柴油机排气颗粒的力学特征与形貌分析  

Analysis on the morphology and mechanical characteristics of agglomerated particles emitted from the diesel exhaust process

作　　者：赵怀北[1] 王忠[1] 刘帅[1] 李瑞娜[1] 冯渊[2] 

机构地区：[1]江苏大学汽车与交通工程学院,镇江212013 [2]无锡职业技术学院汽车与交通学院,无锡214121

出　　处：《科学通报》2017年第30期3498-3505,共8页Chinese Science Bulletin

基　　金：国家自然科学基金(51376083);江苏省高校自然科学研究面上项目(15KJB470001)资助

摘　　要：采用Hamaker等理论模型计算分析了理想状态下颗粒-颗粒间的作用力;采用原子力显微镜以及透射电子显微镜试验的方法,考察了干燥环境下(相对湿度RH≤20%)排气颗粒间总的吸引力、黏附力以及黏附能,探究了排气颗粒粒径对粒子间作用力及颗粒形貌的影响关系.结果表明:颗粒粒径由25 nm增加到45 nm过程中,单颗粒之间的范德华力增加4.6倍,静电力增大9.9倍,相比范德华力,静电力较小.颗粒间黏附力与黏附能均增加了1.8倍.通过AFM试验,对平均粒径分别为30,37,46 nm的团簇颗粒进行测量,发现随着粒径增大,颗粒间总的吸引力F_(at)逐渐增大,为1.04~1.38 n N,范德华力F_(vdw)是F_(at)中的主要作用力,库仑力较小.吸引力F_(ad)与黏附能W_(ad)随着颗粒粒径增大而增加,F_(at)由3.21 nN增大到3.75 nN,增大约16.8%,W_(ad)由2.03×10^(-16) J增大到2.20×10^(-16) J,增大约8.4%,F_ad与W_(ad)的增大充分反映了颗粒间的黏附性增强,颗粒间能量势垒增大,团簇颗粒间更为稳定.随着颗粒平均粒径的增大,导致了颗粒间吸引力、黏附力及黏附能增大,颗粒逐渐团聚,由枝状向簇状转变,逐渐呈山峰状堆积,颗粒致密度、团簇大小均增大,说明颗粒间作用力的变化与颗粒形貌之间存在一定的影响关系.The diesel engine particulate which is one of the major sources of PM, affects the development of human health and production activities seriously. With the continuous strict of emission regulations, the diesel engine particles are subject to strict restriction in terms of quality and quantity. At present, the diesel particulate filter technology is an important technical measure to reduce the exhaust particulate matter of the diesel engine. And the efficient capture of particles is one of the key technologies for the diesel particulate filter. Diesel engine exhaust particles undergo nucleation, surface growth, agglomeration and other processes, in which the degree of agglomeration of exhaust particles will directly affect its number density, scale and the trapping efficiency of the filter and so on. The reason why particles can be agglomerated is mainly due to the interaction between the particles. Therefore, to explore the relationship between the force and the effect of particle agglomeration, it is necessary to carry out the study on the interaction between the exhaust particles of diesel engines. The interaction between particles will affect the process of particle agglomeration and related parameters significantly. The main forces include van der Waals force, electrostatic force and liquid bridge force. In this paper, theoretical models of Hamaker and some others are used to analyze the force between particles in the ideal state. The test methods of atomic force microscopy （AFM） and transmission electron microscopy （TEM） are used to investigate the total attraction force, adhesion force and adhesion energy between diesel exhaust particulates in dry environment （relative humidity RH ≤ 20%）, and measure the total attraction force, adhesion force and adhesion between particles, and explore the relationship between particle size and particle size. The results show that the particle size increases from 25 to 45 nm, the Van der Waals force increases about 4.6 times, the electrostatic force increases

关 键 词：柴油机 排气颗粒 力学特征 颗粒形貌 

分 类 号：TK421.5[动力工程及工程热物理—动力机械及工程]