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Carlo Alberto RINALDINI

Professore Associato
Dipartimento di Ingegneria "Enzo Ferrari"

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Pubblicazioni

2024 - Optimization of the Combustion Chamber Design of a Natural Gas-Diesel Dual Fuel Engine Running at Low Load [Relazione in Atti di Convegno]
Scrignoli, Francesco; Savioli, Tommaso; Rinaldini, Carlo Alberto
abstract

2023 - Combustion Chamber Optimization for Dual-Fuel Biogas–Diesel Co-Combustion in Compression Ignition Engines [Articolo su rivista]
Caprioli, Stefano; Volza, Antonello; Scrignoli, Francesco; Savioli, Tommaso; Mattarelli, Enrico; Rinaldini, Carlo Alberto
abstract

Micro-cogeneration with locally produced biogas from waste is a proven technique for supporting the decarbonization process. However, the strongly variable composition of biogas can make its use in internal combustion engines quite challenging. Dual-fuel engines offer advantages over conventional SI and diesel engines, but there are still issues to be addressed, such as the low-load thermodynamic efficiency and nitrogen oxide emissions. In particular, it is highly desirable to reduce NOx directly in the combustion chamber in order to avoid expensive after-treatment systems. This study analyzed the influence of the combustion system, especially the piston bowl geometry and the injector nozzle, on the performance and emissions of a dual-fuel diesel-biogas engine designed for micro-cogeneration (maximum electric power: 50 kW). In detail, four different cylindrical piston bowls characterized by radii of 23, 28, 33 and 38 mm were compared with a conventional omega-shaped diesel bowl. Moreover, the influence of the injector tip position and the jet tilt angle was analyzed over ranges of 2-10 mm and 30-120 degrees, respectively. The goal of the optimization was to find a configuration that was able to reduce the amount of NOx while maintaining high values of brake thermal efficiency at all the engine operating conditions. For this purpose, a 3D-CFD investigation was carried out by means of a customized version of the KIVA-3V code at both full load (BMEP = 8 bar, 3000 rpm, maximum brake power) and partial load (BMEP = 4 bar, 3000 rpm). The novelty of the study consisted of the parametric approach to the problem and the high number of investigated parameters. The results indicated that the standard design of the piston bowl yielded a near-optimal trade-off at full load between the thermodynamic efficiency and pollutant emissions; however, at a lower load, significant advantages could be found by designing a deeper cylindrical bowl with a smaller radius. In particular, a new bowl characterized by a radius of 23 mm was equivalent to the standard one at BMEP = 8 bar, but it yielded a NOx-specific reduction of 38% at BMEP = 4 bar with the same value of BTE.

2023 - Combustion Optimization of a Premixed Ultra-Lean Blend of Natural Gas and Hydrogen in a Dual Fuel Engine Running at Low Load [Articolo su rivista]
Rinaldini, Carlo Alberto; Scrignoli, Francesco; Savioli, Tommaso; Mattarelli, Enrico
abstract

2023 - Exploring the Potential of Hydrogen Opposed Piston Engines for Single-Cylinder Electric Generators: A Computational Study [Relazione in Atti di Convegno]
Volza, Antonello; Scrignoli, Francesco; Caprioli, Stefano; Mattarelli, Enrico; Rinaldini, Carlo Alberto
abstract

2023 - High Performance and Near Zero Emissions 2-Stroke H 2 Engine [Relazione in Atti di Convegno]
Caprioli, Stefano; Volza, Antonello; Mattarelli, Enrico; Rinaldini, Carlo Alberto
abstract

2023 - Influence of E85 on performance and efficiency of a motorcycle engine [Relazione in Atti di Convegno]
Di Gaetano, C; Volza, A; Caprioli, S; Scrignoli, F; Rinaldini, C A
abstract

2023 - Numerical optimization of supercharging and combustion on a two-stroke compression ignition aircraft engine [Articolo su rivista]
Mattarelli, Enrico; Caprioli, Stefano; Rinaldini, Carlo Alberto; Scrignoli, Francesco; Sparaco, Domenico; Caso, Paolo
abstract

Two-Stroke (2S) Compression Ignition (CI) engines have been used in aviation since World War II, for their excellent fuel efficiency and lightweight construction. In a modern light aircraft, these advantages still remain, along with the capability to run on jet fuel instead of gasoline. However, the design of these engines must be deeply revised, in order to incorporate the recent technologies, and it must be optimized with the support of CAE tools. The paper presents a CFD optimization of a turbocharged 2S CI 5.6 L flat-six aircraft engine developed by CMD. The scavenging system is of the Uniflow type, with exhaust poppet valves and a set of piston-controlled ports along the cylinder liner. Two mechanical superchargers are serially connected to the turbochargers. The crankshaft can be directly coupled to the propeller, thanks to its excellent balance and the relatively low maximum engine speed (2600 rpm). Differently from previous papers published on the same engine, the current study is focused on two crucial design topics: the optimization of the supercharging system and of the injection strategy. A customized version of KIVA-3V is used for the 3D-CFD cylinder analyses, while a commercial 1D-CFD code is employed to model the whole engine. The study is supported by a comprehensive experimental campaign, that permitted the accurate calibration of the numerical models. In comparison to any Four-Stroke delivering the same maximum power (400 HP at 2600 rpm, sea level), the analyzed engine is very light (about 220 kg), and efficient (211 g/kWh at typical cruise conditions). Despite the high performance, peak cylinder pressure and turbine inlet temperature at sea level are relatively low: 125 bar, 850 K. At rated power (360 HP@2400 rpm, sea level) combustion is complete and smoke-less, thanks to the optimization of the injection strategy, supported by the previous CFD analysis. The engine can operate at altitudes as high as 5500 m (18,000 feet), still delivering 270 HP at 2400 rpm, without relevant reduction of fuel efficiency. The key for the performance at high altitudes is the choice of the turbocharger considering the compressor choke limit easly reachable at high altitudes.

2022 - 2‐Stroke RCCI Engines for Passenger Cars [Articolo su rivista]
Mattarelli, E.; Rinaldini, C. A.; Marmorini, L.; Caprioli, S.; Legrottaglie, F.; Scrignoli, F.
abstract

Reactivity Controlled Compression Ignition (RCCI) is one of the most promising solutions among the low temperature combustion concepts, in terms of thermal efficiency and pollutant emissions. However, for values of brake mean effective pressure higher than 10 bar, in‐cylinder peak pressure rise rates tend to be too high, limiting the specific power of any 4‐Stroke (4S) engine. Such a limitation can be canceled by moving to the 2‐Stroke (2S) cycle. Among many alternatives, the “Uniflow” scavenging system with exhaust poppet valves on the cylinder head allows the designer to reproduce the same identical combustion patterns of a 4‐stroke RCCI engine, while increasing the indicated power output. The goal of the paper is to explore the potential of a 2‐stroke RCCI engine, on the basis of a comprehensive experimental campaign carried out on a modified automotive 2.0 L, 4‐stroke, four‐cylinder, four‐valve diesel engine. The developed prototype can run with one cylinder operating in 4‐stroke RCCI mode (gasoline–diesel), while the others work in the standard diesel mode. A One Dimensional‐Computational Fluid Dynamics (1D‐CFD) model has been built to predict the performance of the same prototype, when operating all four cylinders in RCCI mode. In parallel, an equivalent 2‐stroke RCCI virtual engine has been developed, by means of 1D‐CFD simulations and empirical assumptions. A numerical comparison between the 4S and the 2S engines is finally presented, in terms of performance and emissions at full load. The study demonstrates that a 2S RCCI engine can maintain all of the advantages of the RCCI combustion, strongly reducing the penalization in terms of performance, in comparison to a standard 4S diesel engine.

2022 - Development of a Combustion System for a New Generation of 2-Stroke Spark Ignition Engines [Relazione in Atti di Convegno]
Scrignoli, Francesco; Mattarelli, Enrico; Rinaldini, Carlo; Savioli, Tommaso
abstract

2022 - Influence of H2 enrichment for improving low load combustion stability of a Dual Fuel lightduty Diesel engine [Articolo su rivista]
Mattarelli, E.; Rinaldini, C.; Caprioli, S.; Scrignoli, F.
abstract

Dual Fuel (DF) combustion can help to reduce the environmental impact of internal combustion engines, since it may provide excellent Brake Thermal Efficiency (BTE) combined with ultra-low emissions. This technique is particularly attractive when using biofuels, or fuels with a low Carbon content, such as Natural Gas (NG). Unfortunately, as engine load decreases and the homogeneous NG-air mixture tends to become very lean, the high chemical stability of NG can be a serious obstacle to the completion of combustion. As a result, BTE drops and UHC and CO emissions become very high. A possible way to address this problem could be the addition of hydrogen (H2) to the NG-air mixture. In this paper, a numerical study has been carried out on an automotive Diesel engine, modified by the authors in order to operate in both conventional Diesel combustion and DF NG-diesel mode. A previous experimental characterization of the engine is the basis for the CFD-3D modeling and calibration of the DF combustion process, using a commercial software. The effects on combustion stability and emissions of different NG-H2 mixtures (six blends with 5%, 10%, 15%, 20%, 25%, and 30% by volume of hydrogen) are numerically investigated at a low load (BMEP = 2 bar, engine speed 3000 rpm). The results of the CFD-3D simulations demonstrate that NG-H2 blends are able to decrease strongly CO, UHC, and CO2 emissions at low loads. Advantages are also found in terms of thermal efficiency and NOx emissions.

