Numerical and experimental investigation on the influence of inlet contraction ratio for a rocket-based combined cycle engine

The influences of inlet contraction ratio on both the inlet and combustor of the rocket-based combined cycle engine are investigated in this paper by experimental and numerical approaches. A translating spike was employed to simulate the inlet counter pressure in the wind tunnel experiment. Steady-state pressure distributions were recorded and schlieren photos were obtained simultaneously. The combined numerical-experimental results show that the increased inlet contraction ratio always results in the increasing of the compression ratio and capability of anti-counter pressure, while its impact on the mass flow coefficient is negligible. Besides, the reactive numerical results show that the coefficients of inlet drag and combustor thrust increase with the increasing of the inlet contraction ratio, while the nozzle thrust coefficient demonstrates an opposite trend. These suggest that the selection of an appropriate inlet contraction ratio can effectively improve the total thrust coefficient of the engine, while the appropriate inlet contraction ratio is to be set to the minimum that satisfies the robust combustion requirement.