Investigation of spray angle and combustion chamber geometry to improve combustion performance at full load on a heavy-duty diesel engine using genetic algorithm

Abstract

An optimization of spray angle and combustion chamber geometry was conducted to improve the in-cylinder fuel/air mixing process and optimize the combustion process of a heavy-duty diesel engine at full load. The chamber is based on the stepped-lip piston bowl, and the lip radius, lip depth, bowl radius and bowl distance are optimized. A sensitivity analysis of fuel/air mixing and combustion process to stepped-lip chamber geometry parameters was carried out. The simulated results show that the lip radius affects the fuel splitting at the lip, and has the greatest influence on the stepped-lip combustion chamber. The bowl radius is the second most important optimization parameter, followed by the bowl distance and finally the lip depth. To obtain the optimal combination of the combustion chamber geometry in a wide searching space, a total of 100,000 different combustion chambers were solved with multi-island genetic algorithm. Compared to the baseline, the optimized chamber has higher enhanced air utilization, more homogeneous fuel/air mixture, rapider combustion process, higher indicted power delivery and lower emissions. The results of this study are important to guide the stepped-lip combustion chamber design of heavy-duty diesel engines for better fuel/air mixture and combustion performance.