2022 - Numerical Investigation of Dual Fuel Combustion on a Compression Ignition Engine Fueled with Hydrogen/Natural Gas Blends [Articolo su rivista]
Scrignoli, Francesco; Vecchio, Filippo; Legrottaglie, Francesco; Mattarelli, Enrico; Rinaldini, Carlo Alberto
abstract

The present work aims to assess the influence of the composition of blends of hydrogen (H2) and Natural Gas (NG) on Dual Fuel (DF) combustion characteristics, including gaseous emissions. The 3D-CFD study is carried out by means of a customized version of the KIVA-3V code. An automotive 2.8 L, 4-cylinder turbocharged diesel engine was previously modified in order to operate in DF NG-diesel mode, and tested at the dynamometer bench. After validation against experimental results, the numerical model is applied to perform a set of combustion simulations at 3000 rpm-BMEP = 8 bar, in DF H2/NG-diesel mode. Different H2-NG blends are considered: as the H2 mole fraction varies from 0 vol% to 50 vol%, the fuel energy within the premixed charge is kept constant. The influence of the diesel Start Of Injection (SOI) is also investigated. Simulation results demonstrate that H2 enrichment accelerates the combustion process and promotes its completion, strongly decreasing UHC and CO emissions. Evidently, CO2 specific emissions are also reduced (up to about 20%, at 50 vol% of H2). The main drawbacks of the faster combustion include an increase of in-cylinder peak pressure and pressure rate rise, and of NOx emissions. However, the study demonstrates that the optimization of diesel SOI can eliminate all aforementioned shortcomings.

2021 - Application to micro-cogeneration of an innovative dual fuel compression ignition engine running on biogas [Articolo su rivista]
Legrottaglie, F.; Mattarelli, E.; Rinaldini, C. A.; Scrignoli, F.
abstract

Renewable sources and enhancement of energy conversion efficiency are the main paths chosen by the European Community to stop climate changes and environmental degradation, and to enable a sustainable growth. For this purpose, the construction of a new and more dynamic electricity distribution network is mandatory. This “smart grid” should also include small and medium-size companies, able to program the generation and use of energy from renewable sources (the so-called "prosumers"). In this frame, micro-cogeneration (rated electric power up to 50 kW) is one of the most promising techniques. In this work, the application to micro-cogeneration of an innovative Compression Ignition internal combustion engine, operated in Dual Fuel mode is proposed. Thanks to the specific combustion system (Reactivity Controlled Compression Ignition, RCCI: a lean homogenous mixture of air and biomethane or biogas is ignited by the injection of a small amount of Diesel fuel), brake thermal efficiency can be increased at all operating conditions, compared to a conventional Spark Ignition engine running on biomethane or biogas. The ensuing reduction of CO2 emissions is higher than 20%. Furthermore, the proposed engine can tolerate larger variations in the composition of the biogas, without a significant drop of thermal efficiency. Finally, in case of emergency, it is able to run on Diesel fuel only. The use of the engine is particularly suitable for a company operating in the agricultural field, such as a mid-size farm, that is able to produce biogas for its self-consumption. Therefore, a representative study case is selected, and the corresponding electrical and thermal energy needs are analysed throughout a typical year. The energetic analysis leads to the identification of the most suitable engine size and calibration settings, in order to reduce the purchase of electricity and natural gas, maximizing the use of the company's own renewable sources (biogas or biomethane). The final goal of the optimization process is to create a virtuous system, that can reduce the environmental impact and make the company almost independent from the energetic point of view.

2021 - Design of a Novel 2-Stroke SI Engine for Hybrid Light Aircraft [Relazione in Atti di Convegno]
Caprioli, S.; Rinaldini, C.; Mattarelli, E.; Savioli, T.; Scrignoli, F.
abstract

The trend of powertrain electrification is quickly spreading from the automotive field into many other sectors. For ultra-light aircraft, needing a total installed propulsion power up to 150 kW, the combination of a specifically developed internal combustion engine (ICE) integrated with a state-of-the-art electric system (electric motor, inverter and battery) appears particularly promising. The dimensions and weight of ICE can be strongly reduced (downsizing), so that it can operate at higher efficiency at typical cruise conditions; a large power reserve is available for emergency maneuvers; in comparison to a full electric airplane, the hybrid powertrain makes possible to fly at zero emissions for a much longer time, or with a much heavier payload. On the other hand, the packaging of a hybrid powertrain into existing aircraft requires a specific design of the thermal engine, that must be light, compact, highly reliable and fuel efficient. The last aspect has a direct impact on the performance of the aircraft, since the mission range depends on the capacity of the fuel tanks, which, in turn, is limited by the aircraft total weight. The two-stroke cycle engine is far from a novelty for ultra-light aircraft; unfortunately, the specific fuel consumption and pollutant emissions of the conventional engines is quite high, in comparison to their 4-Stroke (4S) counterparts. The aim of the project presented in this paper is to develop a new type of 2-Stroke SI engine, able to match lightness, fuel efficiency and low pollutant emissions at a reasonable cost. The proposed ICE weights less than 60 kg, it delivers 110 kW@6000 rpm, along with a brake specific fuel consumption lower than 260 g/kWh in all the most relevant operating conditions. The paper describes the design of the new engine, with particular attention to the optimization of the scavenging system (without poppet valves) and the design of a low pressure direct injection system. The process is supported by CFD 1D and 3D simulations. As far as the design of the injection system is concerned, the main goal was to obtain a fuel trapping ratio higher than 95%, along with a properly stratified charge at combustion onset, when considering the most critical operating condition (maximum engine speed and load). The main optimized parameters include the number of injectors, their locations, the injection timing and duration.

2021 - Optimization of a High-Speed Dual-Fuel (Natural Gas-Diesel) Compression Ignition Engine for Gen-sets [Articolo su rivista]
Mattarelli, E.; Rinaldini, C. A.; Savioli, T.; Scrignoli, F.
abstract

The goal of this study is to develop a clean and efficient thermal unit for a generator set (gen-set) rated at 80 kW, exploring the potential of Dual-Fuel (DF) combustion (Natural Gas-Diesel) on high-speed Compression Ignition (CI) engines. Typically, the most comparable commercial gen-sets are made up of Heavy-Duty (HD) Diesel engines, whose cost and complexity will probably increase to meet more stringent emissions standards. The conversion of a light-duty Diesel engine may permit to match the high efficiency of Diesels with the low emissions of DF combustion at an affordable cost. Moreover, the new thermal unit would be more compact and lighter. Running on Natural Gas (NG) is less expensive than using Diesel fuel, and it offers more opportunities to reduce the environmental impact (e.g., NG can be easily obtained from biomass, in the same site where the gen-set is installed). Last but not the least, in case of interruption of NG supply, the system can be easily switched to conventional Diesel operation, offering a higher fuel flexibility. Despite the large number of scientific publications concerning DF engines, very few of them consider high-speed units equipped with modern Common Rail injection systems. Even more limited are the investigations on the combustion process at medium-high loads (BMEP > 10 bar), carried out by measuring in-cylinder pressure and optimizing all the fundamental control parameters (injection strategy for both Diesel fuel and NG, boost pressure, EGR rates, etc.). It should be observed that the use of state-of-the-art injection systems and the accurate calibration of their parameters at each operating condition is the only way to maximize the benefits of NG in terms of reduction of soot emissions while addressing the well-known issues related to the increase of some pollutants (HC, CO, and NOx). This study reviews the results of a theoretical and experimental activity carried out on a four-cylinder, Common Rail, 2.8-liter turbocharged Diesel engine. A gas injection system is installed upstream of the intake plenum, and an open Electronic Control Unit (ECU) is used to calibrate all the most important engine parameters. Thanks to the deep insight into the combustion process provided by in-cylinder pressure analysis and measurement of pollutant emissions, the study presents some general guidelines for setting the control strategy in this type of DF engine. Considering the operating condition at maximum power (BMEP = 12 bar, 3000 rpm, brake power = 83 kW), the following advantages are observed with comparison to the standard Diesel engine: soot is more than halved, NOx emissions are reduced by 32% and CO2 by 31%, and Brake Thermal Efficiency (BTE) increases from 35.8% to 39%. The only drawback is the increase of one order of magnitude of both CO and HC, requiring a specific oxidation catalyst. Another outcome of the study is the limitation on the use of DF NG-Diesel combustion at low loads: the experimental activity demonstrates that it is very difficult to achieve complete combustion of an ultra-lean air-NG premixed charge so that BTE tends to drop. At these conditions, it appears to be more convenient to switch back to standard Diesel operations.

2020 - Effects of humidified enriched air on combustion and emissions of a diesel engine [Articolo su rivista]
Pirola, C.; Galli, F.; Rinaldini, C. A.; Manenti, F.; Milani, M.; Montorsi, L.
abstract

The potential of Humidified Enriched Air (HEA) on Diesel engine combustion is investigated, by means of 3D CFD combustion simulations, on a current production 4-cylinder turbocharged Diesel engine. HEA is supposed to be obtained by water degassing operation, exploiting the different vapor-liquid equilibria of it main constituents, nitrogen and oxygen. Simulations are carried out using a customized version of the KIVA 3V code, featuring a detailed chemistry combustion mechanism. The model of the engine is previously validated through comparison with experimental data and then it is used to analyse combustion and emissions of HEA combustion in combination with late injection strategies. Numerical results demonstrate that oxygen-enriched air enhances the thermal efficiency of the engine (up to 13%) and reduces significantly soot emissions; on the other hand, in-cylinder peak pressure and NOx emissions increase. The latter can be significantly reduced by using humidified air maintaining the advantage in terms of thermal efficiency and in soot reduction, nevertheless the baseline case NOx emissions cannot be restored.

