Numerical Simulation Of Characteristics Of Pm Capture And Regeneration Combustion In Wall-flow DPF

As a new generation of diesel engine exhaust after-treatment device,Diesel Particulate Filter(DPF)can capture particulate matters(PM)in exhaust gas with its unique porous structure,which can effectively reduce the emission of particulate pollutants.The process of particle capture and regeneration control in DPF consists of complicated multiphase flow,heat and mass transfer,and chemical reactions.In order to further improve the capture efficiency,characteristics of the physical and chemical transport within DPF is systematical investigated.In this paper,a DPF pore-scale numerical calculation model is developed based on the new lattice Boltzmann method,aiming to explore the micro-and nanoscale gas-solid two-phase flow,heat and mass transfer,and regeneration combustion chemical reaction process in the thin wall of Si C-filter.First of all,the incompressible D2G9 model based on the Lattice Boltzmann method is used to simulate the distribution of flow field and pressure field.And the influence of inlet velocity,pore structure,and filter thickness on the flow field and pressure distribution in a single channel is discussed in detail.The simulation results show that the pressure distribution in the DPF channel is uniform at low inlet velocity.The airflow in the channel with low pore diameter tends to pass through the filter wall from the end of the channel at high inlet velocity.The thicker the filter wall is,the greater the pressure difference is between the inlet and outlet.In addition,based on the Cellular Automata probability model,the particle motion rules are set and coupled with the Lattice Boltzmann method.The characteristics of gas-solid two-phase flow and particle deposition in a single channel of wall-flow DPF are numerically simulated by the verified calculation model.The simulation results show that the influence of airflow on the motion of particles is small at low flow rate.The motion is mainly based on the diffusion mechanism,and the deposition distribution in the channel is relatively identical.The motion of particles mainly depends on the inertial mechanism at high flow rate,and the particles mainly deposit in the middle and back sections of filter channel.The smaller the average pore diameter of the filter is,the more likely the particles are to deposit on the front wall of the filter,where forming the filter cake layer is easier.In the end,based on the Si C-DPF thin-wall microstructure scanned by the Scanning Electron Microscope(SEM),the high-precision two-dimensional three-phase Si C-DPF thin-wall digital model is reconstructed by the Quartet Structure Generation Set(QSGS).And the Lattice Boltzamnn method is used to carry out multi-field coupled simulation calculation for the above Si C-DPF thin-walled digital model.The gas flow,heat and mass transfer,chemical reaction and solid heat conduction were mainly analyzed.The simulation results show that the model can effectively capture the regeneration combustion phenomenon at the pore scale.Meanwhile,it can predict and control various mechanisms of regeneration combustion.In terms of oxygen utilization and stable combustion temperature,diffusion control is more suitable for regeneration combustion,that is to say,low Pe number and high Da number.In summary,based the Lattice Boltzamnn methods,the complicated multiphase flow,heat and mass transfer,and chemical reaction processes at the pore scale of DPF are discussed and analyzed in this paper.To overcome the limitations of experimental microscopic visualization,this paper has important theoretical and practical engineering significance to improve efficiency,optimize regeneration control,and reduce DPF production costs.