Restart Hysteresis and Surge Behavior of a Two-Dimensional Dual-Flow-Channel Inlet Subject to Back-Pressure Variation

Normal matching operation of a supersonic dual-flow-channel inlet in the mode transition is vital to a combined cycle engine (CCE). It is essential to study its working characteristics and explore its working boundary within the mode transition process. This article numerically studies the critical, surge, and unstart/restart characteristics of a two-dimensional dual-flow-channel mixed-compression inlet under a typical flow split ratio during mode transition. The numerical model was validated using inlet data from a free jet test. The aerodynamic performance, particularly the back-pressure characteristics, is analyzed. Furthermore, the inlet surge characteristics are explored. The inlet surge frequency caused by low-speed channel back pressure is 86 Hz, consistent with the acoustic oscillation frequency according to the wave propagation theory in a closed cylindrical cavity. Finally, the change rate of the outlet back pressure from a free jet test was applied to investigate the start and restart characteristics of the inlet. The results show that the critical back pressure of the low-speed channel and inlet is 34.4 times and 40.3 times that of the incoming flow, respectively, at a typical flow split ratio of 0.6. The restart back pressure of the inlet is 10.8 times the static pressure of the incoming flow. The observed pressure hysteresis phenomenon is also analyzed.