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Fabrizio PALTRINIERI

Professore Associato
Dipartimento di Scienze e Metodi dell'Ingegneria

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Pubblicazioni

2023 - A Computation Fluid Dynamics Methodology for the Analysis of the Slipper-Swash Plate Dynamic Interaction in Axial Piston Pumps [Articolo su rivista]
Muzzioli, G; Paltrinieri, F; Montorsi, L; Milani, M
abstract

This paper proposes a CFD methodology for the simulation of the slipper's dynamics of a swash-plate axial piston unit under actual operating conditions. The study considers a typical slipper design, including a vented groove at the swash-plate interface. The dynamic fluid-body interaction (DFBI) model is exploited to find the instantaneous position of the slipper, while the morphing approach is adopted to cope with the corresponding mesh distortion. A modular approach is adopted to ensure high-quality mesh on the entire slipper surface and sliding interfaces provide the fluid dynamic connection between neighboring regions. The external forces acting on the slipper are included by means of user-defined lookup tables with the simulation estimating the lift force induced by fluid compression. Moreover, the force produced by the metal-to-metal contact between the slipper and the swash plate is modeled through a specific tool of the software. The pressure signal over an entire revolution of the pump is taken as an input of the simulation and a variable time step is used to manage the high-pressure gradients occurring in the regions of inner and outer dead points of the piston. The weakly compressible characteristic of the fluid is considered by a specific pressure-dependent density approach, and the two-equation eddy-viscosity k-omega SST (shear stress transport) model is used to assess the turbulent behavior of the flow. Furthermore, the transitional model predicts the onset of transition, thus solving different equations depending on whether the flow enters a laminar or turbulent regime. In conclusion, the proposed methodology investigates the motion of the slipper in response to several external forces acting on the component. The numerical results are discussed in terms of variable clearance height, pressure distribution within the gap, and lift forces acting on the slipper under specific pump operations.

2023 - Development of a Numerical Approach for the CFD Simulation of a Gear Pump under Actual Operating Conditions [Articolo su rivista]
Orlandi, F; Muzzioli, G; Milani, M; Paltrinieri, F; Montorsi, L
abstract

The geometric complexity and high-pressure gradients that characterize the design of the flow field of gear pumps make it very difficult to obtain an accurate CFD simulation of the component. Usually, assumptions are made both in terms of geometrical features and physics being included in the analysis. The contact between the teeth, which is a key factor for the correct functioning of these pumps, represents a critical challenge in 3D CFD simulations, mainly due to the intrinsic limits of the dynamic meshing techniques that can hardly effectively manage a zero or close to zero gap point forming during gear rotation. The geometric complexity and high-pressure gradients that characterize the gear pump flow field make a CFD analysis quite difficult, and the contact between the gear teeth is usually avoided, thus being an extremely important feature. In this paper, a gear pump composed of inlet and outlet pipes was considered, and the contact between the gear's teeth was modeled in two different ways, one where it is effectively implemented and one where it is avoided using distancing and a proper casing modification. Herein, a new methodology is proposed for the application of the dynamic mesh method in the Simcenter STAR-CCM+ environment using an adaptive remeshing technique. The proposed methodology is compared with the alternative overset meshing method available in the software. The new meshing method is implemented using a user-routing that reproduces the real geometry of the gears while rotating during the pump operation, with teeth contact included. The routine is optimized in order to limit the additional computation and time needed for the remeshing process. The results that can be obtained using the two meshing approaches for the gear pump are compared in terms of computational effort and the accuracy of the results. The two methods showed opposite results in almost all the reported results, with the overset being more precise in the radial pressure evaluation and the dynamic being more reliable in the cavitation/aeration extension cloud.

2022 - A lumped parameter and CFD combined approach for the lubrication analysis of a helical gear transmission [Relazione in Atti di Convegno]
Muzzioli, G.; Paini, G.; Denti, F.; Paltrinieri, F.; Montorsi, L.; Milani, M.
abstract

2019 - Testing the performance of an innovative high speed external gear pump as a reliable hydraulic power unit for automotive robotized transmissions [Relazione in Atti di Convegno]
Paltrinieri, F.; Milani, M.; Montorsi, L.
abstract

In this paper the performance of an innovative, high speed, external gear pump have been measured and verified in order to evaluate its potential application as a reliable and efficient power unit for automotive, electro-hydraulic actuated, robotized transmissions. More in detail, this particular type of volumetric machine is built with two suction and two delivery ports and is specifically designed for extremely challenging operating conditions, mainly in terms of both rotational speed and delivery pressure. First of all, the most important hydraulic and mechanical performance parameters have been measured and analyzed, over a wide range of rotational speeds, spanning between 400 and 7000 rpm, and for two different operating temperatures, respectively equal to 40 and 60 °C. In this case, with the aim to increase the consistency of the experimental measurements, two external gear pumps, with exactly the same design geometry and features, have been tested and compared, also with available data coming from the pump manufacturer. All the experimental measurements have been performed with the help of a test bench, equipped with a double Cardan joint and an overdrive, specifically tailored for running the pump at high rotational speed and applying a delivery pressure of about 45 bar, very near to a typical actuation value of a high-performance automotive robotized transmission. At the end of this experimental work, it is possible to conclude that the high speed external gear pump here tested and analyzed can be considered a reliable and effective alternative hydraulic power unit for high-performance, automotive, robotized transmissions.

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.

