Global reaction mechanisms for MILD oxy-combustion of methane

Highlights: • Seven global reaction mechanisms are systematically validated. • Comparisons are performed through both CFD and PFR simulations. • Our refined global mechanism significantly improves the prediction. • Our refined mechanism is a preferable global mechanism for MILD oxy-combustion. This paper optimizes global reaction mechanisms under the MILD (Moderate and Intensive Low-oxygen Dilution) oxy-combustion combustion. Seven global mechanisms are compared and validated with two detailed mechanisms under the oxy-fuel combustion, MILD air-combustion, and MILD oxy-combustion conditions. The ability of these global models to capture the combustion process under different conditions is compared first using computational fluid dynamics (CFD) simulations of both the MILD oxy-combustion in a laboratory-scale furnace and non-premixed turbulent jet open flames, and later using a plug flow reactor (PFR) approach. Experiments of the MILD oxy-combustion are also carried out for the mechanism validation. The detailed comparison shows that the present optimized global mechanism significantly improves the prediction of temperatures, equilibrium concentrations of major species, and the peak CO concentration, relative to other global mechanisms, for the MILD oxy-combustion. The present refined mechanism is an appropriate global reaction mechanism for methane MILD oxy-combustion, if the computational cost of detailed reaction mechanism is unaffordable.