Analytical approximations for structures of wet CO flames with one-step reduced chemistry

Since hydrogen-containing species catalyze CO oxidation, at small H/C and H/O ratios steady-state approximations for reaction intermediaries should be accurate and should produce a good one-step reduced-chemistry approximation for describing the flame structure. Such an approximation is complicated, however, because of the many elementary kinetic steps involved. In the present work simplifications are introduced into a one-step approximation that enable analytical expressions to be obtained for the burning velocities of premixed laminar flames by asymptotic methods. The resulting burning velocities are shown to be in good agreement with experiment and with detailed numerical predictions, and qualitative aspects of the internal flame structure are shown to agree with those deduced from full-chemistry numerical calculations. Estimates are given of the ranges of conditions over which the approximations can reasonably be employed and of flammability limits controlled by chemical kinetics.