Experimental investigation on unstart-restart hysteresis of a supersonic inlet during throat regulation

Abstract

The hysteresis during the throat regulation process of a supersonic variable inlet is unconducive to restart. Hence, detailed experimental studies of such a hysteresis and its control are necessary. A throat variable supersonic inlet was designed at a shock-on-lip Mach number of 4.0 and an Internal Contraction Ratio (ICR) ranging over 1.21–2.94. Meanwhile, a distributed bleed system was proposed to suppress the hysteresis. The wind tunnel tests were conducted at Mach number 2.9. The throat regulation processes were recorded using a high-speed schlieren and dynamic pressure acquisition system. The results indicate that the unstart and restart ICRs during the uncontrolled inlet’s throat regulation process were 1.95 and 1.48, respectively, demonstrating an unstart-restart hysteresis. Four typical flowfields were summarized during the uncontrolled inlet’s restart process. The proposed bleed control increased the unstart and restart ICRs to 2.06 and 1.75, respectively, and the inlet realized the designed state as the ICR was further decreased to 1.67. The controlled inlet’s hysteresis loop was decreased compared to the uncontrolled inlet. Finally, the mechanism of the hysteresis, dominated by the entrance separation-induced wave system, was clarified. The mechanisms of the bleed control to broaden the unstart and restart boundaries and suppress the hysteresis were elucidated.