Influence of Engine Speed on Mixing and Emission Characteristics of Multiple-Injection Common Rail Direct Injection Diesel Engine

Abstract

Increase in engine speed increases the in-cylinder turbulence and hence the rate of mixing. However, it is difficult to directly measure the mixing rate and relating its effect on emissions. Hence, in this paper, the comparison of mixing rate at different engine speeds are demonstrated with a multi-zone phenomenological model which has been developed and validated on a wide range of engine operating conditions. The mixing rate is evaluated using a standard quasi-dimensional k-ε formulation. The quantitative predictions of mixing rates at different engine speed substantiate the cause of soot emission reduction at higher engine speed.