NOx and fuel emissions in combustion of hydrogen/air mixtures near inert surfaces

Combustion of premixed H-2/air flames near inert surfaces was studied numerically using detailed chemistry and multicomponent transport. The roles of inlet composition, radiative loss from the surface, and thermal quenching by cold walls in NOx and fuel emissions were analyzed. It is shown that the bifurcation behavior in terms of extinguishability strongly determines the role of thermal quenching in emissions. For weak, extinguishable flames, thermal quenching at the surface effectively reduces NOx emissions, although at the cost of higher fuel emissions. Strong, nonextinguishable flames at low strain rates are practically unaffected by thermal quenching except for an increased NO2 mole fraction near the surface.