Reactions of initiation of the autoignition of H2–O2 mixtures in shock waves

Abstract

The initiation of the autoignition of hydrogen–oxygen–argon mixtures behind reflected shock waves is studied by absorption and emission spectrophotometry in the temperature range of 960 < T < 1670 K at pressures of ~0.1 MPa. Introduction of Mo(CO)₆ additive in an amount of ~80 ppm made it possible to study the effect of O atoms on the shortening of the ignition delay time of H₂–O₂–Ar mixtures. A kinetic modeling of our own and published experimental data at temperatures of 930 < T < 2500 K and pressures of 0.05 < P < 8.7 MPa enabled to establish how the initiation reactions influence the process of self-ignition and to evaluate the rate constant for one of the initiation reactions: k(H₂ + O₂ → 2OH) = (3 ± 1) × 10¹¹exp(–E_a/RT), cm³ mol^–1 s^–1, where E_a = (40 ± 2) kcal/mol.