Low-Btu gas mixtures—I. Methane oxidation rates for a wide range of equivalence ratios

We present estimates for the effective oxidation rates of methane over a wide range of equivalence ratios using Ar as primary diluent and CO or H2O as additives. The rate of disappearance of methane has been monitored in a fuel-rich CH4 O2 Ar mixture by direct measurements of the change in transmission for He-Ne laser radiation at 3.392 μ behind reflected shock waves. The rate of formation of water with time has been obtained in independent absolute i.r. emission measurements near 6.75 μ on stoichiometric CH4 O2 Ar mixtures with and without added water. We have found empirically that a number of data correlations may be used and that the overall rates of disappearance of CH4 and of formation of H2O were the same during the post-induction period behind reflected shock waves. The rates of concentration changes with time to which we refer are average rates observed during the post-induction periods. The temperatures (Tmax) for which the oxygen-atom concentrations are a relative maximum were found to be close to the arithmetic means between the initial temperatures (T5) behind reflected shock fronts and the final equilibrium temperatures. The numerical values found for the correlation parameters as functions of the temperature during the post-induction oxidation are not sensitive to the prior admixture of CO or H2O but vary with mixture ratio.