Shock-Tube Study of Chain Branching during the Induction Period of the Hydrogen—Oxygen Reaction

The growth of ``blue continuum'' emission has been measured during the induction period of the reaction of H2 (0.5%, 1.5%, and 5%)–CO (3.3% and 33%)–O2 (0.5%)–Ar mixtures between 1100° and 1700°K. For sensitivity, the reacting gas behind reflected shock waves was viewed axially through a large end plate window and lens. The observed intensity I, representing the integral of I′ (x)dx between reflected shock front and end plate, exhibited 2 to 3 decades of exponential growth, I = I0 exp(αt). α is related to the branching chain kinetics of H2–O2 combustion through the proportionality of I′ (x) to the product [CO][O]. α was found to be satisfactorily proportional to density and independent of [CO], and its dependence upon [O2] and [H2] was analyzed to yield rate coefficients for H+O2→ lim k1OH+Oand O+H2→ lim k2OH+Hbetween 1290° and 1667°K. These are represented by k1=1010.89 exp (−14.45 kcal/RT) liter mole−1·sec−1(±10%) over our range, and k2=1010.51 exp (−10.0 kcal/RT) liter mole−1·sec−1from combination of our mean result with literature data at 400°K.