Experimental study of ignition and combustion characteristics of ethylene in cavity-based supersonic combustor at low stagnation temperature and pressure

Abstract

At low inflow Mach number without throttling, since low static temperature the ignition and flame holding is still a big challenge in supersonic combustor. In this paper, the ignition and flame transient development in ethylene fueled cavity-based supersonic combustor are experimentally investigated at low conditions of stagnation temperature 950 K, pressure 0.82 MPa, and the isolator entrance Mach number 2.0. The results show ethylene can achieve successful ignition and stable combustion at low inflow Mach number with global equivalence ratios (ER) varying from 0.12 to 0.3. The combustion mode could be either supersonic or subsonic which depends on the ER. The combustion mode is supersonic stable combustion mode at ER = 0.12, 0.18 and 0.24 while the mode is subsonic stable combustion mode at ER = 0.27, 0.3. Owing to the better fuel/air mixing, ethylene injected from upstream position burns more intensively than that of downstream position at the same ER. It is also found that combustion and shockwaves are strengthened with each other until the balance between the pressure of shockwaves and the backpressure of combustion. This balance makes the flow structures and combustion keep stable. Comparing the combustion and shockwaves of different ER and injector position, the mutual promotion between combustion and shock wave is further demonstrated.