不同压力下对冲扩散火焰燃料型NO生成特性

Fuel NO Formations in Counterflow Diffusion Flames at Different Pressures

采用NH3模拟燃料氮,数值预测了Ar稀释的CH_4/空气对冲扩散火焰在不同压力下NO的生成,并讨论了燃料型NO生成量的影响因素。结果表明:随着燃料氮含量的增加,燃料型NO反应路径逐渐成为NO生成的主要路径。其生成量随着压力的增加而减少。燃料中CH_4含量和气流出口速度对燃料型NO均有一定影响。CH基团同时参与NO的生成与还原反应,在本文工况下对NO还原反应影响更大,随着燃料中CH_4含量的增加,NO峰值会略有减小。气体出口速度增加,高温区变小,反应物在高温区的停留时间变短,对NO还原反应影响强于NO生成反应,因此随着出口速度增加,NO峰值略有增加。

Fuel NO formations in counterflowing diluted NH3-doped CH4/Air diffusion flames at different pressures were numerically studied. Factors affecting fuel NO formations were also discussed. NH3 was added in the fuel stream as fuel nitrogen and fuel stream was diluted by Ar. Results show that fuel NO reaction path gradually becomes the dominating path in NO formation with the increasing NH3 content in the fuel stream. Fuel NO decreases as pressure increases. Both CH4 content in fuel stream and gas exit velocity have certain influence on fuel NO formation. CH radical is involved in several NO formation reactions and NO reduction reactions. It has a larger effect in NO reduction reactions under the conditions in this article, so maximum NO concentration in the flame decreases slightly with the increasing CH4 fraction in the fuel stream. Increasing gas exit velocity narrows high temperature zone and reduces the residence time of the reactants in the high temperature zone. It has a larger influence on NO reduction reactions than NO for- mation reactions. The maximum NO concentration thus increases slightly as gas exit velocity increases.