Effects of supersonic film cooling on shock wave/boundary layer interaction in a scramjet combustor

Many efforts have been put on the study of shock wave/boundary layer interaction (SWBLI) due to its complexity and importance. In hydrogen or hydrocarbon fueled scramjet combustors, fuel film injections will significantly modify upstream boundary layer characteristics, and further increase the SWBLI complexity. In this paper, the effects of hydrogen and hydrocarbon fueled film injections on SWBLI are numerically studied. The results indicate that, interaction length and separation characteristics induced by oblique shock wave impingement are significantly different with different foreign-gas supersonic film injections. Hydrogen injection increases interaction length and further expands flow separation region compared with that without injection. On the contrary, hydrocarbon fuel n-Decane injection decreases interaction length and effectively suppresses flow separation. It is found that, the effects of foreign-gas supersonic film injections on interaction length are attributed to the variations of subsonic layer thickness and momentum in the boundary layer, which are mainly determined by molecular weight and density properties of foreign-gases. Moreover, the effects on separation length depend on comprehensive effects of near-wall momentum and wall shear stress. Meanwhile, the waves structures are also significantly different with hydrogen or hydrocarbon fuel due to different separation characteristics. The interesting thing is that, as shock impingement position moves downstream, separation length decreases with hydrogen film injection, however increases with n-Decane film injection due to different mixing layer growth rates. Therefore, high-molecule foreign-gas film injection with shock impingement position moves upstream could be helpful to weaken the interaction and suppress the flow separation of SWBLI.