2020 - Parametric Study on Electric Turbocharging for Passenger Cars [Relazione in Atti di Convegno]
Mattarelli, E.; Scrignoli, F.; Rinaldini, C. A.
abstract

The motor generator unit installed on the turbocharger shaft (MGU-H) provides a fundamental contribution to the amazing performances and efficiency of the last Formula 1 power units. The excess of exhaust gas energy - normally dumped through the waste-gate - can be converted into electric energy and used to push the car, by means of a second motor generator unit installed on the engine crankshaft (MGU-K). The goal of this paper is to assess pros and cons of the MGU-H technology when applied to a family of engines of different displacement, installed on a typical passenger car. The influence of engine size and cylinders layout is investigated, under the same set of hypotheses, considering both transient and steady engine operations. The baseline engine is a commercial 2.0 L, SI, 4-cylinder in-line, rated at 200 HP at 4500-5000 rpm. The study considers the following other SI configurations: a) 1.5L, 3-cylinder in-line, 150 HP; b) 3.0L, V6, 300 HP; c) 4.0L, V8, 400 HP; d) 6.0L, V12, 600 HP. It is assumed that all the 5 engines have the same unit displacement and the same maximum load, expressed in terms of brake mean effective pressure as a function of rotational speed. The study is carried out using an experimentally calibrated GT-Power model of the baseline engine, and considering the same class C vehicle. A Matlab/Simulink model is also developed for the analysis of the WLTP driving cycle. The study demonstrates that the MGU-H technology can be conveniently applied to all the considered engines. The maximum advantage in terms of fuel saving on a driving cycle is obtained on the smallest. However, in the V6, V8 and V12 configurations, the installation of one electric turbocharger instead of two, strongly simplifies the engine layout, and it allows the designer to find some space for additional powertrain components, such as electric motors, battery packs, etc. Moreover, the elimination of the turbo-lag problem, gives the designer much more freedom, enabling the adoption of more fuel efficient engine settings.

2019 - Combustion analysis of a light duty diesel engine using oxygen-enriched and humidified combustion air [Relazione in Atti di Convegno]
Pirola, C.; Rinaldini, C. A.; Galli, F.; Manenti, F.; Milani, M.; Montorsi, L.
abstract

The present work presents the results of 3D CFD combustion simulations of a current production 4-cylinder turbocharged Diesel engine using oxygen-enriched and humidified combustion air. Enriched Air (EA) is supposed to be produced by desorption from water, exploiting the different Henry constants of N2 and O2. Simulation results show that EA permits to increase the engine thermal efficiency (up to 10%) and drastically reduces soot emissions but increases in-cylinder peak pressure and NOx emissions. Combustion air humidification helps to reduce NOx increment, without losing the advantage in terms of thermal efficiency and in soot reduction, even if NOx emissions cannot be reported to the base case values.

2019 - Design of a Hybrid Power Unit for Formula SAE Application: Packaging Optimization and Thermomechanical Design of the Electric Motor Case [Articolo su rivista]
Mangeruga, V.; Giacopini, M.; Barbieri, S. G.; Berni, F.; Mattarelli, E.; Rinaldini, C.
abstract

This paper presents the development of a parallel hybrid power unit for Formula SAE application. In particular, the system is made up of a brand new, single-cylinder 480 cc internal combustion engine developed on the basis of the Ducati "959 Superquadro" V90 2-cylinders engine. The thermal engine is assisted by a custom electric motor (30 kW), powered by a Li-Ion battery pack. The performance of the ICE has been optimized through CFD-1D simulation (a review of this activity is reported in a parallel paper). The main design goal is to get the maximum amount of mechanical energy from the fuel, considering the car typical usage: racing on a windy track. The Ducati "959 Superquadro" engine is chosen because of its high power-to-weight ratio, as well as for its V90 2-cylinder layout. In fact, the vertical engine head is removed and it is subsequently replaced by the electric motor directly engaged to the crankshaft using the original valvetrain transmission chain, thus achieving a very compact package. The mechanical behaviour of the original chain is investigated for this purpose. A specific electric motor case is then designed and manufactured via Additive Manufacturing technology, in order to include the chain housing, the electric motor cooling system and the lubrication system. Furthermore, the case flange is designed to perfectly fit to the original engine deck in order to allow the engine cooling circuit to match with the electric motor cooling circuit. Several types of circuit layout - around the stator - are analysed via CFD simulations comparing pressure drop and heat transfer coefficients. Finally, a thermo-structural analysis is performed in order to assess the mechanical strength of the electric motor case.

2019 - Development of a Hybrid Power Unit for Formula SAE Application: ICE CFD-1D Optimization and Vehicle Lap Simulation [Relazione in Atti di Convegno]
Mattarelli, E.; Rinaldini, C. A.; Scrignoli, F.; Mangeruga, V.
abstract

The paper reviews the CFD optimization of a motorcycle engine, modified for the development of a hybrid powertrain of a Formula SAE car. In a parallel paper, the choice of the donor engine (Ducati 959 Panigale: 2-cylinder, V90, 955 cc, peak power 150 HP at 10500 rpm, peak torque 102 Nm at 9000 rpm) is thoroughly discussed, along with all the hardware modifications oriented to minimize the new powertrain dimensions, weight and cost, and guarantee full reliability in racing conditions. In the current paper, the attention is focused on two main topics: 1) CFD-1D tuning of the modified Internal Combustion Engine (ICE), in order to comply with the Formula SAE regulations, as well as to maximize the power output; 2) simulation of the vehicle in racing conditions, comparison with a conventional combustion car and a full electric vehicle. The stock engine has been strongly modified, since the head of the vertical cylinder has been replaced by the electric motor, and the intake system of the other cylinder now includes a 20 mm restrictor. Despite these constraints, the tuned ICE is able to deliver more than 70 HP. Finally, the study shows that the hybrid car is not only more efficient (-26% of specific CO2), but also 1.48 s faster on each lap than the corresponding Combustion single seater.

2019 - Dual Fuel (Natural Gas Diesel) for Light-Duty Industrial Engines: A Numerical and Experimental Investigation [Capitolo/Saggio]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; Savioli, Tommaso
abstract

This paper reviews the main results of a numerical and experimental activity, carried out on an automotive four-cylinder, common rail, 2.8 L turbocharged diesel engine, Euro IV compliant. The purpose of the project is to convert this engine, with minor hardware modifications, in order to operate in compression ignition (CI) dual-fuel (DF) mode, using natural gas (NG) as the main source of energy. The diesel injector will keep the only function to ignite the homogeneous air–NG mixture within the cylinder, injecting just a small quantity of diesel fuel. In this way, soot emissions can be almost completely eliminated, and the after-treatment system can be strongly simplified (then, its cost reduced). Other fundamental advantages in the use of NG instead of diesel are the lower emission of CO2 (provided that brake efficiency is not reduced when running on DF) and the lower concentration of nitrogen oxides (NOx). This DF engine would be particularly suitable for light-duty industrial applications (power generators, small tractors, and off-road vehicles) and boats, where the installation of an additional fuel system is not limited by tight constraints. The experimental activity is supported by a comprehensive theoretical study, carried out through CFD simulation (both 1D and 3D). The numerical models are first calibrated for the standard combustion mode and then applied to get the guidelines for the development and calibration of the physical prototype. The most relevant experimental result is obtained at 3000 rpm, BMEP = 12 bar, where the DF engine can work with just a 20% of the diesel fuel required for standard operations. The following advantages are found: (1) complete elimination of soot; (2) 26% reduction of NOx; (3) 25% reduction of CO2; (4) slight improvement of brake efficiency. The only downside is the strong increase in HC and CO concentrations, which are about ten times higher. However, this issue can be addressed installing a cost-effective oxidation catalyst.

2019 - Experimental investigation on a diesel engine operated in RCCI combustion mode [Relazione in Atti di Convegno]
Legrottaglie, F.; Mattarelli, E.; Rinaldini, C. A.; Savioli, T.; Scrignoli, F.
abstract

Low Temperature Combustion (LTC) concepts have been investigated in many recent studies, aiming to improve engine efficiency and minimize pollutant emissions. One of the most promising techniques is represented by the Reactivity Controlled Compression Ignition (RCCI), that can be obtained combining a low reactivity fuel (such as gasoline, natural gas, ethanol, etc) and a high reactivity fuel (such as Diesel oil). The former is injected in the intake manifold, and it generates a homogeneous mixture before the start of combustion; the latter is injected directly into the combustion chamber. This technology can be easily applied to existent Diesel engines, implementing a low pressure injection system for the low-reactivity fuel. This work presents the most important results of a preliminary experimental study, conducted on a light duty Diesel engine, modified in order to operate in RCCI combustion mode. In particular, four gasoline injectors have been installed between the intercooler and the intake plenum, while the injection strategy of both fuels has been optimized, along with boost pressure. Experiments show that at low loads it is possible to substitute most of Diesel fuel with gasoline, maintaining or even improving brake thermal efficiency. This result was obtained by optimizing the Diesel fuel injection strategy, without the support of EGR. However, at medium loads, it was not possible to achieve relevant reductions of Diesel fuel, due to the high risk of knocking.

