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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.

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.

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 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.

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 appears a promising solution for enhancing rated power, low end torque, transient response and hence the launch characteristics of a vehicle. However, many open points still remain, in particular about the impact on emissions control and fuel economy at partial load conditions, generally requiring both high airflow and high EGR rates. The paper analyzes and compares two types of 2-stage supercharging systems: a) two turbochargers of different size; b) one turbocharger coupled to a positive displacement compressor. The goal of the paper is to assess pro and cons of the most feasible configurations for a typical automobile Diesel engine, complying with Euro V regulations and beyond. The base engine is the 2.8L, 4 cylinder in-line unit produced by VM Motori (Cento, Italy), equipped by a standard variable geometry turbocharger.

The paper presents the development and validation of phenomenological predictive schemes for quasi-dimensional modeling of pollutant emissions in direct injected Diesel engines. Models for nitric oxide (NO), carbon monoxide (CO), as well as soot and unburned hydrocarbons (HC) have been developed. All of them have been implemented into a DI Diesel engine simulation environment, previously developed by the authors, which features quasi-dimensional modeling of spray injection and evolution, air-fuel mixture formation, as well as auto-ignition and combustion. An extended Zel'dovich mechanism, which takes into account the three main, thermal-NO formation chemical reactions has been developed for predicting NO emissions.

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.

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.

The paper reviews the theoretical and experimental development of the engine powering the 2011 Formula SAE single seater of the University of Modena and Reggio Emilia (UNIMORE). The general design criteria followed by the UNIMORE team are discussed and compared to those chosen by other competitors. In particular, the reasons supporting the selection 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 much bigger effort for getting an acceptable level of brake power. Therefore, the development was massively supported by CFD simulation (both 1D and 3D) and by experiments. It was found that the most important design areas for the single cylinder are: the intake system, including the restrictor (20 mm), the intake runner and the plenum, and the muffler.

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.

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.

In this paper an integrated experimental and numerical approach is applied to optimize a new 2.5l, four valve, turbocharged DI Diesel engine, developed by VM Motori. The study is focused on the EGR system. For this engine, the traditional dynamometer bench tests provided 3-D maps for brake specific fuel consumption and emissions as a function of engine speed and brake mean effective pressure. Particularly, a set of operating conditions has been considered which, according to the present European legislation, are fundamental for emissions. For these conditions, the influence of the amount of EGR has been experimentally evaluated. A computational model for the engine cycle simulation at full load has been built by using the WAVE code. The model has been set up against experiments, since an excellent agreement has been reached for all the relevant thermo-fluid-dynamic parameters. The simulation model has been used to gain a better insight on the EGR system operations.

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.

In this paper the 1-D modeling of flow through the assembly of valve and port in internal combustion engines is discussed. Three dimensional effects and flow losses close to the valve are accounted for through the experimental effective area, determined at a steady flow bench. The steady flow bench is standard equipment, widely used for engine design and development. The classic method is adequate to the purpose as long as the objective of measuring the effective area is a comparative process for the experimental improvement of the flow through the valves. On the contrary, if the effective area is used for engine cycle simulation, the experimental results must be considered with care. It is demonstrated in this study that, for the outflow from a cylinder to a valve, standard experimental practice can sometimes produce a significant error on the flow rate predicted by simulation.

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 [1], 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).