声场作用下甲烷部分预混火焰不同当量比和流速对NO_x生成的影响

Effects of Equivalence Ratio and Velocity on NO_x Emissions in Methane Partially Premixed Flames With Acoustic Excitation

采用Rijke型脉动燃烧试验台,利用火焰直拍图像、NOx采集系统,对声场作用下甲烷部分预混火焰在不同当量比和流速下的NOx生成特性进行了比较和分析。结果表明,随着当量比的增大,在3.3-4处NO排放因子（NOemissionindex,EINO）出现拐点EI,当量比小于EI时,EINO随当量比的增大而先增后减;当量比大于EI时,EINO随当量比的增大而增大。当量比在2-4时,混合气流速对EINO的影响较小;当量比大于4时,EINO随着流速的增加而增加,但相对于稳态燃烧,EINO随流速增加的速率明显减小,原因在于,流速的增大致使火焰长度增加,燃料在高温区域停留时间变大,而相对于稳态火焰,脉动声场的作用使火焰长度变短。

Experimental tests on the characteristics of NOx emission for partially premixed methane combustion were carried out in a Rijke pulsating combustor under varying conditions of equivalence ratio and velocity with flame direct image and NOx acquisition system,and the test results were compared and analyzed.Along with the change of the equivalence ratio,the results show a inflection point of the NO emission index（EINO） profile appears in quivalence ratio ？？EI is range from 3.3 to 4.When equivalent ratio is less than EI,EINO will be first increased and then decreased with the increase of the equivalence ratio.However,when equivalent ratio is larger than EI,EINO will be increased with the increase of the equivalence ratio.When the equivalent ratio is range from 2 to 4,EINO will be changeless with the increase of the velocity,but in the range from 4 to ∞,the EINO be increased with the increase of the velocity.Nonetheless,the increasing rate of EINO decreased evidently in pulse combustion with increase of flow velocity compared with the steady combustion.The reason is the flame length increased with increase of flow velocity,the global residence time of fuel in the high temperature area is increased.And compare with the steady flame,pulsating sound field make flame length shorter.