Investigation of flow and combustion characteristics of a cavity-based scramjet combustor under different operation regimes

The flow and combustion characteristics of a cavity-based scramjet combustor in the dual- and scram-mode operation regimes are numerically compared, based on the novel self-adaptive turbulence eddy simulation (SATES) turbulence modeling coupled with classic eddy dissipation concept (EDC) combustion model. The SATES-EDC approach is extended to the scram-mode simulation (Mach number reaches 3.5) for the first time and shows good agreement with ground test experimental measurements. The validated results are then leveraged to demonstrate the physics of dual- and scram-mode operation, including flow structures and flame characteristics. Overall, the most significant difference between dual- and scram-mode regimes occurs in the primary combustion region. For the dual-mode operation, boundary layer separation and jet-wake mixing effect dominate the flame stabilization, whereas in the scram-mode regime, the primary combustion region is characterized by shock-enhanced combustion, as well as the flameholder cavity assisted jet-wake stabilized mechanism. Then, the subsonic/supersonic and diffusion/premixed combustion modes under two operation regimes are quantitatively compared by a statistical approach. The turbulence-chemistry interaction is also analyzed using the Damköhler number (Da)-turbulent Reynolds number (Ret) diagram. Finally, the flow, mixing, and combustion characteristics under the two operation regimes are quantitatively compared based on the efficiency indices. These findings underscore the potential of the SATES-EDC method for complex supersonic combustion scenarios and provide valuable reference for scramjet combustors under different operation regimes.