Scramjet Plasma Ignition and Assisted Combustion Technology Review

The use of plasma technology to assist scramjet ignition and combustion has been a research hotspot in the field of supersonic propulsion technology. This paper summarizes the main mechanisms of plasma aerodynamic, thermal, and activity effects and their roles in enhanced fuel mixing, ignition, and combustion in scramjets, before reviewing the main research results of plasma technology applied to the above three scramjet stages, focusing on research progress related to different discharge forms of plasma ignition and combustion technologies. Research shows that plasma based on the triggering of aerodynamic disturbances and thermal effects, through interaction with shock waves, control the flow structure to promote the generation of a vortex structure, improve the thickness of the mixing layer, enhance jet instability, to achieve mixing efficiency. The plasma ignition field has matured, with short ignition time delays, flameout limits, and improved ignition efficiency. However, different conditions—such as the nature of the plasma jet working gas and ignition location—can have a considerable impact on the ignition success. Limited by the complexity of the plasma-enhanced combustion research results focused on the description of phenomena and changes in the law, the research mechanism is relatively constrained, but it has been shown to enhance the flame propagation speed, increase flame intensity, suppress combustion oscillations, and improve combustion efficiency. Finally, the difficulties and problems associated with the current research on plasma ignition and enhanced combustion are analyzed.