最新的实验研究发现，目前广泛应用的甲苯-正庚烷柴油替代燃料的碳烟排放特征与实际柴油的碳烟排放特征有较大差异，而丁基苯-正庚烷柴油替代燃料更加接近实际柴油。这表明单烃基苯结构（支链长度）对柴油替代燃料燃烧产物PAH（碳烟前驱物）有重要影响。本项目拟采用实验、理论计算和数值模拟相结合的方法，从微观到宏观，系统全面地研究单烃基苯支链长度对柴油替代燃料燃烧产物PAH的影响。研究内容包括单烃基苯/柴油替代燃料基础燃烧实验及PAH反应路径的量化计算、柴油替代燃料燃烧机理模型构建及PAH反应动力学研究、发动机复杂条件下柴油替代燃料燃烧产物PAH的实验和模拟研究。通过研究，揭示不同支链长度单烃基苯-正庚烷柴油替代燃料燃烧产物PAH的反应机理，阐明缸内多场耦合条件下不同链长的单烃基苯对柴油替代燃料燃烧产物PAH的贡献和影响机制。研究成果将进一步完善柴油机碳烟生成机理，为降低柴油机颗粒物排放提供理论依据。

The latest experimental research shows that the soot emissions characteristics of toluene-n-heptane model which widely used in diesel surrogate fuels are quite different from those of actual diesel. While the n-butylbenzene-n-heptane diesel surrogate fuel is closer to actual diesel. This indicates that the alkylbenzene structure (side-chain length) has an important influence on the combustion product PAH (a soot precursor) of diesel surrogate fuel. This project intends to use the combination of experimental, theoretical calculation and numerical simulation to systematically study the effect of alkylbenzene side-chain on combustion products PAH of diesel surrogate fuels from micro to macro. The research includes the basic combustion experiment of single alkylbenzene/diesel surrogate fuel and the quantitative calculation of PAH reaction path, the construction of diesel surrogate fuel combustion mechanism model and PAH reaction kinetics, and the experimental and simulation study of diesel surrogate fuel combustion product PAH under complex engine conditions. Through the research, the reaction mechanism of combustion products PAH of different side-chain alkylbenzene-n-heptane diesel fuel surrogate will be revealed. In addition, the contribution and the influence mechanism of alkylbenzenes with different side-chain lengths to the combustion products PAH of diesel surrogate fuel under multi-field coupling conditions will be clarified. The research results will further improve the soot generation mechanism and provide a theoretical basis for reducing particulate matter emissions of diesel engines.