乙烯-正庚烷混合燃料在碳烟生成中的协同效应

Synergistic Effect of Ethylene-Heptane Mixture on Soot Formation

在对冲扩散火焰中对乙烯-正庚烷混合燃料的燃烧进行了模拟研究.耦合的反应机理包含正庚烷的裂解、C0-C4核心小分子反应、初始苯环生成、拓展到六苯并苯(A7)的PAH化学和包含36步成核反应的碳烟表面机理.在预混火焰中对正庚烷的燃烧进行了模拟,得到的关键组分的浓度变化与文献中的试验数据吻合较好.在对冲扩散火焰中对乙烯-正庚烷掺混燃料的燃烧进行模拟,结果显示:随着正庚烷掺混比的增加,碳烟体积分数(SVF)、苯及PAH的峰值均呈现先增加后降低的趋势,当掺混比为5%,时,SVF的峰值达到最大.对苯的生成进行详细分析,发现丙基和甲基在这种协同效应中起着关键作用.此外,随着掺混比的增加,苯与PAH的反应生成区逐渐往氧化剂侧移动,越过滞止平面后苯的生成率和消耗率均大大降低.

Combustion process of ethylene-heptane mixture was calculated in an opposed-flow diffusion flame.The coupled mechanism contains the pyrolysis reactions of heptane,core reactions of C0-C4,the formation of benzene,PAH growth up to coronene（A7）,and soot surface growth which includes 36 nucleation reactions.Combustion of heptane was simulated in a premixed flame.Results show that concentrations of key components agree well with the experimental data in the literature.Combustion of ethylene-heptane mixture was simulated in an opposed-flow diffusion flame.Results show that,with the increase of heptane ratio,the soot volume fraction（SVF）,concentration of benzene and maximum points of PAH show first increase and then decrease.Maximum peak of SVF is reached as 5%,heptane is added to the fuel.Propyl and methyl groups play an important role in the synergistic effect of the formation of benzene.In addition,with the increase of heptane ratio,the formation regions of benzene and PAH move towards the oxidizer nozzle.The formation and consumption rate both decrease as the reaction region gets across the stagnation plane.