The CFD analysis and simulation to investigate the effect of the piston crown inside the combustion chamber of a 4-stroke direct injection automotive engine under the motoring condition is presented. The analyses are dedicated to investigate the outcome of the piston shape differences to the fluid flow, heat transfer and turbulence characteristics for air-fuel mixture preparation in the terms of swirl and tumble ratio, turbulence kinetic energy, turbulence dissipation rate, turbulence viscosity and transient heat flux along the crank angle degrees occurred inside engine model. The first three parameters represents the fluid flow characteristics occurred inside cylinder which influences much to the combustion chamber where the air flows to the cylinder during the intake stroke and enhances greatly the mixing of air and fuel to give a better mixing for the combustion process. While, the turbulence kinetic energy and its dissipation rate characterise the k-ε turbulence model employed in this study with its viscosity to represent the small scale motion. On the other hand, the heat flux correspond to the wall heat transfer arises during engine cycle. The numerical calculations were performed in a single cylinder of 1.6 litre of a 4-stroke direct injection engine running at wide open throttle by using the CFD code to obtain the better piston crown used for such engine. The two different piston bowls for different engine speeds were compared to evaluate those mentioned parameters produced during intake and compression stroke. The results obtained from the numerical analysis can be employed to examine the homogeneity of air-fuel mixture structure for better combustion process and engine performance.
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