A reduced mechanism for nitrogen chemistry in methane combustion

A four step mechanism for combustion of methane in perfectly stirred reactors with special emphasis on formation and destruction of hydrocarbon radicals has been developed using steady state and partial equilibrium assumptions for minor species. The reduced mechanism has been extended to include the nitrogen chemistry with NO and HCN as independent reactive species. The reduced nitrogen scheme includes thermal NO and prompt NO formation, as well as the NO to HCN recycle reactions, and conversion of HCN to NO and N2. We have tested the reduced mechanism by comparing perfectly stirred reactor calculations performed with full and reduced chemistry over a wide range of stoichiometries, temperatures and residence times. The reduced model generally provides a good description of the methane oxidation process as well as formation and destruction of nitrogen oxides. However, at low temperatures or very fuel-rich conditions reduced model predictions deteriorate, partly due to neglection of the C2-chemistry and partly because the OH partial equilibrium assumption becomes less accurate.