Numerical simulation of low NO_x emission three-stage burners for double-P type radiant tubes based on orthogonal test

A kind of three-stage burner for double-P type radiant tubes was designed by using diffusion-type low-NO_x-burning technology. Numerical simulation was performed to verify the model. The structure and operation parameters of the burner were analyzed by orthogonal test and single factor analysis. The research results show that air preheating temperature,air staged proportion and excess air coefficient have significant effect on the outlet NO_x emission concentration without mutual interaction. When the primary air increases from 10% to 20%,the amount of NO_x increases from 65.2×10^-6 to 108.2×10^-6; but when the primary air increases to more than 30%,the outlet NO_x concentration increase rate decreases. The maximum combustion temperature increases about 50℃ with each increase in air preheating temperature of 100℃,and the NO_x emission concentration increases from 50.9×10^-6 at the rates of 22%,23.2%,25.3%,27.2%,27.3% and 29.5%. With the increase of excess air coefficient,the outlet NO_x concentration increases from 82×10^-6 at the rates of 22.1%,1.9%,2.1%,24% and 2.5%.