2018 - Modelling and Testing an Innovative Combined Hydraulic Valve for High-Pressure Washing [Relazione in Atti di Convegno]
Paltrinieri, Fabrizio; Milani, Massimo; Montorsi, Luca; Terzi, Stefano
abstract

In this paper the main design features of an innovative combined hydraulic valve for high-pressure washing applications have been investigated by means of numerical modelling and experimental testing. This particular type of hydraulic component is obtained joining together a relief and a bypass valve. When the washing system is activated, the relief valve limits the maximum admitted working pressure while, when the washing system is switched off, the bypass valve unloads the hydraulic circuit and a direct connection with the drain ambient is quickly established. First of all, a very detailed lumped and distributed numerical model of the combined valve has been developed, with particular care devoted to the coupling between all the mechanical internal components (piston with holes, bushing and related springs) and to the valve body inner hydraulic connections. Then, the predictive capability of this lumped and distributed numerical model has been verified by means of a numerical versus experimental comparison, performed for a wide range of operating conditions (inlet pressure and volumetric flow rate) and geometrical parameters (sealing gaps, springs' stiffness and nozzle size). Finally, the previously validated numerical model has been applied in order to identify reliable design solutions for typical washing conditions, characterized by fluid pressure values spanning in the range between 50 to 280 bar and inlet volumetric flow rates comprised between 10 and 40 l/min.

2018 - Performance and Exhaust Emissions Analysis of a Diesel Engine Using Oxygen-Enriched Air [Relazione in Atti di Convegno]
Manenti, Flavio; Milani, Massimo; Montorsi, Luca; Paltrinieri, Fabrizio; Pirola, Carlo; Rinaldini, Carlo Alberto
abstract

Oxygen enriched air (EA) is a well known industrial mixture in which the content of oxygen is higher respect the atmospheric one, in the range 22-35%. Oxygen EA can be obtained by desorption from water, taking advantage of the higher oxygen solubility in water compared to the nitrogen one, since the Henry constants of this two gases are different. The production of EA by this new approach was already studied by experimental runs and theoretical considerations. New results using salt water are reported. EA promoted combustion is considered as one of the most interesting technologies to improve the performance in diesel engines and to simultaneously control and reduce pollution. This paper explores, by means of 3-dimensional computational fluid dynamics simulations, the effects of EA on the performance and exhaust emissions of a high-speed direct-injection diesel engine. For the analysis, a customized version of the KIVA 3 V code, including a detailed combustion chemistry approach, coupled with a comprehensive oxidation mechanism as a diesel oil surrogate, is used. A current-production 1.3-liter, four-cylinder engine is selected, and available experimental test data are used for validation of the engine model. Using the validated engine model, the effects of enriched air are investigated, along with the influence of injection strategies, under different operating conditions. It is found that oxygen-enriched combustion reduces soot emissions and improves engine thermal efficiency, but also increases in-cylinder peak pressure and nitrogen oxide (NOx) emissions. By changing the start of injection, it is possible to limit in-cylinder pressure to standard values and so reduce the NOx increment.

2015 - A Combined Methodology for Studying the Axial Balancing Mechanism of Orbit Annular Hydraulic Machines [Relazione in Atti di Convegno]
Bigliardi, Elisa; Francia, Marco; Milani, Massimo; Montorsi, Luca; Paltrinieri, Fabrizio; Stefani, Matteo
abstract

A customized combined methodology, based on both 2D CFD and lumped parameters numerical modeling, useful for simulating the hydraulic behavior of orbit annular machines, has been developed and here presented. More in details, the predictive capabilities of this CAE tool can be applied for the study of both roller and gerotor architectures and considering both pumping and motoring operating mode. First of all, a in-house developed 2D CFD methodology, based on the integration of the stationary form of the Reynolds equation for the determination of the pressure distribution inside the lateral clearances bounded by the sides of the stator-rotor group and the valve plate, as well as the internal manifold surface, is firstly presented and applied. The same computational procedure has been also involved for the investigation of the leakages through the clearance between the valve plate and the balancing ring. After that, a lumped and distributed parameters numerical model has been involved for the simulation of a typical orbit roller motor operation. In this case, particular care has been devoted to the modeling of the axial leakage clearances, adopting analytical interpolation functions deducted from the numerical results calculated applying the previously described 2D CFD methodology. Finally, the whole CAE approach has been validated by means of a comprehensive numerical vs. experimental comparison, obtaining a general good accordance for the overall operating field of this particular type of hydraulic unit.

2015 - Multi-phase and Multi-component CFD Analysis of a Load - Sensing Proportional Control Valve [Relazione in Atti di Convegno]
Bigliardi, Elisa; Francia, Marco; Milani, Massimo; Montorsi, Luca; Paltrinieri, Fabrizio; Stefani, Matteo
abstract

The paper analyzes the flow through a directional control valve for load –sensing application by means of a multi-phase and multi-component CFD approach. Numerical modeling includes both cavitation and aeration; in particular, the Rayleigh-Plesset equation and the inertia controlled growth model for bubble formation are adopted. The effects of gas release and vapor formation as well as turbulence on the main valve metering characteristics are investigated. The results show a remarkable influence of the aeration phenomena on the recirculating zones downstream of the metering area and thus on the cavitation onset region.

2014 - Experimental and numerical analysis of the combustor for a cogeneration system based on the aluminum/water reaction [Articolo su rivista]
Montorsi, Luca; Paltrinieri, Fabrizio; Milani, Massimo; Stefani, M.
abstract

The paper focuses on the design of the experimental apparatus aimed at analyzing the performance of the combustion chamber of a cogeneration system based on the reaction of liquid aluminum and water steam. The cogeneration system exploits the heat released by the oxidation of aluminum with water for super-heating the vapor of a steam cycle and simultaneously producing hydrogen. The only by-product is alumina, which in a closed loop can be recycled back and transformed again into aluminum. Therefore, aluminum is used as an energy carrier to transport the energy from the alumina reduction plant to the location of the proposed system. The water is also used in a closed loop since the amount of water produced employing the hydrogen obtained by the proposed system corresponds to the oxidizing water for the Al/H2O reaction. This study investigates the combustor where the liquid aluminum – steam reaction takes place; the design and the performance of the combustion chamber are evaluated using a numerical and an experimental approach. The test rig is specifically designed for the analysis of the liquid aluminum injection in a slightly super-heated steam stream. The first experiments are carried out to verify the correct behavior of the test rig. Thermography is employed to qualitatively assess the steam entrainment of the liquid aluminum jet. Finally, the experimental measurements are compared with the multi-dimension multi-phase flow simulations in order to estimate the influence of varying operating conditions on the combustion behavior. Further analysis will concern experiments aimed at investigating the reaction efficiency for different aluminum and water steam mass flow rates as well as the effects of the relative fuel/oxidizer speeds.

