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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.

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 scavenging process, carried out by means of 3D-CFD simulations, supported by 1D engine cycle calculations. First, a characterization of the flow through the ports and within the cylinder is performed under conventional operating conditions. Then, a complete 3D cycle simulation, including combustion, is carried out at four actual operating conditions, at full load. The CFD results provide fundamental information to address the development of the scavenging system, as well as to calibrate a comprehensive 1D engine model.

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

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.

An automotive 3.2 liter, V8, turbocharged S.I engine by Maserati is analyzed by using integrated experimental and computational methods. An experimental activity has been carried out during the dynamometer test. Torque, fuel consumption and air-fuel equivalence ratio have been measured for several engine speeds at wide open throttle. Furthermore, cycle averaged gas pressure and temperature have been acquired in the most important engine locations. A 1-D fluid dynamic model has been set up, for the engine simulation using the WAVE code, by Ricardo Software. The modeling guidelines are discussed in details. The accuracy of the model has been assessed through a comparison between the experimental and computational results. Finally, a few simulation outputs, particularly useful for addressing the optimization process, are shown.

In this paper, a comparison has been carried out between two Formula 1 engine architectures: a traditional V12 and a 12 cylinder with three banks and one crankshaft, which will be referred to from here on as W12. This comparison is made in terms of geometrical features, as well as in terms of safety coefficients, torsional stiffness, state of balance and friction losses. The W12's crankshaft is 158 mm shorter and stiffer than the V12's. Furthermore, this crankshaft is simpler and lighter. The W12 engine front section is wider. The crankshaft of the W12 has a minimum safety factor that is 30% lower than the V12's under the same operating conditions (18000 rpm, bmep=13 bar). While the V12 is perfectly self-balanced, the secondary forces are out of balance in the W12's crankshaft. This unbalance is, however, no more critical than the one occurring in a V10 or V8. Friction losses in the W12 should be slightly lower in comparison to the V12.

One dimensional CFD codes are standard tools for engine development, in particular for the optimization of intake and exhaust systems. However, the accurate prediction of both engine brake performance and acoustic outputs is not that trivial. A quite critical issue is the modeling of complex engine components, such as air cleaners, plenums, exhaust junctions, silencers, etc. A trade-off is required in order to balance the accuracy of the acoustic analysis and the computational cost, particularly when DOE techniques have to be applied. In this paper a methodology for an integrated acoustic and performance analysis of a high performance SI engine is described. An engine simulation model has been built by using a commercial software, and it has been validated against experiments, finding a good agreement. It is remarked that the measurements of both acoustic and engine performance parameters are taken by using standard facilities and equipment, no anechoic test bench is required.

The paper describes a CFD multidimensional and multicycle engine analysis applied to a novel 2-Stroke HSDI Diesel engine, under development since a few years at the University of Modena and Reggio Emilia. In particular, six operating conditions are considered, two of them at full load and four at partial. The simulation tool is STAR-CD, a commercial software extensively applied by the authors to HSDI Diesel engines. Furthermore, an experimental calibration of the combustion model has been performed and reported in this paper, carrying out CFD simulations on a reference Four Stroke HSDI Diesel engine. As expected, in the multi-cycle analysis a wide dependence of pollutants on trapped charge composition has been found. Much less relevant is the cycle-by-cycle variation in terms of performance parameters, such as trapped mass, IMEP, combustion efficiency, etc.

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. In the paper, reference is made to 2.8L, 4 cylinder in-line unit produced by VM Motori (Cento, Italy), equipped by a standard variable geometry turbocharger. A 1D thermo-fluid-dynamic model of the Euro V version of the engine was built and calibrated against experiments at the dynamometer bench, at both full and partial load.

