燃用生物柴油国Ⅴ公交车的颗粒排放与微观形貌

Emission Characteristics and Microscopic Morphology of Particles from China V Diesel Bus Fueled with Biodiesel Blends

摘要:

以一辆国Ⅴ柴油公交车为研究对象，试验研究了该车燃用不同比例废弃油脂制生物柴油?柴油混合燃料在中国典型城市公交循环（CCBC）下颗粒物质量、颗粒数量、粒径分布与颗粒微观形貌特征。结果表明：随着生物柴油比例的增加，排放的尾气颗粒物质量和固态颗粒数量减小；燃用生物柴油的尾气颗粒典型微观结构与柴油的类似，由多个准球状基本碳粒子堆积而成，呈链状、枝状等不规则结构；与燃用柴油的相比，燃用生物柴油的尾气颗粒基本碳粒子粒径较小，分形维数较大，空间结构更紧密；燃用生物柴油的尾气颗粒在团聚处更易被氧化， 颗粒的分形维数和基本碳粒子直径随着氧化进行而增大；燃用柴油的尾气颗粒的氧化主要以最外壳边界碳层湮灭为主，颗粒分形维数、基本碳粒子直径随着氧化进行而减小。

Abstract:

A diesel bus certified to meet China Ⅴ emission standards is selected as the research object to explore the mass， number， size distribution and microscopic morphology of particles by fueled with different used cooking oil （UCO） biodiesel blends during China typical city bus driving cycle （CCBC） experimentally. The results show that the mass and the number of particles emitted from the diesel bus decrease as the mixing ratio of the UCO biodiesel increases， and the typical microscopic morphology of particles by fueled with biodiesel blends is similar to that by fueled with diesel. The particles consist of dozens of quasi-spherical basic carbon particles， mainly in irregular shapes such as chain and branch. Moreover，the particles by fueled with biodiesel blends have smaller basic carbon particle size， larger fractal dimension and more compact spatial structure than those by fueled with diesel. In the process of oxidation， the particles by fueled with biodiesel blends are easier to be oxidated at agglomerating area， and the fractal dimension and the average size of basic carbon particles increase with the oxidation. However， the oxidation mainly occurs at the outermost carbon layer of the particles by fueled with diesel， and the fractal dimension and the average size of basic carbon particles decrease.