Ignition of hydrogen-oxygen mixtures in reflected shock waves

Abstract

The ignition anomaly that has been known to occur behind reflected shock waves in oxy-hydrogen systems below the temperature corresponding to the extrapolated value of the second explosion limit was studied. During the study particular attention was given to the effects of exothermic energy release due to chemical reaction. Average translational temperatures were determined by measuring both pressure and density in a thermoneutral gas system of different specific heat ratios, γ's. In this case the experiments did not show the gradual increase of temperature which was considered to be due to the boundary layer effects. Also measurements of the temperature rise in the course of the induction period, as manifested by the absorption hydroxyl radical, were performed under conditions of various amounts of exothermic energy release per unit mass of the medium and for different values of γ. On this basis it was found that when the exothermic effects are relatively small, the temperature rise of the substance can be evaluated from gasdynamic and chemical kinetic analysis of a homogeneous gas system, but when the exothermic effects are large this calculation was shown to be invalid. It is suggested that the main reason for this invalidity is associated with the significant amount of inhomogenity caused by exothermic processes.