Dynamic filtration modeling in foam filters for diesel exhaust

Diesel Particulate Filters (DPFs) are probably the most effective means for trapping the exhaust emitted particulate from diesel engines. Foam type fi lters become a promising alternative to the common wall flow filters, since they are effective in filtering small size particles and provide a larger specific surface area for catalytic coatings. A mathematical model taking i nto account the significant phenomena during the dynamic filtration of foam filters is developed. The model predicts the filtration efficiency and the induced backpressure as function of the geometric filter properties and op erating conditions. A novel approach is employed which considers both "deep -bed" and "cake" filtration characteristics in the filter. Due to the parti cular structure properties of the foam filters it is necessary to define a characteristic parameter, which differentiates among different filter types . This parameter, which has a physical meaning, is easily derived by simple experimental measurements. The model is employed to identify and understan d the critical parameters of the phenomenon. Indicative parametric runs are presented, which illustrate the applicability of the model in system optim ization procedures.