Nox in parametrically varied methane flames

Fifteen laminar premixed methane-air flames are computed in the pressure range 1–10 atm. and the equivalence ratio range 0.6–1.0. The kinetic scheme includes thermal and prompt NO x , C 2 chemistry and pressure fall-off data for the kinetic rates. Sensitivity analysis shows the influence of pressure and the relative contributions of the different NO x mechanisms. NO x is insensitive to pressure in very lean flames. Thermal NO x dominates in stoichiometric flames, while prompt NO x and N 2 O mechanisms have an influence in the lean flames. The prompt NO x reactions are more influential in NO 2 than in NO production. NO 2 peaks early due to reactions between HO 2 and NO diffusing forward into the cool part of the flame, and then decays to 1% or less of NO. Reactions which control flame speed are very influential on NO. Based on mass fractions, CH scales as CH 4 ·OH·H in the 10 atm. flame, suggesting a simplified scheme for prompt NO x .