Effects of Filter Substrate Structure on Flow and Filtration Efficiency of Gasoline Soot

For reduction of gasoline soot emitted from gasoline direct injection (GDI) engines, we need a gasoline particulate filter (GPF). Recently, the particulate filter coated by a three-way catalyst (TWC) necessary for the aftertreatment of gasoline vehicles has been proposed. Since the washcoat would increase the filter backpressure which largely affects the fuel consumption, we need to optimize the filter substrate structure for lower filter back pressure as well as better filtration efficiency. In this study, numerical simulations of the flow with the soot deposition in the GPF were performed by changing the substrate structure. A lattice Boltzmann method (LBM) was used. First, the inner structure of the real filter was obtained by an X-ray CT, called the original filter. Next, we created several filters by decreasing or increasing the porosity (called thick or thin). The unique filter was the substrate with the front thick and the rear thin for improving the filtration efficiency but decreasing the pressure drop simultaneously. For the filtration mechanism, Brownian diffusion and interception effects were considered. In comparison with the original filter, the effects of the substrate structure on flow and filtration efficiency were revealed, derived that the pressure drop can be reduced by decreasing the substrate volume which does not contribute to the soot deposition.