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GIUSEPPE CANTORE

DOCENTE A CONTRATTO presso: Dipartimento di Ingegneria "Enzo Ferrari"


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Pubblicazioni

2020 - Compressible Fluid Flow Through Resistances in Series [Articolo su rivista]
Morandi, Gino; Bettocchi, Roberto; Cantore, Giuseppe
abstract

Some theoretical determinations, and with greater generality, experimental research show that, in most cases of practical interest, the law of the flux for a compressible gas, being substantially assimilable to a perfect gas as a function of pressure drop between the extremes of a piping, including concentrated and distributed resistances, can be well approximated by an ellipse. The said ellipse can be determined in different ways, from the flow values for some values of pressure drop through the piping, theoretically or experimentally determined. Practical methods are suggested for determining the ellipse coordinates, which seem to assure simplicity of the advantages of simplicity without detriment to accuracy.


2020 - MOTORI E SISTEMI PROPULSIVI PER AUTOVEICOLI [Monografia/Trattato scientifico]
D'Adamo, A; Cantore, G
abstract

La conoscenza dei motori a combustione interna costituisce una delle principali basi formative che devono caratterizzare la figura dell’Ingegnere Meccanico, in particolar modo dell’Ingegnere del Veicolo. Questo testo si propone di presentarne le principali tipologie e di descriverne i principi di funzionamento, ed è indirizzato a tutti coloro che affrontano per la prima volta, a livello universitario, lo studio di queste macchine complesse. In questa nuova edizione sono state aggiunte alcune sezioni che riflettono l’evoluzione dei motori a combustione interna nell’ultimo decennio, con particolare riferimento alle emissioni inquinanti e al loro trattamento e controllo, così come alle più promettenti frontiere di ricerca sul tema delle combustioni innovative. Inoltre, l’integrazione dei motori a combustione interna in più complessi “sistemi propulsivi” ha motivato la stesura di capitoli riguardanti la descrizione delle più comuni architetture di veicoli ibridi a batteria, corredati da una presentazione dei principi di funzionamento delle pile a combustibile (o “fuel cells”) per uso automobilistico. Si auspica che questo testo possa costituire una solida base di conoscenze, a partire dalle quali lo studente interessato ed appassionato potrà sviluppare i numerosi approfondimenti richiesti dallo studio di questa complessa ed affascinante materia.


2019 - CFD analysis and knock prediction into crevices of piston to liner fireland of an high performance ICE [Relazione in Atti di Convegno]
Rosetti, A.; Iotti, C.; Bedogni, A.; Cantore, G.; Fontanesi, S.; Berni, F.
abstract

The paper aims at defining a methodology for the prediction and understanding of knock tendency in internal combustion engine piston crevices by means of CFD simulations. The motivation for the analysis comes from a real design requirement which appeared during the development of a new high performance SI unit: It is in fact widely known that, in high performance engines (especially the turbocharged ones), the high values of pressure and temperature inside the combustion chamber during the engine cycle may cause knocking phenomena. "Standard" knock can be easily recognized by direct observation of the in-cylinder measured pressure trace; it is then possible to undertake proper actions and implement design and control improvements to prevent it with relatively standard 3D-CFD analyses. Some unusual types of detonation may occur somewhere else in the combustion chamber: Knocking inside piston/liner crevices belongs to the latter category and damages on the piston top land (very similar to pitting) are one of the evidence of knock onset in this region. The very localized regions of damage onset, the cycle to cycle variability and the very short duration of the phenomena do not allow to obtain fully reliable experimental data concerning the investigated problem. A new methodology is therefore implemented in CFD to drive the root causes identification and understanding the impact of crevice design. A preliminary CFD 3D in-cylinder analysis is performed, in order to understand the criticalities in the piston to liner fireland due to local pressure and temperature temporal evolution. Then a "model reduction" is proposed, which is necessary in order to study the problem with reasonable computational costs and times. A 2D simplified model is developed which is able to maintain the possibility to correctly represent the local thermo fluid dynamic effects, especially the auto-ignition conditions. Finally, new geometries are studied in order to prevent local knocking and retard auto-ignition such to improve the KLSA.


2019 - Development of gasoline-ethanol blends laminar flame speed correlations at full-load Si engine conditions via 1D simulations [Relazione in Atti di Convegno]
Pecchia, M. D.; Pessina, V.; Iacovano, C.; Cantore, G.
abstract

Nowadays, most of the engineering development in the field of Spark-Ignited (SI) Internal Combustion Engines (ICEs) is supported by 3D-CFD simulations relying on flamelet combustion models. Such kind of models require laminar flame speed as an input to be specified by the user. While several laminar flame speed correlations are available in literature, for gasoline and pure ethanol at ambient conditions, there is a lack of correlations describing laminar flame speed of gasoline-ethanol blends, for different ethanol volume content, at conditions deemed to be representative of engine-like conditions. Toluene Reference Fuel surrogates with addition of ethanol (ETRF), suitable for representing gasoline-ethanol blends up to 85% vol. ethanol content are formulated. Thanks to these surrogates, 1D premixed laminar flame speed calculations are performed at selected engine-relevant conditions for a E5, E20 and E85 fuels. As a final outcome, three different laminar flame speed correlations based on the chemistry-based calculations are derived for E5, E20 and E85 gasoline-ethanol fuel blends focusing on typical full-load engine conditions. Such kind of correlations can be easily implemented in any 3D-CFD code to provide a chemistry-grounded estimation of laminar flame speed during combustion calculations. Such correlations are of practical use, since they might help in developing the next generation of bio-fuels powered internal combustion engines.


2019 - Intake manifold primary trumpet tuning options for fuel flow limited high Performance I.C.E [Articolo su rivista]
Rosetti, A.; Iott, C.; Cantore, G.
abstract

The 2014 change in Formula One regulations, from naturally aspirated to highly-downsized and heavily-boosted hybridized power units, led to a relevant increase of the internal combustion engine brake specific power output in comparison with former V-8 units. The newly designed “downsized” engines are characterized by a fuel flow limitation and a relevant increase in the thermal loads acting on the engine components, in particular on those facing the combustion chamber. Furthermore, efficiency becomes an equivalent paradigm as performance. In the power unit layout, the air path is defined by the compressor, the intercooler and the piping from the intake plenum to the cylinder. Intake duct length is defined from intake plenum to valve seat and it is a key parameter for engine performance. In order to find the optimum length different design criteria can be applied: the so called “tuning”, the “un-tuning” or the “anti-tuning” are all valid possibilities, showing pros and cons. The scope of the paper is to study and present the possible different tuning options for the internal combustion engine (ICE) part of a hybrid F1 powertrain. From 2015, variable trumpet can be used: the continuous variable length may be used to optimize volumetric efficiency and furthermore to reduce knocking and improve combustion accordingly. The scope of the paper is to show and qualitatively compare all the different options for a hybrid powertrain with fuel flow limited combustion unit.


2019 - Numerical optimization of the injection strategy on a light duty diesel engine operating in dual fuel (CNG/diesel) mode [Articolo su rivista]
Cantore, G.; Mattarelli, E.; Rinaldini, C. A.; Savioli, T.; Scrignoli, Francesco
abstract

The next generation of light duty Diesel engines will face increasingly stringent emissions regulations, as well as the restrictions enforced by some local administrations. As a result, many manufacturers are starting to abandon this technology, because of the high costs and the reduced appeal on customers. On the other hand, Spark Ignition (SI) engines are not able to match the thermal efficiency of diesels, as well as their low emission of carbon dioxide (CO2): therefore, it would be highly desirable to identify cost effective solutions that permit to overcome the limits of Diesel engines, in particular soot emissions, while maintaining all the above-mentioned advantages. Dual fuel combustion, combining Natural Gas and Diesel fuel, is a well-proven technique for reducing soot emissions, while maintaining, or even increasing fuel efficiency. Moreover, this technology can be directly applied to existent Diesel engines with a few hardware modifications. However, to achieve the best results, a brand new calibration of the engine control parameters is needed. CFD-3D combustion simulation is the most cost effective tool to drive the experimental calibration process. Obviously, the numerical models must be previously calibrated against a first set of experimental data.The first part of this study, based on a previous work [9], reviews the building and experimental validation of a CFD 3D model, able to analyze this type of Dual Fuel concept applied to a current production light duty turbocharged Diesel engine, suitable for many different applications. A good agreement between simulation and experiments is found. In the second part of the paper, the calibrated model is used to investigate Dual Fuel combustion, analyzing the effects of Diesel oil injection strategies.


2019 - On the existence of universal wall functions in in-cylinder simulations using a low-Reynolds RANS turbulence model [Relazione in Atti di Convegno]
Berni, F.; Cicalese, G.; Sparacino, S.; Cantore, G.
abstract

Heat Transfer plays a fundamental role in internal combustion engines, as able to affect several aspects, such as efficiency, emissions and reliability. As for this last, a proper heat transfer prediction is mandatory for the estimation of the engine temperatures at peak power condition, it being the most critical one from a thermal point of view. At part-load/low revving speed operations, heat transfer is detrimental for the engine efficiency, deeply reducing indicated work of the burnt gases on the piston. Focusing on the in-cylinder domain, 3D-CFD simulations represent an irreplaceable tool for the estimation of gas-to-wall heat fluxes. Several models have been developed in the past, aiming at providing a reliable estimation of the heat transfer at any condition in terms of load and revving speed. To save computational cost and time, the most diffused wall approach for the numerical simulation of confined reacting flows is the high-Reynolds one, which means that heat transfer model is based on a thermal wall function. Unfortunately, wall functions (logarithmic profiles of the inertial layer) can be claimed only at restricted conditions, such as isothermal steady-state flow, velocity parallel to the wall and negligible pressure gradient. In practice, none of these assumptions is valid for industrial applications such as an in-cylinder simulation. Therefore in these cases, as demonstrated by different works in the past, wall functions do not exist and their adoption leads to a non-negligible error in the estimation of the heat transfer. The main goal of this work is to build up a methodology able to investigate the presence of wall functions in actual industrial applications, in particular in 3D-CFD in-cylinder analyses. Compared to previous works available in literature, where DNS or LES are carried out on simplified geometries and/or at low revving speed conditions because of the computational cost, in the present paper a RANS approach to turbulence and a low-Reynolds wall treatment are adopted. Moreover, a new strategy to obtain dimensionless profiles of velocity and temperature from computed fields is introduced. At first, the proposed methodology is validated on a 2D plane channel. Then, a preliminary application on a research engine, namely the GM Pancake engine, is proposed, showing that dimensionless profiles of velocity and temperature calculated on the combustion chamber walls are remarkably different from standard analytical wall functions.


2019 - Validation of a sectional soot model based on a constant pressure tabulated chemistry approach for PM, PN and PSDF estimation in a GDI research engine [Relazione in Atti di Convegno]
Del Pecchia, M.; Sparacino, S.; Breda, S.; Cantore, G.
abstract

Findings from the International Agency for Research on Cancer (IARC) classified particulate matter (PM) as carcinogenic to humans. While being a promising solution to reduce greenhouse gases (GHG) emissions and increase engine fuel economy, Gasoline Direct Injected (GDI) engines produce a number of particles (PN) of fine size higher than Port Fuel Injected (PFI) ones. As a consequence, the EU commission significantly tightened the emission standards for passenger cars, following which all gasoline engines will have to meet the euro-6d regulation coming into force in 2020. Efforts are made by the research community to understand the root causes leading to soot formation and possibly identify technical solutions to lower it. An important piece of the puzzle is the investigation of soot formation via 3D-CFD. To this aim, relevant efforts have been and are still being paid to adapt soot emissions models, originally developed for Diesel combustion, for GDI units. Among the many available models, one of the most advanced is the so-called Sectional Method. So far, studies presented in literature were not able to formulate a methodology to quantitatively match experimental PM, PN and PSDF without a dedicated soot model tuning. In the present work, a Sectional Method-based methodology to quantitatively predict GDI soot is presented and validated against PM, PN and PSDF measurements on a optically accessible GDI research unit. While adapting the model to GDI soot, attention is devoted to the modelling of soot precursor chemistry: a customized version of a pre-existing chemical kinetics mechanism, used to predict the formation of the key PAH (Polycyclic Aromatic Hydrocarbons) species, is presented and validated via 1D numerical simulations on a premixed flat flame burner dataset available in literature. The present work demonstrates that a Sectional Method-based approach can be a powerful tool to quantitatively predict engine-out soot emissions.


2018 - Analysis and Simulation of Non-Flamelet Turbulent Combustion in a Research Optical Engine [Relazione in Atti di Convegno]
Iacovano, Clara; D'Adamo, Alessandro; Cantore, Giuseppe
abstract

In recent years, the research community devoted many resources to define accurate methodologies to model the real physics behind turbulent combustion. Such effort aims at reducing the need for case-by-case calibration in internal combustion engine simulations. In the present work two of the most widespread combustion models in the engine modelling community are compared, namely ECFM-3Z and G-equation. The interaction of turbulent flows with combustion chemistry is investigated and understood. In particular, the heat release rate characterizing combustion, and therefore the identification of a flame front, is analysed based on flame surface density concept rather than algebraic correlations for turbulent burn rate. In the first part, spark-ignition (S.I.) combustion is simulated in an optically accessible GDI single-cylinder research engine in firing conditions. The turbulent combustion regime is mapped on the Borghi-Peters diagram for all the conditions experienced by the engine flame, and the consistency of the two combustion models is critically analysed. In the second part, a simple test case is defined to test the two combustion models in an ideally turbulence-controlled environment: this allows to fully understand the main differences between the two combustion models under well-monitored conditions. and results are compared against experimental databases of turbulent burn rate for wide ranges of Damkohler (Da) and Karlovitz (Ka) numbers. The joint experimental and numerical study presented in this paper evaluates different approaches within the unified flamelet/non-flamelet framework for modelling turbulent combustion in SI engines. It also indicates guidelines for reduced calibration effort in widespread combustion models.


2018 - Energy efficiency analysis of an entire ceramic kiln: A numerical approach [Articolo su rivista]
Cantore, Giuseppe; Milani, Massimo; Montorsi, Luca; Paltrinieri, Fabrizio
abstract

The paper focuses on the numerical analysis of an industrial ceramic kiln to improve the energy efficiency and the fuel consumption as well as the pollutant emissions. The entire ceramic kiln is modelled by means of a lumped and distributed parameter model; particular care is devoted to the modelling of the heat transfer phenomena occurring within the system under actual operating conditions. Models for the simulation of the different components that are used for the kiln functioning are included in the modelling, such as the burners, the fan, the valves and the control system. The numerical approach demonstrates to predict accurately the temperature distribution of both the tiles and the hot gases along the kiln length. Numerical results are validated against experimental measurements carried out on a real ceramic kiln during regular production operations. The developed numerical approach demonstrates to be an efficient tool for investigating different design solutions for the kiln's components as well as for developing new control strategies. The kiln numerical model is employed to compare different configurations of heat recovery and solutions for improving the tiles' heat transfer. The considered designs are simulated and the performance in terms of energy efficiency and fuel consumption is determined.


2017 - Combustion System Development of an Opposed Piston 2-Stroke Diesel Engine [Relazione in Atti di Convegno]
Mattarelli, Enrico; Cantore, Giuseppe; Rinaldini, Carlo Alberto; Savioli, Tommaso
abstract

Today, the interest towards 2-stroke, opposed-piston compression-ignition engines is higher than ever, after the announcement of imminent production of a 2.7L 3-cylinder light truck engine by Achates Powers. In comparison to other 2-stroke designs, the advantages in terms of scavenge and thermal efficiency are indisputable: a perfect "uniflow" scavenge mode can be achieved with inexpensive and efficient piston controlled ports, while heat losses are strongly reduced by the relatively small transfer area. Unfortunately, the design of the combustion system is completely different from a 4-stroke DI Diesel engine, since the injectors must be installed on the cylinder liners: however, this challenge can be converted into a further opportunity to improve fuel efficiency, adopting advanced combustion concepts. This paper is based on a previous study, where the main geometric parameters of an opposed piston engine rated at 270 kW (3200 rpm) were defined with the support of CFD 1D-3D simulations. The current work will focus on the influence of an innovative combustion system, developed by the authors by means of further CFD-3D analyses, holding constant the boundary conditions of the scavenging process. The numerical study eventually demonstrates that an optimized 2-S OP Diesel engine can achieve a 10% improvement on brake efficiency at full load, in comparison to an equivalent conventional 4-stroke engine, while reducing in-cylinder peak pressures and turbine inlet temperatures.


2017 - Scavenge Ports Ooptimization of a 2-Stroke Opposed Piston Diesel Engine [Relazione in Atti di Convegno]
Mattarelli, Enrico; Rinaldini, Carlo; Savioli, Tommaso; Cantore, Giuseppe; Warey, Alok; Potter, Michael; Gopalakrishnan, Venkatesh; Balestrino, Sandro
abstract

This work reports a CFD study on a 2-stroke (2-S) opposed piston high speed direct injection (HSDI) Diesel engine. The engine main features (bore, stroke, port timings, et cetera) are defined in a previous stage of the project, while the current analysis is focused on the assembly made up of scavenge ports, manifold and cylinder. The first step of the study consists in the construction of a parametric mesh on a simplified geometry. Two geometric parameters and three different operating conditions are considered. A CFD-3D simulation by using a customized version of the KIVA-4 code is performed on a set of 243 different cases, sweeping all the most interesting combinations of geometric parameters and operating conditions. The post-processing of this huge amount of data allow us to define the most effective geometric configuration, named baseline. In the second step of the study, the baseline is further optimized, keeping into account some fundamental design constraints, such as the overall dimensions of the manifold. The evolved geometry is then simulated by using KIVA, adopting a refined grid and realistic boundary conditions. The paper presents the calculated scavenging patterns, offering a detailed insight of the process. Finally, the influence of the offset between the crankshafts is analyzed, by using a calibrated CFD-1D engine model.


2016 - A RANS-Based CFD Model to Predict the Statistical Occurrence of Knock in Spark-Ignition Engines [Articolo su rivista]
D'Adamo, Alessandro; Breda, Sebastiano; Fontanesi, Stefano; Cantore, Giuseppe
abstract

Engine knock is emerging as the main limiting factor for modern spark-ignition (SI) engines, facing increasing thermal loads and seeking demanding efficiency targets. To fulfill these requirements, the engine operating point must be moved as close as possible to the onset of abnormal combustion events. The turbulent regime characterizing in-cylinder flows and SI combustion leads to serious fluctuations between consecutive engine cycles. This forces the engine designer to further distance the target condition from its theoretical optimum, in order to prevent abnormal combustion to severely damage the engine components just because of few individual heavy-knocking cycles. A RANS-based model is presented in this study, which is able to predict not only the ensemble average knock occurrence but also a knock probability. This improves the knock tendency characterization, since the mean knock onset alone is a poorly meaningful indication in a stochastic event such as engine knock. The model is based on a look-up table approach from detailed chemistry, coupled with the transport of the variance of both mixture fraction and enthalpy. These perturbations around the ensemble average value are originated by the turbulent time scale. A multivariate cell-based Gaussian-PDF model is proposed for the unburnt mixture, resulting in a statistical distribution for the in-cell reaction rate. An average knock precursor and its variance are independently calculated and transported, and the earliest knock probability is always preceding the ensemble average knock onset, as confirmed by the experimental evidence. This allows to identify not only the regions where the average knock first occurs, but also where the first knock probability is more likely to be encountered. The application of the model to a RANS simulation of a modern turbocharged direct injection (DI) SI engine is presented and a small percentage of knocking cycles is predicted by the model although the average behavior is knock-free, in agreement with the experiments. The estimate of the knocking probability improves the consolidated “average knock” RANS analysis and gives an indication of the statistical knock tendency of the engine


2016 - Performance, emission and combustion characteristics of a IDI engine running on waste plastic oil [Articolo su rivista]
Rinaldini, Carlo Alberto; Mattarelli, Enrico; Savioli, Tommaso; Cantore, Giuseppe; Garbero, M.; Bologna, A.
abstract

An interesting alternative to fossil fuel for Diesel engines is the use of Diesel-like oil from plastic wastes: such a solution yields the double advantage of recovering the valuable energy content of wastes, as well as of mitigating the disposal problem of the very large amount of plastic wastes produced by both domestic and industrial activities. The present paper describes the experimental campaign carried out on a current production indirect injection, naturally aspirated diesel engine, running on standard Commercial Diesel Oil (CDO) and on a Waste Plastic Oil (WPO) derived from the pyrolysis of plastics. Tests have been carried out at both full and partial load, while in-cylinder pressure traces have been measured in order to analyze the combustion phase. The results of the experimental campaign showed a slight reduction of engine performance for the WPO, basically due to a lower volumetric fuel rating, but better brake specific fuel consumption and brake fuel conversion efficiency (differences up to 8%). In-cylinder pressure traces, measured at the same load, revealed some difference in the first part of the combustion process, in particular at high speeds, where for WPO heat release is smoother. Engine soot emissions are always lower running on WPO, with difference up to 50% at full load.


2015 - A Numerical Investigation on the Potentials of Water Injection as a Fuel Efficiency Enhancer in Highly Downsized GDI Engines [Relazione in Atti di Convegno]
D'Adamo, Alessandro; Berni, Fabio; Breda, Sebastiano; Lugli, Mattia; Fontanesi, Stefano; Cantore, Giuseppe
abstract

Engine downsizing is gaining popularity in the high performance engine market sector, where a new generation of highly downsized engines with specific power outputs around or above 150 HP/litre is emerging. High-boost and downsizing, adopted to increase power density and reduce fuel consumption, have to face the increased risks of pre-ignition, knock or mega-knock. To counterbalance autoignition of fuel/air mixture, such engines usually operate with high fuel enrichments and delayed (sometimes negative) spark advances. The former is responsible for high fuel consumption levels, while the latter reduces performance and induces an even lower A/F ratio (below 11), to limit the turbine inlet temperature, with huge negative effects on BSFC. A relatively simple yet effective solution to increase knock resistance is investigated by means of 3-D CFD analyses in the paper: water is port injected to replace mixture enrichment while preserving, if not improving, indicated mean effective pressure and knock safety margins. Full-load engine operations of a currently made turbocharged GDI engine are investigated comparing the adopted fuel-only rich mixture with stoichiometric mixtures, for which water is added in the intake port under constant charge cooling in the combustion chamber. In order to find the optimum fuel/water balance, preliminary analyses are carried out using a chemical reactor to evaluate the effects of charge dilution and mixture modification on both autoignition delays and laminar flame speeds. Thanks to the lower chemical reactivity of the diluted end gases, the water-injected engine allows the Spark Advance (SA) to be increased; as a consequence, engine power target is met, or even crossed, with a simultaneous relevant reduction of fuel consumption.


