Simulation on soot deposition in in-wall and on-wall catalyzed diesel particulate filters

In order to decrease the regeneration temperature of diesel soot deposited in the diesel particulate filter (DPF), the catalyzed DPF is generally used. Since the catalyst is made of expensive noble metals such as platinum, it is better to reduce the amount of catalyst. For that purpose, we need to know the influence of the catalyst on the soot deposition process. In this study, the flow and the soot deposition of the catalyzed DPF (CDPF) have been simulated. The substrate structure of the filter was obtained by an X-ray CT technique. Here, two types of the catalyst coating were considered, which were in-wall and on-wall CDPFs. For both cases, we set the same amount of catalyst. The effects of the catalyst on the pressure drop were evaluated by comparing the simulation without the catalyst. The permeability of the catalyst layer was estimated based on the experimental pressure drop. In particular, the contact ratio of the deposited soot and the catalyst layer was discussed to obtain the information on the regeneration efficiency. It was found that, due to the catalyst, the soot deposition process was affected. Resultantly, the pressure drop of the on-wall CDPF was smaller than that of the in-wall CDPF. In the case of the on-wall CDPF, more deposited soot can be contacted with the catalyst layer, suggesting the higher efficiency for the filter regeneration.