火焰中多环芳烃（PAHs）的生成和演变机理

Soot formed in incomplete combustion of hydrocarbons is an important inducement in the formation of PM2.5. Polycyclic aromatic hydrocarbons (PAHs) are generally accepted as the precursors to soot particles in flame, and the character of PAHs has great impact on the formation of soot. ABF model developed on the basis of hydrogen-abstraction-carbon-addition (HACA) mechanism is still popular in use for premixed flames. But the predicted concentration of soot is not accurate enough. The object of this program is to provide an improved chemical mechanism of PAH growth and oxidation using accurate ab initio density functional theory calculations, as well as TST (transition state theory ) theory and RRKM (Rice-Ramsperger-Kassel-Marcus) theory. At the same time, the concentration of various PAHs will be experimentally measured via PLIF technology. Both theoretical an experimental researches contribute to developing an improved and accurate PAHs chemical kinetics model. The improved model can provide theoretical basis for the accurate prediction of soot formation.

化石燃料燃烧排放的soot是大气PM2.5形成的重要因素之一。在火焰中，多环芳烃（PAHs）是soot的前体物，其生成特性对soot的形成有重要影响。当前基于HACA机理的PAHs化学动力学模型（ABF模型）还不完善，导致应用该模型计算和预测soot生成不够准确。本项目采用量子化学从头算法、过渡态理论、单分子反应理论对碳氢燃料的PAHs生成、长大、氧化过程进行系统研究，并采用PLIF技术对预混火焰中PAHs进行在线测量，通过理论和实验研究发展更完善PAHs化学动力学模型，为准确预测发动机燃烧soot生成提供理论基础。

本项目针对碳烟（soot）生成前体物多环芳烃（PAHs）的生成和演变机理进行了理论计算和实验研究。理论计算方面，使用量子化学密度泛函理论（DFT）和反应势能面分析，探索了碳氢燃料火焰中多环芳烃（PAHs）生成与氧化的新路径，对现有的PAHs反应机理进行了完善，构建了新的PAHs机理模型，对气相分子和PAHs的浓度预测精度较已有模型有改善明显。实验研究方面，搭建了激光诱导荧光（LIF）实验系统，对层流预混火焰中PAHs的相对浓度进行在线测量，并结合DFT、含时密度泛函理论与Franck − Condon理论计算了各气相PAHs的荧光光谱，提高了LIF技术测量PAHs的选择性。最后，结合实验数据对所构建的PAHs机理进行验证和完善，得到更完善 PAHs 化学动力学模型，为准确预测发动机燃烧 soot 生成提供理论基础。