Visualization of flame structure in supersonic combustion by Planar Laser Induced Fluorescence technique

Planar Laser Induced Fluorescence (PLIF) can be used to visualize the flame structure with high temporal and spatial resolution and investigate the mechanism of supersonic combustion. In this paper, OH-PLIF and CH-PLIF techniques were used to study the flame structure in supersonic combustion. The cavity-stabilized reaction zone structure of the three streamwise sections and two spanwise sections in a supersonic combustor was obtained by using the OH-PLIF technique. The experimental results show that the combustion occurs in the inner cavity and the OH radicals are distributed symmetrically along the central axis at a low global equivalence ratio. The OH radicals are primarily distributed at two-side-wall of the combustor and the location of the flame is higher than that of the cavity at a high equivalence ratio. The heat-release structure of the cavity-stabilized flame was observed by the CH-PLIF technique. It is found that the heat-release zone is highly wrinkled and distorted in the supersonic combustion and it is distributed in a narrower region than the reaction zone.