2015 - A numerical investigation on the potentials of water injection to increase knock resistance and reduce fuel consumption in highly downsized GDI engines [Relazione in Atti di Convegno]
Berni, Fabio; Breda, Sebastiano; Lugli, Mattia; Cantore, Giuseppe
abstract

3D CFD analyses are used to analyse the effects of port-injection of water in a high performance turbocharged GDI engine. Particularly, water injection is adopted to replace mixture enrichment while preserving, if not improving, indicated mean effective pressure and knock resistance. A full-load / maximum power engine operation of a currently made turbocharged GDI engine is investigated comparing the actual adopted fuel-only rich mixture to stoichiometric-to-lean mixtures, for which water is added in the intake port under constant charge cooling in the combustion chamber. In order to find the optimum fuel/water balance, preliminary analyses are carried out using a chemical reactor to evaluate the effects of charge dilution and mixture modification on both autoignition delays and laminar flame speeds. Thanks to the lower chemical reactivity of the diluted end gases, the water-injected engine allows the spark advance (SA) to be increased; as a consequence, engine power target is met, or even crossed, with a simultaneous relevant reduction of fuel consumption.


2015 - CFD optimization of a 2-stroke range extender engine [Articolo su rivista]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; Cantore, Giuseppe
abstract

A very promising concept for small range extenders (peak power less than 40 kW) is represented by the 2-stroke, direct injection spark ignition engine, with scavenging and exhaust ports controlled by the piston, and an external pump. The most important issue to be addressed on this type of engines is the compliance with stringent rules on pollutant emissions, which depends on combustion patterns and the quality of the scavenging process. The latter is generally hindered by the symmetry of ports timings, but this handicap can be canceled by adopting a patented rotary valve, controlling the flow through a set of auxiliary transfer ports, and using a piston pump for delivering air to the power cylinder and enhancing the balance of the crankshaft. The paper reviews the design of a virtual engine, rated at 35 kW at 5600 rpm, and developed according to the above mentioned concepts. Design has been driven by CFD simulation, using, whenever possible, experimentally calibrated numerical models, or experimental information derived from similar projects. Particular care has been devoted to characterize the scavenging process and the flow patterns within the cylinder and through the ports, analyzing the influence of the rotary induction valve. Engine performance parameters have been predicted by using a well-established commercial software (GT-Power, by Gamma Technologies), while CFD-3D analyses have been carried out by means of a customized version of the KIVA-3V code. The whole study is conceived as the basis for the construction of a physical prototype. The power target has been virtually achieved with a very light and compact engine (estimated weight without the close-coupled electric motor: 35 kg). A three-way catalyst allows the engine to comply with the most stringent emission regulations, without relevant penalizations on fuel efficiency. Furthermore, the engine can work with lean mixtures, achieving a minimum specific fuel consumption comparable to a current automotive Diesel engine (223 g/kWh). This excellent result is due to the low friction and pumping losses of the 2-Stroke engine, as well as to the compactness of the combustion chamber and the capability to stratify the charge.


2015 - Comparison between 2 and 4-stroke engines for a 30 kW range extender [Articolo su rivista]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; Cantore, Giuseppe; Agostinelli, Enrico
abstract

The paper compares two different design concepts for a range extender engine rated at 30 kW at 4500 rpm. The first project is a conventional 4-Stroke SI engine, 2-cylinder, 2-valve, equipped with port fuel injection. The second is a new type of 2-Stroke loop scavenged SI engine, featuring a direct gasoline injection and a patented rotary valve for enhancing the induction and scavenging processes. Both power units have been virtually designed with the help of CFD simulation. Moreover, for the 2-Stroke engine, a prototype has been also built and tested at the dynamometer bench, allowing the authors to make a reliable theoretical comparison with the well assessed 4-Stroke unit. Even if the optimized design of each one of the two engines is similar to that of existing prototypes, the paper is not intended to be a benchmarking, but a general study, aimed to define the fundamental project guidelines and compare different solutions under the same conditions, including the unavoidable arbitrary hypotheses. The main results of the comparison may be summarized as follows: the 2-Stroke engine is more compact and light (â?38% of frontal area, 35 vs. 50 kg); its fuel efficiency is slightly better, and further improvements are possible running on stratified charge; the reduction of NOx in the 2-S catalyst may not be complete, due to the unavoidable air short-circuit.


2015 - Effects of fuel composition on charge preparation, combustion and knock tendency in a high performance GDI engine. Part I: RANS analysis [Relazione in Atti di Convegno]
Giovannoni, Nicola; D'Adamo, Alessandro; Nardi, Luca; Cantore, Giuseppe
abstract

The paper analyses the effects of fuel composition modelling in a turbocharged GDI engine for sport car applications. Particularly, a traditional single-component gasoline-surrogate fuel is compared to a seven-component fuel model available in the open literature. The multi-component fuel is represented using the Discrete-Continuous-Multi-Component modelling approach, and it is specifically designed in order to match the volatility of an actual RON95 European gasoline. The comparison is carried out following a detailed calibration with available experimental measurements for a full load maximum power engine speed operation of the engine, and differences are analyzed and critically discussed for each of the spray evolution, mixture stratification and combustion. In the present paper (Part I), a RANS approach is used to preliminarily investigate the behaviour of the fuel model on the average engine cycle. In the subsequent Part II of the same paper, the numerical framework is evolved into a more refined LES approach, in order to take into account cycle-to-cycle variations in mixture formation and knock tendency.


2015 - Effects of fuel composition on charge preparation, combustion and knock tendency in a high performance GDI engine. Part II: Les analysis [Relazione in Atti di Convegno]
D'Adamo, Alessandro; Giovannoni, Nicola; Nardi, Luca; Cantore, Giuseppe; D'Angelis, Angelo
abstract

As discussed in the Part I of this paper, a numerical activity is carried out in order to analyse the effects of fuel composition modelling in a turbocharged GDI engine for sport car applications. While Part I analyses the "ensemble averaged" macroscopic effects on spray evolution, mixture stratification, combustion and knock tendency, in Part II of this paper cycle-to-cycle variations are analysed and discussed using a multi-cycle LES numerical framework, again comparing results from a more traditional single-component fuel surrogate model to those of a multi-component one. A purposely developed numerical approach is applied to properly account for the effects of the Discrete-Continuous-Multi-Component fuel formulation on the charge preparation: just before the spark timing, each vaporized fuel fraction is lumped back into a single-component surrogate fuel to allow the combustion model (ECFM-3Z, in its LES formulation) to take place. At the beginning of a new injection process, the numerical framework for the injected spray is switched back to Multi-Component, thus allowing each fuel fraction to independently spread, vaporize and diffuse in the combustion chamber according to the cycle-specific characteristics. A detailed comparison between the two fuel formulations is carried out on both average and rms values of the most influencing fields just before the spark discharge.


2015 - Effects of Fuel-Induced Piston-Cooling and Fuel Formulation on the Formation of Fuel Deposits and Mixture Stratification in a GDI Engine [Relazione in Atti di Convegno]
Giovannoni, Nicola; D'Adamo, Alessandro; Cicalese, Giuseppe; Cantore, Giuseppe
abstract

Fuel deposits in DISI engines promote unburnt hydrocarbon and soot formation: due to the increasingly stringent emission regulations (EU6 and forthcoming), it is necessary to deeply analyze and well-understand the complex physical mechanisms promoting fuel deposit formation. The task is not trivial, due to the coexistence of mutually interacting factors, such as complex moving geometries, influencing both impact angle and velocity, and time-dependent wall temperatures. The experimental characterization of actual engine conditions on transparent combustion chambers is limited to highly specialized research laboratories; therefore, 3D-CFD simulations can be a fundamental tool to investigate and understand the complex interplay of all the mentioned factors. The aim is pursued in this study by means of full-cycle simulations accounting for instantaneous fuel/piston thermal interaction and actual fuel characteristics. To overcome the standard practice, based on the adoption of time-independent wall temperatures, solid cell layers are added onto the piston crown. In particular, thermal boundary conditions on the lower face of the piston portion are derived from a complete CHT simulation, thus considering both the actual piston shape and the point-wise cooling effect by the oil jets, the friction contribution and the heat transfer to the cylinder liner and the connecting rod. Furthermore, the use of a simplified fuel model based on a single-component formulation is compared to a more realistic hydrocarbon blend. The methodology is applied to a currently produced turbocharged DISI engine operating at full load peak power and maximum torque regimes; the piston thermal field is completely resolved in space and time during the engine cycle, and its effects on spray guidance, fuel impingement and liquid film formation are carefully analyzed.


2015 - Effects on knock intensity and specific fuel consumption of port water/methanol injection in a turbocharged GDI engine: Comparative analysis [Relazione in Atti di Convegno]
Breda, Sebastiano; Berni, Fabio; D'Adamo, Alessandro; Testa, Francesco; Severi, Elena; Cantore, Giuseppe
abstract

The recent rise in fuel prices, the need both to reduce ground transport-generated emissions (increasingly constrained by legislation) and to improve urban air quality have brought fuel-efficient, low-emissions powertrain technologies at the top of vehicle manufacturers' and policy makers' agenda. To these aims, engine design is now oriented towards the adoption of the so-called downsizing and down-speeding techniques, while preserving the performance target. Therefore, brake mean effective pressure is markedly increasing, leading to increased risks of knock onset and abnormal combustions in last-generation SI engines. To counterbalance the increased risks of pre-ignition, knock or mega-knock, currently made turbocharged SI engines usually operate with high fuel enrichments and delayed (sometimes negative) spark advances. The former is responsible for high fuel consumption levels, while the latter induce an even lower A/F ratio (below 11), to limit the turbine inlet temperature, with huge negative effects on BSFC. Possible solutions to increase knock resistance are investigated in the paper by means of 3D-CFD analyses: water, water/methanol emulsion and methanol are port-fuel injected to replace mixture enrichment while preserving, if not improving, indicated mean effective pressure and knock safety margins. The aim of the work is therefore the replacement of the gasoline-only rich mixture with a global stoichiometric one while avoiding power loss and improving fuel consumption. In order to maintain the same knock tendency, water, methanol or a mixture of the two is then added in the intake port to keep the same charge cooling of the original rich mixture. Different strategies in terms of methanol/water ratios of the port injected mixture are compared in order to find the best trade-off between fuel consumption, performance and knock tendency.


2015 - Large-eddy simulation of cycle-resolved knock in a turbocharged SI engine [Relazione in Atti di Convegno]
D'Adamo, Alessandro; Breda, Sebastiano; Cantore, Giuseppe
abstract

The paper presents a numerical study of cycle-to-cycle variability in a turbocharged GDI engine. The Large-Eddy Simulation technique is adopted in this study in conjunction with the recent ISSIM-LES model for spark-ignition, allowing a dedicated treatment of both the flame kernel formation and flame development phases. Numerical results are compared with an extended dataset of experimental test-bed acquisitions, where the engine is operated at knock-limited spark advance. The agreement of both ensemble averaged combustion pressure history and of its standard deviation confirm the validity of the adopted numerical framework able to correctly quantify the degree of CCV measured by the experiments. Knock tendency is evaluated by means of an in-house developed knock model, based on a tabulation technique for AI delays of the same RON98 gasoline as the one used in experiments. The results confirm the knock-free condition of the experimental KLSA, for which the cycle-resolved knock signature is extremely weak just for the cycles in the highest band of the CCV-affected combustion. The visualization of the pressure wave allows to identify the exhaust side as the most knock-prone region. Finally, spark-advance is increased by 3 CA with respect to the experimental edge-of knock limit, in order to simulate an experimentally prevented operating condition. Local pressure measurements mimicking flush-mounted transducers confirm the severe knock damage related to this condition. The predictive capability of the combustion CCV and of the adopted knock model confirm the heavy and recurrent cycle-resolved knock damage.


2015 - LES Modelling of Spark-Ignition Cycle-to-Cycle Variability on a Highly Downsized DISI Engine [Articolo su rivista]
d'ADAMO, Alessandro; Breda, Sebastiano; Fontanesi, Stefano; Cantore, Giuseppe
abstract

The paper reports an activity aiming at characterizing cycle-to-cycle variability (CCV) of the spark-ignition (SI) process in a high performance engine. The numerical simulation of spark-ignition and of early flame kernel evolution are major challenges, mainly due to the time scales of the spark discharge process and to the reduced spatial scales of flame kernel. Typical mesh resolutions are insufficient to resolve the process and a dedicated treatment has to be provided at a subgrid level if the ignition process is to be properly modelled. The focus of this work is on the recent ISSIM-LES (Imposed Stretch Spark-Ignition Model) ignition model, which is based on an extension of the flame surface density (FSD) transport equation for a dedicated flame kernel treatment at subgrid scales. The FSD equation is solved immediately after spark discharge. The interaction of the flame kernel with the flow field is fully accounted for since spark formation and a transition is provided from ignition to propagation phase. The comparison is carried out with the AKTIM-Euler ignition model in terms of flame interaction with the flow field (e.g. arc convection, flame blow-off, flame holder effect). A multiple cycle LES activity provided a set of cycle-resolved conditions for spark-ignition comparisons, and the flame kernel development is carefully analyzed for the two ignition models on a wide range of thermo-physical conditions. Spark-ignition cyclic variability and combustion traces are compared with experiments. Results confirm that the simulated cycle-to-cycle variability increases through the adoption of the ISSIM-LES ignition model.


2015 - Numerical Investigation on the Effects of Water/Methanol Injection as Knock Suppressor to Increase the Fuel Efficiency of a Highly Downsized GDI Engine [Relazione in Atti di Convegno]
Berni, Fabio; Breda, Sebastiano; D'Adamo, Alessandro; Fontanesi, Stefano; Cantore, Giuseppe
abstract

A new generation of highly downsized SI engines with specific power output around or above 150 HP/liter is emerging in the sport car market sector. Technologies such as high-boosting, direct injection and downsizing are adopted to increase power density and reduce fuel consumption. To counterbalance the increased risks of pre-ignition, knock or mega-knock, currently made turbocharged SI engines usually operate with high fuel enrichments and delayed (sometimes negative) spark advances. The former is responsible for high fuel consumption levels, while the latter induce an even lower A/F ratio (below 11), to limit the turbine inlet temperature, with huge negative effects on BSFC. A possible solution to increase knock resistance is investigated in the paper by means of 3D-CFD analyses: water/methanol emulsion is port-fuel injected to replace mixture enrichment while preserving, if not improving, indicated mean effective pressure and knock safety margins. The peak power engine operation of a currently made turbocharged GDI engine is investigated comparing the adopted fuel-only rich mixture with stoichiometric-to-lean mixtures, for which water/methanol mixture is added in the intake port under constant charge cooling in the combustion chamber and same air consumption level. In order to find the optimum fuel/emulsion balance analytic considerations are carried out. Different strategies are evaluated in terms of percentage of methanol-water emulsion rate, to assess the effects of different charge dilutions and mixture compositions on knock tendency and combustion efficiency. Thanks to the lower chemical reactivity of the diluted end gases and the faster burn rate allowed by the methanol addition, the water/methanol-injected engine allows the spark advance (SA) to be increased; as a consequence, engine power target is met, or even crossed, with a simultaneous relevant reduction of fuel consumption.


2014 - A Methodology to Improve Knock Tendency Prediction in High Performance Engines [Relazione in Atti di Convegno]
Fontanesi, Stefano; Cicalese, Giuseppe; D'Adamo, Alessandro; Cantore, Giuseppe
abstract

The paper presents a comprehensive numerical methodology for the estimation of knock tendency in SI engines, based on the synergic use of different frameworks [1]. 3D-CFD in-cylinder analyses are used to simulate the combustion and to estimate the point-wise heat flux acting on engine components. The resulting heat fluxes are used in a conjugate heat transfer model in order to reconstruct the actual point-wise wall temperature distribution. An iterative loop is established between the two simulation realms. In order to evaluate the effect of temperature on knock, in-cylinder analyses are integrated with an accurate chemical description of the actual fuel.


2014 - A new design concept for 2-Stroke aircraft Diesel engines [Relazione in Atti di Convegno]
Cantore, Giuseppe; Mattarelli, Enrico; Rinaldini, Carlo Alberto
abstract

High power density, low weight, compact dimensions, high efficiency as well as reliability are the key factors in designing and dimensioning piston engines for General Aviation and Unmanned Aerial Vehicle (UAV) power plants. Despite of new available technologies, conventional solutions are still struggling to fulfill simultaneously all those requirements. The paper explores the application of a new design of 2-Stroke externally scavenged engines to aircraft. The new concept basically consists in the use of a patented rotary valve for controlling the flow through a set of inlet ports, enabling supercharging and the achievement of extremely high power densities compared to conventional solutions. The scavenging is realized by using an external pump, made up of a further cylinder, whose piston is connected to the same crankshaft. The piston pump allows the crankcase to be used as a conventional oil sump, and greatly improves the crankshaft balance. No poppet valves or camshafts need to be installed, since the flow is driven by piston-controlled ports and by two sets of reed valves. The engine can adopt two types of combustion system: Gasoline Direct Injection (GDI) for SI operations, and Direct Injection Common Rail for Diesel cycle. The paper is focused on the last version, since it can run on standard aircraft fuel. The Diesel engine has three cylinders and three piston pumps, for a total displacement of 1.5 liter The engine is turbocharged and inter-cooled, in order to reach a power target, at sea level, of 150 kW@4000 rpm. Another fundamental target is the minimum power of 100 kW, at the altitude of 20,000 feet. The paper reviews the design of the engine and presents the numerical prediction of the key performance parameters.


2014 - CFD Analysis of the Acoustic Behavior of a Centrifugal Compressor for High Performance Engine Application [Relazione in Atti di Convegno]
Fontanesi, Stefano; Paltrinieri, Stefano; Cantore, Giuseppe
abstract

The paper reports an activity aiming at the characterization of the acoustic noise of a centrifugal compressor for a currently made high performance engine. All the analyses are carried out through the use of Detached Eddy Simulation. During high-load / low-ngine speed operations of the engine, the compressor exhibits noise peaks above 150 dBA at relatively low frequencies, whose origin is relatively hard to rationalize. The use of three-dimensional CFD simulation appears to be very promising to gain a better understanding of the complex flow structures at the compressor inlet as well as to promote design optimizations aiming at limiting the acoustic emissivity of the component. In view of the dependency of the acoustic phenomena on the instantaneous pressure waves and flow structures, fully transient CFD simulations are highly recommended, together with the use of sophisticated numerical techniques such as Large Eddy and Detached Eddy simulation [1], [2], which are widely recognized to be able to better capture highly unstable features than the common RANS approach [3], [4]. In order to limit the computational cost of the analyses, preliminary steady-state RANS simulations are carried out to both initialize the flow field and to evaluate the grid capability to properly match the desired frequency spectrum.


2014 - Development of a Multi-component based Methodology for the Simulation of Reacting High Injection Pressure Diesel Sprays [Relazione in Atti di Convegno]
Malaguti, Simone; Giuseppe, Bagli; Stefano, Piccinini; Cantore, Giuseppe
abstract

Modern Diesel engines are attractive for fuel economy and performances but they are suffering from increasingly strict emission standards. Therefore the investigation of the injection and combustion processes are mandatory. This paper focuses on the development of a multi-component fuel based methodology for the simulation of non-reacting and reacting high injection pressure Diesel sprays. In multi-dimensional modeling fuels are represented predominantly by single components, such as n-Dodecane for Diesel, and this is a limitation in their ability to represent real fuels which are blends of hundreds components. This study outlines a method by which the fuel composition is represented by means of a Discrete Multi-Component (DMC) model approach in order to improve the prediction of the vaporization behavior of high injection pressure Diesel sprays. A testing blend of 6 hydrocarbons is taken into account and a reduced one is developed in order to reduce the computational cost of the CFD simulations while maintaining the advantages due to a multi-component description of the mixture. The CFD methodology is developed within Star-CD commercial code while particular care is also dedicated to the prediction of the atomization and secondary breakup processes. At the nozzle exit the atomized droplets are predicted by a primary breakup approach which is able to take into account the cavitation phenomena and the turbulent effects. The atomization model is based on a simplified approach that is able to evaluate the effects of the nozzle geometry. The preliminary investigations are performed in a constant volume vessel, validating the numerical parameters against experimental data in order to correctly reproduce spray vaporization behavior. Then, to illustrate the important differences between the vaporization characteristics of a multi-component mixture compared to a mono-component one, the CFD methodology is tested investigating the in-cylinder combustion process of a 4 cylinders, Common Rail Diesel engine of current production.


2014 - Integrated In-Cylinder/CHT Analysis for the Prediction of Abnormal Combustion Occurrence in Gasoline Engines [Relazione in Atti di Convegno]
Fontanesi, Stefano; Cicalese, Giuseppe; Cantore, Giuseppe; D'Adamo, Alessandro
abstract

In order to improve fuel conversion efficiency, currently made spark-ignited engines are characterized by the adoption of gasoline direct injection, supercharging and/or turbocharging, complex variable valve actuation strategies. The resulting increase in power/size ratios is responsible for substantially higher average thermal loads on the engine components, which in turn result in increased risks of both thermo-mechanical failures and abnormal combustion events such as surface ignition or knock. The paper presents a comprehensive numerical methodology for the accurate estimation of knock tendency of SI engines, based on the integration of different modeling frameworks and tools. Full-cycle in-cylinder analyses are used to estimate the point-wise heat flux acting on the engine components facing the combustion chamber. The resulting cycle-averaged heat fluxes are then used in a conjugate heat transfer model of the whole engine in order to reconstruct the actual point-wise temperature distribution of the combustion chamber walls. The two simulation realms iteratively exchange information until convergence is met. Particularly, the effect of point-wise temperature distribution on the onset of abnormal combustion events is evaluated. In-cylinder analyses account for the actual autoignition behavior of the air/fuel mixture through a look-up table approach: the combustion chamber is treated as a two-zone region (burnt/unburnt), where ignition delay tabulation, generated off-line using a constant pressure reactor, is applied to the unburnt region to estimate cell-wise knock proximity. The methodology is applied to a high performance engine and the importance of an accurate representation of the combustion chamber thermal boundary conditions when aiming at precisely evaluating the surface ignition/knock tendency is highlighted.


