热辐射对富氧扩散燃烧火焰结构和氮氧化物生成的影响

The Impact of Thermal Radiation on the Flame Structure and the Formation of NO_x during an Oxygen enriched Diffusion Combustion Process

揭示了富氧燃烧过程中的火焰结构和氮氧化物生成机理,针对富氧火焰特性探讨NOx的抑制机理。本文以对向流扩散火焰为对象,利用基于详细的基元反应动力学模型的燃烧数值解析方法研究了热辐射对富氧空气(氧浓度为60%)/甲烷扩散火焰中火焰结构和氮氧化物生成的影响。结果表明,在速度梯度较大时,辐射对燃烧特性的影响可以忽视,当速度梯度κ减小到约20s-1以下,辐射的影响逐渐明显,需要考虑辐射项;同时发现随着速度梯度的减少,总的NO质量生成速率随着速度梯度的下降逐渐增大,在κ≈33.3s-1时达到峰值后又开始下降,直至熄火。

The flame structure and NOx generation mechanism during an oxygen-enriched combustion process are expounded. In connection with the oxygen-enriched flame characteristics an exploratory study was conducted of the mechanism of NOx suppression. With the counterflow diffusion flame serving as an object of investigation and by the use of a detailed elementary-reaction kinetics model-based numerical analysis method a study was conducted of the influence of thermal radiation on the flame structure and NOx formation in a methane/oxygen-enriched (oxygen concentration 60%) air diffusion flame. The results of the study indicate that when the velocity gradient is relatively great, the impact of radiation on the combustion characteristics can be neglected. However, when the velocity gradient is reduced to about less than 20 s-1 the influence of the radiation gradually becomes evident, thus necessitating the consideration of the radiation item. Meanwhile, it has been found that with a decrease in the velocity gradient the total NO mass generation rate will gradually increase with a reduction in the velocity gradient. The total NO mass generation rate will reach a peak value when the velocity gradient equals to about 33.3 s-1 and then begin to decrease until a flame extinction takes place.