Flame-Holding Behind a Wedge by Incident Shock Waves

Abstract

Flame holding is an essential technology for SCRAMJET combustors especially under low Mach flight conditions, which make the airflow temperature low. An interesting technique for the flame holding is the utilization of shock waves. This study investigated their effects on the flame holding by use of a two-dimensional wedge-shaped strut in supersonic flow of Mach 2.5. The primary objectives were to investigate flame-holding characteristics and to obtain a better understanding of the fluid dynamic processes of the interaction between incident shock waves and a wake behind the strut and on their effects on the combustion phenomena. Experiments in a supersonic wind tunnel showed that the incident shock waves achieved the stable flame holding within air total temperatures of 550K through 800K. Laser Doppler Velocimeter measurements and shadowgraph visualization showed that a large recirculation flow was established and the wake region behind the strut was expanded by incident shock waves. Numerical simulation by a two-dimensional compressible flow code with one-step irreversible reaction model was also conducted to investigate the structure of the wake flow and the ignition process and to predict the flame-holding conditions. The results showed the expansion of the wake region and the formation of a large recirculation zone, as shown by the experimental observations, and the flame-holding and the blow-out conditions had the same trends as the experimental data.