Chemical Kinetics for NO Emissions in System of Methane-Air Turbulent-Jet Diffusion Flame

An explicit expression for local, instantaneous NO production rate model was proposed to simulate NO formation in turbulent methane-air combustion. The average production rates of mixture fraction and scalar dissipation were obtained from asymptotes through approximation of two single-variable probability-density function. The theory predicted significant contributions from the Zeldovich mechanism, but negligible contributions from the nitrous-oxide mechanism in the oxygen-consumption zone. The proposed model was used to simulate NO formation in the pilot methane-air jet diffusion combustion. The simulation results were compared with those obtained by the CFD software FLUENT module. Validation of predictions with the experimental data given by Sandia National Laboratory of the USA indicates that the proposed model yields better results than other models, and the deviation is under 50/0. And in some complete reaction zones, the simulation results are even the same as the experimental data. Realizable k-ε model, Reynold stress model and standard k-ω model were also investigated to predict the turbulent combustion reaction, which shows that the simulation results of velocities, temperatures, and concentrations of combustion productions by standard k-ω model are in accordance with the experimental data.