关键词: 尾气颗粒物；燃油硫含量；微观形貌；纳观结构；理化特征

Abstract: The effect of sulfur content in diesel fuel on the morphology, nanostructure, particle size, graphitization degree, surface functional groups and composition of exhaust particles is investigated on a 4.5 L marine auxiliary diesel engine by using three kinds of diesel fuels, which have different sulfur contents. The morphology and nanostructure of exhaust particles are analyzed using transmission electron microscopy (TEM). The graphitization degree of exhaust particles is analyzed by Raman spectrometer. The surface functional groups of exhaust particles are analyzed employing Fourier transform infrared spectrometer. The composition and elemental composition of exhaust particles are analyzed by thermal gravimetric analyzer and plasma emission spectrometer, respectively. Based on the low-powered electron microscopy images, it is found that the exhaust particles is an irregular aggregate structure, which is composed of dozens or even hundreds of spherical or nearly spherical primary particles, and with the increase of fuel sulfur content, the stacking of primary particles becomes more obvious, and the microscopic morphology of exhaust particles changes from chain structure to a more complex agglomerate. Based on high-powered electron microscopy images, it is found that the primary particles perform a typical core-shell structure, and with the increase of fuel sulfur content, the thickness of the amorphous substance at the outer edge of the primary particles and the particle size of the primary particles also increase. Furthermore, with the increase in fuel sulfur content, the research reveals the following findings: in terms of morphology, the average curvature of primary particle crystals increases while the average length decreases; in terms of graphitization, the degree of particle graphitization declines; in terms of composition, the proportion of organic components and S sulfur elements increases.

Key words: Exhaust particulates; Fuel oil sulfur content; Microscopic morphology; Nanoscale structure; Physicochemical characteristics