Modelling of chemical kinetics of methane/nitrogen dioxide/oxygen flames

Abstract

A chemical kinetic model is developed to describe mechanism of different laminar, one-dimensional, premixed, sub-atmospheric pressure, flat CH₄/NO₂/O₂ flames. All the flames considered are lean with equivalence ratios ranging from 0.20 to 0.92. The developed chemical kinetic mechanism consists of 101 elementary reactions among 30 different species. The developed chemical mechanism computes the concentration of stable species CH₄, CO₂, CO, H₂, O, H₂O, N₂, NO, NO₂ and N₂O and radical species CH₃, CH₂, CH₃, CHO, CHO, HCO, H, O, OH, HO₂, H₂O₂, NH, CN, HCN, HNO₂, HNO, NCO, HNCO, N₂H and NH₂, as a function of distance above the surface of the burner. The comparison between the calculated and experimental concentration profiles shows good quantitative and qualitative agreement for the stable species H₂O, NO₂, NO, N₂, CO, CO₂ and for the radical species OH, CH, CN, NH and NH₃. Concentration values of CO₂, CO, H₂O, N₂, NO and NO₂, and peak concentrations of CH, NH and CN are plotted against the equivalence ratio and compared with the experimental data. The results of these plots support the validity of the eveloped chemical mechanism for accurate prediction of the behaviour of CH₄/NO₂/O₂ flames. The formulation of this mechanism is useful in understanding the nitrogen chemistry controlling the combustion of gas phase in solid rocket propellants and in reducing pollutant formation in the atmosphere.