Sooting Propensities of FACE Gasolines in Counterflow Nonpremixed Flames

To combat the negative health and environmental effects that accompany the continued consumption of hydrocarbon fuels, progress is being made to better facilitate clean combustion. Reducing the formation of particulate soot during practical combustion phenomena, e.g., within internal combustion engines, remains a critical challenge. The focus of this study is to provide a detailed characterization of the sooting propensities of three research-grade gasolines, namely FACE (Fuels for Advanced Combustion Engines) F, G, and J, developed by Chevron Phillips Chemical Company. Specifically, laser-induced incandescence (LII) is used to measure spatially resolved soot volume fraction profiles at varying strain rates and reactant concentrations in counterflow nonpremixed flames. LII results are accompanied by planar laser-induced fluorescence (PLIF) measurements of OH radicals for identifying flame sheet locations. In addition, particle image velocimetry (PIV) is used to characterize flow fields. The combination of LII, OH-PLIF, and PIV data sets results in a comprehensive description of soot formation in counterflow flames, which can be used to validate soot models for the combustion of gasoline fuels and to improve upon the fuel property database of FACE gasolines so that the sooting propensities of surrogate fuels can be quantitatively compared to those of their target real fuels. Experimental results show that the soot yield of FACE F is significantly less than those of FACE G and J, while the soot yield disparity between FACE G and J, which have similar aromatic content by volume, can be attributed to differing volumetric percentages of large (≥C9) single-ringed aromatic species.

为应对持续消耗烃类燃料所带来的健康与环境负面影响，当前学界正积极推进相关研究以更好地实现清洁燃烧。在实际燃烧场景（例如内燃机内部）中，抑制颗粒炭烟的生成仍是一项关键挑战。本研究的核心目标是详细表征三款由雪佛龙菲利普斯化学公司（Chevron Phillips Chemical Company）开发的研究级汽油的发烟倾向，即FACE（先进燃烧发动机燃料，Fuels for Advanced Combustion Engines）F、G与J型燃料。具体而言，本研究采用激光诱导炽光法（laser-induced incandescence, LII），在逆流非预混火焰中，于不同应变率与反应物浓度条件下，测量空间分辨的炭烟体积分数分布。激光诱导炽光法的测量结果，辅以羟基自由基的平面激光诱导荧光（planar laser-induced fluorescence, PLIF）测量，以确定火焰面的位置。此外，本研究还采用粒子图像测速法（particle image velocimetry, PIV）对流场进行表征。将激光诱导炽光法、羟基-平面激光诱导荧光与粒子图像测速的数据集相结合，可全面描述逆流火焰中的炭烟生成过程，该数据集可用于验证汽油燃料燃烧的炭烟模型，并完善FACE汽油的燃料属性数据库，从而能够定量对比替代燃料与对应实际燃料的发烟倾向。实验结果表明，FACE F型燃料的炭烟产率显著低于FACE G与J型；而体积芳香烃含量相似的FACE G与J型，其炭烟产率差异可归因于二者中大型单环芳烃（≥C9）的体积占比不同。