Plif imaging of hypersonic reactive flow around blunt bodies

Abstract

Qualitative OH planar laser-induced fluorescence (PLIF) imaging experiments of supersonic reactive flows over a 40° wedge and a 19-mm-diameter blunted cylinder are reported. Hydrogen-, ethylene-, and methane-based mixtures have been used in this work. Three different free stream conditions. M∞=6.7, 5.2 and 4.2, were used to study the combustion modes around the wedge and blunted cylinder. Separate schlieren imaging results were also obtained for several of the test cases, providing complementary shock wave visualization. In several cases for the wedge, shock-induced combustion was observed a finite distance behind the nonreacting oblique shock wave. For the most sensitive hydrogen mixture, an oblique detonation occurred in which the shock wave and combustion front were fully coupled. In the experiments with the blunted cylinder, two different regimes of combustion were observed. When the velocity of the flow was larger than the CJ velocity of the mixture, the mode was that of an adiabatic shock followed by a smooth combustion front. For cases of flow velocity similar to the CJ velocity or less, regular oscillations were observed on the image and in the stagnation pressure history. These observations are qualitatively consistent with previous work.