Simulations on flow and soot deposition in diesel particulate filters

To reduce particulate matter, including soot in diesel exhaust gas, a diesel particulate filter has been developed. In the after-treatment of exhaust gas, the filter traps particulate matter when the exhaust gas passes its porous wall. An increase of particulate matter accumulation could cause technological problems due to the higher filter back-pressure. This can result in a subsequent worsening of fuel efficiency and a decrease in engine output. However, it is difficult to experimentally observe the phenomena in diesel particulate filters. In this study, we simulated the flow with soot deposition using the lattice Boltzmann method. To discuss the flow in a real cordierite filter, a tomography-assisted simulation was conducted, and the inner structure of the filter was scanned using a three-dimensional X-ray computed tomography technique. The local velocity and pressure distributions in the filter were clearly visualized. To model the soot deposition, a parameter of soot deposition probability was used. Results show that the pressure drop increases as more soot is deposited. When the soot deposition probability of the parameter of soot deposition is larger, the soot deposition region is limited to the filter wall surface, corresponding to surface filtration. The pressure drop is smaller as the parameter of soot deposition is increased.