2013 - Improving the Performance of an Electro-Hydraulic Load-Sensing Proportional Control Valve [Articolo su rivista]
Babbone, Raffaele; Milani, Massimo; Montorsi, Luca; Paltrinieri, Fabrizio
abstract

The paper deals with the simulation and the experimental verification of the hydraulic behavior of an electro-hydraulic load-sensing proportional control valve. An innovative CAE (computer aided engineering) methodology, developed combining CFD (computational fluid dynamics) simulations with lumped and distributed numerical modeling, is firstly introduced and tailored by comparing the numerical results with measurements coming from an experimental campaign performed for a wide range of pressure loads and metered flow rates. Then, both the reliability and the limits of the numerical approach are highlighted through a detailed numerical vs. experimental comparison, involving the pressure of the main hydraulic lines, the flow rate through the first section and the local compensator displacement. Finally, the CAE methodology has been applied for assessing the internal ducts hydraulic permeability and the local compensator spring pre-load influence on the control valve metering curves. At the end of this analysis, an optimized design configuration, featuring a maximum controlled volumetric flow rate increased of more than 25%, has been proposed.

2013 - Modeling the Axial Balancing Mechanism of Orbit Annular Hydraulic Machines [Articolo su rivista]
Grasselli, Fabrizio; Milani, Massimo; Montorsi, Luca; Paltrinieri, Fabrizio
abstract

A customized combined methodology based on both 2D CFD (computational fluid dynamics) and lumped parameters numerical modeling, useful for simulating the hydraulic behavior of orbit annular machines, has been developed and here presented. More in details, the predictive capabilities of this CAE (computer-aided engineering) tool can be applied for the study of both roller and gerotor architectures and considering both pumping and motoring operating mode. First of all, an in-house developed 2D CFD methodology, based on the integration of the stationary form of the Reynolds equation for the determination of the pressure distribution inside the lateral clearances bounded by the sides of the stator-rotor group and the valve plate, as well as the internal manifold surface, is firstly presented and applied. The same computational procedure has been also involved for the investigation of the leakages through the clearance between the valve plate and the balancing ring. After that, a lumped and distributed parameters numerical model has been involved for the simulation of a typical orbit roller motor operation. In this case, particular care has been devoted to the modeling of the axial leakage clearances, adopting analytical interpolation functions deducted from the numerical results calculated applying the previously described 2D CFD methodology. Finally, the whole CAE approach has been validated by means of a comprehensive numerical versus experimental comparison, obtaining a general good accordance for the overall operating field of this particular type of hydraulic unit.

2013 - Optimization of the working cycle for a hydrogen production and power generation plant based on aluminum combustion with water [Articolo su rivista]
Mercati, Stefano; Milani, Massimo; Montorsi, Luca; Paltrinieri, Fabrizio
abstract

The working cycle of a novel hydrogen and power generation system based on aluminum combustion with water is analyzed in order to evaluate the best performance in terms of energy conversion efficiency. The system exploits the exothermic reaction between aluminum and steam and produces thermal power for a super-heated steam cycle and hydrogen as a by-product of the reaction. A lumped and distributed parameter approach is adopted for simulating the whole thermo-dynamics cycle and it includes the main components such as the combustion chamber, the steam generator, the turbine and the heat exchangers. Proper numerical models are created to account for the physical phenomena occurring in each of the considered component and are validated against experimental measurements available in literature or theoretical formulations. In particular several plant configurations corresponding to different working cycles are investigated, and their performance in terms of global efficiency, power output and hydrogen yield is discussed. The adoption of a turbine back pressure working cycle demonstrates to reduce the aluminum consumption and to enhance the electrical power conversion efficiency.

2012 - A Transient Multidimensional CFD Approach to the Analysis of a Control Valve Using Non-Newtonian Fluids [Articolo su rivista]
Grasselli, Fabrizio; Milani, Massimo; Montorsi, Luca; Paltrinieri, Fabrizio
abstract

In this paper the flow through a control directional valve is studied by means of a Computational Fluid-Dynamics analysis under transient operating conditions. The mesh motion is resolved on a time basis as a function of the external actuation system. In the analysis, an open source fluid-dynamics code is used and both cavitation and turbulence are accounted for in the modeling. Moreover, the numerical model of the working fluid is modified in order to account also for the non-Newtonian fluids. The effects of the shear rate on the shear stress are accounted for both by using experimental measurements and correlations available in literature, such as the Herschel-Bulkley model. The analysis determines the performance of the control directional valve under different operating conditions when using either Newtonian or non-Newtonian fluids. In particular, the discharge coefficient, the recirculating regions, the flow acceleration angle and the pressure and velocity fields are investigated.

2012 - Design of a Hydraulic System for Liquid Packaging [Articolo su rivista]
Angeloni, Claudio; Franzoni, Federica; Milani, Massimo; Paltrinieri, Fabrizio
abstract

The paper analyzes the dynamic behaviour of an industrial system devoted to the automated hydraulic packaging of beverages. More in detail, a lumped and distributed numerical approach is used to model both the filling system and the multi-actuators hydraulic circuit needed to shape and separate the packages. The model reliability and accuracy are addressed by means of a numerical vs. experimental comparison of the main hydraulic and mechanical quantities for an actual production rate. Afterwards, the system architecture is redesigned in order to obtain higher production rates, and the effects of the hydraulic behaviour variation on the hydraulic efficiency are highlighted. Finally, a sensitivity analysis with respect to the main design parameters is carried out, in order to determine the circuit layout that maximizes the system efficiency in the whole production-rate range.