2014 - LES Analysis of Cyclic Variability in a GDI Engine [Relazione in Atti di Convegno]
Fontanesi, Stefano; Paltrinieri, Stefano; Cantore, Giuseppe
abstract

The paper critically discusses Large-Eddy Simulation (LES) potential to investigate cycle-to-cycle variability (CCV) in internal combustion engines. Particularly, the full load/peak power engine speed operation of a high-performance turbocharged GDI unit, for which ample cycle-to-cycle fluctuations were observed during experimental investigations at the engine test bed, is analyzed through a multi-cycle approach covering 25 subsequent engine cycles. In order to assess the applicability of LES within the research and development industrial practice, a modeling framework with a limited impact on the computational cost of the simulations is set up, with particular reference to the extent of the computational domain, the computational grid size, the choice of boundary conditions and numerical sub-models [1, 2, 3]. In order to evaluate the applicability of the adopted approach to the resolution of an adequate portion of the overall turbulent energy spectrum, different grid metrics are at first introduced, based on criteria available in literature [4, 5]. A qualitative comparison between CFD results and experimental evidence is then carried out in terms of both in-cylinder pressure envelope and coefficients of variation for any of indicated mean effective pressure, 10%, 50% and 90% of fuel burnt distributions among the investigated cycles. Particularly, a detailed analysis of the physical factors influencing the exhibited cycle-to-cycle variability is performed through the use of correlation coefficients, aiming at highlighting possible hierarchies between the many involved phenomena and the observed engine behavior. Finally, a phase-dependent Proper Orthogonal Decomposition (POD). Particularly, while POD applications available in literature mainly cover vector fields and flow structures [6, 7], in the present paper the analysis is extended to scalar fields describing the combustion process evolution and its cyclic variability, and results are critically analyzed and commented.


2013 - Advances in The Design of Two-Stroke, High Speed, Compression Ignition EnginesAdvances in Internal Combustion Engines and Fuel Technologies [Capitolo/Saggio]
Mattarelli, Enrico; Cantore, Giuseppe; Rinaldini, Carlo Alberto
abstract

The most difficult challenge for modern 4-Stroke high speed Diesel engines is the limitation of pollutant emissions without penalizing performance, overall dimensions and production costs, the last ones being already higher than those of the correspondent S.I. engines. An interesting concept in order to meet the conflicting requirements mentioned above is the 2-Stroke cycle combined to Compression Ignition. Such a concept is widely applied to large bore engines, on steady or naval power-plants, where the advantages versus the 4-Stroke cycle in terms of power density and fuel conversion efficiency (in some cases higher than 50% [1]) are well known. In fact, the double cycle frequency allows the designer to either downsize (i.e. reduce the displacement, for a given power target) or “down-speed” (i.e. reduce engine speed, for a given power target) the 2-stroke engine. Furthermore, mechanical efficiency can be strongly improved, for 2 reasons: i) the gas exchange process can be completed with piston controlled ports, without the losses associated to a valve-train; ii) the mechanical power lost in one cycle is about halved, in comparison to a 4-Stroke engine of same design and size, while the indicated power can be the same: as a result, the weight of mechanical losses is lower.


2013 - Assessment of the Potential of Proper Orthogonal Decomposition for the Analysis of Combustion CCV and Knock Tendency in a High Performance Engine [Relazione in Atti di Convegno]
Fontanesi, Stefano; D'Adamo, Alessandro; Paltrinieri, Stefano; Cantore, Giuseppe; C. J., Rutland
abstract

The paper reports the application of Proper Orthogonal Decomposition (POD) to LES calculations for the analysis of combustion and knock tendency in a highly downsized turbocharged GDI engine that is currently under production. In order to qualitatively match the cyclic variability of the combustion process, Large-Eddy Simulation (LES) of the closed-valve portion of the cycle is used with cycle-dependent initial conditions from a previous multi-cycle analysis [1, 2, 3]. Detailed chemical modelling of fuel’s auto-ignition quality is considered through an ad-hoc implemented look-up table approach, as a trade-off between the need for a reasonable representation of the chemistry and that of limiting the computational cost of the LES simulations. Experimental tests were conducted operating the engine at knock-limited spark advance (KLSA) and the proposed knock model was previously validated for such engine setup [3]. All the presented calculations are carried out for an increased spark advance (SA) to both promote knock onset over a large set of cases and to assess the modelling framework sensitivity to small variations in engine operations. The analysis of combustion development and knock onset is carried out analysing 20 subsequent engine cycles through POD of both flame front evolution and local autoignition locations. Particularly, phase-dependent three-dimensional POD is implemented over the scalar distributions of progress variable of the chemical reactions and auto-ignition location, estimated based on the work by Lafossas et al. [4]. The method of snapshots introduced by Sirovich is used for POD [5]. The proposed POD analysis is critically discussed in terms of physical soundness, capability to investigate the engine knock-characteristics and applicability to the optimization of the combustion chamber.


2013 - Comparison between a Diesel and a New 2-Stroke GDI Engine on a Series Hybrid Passenger Car [Relazione in Atti di Convegno]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; Cantore, Giuseppe
abstract

The internal combustion engine (ICE) for a series hybrid vehicle must be very compact, fuel efficient reliable and clean; furthermore it should possess excellent NVH features; finally, the cost should be as low as possible. An unconventional but not exotic solution, potentially ideal to fulfill all the above mentioned requirements, is represented by a 2-Stroke externally scavenged GDI engine, without poppet valves. BRC (Cherasco, Italy) and PRIMAVIS (Turin, Italy) are currently developing an engine of this type, incorporating a patented rotary valve for the control of the charge induced to cylinder. The development is supported by extensive CFD simulations, which are able to predict all the main engine performance characteristics. The paper analyzes, from a theoretical point of view, the installation of the engine on an electric vehicle, previously optimized for a small Diesel engine (Smart 0.8 l CDi). For a straight comparison between the Diesel and the 2-Stroke GDI engine, all the vehicle components are the same. Furthermore, the operating points employed for battery charging correspond to the same values of brake power. The 4-S Diesel and the 2-S GDI engine are compared from several point of views: fuel economy in the European driving cycle, capability to comply with stringent emissions regulations, cost, overall dimensions, weight, etc. It is found that the new 2-Stroke engine can possess the advantages of the Diesel in terms of fuel efficiency, while maintaining the compactness and cost effectiveness of the best SI Range Extenders. INTRODUCTION


2013 - Knock Tendency Prediction in a High Performance Engine Using LES and Tabulated Chemistry [Articolo su rivista]
Fontanesi, Stefano; Paltrinieri, Stefano; d'ADAMO, Alessandro; Cantore, Giuseppe; C. J., Rutland
abstract

The paper reports the application of a look-up table approach within a LES combustion modelling framework for the prediction of knock limit in a highly downsized turbocharged DISI engine. During experimental investigations at the engine test bed, high cycle-to-cycle variability was detected even for relatively stable peak power / full load operations of the engine, where knock onset severely limited the overall engine performance. In order to overcome the excessive computational cost of a direct chemical solution within a LES framework, the use of look-up tables for auto-ignition modelling perfectly fits with the strict mesh requirements of a LES simulation, with an acceptable approximation of the actual chemical kinetics. The model here presented is a totally stand-alone tool for autoignition analysis integrated with look-up table reading from detailed chemical kinetic schemes for gasoline. The look-up table access is provided by a multi-linear interpolating routine internally developed at the “Gruppo Motori (GruMo)” of the University of Modena and Reggio Emilia. As the experimental tests were conducted operating the engine at knock-limited spark advance, the tool is at first validated for three different LES cycles in terms of knock tolerance, i.e. the safety margin to knock occurrence. As a second stage, the validation of the methodology is performed for discrete spark advance increases in order to assess the sensitivity of the modelling strategy to variations in engine operations. A detailed analysis of the unburnt gas physical state is performed which confirms the knock-limited condition suggested by the experimental tests.


2013 - Modelling of primary breakup process of a multi-hole spray for Gasoline Direct Engine applications [Articolo su rivista]
Malaguti, Simone; Fontanesi, Stefano; Cantore, Giuseppe; A., Montanaro; L., Allocca
abstract

The paper proposes a numerical methodology for the simulation of a gasoline spray generated by a multi-hole injector of a current production wall-guided Gasoline Direct Injection engine. Particular care is dedicated to the accurate representation of the spray primary breakup by means of an atomization model. The model is purposely implemented to take into account cavitation phenomena and turbulent effects induced by the nozzle geometry through a simplified approach. Since a high primary breakup rate is expected, an initial distribution of atomized droplets is predicted at the nozzle hole exit by the numerical approach. The spray is at first experimentally investigated in a test vessel at non-evaporative ambient conditions and under quiescent conditions, injecting commercial gasoline at two different injection pressures (10.0 and 20.0 MPa). The spray is characterised in terms of both instantaneous mass flow rate and morphology. Numerical simulations are performed and then compared against experiments in order to evaluate their capability to correctly predict liquid spray penetration, droplet size distribution and spray morphology. The new approach is a fairly simple yet reliable solution able to predict the influence of the nozzle hole (in terms of discharge coefficient, diameter and length) and neglecting geometrical details usually far from being easily accessed by engine developers.


2012 - Analisi sperimentale e numerica di un sistema di iniezione ad attuazione diretta per motori Diesel [Relazione in Atti di Convegno]
Postrioti, Lucio; Malaguti, Simone; Cantore, Giuseppe; Bosi, Maurizio; Buitoni, Giacomo; Piccinini, Stefano
abstract

Nel presente lavoro si riportano i risultati di un’analisi sperimentale e numerica del comportamento idraulico e dell’evoluzione degli spray di un innovativo sistema di iniezione ad attuazione diretta per motori Diesel light duty. Il sistema d’iniezione analizzato - Magneti Marelli Diesel Direct Injection, DDI - è basato sull’attuazione diretta dello spillo iniettore mediante solenoide. Il sistema DDI opera con pressioni di iniezione fino a 600 bar, con un polverizzatore multi-foro che consente di ottenere una distribuzione di getti di combustibile in camera di combustione adatta per applicazioni Diesel industriali ed automotive di piccola cilindrata. Nella fase attuale della ricerca, i cui risultati sono riportati nel presente lavoro, il comportamento idraulico del sistema DDI in termini di volume iniettato e di portata istantanea è stato analizzato in diverse condizioni di funzionamento. L’evoluzione degli spray risultante in queste condizioni è stata inoltre analizzata in condizioni di camera quiescente mediante tecniche di visualizzazione per determinare le principali caratteristiche geometriche del getto. Il successivo confronto con le simulazioni computazionali è il punto di partenza per lo sviluppo di una metodologia che, mediante l'integrazione di codici di calcolo 1D e 3D, sia in grado di descrivere l'evoluzione dello spray e la sua interazione con la carica presente all’interno della camera di combustione. In questa fase del lavoro si è valutato il comportamento dei principali modelli CFD utilizzati per la simulazione dello spray di combustibile con approccio lagrangiano, in condizioni di pressione di iniezione non convenzionali per applicazioni Diesel. Si riportano quindi i confronti sperimentali-numerici con i principali risultati conseguiti nel corso di un campagna di validazione dei modelli di atomizzazione, valutando anche gli effetti di alcuni parametri, quali la dimensione media della cella computazionale, sull'evoluzione dello spray.


2012 - Development of reduced and optimized reaction mechanisms based on genetic algorithms and element flux analysis [Articolo su rivista]
Cantore, Giuseppe; Perini, Federico; J. L., Brakora; R. D., Reitz
abstract

The present paper introduces an approach for the automatic development of reducedreactionmechanisms for hydrocarbon combustion. An iterative reduction procedure is adopted with the aim of gradually reducing the number of species involved in the mechanism, while still maintaining its predictiveness in terms of not only ignition delay times, but also the time evolution of important species. In particular, a global error function is defined taking into account a set of 18 ignition delay calculations at different, engine-relevant, initial mixture compositions, temperatures and pressures. The choice of the species to be deleted is performed exploiting the elementfluxanalysis method, first introduced by Revel et al.; when a global error function of the reducedmechanism exceeds the required accuracy, the collision frequencies and activation energies of selected reactions are corrected by means of a GA-based code. The procedure is repeated until the lowest number of species at the required global error tolerance is achieved. The methodology is applied to a detailed mechanism of ethanol combustion consisting of 58 species and 383 reactions to produce an optimal reducedmechanism of 33 species and 155 reactions.


2012 - Experimental and Numerical Investigation of the Idle Operating Engine Condition for a GDI Engine [Relazione in Atti di Convegno]
Malaguti, Simone; d'ADAMO, Alessandro; Cantore, Giuseppe; P., Sementa; B. M., Vaglieco
abstract

The increased limitations to both NOx and soot emissions have pushed engine researchers to rediscover gasoline engines. Among the many technologies and strategies, gasoline direct injection plays a key-role for improving fuel economy and engine performance. The paper aims to investigate an extremely complex task such as the idle operating engine condition when the engine runs at very low engine speeds and low engine loads and during the warm-up. Due to the low injection pressure and to the null contribution of the turbocharger, the engine condition is far from the standard points of investigation. Taking into account the warm-up engine condition, the analyses are performed with a temperature of the coolant of 50°C. The paper reports part of a combined numerical and experimental synergic activity aiming at the understanding of the physics of spray/wall interaction within the combustion chamber and particular care is used for air/fuel mixing and the combustion process analyses. In order to properly describe the engine condition, different injection strategies are investigated. Late and early injection strategies are deeply analyzed and compared in terms of combustion stability and pollutant emissions. UV-visible imaging and spectral measurements are carried out in real engine with wide optical accesses… Measurements are performed in the optically accessible combustion chamber realized by modifying a real engine. The cylinder head was modified in order to allow in the fourth cylinder the visualization of the fuel injection and the combustion process with high spatial and temporal resolution. The 3D-CFD engine simulations are reproduced by means the commercial code Star-CD. Due to the warm-up condition and the many physical sub-models a numerical methodology is implemented and particular care is used to boundaries conditions analyses. CFD analysis is used to find a possible explanation of the high cycle to cycle variability. The experimental and numerical comparisons, in terms fuel mixing and front flame propagation, give an explanation of the idle condition.


2012 - Validation of a Sparse Analytical Jacobian Chemistry Solver for Heavy-Duty Diesel Engine Simulations with Comprehensive Reaction Mechanisms [Relazione in Atti di Convegno]
Perini, Federico; Galligani, Emanuele; Cantore, Giuseppe; R., Reitz
abstract

The paper presents the development of a novel approach to the solution of detailed chemistry in internal combustion engine simulations, which relies on the analytical computation of the ordinary differential equations (ODE) system Jacobian matrix in sparse form. Arbitrary reaction behaviors in either Arrhenius, third-body or fall-off formulations can be considered, and thermodynamic gasphase mixture properties are evaluated according to the wellestablished 7-coefficient JANAF polynomial form. The current work presents a full validation of the new chemistry solver when coupled to the KIVA-4 code, through modeling of a single cylinder Caterpillar 3401 heavy-duty engine, running in two-stage combustion mode. The code has been tested on a wide range of simulations, at different injection timings, intake pressures, and EGR mass fractions, and considering two reaction mechanisms: a skeletal one with 29 species and 52 reactions, and a comprehensive, semi-detailed one with 160 species and 1540 reactions. The results show that the developed approach allows computational time savings of more than one order of magnitude in comparison to a reference chemistry solver, even with no reduction of the combustion mechanism size.


2012 - 2-Stroke Externally Scavenged Engines for Range Extender Applications [Relazione in Atti di Convegno]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; Cantore, Giuseppe; P., Baldini
abstract

In this work, the authors assess the potential of the 2-Strokeconcept applied to Range Extender engines, proposing 3different configurations: 1) Supercharged, CompressionIgnition; 2) Turbocharged, Compression Ignition; 3)Supercharged, Gasoline Direct Injection. All the enginesfeature a single power cylinder of 0.49l, external air feed bypiston pump and an innovative induction system. Thescavenging is of the Loop type, without poppet valves, andwith a 4-Stroke like lubrication system (no crankcase pump).Engine design has been supported by CFD simulations, both1D (engine cycle analysis) and 3D (scavenging, injection andcombustion calculations). All the numerical models used inthe study are calibrated against experiments, carried out onengines as similar as possible to the proposed ones.The strong points found for this family of engines are: highpower density (up to 122 kW/l) and power to weight ratio;low raw emissions; compactness (design integrated with theelectric motor); low production costs (no valvetrain, no EGRsystem); excellent balance of inertia forces (thanks to thepiston pump installed on the same crankshaft, at 90° from thepower cylinder); mechanical reliability (no exotic solutions,effective lubrication system); low noise (low engine speedsthanks to the double frequency of the cycle); low specific fuelconsumption.


2011 - An Analysis on Time Scale Separation for Engine Simulations with Detailed Chemistry [Relazione in Atti di Convegno]
Perini, Federico; Cantore, Giuseppe; R. D., Reitz
abstract

The simulation of combustion chemistry in internal combustion engines is challenging due to the need to include detailed reaction mechanisms to describe the engine physics. Computational times needed for coupling full chemistry to CFD simulations are still too computationally demanding, even when distributed computer systems are exploited. For these reasons the present paper proposes a time scale separation approach for the integration of the chemistry differential equations and applies it in an engine CFD code. The time scale separation is achieved through the estimation of a characteristic time for each of the species and the introduction of a sampling timestep, wherein the chemistry is subcycled during the overall integration. This allows explicit integration of the system to be carried out, and the step size is governed by tolerance requirements. During the subcycles each of the species is only integrated up to its own characteristic timescale, thus reducing the computational effort needed by the solver. The present ODE solver was first validated using constant pressure batch reactor simulations with two different reaction mechanisms. Then the solver was coupled with the KIVA-4 code, and validated using HCCI and DI diesel combustion cases. Performance is compared with the commonly used DVODE chemistry solver and the results show that significant reductions in the total computational time with comparable accuracy are obtained with the new solution methodology.


2011 - Sviluppo motore ad alte prestazioni per vettura Formula SAE [Articolo su rivista]
A., Battaglia; Cantore, Giuseppe; Mattarelli, Enrico; Rinaldini, Carlo Alberto
abstract

Questo articolo analizza lo sviluppo teorico e sperimentale del motore che equipaggerà la monoposto dell'Università degli Studi di Modena e Reggio Emilia (UNIMORE) per le competizioni della Formula SAE, nel corso del 2011. I criteri di progettazione generale seguiti dal team UNIMORE sono di seguito discussi e confrontati con quelli scelti da altri concorrenti. In particolare, vengono illustrate in dettaglio le ragioni a sostegno della scelta del tipo di motore (monocilindrico Husqvarna). L'adozione di un monocilindrico, invece dei più potenti quattro cilindri, ha richiesto uno sforzo molto maggiore per ottenere un buon livello di potenza. Pertanto, lo sviluppo è stato massicciamente supportato da simulazioni CFD (sia 1D che 3D) e da prove sperimentali. Si è constatato che le aree di progettazione più importanti per il monocilindrico riguardano: il sistema di aspirazione, comprensivo della restrizione da 20 mm, ed il silenziatore. GT-Power è stato il principale strumento CFD utilizzato nel progetto. Dopo la calibrazione sperimentale del modello del motore originale sono state eseguite simulazioni a pieno carico, al fine di ottimizzare i parametri geometrici del motore, tenendo conto di una serie di vincoli decisi dal team o imposti dal regolamento. L’ottimizzazione effettuata non ha avuto solo l’obiettivo di ottenere il massimo della potenza, ma anche quello di trovare il miglior pacchetto motore-veicolo. È stato inoltre utilizzato un codice CFD 3D (STAR-CD) per simulare il flusso attraverso la restrizione, fornendo un aiuto fondamentale per la progettazione del Venturi e per calibrare le perdite di carico nel modello GT-Power del motore. Oltre ai calcoli stazionari condotti a pieno carico, sono state effettuate simulazioni di transitori, nella fattispecie prove di accelerazione. Sono state monitorate anche le emissioni acustiche del sistema di scarico nelle condizioni di prova indicate dal regolamento. Infine, è stata effettuata una caratterizzazione completa delle prestazioni del motore ottimizzato, prima di iniziare i test al banco. Sono state infatti elaborate delle mappe per i principali parametri prestazionali, che hanno consentito di accelerare il processo di calibrazione della centralina e di scelta dei rapporti di trasmissione per la gara di Endurance.


2011 - Validation of a combined CFD/FEM methodology for the evaluation of thermal load acting on aluminum alloy pistons through hardness measurements in internal combustion engines [Articolo su rivista]
Cantore, Giuseppe; Giacopini, Matteo; Rosi, Roberto; Strozzi, Antonio; P., Pelloni; C., Forte; M., Achiluzzi; G. M., Bianchi; L., Ceschini; A., Morri
abstract

This work presents the results of a multidisciplinary research project, carried out in close collaboration with Ducati Motor Holding S.p.A., for the development of an integrated methodology to design engine components in aluminum alloy under high thermal loads. The results refer to the study of an AA2618 (Al-Cu-Mg) alloy piston for high performance motorcycle engines. The piston has been selected as the pilot component for the development and validation of an advanced Fluid Dynamics (CFD) and Finite Element (FE) simulation methodology for the prediction of the inner thermal diffusion. The subsequent validation has been achieved through both the mechanical and microstructural characterization of the component. The methodology here presented consists of close interaction between fluiddynamics (CFD) simulations of the combustion process and Finite Element (FEM) simulations of the thermal diffusion inside the components. Combustion is the main engine heat source and is simulated by means of a threedimensional CFD code for reactive flows (FIRE v2008-AVL), with the use of advanced combustion (ECFM) and wall interaction models. The temperature map on the surfaces is based on the results of the iteration with FEM simulation of thermal diffusion. The FEM model used for the diffusion analysis receives the results of combustion analysis as input. Two different methods have been tested for the transfer of the CFD thermal load to the FEM models: a) imposition on the piston crown of a spatial distribution of heat flux averaged over the mean engine cycle; b) imposition on the piston crown of both heat flux coefficients and temperatures. The latter option allows the reduction of the number of iterations for the convergence of the thermal map inside the piston. The dissipation of the thermal load is accomplished by applying heat coefficients and temperatures, on the remaining parts of the piston surface. The validation of the CFD/FEM methodology is carried out through hardness measurements in different piston locations after bench tests. The identification of the hardness curves, as a function of temperature and time, for the T6 heat-treated AA2618 allowed the assessment of the local temperature reached by the component from the knowledge of the operating time of the engine and local hardness.


