摘要
以柴油-甲醇燃料为研究对象，探究柴油-甲醇混合燃料燃烧对多环芳香烃（PAHs）生成的影响规律。将AVL-Fire和Chemkin耦合，构建正庚烷-甲苯-PAHs化学反应动力学机理并验证，采用Chemkin中的均质零维反应模型进行仿真模拟，研究了柴油甲醇混合燃料不同掺混比、初始温度、初始压力、当量比对多环芳香烃苯、萘、菲、芘（A1~A4）的影响。结果表明：随着甲醇掺混比从0%增加到20%，A1~A4的摩尔分数峰值降幅分别为5.4%，14.6%，21.5%，28.1%，总生成率的谷值升高率分别为0.86%，18.91%，20.84%，23.54%，说明PAHs的苯环数越多，受甲醇的抑制作用相对越明显；从反应路径中可以看出，甲醇在燃烧中分解形成H2、OH、H等，更多地加入到消耗PAHs的反应路径中，尤其是苯环数较多的PAHs；随着初始温度从1 000 K增加到1 200 K，缸内温度急剧升高的时刻提前，A1~A4摩尔分数峰值分别上升了0.67×10-5，2.43×10-10，5.23×10-14，0.93×10-14，说明初始温度增加有利于加速PAHs的生成；随着初始压力从0.1 MPa增加到1 MPa，A1~A4的峰值到达时刻均有所提前，大约提前了27 ms，提前幅度为93%，甲醇分子裂解形成的自由基与PAHs前驱体反应更加剧烈，有利于促进PAHs的生成；当量比从0.5增加到1.5，A1~A4的摩尔分数峰值升高率分别为1 486%，1 194 900%，79 249 900%，29 269 900%，当量比的增加导致燃烧局部缺氧，显著地促进了PAHs的形成。
Abstract
Taking the diesel-methanol blended fuel as the research object，the influence of diesel-methanol blended fuel combustion on the formation of polycyclic aromatic hydrocarbons (PAHs) was studied. The kinetic mechanism of nheptane/toluenePAHs chemical reaction was constructed and verified by coupling AVLFire and Chemkin, the simulation was conducted by using the homogeneous zerodimensional reaction model of Chemkin, and the influences of mixing ratio, initial temperature, initial pressure and equivalent ratio on PAHs such as benzene, naphthalene, phenanthrene and pyrene (A1-A4) were analyzed.The results show that the peak drop of A1-A4 mole fraction are 5.4%, 14.6%, 21.5%, and 28.1% respectively and the valley increase of total yield are 0.86%, 18.91%, 20.84%, and 23.54% respectively when the methanol blending ratio increases from 0 to 20%. Accordingly, methanol has the more obvious inhibitory effect on PAHs with the more number of benzene rings. According to the reaction path, methanol decomposes into H2, OH, H and so on during the combustion, which enter the reaction path that consumes PAHs, especially PAHs with more benzene rings. As the initial temperature increases from 1 000 K to 1 200 K, the sharp rise time of incylinder temperature advances, the peak values of A1-A4 mole fraction increase by 0.67×10-5, 2.43×10-10, 5.23×10-14, and 0.93×10-14 respectively, hence the increase of initial temperature is beneficial to accelerate the generation of PAHs. The initial pressure increases from 0.1 MPa to 10 MPa, then all the peak arrival times of A1-A4 advance. The advancement is about 27 ms, which is equivalent to 93%. The free radicals of methanol molecular decomposition have a violent reaction with PAHs precursor, which is beneficial to promote the generation of PAHs. Besides, the peak values of A1-A4 mole fraction increase by 1 486%, 1 194 900%, 79 249 900%, and 29 269 900% respectively when the equivalence ratio increases from 0.5 to 1.5. The increase of equivalence ratio causes local hypoxia so as to promote the formation of PAHs.
关键词
甲苯 /
正庚烷 /
甲醇 /
多环芳香烃 /
化学反应动力学
钱怡凯，王忠，李瑞娜，刘帅，李立琳.
柴油-甲醇混合燃料多环芳香烃形成的影响因素研究[J]. 车用发动机. 2022, 0(1): 31-39
QIAN Yikai,WANG Zhong,LI Ruina,LIU Shuai,LI Lilin.
Factors Influencing Formation of Polycyclic Aromatic Hydrocarbons for Diesel-Methanol Blended Fuel[J]. Vehicle Engine. 2022, 0(1): 31-39
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