Diesel emission regulation becomes stringent more and more regarding both particulate matter (PM) and NOx in the worldwide. SCR coated DPF system is considered as one of the promising options for future diesel exhaust after-treatment because it has several benefits such as the downsizing of the system, quick light-off of the catalytic function due to mounting closed-couple position.
To integrate the SCR converter into the DPF, it is necessary to design the DPF substrate's porosity higher and pore size larger than conventional DPF to improve SCR catalyst coating capability. However to make the porosity higher will lose the robustness in general. Against these problems, it was studied to improve the high porosity DPF performances by applying the new technology to modify the thermal shock resistance property.
In this study, oxide film forming technology for the thermal shock resistance property modification was applied on the DPF substrate with 63% of porosity and 23um of mean pore size and evaluated soot mass limit, pressure loss and filtration efficiency. As the result, soot mass limit was increased to similar level with 57% porosity DPF because of thermal shock resistance coefficient was increased about 50% by oxide film forming on the surface of SiC porous material. The full-size high porosity DPF prototype was evaluated in the engine bench and it was confirmed that the high porosity SiC-DPF with oxide film forming technology had a possibility to achieve both the high SCR catalyst coating capability and high filtration efficiency after coating to meet Euro6 particle number emission limit to realize the SCR coated DPF system.