2010 - A Numerical Characterization of New High-Pressure Multi-Hole GDI Injector [Relazione in Atti di Convegno]
Malaguti, Simone; Fontanesi, Stefano; Cantore, Giuseppe
abstract

The paper reports a numerical activity aiming at investigating the spray structure originated by a new-generation GDI injector. The spray is analyzed under quiescent conditions, injecting the fuel in a test vessel at non-evaporative ambient conditions. Results from 3D-CFD simulations are compared to experimental measurements available in literature: commer-cial gasoline at two different injection pressures (10 and 20 MPa) was injected and the spray evolution was ana-lyzed throughout the injection duration.The spray was investigated along the jet axis by the phase Doppler anemometry in order to provide droplet size and velocity, in terms of both axial and radial components. Data were analyzed using the ensemble averaging technique in order to provide mean values.Experimental measurements briefly described above are used to test and validate some lagrangian spray numerical sub-models and numerical parameters such as grid density, numerical setup, primary and secondary fuel breakup and droplet to droplet interaction. Particular care is devoted to the accurate representation of the spray primary breakup, in view of the lack of ad-hoc developed models available in literature. A wide CFD activity is then performed in order to investigate grid effects on the prediction of liquid spray penetration and droplet velocity.Results from the CFD analyses show a relevant dependency of the spray structure on both the computational cell size and the adopted CFD model ensemble.


2010 - Analisi Termo-Meccanica a Fatica di un Motore Diesel Automobilistico [Relazione in Atti di Convegno]
Cantore, Giuseppe; Fontanesi, Stefano; Cicalese, Giuseppe; Strozzi, Antonio; Giacopini, Matteo
abstract

L’articolo presenta alcuni risultati relativi all’analisi termo-meccanica di un motore Diesel automobilistico. Lo studio è condotto utilizzando simulazioni disaccoppiate CFD e FEM allo scopo di valutare la resistenza a fatica del motore. Una metodologia semplificata per stimare la caratteristica termo-meccanica di testate motore soggette alle reali condizioni operative è stata proposta dagli autori in precedenti pubblicazioni [1,2], ed è ora affinata apportando rilevanti miglioramenti su entrambi i fronti di simulazione.Dal lato CFD, l’analisi CHT (conjugate heat transfer) include nel dominio di calcolo anche il metallo del basamento, dei componenti forzati della testa, nonché della guarnizione. Particolare cura è rivolta alla rappresentazione dello strato limite e all’applicazione delle condizioni al contorno termiche, in particolare alla distribuzione dei flussi termici tra i vari componenti motore. Al fine di massimizzare l’accuratezza delle previsioni CFD, sono valutati criticamente gli effetti dell’ebollizione del refrigerante sulla previsione dello scambio termico.L’accuratezza della previsione numerica viene valutata mediante confronto con misure sperimentali di temperatura in alcuni punti della testa per condizioni stazionarie di funzionamento del motore. I risultati delle simulazioni CFD, ed in particolare la distribuzione puntuale del flusso di calore all’interfaccia fluido/solido, sono trasferiti come condizione al contorno all’analisi termo-strutturale tramite una routine appositamente realizzata. Dal lato termo-meccanico, la principale novità introdotta è l’implementazione di un criterio di tipo energetico per la stima della resistenza a fatica a basso numero di cicli; tale criterio, utilizzato congiuntamente ai più classici criteri tensionali o deformativi, consente di disporre di uno strumento di progettazione capace di predire la resistenza delle singole parti del motore soggette ai differenti carichi agenti. Sono infatti analizzati carichi affaticanti sia ad alto sia a basso numero di cicli, e la metodologia proposta è applicata con successo per predire i possibili punti di innesco di fratture sulla testa e migliorare le caratteristiche del circuito di raffreddamento.


2010 - Sviluppo di un Motore Diesel Due Tempi Veloce per Propulsione Aeronautica [Relazione in Atti di Convegno]
Cantore, Giuseppe; Mattarelli, Enrico; Fontanesi, Stefano; Paltrinieri, Fabrizio; Rinaldini, Carlo Alberto; Perini, Federico; Malaguti, Simone; Severi, Elena; Cicalese, Giuseppe
abstract

Nel campo della propulsione aeronautica per velivoli leggeri, si è recentemente sollevato un forte interesse verso i motori Diesel a due tempi, allo scopo di sostituire i tradizionali motori ad accensione comandata, per i quali risulterà sempre più difficile il reperimento del carburante “avio” negli aeroporti. L’obbiettivo di questo studio è dunque quello di individuare e confrontare tra loro possibili configurazioni adatte all’applicazione aereonautica. Il propulsore scelto come riferimento è prodotto dall’azienda australiana WAM, ha una potenza di 100/120 HP, ed è dotato di sovralimentazione a due stadi, iniezione indiretta, lavaggio unidirezionale (con valvole di scarico in testa).Il primo “step” evolutivo che si è studiato è la trasformazione ad iniezione diretta, con camera a tazza ricavata nel pistone ed iniettore di tipo Common Rail: questa modifica offre il vantaggio di un notevole incremento di potenza ed efficienza, abbinata ad una riduzione delle masse radianti. Oltre a ciò, si è anche analizzato a calcolo un sistema di combustione innovativo, basato su un lavaggio ad anello, senza ausilio di valvole. A fronte della notevole compattazione del motore, aspetto assai apprezzabile in campo aeronautico, con questa soluzione risulta però più difficile ottimizzare lavaggio e combustione, mancando completamente il riferimento a motori moderni.Partendo dal motore base, è stato anzitutto costruito e calibrato sperimentalmente un modello di simulazione termo-fluidodinamico monodimensionale. In parallelo sono state svolte anche simulazioni CFD-3D utilizzando STAR-CD per l’analisi del lavaggio, e KIVA-3V per lo studio della combustione. Queste analisi di dettaglio hanno consentito di caratterizzare i principali processi termo-fluidodinamici che avvengono nelle diverse configurazioni alternative, che sono poi state poste a confronto tramite analisi di ciclo.


2010 - Sviluppo di una metodologia CFD e FEM per l’analisi a fatica di componenti motoristici [Relazione in Atti di Convegno]
Cantore, Giuseppe; Fontanesi, Stefano; Cicalese, Giuseppe; Strozzi, Antonio; Giacopini, Matteo
abstract

L’articolo presenta alcuni risultati relativi all’analisi termo-meccanica di un motore Diesel automobilistico 6 cilindri a V di cilindrata complessiva 2900cc. Lo studio è condotto utilizzando simulazioni disaccoppiate CFD e FEM allo scopo di valutare la resistenza a fatica dei componenti. La distribuzione di fluido nel circuito di raffreddamento è stata in precedenza oggetto di approfondite analisi e ottimizzazioni al fine di migliorare le caratteristiche dei passaggi del refrigerante. Una metodologia semplificata al fine di stimare la caratteristica termo-meccanica di testate motore soggette alle reali condizioni operative è stata proposta dagli autori in precedenti pubblicazioni. Come conseguenza dell’elevata complessità dei vari fenomeni coinvolti, in questo articolo si introducono alcune importanti migliorie, che consentono un’analisi più accurata della resistenza a fatica del motore, soggetto a carichi affaticanti ad alta frequenza e a bassa frequenza. La metodologia oggetto del presente articolo si basa ancora una volta sull’analisi disaccoppiata CFD e FEM, con rilevanti miglioramenti apportati su entrambi i fronti di simulazione. Dal lato CFD, si utilizza una nuova tipologia di griglia poliedrica, che riesce a combinare l’elevata risoluzione spaziale della mesh con una richiesta computazionale accettabile e un’elevata stabilità numerica della simulazione; particolare attenzione viene dedicata alla rappresentazione del flusso in parete. Mediante l’analisi CFD – CHT (conjugate heat transfer) è valutata la distribuzione puntuale del flusso di calore al refrigerante, includendo nel dominio di calcolo anche il metallo del basamento, della testa completa dei componenti forzati, nonché della guarnizione. Al fine di valutare e incrementare l’accuratezza della previsione numerica, sono stati effettuati e vengono mostrati alcuni confronti con misure sperimentali di temperatura in alcuni punti della testa per condizioni stazionarie di funzionamento del motore. Particolare cura è rivolta alla rappresentazione dello strato limite, fluidodinamico e termico. Allo stesso tempo, grande attenzione è data all’applicazione delle condizioni al contorno termiche, in particolare alla distribuzione dei flussi termici tra i vari componenti affacciati alla camera di combustione. Al fine di massimizzare l’accuratezza delle previsioni CFD, sono valutati criticamente gli effetti dell’ebollizione del refrigerante sulla previsione dello scambio termico tra refrigerante e metallo. I risultati delle simulazioni CFD, ed in particolare la distribuzione puntuale del flusso di calore sulla superficie di contatto fluido/solido, sono successivamente trasferiti come condizione al contorno all’analisi termo-strutturale per la valutazione della resistenza a fatica del componente. A tal fine, si utilizza una routine appositamente realizzata, in grado di mappare la distribuzione puntuale dei flussi termici calcolata tramite le simulazioni CFD su una griglia di calcolo ottimizzata per le analisi FEM. Dal lato termo-meccanico, la principale novità introdotta è l’implementazione di un criterio di tipo energetico per la stima della resistenza a fatica a basso numero di cicli; tale criterio, utilizzato in congiunzione con i più classici criteri tensionali o deformativi, consente di disporre di uno strumento di progettazione capace di predire la resistenza delle singole parti del motore soggette ai differenti carichi agenti. Sono infatti analizzati carichi affaticanti sia ad alto sia a basso numero di cicli, e la metodologia proposta è applicata con successo al fine di predire i possibili punti di innesco di fratture sulla testa e di migliorare le caratteristiche del circuito di raffreddamento.


2009 - A Lumped Parameter Approach for Simulation of ICE Cooling Systems [Relazione in Atti di Convegno]
Paltrinieri, Fabrizio; Cantore, Giuseppe; Perini, Federico; Rinaldini, Carlo Alberto
abstract

In this paper a detailed analysis focused on lumped parameters numerical modeling of high speed direct injected internal combustion engine cooling systems is presented and discussed. More in details, the cooling systems here studied are characterized by extreme performance, both in terms of circulating flow rates and thermal loads. First of all, a comprehensive description of the simulation environment properly tailored for cooling systems modeling is introduced and all its geometric, fluid-dynamic and thermodynamic characteristics are described in depth. Then, the model has been validated through an exhaustive numerical vs. experimental comparison, involving both cold and hot engine operation, for a wide range of rotational speeds. The general good accordance obtained between calculated and measured results clearly demonstrate the reliability of the numerical model. Finally, the main capabilities of the lumped parameters model as a useful design tool have been evidently showed by investigating different cooling circuit configurations and comparing the results here obtained with the baseline solution.


2009 - CFD investigation of wall wetting in a GDI engine under low temperature cranking operations [Relazione in Atti di Convegno]
Malaguti, Simone; Fontanesi, Stefano; Cantore, Giuseppe; A., Rosetti; R., Lupi
abstract

The paper reports a numerical activity on the investigation of the spray evolution within the combustion chamber of an automotive DISI engine under low-temperature cranking operations. In view of the high injected fuel amount and the strongly reduced fuel vaporisation at cold cranking, wall wetting becomes a critical issue. Under such conditions, fuel deposits around the spark plug region can affect the ignition process, and even prevent engine start-up. In fact, due to the low injection pressure at engine start-up, the fuel shows almost negligible atomisation and breakup, and the spray structure at the swirl-type injector nozzle is characterized by a single column of liquid fuel, strongly limiting the subsequent vaporisation and enhancing the fuel-wall interaction.In order to properly investigate and understand the many involved phenomena, experimental visualisation of the full injection process by means of an optically accessible engine would be a very useful tool. Nevertheless, the application of such technique, far from being feasible from an industrial point of view, appears to be very difficult even in research laboratories, due to the relevant wall wetting at cranking conditions.CFD analyses prove therefore to be the sole chance to gain a full insight of the overall process, to correlate spark plug wetting to both the combustion chamber design and the injection profile and eventually address either design modifications or changes in the injection strategies. In order to limit the overall number of modelling uncertainties, and to validate the spray model under actual cranking conditions, comparisons with available experimental data at low temperature and low injection pressure were performed and are reported in the paper.


2009 - CFD-3D Multi-Cycle Analysis on a New 2-Stroke HSDI Diesel Engine [Relazione in Atti di Convegno]
Cantore, Giuseppe; Fontanesi, Stefano; Malaguti, Simone; Mattarelli, Enrico
abstract

The paper describes a CFD multidimensional and multi-cycle engine analysis applied to a novel 2-Stroke HSDI Diesel engine, under development since a few years at the University of Modena and Reggio Emilia. In particular, six operating conditions are considered, two of them at full load and four at partial. The simulation tool is STAR-CD, a commercial software extensively applied by the authors to HSDI Diesel engines. Furthermore, an experimental calibration of the combustion model has been performed and reported in this paper, carrying out CFD simulations on a reference Four Stroke HSDI Diesel engine. As expected, in the multi-cycle analysis a wide dependence of pollutants on trapped charge composition has been found. Much less relevant is the cycle-by-cycle variation in terms of performance parameters, such as trapped mass, IMEP, combustion efficiency, etc. For these parameters, 2 cycle are sufficient to reach a reasonable convergence, while for pollutants 3 or more cycles are required. Information from multi-cycle simulation has been used to refine a 1D engine cycle model, providing a prediction on engine performance at several operating conditions. In particular, the influence of the combustion sub-model has been investigated, comparing the results obtained by entering empirical heat release laws to the results provided by a combustion model refined through multi-cycle 3D simulations.


2008 - Analisi Termofluidodinamica Multidimensionale del Ciclo di un Innovativo Motore Diesel, 2 Tempi Veloce [Relazione in Atti di Convegno]
Cantore, Giuseppe; Carpentiero, Davide; Fontanesi, Stefano; Malaguti, Simone; Mattarelli, Enrico
abstract

L’analisi termofluidodinamica multidimensionale del ciclo di un motore a combustione interna presenta notevoli difficoltà, sia concettuali che pratiche. Da un punto di vista teorico occorre infatti definire una metodologia in grado di simulare in maniera sufficientemente accurata tutti i complessi fenomeni che avvengono all’interno del cilindro e dei condotti (in particolare la miscelazione aria-combustibile, la combustione, l’efflusso attraverso le valvole e/o le luci). Tutt’altro che banale risulta anche la generazione della griglia di calcolo e la gestione del movimento del pistone e degli eventi di apertura e chiusura delle valvole. L’affinamento dei modelli e l’esigenza di reiterare i calcoli per più cicli consecutivi del motore si scontra poi sempre con la limitatezza delle risorse di calcolo, per quanto la potenza dei sistemi di elaborazione sia in costante espansione.Il presente articolo descrive un’analisi multidimensionale e multiciclo applicata ad un innovativo motore Diesel 2 Tempi veloce, in corso di sviluppo presso il Dipartimento di Ingegneria Meccanica e Civile dell’Università di Modena e Reggio Emilia. In particolare, sono state considerate quattro condizioni operative, due a pieno carico e due a carico parziale.Lo strumento di simulazione CFD è un software commerciale, in cui i modelli di spray e combustione sono stati calibrati sulla base di dati sperimentali, ottenuti su di un motore Diesel veloce a 4 Tempi, avente medesimo alesaggio.La metodologia utilizzata si è dimostrata in grado di fornire risultati stabili mediamente dopo tre cicli, ciascuno dei quali ha richiesto circa 200 ore di calcolo su di una macchina quadri-processore. Molto significativa è risultata essere la variazione ciclica per quello che riguarda le emissioni inquinanti, a causa delle differenze di composizione iniziale della carica.E’ stata infine valutata l’influenza delle leggi di rilascio del calore, ottenute mediante queste simulazioni multidimensionali e multiciclo, sui parametri prestazionali del motore a due tempi, calcolati con l’ausilio di un codice gasdinamico mono-dimensionale.


2008 - Development and Application of Gasoline/EtOH Combustion Mechanism: Modeling of Direct Injection Ethanol Boosted Gasoline Engine [Relazione in Atti di Convegno]
V. I., Golovitchev; Rinaldini, Carlo Alberto; Cantore, Giuseppe
abstract

Ethanol could play an important role to reduce the use of fossil fuels in the automotive industry together with asubstantial increase in the efficiency of direct injection gasoline engines. As suggested by Cohn, Bromberg, andHeywood, the concept of ethanol DI boosted gasoline engine can facilitate the high compression ratio engine operationby reducing the knock constraint. In this concept, the direct injection of ethanol was proposed as an effective knocksuppressant. As described, a small amount of ethanol could be used to reach the engine efficiency corresponding toinjection of larger (by 30 %) amount of gasoline. Gasoline consumption and out emissions would be reduced by 25%.The concept has been validated for the small bore model engine using the KIVA3V code supplemented by the detailed chemistry approach. The chemical mechanism for gasoline surrogate/ethanol blend was constructed consisting of 129 species participating in 700 reactions. The gasoline surrogate model was constructed using sub-mechanisms for constituent components (iso-octane, toluene, and n-heptane in a selected proportion) from classes of hydrocarbons typical for gasoline. The mechanism was validated using shock-tube auto-ignition data taken from Sakai (University of Tokyo) and Gauthier (Stanford University) data compilations. The sub-mechanism of ethanol combustion is described by the reduced mechanism of Marinov (LLNL). The KIVA3V code was modified to treat the chemical mechanism developed and allowing injections of different fuels. The numerical results illustrate the possible efficiency gain for the model DI gasoline engine with conventional compression ratio within the range of 10-20% by ethanol injection in 10-20% of the total amount of fuel.


2008 - Fondamenti di Motori Endotermici Alternativi con cenni di controllo [Monografia/Trattato scientifico]
Cantore, Giuseppe
abstract

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2008 - Lumped Parameters Numerical Simulation of a Variable Displacement Vane Pump for High Speed ICE Lubrication [Relazione in Atti di Convegno]
Cantore, Giuseppe; Milani, Massimo; Paltrinieri, Fabrizio; F., Tosetti
abstract

In this paper a detailed analysis focused on lumped parameters numerical modelling of a variable displacement vane pump for high-speed internal combustion engine lubrication is presented and discussed. This particular volumetric unit is characterized by very extreme performance, both in terms of rotational speed, delivery pressure and displacement variation.First of all, a comprehensive description of the simulation environment properly tailored for the numerical modelling of the vane pump operation is introduced and all its geometric, kinematic and fluid-dynamic characteristics are described in depth. Then, the results coming from an exhaustive experimental campaign have been compared with simulations, finding a general good accordance that demonstrates the reliability of this numerical approach. Finally, the capabilities of the validated model have been applied to investigate the influence exerted by the main geometrical parameters and internal leakages on the pump fluid dynamic behavior.


2007 - A NEW CONCEPT FOR ULTRA-COMPACT AUTOMOTIVE HSDI DIESEL ENGINES [Relazione in Atti di Convegno]
Mattarelli, Enrico; Cantore, Giuseppe
abstract

The Department of Mechanical and Civil Engineering (DIMeC) of the University of Modena and Reggio is developing a new concept of small capacity HSDI 2-Stroke Diesel engine, featuring a specifically designed combustion system. The paper reviews the 2-Stroke engine design process, supported by CFD simulations, both 1D and multi-dimensional.A four stroke automobile Diesel engine is taken as a reference for a theoretical comparison in terms of brake performance at both full and partial load. This comparison shows the potential of the 2-Stroke, as an ultra-compact, efficient and clean engine.


2006 - Analysis of a HSDI diesel engine intake system by means of multi-dimensional numerical simulations: influence of non uniform EGR distribution [Relazione in Atti di Convegno]
Cantore, Giuseppe; DE MARCO, Carlo Arturo; Montorsi, Luca; Paltrinieri, Fabrizio; Rinaldini, Carlo Alberto
abstract

In order to comply with stringent pollutant emissions regulations a detailed analysis of the overall engine is required, assessing the mutual influence of its main operating parameters. The present study is focused on the investigation of the intake system under actual working conditions by means of 1D and 3D numerical simulations. Particularly, the effect of EGR distribution on engine performance and pollutants formation has been calculated for a production 6 cylinder HSDI Diesel engine in a EUDC operating point. Firstly a coupled 1D/3D simulation of the entire engine geometry has been carried out to estimate the EGR rate delivered to every cylinder; subsequently the in-cylinder flow field has been evaluated by simulating the intake and compression strokes. Finally the spray and combustion processes have been studied accounting for the real combustion chamber geometry and particularly the pollutants formation has been determined by using a detailed kinetic mechanism combustion model. The 1D/3D analysis highlighted a significant cylinder to cylinder EGR percentage variation affecting remarkably the pollutant emissions formation, as evaluated by the combustion process simulations. A combined use of commercial and in-house modified codes has been adopted.


