Effects of recess length on unsteady combustion ow elds and performance of a rocket injector

摘要

The present study investigates the effect of recess length on CH4/O2 combustion ow eld of a rocket injector using the compressible Navier-Stoke equations with a skeletal reaction mechanism in the manner of direct numerical simulation. The recess length parametrically changes with four different lengths, while the other geometrical parameters are xed. A main difference of combustion ow elds between the non-recessed and recessed injectors lies in the interaction mechanism of a large recirculation ow in the corner of combustion chamber with the incoming CH4 jet and ame anchoring region behind the post. With increasing the recess length, the combustion in the recessed region is more promoted, resulting in the earlier formation of higher-temperature combustion gas regions in the combustion chamber. However, the temperature increase in the combustion chamber is saturated with a relatively long recess length since no signi cant changes of combustion occur in the recessed region with further increasing recess length. This is because the incoming CH4 are mostly consumed in the recess region with a certain recess length. On the other hand, the in uence of the combustion gas on the CH4 upper and lower walls becomes larger with increasing the recess length due to the formation of larger amount of combustion gases.