Effect of Piston Bowl geometry on Flow, Combustion and Emission in DI Diesel Engine - A CFD approach

The Vehicular emission norms on IC Engines are becoming more and more stringent with a view to control pollution. Engine manufacturers are taking extreme care in the engine design to meet the emission norms. The piston bowl design is one of the most important factors that affect the air-fuel mixing and the subsequent combustion and pollutant formation processes in a direct injection diesel engine. In this regard CFD has been identified as a very helpful tool through which the in-cylinder processes can be simulated and studied before proceeding to prototype and experimental studies. In the present study, a 6 HP single cylinder, constant speed DI diesel engine has been selected for analysis.The present work deals with three dimensional modeling of diesel engines with three different bowl geometry to study the in-cylinder flow characteristics The flow characteristics of these engine bowl configurations are simulated under transient condition using STAR CD, a commercial computational fluid dynamics (CFD) package.. The computational results such as swirl ratio, Pressure, Temperature, NOX and Soot emissions at different crank angles have been compared. It has been observed that combustion chamber shape has a negligible effect on in-cylinder flow dynamics during initial part of the compression. But near TDC of compression stroke is an important period with respect to combustion and pollutants formation, as was observed to be quite significant.