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Air motion inside the engine cylinder plays a predominant role on combustion and emission processes. An attempt has been made in this investigation to simulate the in-cylinder air motion in a DI diesel engine with four different piston configurations such as dome piston, bowl on dome and pentroof piston and pentroof offset bowl piston. For computational analysis, the commercial general purpose code STAR-CD Es-ice has been used, which works on the method of finite volume. To validate the simulation, qualitative and quantitative comparisons have been done with the PIV results available in the literature. From this study, the best possible piston configuration has been arrived at.

Of late Direct Injection Spark Ignition (DISI) engines are replacing the carburetted SI engines due to certain inherent advantages like uniform distribution of fuel-air mixture in all cylinders in multi cylinder engines. However the homogeneity of the mixture depends on the time of injection as well as the type of fuel injector. It is expected that late in the compression stroke the fuel-air mixture near the spark plug should be a combustible mixture. In order to achieve this, proper air motion during induction and compression is a must. Further the interaction of fuel and air from the start of injection is equally important. This paper addresses these issues. For this a CFD study has been carried out. The injection timings selected are 90, 180 and 2700 aTDC, the idea being to understand the effects of early or late injection on fuel air mixing. The appropriate governing equations are solved using finite volume method. RNG k-ε turbulence model is used for physical modelling.

This paper deals mainly with the computer simulation and experimental investigations on a single cylinder, four-stroke, spark ignited, extended expansion engine. The simulation procedure involves thermodynamic and global modeling techniques. Sub-models have been used for predicting heat transfer, friction and gas exchange processes. A two-zone model is adopted for combustion process. Combustion model predicts mass burning rate, ignition delay and combustion duration. It uses sub-models for calculating flame-front area, flamespeed and chemical equilibrium composition of ten product species. Experimentally measured valve-lift data along with suitable coefficient of discharge is used in the analysis of gas exchange process. Unburned hydrocarbons, carbon monoxide and nitric oxide emissions have also been predicted. Experiments have been conducted on a single cylinder, air-cooled, four-stroke, spark-ignition engine.

This paper deals with a numerical investigation on swirl generation by a helical intake port and its effects on in-cylinder flow characteristics with axisymmetric piston bowls in a small four-valve direct injection diesel engine. The novelty of this study is in determining the appropriate design and orientation of the helical port to generate high swirl. A commercial CFD software STAR-CD is used to perform the detailed three dimensional simulations. Preliminary studies were carried out at steady state conditions with the helical port which demonstrated a good swirl potential and the CFD predictions were found to have reasonably good agreement with the experimental data taken from literature. For transient cold flow simulations, the STAR-CD code was validated with Laser Doppler Velocimetry (LDV) experimental velocity components’ measurements available in literature.

Of late direct injection engines are replacing carburetted and port injected engines due to their high thermal efficiency and fuel economy. One of the reasons for the increased fuel economy is the ultra lean mixture with which the engine operates under low loads. Under the low load conditions, the air fuel ratio of the mixture near the spark plug is close to stoichiometric values while the overall mixture is lean, which is called stratified mixture. In order to achieve this, proper air motion during the late stages of compression is a must. Quality of the mixture depends on the time of injection as well as the type of fuel injector and mixture preparation strategy used. Engines employing air guided mixture preparation are considered as the second generation engines. For understanding the efficient mixture preparation method, three types of flow structures like base (low tumble), high tumble and inclined swirl are created inside the engine cylinder using shrouds on the intake valves.

The fuel injection timing is one of the most important operating parameters that affect the atomization, mixture formation and combustion which determines the performance and emissions of a gasoline engine. Optimizing the injection timing will improve the performance of the engine to a large extend. Towards this end artificial neural-network (ANN) technique using Levenberg-Marquardt (LM) training algorithm is used to train and optimize the fuel injection timing of a single cylinder, four-stroke gasoline engine. Experimental studies have been carried out to obtain training as well as test data. For various engine speeds between 700 and 5000 rpm and for different manifold absolute pressures, fuel injection timing was measured by conducting experiments. The experimental data set generated is used to train the neural network to arrive at the optimized performance of the engine.

This paper deals mainly with the computer simulation and experimental investigations on a single cylinder, four stroke, spark ignited, extended expansion engine. The simulation procedure involves thermodynamic and global modeling techniques. Submodels for predicting gas exchange processes, heat transfer and friction are used. Two-zone model is adopted for combustion process. The combustion model predicts mass burning rate, ignition delay and combustion duration. It uses sub-models for calculating flame-front area, flame-speed and chemical equilibrium composition of ten product species. Experimentally measured valve-lift data along with suitable coefficient of discharge is used in the analysis of gas exchange process. Unburned hydrocarbons, carbon monoxide and nitric oxide emissions have also been predicted. Experiments have been conducted on a single cylinder, air cooled, four stroke, spark ignition engine. A production engine was modified to run as extended expansion engine.