The influence of a large methyl ester on in-flame soot particle structures in a small-bore diesel engine
The influence of a large methyl ester on in-flame soot particle structures in a small-bore diesel engine
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DOI：
10.1016/j.fuel.2017.01.044
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发表时间：
2017-04
期刊：
影响因子：
7.4
通讯作者：
Yilong Zhang;Renlin Zhang;L. Rao;Dongchan Kim;S. Kook
中科院分区：
文献类型：
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作者：
Yilong Zhang;Renlin Zhang;L. Rao;Dongchan Kim;S. Kook
与传统柴油相比，含氧生物柴油具有更低的烟尘倾向，为解决高颗粒物排放问题提供了良好的机会。本研究报告了癸酸甲酯的烟灰形态细节，癸酸甲酯是生物柴油中较大脂肪酸甲酯的替代燃料。并与传统柴油进行了比较，讨论了烟尘初生颗粒和团聚体的大小分布以及团聚体的分形维数。此外，还分析了碳条纹长度、弯曲度和条纹间分离距离等纳米尺度烟尘参数，以阐明不同燃料类型下碳条纹内部结构的变化。特别令人感兴趣的是运行中的柴油机火焰中烟灰颗粒的结构。与以往大量报道生物柴油尾气烟尘颗粒结构的研究相比，本研究提供了关于主燃烧过程中高形成和氧化过程中烟尘颗粒的额外和补充信息。在一个小口径光学柴油发动机中，利用放置在燃烧室内的采样探针，将透射电子显微镜（TEM）栅格直接暴露于煤烟火焰中，进行了基于热反射电阻的煤烟颗粒收集。对TEM图像进行后处理，对上述形貌和纳米结构参数进行统计分析。结果表明，癸酸甲酯生成的煤烟初级颗粒较小，聚体分形维数较低，这可能与煤烟形成阶段较早或煤烟氧化程度较高有关。从条纹分离结果显示癸酸甲酯的间隙较小，可以得出结论，由于燃料中氧化剂的存在，采样的火焰中烟灰颗粒更容易被氧化。
Oxygenated biodiesel presents lower sooting propensity than conventional diesel, providing a good opportunity to resolve the high particulate emissions issue. This study reports soot morphology details of methyl decanoate, a selected surrogate fuel for the larger fatty acid methyl esters in biodiesel. The size distribution of soot primary particles and aggregates as well as the fractal dimension of the aggregates are discussed in comparison to those of a conventional diesel fuel. In addition, nanoscale soot parameters such as carbon fringe length, tortuosity, and fringe-to-fringe separation distance are analysed to clarify the internal structure variations depending on the fuel type. Of particular interest are the structures of soot particles within the flame in a running diesel engine. Compared with numerous previous studies reporting exhaust soot particle structures of biodiesel, the present study provides additional and complementary information about soot particles under high formation and oxidation processes during the main combustion event. Thermophoresis-based soot particles collection was conducted in a small-bore optical diesel engine using a sampling probe placed within the combustion chamber for the direct exposure of a transmission electron microscope (TEM) grid to sooting flames. The TEM images were post-processed for statistical analysis of the aforementioned morphology and nanostructure parameters. The results show that methyl decanoate generates smaller soot primary particles and aggregates with lower fractal dimension, which could be explained either by the earlier stage of soot formation or more oxidised soot status. From the fringe separation results showing a smaller gap for methyl decanoate, it is concluded that the sampled in-flame soot particles were more oxidised likely due to the presence of oxidisers in fuel.