Simulation Study Of Particle Deposition Inside Microchannel Of Diesel Particulate Filter

With the development of society and the progress of industry,the appearance of cars has greatly improved people’s production efficiency and changed people’s way of travel.Diesel engine is widely used because of its high efficiency and high reliability.But,compared with gasoline engine,diesel engine emits more carbon particles and NO_X,and Diesel Particulate Filter(DPF)has become an essential exhaust aftertreatment device.With the improvement of people’s awareness of environmental protection and the continuous tightening of emission regulations,higher requirements are put forward for DPF.Therefore,it is necessary to conduct micro-scale research on DPF.The research object of this paper are mainly the gas-solid two-phase flow and porous media.The dynamic filtration process of the DPF is simulated by using Eulerian-Eulerian approach,and the particle deposition distribution along the wall surface is simulated by using Eulerian-Lagrangian approach.In the modeling process,the two-dimensional microscopic single-channel model is firstly established,and then the transient filtration model is built and coupled into the channel model.Drag force,gravity,Brownian force and Saffman lift are all considered in this model.Moreover,Brownian diffusion mechanism,interception mechanism and inertial mechanism are all considered in this paper.Based on the established and verified model,the particle deposition distribution inside porous media is studied in this paper.The results showed that most of the particles deposited in the top 15%of the porous media,especially the 10 nm particles and 1000 nm particles,while the 100 nm particles would penetrate deeper into the porous media.In the axial direction of the channel,more particles are deposited near the inlet and outlet of the channel.With the increase of DPF inlet velocity,through-wall velocity will rise obviously,and more particles penetrate deeper into the porous media.Besides,DPF filtration efficiency will drop significantly,especially for 10 nm particles and 100 nm particles.Due to the large inertia of 1000 nm particles,the capture of them by DPF mainly relies on the interception mechanism,so it is less affected by the inlet velocity.The increase of inlet velocity also causes the pressure drop to rise,and the pressure drop will rise further after the deposition of carbon particles,especially when the area near the wall surface reaches saturation.Furthermore,the simulation study shows that the pressure drop near the inlet and outlet of the channel is significantly higher than that in the middle of the channel along the axial direction of the channel.In addition,using Eulerian-Lagrangian approach,the results show that over the surface of the channel,all particles preferentially deposit at the end of the channel.This phenomenon is more pronounced for 1000 nm particles,because they have higher inertia and are capable of following the fluid flow.However,for 10 nm particles,the particle motion trajectories are significantly by Brownian motion,so particle motion is more random and does not completely follow fluid flow.The existence of the membrane on the surface of the DPF channel will affect the flow field and pressure field in the channel,making the“V”type through-wall velocity curve become more gentle,thus further affecting movement and deposition distribution of particles.The membrane can effectively improve filtration efficiency,especially for100 nm particles,and the filtration efficiency curve along the axial direction of the channel is more straight.Besides,the particle deposition distribution inside porous media is more uniform,and the difference between the distribution of particles with different particle sizes is also reduced.Moreover,because the membrane has lower porosity and pore diameter,porous media can reach the saturation state to form the“cake”layer faster.In addition,carbon particles are more evenly distributed on the surface of the coated channel than on the uncoated channel.