Hypersonic Inlet Studies for a Small-Scale Rocket-Based Combined-Cycle Engine

Experimental tests on a small-scale rocket-based combined-cycle model engine at Mach 8 were conducted to investigate the influence of inlet airflow changes on the engine performance. Flat plates of different lengths with a sharp leading edge and parallel to the freestream airflow, simulating the presence of vehicle body, were mounted before the inlet bottom surface. The test results indicated that fuel ignition, combustion chamber pressure, and engine net thrust were strongly affected by moderate changes of the flat plate length. The formation of an oblique shock wave due to hypersonic viscous interaction effects was observed above the flat plates. External compression of the captured airflow and lateral mass spillage were quantified on the basis of wall pressure measurements near the engine inlet for all tested plates. A convenient flat plate length range was identified that minimized spillage and optimized the engine performance.