2012 - Design of the steam generator in an energy conversion system based on the aluminum combustion with water [Articolo su rivista]
Mercati, Stefano; Milani, Massimo; Montorsi, Luca; Paltrinieri, Fabrizio
abstract

The paper shows the preliminary design of the superheated steam generator to be used in a novel hydrogen production and energy conversion system based on the combustion of aluminum particles with water. The system is aimed at producing hydrogen and pressurized superheated steam, using the heat released by the Al–H2O reaction. The interest on this type of technology arises because of the possibility of obtaining hydrogen with very low pollutant and greenhouse gas emissions, compared to the traditional hydrogen production systems, such as the steam reforming from methane. The analysis of the combustion chamber and the heat recovery system is carried out by means of a lumped and distributed parameter numerical approach. The multi phase and gas mixture theoretical principles are used both to characterize the mass flow rate and the heat release in the combustion chamber and within the heat exchangers in order to relate the steam generator performance to the system operating parameters. Finally, the influence of the steam generator performance on the whole energy conversion system behavior is addressed, with particular care to the evaluation of the total power and efficiency variation with the combustion parameters.

2012 - Multidimensional Design of Hydraulic Components and Systems [Capitolo/Saggio]
Milani, Massimo; Montorsi, Luca; Paltrinieri, Fabrizio
abstract

In this chapter, the above mentioned critical aspects in the application of multidimensional numerical analysis for the design of mechanical devices and components for hydraulic systems are addressed. The objective of the chapter is to provide a roadmap for the multidimensional numerical analysis of the hydraulic components to be used effectively in the design process. In particular, two examples of hydraulic systems are accounted for in the application of the CFD analysis: a proportional control valve and a fuel accumulator for multi-fuel injection systems. These test cases have been selected due to their representativeness in the field of hydraulic applications and to the complexity and variety ofthe physical phenomena involved.

2012 - Proceedings of the 7th FPNI PhD Symposium on Fluid Power [Curatela]
Milani, Massimo; Montorsi, Luca; Paltrinieri, Fabrizio
abstract

All Young Researchers and PhD Students coming from all over the world interested in Fluid Power have been invited to present the results and the directions of their scientific activities, and to establish new contacts for a broader R&D cooperation in fluid power technology and related fields.This Proceedings collect about 50 works from about 200 Authors, coming from more than 15 countries, and they highlight the academic results and the industrial applications shown during the 11 Technical Sessions held during the three days of Symposium.

2011 - A Transient Multidimensional CFD Approach to the Analysis of a Control Valve using Non-Newtonian Fluids [Relazione in Atti di Convegno]
Angeloni, Claudio; Franzoni, Federica; Montorsi, Luca; Milani, Massimo; Paltrinieri, Fabrizio
abstract

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2010 - A quasi-dimensional combustion model for performance and emissions of SI engines running on hydrogen–methane blends [Articolo su rivista]
Perini, Federico; Paltrinieri, Fabrizio; Mattarelli, Enrico
abstract

The development of a predictive two-zone, quasi-dimensional model for the simulation of the combustion process in spark ignited engines fueled with hydrogen, methane, or hydrogen–methane blends is presented. The code is based on a general-purpose thermodynamic framework for the simulation of the power cycle of internal combustion engines. Quasi-dimensional modelling describes the flame front development assuming a simplified spherical geometry, as well as infinitesimal thickness. The flame front subdivides the in-cylinder volume into a zone of unburned mixture, and a second zone of burned gases. As far as the combustion process is concerned, attention is paid to the description of the physical and chemical phenomena controlling the flame development and the formation of combustion products. First of all, an empirical correlation has been defined for estimating the laminar burning velocity. The equation, tailored for arbitrary fuel blendings and equivalence ratios, has been validated against detailed experimental data. Furthermore, the influence of turbulence on flame evolution has been implemented according to a fractal-based model. Then, a physical and chemical computing environment for evaluating both gaseous mixtures’ thermodynamic properties, and equilibrium species concentrations of combustion products has been developed and coupled to the code. The validation has been performed by comparing numerical pressure traces against literature experimental data, on a standard CFR single-cylinder engine. A unique set-up of the model parameters has been obtained, suitable for both pure hydrogen and pure methane fuelings; finally, the predictive capabilities of the model have been applied to analyze different fuel blends and equivalence ratios: the comparison against experimental pollutant emissions (NO and CO) shows a reasonable accuracy.

2010 - Development and Validation of Predictive Emissions Schemes for Quasi-Dimensional Combustion Models [Relazione in Atti di Convegno]
Perini, Federico; Mattarelli, Enrico; Paltrinieri, Fabrizio
abstract

The paper presents the development and validation of phenomenological predictive schemes for quasi-dimensional modeling of pollutant emissions in direct injected Diesel engines. Models for nitric oxide (NO), carbon monoxide (CO), as well as soot and unburned hydrocarbons (HC) have been developed. All of them have been implemented into a DI Diesel engine simulation environment, previously developed by the authors, which features quasi-dimensional modeling of spray injection and evolution, air-fuel mixture formation, as well as auto-ignition and combustion. An extended Zel'dovich mechanism, which takes into account the three main, thermal-NO formation chemical reactions has been developed for predicting NO emissions. A simple, one-reaction soot formation model has been implemented, while a new approach has been proposed for soot oxidation, which considers two different temperature ranges: the well-established Nagle and Strickland-Constable one has been adopted for the highest temperatures, while a new, single-step reaction model has been implemented at the low temperatures. The model for carbon monoxide formation relies on five chemical reactions, whose kinetics are computed exploiting partial equilibrium assumptions, in a system of 11 species. Finally, hydrocarbon emissions have been modeled taking into account the effects of three main sources: fuel injected and mixed beyond the lean combustion limit, fuel yielded by the injector sac volume and nozzle holes, as well as overpenetrated fuel. A detailed comparison with experimental data from a high speed, direct injected diesel engine, carried on for both full and partial load and for a wide range of engine speeds, shows that the models are capable to predict the engine emissions with reasonable reliability.

