Study On The Morphology And Oxidation Activity Of Soot Particles From Diesel Engine Exhaust

The microstructure of soot particles is a kind of physical structure,which is characterized by high electron microscopy.It has a typical "shell core" structure,which is closely related to the engine operating conditions,particle formation process and oxidation activity.Therefore,the study of the relationship between the microstructure and oxidation activity of the soot particles in the exhaust gas of the engine has important theoretical and practical significance for the further understanding of the soot formation process and guiding post-discharge treatment of the engine.This paper is mainly based on the soot particles TEM image processing software-SootFringe,which is designed by ourselves,using technology of fast cylinder sampling system,high electron microscopy and thermogravimetric analysis(TGA),analyzing the connection of the micro morphology and the oxidation activity of sample and actual soot systematically.The main contents and results are as follows.According to the microscopic characteristics of soot particles,based on the modern image processing technology,design soot image processing software – SootFringe.Using histogram equalization,Gauss low-pass filter,top hat transform,Fu Liye transform,image thinning,post processing(microcrystalline correction)and a series of image processing method,denoised and modified the original TEM image,and it can be used to extract the microscopic characteristic parameters of soot particles.Combined with image processing software and thermogravimetric analysis(TGA)technology,considering the effect factors of different heat treatment temperature and different kinds of soot particles,systematically analyzed the relationship between the microscopic morphology and the oxidation activity of the sample soot(simulated soot).The results show that with the increase of heat treatment temperature,the fringe length increase,the fringe separation distance and tortuosity decrease,the arrangement is more regular,the graphitization degree increases,and the oxidation activity decreases.At the same time,it is also found that the difference of the carbon smoke can lead to the difference of the micro morphology and oxidation activity.The soot particles in the exhaust gas of the actual engine were sampled and analyzed,which explores the change rules of microscopic parameters and particle soot oxidation activity of different load,injection pressure and fuels.The study find that most of the fringe length of the soot particles is between 0.2~3 nm,the separation distance is 0.28~0.52 nm,and the tortuosity is in the range of 1~1.5.With the increase of pressure and load,micro parameters of soot particles are similar.Fringe length is increased while the fringe separation distance and tortuosity is decreased,the arrangement of carbon fringe layers is more regular and the graphitization degree is increased,which makes it difficult to be oxidized.Compared with butanol diesel oil(B50)and pure diesel fuel(B00),the fringe length of soot particles with B50 emission is smaller,the separation distance between layers and the tortuosity are larger,the arrangement is more chaotic,the proportion of active carbon atoms increases,and the oxidation activity is higher.