Research progress of the flow and combustion organization for the high-Mach-number scramjet: From Mach 8 to 12

Abstract

The recent groundbreaking advancements in Mach 4–7 combustion organization technology have paved the way for a significant expansion of the operational envelope for scramjets, enabling them to reach higher Mach numbers. By meticulously designing the compression ratio of the hypersonic inlet, the flow parameters at the entrance of the combustor can be effectively managed, thereby facilitating the autoignition of the reactant gas mixture. However, the challenge of achieving efficient combustion in a hypersonic environment escalates considerably. This paper delves into the intricacies of the reacting flows within high-Mach-number scramjets through a comprehensive literature review, segmented into three key technical fields. Firstly, the real gas effects in high-temperature hypersonic flows are given more attention, offering an in-depth examination of the physical and chemical properties of nonequilibrium flows. It also elucidates the sources of internal resistance in the flow path and the mechanisms behind the drag reduction achieved through boundary layer combustion. Subsequently, the paper synthesizes various strategies to enhance the efficiency of fuel/air mixing and combustion. These include advancing the injection position to prolong the fuel's flow residence time, employing porous, pulse injection, and oxygen supplementation techniques to boost the local premixing of combustible gases, and utilizing vortex generators to create large-scale streamwise vortices or recirculation zones that foster mixing. In summary, the paper provides an overview of combustion stabilization modes and mechanisms controlled by mixing in different combustion configurations. Building on this analysis, it uncovers the significant influence of thermochemical nonequilibrium effects on flow, ignition and flame stabilization, shedding light on the complexities of scramjets at high Mach numbers.