Phenomena of PM Deposition and Oxidation in the Diesel Particulate Filter

The diesel particulate filter (DPF) has attracted strong attention as a desirable after-treatment device for the particulate matter (PM) contained in exhaust gas of diesel engine. When particulate matter was deposited on a DPF, the pressure drop increases due to the PM trapping in the surface cavities of the DPF. After that, an active regeneration is required. Since more fuel is required for the regeneration in addition to the normal driving (passive regeneration), the fuel economy deteriorates. In order to improve the performance, a passive regeneration is necessary. In this study, we compared the dependence of the shape and depth of the cavity of the DPF on the PM trapping process by a comprehensive overall model and numerical calculation. We found that the pressure drop and elapsed time of the PM trapping varied, strongly depending on the cavity shape of the DPF surface. Further we examined the relative importance of the amount of PM deposit and the surface cavity shape of the DPF. We discovered that the pressure drop was lower when the shape of surface cavity in DPF became flatter and shallower. Based on the above result, we simulated a combination of hydrodynamics and oxidation reaction during PM deposition and combustion. Through this simulation, we constructed a series of models from PM deposition to combustion process. The result provides a quantitative evaluation and design of the surface cavity in the DPF leading to better production process of porous ceramic parts.