Effect of injection strategy on fuel-air mixing and combustion process in a direct injection diesel rotary engine (DI-DRE)

This paper aims at improving the combustion efficiency of direct injection diesel rotary engine (DI-DRE) by adjusting the injection strategy. An experimental validated 3D-dynamic simulation model coupled with chemical kinetics mechanism was established. A high-pressure direct injection mode was used to investigate the effect of diesel fuel injection timing (IT) and injection angle (IA) on fuel-air mixing and combustion process in a DI-DRE with spark ignition. Results showed that increasing IA changed the fuel distribution position from front to back of the combustion chamber, delayed IT and the fuel distribution area also became narrower and more concentrated. For combustion process, the fuel concentrated at partial central position towards the back of the combustion chamber was better for ignition. The distribution of more continuous mixture between the two spark plugs and concentration of more fuel near the trailing spark plug (TSP) was conducive to the improvement of combustion efficiency. The preferable combustion rate and emission performance were obtained when the IT was 80°CA (BTDC) and IA was 90°. Compared to the original scheme, maximum combustion pressure increased by16.82% while crank angle for maximum combustion pressure reduced by 8.19%. Soot and CO emissions reduced by 41.48% and 32.87% respectively. However, NO and CO2 emissions increased slightly.