Coupled analysis of supersonic combustion chamber with flame modes transition under fluid–thermal–structure interaction

The harsh environment and lightweight structure of the scramjet engine make the fluid–thermal–structure interaction (FTSI) effects significant. This paper conducts coupled analysis of a scramjet for 20 s, investigating the interaction between the thin-walled structure and supersonic combustion (result at 0 s as the benchmark without considering the FTSI effect). During the operation, the flame on the upper wall changes from the cavity-assisted jet wake-stabilized combustion into the cavity shear layer-stabilized combustion. While the lower flame gradually moves forward to the jet, the moving distance decreases with the inflow from Ma2.5 to Ma3.5. These variations induce the structural deformation mode from downward depression of the lower wall to upward bugling of the upper wall. Since the FTSI effects are evident for Ma3.0 inflow, an in-depth investigation of this condition is studied. For Ma3.0 inflow, a separation zone progressively emerges on the lower wall and it promotes the flame toward the jet, with the combustion changing into jet wake-stabilized mode. On the contrary, the backward moving flame on the upper wall delays the corner flow separation point toward the cavity. The performance parameters are also influenced by the FTSI effect. Inlet and outlet areas of the combustion chamber increase by 12% and 11%, respectively. The thrust undergoes the process of decreasing and then increasing.