Post-induction kinetics in shock-initiated H 2−O 2 reactions

Abstract

The course of the shock-initiated hydrogen-oxygen reaction after the induction period, during the transition to partial equilibrium, has been investigated by computer integration of the rate equations, and interpretations of particular aspects are developed. H2:O2 ratios far from stoichiometric are considered. An earlier suggestion by one of the authors that partial equilibrium conditions with no recombination represent a practical upper limit to the transient atom and radical concentrations is contradicted, and attention is focused on the pronounced “spike” in oxygen-atom concentration that modern rate-coefficient data predict to occur in fuel-rich mixtures at the time of maximum reaction rates and most rapid O2 depletion. Determination of the time duration and amplitude of O “spikes” in rich mixtures, which we have not yet accomplished, offers the possibility of direct information on the rate coefficients for the reactions H + O 2 → k a O H + O O + H 2 → k b O H + H Failure of measured OH-concentration profiles to exhibit such “spikes” in rich mixtures over the range 1160°≤T≤1884°K places an upper bound on the ratio ka/kc O H + H 2 → k c H 2 O + H