An experimental study on shock-induced combustion of isolated regions of hydrogen-oxygen mixtures.

Abstract

The interaction of a strong plane shock wave with isolated regions of gaseous mixtures was examined through a series of shock tube experiments. Specifically, the non-uniform mixtures examined consisted of a spherical bubble of pure hydrogen or hydrogen-oxygen mixtures surrounded by either an oxygen, nitrogen or air atmosphere. Shocks in the range of Mach 1.7 to 3.7 were studied. The interaction events where recorded with high speed shadowgraphs and pressure trace recordings. No chemical reactions were observed in the interactions of shocks with strengths up to Mach 3.7 with pure hydrogen spheres due to inadequate mixing of the reactants. In addition no reaction was observed for shocks up to Mach 3.0 for premixed spheres of equivalence ratios of 1.0, 0.7, and 0.5. However, shock induced combustion was observed for incident shock strengths above Mach 3.0. This demarcation between reaction and non-reaction corresponds to the classical third explosion limit for a hydrogen-oxygen mixture. Measurements of the induction period for hydrogen-oxygen mixtures for pressure and temperature conditions near the third explosion limit are also reported. This data will aid the study of the initiation and propagation of detonation waves and provide a useful set of test data for computational fluid dynamics codes involving reactive flows.