Numerical Study of Mixing Enhancement by Shock Waves in Model Scramjet Engine

A numerical study has been conducted to investigate the effect of shock waves on the supersonic hydrogen-air jet flame stabilized in a Mach 2.5 circular cross-section combustor. The numerical model utilizes multispecies Navier-Stokes equations with detailed chemical reaction models and employs a k-w shear stress transport model. A wedge is mounted on the side wall of the combustor in order to find the interaction of the oblique shock waves with the hydrogen-air jetlike flame. The interaction between the shock waves and the mixing layer is classified according to the increasing tendency of the growth rate of the mixing layer downstream of the shock waves. It is found that the shock waves create a radially inward/outward airflow to the flame and elongate a flame-holding recirculation zone, and thus fuel-air mixing is enhanced significantly, resulting in improved combustion efficiency. Also, the overall performance is investigated by changing the shock position and considering the mixing/combustion efficiency and total pressure loss in a model scramjet combustor. Because there exists a tradeoff between the enhanced mixing/combustion efficiency and the decreased total pressure recovery, it is suggested that the optimized shock position needs to be determined in order to obtain the maximum overall combustor performance using the overall performance index. [PUBLICATION ABSTRACT]