A review on the flame holding mechanisms used for the development of scramjet engines

Abstract

The air-breathing engine is a promising candidate in building the future of the hypersonic industry. These engines do not carry any fuel oxidizers, uses atmospheric oxygen to undergo the combustion process. The papers review the importance, fundamental principle, history of development, challenges in the scramjet engines. It subjectively studies different experimental and computational analyses conducted by research around the globe to understand the effect and importance of flame holders in the supersonic combustion process. From the literature, it has been identified that due to supersonic combustion inside the combustor, the time available for fuel-air mixing is less. There is insufficient burning of fuel which leads to wastage, ignition, atomization, etc. To overcome the issue the flame holders are introduced into the combustor. The flame holder provides area for combustion along with the formation of vortices in the combustor. This results in the formation of a recirculation region, which enhances the combustion phenomenon in the combustor. Additionally, additional shock waves are formed that lead to the interaction of shock waves. The turbulent flow inside the combustor is very complex, however proper understanding of the physics behind the formation and interaction of the shockwaves with the boundary layer is yet to be estimated in the near future.