Visualization Study of PM Trapping and Reaction Phenomena in Micro-Structural Pores Through Cross Section of DPF Wall

摘要

Trapping of diesel particulates and phenomena of chemical reaction in regeneration were investigated by visualization through the cross-sectional area of a diesel-particulate-filter wall, using a digital microscope with a high focusing depth. Herein, SiC-DPF walls were polished up to make a uniform height and to create a mirror-like surface on each SiC-particle grain. At the beginning of the trapping process, it was observed that large particulates were trapped once in the small pores inside the wall, and then, since the flow pattern was changed drastically, the trapped particulates were pushed out and blown off again, and finally, trapped in a region further downstream. As time passed, image analysis disclosed that since fine particulates were deposited around the SiC-particle-grain surface, the flow channels became increasingly narrow. As a result, most of the particulates were trapped in the vicinity of the inlet of the wall, resulting in transition from depth filtration to surface filtration. In the regeneration process, on the other hand, the crevices made on the surface-filtrated particulate cake were strongly dependent on the configuration of the DPF-wall inlet. In the inside of the wall, trapped particulates reacted with oxygen heterogeneously at each location.