Review of combustion stabilization for hypersonic airbreathing propulsion

A review of fundamental research in combustion stabilization for hypersonic airbreathing propulsion is presented. Combustion in high-speed airbreathing propulsion systems demands stable flame distribution and chemical reaction to provide reliable thrust over a wide flight envelope. Various methods have been developed to stabilize combustion depending on the hypersonic regime. For low hypersonic conditions, combustion occurs mainly in the diffusive mode in which the gas/liquid fuels are injected into supersonic freestreams for simultaneous fuel-air mixing and chemical reaction. Flame stability is generally enhanced by improved mixing, physical flameholding, and external energy addition. In higher hypersonic conditions, partially/fully premixed combustion relying on shock induced stabilization becomes more dominant. In such cases, flame stabilization can be achieved through alternative means such as radical generation and standing oblique detonation waves. The review outlines both experimental and numerical research progress made towards combustion stabilization over the entire hypersonic regime, and intended to lay the groundwork for further studies which can provide optimized design guidelines for the next generation of high-speed airbreathing propulsion systems.