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 - 2-Stroke Diesel engine for light aircraft: IDI vs. DI combustion systems [Relazione in Atti di Convegno]
Mattarelli, Enrico; Paltrinieri, Fabrizio; Perini, Federico; Rinaldini, Carlo Alberto; M. C., Wilksch
abstract

The paper presents a numerical study aimed at converting a commercial lightweight 2-Stroke Indirect Injection (IDI) Diesel aircraft engine to Direct Injection(DI). First, a CFD-1D model of the IDI engine was built and calibrated against experiments at the dynamometer bench. This model is the baseline for the comparison between the IDI and the DI combustion systems. The DI chamber design was supported by extensive 3D-CFD simulations, using a customized version of the KIVA-3V code. Once a satisfactory combustion system was identified, its heat release and wall transfer patterns were entered in the CFD-1D model, and a comparison between the IDI and the DI engine was performed, considering the same Air-Fuel Ratio limit. It was found that the DI combustion system yields several advantages: better take-off performance (higher power output), lower fuel consumption at cruise conditions, improved altitude performance, reduced cooling requirements. Furthermore, the injection system requirements for DI combustion can be met also by mechanical pump and injectors.

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 - Design and Optimization of a Variable Displacement Vane Pump for High Performance IC Engine Lubrication - Part 1 - Experimental analysis of the circumferential pressure distribution with dynamic pressure sensors [Relazione in Atti di Convegno]
A., Bianchini; G., Ferrara; L., Ferrari; Milani, Massimo; Paltrinieri, Fabrizio; F., Tosetti
abstract

In the present automotive research, increasing efforts are being directed to improve the overall organic efficiency, which, inter alia, means to improve the operational behavior of the auxiliary organs. This paper reports an experimental approach for the determination and analysis of the pressure distribution in a variable displacement vane pump for high speed internal combustion engine lubrication. More in details, an actual application is presented for a seven-blades variable displacement vane pump equipped with a hydraulic geometry variation system. This unit is characterized by a high performance, in terms of rotational speed, delivery pressure and displacement variation. The experimental layout and some relevant facilities are described. An extended test campaign was performed on the pump to characterize its operational behavior. Rotational speeds from the idling regime to the maximum sustainable regime were tested by varying the hydraulic circuit load: the results of the pressure field are shown together with a detailed description of the oil physical behavior into the pump. Furthermore, several changes in the geometry of the pump, which were suggested by the experimental campaign, are presented and their influence on the performance of the pump is evaluated and discussed with a comparative performance analysis.

2009 - Design and Optimization of a Variable Displacement Vane Pump for High Performance IC Engine Lubrication. Part 2 - Lumped parameters numerical analysis. [Relazione in Atti di Convegno]
A., Bianchini; G., Ferrara; L., Ferrari; Milani, Massimo; Paltrinieri, Fabrizio; F., Tosetti
abstract

In this paper a detailed analysis focused on lumped parameters numerical modeling 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 modeling 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.

2009 - Sviluppi nello studio di pompe e macchine volumetriche ad ingranaggi esterni [Articolo su rivista]
Borghi, Massimo; Paltrinieri, Fabrizio; Zardin, Barbara
abstract

L'articolo presenta un resoconto delle attività di ricerca, modellazione e simulazione relative alle macchine ad ingranaggi esterni, portate avanti dal gruppo di ricerca di Macchine e Sistemi Energetici presso il Dipartimento di Ingegneria Meccanica dell'Università di Modena e Reggio Emilia

2008 - External Gear Pumps and Motors Bearing Blocks Design: Influence on the Volumetric Efficiency [Relazione in Atti di Convegno]
Borghi, Massimo; Milani, Massimo; Paltrinieri, Fabrizio; Zardin, Barbara
abstract

External gear pumps and motors, in their typical commercial design, are equipped with hydraulically balanced bearing blocks, which allow to maintain good volumetric efficiencies also when the pressure drop between the ports is high. The aim of this work is to analyze some geometrical aspects characterizing the bearing blocks design, evaluating their influence on the volumetric efficiency of the machine with the aid of a numerical model properly created. External gear pumps and motors operation behavior is strongly influenced by the volumetric efficiency; this parameter takes into account the leakages of fluid which typically affect the hydraulic machine operation and, together with the mechanical efficiency, determines its total efficiency and, consequently, has a great influence on power loss.

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 Combustion System for 2-Stroke HSDI Diesel Engines [Relazione in Atti di Convegno]
DE MARCO, Carlo Arturo; Mattarelli, Enrico; Paltrinieri, Fabrizio; Rinaldini, Carlo Alberto
abstract

The Department of Mechanical and Civil Engineering (DIMeC) of the University of Modena and Reggio Emilia is developing a new type of small capacity HSDI 2-Stroke Diesel engine, featuring a specifically designed combustion system. The present paper is focused on the analysis of the combustion process, investigated by means of a customized version of the KIVA-3V code. A four stroke automobile Diesel engine featuring a very close bore size is taken as a reference, for both the numerical models calibration and for a comparison with the 2-Stroke engine. Such a comparison clearly demonstrates the effectiveness of the two stroke concept in terms of emissions reduction and high power density.

2007 - CAE Development of Automotive Hydraulic Applications [Relazione in Atti di Convegno]
Milani, Massimo; Paltrinieri, Fabrizio
abstract

L'articolo illustra i principlai risultati ottenibili mediante l'uso di strumenti numerici a parametri concnetrati e multidimensionali nello sviluppo progettuale e nell'ottimizzazione funzionale di sistemi idraulici per applicazioni automotive.

