甲烷/高温烟气稀释空气的Mild燃烧过程的数值研究

中低氧浓度稀释MILD燃烧与传统有焰燃烧方式相比,燃烧室内温度相对均匀,可以有效控制和降低NO_X等污染物排放。燃烧室内的烟气循环导致的混合气稀释程度、预热温度以及流场应变率对Mild燃烧过程有重要影响。通过对不同稀释和预热程度的一维层流对撞扩散火焰进行计算,研究了烟气回流稀释/预热形成的Mild燃烧情况。数值计算结果表明,Mild燃烧能很好的控制燃烧场的最高温度和反应放热速率,得到较为均匀的温度场,并因此降低产物中污染物的浓度。对不同预热温度、不同拉伸率下工况的计算证明了Mild燃烧能够扩展燃料的燃烧极限,Mild燃烧对流场等外部干扰的敏感度较小,燃烧稳定。

Numerical Study of Mild Combustion Process of CH4 and Hot Gas Diluted Air

Compared with traditional flame combustion, the Moderate ＆ Intense Low Oxygen Dilution （MILD） combustion could provide relative uniform temperature field, as well as effectively controlling and reducing the discharge of pollutants like NOx. The dilution level, preheating temperature and the strain rate of the flow field caused by the gas recirculation in the combustion chamber, have great influence on Mild combustion process. The Mild combustion formed though gas recirculation has been studied by opposed jets of hot/diluent air mixture versus cold fuel under different dilution and preheating levels. The computational results indicate that Mild combustion process could satisfactorily control the highest temperature and heat release rate profile in the combustion field, which could be a more uniform one, and as the result, significantly reduce the concentration of pollutants. The characteristics of Mild combustion including lower sensitivity to external perturbation and stable combustion are proved by simulations under different preheating temperatures and stain rates.