Mixing Enhancement Mechanism of Liquid Jet in Supersonic Crossflow with Gas Throttling

Abstract

Numerical and experimental studies were conducted to uncover the physical aspects of a liquid jet injected into a supersonic crossflow with gas throttling systematically. The results were obtained with the inflow conditions of a Mach number of 2.0, a total temperature of 300 K, and a total pressure of 0.55 MPa. The results show that fuel–air mixing is considerably enhanced due to shock-induced flow distortion by adding gas throttling. The strength of downstream backpressure determines the distance of forward movement of the throttling shock wave train and the flowfield structure in the channel. When the mass flux of gas throttling is high, the influence of throttling gas spreads across the expansion section, resulting in significant flow separation in front of the liquid jet. It is found that the spray flashback phenomenon is similar to the flame flashback phenomenon that occurs in the supersonic combustion process under the action of a precombustion shock train. The wall counterrotating vortex pair and induced cavity streamwise vortices are enhanced with the increase of the flux of gas throttling. The relatively high-pressure environment generated by gas throttling promotes the atomization of droplets. As a result, the mixing enhancement mechanism of a liquid jet in a supersonic crossflow with gas throttling is mainly due to the combined effects of 1) the shock waves separating the side wall boundary layer and modifying the local flow state of air in the combustor, which lead to a dramatic increase in fuel–air mixing, and 2) the streamwise vorticity values as well as the residence time resulting from channel blockage elevating.