NO_x emission in a stretched methane air counterflow diffusion flame

The effect of strain rate on NO_x emissions in a methane air counterflow diffusion flame is numerically analyzed with detailed chemistry. First, the kinetic mechanism is revised and tested by introducing ammonia into the fuel. Comparison of the experimental results with the computed results showed that NO formation is well predicted by the present detailed chemistry. NO_x formation at high air temperature is then calculated by increasing the strain rate from 10 s^-1 to 12 800 s^-1. The results showed that NO_x emission decreases dramatically with the increase of strain rate and that extinction limit is greatly extended with the increase of air temperature. Furthermore, the sensitivity and production rate analyses are made. Important elementary reactions and formation routes corresponding to NO_x emissions at different strain rates are presented and discussed. Comparisons between prompt NO_x and thermal NO_x are made. Quenches of thermal NO_x and NCO and CN recycle routes at high strain rate are identified.