2019 - Modeling and optimization of industrial internal combustion engines running on Diesel/syngas blends [Articolo su rivista]
Rinaldini, Carlo Alberto; Allesina, Giulio; Pedrazzi, Simone; Mattarelli, Enrico; Tartarini, Paolo
abstract

The paper presents a numerical analysis of combustion, carried out on a compression ignition indirect injection engine fueled by both Diesel and syngas, the latter obtained from biomass gasification and introduced in the intake manifold. The computational fluid dynamics model includes an improved chemical kinetics scheme, tailored on the syngas-diesel dual fuel combustion. The model was validated by an experimental campaign, on the same engine. The syngas fuel was produced by a small scale gasifier running on wood chips. Several simulations were performed varying both the share of syngas and the Diesel start of injection angle. The total amount of heat released by combustion can increase up to 50%, along with the indicated work and the cylinder peak pressure. The start of injection angle should be modified in order to preserve the mechanical integrity of the engine, as well as to maximize its brake efficiency. The numerical analysis provides the guidelines for setting the injection strategy, as a function of the syngas share.

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 - Potential of Electrification Applied to Non-Road Diesel Engines [Relazione in Atti di Convegno]
Mattarelli, E.; Rinaldini, C. A.; Scrignoli, F.; Fregni, P.; Gaioli, S.; Franceschini, G.; Barater, D.
abstract

The new Stage 5 European regulation for Non Road Mobile Machinery has lowered the limits on pollutant emissions for all the categories of internal combustion engines. An interesting alternative to the implementation of sophisticated after-treatment systems is to downsize the engine, and provide the extra power for peak demands with an electric motor, installed in place of the flywheel. The paper explores the potential of this concept, applied to an industrial engine, manufactured by Kohler, and delivering a maximum power of 56 kW@2600 rpm. The study is supported by a comprehensive experimental characterization of the internal combustion engine and of the electric components. A representative duty cycle is also defined, on the basis of a set of measures, taken in real operating conditions. The analysis of this reference cycle is performed by using a GT-Suite model, comparing different power split strategies. It is found that the ICE total displacement can be reduced from 2.5 to 1.9 L (from 4 to 3 cylinders), without any penalization on powertrain performance and weight. A relevant reduction of soot (22%) and NOx (16%) emissions is observed, along with a slight reduction of fuel consumption.

2018 - An Innovative Hybrid Powertrain for Small and Medium Boats [Relazione in Atti di Convegno]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; Savioli, Tommaso; Warey, Alok; Gopalakrishnan, Venkatesh; Potter, Michael
abstract

Hybridization is a mainstream technology for automobiles, and its application is rapidly expanding in other fields. Marine propulsion is one such field that could benefit from electrification of the powertrain. In particular, for boats to sail in enclosed waterways, such as harbors, channels, lagoons, a pure electric mode would be highly desirable. The main challenge to accomplish hybridization is the additional weight of the electric components, in particular the batteries. The goal of this project is to replace a conventional 4-stroke turbocharged Diesel engine with a hybrid powertrain, without any penalty in terms of weight, overall dimensions, fuel efficiency, and pollutant emissions. This can be achieved by developing a new generation of 2-Stroke Diesel engines, and coupling them to a state-of-the art electric system. For the thermal units, two alternative designs without active valve train are considered: opposed piston and loop scavenged engines. The design of the alternative engines is carried out through CFD simulations. The CFD has been calibrated and validated using experimental data from single-cylinder loop scavenged engine. The study demonstrates that the new Loop scavenged engine with a 23 kWh battery pack and an Opposed Piston design with a 15 kWh battery pack can meet the goals of the project while providing 5% and 10% fuel efficiency improvement at cruise conditions respectively, in comparison to the reference 4-stroke engine.

2018 - MOTORE A DUE TEMPI E A PISTONI CONTRAPPOSTI [Brevetto]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; Savioli, Tommaso
abstract

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.

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 - Commercial Vehicles: New Diesel Engine Concepts for Euro VI and beyond [Relazione in Atti di Convegno]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; Patroncini, Paolo
abstract

The paper presents a numerical investigation, aimed to explore the potential of 2-stroke Diesel engines, able to meet Euro VI requirements, for application to medium size commercial vehicles (power rate: 80 kW at 2600 rpm, max. torque 420 Nm from 1200 to 1400 rpm). The study is based on experimental performance of a highly developed 4-stroke engine. Two different designs are considered: Loop and Uniflow scavenging, the latter obtained through an opposed piston configuration. In both cases, no poppet valves are used, and the lubrication is provided by a 4-stroke-like oil sump. The study started with the development of a 4-stroke EURO VI engine, on the basis of a previous EURO IV version. A prototype of the new engine (named 430) was built and tested. The second phase of the study consisted in the comparison to the 2-stroke configurations, considering the same performance and emissions targets, as well as the same constraints Engine outputs are calculated by using GT-Power models: while for the 4-stroke unit these results are fully supported by experimental data, the 2-strokes are just "paper" engines. However, the CFD-1D modeling was supported by other detailed numerical simulations, including both scavenging and combustion analyses. The two stroke concepts analyzed in the paper appear to yield several advantages, in comparison to their 4-stroke counterpart: reduced fuel consumption, cleaner combustion conditions, more compact dimensions, higher flexibility of the EGR control. On the other hand, they require a strong effort for the development of a specific combustion system.

2017 - Design Of Two-Stage On/Off Cartridge Valves For Mobile Applications [Relazione in Atti di Convegno]
Zardin, Barbara; Borghi, Massimo; Cillo, Giovanni; Rinaldini, Carlo Alberto; Mattarelli, Enrico
abstract

Cartridge valves are widely used in mobile applications, where they are screwed in manifolds, to realize opportune circuit layouts. These valves are quite simple in operation but require a sophisticated design in order to meet all the requirements needed in the mobile machines. Typically, the design process is developed realizing a first design concept and some prototypes and experimentally testing them; after this, the designer chases the optimal performances requested to the valve with a trial and error approach on the prototypes, involving high time and cost resources. In this paper an alternative design procedure is proposed, which involves dedicated simulations to analyze the main critical issues regarding the cartridge valve object of the study. Modelling and simulations here have been considered as steps into the design process of a new valve, which satisfies the requirements and well adapt to the necessities to operate at higher flow and pressure levels without compromising its performances. In that way, the number of prototypes, realized to validate the numerical results and verify the design process, has been considerably reduced, together with related time and costs.

2017 - Design and experimental development of a compact and efficient range extender engine [Articolo su rivista]
Borghi, Massimo; Mattarelli, Enrico; Muscoloni, Jarin; Rinaldini, Carlo Alberto; Savioli, Tommaso; Zardin, Barbara
abstract

The paper reviews the design and experimental development of an original range-extender single-cylinder two-stroke gasoline engine, rated at 30 kW (maximum engine speed: 4500 rpm). The goal of the project is to get most of the benefits of the two-stroke cycle (compactness, high power density, low cost), while addressing the typical issues affecting the conventional engines of this type. Among many recent similar propositions, the peculiarities of this engine, besides the cycle, are: external scavenging by means of an electric supercharger, piston controlled scavenge and exhaust ports (no poppet valves), gasoline direct injection (GDI), and a patented rotary valve for the optimization of the scavenging process, of the loop type. Lubrication is identical to a conventional four-stroke engine, and the rotary valve, connected to the crankshaft, helps to improve the balance of the piston reciprocating forces, yielding an excellent NVH behavior. It should be noted that, except the patented rotary valve, all the engine parts are standard automotive commercial components, that don’t require any specific expensive technology. In fact, the originality of the engine consists in the optimum combination of existing well assessed concepts. The scavenging and combustion systems of the engine are developed in the first phase of the project, including the construction and the experimental testing of a prototype. In the second phase, the air metering system of the prototype is completely modified: the piston pump is replaced by an electric supercharger, and engine load is now controlled by the supercharger speed, without throttle valve. The new engine is compared to a standard 4-stroke engine, developed in a previous project for the same application. The main advantages of the two-stroke engine may be summarized as follows: lower weight (−35%), higher brake efficiency (+6%, on average), less heat rejected (−18%), lower thermal and mechanical loads within the cylinder (−40%). The only concern, that will be addressed in a future phase of the study, is the compliance with very low NOx limits: in the worst scenario, the 2-stroke engine could be forced to adopt a well assessed but expensive after-treatment device.

2017 - Experimental investigation on a Common Rail Diesel engine partially fuelled by syngas [Articolo su rivista]
Rinaldini, Carlo Alberto; Allesina, Giulio; Pedrazzi, Simone; Mattarelli, Enrico; Savioli, Tommaso; Morselli, Nicolo'; Puglia, Marco; Tartarini, Paolo
abstract

The high efficiency, reliability and flexibility of modern passenger car Diesel engines makes these power units quite attractive for steady power plants totally or partially running on fuels derived from biomass, in particular on syngas. The engine cost, which is obviously higher than that of current industrial engines, may not be a big obstacle, provided that the re-engineering work is limited and that performance and efficiency are enhanced. The goal of this work is to explore the potential of a current automotive turbocharged Diesel engine running on both Diesel fuel and syngas, by means of a comprehensive experimental investigation focused on the combustion process. The engine is operated at the most typical speed employed in steady power plants (3000 rpm), considering three different loads (50–100–300 Nm/16–31–94 kW). For each operating condition, the syngas rate is progressively increased until it provides a maximum heating power of 85 kW, while contemporarily reducing the amount of injected Diesel oil. Maximum care is applied to guarantee a constant quality of the syngas flow throughout the tests, as well as to maintain the same engine control parameters, in particular the boost pressure. It is found that in-cylinder pressure traces do not change very much, even when drastically reducing the amount of Diesel fuel: this is a very encouraging result, because it demonstrates that there is no need to radically modify the standard stock engine design. Another promising outcome is the slight but consistent enhancement of the engine brake efficiency: the use of syngas not only reduces the consumption of Diesel oil, but it also improves the combustion quality. The authors acknowledge that this study is only a starting basis: further investigation is required to cover all the aspects related to the industrial application of this syngas-Diesel combustion concept, in particular the impact on pollutant emission and on engine durability.

