On the structure of an impinging jet with flow swirl and burning

The PIV and PLIF OH methods were used to experimentally study the structure of a jet impinging on a flat surface with swirl and combustion of a propane-air mixture with an equivalence ratio of 0.7 at distances between the nozzle and the surface $H/d$ = 1 and 3 and in the absence of the impinged surface. The swirl parameter was 0.41 and 1.0, and the Reynolds number was 5000. It is concluded that for both values of the swirl parameter, the presence of the surface leads to the formation of an extended central cone-shaped recirculation zones. For $H/d$ = 3 and 2, the intensity of OH fluorescence near the impinged surface and inside the recirculation zone significantly reduced. This effect is presumably caused by a decrease in the temperature of combustion products in the recirculation zone, including in the neighborhood of the flame front.