ID#: 137
Abstract Title: Direct Observations of Reaction Zone Structure in Propagating Detonations
Session Title: Detonation Structure
Session Date: 7/30/01
Session Start Time: 2:00 PM
Contributing Author: Shepherd, J.E.
Organization: California Institute of Technology
Country: USA
Authors: F. Pintgen, C.A. Eckett, J.M. Austin, J.E. Shepherd
Short Abstract: We report experimental observations on the reaction zone structure of self-sustaining, ``cellular'' detonations propagating near the CJ state in hydrogen-oxygen-argon mixtures. Two-dimensional crosssections perpendicular to the propagation direction were imaged using the technique of Planar Laser Induced Fluorescence (PLIF) and in some cases, compared to simultaneous pulsed-laser schlieren imaging. For the first time, images are obtained which clearly show the nature of the disturbances in an intermediate chemical species (OH) created by the variations in the strength of the leading shock front associated with the transverse wave instablity of a propagating detonation. The images are compared to two-dimensional, unsteady simulations with a reduced but realistic model of the chemical reaction processes in the hydrogen-oxygen-argon system. We interpret the experimental and numerical images using simple models of the detonation front structure based on the ``weak version of the flow near the triple point. Both the unsteady simulations and the triple point considerations are consistent with the creation of keystone shaped regions of low reactivity behind the incident shock near the end of the oscillation cycle within the ``cell'' created by two counterpropagating transverse waves.