Numerical Study on the Influence of Inlet Air Swirl Intensity on Diffusion Combustion Characteristics of Low Calorific Value Coalbed Methane
China is rich in coalbed methane resources,its reserves rank third in the world,but the utilization rate is very low,and the utilization form is single,especially the low calorific value coalbed methane extracted underground.Because the methane concentration is only 10%-30%,at present,it mainly adopts the way of emptying,resulting in huge energy waste and environmental problems.Swirling combustion technology,by orga-nizing fuel or oxidant into the burner in a swirling way to form a jet,using swirling combustion to optimize the combustion conditions,can effectively improve the combustion intensity and significantly improve the stability of the flame.A large number of engineering practices have verified that swirl combustion technology is suitable for the combustion of low calorific value gas.In this paper,the swirl combustion model of low calorific value coalbed methane is established by computational fluid dynamics.Based on the comparison and verification with the data of related literatures,the relationship between the swirl intensity of air incidence and the diffusion com-bustion characteristics of low calorific value coalbed methane is numerically simulated from the aspects of swirl flow field,flame temperature and radiation heat transfer.The results show that When the swirl number increas-es from 0 to 0.6,a recirculation zone is formed in the furnace,and the combustion products are generated in the inner recirculation zone.Fuel and air can be mixed more effectively,thus eliminating the high temperature zone,reducing NOx emissions and improving combustion efficiency.In addition,with the increase of swirl num-ber,the distribution of radial flow field is improved.Although the maximum flame temperature decreases,the flame heat transfer area increases,which makes the radiation efficiency increase by 36.5%and NOx emission decrease by 58.6%.In order to solve the two opposite and contradictory problems caused by swirl intensity to stable ignition,the swirl number should be controlled between 0.3 and 0.4.
Low calorific value coalbed methaneSwirl combustion technologySwirling intensityNumerical simulation
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