Study on the Influence of Excess Air Coefficient and Swirl Number on Combustion Characteristics of Natural Gas
The effects of excess air coefficient and swirl number on temperature distribution,velocity dis-tribution and NOx generation in the combustion chamber of WNS gas boiler when natural gas diffused and burned in O2/N2 atmosphere were addressed.The numerical simulations were carried out by using CFD software,the standard k-ε turbulence model,P-1 radiation model and eddy dissipation model.Based on the swirling effect on dynamic flow behavior,the swirl number S was used to express the swirling in-tensity of the inlet air.The results show that in the process of increasing the excess air coefficient α from 1.0 to 1.3,the diameter of the flame gradually decreases,the exhaust gas temperature decreases,and the mass fraction of NOx at the outlet of the combustion chamber gradually decreases;in the process of increasing the number of air swirls from 0 to 0.8,a central recirculation zone is formed in the combustion chamber,the radial flow distribution of the flame is gradually improved,and the temperature distribution in the combustion chamber is more uniform;the temperature distribution of the central axis of the swirling combustion flame is higher than that of the straight-flow jet combustion,and increasing air swirl number can effectively reduce NOx mass fraction.
gas boilerexcess air coefficientswirl numbernumerical simulation