稀释气/天然气燃烧及NO_x排放特性

The reaction mechanism of the NO_x emission and combustion characteristics of the natural gas with diluents

以甲烷/空气/稀释气预混火焰为研究对象,研究了CO_2和N_2这两种稀释气对天然气燃烧NO_x排放的影响;借助反应路径分析方法,揭示了CO_2的化学效应和热效应对NO生成的影响机制。研究结果表明:1)CO_2降低NO_x排放的效果比N_2更显著,其化学效应主要是通过在火焰面区内消耗大量CH_2(s),降低了区内CH的浓度,从而减少NO的生成。2)热效应的减排作用比化学效应更大,通过降低绝热燃烧温度实现。3)稀释气会轻微增大混合物着火延迟时间和大幅度降低层流火焰速度,表明引入稀释气降低污染物排放的同时还存在明显抑制燃烧反应进行的作用。

The effect of different diluents on the NO x emission of the combustion of natural gas with CO2 and N2 was studied with premixed methane/air/diluent flame.The chemical effect and thermal effect of CO2 on the NO production was revealed via conducting reaction-path analysis.The numerical results show that:1)CO2 is more effective than NO in emission reduction.The chemical effect is achieved by consuming larger part of CH2(s)in the flame zone,leading to smaller NO production subsequent to lower CH concentration;2)compared to the chemical effect,the thermal one plays a more important role in NO emission by reducing the adiabatic flame temperature of the mixture;3)the introduced diluents enlarge the ignition delay time slightly and greatly reduce the laminar flame speed of the mixture,indicating that low NOx emission characteristic of diluents accompanies with significant inhibiting effect on the combustion of the mixture.