基于反扩散燃烧的CH_(4)燃烧特性及NO_(x)排放的数值研究

Numerical study on CH_(4)combustion characteristics and NO_(x)emission based on anti-diffusion combustion

反扩散燃烧具有火焰温度均匀、污染物排放低的特点。针对基于反扩散燃烧的天然气低氮氧化物(NO_(x))燃烧器,文章利用CFD软件对燃烧器反扩散燃烧的燃烧特性进行数值研究,分析分级燃烧过程及热力型和快速型NO_(x)的生成特点,提出“气包风”的反扩散燃烧组织思想;研究不同过量空气系数、烟气再循环率对流场分布、温度场分布、NO_(x)排放特性的影响。研究结果表明:随着过量空气系数增大,火焰长度变短,燃烧速率变快,燃烧状况得到改善,NO_(x)排放呈现先增加后减少的变化趋势;随着烟气再循环率的增加,炉膛内火焰平均温度与出口处NO_(x)排放均呈下降趋势,当烟气再循环率为0.20时,出口处NO_(x)排放降低约95%,实现超低排放。该研究对反扩散火焰在工业生产中的应用具有一定的指导意义。

Anti-diffusion combustion has the characteristics of uniform flame temperature and low pollutant emission.Aiming at the natural gas low NO_(x)burner based on anti-diffusion combustion,the combustion characteristics of anti-diffusion combustion of the burner are numerically studied by CFD software,the staged combustion process and the generation characteristics of thermal and rapid NO_(x)are analyzed,and the anti-diffusion combustion organization idea of“air bag wind”is put forward.The effects of different excess air coefficient and flue gas recirculation rate on flow field distribution,temperature field distribution and NO_(x)emission characteristics are studied.The results show that with the increase of excess air coefficient,the flame length becomes shorter,the combustion rate becomes faster,the combustion condition is improved,and the NO_(x)emission increases first and then decreases.With the increase of the flue gas recirculation rate,the average flame temperature in the furnace and the NO_(x)emission at the outlet both show a downward trend.When the flue gas recirculation rate is 0.20,the NO_(x)emission at the outlet decreases by about 95%,achieving ultra-low emission,which has guiding significance for the application of anti-diffusion flame in industrial production.