Optimization of Tangential Mass Injection for Minimizing Flow Separation in aScramjet Inlet

摘要

With the reemergence of interest in air-breathing hypersonic propulsion, scramjetinlet efficiency has become an area of concern. The impingement of the engine cowl shock near the shoulder (expansion corner between forebody and combustor) may cause boundary layer separation which reduces inlet efficiency. Tangential mass injection (TMI) upstream of the shoulder has recently been tested to control this separation but without much parametric evaluation. To resolve this deficiency, a 2-D scramjet inlet model with variable length cowl, and TMI was built and tested in the WL Mach 6 High Reynolds Number Facility. Parameters varied were boundary layer thickness, TMI flow rate, cowl position, cowl and shoulder angle, and slot to shoulder distance. The optimum slot location was determined by finding the minimum injection flow rate required to eliminate separation for each configuration and analyzing the trends. The test results, along with a simplified mixing theory based on maximizing the jet/freestream wake mass flux, indicated that the optimum slot location was 5-6 slot heights upstream of the shoulder. However, this result was somewhat obscured by the observation that, when the cowl shock impinged closer to (but downstream of) the slot or aft of the shoulder, less mass injection was required to eliminate separation. A typical TMI rate for controlling the shock-induced separation in these regions was 3-6% of the inlet captured mass flow.