To address the issue of low energy utilization efficiency in the unsteady exhaust process of pulse detonation ramjet engines, which arises from throat choking and wave reflection, a passive adaptive nozzle is proposed. Numerical simulations were employed to investigate the control mechanism of this configuration on the flow field, as well as the effects of spring load on engine performance. The results indicate that the nozzle achieves adaptive geometric adjustment through the dynamic balance between aerodynamic loading and spring restoring force, effectively suppressing shock accumulation and Mach reflection in the throat region and, thereby, alleviating aerodynamic blockage during the initial exhaust phase. When the maximum spring load is 240 N, optimal phase synchronization between the mechanical response frequency and the pressure decay rate is achieved, significantly reducing losses associated with over-expansion and under-expansion. The cycle-averaged thrust is increased by 38%.
Yang et al. (Fri,) studied this question.