Sooting tendencies of diesel fuel component mixtures follow a linear mixing rule

With the growing importance of climate change, soot emissions from engines have been receiving increasing attention since black carbon is the second largest source of global warming. A sooting tendency can be used to quantify the extent of soot formation in a combustion device for a given fuel molecule, and therefore to quantify the soot reduction benefits of alternative fuels. However real fuels are complex mixtures of multiple components. In this work, we have used experimental methods to investigate how the sooting tendency of a blended fuel mixture is related to the sooting tendencies of the individual components. A test matrix was formulated that includes sixteen mixtures of six components that are representative of the main categories of hydrocarbons in diesel (eicosane (ECO) for alkanes, isocetane (ICE) for isoalkanes, butylcyclohexane (BCH) for cycloalkanes, 1-methylnaphthalene (1MN) for aromatics, tetralin for naphthoaromatics, and methyl-decanoate (MDC) for oxygenates). Most of the mixtures contain three to five components. The sooting tendency of each mixture was characterized by yield sooting index (YSI), which is based on the soot yield when a methane/air nonpremixed flame is doped with 1000 ppm of the test fuel. The YSIs were measured experimentally. The results show that the blending behavior is linear, i.e., the YSI of the mixtures is the mole-fraction-weighted average of the component YSIs. Experimental results have shown that the sooting tendency of a fuel mixture can be accurately estimated as the linear combination of the individual components. In addition, mass density of the mixtures is also measured, and a linear blending rule is applied to test whether mixing rules exist for mass density of diesel mixtures in this study. Results also have shown that the mixing rule tested in this study is valid and mass density of a mixture can be accurately estimated from the linear combination of the individual components.

随着气候变化的重要性日益凸显，由于黑碳是全球变暖的第二大来源，发动机的 soot排放受到了越来越多的关注。sooting倾向可用于量化给定燃料分子在燃烧装置中形成soot的程度，从而量化替代燃料减少soot的益处。然而，实际的燃料是多种成分的复杂混合物。在这项工作中，我们使用实验方法研究了混合燃料混合物的sooting倾向如何与各成分的sooting倾向相关。制定了一个测试矩阵，其中包括六种成分的十六种混合物，这些成分代表了柴油中碳氢化合物的主要类别（二十烷（ECO）代表烷烃，异十六烷（ICE）代表异烷烃，丁基环己烷（BCH）代表环烷烃，1 - 甲基萘（1MN）代表芳烃，四氢萘代表萘芳烃，甲基癸酸酯（MDC）代表含氧化合物）。大多数混合物包含三到五种成分。每种混合物的sooting倾向通过产率sooting指数（YSI）来表征，该指数基于在甲烷/空气非预混火焰中掺杂1000 ppm测试燃料时的soot产率。YSI是通过实验测量的。结果表明，混合行为是线性的，即混合物的YSI是各成分YSI的摩尔分数加权平均值。实验结果表明，燃料混合物的sooting倾向可以准确地估计为各成分的线性组合。此外，还测量了混合物的质量密度，并应用线性混合规则来测试本研究中柴油混合物的质量密度是否存在混合规则。结果还表明，本研究中测试的混合规则是有效的，混合物的质量密度可以从各成分的线性组合中准确估计。