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 - Numerical Characterization of Pipes And Hoses Dynamic Response [Relazione in Atti di Convegno]
Borghi, Massimo; Milani, Massimo; Paltrinieri, Fabrizio; Zardin, Barbara
abstract

This paper deals with the study of pipes and hoses dynamic characteristics variation with the fluid-wall equivalent bulkmodulus description, with particular attention devoted to the analysis of the wall thickness, of the mechanical constraintsand of the internal pressure both on the fluid celerity, and on the pipe frequency response. In particular, consideringboth the case of plain stress and of plain strain, the pipe wall compliance and bulk modulus are firstly derived as afunction of the internal pressure and of the wall elastic and geometrical characteristics. Then, the influence of the pipegeometry and of the wall thickness on the pipe wall compliance and bulk modulus are highlighted for some materials ofinterest for industrial, automotive and aerospace applications (steel, aluminium, titanium and wired rubber), and thedependency of the equivalent bulk modulus on these parameters and on fluid physical characteristics is highlighted.Finally, the influence of mechanical constraints, of pipe geometry, of fluid physical properties, of wall material and offluid pressure on the global pipe dynamic response characteristics, and in particular on the fluid celerity, on the Machnumber and on the natural frequency, is evidenced.

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.

2006 - The influence of aeration and cavitation on gear pumps and motors meshing volumes pressures [Relazione in Atti di Convegno]
Borghi, Massimo; Milani, Massimo; Paltrinieri, Fabrizio; Zardin, Barbara
abstract

The paper describes the influence of the fluid modeling on cavitation and aeration detection in external gear pumps and motors inter-teeth volumes during the gears meshing process, in order to compare the results coming from the use of different physical models of air release/adsorption and cavitation. A simplified cavitation model is firstly involved, and pressure transients are calculated imposing a pressure cut when the fluid vapor pressure (or the dissolved air partial pressure) is reached. After, assuming an equivalent approach able to involve the vapor phase generation, the cavitation phenomena in the meshing volumes are deepened, and the influence of the fluid modeling enhancement on the cavitating machine behavior is highlighted. Then, the equivalent fluid approach is enhanced introducing the air release, and properly coupling the gaseous phases release/adsorption to the Henry's Law for not instantaneous processes. Finally, the influence of the air release/adsorption time constant on meshing volumes pressure transients are detailed, with particular attention devoted to the modification introduced by the cavitation detailing on the gaseous phase void fraction determination and on the angular extension of the cavitation phenomena detection.

2005 - Pressure Transients in External Gear Pumps and Motors Meshing Volumes [Relazione in Atti di Convegno]
Borghi, Massimo; Milani, Massimo; Paltrinieri, Fabrizio; Zardin, Barbara
abstract

In this paper a lumped parameters numerical model isreviewed to study the meshing process of external gearpumps and motors, with the aim of highlighting theinfluence of some geometrical design parameters andoperating conditions on inter-teeth volumes pressures.The inter-teeth space is modeled adopting a two-volumeapproach, properly tailored both for the pump and for themotor units behavior description. In both cases, thecommunications between the interconnected inter-teethvolumes and the high and low pressure ports aresketched as variable equivalent turbulent restrictors; flowareas have been determined as functions of the gearsand of the meshing grooves main design parameters.The inter-teeth pressures, and the leakage flows, arecalculated solving the incompressible and isothermalcontinuity equation, contemporarily applied to bothvolumes and properly combined with the classicalturbulent orifice equation. Successively, for a referenceoperating condition, properly chosen for underlining theinter-teeth meshing cycle and corresponding to a verylow pressure load, the meshing processes of an externalgear pump and of an external gear motor are compared.Among others, the attention is focused on the behaviorof those hydraulic variables more conditioning themeshing cycle, and the differences rising up in interteethpressure peaks and in cavitation interval amplitudeand angular positioning are evidenced. Then, themeshing process analysis is expanded to cover theexternal gear units common operating field, both interms of rotational speed (from 500 to 3000 rpm) and interms of the high pressure port value (from 10 to 250bar). In all cases, the general trend shows that cavitationhas a deeper influence on external gear pumpsoperation, while external gear motors are subjected tomore significant pressure peaks, particularly markedduring the low pressure part of the meshing cycle.Attention is also focused on the influence of gears interaxialdistance and axial width on the meshing processcharacteristics, in order to assess how the volumedimensions could differently affect pressure peaks andcavitation phenomena in pumps and motors.Finally, the role of the balancing plates grooves inconditioning pressure peaks and cavitation is highlightedand, with particular care devoted to external gearmotors, some useful guidelines for their design areoutlined.

2005 - Studying the Axial Balance of External Gear Pumps [Relazione in Atti di Convegno]
Borghi, Massimo; Milani, Massimo; Paltrinieri, Fabrizio; Zardin, Barbara
abstract

In this paper some design aspects related to externalgear pumps balancing surfaces are studied, and someuseful guidelines for designing bearing blocksbalancing surfaces are suggested. In order to studybearing blocks axial balance, a numerical procedurefor the determination of the pressure distribution insidethe clearance bounded by gears sides and bearingblocks internal surfaces is firstly presented andapplied. After, the influence of bearing blocksgeometry and pump operating conditions on thewidening thrust is highlighted, considering bothconstant and variable lateral clearance heights. Then,the computations are performed to evaluate thewidening thrust variation as a function of bearingblocks relative tilt with respect to gears lateral sides,and both positive and negative bearing blocks tilts areevidenced and discussed. Finally, the numericalprocedure is validated through a comprehensivecomparison of its results with experimental data(coming from some bibliographic sources), and someuseful guidelines in designing external gear pumpsbalancing surfaces are defined.

