Parametric Computational Studies of NOx Emission Reduction in Staged Combustion of Ideal Fuel-Air Mixtures1

Abstract

This paper is the second of series of articles devoted to computational studies for optimization of the combustion of fuel-oxygen mixtures with combustion chamber exhaust temperatures of 1600°C or more while meeting pollution emission standards. Calculations of the combustion of ideally mixed fuel-air mixtures in a combustor consisting of two sequentially positioned (staged) combustion volumes, each with its own burner, are presented. The first burner is a traditional low-emission combustion chamber with combustion of a pre-mixed fuel-air mixture with a swirler and a pre-mixing chamber, and pilot and main burners. The second burner lies downstream in the flow and a fuel-air mixture with a different composition is fed into it through a special aperture; this mixture is burnt in a medium with reduced oxygen content and a high temperature. The distribution and composition of the fuel-air mixture feeds between the two burners are optimized to attain minimum NO_x emissions for outlet temperatures of 1700°C. The optimum length of the second combustion volume is determined for complete burnup of the fuel with minimum concentrations of the oxides of nitrogen and carbon at its outlet. The results can be used to evaluate the minimum possible level of nitrogen oxide emissions attainable in the sequential combustion scheme for ideally mixed fuel-air mixtures.