Experimental and Numerical Study on the Local Unstart Mechanism of Hypersonic Inlet

Hypersonic inlet is a vital component of a scramjet, whose starting mode is the prerequisite of the normal operation. Relative researches and empirical formulae for hypersonic inlet, which have been conducted, are appropriate for low Mach number working condition. However, previous studies can not well reveal the performance degradation of inlet at high Mach number working condition. In this paper, local unstart flows of a hypersonic inlet are studied at freestream Mach number of 7.0 by experimental and numerical methods. Two operation modes of hypersonic inlet were observed at high Mach number, with the aid of bleed holes and downstream pressure variation simulator. Further, the detailed flow field of a quasi-two-dimensional hypersonic inlet was obtained by viscous numerical simulations. The present study shows that the local unstart of hypersonic inlet is the interaction between the separation region on the cowl and another separation bubble on the forebody, which may be of benefit to interpret the formation mechanism, prediction, and suppression of the inlet unstart mode.