2017 - Pressure losses in hydraulic manifolds [Articolo su rivista]
Zardin, Barbara; Cillo, Giovanni; Rinaldini, Carlo Alberto; Mattarelli, Enrico; Borghi, Massimo
abstract

Hydraulic manifolds are used to realize compact circuit layout, but may introduce a high pressure drop in the system. Their design is in fact oriented more toward achieving minimum size and weight than to reducing pressure losses. This work studies the pressure losses in hydraulic manifolds using different methods: Computational Fluid Dynamic (CFD) analysis; semi-empirical formulation derived from the scientific literature, when available; and experimental characterization. The purpose is to obtain the pressure losses when the channels' connections within the manifold are not ascribable to the few classic cases studied in the literature, in particular for 90° bends (elbows) with expansion/contraction and offset intersection of channels. Moreover, since CFD analysis is used to predict pressure losses, general considerations of the manifold design may be outlined and this will help the design process in the optimization of flow passages. The main results obtained show how CFD analysis overestimates the experimental results; nevertheless, the numerical analysis represents the correct trends of the pressure losses.

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 - An Analytical Assessment of the CO2 Emissions Benefit of Two-Stroke Diesel Engines [Relazione in Atti di Convegno]
Warey, Alok; Gopalakrishnan, Venkatesh; Potter, Michael; Mattarelli, Enrico; Rinaldini, Carlo Alberto
abstract

Two-stroke diesel engines could be a promising solution for reducing carbon dioxide (CO2) emissions from light-duty vehicles. The main objective of this study was to assess the potential of two-stroke engines in achieving a substantial reduction in CO2 emissions compared to four-stroke diesel baselines. As part of this study 1-D models were developed for loop scavenged two-stroke and opposed piston two-stroke diesel engine concepts. Based on the engine models and an in-house vehicle model, projections were made for the CO2 emissions for a representative light-duty vehicle over the New European Driving Cycle and the Worldwide Harmonized Light Vehicles Test Procedure. The loop scavenged two-stroke engine had about 5-6% lower CO2 emissions over the two driving cycles compared to a state of the art four-stroke diesel engine, while the opposed piston diesel engine had about 13-15% potential benefit. Opposed piston two-stroke engines offer the potential for even higher thermal efficiency than loop scavenged two-stroke engines. The efficiency advantages of the opposed piston two-stroke engine are mainly because of lower in-cylinder heat losses due to elimination of the cylinder head and lower surface area to volume ratio. The thermal efficiency of a loop scavenged two-stroke engine can be potentially further improved by using thermal barrier materials for incylinder surfaces to minimize heat losses. Analytical studies show that integration of thermal barrier materials and two-stroke loop scavenged engine could lead to a cost effective highly efficient diesel engine. Whether the theoretical benefit translates to actual CO2 emissions reduction will have to be verified experimentally.

2016 - Comparison of Supercharging Concepts for SI Engine Downsizing [Relazione in Atti di Convegno]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; Agostinelli, Enrico
abstract

The paper reviews the design of the supercharging system for a strongly downsized engine, to be installed on a sport car. Design is supported by cfd-1d engine simulations, using an experimentally calibrated model. The goal of the supercharging system is to deliver the required values of boost pressure at steady operating conditions, and to maintain or improve the full size engine response during acceleration (one of the most critical issues for downsized engines). Two options have been considered: 1) two-stage turbocharging, with two small turbochargers as a high-pressure stage, and one big turbo as low pressure stage (referred to as "TRITURBO"; 2) two-stage supercharging made up of one low pressure stage turbocharger and one electric supercharger (referred to as "E-SUPER"). It was found that both configurations not only allow the downsized engine to comply with the performance targets at wide open throttle, steady conditions, but they are also able to improve the transient response in comparison to the full size engine. TRITURBO is less expensive than E-SUPER, but also less fuel efficient and more difficult to install on the vehicle.

2016 - Modified diesel engine fueled by syngas: Modeling and experimental validation [Relazione in Atti di Convegno]
Pedrazzi, Simone; Allesina, Giulio; Morselli, Nicolò; Puglia, Marco; Rinaldini, Carlo Alberto; Savioli, Tommaso; Mattarelli, Enrico; Giorgini, Loris; Tartarini, Paolo
abstract

Diesel engines are robust and reliable machine for stationary electrical energy production. In fact, these engines are designed to run continuously for thousands of hours and with low maintenance. However, several issues affect the application of syngas as fuel in this kind of engines. The full conversion from diesel to gas fuel need the presence of the spark plug instead of the diesel injection. Therefore, the high compression ratio in this kind of engines increase the possibility of the knocking phenomenon inside the combustion chamber. The knocking damages the engine mechanical structure and reduce the engine reliability. Several works set the limit of the compression ratio to 17 in order to overcome this issue. In addition, the velocity of the syngas combustion flame is higher compared to the diesel one as result to the presence of hydrogen in the syngas. This difference forces to reduce the spark ignition time from 0 to 15 ° in advance respect the Bottom Top Dead Center (BTDC) in order to limit the peak pressure inside the cylinders to the design value of the engine. Aim of this work is to compare results of a 0D mathematical model of a converted diesel engine with the results obtained in an experimental campaign. For the tests a Fiat Power Train (FPT) 4.5 liters commercial diesel engine converted to syngas is used. The model calculates the maximum power output of the engine at different rpm starting from syngas composition, airsyngas mixture temperature and diesel nominal power. The model takes into account the friction losses, air to fuel ratio and intake manifold pressure. Experimental tests were run on a gasification facility consisting in a fixed bed wood chip downdraft gasifier that generates syngas to fuel the FPT engine. The engine is connected to a MeccAlte generator for electrical power production. An Arduino based controller sets the position of the air valve in order to stabilize the lambda value of the exhaust of the engine to 1.05. A variable electrical load was applied and it was increased as long as the engine was able to drag the generator at 1500 rpm. During the tests, the following parameters were monitored: syngas volumetric flow rate and composition, syngas pollutants concentration (tar, particulate and water), air-gas mixture temperature and intake manifold pressure. An HT electrical circuit analyzer recorded the power output of the generator. Several tests were run at 1500 rpm varying the air-syngas mixture temperature and the intake manifold pressure and experimental results was compared to 0D model predictions. A good agreement of the model to experimental data was achieved. Syngas conversion reduces the maximum electrical power output of the engine generator from 49.7 kW to about 22 kW as result of the lower air-syngas mixture calorific value and density compared to diesel-air mixture. However, the engine mechanical efficiency is comparable using syngas or diesel fuel (about 30%) and pollutant emissions are strongly lower with syngas fuel.

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.

2016 - Port Design Criteria for 2-Stroke Loop Scavenged Engines [Relazione in Atti di Convegno]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; Savioli, Tommaso
abstract

Interest in 2-stroke engines has been recently renewed by several prototypes, developed for the automotive and/or the aircraft field. Loop scavenging, with piston controlled ports is particularly attractive, but the configurations successfully developed in the past for motorbike racing (in particular, the 125cc unit displacement, crankcase pump engines), are not suitable for automotive applications. Therefore, new criteria are necessary to address the scavenging system design of the new generation of 2-stroke automobile/aircraft engines. The paper reviews the transfer ports optimization of a loop scavenged 2-stroke cylinder, whose main parameters were defined in a previous study. The optimization has been carried by means of a parametric grid, considering 3 parameters (2 tilt angles, and the focus distance), and 3 different engine speeds (2000-3000-4000 rpm, assuming a Diesel engine). A set of scavenging CFD-3d simulations have been performed by using a customized version of KIVA-3V. The numerical approach was experimentally calibrated in a previous project (see appendix 1) The simulations results are presented by means of maps showing the influence of the geometrical parameters on the main scavenging coefficients. Finally, a refined mesh has been constructed for the optimum configuration found in the previous parametric analysis, and a set of multi-cycle simulations have been performed. The results demonstrated the very good efficiency of the scavenging process, close to a perfect displacement for delivery ratio up to 1.5, or for residuals fraction higher than 50%

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 - Combustion Analysis on an IDI CI Engine Fueled by Microalgae [Articolo su rivista]
Mattarelli, Enrico; Rinaldini, Carlo Alberto
abstract

The third generation of biodiesels, derived from microalgae, is one of the most interesting options for the replacement of fossil fuels. While the use of first generation biodiesels on different types of compression ignition engines is well documented in the open literature, much less information is available on algal fuels. As a matter of fact, the influence on combustion and pollutant emissions is not definitively assessed, depending on the combination of the specific features of both fuel and engine. The aim of this paper is to analyze the combustion process in a small industrial engine fueled by an algal Biodiesel, blended with standard Diesel fuel. The blend composition is the one typically used in most applications, i.e. 20% of biodiesel and 80% of Diesel (B20). In order to give a rigorous reference, all the experiments have been repeated with pure Diesel fuel, and with a blend made up of 20% of commercial rapeseed biodiesel, one of the most representative first generation biofuel. The experimental campaign has been carried out on an IDI 4-cylinder 1.4 liter naturally aspirated engine. It was found that the algal B20 slightly improves fuel conversion efficiency, in comparison to standard Diesel. This result is due to the different combustion rate, as well as to a more complete burning process. Differently from previous studies, no advantage has been found in terms of soot. Finally the algal B20 requires a higher fuel mass flow rate in order to compensate the lower heating value.

