Numerical Investigation of Effect of Bowl Profiles on Performance and Emission Characteristics of a Diesel Engine

The mixture generation in Diesel engines is mainly driven by the combustion chamber geometry and the fuel spray characteristics. Thus, combustion chamber geometry is considered as an important parameter for Diesel engine in-cylinder emission control strategy. In this work, effect of nozzle tilt angle and various combustion chamber geometries such as mexican-hat combustion chamber (MHCC), double-lip combustion chamber (DLCC), bow combustion chamber (BCC) and toroidal combustion chamber (TCC) on in-cylinder processes and emissions has been studied numerically using a CFD-tool called Converge. Converge code has been validated against the experimental results of a Diesel engine. Results showed that a significant reduction in soot, HC and CO has been achieved with the optimum (156°) nozzle tilt angle; but NO_x was increased. A significant reduction in soot (∼16%), HC (∼58%) and CO (∼96%) with an acceptable increase in NO_x (∼12%) has been achieved with MHCC as compared to these values from the base hemispherical combustion chamber (HCC). Effect of central cone angle of bowl on emissions has also been studied with MHCC and bowl with 64° half central cone angle has been found to be the optimum. DLCC and BCC also offered a good reduction in HC and CO without altering NO_x and PM. In TCC, considerable amount of fuel got accumulated near the curvature of the bowl and thus led to higher soot.