Analysis of Homogeneity Factor for Diesel PCCI Combustion Control

Owing to the potentials for low NOx and soot emissions, diesel PCCI combustion has been widely studied over last 10 years. However, its control is still the main barrier to constrain it to be applied on production engines. As there are a number of variables which affect the mixing and combustion process, it is difficult to develop control strategies with adequate functions but simple control order for implementing them. In the current research, a reformed Homogeneity Factor (HF) of in-cylinder charge has been explored as a control medium for simplifying the control model structure. Based on multi-pulse injection, the effects of operating parameters on the Homogeneity Factor and the relationship between Homogeneity Factor and mixing, combustion processes, emissions were investigated in a four-valve, direct-injection diesel engine by CFD simulation using KIVA-3V code coupled with detailed chemistry. The results show effects of most operating conditions on Homogeneity Factor can be analyzed with monomial variations though the injection timing produces some complication. Then an perfect correlation can be built between Homogeneity Factor and 50% burnt location, while acceptable regressions can be provided by the Homogeneity Factor for NOx, soot and CO2 emissions (or fuel consumption).