2015 - Combustion analysis of a diesel engine running on different biodiesel blends [Articolo su rivista]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; Savioli, Tommaso
abstract

Rape-seed biodiesel is an interesting option to address the problem of decreasing availability of conventional fossil fuels, as well as to reduce the CO2 emissions of internal combustion engines. The present paper describes an experimental campaign carried out on a current production 4-cylinder, 4-stroke naturally aspirated diesel engine, running on standard diesel fuel and on three different blends of rape-seed biodiesel (20%-50%-100%). Performance, emissions and in-cylinder pressure traces were measured at full load. It was found that the influence of rape-seed biodiesel in the fuel blend is not constant at each operating condition. However, as the biodiesel content increases, full load performance tends to drop, in particular brake specific fuel consumption (maximum worsening: +18%), while soot emission goes down. The maximum improvement observed in terms of soot concentration is 37.5%, at 1200 rpm. The combustion analysis revealed that the main differences among the fuels occur in the first phase of combustion: the burn rate is slower for biodiesel blends at low speeds, and faster at high.

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 - Digestate as bio-fuel in domestic furnaces [Articolo su rivista]
Pedrazzi, Simone; Allesina, Giulio; Belló, Tobia; Rinaldini, Carlo Alberto; Tartarini, Paolo
abstract

This study investigates the use of the biogas power plants byproduct (digestate) as biofuel in an ordinary domestic air furnace. The digestate, disposed by a 1 MW biogas plant located in Italy, was dried out and pelletized in order to be used as fuel in a wood pellet furnace with 29 kW(th) of nominal power, commonly installed in industrial HVAC systems. The first test was carried out starting from a heavily dried pellet called "digestate 0" characterized chemically and physically in order to obtain its composition, while its ashes were tested using an optical thermal dilatometer for the softening point evaluation. This first test outlined that the "digestate 0" pellets were not suitable for combustion applications even when mixed with an equal part of pure wood pellets. The research then focused on the raw digestate drying process through a set of physical and chemical tests. It was found that a temperature of 150 degrees C maximizes the higher heating value of the new "digestate 1" at 16.6 MJ/kg. However, to further avoid the ash sintering, "ultimate digestate" pellets were prepared mixing 50% of "digestate 1" and 50% of wood. The digestate obtained in such a way was experimentally tested through several runs of the air furnace. In these tests, the overall efficiency as well as the furnace emissions was measured.

2015 - Experimental-analytical evaluation of sustainable syngasbiodiesel CHP systems based on oleaginous crop rotation [Relazione in Atti di Convegno]
Allesina, Giulio; Pedrazzi, Simone; Rinaldini, Carlo Alberto; Savioli, Tommaso; Morselli, Nicolo'; Mattarelli, Enrico; Tartarini, Paolo
abstract

This work is aimed at investigating how the solutions adopted for the SRF (short rotational forestry) can be applied to oleaginous cultures for bioenergy production with a dual fuel diesel engine. The method is based on four sub-systems: a seed press for oil production, a downdraft gasifier, a biodiesel conversion plant and a dual fuel biodiesel IC engine for CHP (combined heat and power) production. The plant is analytically modeled except for the IC engine that was tested via experimental analysis. Results showed that, in the hypothesis of 8000 hours/year of power plant run, a surface of 27 hectares can supply enough syngas and biodiesel to run a CHP unit with nominal electrical power of 13.61 kW. Moreover, the experimental analysis outlined how the engine running with dual fuel is not almost affected by significant losses in its performance. Besides, the use of syngas yields strong benefits in terms of soot emissions (measured by an opacimeter), as well as in terms of brake fuel conversion efficiency.

2015 - Two-Stroke Gasoline Engines for Small-Medium Passenger Cars [Relazione in Atti di Convegno]
Mattarelli, Enrico; Rinaldini, Carlo Alberto
abstract

Among all the reciprocating internal combustion engines, gasoline two-strokes can reach the highest specific power, making this technology a natural enabler of downsizing and/or down-speeding. In addition, multi-cylinder 2-stroke engines may be an ideal match for electrical superchargers, providing very efficient power units. The paper explores through CFD-1d simulations and empirical hypotheses the potential of a 3-cylinder, 1.0 liter, GDI 2-stroke turbocharged engine featuring a patented rotary valve for the optimization of the scavenging process, the latter being of the loop type (piston-controlled ports). The lubrication system is the same of a 4-stroke engine (no crankcase pumps). The supercharging system is made up of a turbocharger and an electric compressor, serially connected. The power of the electric compressor is limited to 2 kW, in order to comply with standard automotive 12 V electric systems. The proposed engine easily achieves the goal of 95 kW at 4500 rpm, and 210 Nm at 1500 rpm, resulting also quite fuel efficient at any operating conditions (best point: 211 g/kWh, achieved with stratified charge).

2015 - Two-stage turbocharging for the downsizing of SI V-engines [Relazione in Atti di Convegno]
Rinaldini, Carlo Alberto; Breda, Sebastiano; Fontanesi, Stefano; Savioli, Tommaso
abstract

One of the most critical challenges for the specific power increase of turbocharged SI engines is the low end torque, limited by two aspects. First, the big size of the compressor necessary to deliver the maximum airflow does not allow high boost pressures at low speed, due to the surge line proximity. Second, the flame front velocity may become slower than the end gas auto-ignition rate, thus increasing the risk of knocking. This study is based on a current SI GDI V8 turbocharged engine, modeled by means of CFD tools, both 1d and 3d. The goal of the activity is to lower by 20% the displacement, without reducing brake torque, all over the engine speed range. It was decided to adopt a smaller bore, keeping stroke constant. Obviously, the combustion chamber, the valves and the intakeexhaust ports have been re-designed, as well as the whole intake and exhaust system. Instead of the two turbochargers, one for each bank of cylinders, a triple-turbocharger layout has been considered. The development of the engine has been carried out by means of 1D engine cycle simulations, using predictive knock models, calibrated with the support of both experiments and CFD-3d simulations. A few operating conditions for the final configuration have been also analyzed by means of a 3-d CFD tool. The paper presents the results of this activity, and describes in details the guidelines followed for the development of the engine.

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-3D Analysis of a Light Duty Dual Fuel (Diesel/Natural Gas) Combustion Engine [Relazione in Atti di Convegno]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; Valeri I., Golovitchev
abstract

Nowadays, the most critical issues concerning internal combustion engines are the reduction of the pollutant emissions, in particular of CO2, and the replacement of fossil fuels with renewable sources. An interesting proposition for Diesel engines is the Dual Fuel (DF) combustion, consisting in the ignition of a premixed charge of gaseous fuel (typically natural gas) by means of a pilot injection of Diesel Fuel. Dual fuel combustion is a quite complex process to model, since it includes the injection of liquid fuel, superimposed with a premixed combustion. However, CFD simulation is fundamental to address a number of practical issues, such as the setting of the liquid injection parameters and of the gaseous fuel metering, as well as to get the maximum benefit from the DF technique. In this paper, a customized version of the KIVA-3V Computational Fluid Dynamic (CFD) code was adopted to analyze the combustion process of a 4-cylinder, 2.8 l, turbocharged HSDI Diesel engine, operating in both Diesel and DF (Diesel and Natural Gas) modes. Starting from a previously validated diesel combustion model, a natural gas combustion model was implemented and added to simulate the DF operations. Available engine test data were used for validation of the diesel-only operation regimes. Using the calibrated model, the influence of the premixed charge composition was investigated, along with the effect of the diesel injection advance angle, at a few characteristic operating conditions. An optimum setting was eventually found, allowing the DF engine to deliver the same brake power of the original Diesel unit, yielding the same maximum in-cylinder pressure. It was found that DF combustion is soot-less, yields a strong reduction of CO and CO2, but also an increase of NO.

2014 - Experimental Investigation on Biodiesel from Microalgae as Fuel for Diesel Engines [Relazione in Atti di Convegno]
Rinaldini, Carlo Alberto; Mattarelli, Enrico; M., Magri; M., Beraldi
abstract

Biodiesel from Algae appears as an almost ideal solution to address the problem of decreasing availability of conventional fossil fuels, as well as to reduce the impact in terms of CO2 of internal combustion engines. In comparison to other biodiesels, algae do not compete for the land use with food cultures, and they have an excellent oil yield. Despite the significant amount of technical reports about the production process of algal biodiesel, detailed information about the application to current production engines is almost completely missing. The present paper describes the experimental campaign carried out on a current production 4-cylinder, 4-stroke naturally aspirated Diesel engine, running on standard Diesel oil and on a blend made up of 20% of oil manufactured by transesterification of Microalgae (B20). Performance and emission parameters have been measured over the whole engine operating range. It was found that the use of B20 leads to a very small decrease of full load performance (lower torque and higher specific fuel consumption), in front of a significant advantage in terms of Soot emissions, partly balanced by a higher NOx rate. No apparent difference has been observed in terms of NVH when running on the two fuels.

