Research On Gas-Particle Two-Phase Flow Characteristic In Diesel Particulate Filter

Further increase of diesel vehicles proportion is the trend, but the high level ofparticulate emission is one of the key issues which restrict the development ofdiesel engines. In the various ways of particle post-processing at present, dieselparticulate filter is considered as a very prospective way to reduce the particle.In this thesis, 2D structure model of diesel particulate filter is set up. After thegas-particle flows mathematical model is solved, the pressure field of dieselparticulate filter, the velocity field of gas phase and distribution of particleconcentration field are obtained. At the same time, we study how different inletvelocity, surface permeability of porous medium and inlet concentration have aninfluence on gas flow rate and also how different inlet velocity, surface permeabilityand diameter of particle have an influence on uniformity of particle concentration.Then set up the diesel particulate filter 3D structure model, solve the gas-particleflow model and obtain the pressure difference between the inlet and outlet. Also getthe distribution of the gas velocity field and particle concentration field in filterfront face. Then after region divided on the section according to the distribution andselect some special points in this area, we analyze the gas-particle flow property ofthe whole filter body and compare the efficiency of the diesel particulate filter ofdifferent particulate diameters by calculate the model.The results show that: the faster the inlet velocity, the more dramatic changesof gas velocity and particle concentration in expanding region and filter body. Theaxial distribution of gas velocity and particle concentration in the filter body is even,but the radial distribution is uneven. Central axis and wall accessories are large andthe middle is small. When the inlet velocity is slow, the gas velocity and particleconcentration is merely changed. The smaller the surface permeability, the slowerthe gas velocity and the greater difference of particle concentration between inletand outlet of filter body. The greater of the difference shows the higher efficiency ofthe diesel particulate filter. With the increase of smoke concentration, the changesof gas flow velocity is more obvious. However, the trend of velocity change in thecorresponding position is basically the same. That is in the central axis and wallarea of diesel particulate filter, the velocity is fast and velocity in the area betweenthem is relatively slow. The smaller of the particle diameter, the more obvious diffusion of particle. So the better of distribution of particle concentration and thebigger of diameter, the greater difference of particulate concentration between inletand outlet and the bigger deposition of particle. That is the higher efficiency ofdiesel particulate filter.There is a large amount of particle deposition near the central axis of filterbody and the wall region of particulate filter. With the capture time past,sedimentary particles inside the filter body are more and more, which increase theexhaust resistance gradually. so it can reduce the engine output power and increasefuel consumption. For that reason, when regenerate of the particulate filter,improving the efficiency of regeneration of these areas is mostly recommend.This study provides the basis to further improve the efficiency of dieselparticulate filter.