The present work focused on the combustion chemistry in sooting transition process in iso-octane counterflow diffusion flames. A series of iso-octane flames ranging from sooting-free to heavy-sooting were investigated by stepwise increasing the oxygen concentration (X_O) in the oxidizer stream. In particular an optical approach with two different algorithms based on the three wavelengths distribution of flame images captured by digital single lens reflex (DSLR) camera was proposed to identify the critical condition for the sooting transition process. The results showed that the sharp increase in signal ratio of red luminosity with simultaneously obvious decrease in signal rations of blue luminosity could be used as an effective indicator of sooting onset in flames. On-line gas chromatography (GC) measurements were used to investigate the flame chemistry and determine quantitative mole fraction profiles of stable and reactive species formed in the combustion process. Particular attention was given to the combustion chemistry changes caused by the occurrence of sooting transition. Numerical kinetic simulations were performed along with the comparisons with experimental results to obtain deep insights into the sooting transition process, with focus on benzene chemistry considering the critical role of benzene formation in the subsequent large aromatic species/soot formation process. In most cases, the trend observed in the experiments could be satisfactorily reproduced and explained by the models. For major species and C1–C4 species, it can be seen that the concentration increased with the increase of X_O in sooting transition process. For the decomposition of fuel and the formation of benzene, the influence in sooting transition process was mainly reflected in the contributions of different pathways due to temperature effects. The impact of sooting transition on flame chemical structure was mainly reflected in the growth of PAHs. The increasing trend for the PAHs growth caused by the increase of oxygen concentration in the transition process was more and more obvious.

目前的工作重点是异辛烷逆流扩散火焰中烟尘转变过程中的燃烧化学。一系列的异-辛烷的火焰从免费烟熏到重积炭通过逐步增加研究的氧浓度（X _Ò) 在氧化剂流中。特别是提出了一种基于数字单镜头反光 (DSLR) 相机捕获的火焰图像的三个波长分布的两种不同算法的光学方法，以确定烟尘过渡过程的临界条件。结果表明，红色光度信号比急剧增加，同时蓝色光度信号比明显下降，可作为火焰中烟灰发生的有效指标。在线气相色谱 (GC) 测量用于研究火焰化学并确定燃烧过程中形成的稳定和反应性物种的定量摩尔分数分布。特别关注由碳烟转变的发生引起的燃烧化学变化。进行了数值动力学模拟以及与实验结果的比较，以获得对烟尘转变过程的深入了解，重点是苯化学，考虑到苯形成在随后的大芳香族物质/烟尘形成过程中的关键作用。在大多数情况下，模型可以令人满意地再现和解释实验中观察到的趋势。对于主要物种和 C1-C4 物种，可以看出，浓度随着浓度的增加而增加。实验中观察到的趋势可以通过模型令人满意地再现和解释。对于主要物种和 C1-C4 物种，可以看出，浓度随着浓度的增加而增加。实验中观察到的趋势可以通过模型令人满意地再现和解释。对于主要物种和 C1-C4 物种，可以看出，浓度随着浓度的增加而增加。X _O在烟灰过渡过程中。对于燃料的分解和苯的形成，烟尘转变过程的影响主要体现在温度效应下不同途径的贡献。烟尘转变对火焰化学结构的影响主要体现在 PAHs 的生长上。过渡过程中氧浓度增加引起的PAHs生长增加的趋势越来越明显。