2006 - Analysis of a HSDI diesel engine intake system by means of multi-dimensional numerical simulations: Influence of now uniform EGR distribution [Relazione in Atti di Convegno]
Cantore, G.; De Marco, C. A.; Montorsi, L.; Paltrinieri, F.; Rinaldini, C. A.
abstract

In order to comply with stringent pollutant emissions regulations a detailed analysis of the overall engine is required, assessing the mutual influence of its main operating parameters. The present study is focused on the investigation of the intake system under actual working conditions by means of ID and 3D numerical simulations. Particularly, the effect of EGR distribution on engine performance and pollutants formation has been calculated for a production 6 cylinder HSDI Diesel engine in a EUDC operating point. Firstly a coupled 1D/3D simulation of the entire engine geometry has been carried out to estimate the EGR rate delivered to every cylinder; subsequently the in-cylinder flow field has been evaluated by simulating the intake and compression strokes. Finally the spray and combustion processes have been studied accounting for the real combustion chamber geometry and particularly the pollutants formation has been determined by using a detailed kinetic mechanism combustion model. The 1D/3D analysis highlighted a significant cylinder to cylinder EGR percentage variation affecting remarkably the pollutant emissions formation, as evaluated by the combustion process simulations. A combined use of commercial and in-house modified codes has been adopted. Copyright © 2006 by ASME.


2006 - CFD optimisation of the in-cylinder flow patterns in a small unit displacement HSDI Diesel Engine for off-highway applications [Relazione in Atti di Convegno]
Cantore, Giuseppe; Fontanesi, Stefano; Gagliardi, Vincenzo; Malaguti, Simone
abstract

The aim of the paper is to provide information about the in-cylinder flow field optimisation in a high speed, direct injection (HSDI) four valve per cylinder diesel engine for off-highway applications.Fully transient CFD analyses of different valve profile strategies for the intake and compression strokes are at first performed, in order to evaluate the effects on both engine permeability and in-cylinder flow field evolution. Modifications are applied to each intake valve separately: gradually stretched cam profiles are imposed so that strategies range from the standard operation, i.e. the adoption of a unique cam profile for the two intake valves, up to the limit case characterized by a 40 % difference between the intake valves maximum valve lifts for three different engine conditions. Organized flow structures (i.e., swirl) and turbulent flow patterns are investigated, in order to address rules for ad-hoc strategies aiming at finding the best trade off between engine performance and pollutant emission.The effectiveness of the valve strategies is validated by means of full injection and combustion simulations using state of the art models. At first, results for the base case are validated against experiments; subsequently, both full-load / peak-torque and mid-load / low-speed operations for the most promising cases are performed.Relative valve profile strategies prove to strongly influence the flow field within the combustion chamber, and therefore the subsequent spray evolution and fuel combustion, confirming the importance of an ad-hoc optimization in order to meet the best trade-off between performance and pollutant emissions.


2006 - Primi Risultati dello Sviluppo di un Motore Diesel Veloce a Due Tempi di Nuova Concezione [Relazione in Atti di Convegno]
Cantore, Giuseppe; DE MARCO, Carlo Arturo; Mattarelli, Enrico; Paltrinieri, Fabrizio; Tosetti, Federico
abstract

Fin dall’inizio degli anni Novanta, numerosi tentativi sono stati fatti per applicare il ciclo a due tempi ai motori Diesel veloci: si ricordano ad esempio i prototipi automobilistici realizzati da Toyota, Yamaha e AVL; nel campo aeronautico vi sono addirittura già alcuni esemplari in commercio (DeltaHawk, Zoche, Diesel Air, Wilksh Airmotive). La superiorità del Diesel due tempi rispetto al quattro tempi è ormai accertata in termini di rapporto peso-potenza ed emissioni di NOx; qualche dubbio sussiste tuttavia per quello che riguarda il consumo specifico e le emissioni di particolato. All’interno del Dipartimento di Ingegneria Meccanica e Civile dell’Università di Modena e Reggio Emilia è attivo da qualche tempo un progetto che ha come iniziale obiettivo lo studio della fattibilità e la previsione delle prestazioni di un nuovo tipo di motore a due tempi Diesel veloce. Tale studio, i cui principali risultati finora ottenuti sono presentati in questo articolo, si avvale principalmente di simulazioni CFD, sia mono che multi-dimensionali, includendo anche la combustione. Per poter valutare le potenzialità del nuovo motore si è assunto come riferimento un motore a quattro tempi Diesel automobilistico, del quale sono note sperimentalmente tutte le caratteristiche e di cui si sono effettuate anche svariate simulazioni. Dal confronto finora effettuato tra il quattro tempi di riferimento ed il nuovo motore due tempi, sono emerse indicazioni estremamente confortanti circa la validità del concetto proposto.


2005 - Effects of Relative Port Orientation on the In-Cylinder Flow Patterns in a Small Unit Displacement HSDI Diesel Engine [Relazione in Atti di Convegno]
Cantore, Giuseppe; Fontanesi, Stefano; Gagliardi, Vincenzo; Malaguti, Simone
abstract

The paper aims at providing information about the in-cylinder flow structure and its evolution of a high speeddirect injection (HSDI) four valve per cylinder engine for off-highway applications.Fully transient CFD analyses by means of state-of-the-art tools and methodologies are carried out for the wholeintake and compression strokes, in order to evaluate port effects on both engine permability and in-cylinder flowfield evolution. Organized mean motions (i.e., swirl, tumble and squish) are investigated, trying to establishgeneral rules in the port design optimization process, addressing relationships between the relative portorientation and the in-cylinder flow structure. Different port configurations are compared, each deriving from therotation of the BASE port configuration on two different planes, the former being perpendicular to the cylinderaxis, while the latter being parallel to the cylinder axis.Relative intake port orientation proves to strongly influence the flow field evolution within the combustionchamber, and is therefore expected to play a non negligible role on the subsequent spray evolution and fuelcombustion.


2005 - Large-scale CFD Approach for Spray Combustion Modeling in Compression Ignited Engines [Relazione in Atti di Convegno]
Cantore, Giuseppe; V. I., Golovitchev; J., Gustavsson; Montorsi, Luca; F. E., Corcione
abstract

Computational simulations of the spray combustion and emissions formation processes in a heavy-duty DI diesel engine and in a small-bore DI diesel engine with a complicated injection schedule were performed by using the modified KIVA3V, rel. 2 code. Some initial parameter sets varying engine operating conditions, such as injection pressure, injector nozzle diameter, EGR load, were examined in order to evaluate their effects on the engine performance. Full-scale combustion chamber representations on 360-deg, Cartesian and polar, multiblock meshes with a different number of sprays have been used in the modelling unlike the conventional approach based on polar sector meshes covering the region around one fuel spray. The spray combustion phenomena were simulated using the detailed chemical mechanism for diesel fuel surrogate (69 species and 306 reactions). The simulations have been performed for Isotta Fraschini (DI diesel, 7 sprays) and Volvo NED5 (DI diesel, 10 sprays) engines, which are currently under development. Numerical results were predicted in agreement with typical experimental trends for such engines.


2005 - Optimization of a Cooling Circuit in an Internal Combustion Engine for Marine Applications [Relazione in Atti di Convegno]
Cantore, G.; Fontanesi, S.; Gagliardi, V.; Malaguti, S.; Baldini, A.; Giacopini, M.; Strozzi, A.; Rosi, R.
abstract

An optimization study involving both fluid-dynamic and thermostructural aspects has been carried out for a 2200 cc turbocharged engine head for marine applications. In this cross-disciplinary problem, the structural and thermodynamic aspects have been decoupled. A preliminary set of CFD numerical analyses of the cooling jacket layout has been performed, in order to investigate critical aspects of the present configuration and improve the cooling performance, by means of local flow patterns and flow distribution analysis. At a second stage, temperature distributions within the metal cast parts have been derived from CFD in order to assess the fatigue strength of the component with structural finite elements. A proper choice of both CFD methodology and boundary conditions is carried out in order to determine a trade-off between computational effort and actual engine behavior representation. The proposed modelling procedure allows a sensitivity study to be carried out of the engine head to variations of the leading geometric parameters, thus devising an optimized component. The methodology favored in this study is finally applied to carry out a comparison between the basic configuration and a fluid-dynamic improved solution, in order to estimate the effectiveness of the design optimization on the fatigue strength of the component.


2004 - Comparison Between Steady and Unsteady CFD Simulations of Two Different Port Designs in a Four Valve HSDI Diesel Engine: Swirl Intensity and Engine Permeability [Relazione in Atti di Convegno]
Fontanesi, Stefano; Cantore, Giuseppe; Montorsi, Luca; P., Ortolani
abstract

Swirl control strategies are useful methods for controllingmixture formation in HSDI Diesel engines. Test rigs allowsonly steady state measurements of the Swirl number, and giveonly a rough estimation of the charge motion during the actualcompression stroke within the engine. On the contrary, CFDsimulations are powerful tools to characterize the air flowdrawn into the cylinder, since they allow not only steady stateoperations, but also full dynamic modeling of the intake andcompression strokes. This paper studies an application ofcomputational fluid dynamics for predicting intake swirlintensity in an automotive 4 valve per cylinder D.I. Dieselengine. Two different intake ports are compared and the besttrade off between engine permeability and swirl intensity isassessed. Both steady state and dynamic simulations of theinduction process are carried out, and results demonstrate thatsteady state analysis is a reliable tool for predicting the portpermeability, while the same capability is not proved ininvestigating the organized charge motion within the chamber.


2004 - Comparison of Four Stroke MotoGP engines [Relazione in Atti di Convegno]
Mattarelli, Enrico; Cantore, Giuseppe
abstract

This paper compares different engine solutions for the FIM MotoGP World Championship. Starting from the general guidelines given in a previous paper, in this study the specific features of each engine architecture (3 and 4 in line, V4, V5 and V6) are considered. 1-D engine simulations, based on a previously validated model, are extensively used to optimize each solution, as well as to provide a comparison among the engines in terms of dynamometer performances. Some issues concerning engine balance, engine overall dimensions, intake and exhaust system lay-out are discussed. Finally, the influence of the engine on the bike acceleration is calculated by means of a simple simulation at the Mugello track.


2004 - Optimization of the Intake System on Diesel Engines Featuring a High Pressure Injection System [Capitolo/Saggio]
Borghi, Massimo; Cantore, Giuseppe; Mattarelli, Enrico; Milani, Massimo; Fontanesi, Stefano; Montorsi, Luca; D., Balestrazzi
abstract

Combustion in Diesel engines is controlled by the interaction between fuel jet and mean and turbulent flow field. Therefore, the use of novel fuel injection strategies should be always integrated with the optimisation of the mean and turbulent flow field within the cylinder. While in the last years injection system technology has evolved at an impressive rate, establishing new standards, the development of design criteria for intake ports, ducts and plenums is not keeping the same pace. The authors believe that a substantial work should be carried out in this field. For this purpose numerical simulation should play a fundamental role to cut development time, as well as to gain a better understanding of the complex thermo-fluid-dynamics phenomena occurring within the engines.This paper reviews the fundamentals of the experimental and theoretical work carried out at DIMEC-University of Modena and Reggio for supporting the development of more efficient HSDI Diesel engines.


2004 - Similarity Rules and Parametric Design of Four Stroke MotoGP engines [Relazione in Atti di Convegno]
Mattarelli, Enrico; Cantore, Giuseppe
abstract

The design of 4-stroke engines, complying with the new Motorcycle Road Racing World Championship regulations is discussed. Similarity rules and non dimensional parameters from a database on racing engines are used to define some general guidelines. More specific information about friction losses and combustion is derived from experiments, carried out on a 3-cylinder MotoGP prototype engine. These experiments provided the input needed to set up and validate a base model for 1D thermo-fluid-dynamic calculations. Engine simulation is employed for optimizing several design parameters. A comparison between the proposed methodology and a few design criteria presented in literature is made. Finally, the brake performances of some optimized engines are predicted .


2003 - A 3D CFD Analysis of the High Speed Premixed Combustion Process [Relazione in Atti di Convegno]
G. M., Bianchi; Cantore, Giuseppe; T., Baritaud; N., Pini
abstract

n.d.


2003 - SI Engines 1D Modeling: Prediction of Brake Performance Parameters and Emissions. [Relazione in Atti di Convegno]
Cantore, Giuseppe; Mattarelli, Enrico; A., Onorati; G., D'Errico
abstract

1D simulation codes, including thermodynamic, fluid dynamic and chemical models, are fundamental tools for engine design and optimization. The GASDYN code, developed by the authors at the Politecnico of Milano, has been used to analyze the operations of a Maserati S.I., naturally aspirated, V8 engine. An experimental campaign was previously carried out on this engine, including the measurement of brake performance parameters and exhaust emissions and in-cylinder pressure cycles, for several operating conditions at both full and partial load. This large amount of data allowed the authors to set up and validate at full load a numerical model of the engine. A multi-zone fractal model has been employed to predict combustion heat release, as well as NO, CO and HC emissions. After the experimental validation, the engine model has been used to calculate engine performances and emissions at partial load. A very satisfactory agreement was found.


2003 - The Influence of Cylinder Cut-out on High Performance Engines Fuel Efficiency [Relazione in Atti di Convegno]
Cantore, Giuseppe; Mattarelli, Enrico; N., Pini
abstract

Cylinder cut-out is a very promising strategy to reduce fuel consumption at partial load on high performance, big capacity S.I. engines. The simplest way to deactivate a set of cylinders is to design an air metering system featuring a separate control on the gas flow delivered by the firing cylinders and the deactivated ones. Particularly, the throttle valve controlling the motored cylinders should be kept wide open, in order to reduce pumping losses, while the opening angle of the other throttle should be electronically modulated in order to meet the load target. In this way, total pumping losses are strongly reduced, thus fuel efficiency is enhanced. The benefit of the strategy described above, along with a traditional VVA control, is evaluated with reference to two high performance naturally aspirated engines, produced by Ferrari and Maserati. The study is carried out by means of 1D cycle simulations, integrated by experimental data. It was found that the increase of fuel efficiency in the European Driving Cycle is consistent (12-19%), while the fully electronic power train management should minimize drawbacks.


2002 - A methodology for the in-cylinder flow field evaluation in a low stroke-to-bore SI engine [Relazione in Atti di Convegno]
Cantore, Giuseppe; Fontanesi, Stefano; Mattarelli, Enrico; Bianchi, G. M.
abstract

This paper presents a methodology for the 3D CFD simulation of the intake and compression processes of four stroke internal combustion engines.The main feature of this approach is to provide very accurate initial conditions by means of a cost-effective initialization step. Calculations are applied to a low stroke-to-bore SI engine, operated at full load and maximum engine speed. It is demonstrated that initial conditions for this kind of engines have an important influence on flow field development, particularly in terms of mean velocities close to the firing TDC


2002 - Analysis of a 6 cylinder turbocharged HCCI engine using a detailed kinetic mechanism [Relazione in Atti di Convegno]
Cantore, Giuseppe; Montorsi, Luca; F., Mauss; P., Amnéus; O., Erlandsson; B., Johansson; T., Morel
abstract

When analyzing HCCI combustion engine behavior,the integration of experimental tests and numericalsimulations is crucial. Investigations of possible enginecontrol strategies as a function of the different operatingconditions have to take the behavior of the whole HCCIengine into account, including the effects both of thecombustion process and of complex devices. Thereforethe numerical simulation code must be able both to modelaccurately the gas-dynamic of the system and to evaluatethe combustion chemical kinetics.This paper focuses on the coupling between thecommercial one-dimensional fluid-dynamic GT-PowerCode and our in-house detailed chemical kinetic IgnitionCode. An interface has been developed in order toexchange information between the two codes: the IgnitionCode considers as boundary conditions the GT-PowerCode values provided for the gas composition at IVC andthe pressure and temperature at every time step andpasses back to GT-Power the burnt fuel fraction andstores in an external file the in cylinder gas composition.Thus the whole engine cycle can be accurately simulated,estimating the interactions between the gas-dynamicsphenomena along the intake and exhaust pipes andthrough the valves, and the chemical processes occurringduring the closed valves period.This tool makes it possible to analyze the enginebehavior under duty cycle operating conditions, andtherefore it represents a useful support to theexperimental measurements, reducing the number oftests required to assess the proper engine controlstrategies.


2002 - CFD Analysis of the In-Cylinder Flow in DI Diesel Engines [Capitolo/Saggio]
Borghi, Massimo; Cantore, Giuseppe; Mattarelli, Enrico; Milani, Massimo; Fontanesi, Stefano; Montorsi, Luca
abstract

Non disponibile


2002 - On application of nonlinear k-epsilon models for internal combustion engine flows [Articolo su rivista]
Gm, Bianchi; Cantore, Giuseppe; P., Parmeggiani; V., Michelassi
abstract

The linear k-epsilon model, in its different formulations, still remains the most widely used turbulence model for the solutions of internal combustion engine (ICE) flows thanks to the use of only two scale-determining transport variables and the simple constitutive relation. This paper discusses the application of nonlinear k-epsilon turbulence models for internal combustion engine flows. Motivations to nonlinear eddy viscosity models use arise from the consideration that such models combine the simplicity of linear eddy-viscosity models with the predictive properties of second moment closure. In this research the nonlinear k-epsilon models developed by Speziale in quadratic expansion, and Craft et al. in cubic expansion, have been applied to a practical tumble flow Comparisons between calculated and measured mean velocity components and turbulence intensity were performed for simple flow structure case. The effects of quadratic and cubic formulations on numerical predictions it ere investigated too, with particular emphasis on anisotropy and influence of streamline curvature on Reynolds stresses.


2002 - Turbulence Modelling in CFD Simulations of ICE Intake Flows: The Discharge Coefficient Prediction [Relazione in Atti di Convegno]
G. M., Bianchi; Cantore, Giuseppe; Fontanesi, Stefano
abstract

The paper is focused on the influence of theeddy viscosity turbulence models (EVM) in CFD threedimensionalsimulations of steady turbulent engineintake flows in order to assess their reliability inpredicting the discharge coefficient. Results have beenanalyzed by means of the comparison with experimentalmeasurements at the steady flow bench. High Reynoldslinear and non-linear and RNG k-ε models have beenused for simulation, revealing the strong influence ofboth the constitutive relation and the ε-equationformulation on the obtained results, while limits in theapplicability of more sophisticated near-wall approachesare briefly discussed in the paper.Due to the extreme complexity of typical ICEflows and geometries, the analysis of the behavior ofEVM turbulence models has been subsequently appliedto a test-case available in literature, i.e. a high-Reynoldscompressible flow over a inclined backward facing step(BFS). Different high-Reynolds and low-Reynolds linearand quadratic k-ε models, linear and quadratic RNG k-εmodels and linear and quadratic two-layer models havebeen used for simulation. The predicted mean velocityprofiles at different locations along the duct have beencompared versus experiments available in literature.


2001 - A new concept of supercharging applied to high speed DI Diesel engines [Relazione in Atti di Convegno]
Cantore, Giuseppe; Mattarelli, Enrico; Fontanesi, Stefano
abstract

The supercharging system investigated in this study is made up of a traditional turbocharger, coupled with a Roots-type positive displacement compressor. An electrically actuated clutch allows the compressor to be disengaged from the engine at high speed and under partial load steady operations (such as the ones occurring in a driving cycle).This concept of supercharging has been applied to the downsizing of a reference engine (a 2.5 litre, turbocharged, four cylinder, high speed DI Diesel engine), without penalization on the maximum brake power (110 kW) and transient response.For such a purpose, a “paper” engine has been theoretically characterized. The gross engine parameters have been optimised by means of 1-D numerical simulations, using a computational model previously validated against experiments.Performances of the reference and the downsized engine have been compared, considering both steady and transient operating conditions, full and partial load. The two-stage supercharging system allows the “paper” engine to provide higher values of torque at low engine speed and full load, and to perform slightly better in terms of transient response. Furthermore, when considering operating conditions occurring in the European Driving cycle (Roots compressor disengaged), the downsized engine shows lower fuel consumption (from 6 to 24%), and lower pollutant emissions.


2001 - La sovralimentazione volumetrica per motori ad accensione comandata ad alte prestazioni [Relazione in Atti di Convegno]
Cantore, Giuseppe; Fontanesi, Stefano; Mattarelli, Enrico; Montorsi, Luca
abstract

Analisi numerica monodimensionale dei vantaggi derivanti dalla sovralimentazione applicata ai motori ad accensione comandata, nell'ottica dell'engine downsizing.


2001 - Turbulence modelling in CFD simulation of ICE intake flow [Relazione in Atti di Convegno]
Bianchi, G. M.; Cantore, Giuseppe; Fontanesi, Stefano
abstract

The paper is focused on the influence of the eddy viscosity turbulence models (EVM) in CFD three-dimensional simulations of steady turbulent engine intake flows in order to assess their reliability in predicting the discharge coefficient. Results have been analyzed by means of the comparison with experimental measurements at the steady flow bench. High Reynolds linear and nonlinear and RNG k-ge models have been used for simulation, revealing the strong influence of both the constitutive relation and the -equation formulation on the obtained results, while limits in the applicability of more sophisticated near-wall approaches are briefly discussed in the paper. Due to the extreme complexity of typical ICE flows and geometries, the analysis of the behavior of EVM turbulence models has been subsequently applied to a test-case available in literature, i.e., a high-Reynolds compressible flow over an inclined backward-facing step (BFS). Different high-Reynolds and low-Reynolds linear and quadratic k-ge models and linear and quadratic two-layer models have been used for simulation. The predicted velocity profiles at different locations along the duct have been compared versus experiments available in literature. The EVM model constitutive relation as well as near-wall treatment was found to be fundamental for accurately predicting the flow characteristics. In the recirculation regions the nonlinear EVM models behave much better than the standard linear EVM thanks to their more accurate physical ground, thus determining the best agreement with experimental data. Simulations revealed also limits of the RANS approach and related EVM when faced with typically unsteady and complex phenomena like flow separation as those occurring in engine intake ducts.


2000 - Analisi del comportamento dinamico del circuito idraulico di selezione marcia di una vettura di Formula 1 [Relazione in Atti di Convegno]
Cantore, Giuseppe; Borghi, Massimo; Piraccini, M.; Baccolini, D.; Flandoli, M.
abstract

n.d.


