Inlet Static Pressure Ratio Effect on Vortex Structure Downstream of the Flameholder in Subsonic–supersonic Mixing Flow

The flow field characteristics downstream of the evaporative flameholder in the subsonic–supersonic mixing flow were experimentally investigated. The study focused on examining the effects of different inlet static pressure ratios characterized by supersonic and subsonic flow parameters. The results indicated that the increase in the static pressure ratio enhanced the fragmentation of the multiple vortices downstream of the flameholder located in the subsonic mainstream. It also exacerbated the asymmetry in the recirculation zone downstream of the flameholder and strengthened the tendency of the fluid to flow from one vortex to another. The regions with higher vorticity were mainly concentrated in the subsonic–supersonic shear layer between the subsonic and supersonic mainstream and the subsonic–subsonic shear layer region downstream of the flameholder. Furthermore, an increase in the static pressure ratio widened the range of peak distribution while reducing the magnitude of the peaks. The recirculation zone downstream of the flameholder exhibited four distinct changes in the vortex structure as the static pressure ratio increased from 1.07 to 1.96. These typical changes in the vortex structure observed are as follows: asymmetric dual-vortex structure, single vortex structure (away from the supersonic mainstream region), asymmetric dual-vortex structure, and single vortex structure (near the supersonic mainstream region).