Flow and combustion characteristic analysis of circular-section scramjet under Mach number 6 flight condition

A numerical study on the combustion flow field of an ethylene-fueled circular-section scramjet engine under Mach number 6 flight condition is conducted based on the RANS method. A pressure-related flamelet/progress variable model is used in the calculations, and the numerical results obtained are in good agreement with the experiments. Accordingly, the flame structure and combustion characteristics were analyzed for the high and low equivalence ratio cases. Calculations show that the high equivalence ratio case has a high level of heat release, forming a thermal congestion in the flow field, and that the premixed combustion and diffusion combustion together dominate the overall heat release. In the low equivalence ratio case, the center of the flow channel is still supersonic, and the diffusion flame dominates the overall heat release. In both cases, the jet leeward zone and the axisymmetric cavity are important reaction zones, where the former has a high heat release intensity, while the latter plays an important role in enhancing mixing and improving combustion efficiency.