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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。
The Rijke pulsation combustion test stand is used to compare and analyze the NOx formation characteristics of methane partial premixed flame at different equivalence ratios and flow velocities under the action of sound field by utilizing the flame direct image and NOx acquisition system. The results showed that the inflection point EI of NO emission index (EINO) appeared at 3.3 ~ 4 with the increase of equivalence ratio. When the equivalence ratio was less than EI, EINO increased first and then decreased with the increase of equivalence ratio; EI, EINO increases with the equivalence ratio. When the equivalence ratio is between 2 and 4, the effect of the mixed gas flow rate on EINO is small. When the equivalence ratio is larger than 4, the EINO increases with the increase of the flow rate. However, compared with the steady state combustion, The reason is that the increase of the flow velocity causes the length of the flame to increase, and the residence time of the fuel in the high temperature region becomes larger, whereas the effect of the pulsating sound field relative to the steady state flame shortens the length of the flame.