2000 - Analisi del “Matching” motore - turbocompressore in un motore Diesel automobilistico ad iniezione diretta [Relazione in Atti di Convegno]
Cantore, Giuseppe; Fontanesi, Stefano; Mattarelli, Enrico; Montorsi, Luca; Luppino Bertoni, F.
abstract

n.d.


2000 - Similarity rules and parametric design of race engines [Relazione in Atti di Convegno]
Boretti, A.; Cantore, Giuseppe
abstract

The paper shows results fom the comparison between V10 and V12 engines for racing applications. Results are derived from a combination of experimental data and 1d simulations.


1999 - Experimental and theoretical analysis of a Diesel fuel injection system [Relazione in Atti di Convegno]
A. A., Boretti; Cantore, Giuseppe; Mattarelli, Enrico
abstract

The paper presents experimental and theoretical results obtained for a mechanical Diesel fuel injection system, made up of a distributor-type pump, four delivery pipes and four four-hole injectors. Pressure in the pumping chamber, in two locations along the fuel line and within the injector is measured directly, as well as the injector needle lift. The flow rate is evaluated through the measure of pressure in the injection chamber.Experimental results are sustained by theoretical results. The numerical model considers systems of ordinary differential equations representing the operation of injector, pump, delivery valve and line volume elements. Only a few model details are presented. Similar approaches are in use by many years, and the accuracy they provide is generally accepted to be fairly good. Theoretical and experimental results are presented vs. the time at different pump speeds, showing a very satisfactory accuracy.The main objective of the paper is to describe the unsteady flow within the injector, and to show differences with reference to the steady flow. Despite the subject is not adequately covered in the open literature, several reasons suggest that steady and unsteady flow behaviors differ considerably. These differences may affect the prediction of both injection pressure and flow rate.


1999 - Le forze Radiali in Valvole a Cassetto [Articolo su rivista]
Borghi, Massimo; Cantore, Giuseppe; Milani, Massimo; R., Paoluzzi
abstract

A partire dal calcolo della spinta radiale agente sulle porzioni di cursore in ricoprimento, la memoria illustra le linee guida principali per un corretto dimensionamento e posizionamento delle scanalature circonferenziali di bilanciamento.


1999 - Macchine [Monografia/Trattato scientifico]
Cantore, Giuseppe
abstract

n.d.


1999 - Modeling Atomization of High-Pressure Diesel Sprays [Relazione in Atti di Convegno]
Cantore, Giuseppe; G. M., Bianchi; P., Pelloni
abstract

n.d.


1999 - Numerical analysis of the influence of the stroke to bore ratio on tumble breakdown [Relazione in Atti di Convegno]
Bianchi, GIAN MARCO; Cantore, Giuseppe; D., Nicolini; L., Sassi; L., Fraboni
abstract

n.d.


1999 - Variable Displacement Axial Piston Pump Volumetric Efficiency Analysis [Relazione in Atti di Convegno]
Cantore, Giuseppe; Borghi, Massimo; Milani, Massimo
abstract

This paper describes a study of the volumetric efficiency of a variable displacement axial piston pump. A theoretical model, based on the continuity equation and properly combined with a simplified analytical treatment of leakage flows, is first presented and used to characterise the stationary behaviour of a 9 piston pump for different operating conditions and different configurations. In this study attention is focused on pump volumetric efficiency dependency on overall operational conditions as supply pressure, pump speed, leakage clearance heights, swash plate angle and port plate timing. Successively, a numerical vs. experimental comparison of steady-state pump characteristics is presented; this last part of the paper has been developed with the aim of showing the validity limits of the assumptions made to build up the numerical model. Results confirm the applicability of the simplified hypotheses introduced and validates the analysis of volumetric efficiency previously performed.


1998 - Analisi della Risposta Dinamica del Circuito di Comando degli Attuatori di un Escavatore [Relazione in Atti di Convegno]
Borghi, Massimo; Cantore, Giuseppe; Milani, Massimo; A., Valentini
abstract

Vengono presentati i risultati ottenuti dallo studio del comportamento dinamico del circuito idraulico di comando degli attuatori di un escavatore. Più nel dettaglio, utilizzando il codice commerciale AMESim è stato messo a punto un modello di simulazione numerica a parametri concentrati dei circuito idraulico di comando della benna posteriore di un escavatore, per studiare la risposta di uno degli attuatori lineari (il boom cylinder) nella condizione di carico trascinante. L'analisi della risposta dinamica dei sistema idraulico ha permesso di evidenziare come, nella particolare condizione operativa imposta, la discesa dei carico non risulti facilmente controllabile dall'operatore, e venga ad essere completata in un tempo particolarmente breve. L'inserimento di una valvola di bilanciamento (o di overcenter) di corrente produzione industriale, come componente di controllo e di sicurezza, tra il martinetto di comando della benna e il circuito idraulico, ha permesso di verificare come tale componente possa esercitare la sua funzione in presenza di un comando a pressione costante applicato al suo stadio di pilotaggio. Allo scopo è stato previsto l'utilizzo di un accumulatore a precarica sulla linea di pilotaggio della valvola di bilanciamento, in grado, inoltre, di assorbire le eventuali pulsazioni di pressione nella camera lato pistone del boom cylinder, indotte dall'elasticità della struttura meccanica. L'ultima parte del lavoro è dedicata alla scelta della pressione di precarica e dei volume dell'accumulatore, ai fini del raggiungimento della configurazione necessaria ad assicurare il completo controllo della fase di discesa dei carico.


1998 - Analysis of hydraulic components using computational fluid dynamics models [Articolo su rivista]
Borghi, Massimo; Cantore, Giuseppe; Milani, Massimo; R., Paoluzzi
abstract

This paper presents some results obtained during the computational fluid dynamics (CFD) analysis of internal flows inside a hydraulic component, using a scaling technique applied to numerical pre- and post-processing. The main aim of the work is to demonstrate the reduction of computational work needed for a complete analysis of component behaviour over a wide range of operating conditions. This result is achieved through the adoption of a methodology aimed at giving the highest level of generality to a non-dimensional solution, thereby overcoming the two major limitations encountered in the use of CFD in fluid power design: computer resources and time. In the case study, the technique was applied to a hydraulic distributor and computations were performed with a commercial computational fluid dynamics code. The key factor of this technique is the evaluation, for a given distributor opening, of the Reynolds number of the flow in the metering region. Provided that this number is high enough to ensure that the discharge coefficient has reached its asymptotic value, the characterization of the flow by a single non-dimensional numerical run can be shown. The theoretical contents of the analysis of the re-scaling technique, which focuses on the engineering information necessary in component design, are described in detail. The bases for its subsequent application to actual cases are then outlined. Finally, a fairly close correlation between numerical results and experimental data is presented.


1998 - "Comparison of V10 and V12 F1 Engines" [Articolo su rivista]
A. A., Boretti; Cantore, Giuseppe
abstract

The paper compares 3.0 liter F1 engines having different architectures and developed in compliance with the 1998 FIA technical regulations. Similarity rules and non dimensional parameters from previous projects define key geometry and operating parameters for V10 and V12 engines having equal degree of sophistication. The paper presents computed classical engine outputs versus engine speed, including brake, indicated and friction values. The V12 solution shows clear advantages in terms of pure engine performances.


1998 - Mehrdimensionale Stromungs- und Verbrennungsmodelle [Articolo su rivista]
Cantore, Giuseppe; G. M., Bianchi; G., Guerrini; F., Papetti
abstract

N.D.


1998 - Numerical analysis of the lateral forces acting on spools of hydraulic components. [Relazione in Atti di Convegno]
Borghi, Massimo; Cantore, Giuseppe; Milani, Massimo; Paoluzzi, Roberto
abstract

This paper deals with the analysis of pressure distribution within the fluid film in the clearance between spool and sleeve of hydraulic components, in order to predict the value of the locking force induced by unbalanced pressure acting on tapered geometries. Particular care is devoted to the investigation of the lateral force dependency on clearance and eccentricity of the spool. Some theoretical results are presented, obtained solving (by the finite difference method) the two dimensional Reynolds equation for the fluid film. These results are then compared to those deriving from a generally adopted predictive formula. Results show remarkable differences, up to 70 %, in presence of high values of eccentricity. Moreover, an analogous Reynolds' based solution is performed for a tapered geometry of the spool with one balancing groove, with particular attention to the influence of its length and position on resulting locking force and leakage flow. Also the locking force reducing effect of a balancing groove is characterized, and a saturated behavior when the groove is placed very close to the high pressure spool side has been found.


1998 - The Influence of Stroke-to-Bore Ratio and Combustion Chamber Design on Formula One Engines Performance [Relazione in Atti di Convegno]
Mattarelli, Enrico; G. M., Bianchi; Cantore, Giuseppe; G., Guerrini; F., Papetti
abstract

This paper presents a numerical study of the combustion chamber design influence on the performance of racing engines. The analysis has been applied to the Ferrari 10 cylinder 3.0 liter S.I. engine adopted in Formula One racing.


1997 - Analisi termofluidodinamica di sistemi di scarico per motore automobilistico aspirato ad accensione comandata [Relazione in Atti di Convegno]
Cantore, Giuseppe; Mattarelli, Enrico; G. M., Bianchi
abstract

Le prestazioni di un motore alternativo a combustione interna sono principalmente influenzate dall'efficienza dei processi di ricambio della carica. Lo studio di tali processi, possibile con l'ausilio di codici termofluidodinamici 1-D, costituisce pertanto una base per l'ottimizzazione dei sistemi di aspirazione e scarico.In questo lavoro sono anzitutto discussi gli aspetti fluidodinamici caratteristici ed i criteri di progetto del sistema di scarico per un motore aspirato a quattro tempi, policilindrico.Lo studio e' stato quindi indirizzato ad un motore automobilistico di produzione Maserati, 8 cilindri a V, di cui sono definite tutte le caratteristiche tranne la geometria del sistema di scarico. Per le due configurazioni dello scarico piu' comunemente impiegate in una bancata a quattro cilindri (4-1 e 4-2-1), e tenendo conto dei vincoli progettuali, e' stata effettuata un'analisi d'influenza dei parametri geometrici ritenuti piu' significativi.La migliore soluzione 4-2-1 fornisce, rispetto alla corrispondente 4-1, prestazioni piu' elevate ai medi regimi di rotazione.


1997 - Bilanciamento delle Macchine Oleodinamiche ad Ingranaggi Esterni [Relazione in Atti di Convegno]
Cantore, Giuseppe; Borghi, Massimo; Milani, Massimo
abstract

n.d.


1997 - Distribuzione della pressione nei vani di una pompa a palette [Relazione in Atti di Convegno]
Borghi, Massimo; Cantore, Giuseppe; Milani, Massimo
abstract

In questo lavoro sono presentati e discussi i risultati ottenuti da una serie di rilievi sperimentali volti alla misura della pressione nei vani di una pompa a palette di produzione industriale.Le prove, effettuate in diverse condizioni di funzionamento della macchina, evidenziano alcune singolarita' originate probabilmente dal recupero dei giochi da parte delle palette; tali fenomeni si manifestano in prossimita' delle zone di commutazione, laddove la pressione inizia ad aumentare o a diminuire.Vengono inoltre presentati i risultati di un modello di calcolo semplificato, basato sull'applicazione dell'equazione di continuita' ai vani della macchina.Il confronto fra i risultati forniti dal calcolo e quelli sperimentali si mostra incoraggiante nelle sue linee generali, nonostante la semplicita' del modello. Vengono fornite indicazioni per l'ulteriore miglioramento della modellizzazione.


1997 - Experimental and Numerical Analysis of Forces on a Hydraulic Distributor [Relazione in Atti di Convegno]
Borghi, Massimo; Cantore, Giuseppe; Milani, Massimo; R., Paoluzzi
abstract

The paper relates about experiments and Computational Fluid Dynamics (CFD) analysis on forces acting on a commerci al 4/3 distributor. Experimental results are reported, together with a detailed discussion to asses their reliability. The same results are then used to drive the approach to numerical simulation, in order to minimise the number of runs needed to gather the required informations in term of pressure drop and spool forces.A description of the benefits achievable with an extensive use of dimensional analysis is presented, showing how, within the validity limits of the same set of equations (turbulent or laminar), non-dimensional results of a numerical computation can be consistently extended to various flow conditions. Some final considerations are then reserved to a few indications useful for valve geometry improvement; furthermore a discussion is reported about some controversial numerical and experimental results.


1997 - L'impiego dei coefficienti di efflusso nelle simulazioni del ciclo dei motori alternativi a combustione interna (The use of discharge coefficients in thermo-fluid-dynamic numerical simulation of reciprocating internal combustion engines) [Relazione in Atti di Convegno]
Cantore, Giuseppe; Mattarelli, Enrico; Borghi, Massimo; A. A., Boretti; G., Guerrini
abstract

II progetto e lo sviluppo di motori ad alte prestazioni trova un valido supporto nelle simulazioni termofluidodinamiche del ciclo. Tali simulazioni consentono sia di studiare l'evoluzione temporale delle principali grandezze termodinarniche e di flusso nel motore, sia di prevedere le caratteristiche prestazionali del motore stesso. L'accuratezza dei risultati di queste simulazioni è estremamente importante ai fini di una loro applicazione sistematica in ambito industriale. In questo lavoro vengono discussi alcuni aspetti inerenti la modellizzazione del flusso attraverso i condotti e le valvole dei motori, allo scopo di migliorare le capacità predittivedella simulazione numerica, mediante un uso critico dei dati sperimentali. Si è osservato che, per le consuete modalità con cui si effettuano le prove di flussaggio stazionario delle valvole, è talvolta necessario correggere il valore dei coefficienti di efilusso da introdurre nella simulazione. Vengono allo scopo proposte alcune relazioni dedotte per via teorica, da integrarsi con i risultati di un'analisi numerica tridimensionale, o di ulteriori provesperimentali.L'influenza delle correzioni proposte, e le relative conseguenze sui risultati della simulazione di ciclo, sono state valutate con riferimento al caso di un motore Ferrari per laFormula 1. E' risultato che le entità delle correzioni al coefficiente di efilusso sono in alcuni casi significative, raggiungendo anche il 25%. Sensibili, anche se decisamente meno rilevanti, sono le differenze che si riscontrano per i risultati della simulazione in termini di prestazioni globali del motore.


1997 - Multidimensional Modeling of In-Cylinder Flows and Combustion of a Four Valve S.I. Competition Engine [Relazione in Atti di Convegno]
Cantore, Giuseppe; G. M., Bianchi; G., Guerrini; F., Papetti
abstract

n.d.


1997 - Pressure balancing in external gear pumps and motors[Bilanciamento delle macchine oleodinamiche a ingranaggi esterni] [Articolo su rivista]
Cantore, Giuseppe; Milani, Massimo; Borghi, Massimo
abstract

The paper relates on a numerical method for designing balancing bearing block areas for external gear pumps and motors. At first, a way is presented for obtaining pressure distribution inside spaces between teeth, bearing blocks and casing; the procedure, based on integration of the continuity equation for sealed spaces, permits also the evaluation of some interesting aspects dealing with the influence of rotational speed, dynamic viscosity and gears eccentricity. Then, a method is presented for calculating pressure distribution in the layer bounded by gears sides and bearing blocks. The method, starting from pressure distribution in spaces, is based on the integration of the laspace equation over the whole layer. Axial thrust on bearing blocks and its point of application are then calculated. Finally, the same problem is analysed with a simplified numerical approach, as well based on the integration of the laplace equation, but on the small portion of the layer corresponding to one tooth, with only one boundary condition. At the end, calculations are made for a commercial pump, obtaining balancing aeras very close to the ones designed by the manufacturer.


1997 - Sperimentazione con Fluidodinamica Computazionale di un Distributore Oleodinamico [Articolo su rivista]
Borghi, Massimo; Cantore, Giuseppe; Milani, Massimo; R., Paoluzzi
abstract

La memoria si occupa della riprogettazione di un distributore oleodinamico di tipo on-off mediante l'utilizzo di strumenti di progettazione assistita da calcolatore, sottolineando quali aspetti progettuali debbano essere considerati per ridurre l'effetto delle forze di flusso assiali.


1996 - Computational Methods for the Fluid Dynamic Optimization of High-Performance Engines [Relazione in Atti di Convegno]
Cantore, Giuseppe; A. A., Boretti; Mattarelli, Enrico; Borghi, Massimo
abstract

n.d.


1996 - Experimental and Computational Analysis of a High Performance Motorcycle Engine [Relazione in Atti di Convegno]
Cantore, Giuseppe; A. A., Boretti; Mattarelli, Enrico; F., Preziosi
abstract

A high performance, motorcycle engine is analyzed by using integrated experimental and computational methods. Test bench experiments provide a few gross engine performance parameters. Dynamic simulations provide gross engine performance parameters and a detailed description of basic phenomena. Modelling guidelines are briefly reviewed. The accuracy of the model is finally assessed through comparison of experimental and computational gross engine performance parameters.


1996 - Fluido contaminato? No grazie! [Articolo su rivista]
Cantore, Giuseppe; Borghi, Massimo; Milani, Massimo; M., Bianchi
abstract

n.d.


1996 - Modellizzazione numerica del processo di combustione in motori ad accensione comandata con codice CRI-TurboKIVA 2.2 [Relazione in Atti di Convegno]
G. M., Bianchi; A. A., Boretti; Cantore, Giuseppe; P., Casoli; Mattarelli, Enrico
abstract

Questo studio si inserisce nell'ambito di un'attivita` di ricerca in corso gia` da qualche anno in collaborazione con la Ferrari Auto ed avente come tema la simulazione numerica con il codice CRI/TurboKiva 2.2 del processo di combustione in motori ad accensione comandata ad elevate prestazioni. In particolare, questo lavoro mira alla valutazione delle capacita` predittive di CRI/TurboKiva nell'analisi dell'influenza esercitata dai moti di tumble e di swirl sulla velocita` di combustione. Il comportamento del modello di combustione e` stato testato a due differenti regimi di rotazione del motore. I risultati numerici, in termini di ciclo di pressione e di legge di rilascio calore, si sono mostrati in ottimo accordo con i corrispondenti andamenti sperimentali in entrambe le condizioni di funzionamento considerate. La risposta del codice a variazioni dei rapporti iniziali di tumble e swirl e` risultata qualitativamente corretta solo nel caso dei moti di tumble mentre altrettanto non e` accaduto nel caso di moti sovrapposti di tumble e di swirl. Tale anomalia sembra riconducibile soprattutto a problemi di accuratezza numerica, all'adozione del modello k-e a turbolenza isotropa ed alle ipotesi semplificative utilizzate nella definizione del campo di moto iniziale medio e turbolento.


1996 - Numerical optimization of a racing engine with variable intake and exhaust geometry and valve actuation [Relazione in Atti di Convegno]
A. A., Boretti; Borghi, Massimo; Cantore, Giuseppe; Mattarelli, Enrico
abstract

This paper presents a numerical study on a racing engine with variable intake and exhaust geometry and valve actuation. The study is carried out by using dynamic engine simulations. Aim of the analysis is the evaluation of the benefits these devices have on engine performance. Results show clear advantages over the full range of engine speed.


1995 - Experimental and Computational Methods for Swirl Port Design in Internal Combustion Engines [Relazione in Atti di Convegno]
A. A., Boretti; Cantore, Giuseppe; Borghi, Massimo; Mattarelli, Enrico
abstract

The paper reviews the minimum losses and intake flow conditioning criteria typically adopted for the design of swirl ports in two valve Direct Injection (DI) Diesel engines, as well as in some two valve Spark Ignition (SI) engines. The standard experimental practice, based on the use of steady flow discharge and swirl coefficients as a measure of port design quality is first presented. The analogous computational methodology, where the steady flow is simulated, is then introduced. The computational methodology is extensively validated against a data set for a series of ports, of the direct, hybrid and helical type. The computational methodology is finally applied to simulate the transient flow within the engine during the intake stroke. The computed Intake Valve Closure (IVC) flow field provides a more rational basis for port optimization than steady flow coefficients, even if these latter simulations have still to be properly validated.


1995 - Numerical Simulation of Turbulent Combustion in a Four Valve Spark Ignition Engine with CRI/Turbokiva 2.0 Code [Relazione in Atti di Convegno]
Cantore, Giuseppe; Borghi, Massimo; Mattarelli, Enrico; G. M., Bianchi; A. A., Boretti; L., Chinni
abstract

An enhanced engineering version of the Los Alamos National Laboratory's Kiva 3 code, called CRI/Turbokiva 2.0, was applied to the study of the mean and turbulent flow field evolution during compression and combustion in a spark ignition engine. A kinetically influenced turbulent combustion model was formulated to overcome the limitations of the standard turbulent combustion model. Mean velocity, turbulence intensity and turbulent length scale results are presented and compared with experimental data, providing satisfactory agreement. These comparisons provide a proper validation work for the fluid dynamic and combustion parts of the code.


1995 - Simulazione numerica del processo di combustione in motori ad elevate prestazioni con codice di calcolo tridimensionale [Relazione in Atti di Convegno]
Cantore, Giuseppe; G. M., Bianchi; A., Dominici; A., Boretti
abstract

n.d.


1994 - Cogenerative combined cycle power plants fueled by coal and biomass gas [Relazione in Atti di Convegno]
Borghi, Massimo; Cantore, Giuseppe; A., Peretto; P. R., Spina
abstract

This paper proposes a system made-up by a Lurgi fixed-bed gasifier fed with coal or biomass and by a dual pressure level gas-steam combined cycle power plant in cogenerative application. Some comparisons among different configuration plants with single or double intercooled compression gas turbine are carried-out. In this analysis gas turbine off-design operating conditions, due to the use of low-medium Lower Heating Value coal or biomass gas fuel, are pointed-out. A constrained minimization algorithm is used for solving simultaneously all equations describing the system (included the ones representing energy balances and chemical equilibrium in the gasifier) to calculate the integrated plant performance. Results show that the proposed plant can work with energy conversion efficiency not much lower than the one obtainable when the gas turbine is fed with methane, that is the fuel for which the gas turbine itself was designed. Nevertheless, increases up to 15% in both electrical and thermal power are evaluated.


