Analysis and optimization of gel-cast ceramic foam diesel particulate filter performance

Abstract

Gel-cast ceramic foams potentially offer a more robust configurable alternative filtration medium to monolithic wall flow filters (WFFs) for the reduction in particulate matter (PM) emissions from diesel internal combustion engines. The fundamental back pressure and filtration efficiency characteristics of gel-cast ceramic foam diesel particulate filters (DPFs) have been investigated. Methodology is developed for the first time that allows the calculation of the effect of local PM loading on the pressure drop characteristics from experimental data without problems caused by the non-uniform PM loading in the filter that can be applied to all depth bed filtration media. The back pressure and filtration efficiency relationships were used to develop graphical design spaces to aid development of application-specific DPFs. Effects of PM distribution on the pressure drop of the filter are presented. Filters with a non-even distribution of PM were found to have lower pressure drops than filters with an evenly distributed PM for the same average specific PM loadings. The predictions showed that gel-cast ceramic foams can achieve comparable back pressure, filtration volume, and PM holding capacity with WFFs with a lower filtration efficiency of about 80 per cent. The model demonstrated that greater than 90 per cent filtration efficiency can be achieved with filter volumes of about 0.6 times the volume of a WFF with a lower PM holding capacity.