2005 - Studying the Efficiency of a Compact Excavator Primary Workgroup Hydraulic Control System [Relazione in Atti di Convegno]
Borghi, Massimo; Milani, Massimo; Paltrinieri, Fabrizio; Zardin, Barbara
abstract

This paper studies the proportional directional controlvalves design influence on the energetic behavior of amid-power compact excavator.In particular, with reference to the hydraulic circuitactuating the primary workgroup, in the paper thehydraulic power metering performed with the boomcylinder proportional control valve is studied, and somedesign solution useful in reducing both the hydraulicpower dissipation, and the power absorption from themachinery prime mover are highlighted.The analysis, experimentally performed for differentoperating conditions, is carried out highlighting theinfluence of a metering configuration both on the supplypressure modulation and on the flow-rate supplied tothe actuator.The hydraulic power metering and the boom actuationhydraulic efficiency are defined for two alternativeproportional control valve metering configurations and,within the limits implicitly implied on the actuation circuitarchitecture, a possible design solution in determiningthe improvement of the boom actuation systemperformances is investigated.

2005 - The Influence of the Notch Shape and Number on Proportional Directional Control Valve Metering Characteristics [Articolo su rivista]
Borghi, Massimo; Milani, Massimo; Paltrinieri, Fabrizio
abstract

The paper investigates, by means of a 3D, steady-state, incompressible and isothermal CFD analysis, the influence of the notch shape and number on proportional directional control valves metering edge characteristics. The numerical activity is firstly performed for a sharp metering edge, considered as reference case.Then, different configurations of notched metering edges are considered, coming from the adoption of two notch geometrical shapes largely used in proportional directional control valves actual design, and from a symmetrical displacement of two, three and four notches on the spool periphery. For all the cases considered, the qualitative analysis of the internal flow field is performed in order to highlight the fluid efflux main characteristics.After, a quantitative analysis of the metering characteristics is introduced, with the aim of determining the influence of the metering configuration, of the spool position and of the operating conditions on the efflux characteristics (the discharge coefficient and the jet angle).

2004 - About the Prediction of Pressure Variation in the Inter-Teeth Volumes of External Gear Pumps [Relazione in Atti di Convegno]
Borghi, Massimo; Milani, Massimo; Paltrinieri, Fabrizio; Zardin, Barbara
abstract

The paper deals with the analysis of the inter-teeth pressure transients during gears meshing cycle of external gear pumps. A lumped parameter model, tailored for the prediction of pressures in the meshing zone, is firstly presented. The numerical model, based on the integration of the continuity equation, is applied to the inter-teeth volumes, communicating with the neighbouring ambient through geometry dependent orifices. A comparison between numerical results, obtained considering both constant and variable discharge coefficients, is illustrated. Successively, the dependency of pressure transients on gear pump operating conditions, mainly in terms of delivery pressure and rotational speed, is investigated. The effect of some geometric parameters is also discussed, mainly considering different gears widths and interaxial distances, and high-pressure recess positioning. Finally, in order to highlight the influence of the cavitation modelling on low pressure transition, the results coming from the application of two simplified approaches are shown and compared.

2004 - Stydying the Flow Field Inside Lateral Clearances of External Gear Pumps [Relazione in Atti di Convegno]
Paltrinieri, Fabrizio; Borghi, Massimo; Milani, Massimo
abstract

In this paper the flow field in the clearances bounded by gears lateral sides and bearing blocks internal surfaces of external gear pumps is studied. Firstly, the pressure distribution is determined applying the Laplace equation to the domain limited by two successive teeth profiles, the middle lines of the first and of the last space and the drain circle, and the main leakage paths inside the clearance are evaluated. Then, the leakage flows between the spaces, and between each space and the drain ambient, are calculated considering different boundary conditions and teeth shapes, and the streamlines are highlighted in order to evidence the main leakage paths. The information gathered through this flow field analysis are used to define equivalent conductance for leakage paths, useful to be adopted in simple lumped parameters models, usually applied with the aim to determine the pressure distribution inside pump casing or, for example, gear pumps volumetric efficiency.

2004 - The Effect of Flow Forces Compensating Profile on the Metering Characteristics of a Conical Seat Valve [Relazione in Atti di Convegno]
Borghi, Massimo; Milani, Massimo; Paltrinieri, Fabrizio
abstract

This paper studies the influence of the discharge chamber geometrical parameters on the steady-state characteristics behavior of a conical seat valve having compensating profile.More in details, starting from the analysis of the experimental behavior of an actual valve showing inefficient characteristic curves, the metering openings leading to the transition from under to over compensation are individuated.Then, a 3D CFD steady-state, incompressible and isothermal analysis is involved, mainly to evidence the valve discharge coefficient and flow-forces variations with operating conditions.After, two alternative valve configurations, presenting a low pressure region designed to optimize the flow-forces compensation, are characterized through the 3D CFD analysis.

2004 - The Influence of the Notch Shape and Number on Proportional Directional Control Valve Metering Characteristics [Relazione in Atti di Convegno]
Borghi, Massimo; Milani, Massimo; Paltrinieri, Fabrizio
abstract

The paper investigates, by means of a 3D, steady-state, incompressible and isothermal CFD analysis, the influence of the notch shape and number on proportional directional control valves metering edge characteristics. The numerical activity is firstly performed for a sharp metering edge, considered as reference case. Then, different configurations of notched metering edges are considered, coming from the adoption of two notch geometrical shapes largely used in proportional directional control valves actual design, and from asymmetrical displacement of two, three and four notches on the spool periphery. For all the cases considered, the qualitative analysis of the internal flow field is performed in order to highlight the fluid efflux main characteristics. After, a quantitative analysis of the metering characteristics is introduced, with the aim of determining the influence of the metering configuration, of the spool position and of the operating conditions on the efflux characteristics (the discharge coefficient and the jet angle).

