Simulation of flow and heat transfer in diesel particulate filter

Abstract

Particulate matters (PM) including soot in diesel exhaust gas are severe environmental problems. It is expected that emission of soot particles can penetrate into the lung, causing human carcinogenic effects. To reduce these emissions especially from heavy-duty vehicles such as cargo trucks and buses, a diesel particulate filter (DPF) has been developed for the after-treatment of exhaust gas. In simple explanation of DPF, it traps PM when exhaust gas passes its porous wall. However, since the filter would be plugged with particles to cause an increase of filter back-pressure, filter regeneration process is needed. In this study, we simulate the flow in DPF by the lattice Boltzmann method (LBM). So far, the LBM has been widely used in fluid simulation, and has been an alternative and promising numerical scheme. It has been confirmed that, through the Chapman-Enskog procedure, the Navier-Stokes equations are derived from LB equations. In the LBM, the treatment of boundary conditions is simple and easy, and it is appropriate to simulate porous media flows such as DPF. In this paper, our approach for LB simulation of combustion is briefly explained. Here, the real filter is used in the simulation. The inner structure of the filter sample is scanned by a 3D X-ray CT technique. By conducting tomography-assisted simulation, we obtain local velocity and pressure distributions in the filter, which is hardly obtained by measurements. First, the flow and pressure profiles are visualized, compared with the empirical equation of the Ergun equation. Then, the soot combustion is simulated. Based on the temperature change and reaction inside the filter, the heat and mass transfer in the filter regeneration process is discussed.