Three-dimensional structure of stabilization of oblique detonation wave in hypersonic flow

Abstract

Detailed oblique detonation wave structure produced by a wedge at hypersonic speed (Mach number M =8.3) is studied experimentally using the oblique shock tube facility of the Laboratoire de Combustion et de Détonique (LCD) Laboratory. The flowfield induced by the wedge is visualized using multiframe schlieren and planar laser-induced fluorescence (PLIF) imaging. In addition, the story of the establishment and propagating phase of the structure is followed by smoked foil technique. Experiments performed in H 2 +2.38O 2 mixture show that onset of oblique detonation is triggered by oblique shock wave, after a delay corresponding to the chemical induction time. The basic configuration appears as a three waves structure issued from a triple point, that is, the oblique shock wave, the oblique detonation wave, and a transverse detonation wave. The transverse detonation wave is found especially overdriven. For relatively short induction time corresponding to an initial pressure of p o =0.5 bar, the triple point is fairly stable. Reducing the initial pressure ( p 0 ≤0.4 bar) causes the apparition of periodic instabilities: the triple point oscillates around an average position. These periodic instabilities seem to be linked to the chemical induction time. These instabilities correspond to an explosion behind the oblique shock wave and ahead of the triple point structure, giving birth to a new triple point, replacing the old one. At that time, computational fluid dynamics (CFD) models failed to simulate this structure and linked mechanism of instabilities. New improvements in modeling may provide better results.