Standard design practice usually adopts steady flow tests for addressing optimisation of the intake valve-port assembly. Recently, with more user-friendly CFD tools and with increased computing power, intake stroke simulations, handling both piston and valves motion, have become practical. The purpose of this paper is to compare the design guidelines provided by the standard steady flow tests (both experimental and numerical) and the information coming from a CFD-3D intake stroke analysis. Reference is made to a four valve HSDI Diesel engine. Three swirl control strategies are investigated. It is supposed that one intake valve is kept closed, while the other one operates normally (first strategy). The second strategy consists in a 50% reduction of the lift of both valves. Finally, the third possibility is the blockage of one intake port by means of a simple butterfly valve.

The paper reviews the transformation of a 2.8 litre, 4 cylinder, turbocharged Diesel engine, produced by VM Motori (Cento, Italy), into a Compressed Natural Gas (CNG) naturally aspirated power unit. The main goal of the project is to keep an about constant top power value, minimizing engineering costs. The development of the new engine has been supported by experiments and 1D cycle simulations. A first prototype has been built and extensively tested at the dynamometer bench. These data helped the validation of the simulation model, which has been used as an optimisation tool, addressing the next steps of the development process.

The purpose of this paper is to compare different methodologies of CFD analysis, applied to the intake plenum of a turbocharged HSDI Diesel engine. The study is performed by using both an engine cycle simulation code and a 3D-CFD code. Experiments at the engine dynamometer and at a steady flow bench support the theoretical study. The most promising simulation technique presented in the paper is the integrated 1D and 3D-CFD simulation. This numerical approach showed itself to be particularly suitable for analysing complex engine components where the flow patterns are fully transient.

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

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

High power output, four stroke, motorcycle engines are characterised by a complex combustion evolution strongly influenced by the properties of the averaged and turbulent flow field. In the present paper, state-of-the-art detailed computational methods are used to investigate the combustion evolution in a four cylinder, four valve per cylinder engine with a four-in-one exhaust where volumetric efficiencies and mixture compositions have been previously computed. Three dimensional unsteady computations of intake, compression, combustion and expansion strokes are performed. The method proves to be effective in qualitatively predicting heat release rate variations with engine speed and volumetric efficiency, while the simple modelling of the turbulent combustion does not allow to precisely define the magnitude of these variations.

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

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

Thermal Engine Encapsulation (TEE) is a technique for reducing heat loss from an engine after it has been switched off, in order to get a warmer re-start. This practice yields benefits in terms of fuel economy, emissions and wear, especially for vehicles used for short journeys in cold weather and with engines warming up slowly. In this study, the encapsulation of a small automotive diesel engine is investigated by means of theoretical and experimental analyses. In particular, the influence of oil temperature on brake specific fuel consumption and emissions is calculated. Furthermore, the thermal behavior of the engine has been simulated by a lumped-capacitance model, in order to assess the correlation between encapsulation thickness and cool-down time.

This paper presents a numerical study of the combustion chamber design influence on the performance of racing engines. The analysis has been applied to the Ferrari 10 cylinder 3.0 liter S.I. engine adopted in Formula One racing. The numerical investigation aimed to asses the influence of stroke-to-bore ratio changes on engine performance within real life design constraints. The effects of the stroke-to-bore ratio on both the volumetric efficiency and the thermal conversion efficiency have been investigated. Flame front area maps, wall areas wetted by burned gases, mean flow field patterns and main turbulent parameters have been compared for two different S/B ratios. Since higher intake and exhaust valve areas per unit displaced volume result in a higher volume of piston bowls, a lower S/B ratio leads to a lower compression ratio, which strongly limits the indicated mean effective pressure.

This paper compares different engine solutions for the FIM MotoGP World Championship. Starting from the general guidelines given in a previous paper [2], in this study the specific features of each engine architecture (3 and 4 in line, V4, V5 and V6) are considered. 1-D engine simulations, based on a previously validated model, are extensively used to optimize each solution, as well as to provide a comparison among the engines in terms of dynamometer performances. Some issues concerning engine balance, engine overall dimensions, intake and exhaust system lay-out are discussed. Finally, the influence of the engine on the bike acceleration is calculated by means of a simple simulation at the Mugello track. The comparison has shown slight differences among the proposed configurations. Globally, the V engines, with four and five cylinders, have resulted to be the best solutions.