2003 - A Conservative High Resolution Scheme for the Study of Gases and Liquids Homentropic Flows [Relazione in Atti di Convegno]
Borghi, Massimo; C., Bussi; Milani, Massimo; Paltrinieri, Fabrizio
abstract

In this paper a high-resolution explicit integration scheme is introduced and adopted to study the one-dimensional homentropic flow of a generic fluid, applicable to gaseous and liquid phase. The generally valid governing equations for one-dimensional homentropic flows are firstly introduced and, without forcing any assumption in relation to the nature of the fluid, an investigation of mathematical properties of the system of equations is given in order to derive the characteristic matrix and the system eigenvalue. Then, the Maxwell differential formulation of the fluid constitutive equations is introduced, with the purpose of providing a general state equation which retains its validity for both gases and liquids, and with the aim of expressing and explicitly calculating pressure, pressure derivative with respect to density and sound speed as functions of fluid bulk modulus. Starting from the differential formulation of the state equation, a high-resolution explicit integration scheme, based on conservative formulation of the governing equations for fluid flows, is then introduced and discussed. Finally, the well-known shock tube test is employed to study both liquid and gaseous flows, and the forthcoming numerical vs. analytical results comparison is used to assess the accuracy and the stability of the integration scheme.

2003 - A Numerical Approach to the Hydraulic Fluid Properties Prediction [Relazione in Atti di Convegno]
Borghi, Massimo; Bussi, Carlo; Milani, Massimo; Paltrinieri, Fabrizio
abstract

This paper presents a numerica! approach tailored for the prediction ofhydraulic fluids physical and thennodynarnic properties, starting from a limited number of information about fluid viscosity and fluid density. Firstly, the review of some experimental based prediction models available in literature for the fluid viscosity variations is presented, and the more accurate ones for the analysis ofindustrial and automotive hydraulic fluids (mineral oils, lubricants and fuels) are selected. Then, the paper highlights the step of a possible procedure able to defme thevariations both of other physical fluid praperties (such as the isothermal or the isentropic bulk modulus, the constant pressure or the constant volume specific heat, the constant pressure, orthe constant volume, volume expansion coefficient), and of the main thermodynamic fluid properties (such as the specific entropy, the specific enthalpy and the specific internal energy).Finally, the resu1ts coming from the numerical approach previously outlined are compared with experimental data, found in literature for different mineral oils, in a range of temperature from O to 160°C and of pressure from O to 600 bar.

2003 - Studio del Campo di Moto nei Meati Laterali di Macchine Volumetriche ad Ingranaggi Esterni [Relazione in Atti di Convegno]
Borghi, Massimo; Milani, Massimo; Paltrinieri, Fabrizio
abstract

Viene presentato lo studio del campo di moto nel meato, supposto ad altezza costante, esistente tra i fianchi delle ruote dentate e le superfici delle fiancate di bilanciamento di macchine volumetriche ad ingranaggi esterni. A partire dalla determinazione della distribuzione di pressione nel meato vengono determinati, al variare della geometria e delle condizioni al contorno, le portate e le linee di corrente. La valutazione delle portate scambiate dal generico vano con i vani contigui e con l’ambiente di drenaggio viene poi utilizzata per mettere a punto un modello di meato a parametri concentrati che si mostra essere più accurato di quello utilizzato in precedenti lavori per il calcolo della distribuzione di pressione nei vani tra i denti affinando la determinazione delle conduttanze caratteristiche degli strozzatori in esso considerati. I risultati, relativi a diverse geometrie di ruote dentate di corrente impiego, vengono poi confrontati tra loro al fine di evidenziare l’influenza dei parametri geometrici caratteristici delle dentature sulla distribuzione di pressione nel meato, sulla ripartizione delle principali portate di fuga e sulle dimensioni caratteristiche degli strozzatori equivalenti considerati nei modelli a parametri concentrati. I risultati ottenuti mostrano altresì come il modello proposto risulti adeguato per le geometrie di dentatura considerate e pare particolarmente promettente per essere utilizzato nella previsione e calcolo del rendimento volumetrico.

2002 - Modelling and Simulating Hydraulically Balanced External Gear Pumps [Relazione in Atti di Convegno]
Borghi, Massimo; Paltrinieri, Fabrizio; Milani, Massimo
abstract

The paper presents some developments of a research activity regarding hydraulically balanced external gear pumps.Numerical models are introduced in order to study gears radial equilibrium and axial bearing blocks balance. A numericalapproach useful for determining the eccentric positions assumed by gears inside the pump casing and to assess the radialthrusts acting on gears is proposed. The effect of the running in process on the casing internal surface and on the pressure distribution in sealed spaces between teeth is also shown and discussed. At the end a numerical model useful in designing bearing blocks balancing surfaces is outlined. Comparisons of numerical and experimental results seem to encourage the development of the study.

2001 - Influenza del Rodaggio sulle Condizioni di Funzionamento di Macchine Volumetriche ad Ingranaggi Esterni [Relazione in Atti di Convegno]
Borghi, Massimo; Milani, Massimo; Paltrinieri, Fabrizio; M., Guidetti
abstract

Si illustrano gli ultimi sviluppi di un modello, descritto in (Bonacini e Borghi, 1990) ed in (Borghi et al., 1997), per il calcolo dell’andamento della pressione nei vani compresi tra due denti consecutivi, le fiancate ed il corpo di macchine volumetriche ad ingranaggi esterni. Nella prima parte del lavoro viene presentato un modello per la determinazione della posizione assunta dalle ruote, durante il funzionamento, all’interno del corpo della macchina. In particolare, la posizione di lavoro delle ruote è determinata valutando separatamente due contributi: il primo dovuto al recupero del gioco esistente tra le fiancate ed il corpo; il secondo legato alla capacità di sostentamento del carico della coppia rotoidale lubrificata costituita dall’albero della ruota e dalle boccole alloggiate nelle fiancate. In questo modo è possibile evidenziare, da un lato le condizioni di funzionamento che portano le ruote ad interferire con la superficie interna del corpo, dall’altro l’entità dell’asportazione di materiale dal corpo stesso. I profili della superficie interna del corpo così ottenibili vengono poi confrontati, per macchine operatrici di corrente produzione industriale di diverse caratteristiche geometriche, con i corrispondenti rilevati al termine di processi di rodaggio appositamente predisposti. I confronti effettuati mostrano la sostanziale validità del modello presentato, la sua generale attendibilità e l’applicabilità industriale.