1994 - Computational analysis with Turbokiva code on multivalves spark ignition engine performance [Relazione in Atti di Convegno]
Cantore, Giuseppe; Borghi, Massimo; L., Chinni; Mattarelli, Enrico; A., Dominici; L., Marmorini; P., Martinelli
abstract

n.d.


1994 - Numerical Correlation of Combustion Evolution and Port and Combustion Chamber Shape in a High Speed, Four Valve, Spark Ignition Engine [Relazione in Atti di Convegno]
A. A., Boretti; Cantore, Giuseppe; Mattarelli, Enrico
abstract

The paper presents the results of a CFD 1D and 3D analysis carried out on a high speed 4 valve 4-Stroke engine.


1994 - Numerical Study of Volumetric Efficiencies in a High Speed, Four Valve, Four Cylinder, Spark Ignition Engine [Relazione in Atti di Convegno]
A. A., Boretti; Borghi, Massimo; Cantore, Giuseppe
abstract

High power output, four stroke, motorcycle engines are characterised by specific power levels well beyond 150 HPllitre also in production engines. These power levels are obtained through extremely high values of volumetric efficiencies in tbe range of high engine speed, resulting from highly optimised gas exchange processes. In the present paper, a four cylinder, four valve per cylinder engine with a four-in-one exhaust is optimised for volumetric efficiencies by using state-of-the-artcomputational methods. These computational metbods include stati c three dimensional computations as well as dynamic one and three dimensional computations. The engine geornetric and operating parameters optimised by using these computations agree fairly well with those optimised by using experiments, thus demonstrating the effectiveness of the proposed computational practice.


1993 - Analisi exergetica di sistemi integrati con turbina a gas e sorgente geotermica [Relazione in Atti di Convegno]
Cantore, Giuseppe; G., Negri di Montenegro; A., Peretto
abstract

n.d.


1993 - Combined Cycle Power Plants from Gas Turbines and Geothermal Source Integration [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi; E., Gadda; G., Negri di Montenegro; A., Peretto
abstract

Geothermal power plants have difficulties due to the low conversion efficiencies achievable. geothermal integrated combined cycle proposed and analyzed in this paper is a way to achieve high efficiency. In the proposed cycle the geothermal fluid energy is added, through suitable heat exchangers, to that of exhaust gases for generating a steam cycle. The proposed cycle maintains the geothermal fluid segregated from ambient and these can be positive on the environmental point of view. Many systems configurations, based on this possibility, can be taken into account to get the best thermodynamic result. The performed analysis examines different possible sharings between the heat coming from geothermal and exhaust gases, and gives the resulting system efficiencies. Various pressures of the geothermal steam and water dominated sources are also taken into account. As a result the analysis shows that the integrated plant power output is largely greater than the total power obtained by summing the gas turbine and the traditional geothermal plant power output, considered separately.


1993 - Gas Turbine Cycle Modeling Oriented to Component Performance Evaluation from Limited Design or test Data [Relazione in Atti di Convegno]
Cantore, Giuseppe; E., Benvenuti; R., Bettocchi; G., Negri di Montenegro; P. R., Spina
abstract

This paper describes the first phase of a study aimed at setting - up a cycle model and computer program for evaluating the performance of gas turbine components having only a limited amount of data available. In this study the mathematical models of the individual components, the iterative solution algorithms and the main code blocks were set-up. To achieve a solution a simultaneous method, consisting of a constrained optimization algorithm, is utilized. A preliminary evaluation of the ranges in which parameters can vary was necessary to calibrate the method; it consisted of a sensitivity analysis made with a version of the code that employs a sequential solution method. The code may be utilized either to identify the causes of performance deviations from design values or to perform comparative analyses of gas turbine cycles when few specific design data are available. In the latter case a statistical data base for each class of machine analysed is needed as input. A future paper will present the results of work currently in progress, involving application of the code to a number of turbines, for which detail design data are available, in order to check the simultaneous solution method for a variety of machines and operating conditions.


1993 - Prestazioni di pompe ad ingranaggi per motori a carter secco in presenza di miscele olio-aria [Relazione in Atti di Convegno]
Borghi, Massimo; Cantore, Giuseppe; L., Mosele
abstract

Si riferisce sui risultati di una prima serie di rilievi sperimentali volti a determinare le prestazioni di pompe ad ingranaggi per la lubrificazione di motori automobilistici ad elevate prestazioni a carter secco. In particolare viene evidenziata l'influenza della presenza di aria nella miscela con l'olio sulla portata destinata alla lubrificazione del motore. In questa prima fase della ricerca è stato appositamente studiato e realizzato un banco prova nel quale si vuole simulare il funzionamento del gruppo di lubrificazione nel motore, utilizzando i reali componenti del circuito. Si è anche studiata l'influenza del serbatoio-separatore e del posizionamento del radiatore olio sulle prestazioni di queste pompe.


1993 - Sulla simulazione del ciclo di piccoli motori diesel funzionanti con miscele gassose artificiali [Relazione in Atti di Convegno]
Borghi, Massimo; A., Brighenti; Cantore, Giuseppe; P., Osti
abstract

In questo lavoro viene rielaborato un modello di simulazione del ciclo di motori Diesel ad iniezione diretta, precedentemente studiato dagli autori. Cio' e' stato possibile grazie alla disponibilita' di una serie di dati sperimentali relativi a piu' motori appartenenti ad una stessa famiglia e funzionanti con aria. Il modello e' stato modificato rispetto alla versione precedente e calibrato in maniera piu' accurata per renderlo adatto a prevedere le prestazioni dell'intera famiglia di motori considerata in un piu' ampio campo di condizioni operative. Viene riportato inoltre un confronto fra i risultati ottenuti utilizzando per la simulazione due diversi modelli fenomenologici di combustione a singola zona. Lo scopo di questa fase della ricerca e' quello di utilizzare il modello per confrontare le prestazioni di motori costruiti per funzionare in aria, quando, con o senza modifiche, siano alimentati con miscele gassose artificiali come per esempio ossigeno ed anidride carbonica, con o senza argon. In questo lavoro si presenta l'influenza della concentrazione di argon, a percentuale di ossigeno costante, nella parte inerte della suddetta miscela ternaria, senza modificare la geometria del motore. In particolare si e' evidenziato che una percentuale di circa il 60% del gas inerte deve contenere un gas monoatomico come l'argon, essendo la restante parte costituita da anidride carbonica, se si vogliono ottenere diagrammi pressione - angolo di manovella e lavori indicati vicini a quelli trovati con il modello applicato al motore funzionante ad aria.


1992 - Analisi comparativa di sistemi energetici integrati con sorgente geotermica [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi; E., Gadda; G., Negri di Montenegro; A., Peretto
abstract

Nel presente lavoro si sono studiati sistemi energetici integrati con sorgente geotermica, derivati da impianti a combustibile fossile tradizionali quali turbine a gas e impianti a vapore a ciclo rigenerativo e dai più recenti impianti a ciclo combinato gas-vapore. Viene eseguita un'analisi comparativa sulla base delle variazioni di potenza conseguenti all'integrazione e del rendimento globale di conversione del sistema integrato. I risultati dello studio portano a concludere che sistemi integrati derivati da turbine a gas hanno incrementi di potenza più elevati ma più bassi valori del rendimento, mentre quelli derivati da impianti combinati forniscono più elevati rendimenti con più bassi incrementi di potenza. meno interessanti risultano invece i sistemi integrati derivati da impianti a vapore a spillamenti che possono risultare utilizzabili per sorgenti geotermiche di basso livello entalpico.


1992 - Combustion Model of IDI Diesel Engine [Relazione in Atti di Convegno]
Cantore, Giuseppe; M., Feola; P., Pelloni; G., Bella; P., Casoli; G., Toderi
abstract

This paper describes a simulation model of a naturally aspirated four stroke diesel engine with a swirl prechamber. The study was carried out use a "two-zone" thermodynamic in both chambers model as regards the closed valves phase and "filling-emptying" one as regards the open valves phase. The capability of the previously described model to predict the pressure cycle as well as polluting emissions of a I.D.I. engine was verified by comparing experimental and evaluated data. Comparison between the result yielded by the model and experimentals ones shown the model good predictive capability as regards indicated pressure cycle nitric oxide and soot productions.


1992 - Influenza della compressione frazionata e della ricombustione in cicli Stig in versione bialbero [Relazione in Atti di Convegno]
Cantore, Giuseppe; P., Casoli; A., Peretto; G., Toderi
abstract

Nel presente lavoro si esaminano dapprima le prestazioni di turbine a gas con compressione frazionata interrefrigerata, funzionanti con ciclo STIG. Viene in particolare considerata una versione bialbero valutando l'influenza sulle prestazioni della quantità di vapore iniettata in camera di combustione. Successivamente viene svolta un'analisi sull'influenza della ricombustione sulle prestazioni delle tipologie di macchine prima esaminate per valutare se esiste interesse che giustifichi questa complicazione impiantistica.


1992 - Integrated Design and Testing Methodology for High - Performance Vehicle Thermal Systems [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Fedeli; G., Molinari
abstract

The paper describes the methodology studied and developed at Ferrari in order to establish an integrated design and testing procedure of the vehicle's cooling system (water, oil, air conditioning). Some experimental results obtained in the engine test room and in the wind tunnel with reference to engine thermal balance and external flow dynamics, are presented and discussed. Heat exchanges in the air conditioning and engine cooling system depend on the components layout by means of influence factors. These were related to the layout chosen, on the basis of correlation laws derived from experimental analyses.


1992 - Optimization of Injection Law for a D.I. Diesel Engine [Articolo su rivista]
Cantore, Giuseppe; M., Feola; P., Pelloni; G., Bella; P., Casoli; G., Toderi
abstract

This paper describes how different timing and shape of the injection law can influence pollutant emission of a direct injection diesel engine. The study was carried out making use of a multizone thermodynamic model as regards the closed valve phase, and a filling-emptying one as regards the open valve phase. After being calibrated by comparison with experimental data, the abovementioned model was used for injection law optimization as regards minimum pollutant concentration (NO[sub x] and soot) in the exhaust gases with the smallest engine performance reduction possible.


1992 - Simulazione del ciclo reale di un motore diesel alimentato con miscele gassose artificiali [Relazione in Atti di Convegno]
Cantore, Giuseppe; A., Brighenti; P., Osti
abstract

Lo studio che si presenta in questo lavoro si pone l'obiettivo di valutare le prestazioni e individuare l'andamento delle pressioni in un motore alimentato cin miscele gassose artificiali, con elevato tenore di CO2. Le diverse caratteristiche termodinamiche e di trasporto della CO2 rispetto agli inerti biatomici presenti normalmente in un motore Diesel atmosferico rendono necessaria l'adozione di alcune modifiche, insieme o in alternativa fra loro, per consentire di adattare un motore commerciale alla diversa alimentazione.


1992 - Simulazione della fase di combustione in motori diesel ad iniezione diretta [Relazione in Atti di Convegno]
Cantore, Giuseppe; M., Feola; P., Pelloni; G., Bella; P., Casoli; G., Toderi
abstract

Nel presente lavoro vengono analizzati due diversi modelli di simulazione del fenomeno di combustione in motori Diesel ad iniezione diretta; il primo è un modello fenomenologico di tipo multi-zone, il secondo è il modello fluidodinamico Kiva-II che risolve in un dominio tridimensionale l'equazione di Navier-Stokes per un fluido comprimibile turbolento e reagente in condizioni instazionarie. L'analisi consiste nel valutare le capacità predittive dei modelli evidenziandone l'opportunità di impiego, in relazione alle loro prestazioni.


1992 - Sistema di acquisizione e controllo per la mappatura automatica di motori ad iniezione elettronica [Articolo su rivista]
Cantore, Giuseppe; C., Galletti
abstract

In questo lavoro viene presentato un sistema di acquisizione e controllo per la mappatura automatica di un motore ad iniezione elettronica destinato ad equipaggiare una vettura stradale ad elevate prestazioni. In sistema, studiato avvalendosi delle attrezzature disponibili in sala prove, è stato realizzato per interagire con l'iniezione elettronica installata sul motore. Uno degli aspetti innovativi della realizzazione consiste nell'aver fornito il sistema di routine che, utilizzando le misure effettuate a regimi stazionari, sono in grado di svolgere automaticamente i relativi interventi sull'iniezione, atti a costruire le mappe del tempo di erogazione e dell'anticipo su cui il sistema ALFA-N si basa. Il sistema è in grado di generare file contenenti i risultati della sezione di prova, di graficarli oppure di tabularli; risulta di facile impiego e consente di ottenere buone messe a punto del motore grazie alle routine di mappatura automatica che si sono rilevate rapide a precise.


1992 - Sistema di Climatizzazione per Autoveicoli con Riscaldamento a Compressione di Gas [Articolo su rivista]
Cantore, Giuseppe; R., Grotti; R., Marchetti
abstract

Il sistema di climatizzazione con riscaldamento a compressione di gas che viene presentato in questo lavoro è stato realizzato nell'ambito delle ricerche sperimentali che si svolgono in collaborazione tra il reparto ricerca e sviluppo della Diavia S.r.l. e l'Istituto di Macchine della Facoltà di Ingegneria dell'Università di Bologna. Con il sistema proposto si intende ottenere dai climatizzatori per autoveicoli la capacità di fornire una fonte di calore immediatamente disponibile all'atto dell'avviamento a freddo del motore. Nella realizzazione si è cercato, per quanto possibile, di usare componenti standard di impianti di climatizzazione per autoveicoli. Il sistema è stato provato in diverse condizioni di funzionamento al fine di valutarne le prestazioni e di verificarne l'affidabilità.


1992 - Study, Development and Construction of a HVAC System for Monospace Vehicle [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Grotti; P., Lotti
abstract

This paper relates to innovative solutions for a new HVAC system to be placed on the concept car Scenic produced by Renault. The components characteristics definition and fitting have been carried out with reference to the particular vehicle structure and thermal requirements. First the HVAC system has been installed on a vehicle as similar as possible to the actual one. This vehicle has been tested in the climatic room to define performances. At the second stage all the system components have been integrated in the Scenic prototype during the development. The presence of two different units in the HVAC system has imposed the study of a sophisticated control system able to manage air distribution and temperature.


1992 - Thermodynamic and Economic Analysis on Geothermal Integrated Combined-Cycle Power Plants [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi; E., Gadda; G., Negri di Montenegro
abstract

The paper considers geothermal integrated power plants obtained matching a geothermal plant with, a two pressure level combined plant. The purpose of the paper is the evaluation of thermodynamic and economic aspect on geothermal integrated combined-cycle power plant and a comparison with conventional solutions. The results show that the integrated combined plant power is greater than the sum of combined cycle and geothermal plant powers considered separately and that the integrated plant can offer economic benefits reaching the 16% of the total capital required.


1991 - Analisi comparativa di cicli STIG complessi [Relazione in Atti di Convegno]
Cantore, Giuseppe; P., Casoli; G., Toderi
abstract

In questo studio sono state valutate le prestazioni di alcune fattispecie industriali di turbine a gas nell'ipotesi di funzionamento in ciclo STIG con compressione frazionata interrefrigerata. le fattispecie industriali considerate sono quelle classiche, denominate small-size, heavy-duty e aeroderivate. E' stato messo a punto un modello di calcolo che deriva da un altro precedentemente realizzato per turbine a gas con compressione frazionata interrefrigerata e che è stato modificato per tenere conto del funzionamento off-design conseguente all'iniezione di vapore.


1991 - Gruppi combinati con turbina a gas interrefrigerata [Relazione in Atti di Convegno]
Cantore, Giuseppe; P., Azzoni; R., Bettocchi; D., Moro
abstract

n.d.


1991 - Gruppo combinato con integrazione geotermica [Relazione in Atti di Convegno]
Cantore, Giuseppe; E., Gadda; G., Negri di Montenegro
abstract

In questo lavoro viene studiata l'integrazione di un impianto di potenza a ciclo combinato gas-vapore con una sorgente geotermica. Si sono esaminate le variazioni di rendimento e di potenza ottenibili sia dal ciclo combinato integrato sia dalla sola sezione a vapore al variare della potenza termica fornita dalla sorgente geotermica e dalla temperatura di surriscaldamento del vapore di bassa pressione.


1991 - Off-Design Evaluation of a Multiple Expansion Reheating Gas Turbine in Cogeneration Applications [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi; E., Benvenuti; G., Negri di Montenegro
abstract

The multiple expansion reheating gas turbine proves to have a potential of good operational flexibility for the intrinsic capability of responding to variations in electric and thermal power demands without appreciable impact on efficiency. The present study deals with evaluation of the performance attainable in off-design operation, with power control obtained through changes in the first and second combustor firing temperatures and in the compressor intake air flow achieved by means of variable inlet guide vanes.


1991 - Optimum Performance Evaluation in Multistage Intercooled Compression Gas Turbines [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi; G., Negri di Montenegro; D., Moro
abstract

Multistage intercooled compression in gas turbines is nowdays increasingly interesting because it is due to the ever higher firing temperature values, which call for more effective cooling of the most thermally stressed parts. A part from a decrease in the compression work, intercooled compression causes an increase in the cooling action due to lower temperature values at the compressor aoutlet.


1991 - Simulazione dinamica di un sistema con motore Diesel a ciclo chiuso e liquefazione criogenica dei gas di scarico [Relazione in Atti di Convegno]
Cantore, Giuseppe; A., Brighenti; A., Dalla Rosa; P., Osti
abstract

Si descrive e si discute l'architettura, il funzionamento, il modello e le prestazioni in regime variabile di un sistema con motore Diesel a ciclo chiuso in cui l'eccesso dei gas di scarico prodotto dalla combustione, specificamente l'anidride carbonica, viene separato e stoccato dopo liquefazione criogenica. Questa avviene per l'evaporazione di ossigeno liquido, utilizzato per il reintegro del potere comburente della miscela che alimenta il motore. Viene messa in evidenza l'azione autoregolante del sistema sul tenore di ossigeno, dovuta alla variazione della pressione di aspirazione del motore al variare della sua velocità, che si affianca positivamente all'azione del sistema di controllo.


1991 - The Cryo-Thermal Closed Cycle Diesel Engine. Detailed Analysis of Stationary Working Conditions [Relazione in Atti di Convegno]
Cantore, Giuseppe; A., Brighenti; P., Osti
abstract

The "cryothermal engine" is a closed cycle Diesel system in which exhaust gases are cooled and part of them compressed so that CO2 is condensed, separated and stored at low temperature, thanks to heat exchange with stored liquid oxygen. This generates a cooling effect while is evaporated and superheated to feed the inlet mixtures of the engine. The system, petented in a number of countries, was presented in a previous paper where the main differences and advantages were shown with respect to other energy system for Autonomous Underwater Vehicles (AUV). Basic thermodynamics and performances of the plant were presented and discussed, highlighting the high degree of system's non linearity.


1990 - Collaudo automatico di pompe oleoidrauliche in condizioni estreme [Articolo su rivista]
Cantore, Giuseppe; G., Minelli; R., Bettocchi
abstract

Un sistema per il collaudo di pompe oleoidrauliche con acquisizione automatica e restituzione istantanea delle prestazioni con lo scopo precipuo di dare con immediatezza allo'operatore la percezione se si sta spingendo a condizioni di funzionamento inaccettabili per la macchina che così può essere collaudata in un più ampio campo, senza rischi di danneggiamenti.


1990 - Comparative Analysis of STIG Cycles and Postcombustion Influence [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi; P. E., Laudi; G., Negri di Montenegro
abstract

A methodology to evaluate the performances of STIG cycles has been carried out in this study, based on remarkable parameters such as steam injected fraction, gas and steam specific work and their respective heat amounts supplied in the combustor. The survey has been carried out on two different kind of gas turbines: heavy duty and aeroderivative gas turbines. Suitable amounts of cooling air with regard to the various kinds of gas turbines have been calculated. The results achieved with the proposed methodology agree with the data put forth in the literature on the subject and are a reference for more complex STIG cycles such as the postcombustion case. In the latter case the postcombustion has not proved convenient for STIG cyclesm as regards efficiency, but it involves benefits as greater maximum powers are obtainable.


1990 - Experimental Analysis on Swirling Flow and Performance of Bent Diffuser Ducts [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi; D., Moro
abstract

This study refers to an experimental analysis on swirling flow in some shapes of bent diffuser ducts. The study has been carried out for the purposes of investigating the correlation between the rotational intensity of the flow, the main geometrical characteristics of the diffusers and their performance. The cases of a cone, a costant section elbow followed by the previous cone, and a duct obtained by combining the latter with another cone positioned upstream have been studied. It has been seen that an appropriate value for the rotational intensity of the flow, which is not a particularly high value, in all the types studied, determines the advantage in the pressure recovery coefficient. When, on the other hand, the rotational intensity assumes higher values, a considerable reduction in the coefficient itself is experienced.


1990 - Flusso vorticoso in un modello di canale curvo diffondente [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi; D., Moro
abstract

Nel lavoro si presenta l'analisi sperimentale sul flusso vorticoso in un condotto costituito da un cono, una curva a 90° a sezione costante e un altro cono, condotto che vuole rappresentare una forma semplificata di un canale curvo diffondente del tipo di quelli installati allo scarico delle turbine idrauliche a reazione. Per un'analisi dettagliata sull'evoluzione del flusso nel condotto e per la valutazione dell'influenza dell'intensità di rotazione della vena si sono rilevati sperimentalmente, in diverse sezioni, i profili delle pressioni e delle velocità. L'analisi effettuata consente di valutare le prestazioni del condotto e di interpretare l'influenza su di esse dell'intensità di rotazione del flusso. In particolare si sono studiate le variazioni del coefficiente di recupero della pressione e del rendimento di conversione. Il confronto con altre geometrie precedentemente analizzate ha permesso di mettere in luce l'efficacia della diffusione dovuta al cono disposto a monte della curva.


