Development and Application of an Eight-Step Global Mechanism for CFD and CRN Simulations of Lean-Premixed Combustors

In this paper, the development of an eight-step global chemical kinetic mechanism for methane oxidation with nitric oxide formation in lean-premixed combustion at elevated pressures is described and applied. In particular, the mechanism has been developed for use in computational fluid dynamics and chemical reactor network simulations of combustion in lean-premixed gas turbine engines. Special attention is focused on the ability of the mechanism to predict $NOx$ and CO exhaust emissions. Applications of the eight-step mechanism are reported in the paper, all for high-pressure, lean-premixed, methane-air (or natural gas-air) combustion. The eight steps of the mechanism are as follows: (1) oxidation of the methane fuel to CO and $H2O$⁠, (2) oxidation of the CO to $CO2$⁠, (3) dissociation of the $CO2$ to CO, (4) flame-NO formation by the Zeldovich and nitrous oxide mechanisms, (5) flame-NO formation by the prompt and NNH mechanisms, (6) postflame-NO formation by equilibrium H-atom attack on equilibrium $N2O$⁠, (7) postflame-NO formation by equilibrium O-atom attack on equilibrium $N2O$⁠, and (8) postflame Zeldovich NO formation by equilibrium O-atom attack on $N2$⁠.