Nitric oxide formation in premixed flames of H 2+CO+CO 2 and air

Abstract

Burning velocity and probe sampling measurements of the concentrations of O2, CO2, CO, and NO in the postflame zone of the flames of H2+CO+CO2 and air are reported. The heat flux method was used for stabilization of laminar, premixed, non-stretched flames on a perforated plate burner at 1 atm. Axial profiles of the concentrations of major species were used to evaluate the influence of the ambient air entrainment and downstream heat losses. The influence of the downstream heat losses to the environment has been included in the modeling. The numerical predictions of the concentrations of O2, CO2, and CO in the postflame zone are in a good agreement with the experiment. The amount of the NO formed in the adiabatic flame front is significantly higher than that formed downstream. It is shown that in rich mixtures, where the NNH route forming NO is dominant, the heat losses do not affect significantly the calculated [NO]. The comparison of the experimental data with the detailed flame structure modeling strongly suggests a reduced value of the rate constant k1 for the reaction NNH+O=NH+NO. The calculations with k1=(1±0.5)×1014exp(−16.75±4.2 kJ/mol/RT) cm3/mol s bring the modeling close to the measurements not only in rich but also in stoichiometric and lean flames. The rate constant proposed in the present study is consistent with earlier evaluations within uncertainty limits.