Suppression of flow response hysteresis in the throttling/unthrottling process for supersonic inlet

Abstract

The flow response hysteresis in a mixed-compression supersonic inlet's throttling/unthrottling process is unconducive to its practical engineering applications. To suppress such hysteresis, herein, a flow control method based on a distributed bleed system in the inlet's internal contraction part was proposed and applied to a rectangular supersonic inlet with a designed Mach number of 4.0 and an internal contraction ratio of 1.5. All tests were conducted in a supersonic wind tunnel at a freestream Mach number of 2.9, and the relevant test data were obtained using the high-speed schlieren and dynamic pressure measurement systems. The results indicate that the distributed bleed system improved the uncontrolled inlet's unstart throttling ratio from 43.8% to 47.3% and the restart throttling ratio from 29.4% to 47.1%, and it essentially eliminated the flow response hysteresis during the throttling/unthrottling process. Moreover, the hysteresis mechanism of the uncontrolled inlet, dominated by the separation-induced flow structures in the internal contraction part, was investigated to help elucidate the targeted control mechanism of the bleed system that suppresses the hysteresis. Finally, the specific flow phenomena in the oscillation of the controlled inlet were examined to study the bleed system's impact on the unsteady flowfield, including the coupled flow of the mainstream with the bleed system and complex wave motion structures.