Mechanisms of NO formation in MILD combustion of CH4/H2 fuel blends

Chemical kinetics calculations indicate that the conversion from NO to NO2 becomes significant and thus the relative importance of NO2 is increased in the total NOx emission under low temperature MILD conditions. As the reactor temperature is increased from 1100 K to 1600 K, the importance of N2O route decreases while that of thermal route increases. In contrast, as the initial mass fraction of oxygen is increased from 3% to 9%, the importance of N2O route increases but that of the prompt and NNH routes decreases. Likewise, as the equivalence ratio increases, the NO-reburning reaction becomes strong. Worth noting is that the N2O-intermediate route controls the NO production under fuel lean conditions whereas the prompt route is dominant in rich ones.