| Metal fiber burners are applications of porous media combustion technology and are widely used in various types of boilers.Compared with traditional diffusion burners,metal fiber burners have the advantages of low NOx emissions,high combustion strength and high tempering safety.To further reduce the amount of nitrogen oxides produced during the combustion of natural gas metal fiber burners,this paper begins with the improvement of the mixing effect of natural gas and air in the mixture chamber of metal fiber burner,designs the mixture structure,and optimizes the mixture structure parameters based on the orthogonal test.Based on the improvement of the mixing effect of natural gas and air in metal fiber burners,the aeration structure was designed.The mixing unevenness is used as the evaluation of the mixing effect of the aeration structure,through the numerical simulation method,the four research objects: air flow,blade angle,number of blades,number of gas distribution rings,and single-factor influence analysis of aeration effect were obtained,and the influence trend of each single factor on the mixing unevenness was obtained.The results show that under the single factor variation,the air flow rate and the swirling blade angle have a great influence on the mixed unevenness trend,and the number of blades and the outlet of the gas distribution ring are several times.In order to obtain the optimal mixing effect,the air flow,the blade angle,the number of blades,and the number of outlets of the gas distribution ring are selected as experimental factors.The combination of orthogonal experiment and Fluent numerical simulation is used to optimize the parameters and operating parameters of the aeration.Through the range analysis,the order of influence of various research factors on the mixing effect of the mixture is: blade angle>air flow >Number of blades> Number of outlets for the gas distribution ring.Through the excellent level analysis,the combination of the mixing parameters with the best mixing effect is obtained: the air flow is 414.5m3/h,the number of the gas distribution ring is 5,the blade angle is 15°,and the number of blades is 14.Based on the built-up combustion test bench,the experimental research on the metal fiber burner under the combination of the theoretical optimal aeration parameter combination and the non-theoretical optimal aeration parameter is carried out.The results show that the NOX amount emitted by combustion under the optimal aeration parameter combination is lower than that of other aeration parameters,and the temperature distribution is more uniform.Based on the correctness of the optimal combination of aeration parameters,further study the combustion experiments of metal fiber burners with heat loads of 50%,40%,30%,20%,and 10%,the experimental results show that the uniformity of the temperature distribution in the combustion chamber under different loads is not affected by the load change,but the average temperature in the combustion chamber decreases with the load,and its stability also decreases.The numerical simulation method is used to simulate the cold and hot state of the metal fiber burner in the combustion chamber under the optimal parameter combination,the results show that under cold conditions,the premixed gas flows out evenly on the fiber layer on the surface of the metal fiber burner,and the gas flow characteristics are good;Under hot conditions,when the 40% load premixed gas is burned at four flow rates of 0.5m/s,0.6m/s,0.7m/s,and 0.8m/s,the overall temperature field distribution in the combustion chamber is relatively uniform.There is no obvious difference in the temperature distribution trajectory,but the temperature on both the inner wall and the outlet of the combustion chamber is relatively high.The peak temperatures reached at the four flow rates are 1862 K,1837K,1824 K,1800K,respectively,and the temperature is higher,the NO molar concentration In a relatively high,low temperature region,the NO molar concentration is low. |
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