Flame stabilization enhancement in a strut-based supersonic combustor by shock wave generators

Abstract

An experimental study was performed to investigate the effect of shock wave generators (SWGs) and equivalence ratio on the combustion mode of a strut-based supersonic combustor. The Mach number, total pressure, and stagnation temperature of the inflow were 2.92, 2.6 MPa, and 1650 K. Ethylene with a global equivalence ratio ranging from 0.15 to 0.35 was used as the primary fuel. Hydrogen with a global equivalence ratio of 0.1 was used to ignite the combustor but it was shut down when auto-ignition was achieved. It was found that the SWGs elevated the temperature and pressure of the strut wake, which significantly accelerated the auto-ignition process. After shutting down the hydrogen, the flame in the combustor without a SWG extinguished in 20 ms because the recirculation flow was too small to hold the flame. In stark contrast, a stable combustion was attained in the combustor with SWGs when the hydrogen was shut down. The reason for this phenomenon was that the SWGs increased the residence time of the combustible mixture by extending the length of the recirculation flow. The SWGs also reduced the ignition delay time of the combustible mixture via increasing the local static temperature. The investigation on the equivalence ratio indicated that the flame chemiluminescence and the width of the flame brush increased when more ethylene was supplied. However, no considerable change of the combustion mode was witnessed when the equivalence ratio increased from 0.15 to 0.35. Using the present experimental setup, the size of the recirculation flow and the combustion mode were mainly dominated by the SWGs.