Overview on the research progress of unsteady supersonic combustion

Supersonic combustion process in a scramjet engine has been investigated widely for decades. With digging deeper into the supersonic combustion issues, the hot spot of supersonic combustion studies has been shifted gradually from quasi-steady state such as flame stabilizations to unsteady state such as combustion fluctuations. Nowadays, unsteady supersonic combustion and its control strategy become a challenge for real scramjet engine applications. This paper investigates unsteady supersonic combustion processes and gives a comprehensive review on five typical unsteady supersonic combustion phenomena, which include acoustic oscillation in scramjet engines, combustion instability induced by flow unsteadiness, ignition, flame flashback, and flame behaviors near blowoff limits. The recent research progress on these issues has been overviewed. Fundamental mechanisms of the typical unsteady supersonic combustion are discussed, and some established models and control strategies are given. Finally, suggestions for further conducting unsteady supersonic combustion investigations are proposed.