The Particle Number (PN) emission limit is implemented for Direct Injection (DI) gasoline from EU6 regulation in European region. The wall-flow type ceramic filter technology is an essential component for Diesel PN emission control, and will be one potential solution to be investigated for the future Gasoline DI PN emission control demand. Especially the requirement of lower pressure loss with smaller filter volume is very strong for the filter substrate for Gasoline DI compared to DPF, not to lose better fuel economy benefit of Gasoline DI engine.
Re-crystallized SiC (R-SiC) has high strength as its own property, and enable for Gasoline Particulate Filter (GPF) design to make the wall thickness thinner and the porosity higher compared to the other ceramic materials. In this study, the three-way catalyst (TWC) coated pressure loss and catalytic light-off performance those are the key functions for GPF was evaluated for thin-wall high-porosity R-SiC GPF prototypes to confirm the effectiveness of these design directions. The different wash-coat amount was coated on 6, 8, and 13 milli-inch wall thickness prototypes with 200 cpsi (cells per square inches) of cell density and 60% of porosity and evaluated gas conversion efficiency be synthetic gas bench.
As a result, it was found that thinner wall thickness design had lower pressure loss before coating and that advantage was kept after coating until 60 g/l wash-coat amount. 6 mil wall thickness design had a potential of about 30% downsizing of the filter size compared to 13 mil one from the point of view of coated pressure loss. Thinner wall thickness had higher gas conversion efficiency especially at cold-start period due to smaller heat capacity compared to thicker wall thickness design. The PN filtration efficiency was influenced by the wall thickness and pore size distribution after catalyst coating. As a conclusion, it was confirmed that the thinner-wall high-porosity R-SiC GPF has a possibility of catalyst amount reduction, better packaging for TWC coated GPF system because of its downsizing potential due to lower pressure loss and smaller heat capacity.