基于对冲火焰的碳氢燃料碳烟生成倾向的量化指标及机理研究

The formation of soot during hydrocarbon fuel combustion is a highly complex phenomenon involving various interrelated physicochemical processes. Among these factors influencing soot formation, fuel type, (i.e. its molecular structure) is of particular significance considering that practical fuels are typically composed of many different chemical components, each of which may have different sooting characteristics. Through laser-based measurements, the current project aims to systematically evaluate the sooting tendencies of various C5-C8 hydrocarbons in counterflow diffusion flames including n-alkanes, branched-alkanes, cycloalkanes, alkenes, dienes, aromatics and their derivatives. A sooting index based on counterflow diffusion flame will be proposed to quantify the sooting tendencies of hydrocarbon fuels and the effects of different functional group will be investigated. Further work will focus on the effect of fuel mixing on soot formation and their dependence on fuel type. Quantified mixing rule will be proposed. Detailed kinetic mechanism with PAH growth for representative fuels will be developed and used together with a soot model to simulate soot formation in CDF. Subsequent analysis of the simulation results, through sensitivity and ROP analysis, aims to uncover the underlying mechanism for the experimentally observed difference in sooting tendency for different fuels, with a focus on the effect of functional group. The findings of the proposed project will provide theoretical and practical guidance on reducing the sooting tendencies of realistic fuels through component optimization and fuel additives development.

石化燃料燃烧过程中的碳烟生成是一个复杂现象，涉及众多相互联系的理化过程。在影响碳烟生成的各种因素中，燃料种类的影响尤为重要。这是因为实际燃料通常由多种组分组成，而每种组分又具有不同的碳烟生成倾向。项目拟通过基于激光诊断的测量技术，系统地研究对冲火焰中C5-C8燃料(直/支链烷烃，烯/二烯烃，环烷烃和芳香烃等)的碳烟生成倾向。提出基于对冲火焰的碳烟生成倾向的量化指标，并据此分析典型化学官能团与碳烟生成的量化关系。进一步研究不同种类燃料掺混的影响，提出定量混合规律。项目还将针对具有典型官能团的燃料开发包含PAH生成的详细化学机理，结合碳烟模型进行对冲火焰碳烟生成的模拟计算。通过对模拟结果进行敏感性和反应路径分析，找出与燃料种类相关并对碳烟生成有重要影响的中间产物及反应步骤，揭示燃料结构影响碳烟生成的内在机理。所得结果对优化燃料组成、开发添加剂以降低实际燃料的碳烟生成倾向有重要的理论和现实意义。

碳烟生成涉及众多相互联系的理化过程。在影响碳烟生成的各种因素中，燃料结构的影响尤为重要。这是因为实际燃料通常由多种组分组成，而每种组分又具有不同的碳烟生成倾向。本项目采用对冲火焰的碳烟生成研究平台，研究了燃料结构对碳烟生成倾向的影响规律和化学机理。项目首先搭建了对冲火焰的碳烟光学诊断平台（包括激光消光法和激光诱导炽光），构建了分区碳烟动力学模型，分析了典型对冲火焰的热化学结构和碳烟生成区域结构。在此基础上，研究了C2-C8 1-烯烃燃料的碳烟生成倾向，提出了基于碳烟体积分数的碳烟生成倾向量化指标，并构建了描述C2-C8 1-烯烃燃料PAH生长的详细气相反应机理，分析了燃料具有不同碳烟生成倾向的动力学机理；测量了若干C6碳氢燃料的碳烟生成倾向，研究化学官能团结构（如支链的位置、双键、环状结构及环状结构上的支链等因素）对碳烟生成倾向的影响规律，提出了基于对冲火焰碳烟生成临界火焰温度的量化指标。最后，研究了氢气及醇类燃料分别掺混对碳氢燃料碳烟生成倾向的影响规律和动力学机制，揭示了氢气（醇类燃料）在碳氢燃料碳烟生成过程的化学作用。本研究工作为优化燃料组成、开发添加剂以降低实际燃料的碳烟生成倾向有重要的理论和现实意义，为实现氢气（或醇类燃料）与化石燃料掺混的高效清洁燃烧提供理论参考。