2014 - Modeling and Experimental Investigation of a 2-Stroke GDI Engine for Range Extender Applications [Relazione in Atti di Convegno]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; P., Baldini
abstract

The basic requirements for range extender engines are low cost, compact dimensions, high specific power, good efficiency, low pollutant emission levels, excellent NVH behavior. For a power rate lower than 30 kW, it is very difficult to find an off-the-shelf engine meeting all the requirements listed above, so that a new generation of dedicated engines is under development. Following a preliminary theoretical work presented in 2012, the current paper reviews the design process and the first experimental tests carried out on a novel 2-stroke GDI single-cylinder engine, rated at 30 kW at 4500 rpm, featuring a patented induction valve and a piston pump for scavenging. A prototype has been designed with the support of CFD simulations, then built and tested at the BRC laboratories, in Cherasco (Italy).

2013 - 2-Stroke Multipurpose Externally Scavenged Hi Efficiency Engines [Abstract in Atti di Convegno]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; Luca, Morfino
abstract

This work is related to debate on potential of the 2-Stroke concept applied to Range Extender engines, proposing 3 different configurations: 1) Supercharged, Compression Ignition; 2) Turbocharged, Compression Ignition; 3) Supercharged, Gasoline Direct Injection. All the engines feature a single power cylinder of 0.49l, external air feed by piston pump and an innovative induction system. The scavenging is of the Loop type, without poppet valves, and with a 4-Stroke like lubrication system (no crankcase pump). Engine design has been supported by CFD simulations, both 1D (engine cycle analysis) and 3D (scavenging, injection and combustion calculations). The strong points found for this family of engines are: high power density (up to 122 kW/l) and power to weight ratio; low raw emissions; compactness (design integrated with the electric motor); low production costs (no valvetrain, no EGR system); excellent balance of inertia forces (thanks to the piston pump installed on the same crankshaft, at 90° from the power cylinder); mechanical reliability (no exotic solutions, effective lubrication system); low noise (low engine speed thanks to the double frequency of the cycle); low specific fuel consumption. All those characteristics would be suitable for different application: steady generator, automotive, aviation, etc.

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 - Combustion Optimization of a Marine DI Diesel Engine [Relazione in Atti di Convegno]
Mattarelli, Enrico; Fontanesi, Stefano; Rinaldini, Carlo Alberto; G., Valentino; S., Iannuzzi; Severi, Elena; V., Golovitchev
abstract

Enhanced calibration strategies and innovative engine combustion technologies are required to meet the new limits on exhaust gas emissions enforced in the field of marine propulsion and on-board energy production. The goal of the paper is to optimize the control parameters of a 4.2 dm3 unit displacement marine DI Diesel engine, in order to enhance the efficiency of the combustion system and reduce engine out emissions. The investigation is carried out by means of experimental tests and CFD simulations. For a better control of the testing conditions, the experimental activity is performed on a single cylinder prototype, while the engine test bench is specifically designed to simulate different levels of boosting. The numerical investigations are carried out using a set of different CFD tools: GT-Power for the engine cycle analysis, STAR-CD for the study of the in-cylinder flow, and a customized version of the KIVA-3V code for combustion. All the models are calibrated through the above mentioned experimental campaign. Then, CFD simulations are applied to optimize the injection parameters and to explore the potential of the Miller combustion concept. It is found that the reduction of the charge temperature, ensuing the adoption of an early intake valve closing strategy, strongly affects combustion. With a proper valve actuation strategy, an increase of boost pressure and an optimized injection advance, a 40% reduction of NOx emissions can be obtained, along with a significant reduction of in-cylinder peak pressure, without penalizing fuel efficiency.

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 - Potential of the Miller cycle on a HSDI diesel automotive engine [Articolo su rivista]
Rinaldini, Carlo Alberto; Mattarelli, Enrico; Valeri I., Golovitchev
abstract

The paper explores, by means of CFD simulations, the potential of the Miller cycle, applied to High Speed Direct Injection (HSDI) Diesel engines, facing the challenge of emissions reduction enforced by the nearterm regulations, with particular reference to Euro VI. In fact, a valuable benefit of the Miller technique is the strong reduction of combustion temperature, thus the abating of NOx emissions, compared to a traditional cycle with the same values of AFR and EGR rate. The practical application of the Miller cycle yields a number of critical issues, which are generally addressed in the paper. However, the goal of the study is to assess the potential and the limits of this technique, more than develop a specific engine configuration. For the analysis, a 2.8 L 4-cylinder turbocharged engine produced by VM Motori was selected, carrying out a comprehensive experimental campaign, at both full and partial load. The experimental data allowed the authors to calibrate two types of numerical models, one for the whole engine analyses (0/1D), the other for the combustion process simulation (CFD-3D). The integrated use of these computational tools provides a reliable comparison between the base engine and the one modified according to the Miller cycle, in terms of both emissions and fuel consumption in the European Driving Cycle. It was found a reduction of NOx and Soot of 25% and 60%, respectively, and a worsening of fuel efficiency of 2%. The abating of NOx can be further enhanced, since it is demonstrated that the engine operated according to the Miller cycle can tolerate higher rates of EGR.

2013 - Virtual optimization of a 2-Stroke GDI Range Extender engine [Abstract in Atti di Convegno]
Mattarelli, Enrico; Rinaldini, Carlo Alberto
abstract

Virtual optimization of a 2-Stroke GDI Range Extender engine

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.

2012 - Development of a High Performance Engine for a Formula SAE Racer [Relazione in Atti di Convegno]
Mattarelli, Enrico; Rinaldini, Carlo Alberto
abstract

The paper reviews the theoretical and experimentaldevelopment of the engine powering the 2011 Formula SAEsingle seater of the University of Modena and Reggio Emilia(UNIMORE). The general design criteria followed by theUNIMORE team are discussed and compared to those chosenby other competitors. In particular, the reasons supporting theselection of the engine type (single cylinder by Husqvarna)are explained in details. The adoption of a single cylinder,instead of the more powerful four-in-line, required a muchbigger effort for getting an acceptable level of brake power.Therefore, the development was massively supported by CFDsimulation (both 1D and 3D) and by experiments. It wasfound that the most important design areas for the singlecylinder are: the intake system, including the restrictor (20mm), the intake runner and the plenum, and the muffler. GTPowerwas the main CFD tool used in the project: after theexperimental calibration of the base model, full loadsimulation have been carried out in order to optimize theengine geometric parameters, taking into account a number ofconstraints, decided by the team. The optimization goal wasnot just to have an engine as powerful as possible, but to findthe best package of both engine and vehicle.Besides full load steady calculations, also transient enginesimulations during a car acceleration have been performed.Engine-out noise was monitored too, in particular at thetesting conditions indicated by the competition rules.Finally, a complete performance characterization of theoptimized engine was predicted before starting the testing atthe dynamometer bed. These performance maps helped tospeed up the calibration process, and allowed the team also toget a rough estimation of the car fuel efficiency during theendurance event.

2011 - 2-Stroke High Speed Diesel Engines for Light Aircraft [Articolo su rivista]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; M. C., Wilksch
abstract

The paper describes a numerical study, supported by experiments, on light aircraft 2-Stroke Direct Injected Diesel engines, typically rated up to 110 kW (corresponding to about 150 imperial HP). The engines must be as light as possible and they are to be directly coupled to the propeller, without reduction drive. The ensuing main design constraints are: i) in-cylinder peak pressure as low as possible (typically, no more than 120 bar); ii) maximum rotational speed limited to 2600 rpm. As far as exhaust emissions are concerned, piston aircraft engines remain unregulated but lack of visible smoke is a customer requirement, so that a value of 1 is assumed as maximum Smoke number.For the reasons clarified in the paper, only three cylinder in line engines are investigated. Reference is made to two types of scavenging and combustion systems, designed by the authors with the assistance of state-of-the-art CFD tools and described in detail in a parallel paper. The former is a uniflow system, featuring two exhaust valves per cylinder in the engine head, piston controlled inlet ports and a combustion bowl in the piston; the latter is a loop scavenged design, with both inlet and exhaust ports controlled by the piston, and a non conventional combustion chamber in the engine head (no bowl in the piston). All the calculations presented in the paper are performed by using GT-Power models calibrated by means of CFD-3D calculations (by KIVA-3V) and experiments. The experimental support is provided by two engines: the former is a modern commercial aircraft 2-Stroke Diesel engine, indirect injected, uniflow scavenged; the latter is a research engine based on an old marine unit, featuring loop scavenging and direct injection. The calibration of the GT-Power models is reviewed in the paper.

