In this study, three-dimensional numerical studies have been performed to investigate the performance of a rotating detonation combustor with a diverging nozzle downstream. The effects of a diverging nozzle on the formation and propagation process of a detonation wave and typical flow field parameters in a rotating detonation combustor are mainly discussed. The results indicate that the diverging nozzle downstream is an important factor affecting the performance and design of a rotating detonation combustor. The diverging nozzle does not affect the formation and propagation process of the rotating detonation wave, while the time of two key wave collisions are delayed during the formation process of the detonation wave. With increases of the diverging angle, the rotating detonation combustor with the diverging nozzle can still maintain a certain pressure gain performance. Both the diverging nozzle and diverging angle have great influence on the flow field parameters of the rotating detonation combustor, including reducing the high pressure and temperature load, making the distribution of the outlet parameters uniform, and changing the local supersonic flow at the outlet. Among them, the outlet static pressure is reduced by up to 88.32%, and the outlet static temperature is reduced by up to 32.12%. This evidently improves the working environment of the combustor while reducing the thermodynamic and aerodynamic loads at the outlet. In particular, the diverging nozzle does not affect the supersonic characteristics of the outlet airflow, and on this basis, the Mach number becomes coincident and enhanced.
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