On the optimization of the double-layer combustion chamber with and without EGR of a diesel engine

Abstract

This paper focuses on the multi-objective optimization of the fuel injection parameters, combustion chamber geometry parameters and engine operating parameters of a double-layer combustion chamber. Three optimization objectives have been optimized by combining the NSGA-II genetic algorithm and the KIVA-3V program, including the indicated specific fuel consumption (ISFC) rate, NOx and soot emissions. Meanwhile, 10 engine parameters, including two injection parameters, six combustion bowl geometry parameters, compression ratio, and Exhaust Gas Recirculation (EGR) rate, are optimized simultaneously. The results show that the NOx and soot emissions exhibit an apparent trade-off relationship as well as the NOx emission versus ISFC. In addition, response surface analysis is conducted to investigate the influence of the selected parameters on the optimization objectives. It indicates that the retarded injection timing and EGR are conducive to the reduction of the NOx emission. Moreover, the double-layer combustion chamber with an impingement platform can enhance the fuel-air mixing process, and the air utilization rate of the combustion chamber is henceforth improved. Based on our optimization, the high temperature area is widely distributed throughout the double-layer combustion chamber, and most of the soot can be oxidized sufficiently in the main combustion period.