Study of SiC Application to Diesel Particulate Filter (Part 1): Material Development

We studied the use of SiC porous material for diesel particulate filters. Crystallities of SiC grow into hexagonal plates during sintering,but their sizes have not been controllable yet. We developed a production process that makes the average pore diameter as desired in limiting the pore size distribution to a narrow range. Diesel particulate filters made of SiC greatly reduce pressure loss even when a large quantity of particulates accumulates as compared with conventional wall-flow type filter of cordierite of the same size. This enables particulate filter to be made smaller. The good thermal conductivity of SiC allows fast regeneration without a temperature spike, but its large coefficient of thermal expansion causes heat cracks during rig tests and engine bench tests. The rig tests showed that the heat cracking problem can be solved if the length and diameter are below a certain threshold for each. Thus, we developed a split-type of diesel particulate filter, which consists of a number of filter segments with a square section, and seal materials having good thermal conductivity, which are sandwiched between segments. And the split-type of diesel particulate filter can easily be adapted to each engine volume.