Spatial structure of a reacting flow of a turbulent swirled jet during combustion of a propane-air mixture

Results of an experimental study of the spatial structure of a reacting flow during combustion of a propane-air mixture in a turbulent swirled jet escaping into atmospheric air are presented. The fuel-to-air equivalence ratio is $\phi= 0.7$, and the Reynolds number of the jet is $\operatorname{Re}= 5\cdot10^3$. The time-averaged spatial distributions of velocity, local density, and concentrations of the main species of the gas mixture are measured under the conditions of moderate and intense swirling of the flow. In both cases, the flame front is stabilized in the internal mixing layer formed by the axial region of jet deceleration, where hot combustion products are concentrated. In the case of intense swirling of the flow, the temperature distributions in the cross section $y/d=0.5$ show that the region with the maximum temperature of the gas is located at the periphery of the central recirculation zone. In the case of intense swirling of the flow, there is a recirculation region at the axis, and the $\mathrm{CO}_2$ concentration is twice higher than in a moderately swirled jet. The opposite situation is observed for $\mathrm{O}_2$.