2011 - 2-stroke high speed diesel engines for light aircraft [Relazione in Atti di Convegno]
Mattarelli, E.; Rinaldini, C. A.; Wilksch, M.
abstract

The paper describes a numerical study, supported by experiments, on light aircraft 2-Stroke Direct Injected Diesel engines, typically rated up to 110 kW (corresponding to about 150 imperial HP). The engines must be as light as possible and they are to be directly coupled to the propeller, without reduction drive. The ensuing main design constraints are: i) in-cylinder peak pressure as low as possible (typically, no more than 120 bar); ii) maximum rotational speed limited to 2600 rpm. As far as exhaust emissions are concerned, piston aircraft engines remain unregulated but lack of visible smoke is a customer requirement, so that a value of 1 is assumed as maximum Smoke number. For the reasons clarified in the paper, only three cylinder in line engines are investigated. Reference is made to two types of scavenging and combustion systems, designed by the authors with the assistance of state-of-the-art CFD tools and described in detail in a parallel paper. The former is a uniflow system, featuring two exhaust valves per cylinder in the engine head, piston controlled inlet ports and a combustion bowl in the piston; the latter is a loop scavenged design, with both inlet and exhaust ports controlled by the piston, and a non conventional combustion chamber in the engine head (no bowl in the piston). All the calculations presented in the paper are performed by using GT-Power models calibrated by means of CFD-3D calculations (by KIVA-3V) and experiments. The experimental support is provided by two engines: the former is a modern commercial aircraft 2-Stroke Diesel engine, indirect injected, uniflow scavenged; the latter is a research engine based on an old marine unit, featuring loop scavenging and direct injection. The calibration of the GT-Power models is reviewed in the paper. Copyright © 2011 SAE International.

2011 - CFD analyses on 2-Stroke High Speed Diesel engines [Articolo su rivista]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; V. A., Golovitchev
abstract

In recent years, interest has been growing in the 2-Stroke Diesel cycle, coupled to high speed engines. One of the most promising applications is on light aircraft piston engines, typically designed to provide a top brake power of 100-200 HP with a relatively low weight. The main advantage yielded by the 2-Stroke cycle is the possibility to achieve high power density at low crankshaft speed, allowing the propeller to be directly coupled to the engine, without a reduction drive. Furthermore, Diesel combustion is a good match for supercharging and it is expected to provide a superior fuel efficiency, in comparison to S.I. engines. However, the coupling of 2-Stroke cycle and Diesel combustion on small bore, high speed engines is quite complex, requiring a suitable support from CFD simulation. In this paper, a customized version of the KIVA-3v code (a CFD program for multidimensional analyses) has been used to address ports and combustion chamber design of a new project (a 3-cylinder 1.8L engine, with a power rating up to 150 HP). Multidimensional calculations have been supported by 1D engine cycle analyses, using GT-Power.Two types of combustion-scavenging system have been considered, both of them featuring direct injection: a configuration with exhaust poppet valves and another one with piston controlled ports. A development of both projects has been performed through a coupled 1d-3d computational approach.A first set of KIVA calculations has been performed, in order to characterize the scavenging and the port flow patterns of both configurations, considering three different operating conditions, representative an aircraft engine.Then, several combustion simulations have been run, for defining two chambers able to match the project goals (high fuel efficiency, limited in-cylinder peak-pressure). For the two best configurations, the most interesting calculation results are presented in the paper.

2011 - CFD analyses on 2-stroke high speed diesel engines [Relazione in Atti di Convegno]
Rinaldini, C. A.; Mattarelli, E.; Golovitchev, V.
abstract

In recent years, interest has been growing in the 2-Stroke Diesel cycle, coupled to high speed engines. One of the most promising applications is on light aircraft piston engines, typically designed to provide a top brake power of 100-200 HP with a relatively low weight. The main advantage yielded by the 2-Stroke cycle is the possibility to achieve high power density at low crankshaft speed, allowing the propeller to be directly coupled to the engine, without a reduction drive. Furthermore, Diesel combustion is a good match for supercharging and it is expected to provide a superior fuel efficiency, in comparison to S.I. engines. However, the coupling of 2-Stroke cycle and Diesel combustion on small bore, high speed engines is quite complex, requiring a suitable support from CFD simulation. In this paper, a customized version of the KIVA-3v code (a CFD program for multidimensional analyses) has been used to address ports and combustion chamber design of a new project (a 3-cylinder 1.8L engine, with a power rating up to 150 HP). Multidimensional calculations have been supported by 1D engine cycle analyses, using GT-Power. Two types of combustion-scavenging system have been considered, both of them featuring direct injection: a configuration with exhaust poppet valves and another one with piston controlled ports. A development of both projects has been performed through a coupled 1d-3d computational approach. A first set of KIVA calculations has been performed, in order to characterize the scavenging and the port flow patterns of both configurations, considering three different operating conditions, representative an aircraft engine. Then, several combustion simulations have been run, for defining two chambers able to match the project goals (high fuel efficiency, limited in-cylinder peak-pressure). For the two best configurations, the most interesting calculation results are presented in the paper. Copyright © 2011 SAE International.

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.

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.

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.

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 - Development of a 2-Stage Supercharging System for a HSDI Diesel Engine [Relazione in Atti di Convegno]
Mattarelli, Enrico; Rinaldini, Carlo Alberto; A., Mazza; M., Oliva
abstract

2-stage supercharging applied to HSDI Diesel engines is a promising solution for enhancing rated power, low end torque, transient response and hence the launch characteristics of a vehicle. However, a trade-off is required to match some conflicting issues, i.e. overall dimensions, cost, emissions control and performance. The outcome strongly depends on the specific constraints and goals of the project.

2009 - Optimization of a Supercharged Single Cylinder Engine for a Formula SAE Racing Car [Articolo su rivista]
Mattarelli, Enrico; Perini, Federico; Rinaldini, Carlo Alberto
abstract

The paper reviews the development and optimization of a SI high performance engine, to be used in Formula SAE/Student competitions. The base engine is a single cylinder Yamaha 660cc motorcycle unit, rated at about 48 HP at 6000rpm. Besides the reduction of engine capacity to 600cc and the mounting of the required restrictor, mechanical supercharging has been adopted in order to boost performance.The fluid-dynamic optimization of the engine system has been performed by means of 1D-CFD simulation, coupled to a single-objective genetic algorithm, developed by the authors. The optimization results have been compared to the ones obtained by a well known commercial optimization software, finding a good agreement.Experiments at the brake dynamometer have been carried out, in order to support engine modeling and to demonstrate the reliability of the optimization process

2009 - Optimization of a supercharged single cylinder engine for a formula SAE racing car [Articolo su rivista]
Mattarelli, E.; Perini, F.; Rinaldini, C. A.
abstract

The paper reviews the development and optimization of a SI high performance engine, to be used in Formula SAE/Student competitions. The base engine is a single cylinder Yamaha 660cc motorcycle unit, rated at about 48 HP at 6000rpm. Besides the reduction of engine capacity to 600cc and the mounting of the required restrictor, mechanical supercharging has been adopted in order to boost performance. The fluid-dynamic optimization of the engine system has been performed by means of 1D-CFD simulation, coupled to a single-objective genetic algorithm, developed by the authors. The optimization results have been compared to the ones obtained by a well known commercial optimization software, finding a good agreement. Experiments at the brake dynamometer have been carried out, in order to support engine modeling and to demonstrate the reliability of the optimization process. Copyright © 2009 SAE International.

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.

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.

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 - 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 - CFD COMBUSTION AND EMISSION FORMATION MODELING FOR A HSDI DIESEL ENGINE USING DETAILED CHEMISTRY [Relazione in Atti di Convegno]
V. I., Golovitchev; Montorsi, Luca; Rinaldini, Carlo Alberto; A., Rosetti
abstract

In order to comply with current emissions regulations, a detailed analysis of the combustion and emission formation processes in the Diesel engines accounting for the effect of the main operating parameters is required. The present study is based both on 0D and 3D numerical simulations by compiling 0D chemical kinetics calculations for Diesel oil surrogate combustion and emission (soot, NOx) formation mechanisms to construct a φ-T (equivalence ratio – temperature) parametric map. In this map, the regions of emissions formation are depicted defining a possible optimal path between the regions by placing on the same map the engine operation conditions represented by the computational cells, whose parameters (equivalence ratio and temperature) are calculated by means of 3D engine modelling.

2006 - Experimental and numerical investigation of split injections at low load in an hddi diesel engine equipped with a piezo injector [Relazione in Atti di Convegno]
Ehleskog, R.; Golovitchev, V.; Denbratt, I.; Andersson, S.; Rinaldini, C. A.
abstract

In order to investigate the effects of split injection on emission formation and engine performance,experiments was carried out using a heavy duty single cylinder Diesel engine. Split injections with varied dwell Time and start of injection were investigated and compared with single injection cases. In order to isolate the effect of the parameters selected to investigate,other variables were kept constant. In this investigation no EGR was used. The engine was equipped with a common rail injection system with a piezoelectric injector. To interpret the observed phenomena,engine CFD simulations using the KIVA-3V code were also made. The results show that a reduction in NOx emissions and brake specific fuel consumption was achieved for short dwell times whereas they were increased when the dwell time was prolonged. No EGR was used so the soot levels were already very low in the cases of sinGle injections. The results indicated,however,no increase in soot as a result of splitting the injection in two parts. Both HC and CO emissions were found to increase with split injections.

2006 - Performance and Emissions of a DME Diesel Engine - A Simulation Study [Relazione in Atti di Convegno]
H., Salsing; Rinaldini, Carlo Alberto; V. I., Golovitchev; I., Denbratt
abstract

In order to investigate DME combustion in a heavy duty diesel engine, a three dimensional CFD study was performed. Following parameters were investigated; injection timing, amount of fuel injected, umbrella angle and EGR amount with respect to combustion efficiency and emissions formation. It can be concluded that a large amount of EGR effectively suppresses NO formation and that the low heating value of DME can be balanced by a larger amount of injected fuel without any penalties in combustion efficiency and CO emissions.