Overdriven Gaseous Detonations

Abstract

The overdriven detonation waves, generated by the interaction of a Chapman-Jouguet (CJ) detonation with a conical insert in a circular tube and a wedge inserted into a flat channel, have been studied experimentally. In the case of an irregular (Mach) CJ wave reflection from the surface of the wedge or the conical channel, the Mach stem was an overdriven wave, whose velocity was 1.3 times the CJ velocity. The critical wedge angle and the critical angle between the conical channel and the axis of the tube were found to be 40 t 1 and 45 +, 1 deg, respectively. As these angles were decreased, the~Mach stem size increased, and its degree of overdrive decreased. The locus of the triple point in the flat channel was not self-similar, while it was nearly self-similar in the circular tube. The results indicated a direct correlation between the Mach stem size and the cell size in the CJ wave. For the mixtures: C?H~ + 2.502, 2H2 + 02, and CH4 + 202 at initial pressures from 0.05 to 1 atm, the pictures of an irregular reflection were identical when the cell size was the same. In the case of the secondary irregular reflection of the Mach stems at the centerline of the tube the generated wave velocity was about 1.6 times the CJ velocity and remained constant along the narrow channel for a distance of about two or three narrow channel widths. Presented at the 8th ICOGER, Minsk, USSR, Aug. 23-36, 1981. Copyright© American Institute of Aeronautics and Astronautics, Inc. 1983. All rights reserved. *Senior Researcher, Institute of Hydrodynamics. tResearcher, Institute of Hydrodynamics.