Study on Next Generation Diesel Particulate Filter

Although diesel engines are superior to gasoline engines in terms of the demand to reduce CO₂ emissions, diesel engines suffer from the problem of emitting Particulate Matter (PM). Therefore, a Diesel Particulate Filter (DPF) has to be fitted in the engine exhaust aftertreatment system. From the viewpoint of reducing CO₂ emissions, there is a strong demand to reduce the exhaust system pressure drop and for DPF designs that are able to help reduce the pressure drop. A wall flow DPF having a novel wall pore structure design for reducing pressure drop, increasing robustness and increasing filtration efficiency is presented. The filter offers a linear relationship between PM loading and pressure drop, offering lower pressure drop and greater accuracy in estimating the accumulated PM amount from pressure drop. First, basic experiments were performed on small plate test samples having various pore structure designs. Second, referring to the evaluation result of the plate samples, the evaluation samples were developed into a honeycomb structure, and the pressure drop and filtration efficiencies were evaluated. An Inlet-Membrane pore structure on the inlet channel surface is given a filtration membrane having smaller pores was demonstrated to improve the filtration efficiency, reduce the pressure drop with PM accumulation, as well as provide a linear relationship between PM loading and pressure drop. Pressure drop characteristics of this structure are not dependent on the body material but the filtration membrane. Therefore, it is estimated that the characteristics of the filtration membrane determine the pressure drop characteristics, even if body materials are combined. This structure allows the porosity of the body materials to be independently chosen making the suitable structure for both robustness-conscious and continuous regeneration-conscious applications. In this paper, it is shown that the filtration membrane can be formed into a honeycomb structure applied to practical use as a DPF.