Numerical Investigation of the Effect of Circumferentially Non-Uniform Injection on the Propagation Direction of MMH/NTO Rotating Detonation in a Hollow Combustor

The uncertain propagation direction of rotating detonation in hollow combustors limits the predictability of liquid hypergolic propulsion systems. In this study, the effect of circumferentially non-uniform injection on the propagation direction of monomethylhydrazine/nitrogen tetroxide (MMH/NTO) rotating detonation is numerically investigated. Different injection-intensity distributions are established by varying the local mass flow rate and injection velocity while maintaining the total propellant mass flow rate and overall oxidizer-to-fuel ratio. The results show that configurations with shorter injector groups exhibit inconsistent propagation directions, whereas the S4–M4–L4 configuration at a non-uniformity amplitude of 0.4 shows a clear directional preference consistent with the injection arrangement. At δ=0.6, opposite-direction propagation was observed in limited simulations, indicating a non-monotonic directional response under the investigated conditions. Reversing the injection arrangement after stable rotating detonation is established does not reverse the propagation direction. Transient pressure fields further reveal competition between oppositely propagating circumferential pressure waves during detonation establishment. These results indicate that circumferentially non-uniform injection mainly influences propagation-direction selection during the establishment stage.