1990 - Multiple Expansion Reheating Gas Turbine for Cogeneration Plants [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi; P. M., Pellò; G., Negri di Montenegro
abstract

The following is a study of the feasibility of a cogeneration system characterized by a power unit with a multiple expansion reheating gas turbine. The "limit" specific cost of investment, calculated on the assumption of a non-profit making situation, of the additional electrical power obtainable in relation to the solution under reference, has been used to evaluate the financial advantage of the system. The limit value, within a defined list of tariff rates, will depend substantially on electrical efficiency which, in turn, will be affected by the quality of heat recovery, the degree of recombustion and the coefficient of heat itilization. The numerical results of the study show that, even in the unfavourable cases examined, these limit values for specific investment cost are sufficiently high to make them profitable against the likely industrial costs of a significantly large production series.


1989 - Prospettive di impiego di turbine a gas con espansione frazionata interriscaldata per la cogenerazione [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi; G., Negri di Montenegro; P. M., Pellò
abstract

n.d.


1989 - Sistema di acquisizione automatica ed elaborazione dati per misure con sonde di pressione [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi
abstract

Il sistema di acquisizione automatica ed elaborazione dati che viene presentato in questo lavoro è stato realizzato nell'ambito delle ricerche sperimentali che gli autori svolgono, presso il laboratorio dell'Istituto di Macchine dell'Università di Bologna, sul flusso nei condotti delle macchine. Nel lavoro si fa riferimento al caso in cui le misure per la determinazione dei profili di pressione e di velocità, necessarie per lo studio del flusso, siano effettuate utilizzando sonde tridimensionali di pressione di tipo commerciale, ma il sistema può essere impiegato in una generalità di casi pratici che prevedono l'impiego di qualunque tipo di sonda di pressione purchè si disponga delle curve di taratura.


1989 - The Cooling Air Influence on the Performance of the Gas-Steam Combined Cycle Power Plants with Multiple Expansion Reheating Gas Turbine [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi; G., Negri di Montenegro; G., Vincenzi
abstract

The performance of gas-steam combined cycle power plants with multiple expansion reheating gas turbine, are studied considering the influence of the cooling air necessary to the most thermically stressed topper devices. The influence of various maximum quantities of the cooling air have been examined and it has been observed that, in all case, a small range of intermediate pressures exists making combined plant maximum efficiency. Beside it followed that, even considering the most severe conditions for the cooling air, efficiencies are greater (two or three points about) than those of combined plants with Brayton cycle gas turbine. The values of the power ratio between the gas turbine and the steam section are low so that relatively high power combined plants can be realized.


1988 - A comparative study on the ways of converting steam power plants to steam-gas combined cycle power plants [Relazione in Atti di Convegno]
G., Negri Di Montenegro; R., Bettocchi; Cantore, Giuseppe; Borghi, Massimo; G., Naldi
abstract

The authors consider gas-steam combined cycle power plants derived from existing steam power plants by inserting a Brayton cycle gas turbine as a topper. The conversion of superheated, superheated-reheated and regenerative steam cycle power plants is examined. Two methods of conversion are studied: replacing the original steam generator with a recovery boiler either with afterburning at the gas turbine exhaust or not, and keeping the steam generator of the working steam plant in operation and burning fuel inside the gas turbine exhaust gases. In the latter instance the possibility of adding external air, through the steam generator air preheater, to the gas turbine exhaust gases is considered too. The combined overall power plant efficiency and the gas-to-steam-power ratio are evaluated and a comparison is made between the values obtained for the two methods. The overall efficiency is also compared with that of the original working steam plant. The study shows that maximum overall efficiencies are attained when adopting a recovery boiler and that the afterburning at the gas-turbine exhaust is not always advantageous.


1988 - Analisi comparativa fra cicli combinati gas-vapore con e senza post-combustione [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi; A., Galletti; R., Gusso; G., Negri di Montenegro
abstract

n.d.


1988 - Analisi sperimentale del flusso in un condotto curva-diffusore in presenza di componenti rotatorie di velocità [Relazione in Atti di Convegno]
Cantore, Giuseppe
abstract

Sono stati eseguiti rilievi sperimentali per la determinazione dei profili di velocità e di pressione in diverse sezioni di un condotto costituito da una curva a 90° e da un diffusore conico con angolo di apertura 12°. In questo studio si presenta un'analisi del flusso all'interno del condotto in prova eseguita sulla base delle misure effettuate sia nel caso di corrente uniforme che di flusso con componenti rotatorie di velocità. In particolare si è valutata l'influenza che le componenti rotatorie di velocità hanno sull'instaurarsi di fenomeni di separazione nelle zone a valle della curva, constatando che quando il valore di tali componenti supera una certa entità la separazione tende a scomparire.


1988 - Modello interpretativo del comportamento di valvole di sicurezza [Articolo su rivista]
Cantore, Giuseppe; G., Minelli; R., Bettocchi; Borghi, Massimo; G., Naldi
abstract

Le prestazioni operative di una valvola di sicurezza sono tanto più brillanti quanto minori sono, per una data portata effluente, la sovrapressione di apertura e lo scarto di chiusura. A tal scopo, lo studio qui presentato consente di individuare la configurazione più opportuna di dette valvole.


1988 - Performance Levels Obtainable from Steam-Gas Turbine Combined Cycles [Relazione in Atti di Convegno]
Cantore, Giuseppe; G., Negri di Montenegro; R., Bettocchi; G., Naldi
abstract

This study aims to the evaluation of the best performance obtainable from a steam-gas turbine combined plants both in a new plant design and in improving existing steam plants by adding a topping gas turbine system. A method of comparison is presented here, based on the choice of a steam-gas reference cycle which has shown to be particularly suitable for a general study. A thermodynamic analysis has been carried out showing the influence on the combined plant overall efficiency of the parameters characterizing both the gas and steam cycles. The reference cycle as well as those derivable from it by modifying the gas portion cycle only has been studied. The analysis was also extended to evuation of the gas to steam units output power ratio and of the efficiency increase when repowering a steam unit. It has been shown that the combined cycle plants maximum overall-efficiency is achieved, whatever the steam cycle, when the gas turbine cycle operates at maximum specific work. The result is that the best performance in combined cycle plants is achieved by using multiple expansion with reheating in the gas cycle, when designing a new plant. When steam plants are to be repowered by means of existing gas turbine units, afterburning may be useful to improve performance.


1988 - Sulla determinazione sperimentale delle prestazioni dei diffusori in presenza di flussi rotanti [Articolo su rivista]
Cantore, Giuseppe; R., Bettocchi; S., Battistini
abstract

La ricerca che si presenta verte sulle modalità di determinazione sperimentale delle prestazioni (coefficiente di recupero della pressione statica e rendimento) dei diffusori: in particolare sono messi a confronto i casi in cui tali prestazioni vengono determinate o utilizzando rilievi di pressione statica alla parete nelle sezioni di ingresso e di uscita del diffusore nonché una misura della portata, oppure attraverso misure di pressione e di velocità effettuate lungo più traverse, nelle stesse sezioni.


1988 - Sull'ottimizzazione di gruppi combinati gas-vapore con sezione a vapore a due pressioni [Relazione in Atti di Convegno]
Cantore, Giuseppe; G., Naldi; S., Sandrolini
abstract

Scopo dello studio è la determinazione dei massimi rendimenti ottenibili dai gruppi combinati gas-vapore costituiti da turbine a gas a ciclo di Brayton e da sezioni a vapore a due livelli di pressione. In linea con le più diffuse realizzazioni industriali nel settore, il vapore di bassa pressione è impiegato allo stato fisico di vapore saturo secco. Lo studio è stato condotto per turbine a gas di attuale e futura generazione considerando, per ciascuna di esse, un campo di rapporti di compressione sufficientemente ampio da contenere tutte le realizzazioni industriali.


1987 - CONVERSION OF STEAM AND GAS POWER PLANTS TO COMBINED CYCLES [Relazione in Atti di Convegno]
G., Negri di Montenegro; R., Bettocchi; Cantore, Giuseppe; Borghi, Massimo; G., Naldi
abstract

This paper studies the repowering of already operating steam or turbogas plants through the fitting of a turbogas unit as topper in the first case, and a steam unit as bottomer in the second, thus obtaining steam-gas combined plants. As to steam plants, a methodology has been defined which permits evaluation of both the overall efficiency and gas to steam power ratio of the derived combined plant obtained by superposing a turbogas unit on any assigned steam plant so as to permit integral utilization or minimum modification of the steam section.


1987 - Conversione di centrali a vapore in gruppi combinati gas-vapore con caldaia a recupero [Relazione in Atti di Convegno]
Cantore, Giuseppe
abstract

n.d.


1986 - A STEAM-GAS COMBINED PLANTS OPTIMIZATION [Relazione in Atti di Convegno]
G., Negri di Montenegro; R., Bettocchi; Cantore, Giuseppe; Borghi, Massimo; G., Naldi
abstract

An optimum-design general criterion for steam-gas combined plants is illustrated by which the characteristics of the gas and steam sections can be established to obtain maximum overall efficiency of the plant. The methodology is based on the choice, as an independent variable of the temperature, of the exhaust gases at the recovery boiler inlet. Consideration is given to gas units operating according to a Brayton cycle, with and without afterburning and in accordance with reheat-gas-turbine cycles, and to steam units realized with superheat, superheat reheat, and extraction- heater steam cycles. It is concluded that in order to obtain high-performance combined plants it is not advisable to adopt particularly complicated steam sections, that is, fitted with regeneration and superheat reheating; it is, on the other hand, desirable to match turbo-gas plants operating according to a multiple expansion with reheating cycles, and steam plants with simple superheating.


1986 - Influenza dell'intensità di rotazione del flusso sulle pulsazioni di pressione in un diffusore conico [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi
abstract

Si sono eseguiti rilievi di pulsazioni di pressione in diverse sezioni disposte lungo l'asse di un diffusore conico per diversi valori dell'intensità di rotazione della vena nella sezione di ingresso. L'analisi dei risultati ed il confronto con quelli ottenuti nello stesso diffusore con flusso puramente assiale consentono di concludere che, in presenza di una corrente vorticosa, si ottiene una "stabilizzazione" del flusso associata ad una riduzione della entità delle pulsazioni di pressione. Nel lavoro è stata affrontata anche la problematica connessa all'errore che si commette nella determinazione delle velocità quando per la misura si impieghino le sonde di pressione e nel flusso siano presenti pulsazioni di pressione.


1986 - Sull'influenza degli spillamenti nei gruppi combinati gas-vapore con post-combustione [Relazione in Atti di Convegno]
Cantore, Giuseppe
abstract

Vengono valutate le prestazioni di gruppi combinati, costituiti da sezioni a gas con post-combustione e da sezioni a vapore rigenerative, ai fini di un confronto con il caso in cui la sezione a vapore sia a semplice surriscaldamento. Lo studio evidenzia che l'adozione degli spillamenti può consentire un incremento del rendimento del gruppo combinato solo quando la temperatura dei gas all'ingresso della caldaia a recupero risulti maggiore di un determinato valore dipendente dal ciclo a vapore considerato a dalla minima temperatura ammessa all'uscita dalla caldaia a recupero. In ogni caso però il beneficio che si ottiene è di entità talmente modesta da non giustificare la maggiore complicazione impiantistica.


1985 - Analisi del flusso e prestazioni di un diffusore conico in presenza di componenti rotatorie di velocità [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi
abstract

Lo studio che qui si presenta riguarda l'analisi del flusso vorticoso e la valutazione delle prestazioni in un diffusore conico rettilineo avente rapporto fra l'area finale e quella iniziale pari a 3,92 e angolo totale di apertura di 12°. Le ricerche sono state eseguite in aria effettuando rilievi delle distribuzioni di pressione e di velocità in diverse sezioni disposte lungo l'asse del cono e per diversi valori dell'intensità di rotazione della vena fluida nella sezione d'ingresso. Per valutare le prestazioni del diffusore sono stati calcolati, in ogni sezione provata, i valori del coefficiente di recupero della pressione statica e dell'efficienza totale e si è analizzata l'influenza su di essi dell'intensità di rotazione del flusso. Il confronto con il caso di flusso puramente assiale permette di concludere che una modesta intensità di rotazione della vena fluida all'ingresso consente di ottenere valori più elevati del coefficiente di recupero della pressione e anche dell'efficienza qualora la rotazione sia tale da impedire l'eventuale instaurarsi di fenomeni di separazione.


1985 - Experimental analysis of the flow in a conical diffuser with pulsating pressures and evaluation of the consequent error in determining the velocity [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi
abstract

Experimental measurements of velocity and pulsating pressures have been carried out in a conical diffuser tested with air, in which a flow regime of transitory stall is established. Special importance is given to evaluation of the error made in determining the velocity and flow rate when pulsating pressures exist, and pressure probes are used in the measurements. An analysis is then made of the flow in order to go back to the main causes of the error.


1985 - Steam-Gas Combined Units. A Comparative Study [Relazione in Atti di Convegno]
Cantore, Giuseppe; G., Negri di Montenegro; P., Pelloni; S., Sandrolini; G., Naldi
abstract

Steam-gas combined units are studied from the view point of the attainable performaces by using a general methodology wich allows comparison between various possible solutions.


1985 - Studio e realizzazione di un apparato digitale per misure con sonde tridimensionali di pressione [Articolo su rivista]
Cantore, Giuseppe
abstract

Si riferisce sulla realizzazione di un apparato di misura adatto a rilevare i valori delle pressioni e/o delle differenze di pressione in uscita da sonde tridimensionali; esso è costituito da quattro uguali catene di misura disposte in parallelo comprendenti trasduttori pressione-tensione e voltmetri digitali.


1985 - Sui gruppi combinati gas-vapore con post-combustione [Relazione in Atti di Convegno]
Cantore, Giuseppe; G., Negri di Montenegro; G., Naldi
abstract

Nel presente lavoro vengono valutate le prestazioni dei gruppi combinati gas-vapore con post-combustione ed i limiti di convenienza della medesima, adottando una metodologia di indagine messa a punto dagli autori in studi precedenti. definito un grado di post-combustione se ne determinano i valori limite superiore e se ne valuta l'influenza sul rendimento totale del gruppo combinato con post-combustione mostrando in quali campi la pratica della post-combustione sia più conveniente. Lo studio mostra che, qualunque sia il gruppo a vapore scelto, il gruppo a gas che rende massimo il rendimento totale è sempre il medesimo ed in particolare è quello di massimo lavoro specifico, individuandosi così la condizione ottimale per detti gruppi combinati. Si conclude pertanto che l'adozione della post-combustione consente di ottenere il meglio dai gruppi combinati, abbinando ad un gruppo a vapore di più alto rendimento possibile, un gruppo a gas funzionante in condizioni di massimo lavoro specifico.


1985 - Sul comportamento di sonde di pressione in flussi con pulsazioni di pressione [Articolo su rivista]
Cantore, Giuseppe; R., Bettocchi
abstract

Si sono studiati e realizzati sistemi di misura costituiti da alcuni tipi di sonde di pressione collegate a trasduttori e relativi sistemi di acquisizione; in particolare l'analisi effettuata verte sulla valutazione della pressione che si stabilisce nella camera del trasduttore in relazione al valor medio della pressione di ingresso nel sistema.


1984 - Experimental investigations into vortex flow in a straight, annular section channel [Articolo su rivista]
Cantore, Giuseppe; R., Bettocchi
abstract

Results of experimental velocity measurements in air at several cross-sections along a straight annular section channel comparable to a hydraulic machine admission duct are presented. The flow analysis focuses on the axial and tangential velocity components and their modification with changes in the intensity of swirl along the channel. Particular prominence is given to an anomalous flow, the ‘dead water core’, occurring at the greatest swirl intensities. An earlier method of evaluating the core size of this anomalous flow on the basis of a vortex-type schematization is tested; Strscheletzky's method is also analysed. Finally a definition of the dead water core dimensions based on the axial velocity component distribution is proposed


1984 - Sul comportamento di sonde tridimensionali di pressione in un flusso vorticoso [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi
abstract

Si è studiato il comportamento di alcuni tipi di sonde tridimensionali di pressione quando vengono impiegate per misure in un flusso con componenti tangenziali di velocità e gradienti di pressione radiali. In particolare si sono confrontati i risultati sperimentali ottenuti esplorando lungo uno stesso diametro di un condotto di prova introducendo le sonde dalle due parti diametralmente opposte.


1982 - Analyse expérimentale de l'écoulement dans la zone axiale des canaux adducteurs des turbines-Hélices [Articolo su rivista]
Cantore, Giuseppe; R., Bettocchi; L., Magri; M., Ubaldi
abstract

The paper presents sorne results of the measurements carried out, in water, in the axial region of a propeller turbine admission duct (Hy), without runner, and, in air, in an annular section cylindrical duct fed by a radial distributor (1MB) (see Fig. 2). The measurements have been performed with different wicket-gate openings a and the attention has been drawn on the small openings where different phenomena have been observed (see Fig. 1) : a variation of the radial distribution of the tangential velocity near the hub, associated with the arising of a quite forced vortex ; the decrease and sometimes the inversion of the axial velocity; the presence of radial flows directed towards the hub; the drop of the total pressure, due to the viscous dissipation, These phenomena mainly develop in the axial region of the two ducts, rapidly extend their influence and finally settle on a practically constant area (see Fig. II). The distribution of axial and tangential velocity components change almost similarly in the two ducts according to the decrease of the wicket-gate opening, as it can be observed in figures 3 and 4. These figures show the distribution of axial and tangential velocity components divided by the average axial velocity, as a function of the ratio between the radius of the measurement points and the external one in the closest sections of the two ducts (1MB 2 and HyG). The similarity of the flow evolution in the two ducts is even more underlined by the comparison (see Fig. 5-8) of the velocity distributions for comparable values of the m parameter, called swirl rate, defined by the equation (1) and usually utilized in technical literature for the evaluation of the flow vortex intensity. In the diagram of figure 9 the radius limiting the central core, which is characterized by the decrease of axial velocity (ri) and the radius of the core characterized by the quite forced vortex distribution of tangential velocities (rf) have been associated to mparameter values, calculated by means of the geometric data of the duct according to the equation (2). The mand m values have been compared in the diagram of figure 10 versus a. Some experimental tests carried out on the Hy model with runner showed that, at small openings, a central core similar to the one previously described in the case without runner is developed (see Fig. 12). In axial turbines this phenomenon causes efficiency drop and cavitating vortexes which, as it happens without the runner (see Fig. 14), detach near the hub and pass through the runner (see Fig. 15) in a helix spiral form, thus causing vibrations and noise at low operation loads. The operation areas concerned by this phenomenon are indicated in figure 13 on the hill diagrams of a propeller and a Kaplan turbine with medium specific speed.


1982 - Ricerche sperimentali sul flusso in un canale rettilineo di sezione circolare in uscita da un distributore cilindrico [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi
abstract

Nel presente lavoro si espongono i risultati di ricerche sperimentali sulle distribuzioni di velocità in un canale rettilineo di sezione circolare in uscita da un distributore cilindrico a pale piane orientabili. I risultati ottenuti consentono di analizzare il flusso lungo il canale studiato ed in particolare di valutare le dimensioni di quella zona centrale, detta "nocciolo di acqua morta", nella quale si instaura un vortice di tipo forzato e la velocità assiale tende a valori nulli o negativi dando luogo ad una corrente anomala. Viene proposto un metodo, basato su una schematizzazione del tipo di vortice instaurato, che consente di valutare le dimensioni del "nocciolo di acqua morta" e che viene confrontato con quello proposto da altri autori.


1982 - Ricerche sperimentali sul flusso vorticoso in un canale rettilineo di sezione anulare [Relazione in Atti di Convegno]
Cantore, Giuseppe; R., Bettocchi
abstract

Si presentano i risultati di misure sperimentali di velocità, eseguite in aria, in diverse sezioni di un canale rettilineo di sezione anulare assimilabile ad un condotto adduttore di macchine idrauliche. L'analisi del flusso è rivolta in particolare allo studio delle componenti assiale e tangenziale di velocità, al loro modificarsi al variare dell'inclinazione conferita alla vena fluida e lungo l'asse del canale.


1981 - On the resistance offered to compressible flow by obstructions in series [Articolo su rivista]
Morandi, G.; Bettocchi, R.; Cantore, G.
abstract

A method is proposed for the determination of the flow characteristic of two flow restrictions in series, where an eliptical curve represents the relationship between the expansion coefficient (ratio of upstream and downstream pressures) and the reduced flow rate' for each individual obstruction. Elipse parameters are calculated for choking flow conditions of the combined system and the accuracy of the method is considered in the light of the assumptions made. (C.C.B.)


1981 - Ricerche sperimentali sulle misure di portata con diaframmi in presenza di componenti tangenziali di velocità [Articolo su rivista]
Cantore, Giuseppe; R., Bettocchi
abstract

N.D.


1981 - Sulla resistenza risultante di ostruzioni in serie nel flusso comprimibile [Articolo su rivista]
Cantore, Giuseppe; R., Bettocchi; G., Morandi
abstract

Si propongono metodi per la determinazione della caratteristica di portata di una resistenza risultante da due ostruzioni in serie, per ognuna delle quali la curva di portata sia rappresentabile con la relazione ellittica. Si forniscono indicazioni sull'approssimazione ottenibile con i metodi proposti.


1981 - Sulla scelta delle turbine di avviamento per gruppi propulsori aeronautici [Articolo su rivista]
R., Bettocchi; Cantore, Giuseppe
abstract

Si espone un criterio di scelta delle turbine di avviamento per gruppi propulsori aeronautici che consente di minimizzare il consumo di aria e, quindi, di combustibile necessari per l'avviamento. Per una applicazione del metodo proposto si sono utilizzate le curve caratteristiche ottenute da prove sperimentali condotte su un particolare tipo di queste turbine.


1979 - Costruzione e taratura di un Pitot sferico [Articolo su rivista]
Cantore, Giuseppe; R., Bettocchi
abstract

N.D.


1979 - Ricerche sperimentali sul flusso comprimibile attraverso resistenze in serie [Articolo su rivista]
Cantore, Giuseppe; R., Bettocchi
abstract

N. D.


1978 - Sulla portata di fluido compressibile attraverso resistenze in serie [Articolo su rivista]
Cantore, Giuseppe; G., Morandi; R., Bettocchi
abstract

N.D.


1977 - Sul dimensionamento dei compressori Roots [Articolo su rivista]
Cantore, Giuseppe; R., Bettocchi
abstract

N.D.