Effects of the injection nozzle on the propagating characteristics of ethylene/air rotating detonation waves

Numerical simulations of an ethylene/air rotating detonation engine with a plenum structure were conducted to investigate the effects of different injection nozzles. The flow field characteristics, propagation features, and propulsion performance of the detonation wave were thoroughly discussed. Three types of nozzles were utilized, all of which achieved a stable single-wave mode. The detonation wave induces an upstream wave in the plenum, which after reflection, generates reflected waves. The combustion products exhibit backflow, but this phenomenon is largely confined within the nozzle. Significant total pressure losses occur after the propellant passes through the nozzle. It was found that the injection velocity has a substantial impact on the performance of the combustion chamber. The injection velocity through the convergent nozzle is the lowest among the three nozzles, with the longest fuel residence time, resulting in the best combustion effect and the highest total pressure gain. The results were compared with an ideal combustion chamber without a plenum, revealing that even after accounting for the losses through the injection structure, the total pressure gain is still less than that of the ideal combustion chamber model. The injection velocity through the convex nozzle is the highest, leading to the poorest propulsion performance. However, due to the convex structure in the middle of the nozzle, which effectively blocks the propagation of pressure waves, the operation is the most stable.