Spatiotemporal flow evolution in a rocket-based combined-cycle inlet during ejector-to-ramjet mode transition

Abstract

The spatiotemporal distribution characteristics and flow stability of a rocket-based combined-cycle (RBCC) inlet during the ejector-to-ramjet mode transition are investigated numerically. The operational pressure of the embedded rocket is adjusted to three different levels, and the time-sequences of the rocket and back pressure regulation are varied. The pressure in feature sections is monitored to reveal the coupling relationship and stability of the internal flowfield. The inlet is more adaptable to severe disturbances under the “throttle-maintaining” regulation and is susceptible under the “direct-shutdown” regulation. The severe fluctuation period is relatively short within “medium throttle-maintaining,” while is lengthy within the “high throttle-maintaining.” The severe fluctuation under the direct-shutdown develops with the propagation of the regulation and decays with its establishment. The ultimate flowfields driven by different time-sequences reach unanimity with the same adjustable parameters of embedded rocket and back pressure; however, the dynamic evolutions show distinct characteristics. During the mode transition, pressure “valleys” are formed in any selected sections with the rocket regulations, and “peaks” are developed in many sections due to the propagation of back pressure or the instability of the rocket jet. For the medium throttle-maintaining regulation, the effect of time-sequence on the flowfield is relatively weak. For the high throttle-maintaining regulation, the pressure disturbance rises abruptly under the rocket priority regulation, with a most severe amplitude of 100.7%. For the direct-shutdown regulation, the maximum pressure disturbance of 125% is observed within the rocket priority regulation, and the minimum disturbance occurs within the back pressure priority regulation.