Research progress on strut-equipped supersonic combustors for scramjet application

Abstract Scramjets are regarded as one of the most efficient air-breathing propulsion devices in supersonic flight conditions, and combustors are critical components in scramjet engines. Effective flame stabilization is required in supersonic combustors to complete the process, including rapid mixing, continuous ignition, and stable combustion, of generating thrust in a short resident time of milliseconds order. Due to the complex flow conditions in the supersonic combustor, it is difficult to achieve efficient flame stabilization, therefore, an efficient fuel injector and flame holder are required. Struts are commonly used as the fuel injector and flame holder as they can enhance mixing and strengthen combustion. This study will present a review of the research progress made on supersonic combustors equipped with struts in recent decades. In this survey, the summary primarily covers the fundamental problems and recent advances regarding strut-equipped combustors in high-speed flow, including fuel injection and mixing enhancement, thermal protection, strut resistance characteristics, combustion stabilization mechanisms, and flame propagation processes. A number of relevant questions regarding future strut studies are provided, including the interaction mechanisms between combustion and flow, the coupling relationship between efficient combustion and efficient cooling, combustion optimization in multi-strut large-scale combustors, and the flame flashback mechanism inducing factors, that are essential for the improvement of combustor performance. Finally, guidelines for the optimization and performance improvement are provided for future research of the strut-equipped combustor.