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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 paper reports a numerical activity on the investigation of the spray evolution within the combustion chamber of an automotive DISI engine under low-temperature cranking operations. In view of the high injected fuel amount and the strongly reduced fuel vaporization at cold cranking, wall wetting becomes a critical issue. Under such conditions, fuel deposits around the spark plug region can affect the ignition process, and even prevent engine start-up. In fact, due to the low injection pressure at engine start-up, the fuel shows almost negligible atomization and breakup, and the spray structure at the swirl-type injector nozzle is characterized by a single column of liquid fuel, strongly limiting the subsequent vaporization and enhancing the fuel-wall interaction. In order to properly investigate and understand the many involved phenomena, experimental visualization of the full injection process by means of an optically accessible engine would be a very useful tool.

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.

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

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

The paper is focused on the influence of the eddy viscosity turbulence models (EVM) in CFD three-dimensional simulations of steady turbulent engine intake flows in order to assess their reliability in predicting the discharge coefficient. Results have been analysed by means of the comparison with experimental measurements at the steady flow bench. High Reynolds linear and non linear and RNG k-ɛ models have been used for simulation, revealing the strong influence of both the constitutive relation and the ɛ-equation formulation on the obtained results, while limits in the applicability of more sophisticated near-wall approaches are briefly discussed in the paper. Due to the extreme complexity of typical ICE flows and geometries, the analysis of the behaviour of EVM turbulence models has been subsequently applied to a test-case available in literature, i.e. a high-Reynolds compressible flow over a inclined backward facing step (BFS).

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.

The paper is focused on the influence of the eddy viscosity turbulence models (EVM) in CFD three-dimensional simulations of steady turbulent engine intake flows in order to assess their reliability in predicting the discharge coefficient. Results have been analyzed by means of the comparison with experimental measurements at the steady flow bench. High Reynolds linear and non-linear and RNG k-ε models have been used for simulation, revealing the strong influence of both the constitutive relation and the ε-equation formulation on the obtained results, while limits in the applicability of more sophisticated near-wall approaches are briefly discussed in the paper. Due to the extreme complexity of typical ICE flows and geometries, the analysis of the behavior of EVM turbulence models has been subsequently applied to a test-case available in literature, i.e. a high-Reynolds compressible flow over a inclined backward facing step (BFS).

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.

An optimization study involving both fluid-dynamic and thermostructural aspects has been carried out for a 2200 cc turbocharged engine head for marine applications. In this cross-disciplinary problem, the structural and thermodynamic aspects have been decoupled. A preliminary set of CFD numerical analyses of the cooling jacket layout has been performed, in order to investigate critical aspects of the present configuration and improve the cooling performance, by means of local flow patterns and flow distribution analysis. At a second stage, temperature distributions within the metal cast parts have been derived from CFD in order to assess the fatigue strength of the component with structural finite elements. A proper choice of both CFD methodology and boundary conditions is carried out in order to determine a trade-off between computational effort and actual engine behavior representation.

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.

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