Analysis of structure and regime of ethylene fuel injection flame in circular-section supersonic combustor

In this study, a hybrid Reynolds-Averaged Navier-Stokes/Large Eddy Simulation (RANS/LES) approach coupled with an improved Flamelet/Progress Variable model is used to numerically investigate the combustion flow field of an ethylene-fueled circular-section model scramjet at high Mach numbers. The computational results show highly consistent combustion structure and heat release characteristics with those from the experiments. On this basis, the analysis results indicate that the mixing process of the flow field is dominated by the large-scale flow structures, and the shock train at the center of the channel is the direct cause of promoting vorticity generation, fuel mixing, and downstream reaction zone wrinkling. In this case, the cavity does not directly participate in the heat release process, but rather plays a role in inducing shock waves and promoting mixing and combustion. Overall, combustion exhibits spatiotemporal multi-scale characteristics, and flames gradually develop towards a near equilibrium state as they propagate downstream. The scramjet mode and diffusion combustion dominate the entire reaction zone, and most of the fast-chemistry combustion is in the corrugated flamelets regime.