Patent ID: 8240138

Claim:
A system for reducing particulate matter emission in engine exhaust gas, said system comprising: a first particulate filter including a plurality of particulate filter units configured to engage a respective cross-sectional region of said engine exhaust gas including particulate matter, each particulate filter unit comprising a plurality of channels aligned in a flow direction of said engine exhaust gas, said channels being selectively configured with a varying cross-sectional area density, which varies based upon an expected cross-sectional distribution of a flow rate of the exhaust gas passing through the channels in the first particulate filter, wherein said plurality of channels of each particular filter unit comprises: a plurality of first channels having a blocked inlet and an open outlet; and a plurality of second channels having an open inlet and a blocked outlet, each first channel being positioned adjacent to a second channel, and each second channel being positioned adjacent to a first channel; a plurality of walls separating adjacent channels of said plurality of channels, said walls having a varying thickness, which varies based upon the expected cross-sectional distribution of the flow rate of the exhaust gas; and a plurality of pores within said plurality of walls trapping particulates in the exhaust gas, said pores being configured to vacate a varying ratio of the area of said walls, wherein said ratio varies based upon the expected cross-sectional distribution of the flow rate of the exhaust gas; a second particulate filter coupled to receive exhaust gas from the first particulate filter, the second particulate filter comprising a plurality of particulate filter units configured to engage a respective cross-sectional region of the exhaust gas from the first particulate filter, each particulate filter unit of said second particulate filter comprising a flow-through unit, each particulate filter unit comprising a plurality of channels aligned in a flow direction of the exhaust gas from the first particulate filter, said channels being selectively configured with a varying cross-sectional area density, which varies based upon an expected cross-sectional distribution of a flow rate of the exhaust gas passing through the channels in the second particulate filter; a plurality of walls separating adjacent channels of said plurality of channels, said walls having a varying thickness, which varies based upon the expected cross-sectional distribution of the flow rate of the exhaust gas passing through the channels in the second particulate filter, wherein for at least some of particulate filter units of the first and second particulate filters, at least one of said cross-sectional area density of said plurality of channels, said respective wall thickness and said ratio of pores within said walls is selected to optimize a flow and/or thermal characteristic of a filter coupling arrangement comprising a combination of said first and second particulate filters.