Throttling Characteristics of a Supersonic Variable Inlet at Different Internal Contraction Ratios

Abstract

Supersonic inlets with a wide operating Mach number range can regulate the internal contraction ratio (defined as the area ratio of the duct entrance and throat, denoted as ICR) to improve the critical total pressure recovery performance and flight condition adaptability. To elucidate the association between the downstream throttling characteristics and the ICR, a rectangular supersonic inlet with a variable ICR (ranging from 1.21 to 2.04) was designed. Using a high-speed schlieren and dynamic pressure acquisition system, a series of experimental studies was carried out in a supersonic wind tunnel at a freestream Mach number of 2.9. The results indicate that the downstream-throttling unstart modes of the inlet at different ICRs can be divided into two classes, namely, a “steadily changing” mode and an “abruptly changing” mode. As the ICR increases, the inlet substantially improves its compression and throttling performances by sacrificing a small amount of mass flow. Moreover, the inlet’s throttling characteristics at different ICRs are dominated by the flow loss of the terminal shock train. Then, the influence mechanism of the ICR on the inlet’s downstream throttling characteristics is revealed, and a throttling characteristic prediction model for rectangular supersonic variable inlets is established.