Effects and mechanisms of strut injection strategy on mixing and combustion in oblique detonation engines

The oblique detonation engine has attracted increasing attention due to its excellent development potential in the high Mach number range. However, the mixing performance directly affects the initiation of oblique detonation waves. Through experiments and simulations, this work investigates the effect of strategy-induced mixing characteristics on the combustion of oblique detonation waves. In this study, the wind tunnel test of oblique detonation engine using C₂H₄ as the fuel is carried out. The experiments verify that the oblique detonation can be successfully initiated by the strut injection strategy, and the clearly structured oblique detonation is observed within the test duration. On the basis, numerical studies are conducted on two injection factors: strut position and injection equivalence ratio. The results show that the further the strut is from the ramp, the higher the mixing efficiency, peaking at 62.98%. It is also observed that the greater distance from the ramp results in the higher total pressure loss prior to reaching the ramp. What is more, the mixing process is periodically enhanced and inhibited by the wave system of strut-reflected shock waves and wall reflections. Therefore, controlling the reflection wave system in front of the ramp is of great significance for the improvement of mixing efficiency. The fuel injection strategy with the higher equivalence ratio delivers greater fuel penetration depth but reduces the mixing efficiency. The mixing efficiency is 71.3% at the equivalence ratio of 0.2 and drops to 28.5% at the equivalence ratio of 1.6. The higher equivalence ratio also causes greater total pressure loss. The mixing efficiency directly impacts the detonation combustion state.