Direct Observations of Reaction Zone Structure in Propagating Detonations
CALIFORNIA INST OF TECH PASADENA GRADUATE AERONAUTICAL LABS
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We report experimental observations of the reaction zone structure of self-sustaining cellular detonations propagating near the Chapman-Jouguet state in hydrogen-oxygen-argonnitrogen mixtures. Two-dimensional cross sections perpendicular to the propagation direction were imaged using the technique of planar laser induced fluorescence PLIF and in some cases, compared to simultaneously acquired schlieren images. 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 instability of a propagating detonation. The images are compared to two-dimensional, unsteady simulations with a reduced 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 or intersection of three shock waves, two of which make up the shock front and the third corresponding to the wave propagating transversely to the front. Both the unsteady simulations and the triple point calculations 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.
- Lasers and Masers
- Radiofrequency Wave Propagation