A study of combustion and emissions characteristics of a compression ignition engine processes using a numerical tool

Abstract

Experimental analysis of a diesel engine gives only the global picture of the in-cylinder processes, through averaged quantities. These averages are sometimes global averages or in some cases taken at each crank angle. To understand the in-cylinder processes better, the distribution of scalars becomes very important. In this paper, Converge, a CFD-tool was used to simulate the closed cycle in-cylinder process of a diesel engine to develop deeper insights into the effects of various injection parameters and compression ratio on engine performance and exhaust emissions. Results from Converge CFD-tool have been validated against the experimental data published in the literature. Effects of compression ratio, number of injector holes, spray angle, half cone angle and injection duration were studied using the validated model. Simulation results indicate that decreasing compression ratio resulted in a significant reduction in NO concentrations with a slight increment in specific fuel consumption (SFC). A narrow spray angle resulted in a considerable reduction of soot and SFC. Spray-to-spray interaction was increased with increasing number of nozzle holes. As a result, higher SFC, CO and soot were observed with increasing number of nozzle holes. Various in-cylinder contour plots showed that the injection with higher injection duration i.e. lower injection pressure produces relatively lower extent of fuel wall wetting and hence resulted in less intensity flames close to the piston head. Increasing the spray angle, number of holes and injection duration resulted in clear decline in exhaust NO concentration.