Effect of Injector Configuration on Flame Stabilization in Confined Supersonic Flowpaths

Flame stabilization in confined supersonic flowpaths is challenging due to limited residence time, strong shock–boundary-layer interactions, and the difficulty in achieving efficient fuel–air mixing. Transverse jet injection enhances mixing by generating vortical structures and recirculation zones that support flame holding. However, a single jet entrains only a small portion of the crossflow, confining the flame to its wake. Multiple jets offer distributed fuel injection and stronger shock–shear interactions, potentially creating richer reaction zones, yet their stabilization behavior under reacting conditions remains insufficiently understood. This study examines ignition and stabilization by comparing single- and quad sonic ethylene jets injected into a Mach 3 crossflow. Simulations are performed using an in-house compressible solver with adaptive mesh refinement to resolve key flow and flame features. Both configurations use the same global equivalence ratio and jet-to-crossflow momentum ratio, isolating injector layout effects. The results show that confinement and fuel dispersion fundamentally alter the flame stabilization mechanisms: the single jet forms an autoignition-assisted jet-wake flame, whereas the quad jets sustain a shock-train-anchored autoignition jet stabilized flame. Overall, confinement and distributed injection strengthen shock–shear-layer interactions, promote turbulence and mixing in the jet wake, and create quasi-stable reaction fronts.