Effects of spatial and temporal inlet total pressure fluctuations on rotating detonation characteristics in ethylene-air mixture

Inlet fluctuations in a rotating detonation engine play a critical role in shaping the propagation dynamics of rotating detonation waves (RDWs). Based on the OpenFOAM platform, numerical simulations are performed for ethylene-air mixture to investigate the effects of spatially and temporally fluctuating inlet total pressure on RDW propagation characteristics. The results show that spatial and temporal fluctuations significantly alter the RDW propagation modes, and the responses of the number of RDWs and propagation direction to the fluctuation parameters are complex and nonlinear. In the dynamic equilibrium stage, RDWs exhibit nonrepetitive spatial propagation, whereas the rotating detonation flow field shows pronounced temporal self-similarity. Under fixed spatial fluctuation parameters, the introduction of temporal fluctuations induces a distinct periodic response in RDW propagation, influencing the RDW velocity, pressure dynamics, heat release rate, and thrust. Due to the combined influence of spatial fluctuations, the temporal fluctuation amplitude is negatively correlated with the stability of RDW propagation, average heat release rate and thrust, whereas the temporal fluctuation frequency determines the temporal pattern and waveform of the AHRR and thrust responses. Under the operating conditions investigated in this study, when the spatial fluctuation amplitude and frequency are fixed at 0.2 MPa and 50, respectively, and the temporal fluctuation amplitude is kept the same, a temporal fluctuation frequency of 20 kHz yields the best RDW stability, combustor heat-release stability, and thrust stability. A high-frequency, low-amplitude perturbation combination (e.g., 20 kHz and 0.1 MPa) is conducive to maintaining a relatively steady combustion state and thrust output,demonstrating the potential for controlling thrust output stability through the strategic regulation of inlet parameters.