Study on Wall Pore Structure for Next Generation Diesel Particulate Filter 2008-01-0618
A wall flow diesel particulate filter (DPF) having a novel wall pore structure design for reducing backpressure, increasing robustness, and increasing filtration efficiency is presented. The filter offers a linear relationship between soot loading and backpressure, offering greater accuracy in estimating the amount of soot loading from backpressure. Basic experiments were performed on small plate test pieces having various pore structure designs. Soot generated by a Cast-2F propane burner having a controlled size distribution was used. Cold flow test equipment that was carefully designed for flow distribution and soot/air mixing was used for precise measurement of backpressure during soot loading. The upstream and downstream PM numbers were counted by Scanning Mobility Particle Sizer (SMPS) to determine soot concentration in the gas flow and filtration efficiency of the test pieces. Microscope observations of the soot trapped in the wall were also carried out. A dual-layer pore structure in which the gas inflow side of the wall is given a filtration layer having small pores and a high porosity (void ratio) was demonstrated to drastically improve the filtration efficiency, drastically reduce the backpressure with Particulate Matter (PM) accumulation, as well as provide a linear relationship between soot loading and backpressure. This structure allows the porosity of the both body components to be independently chosen because filtration and backpressure are not easily affected by the pore structure of the wall bodies, making the structure suitable for both robustness-oriented and continuous-regeneration oriented applications.