Partial wall-flow filter and method

A partial wall-flow filter, comprising:

• an inlet end, an outlet end, and a plurality of parallel channels disposed and configured to flow fluid from the inlet end to the outlet end, the channels being defined by a plurality of porous walls;
• wherein a first portion of the channels have a first hydraulic diameter Dh1, a second portion of the channels have a second hydraulic diameter Dh2 smaller than the first hydraulic diameter Dh1, and wherein the ratio of Dh1:Dh2 is in the range of 1.1 to 1.6;
• wherein none of the channels are plugged at the inlet end, and only channels having hydraulic diameter Dh1 are plugged at the outlet end.

A method of operating an exhaust system, comprising:

• providing a partial wall-flow filter having an inlet end, an outlet end, and a plurality of parallel channels disposed and configured to flow fluid from the inlet end to the outlet end, the channels being defined by a plurality of porous walls, wherein a first portion of the channels have a first hydraulic diameter Dh1, a second portion of the channels have a second hydraulic diameter Dh2 smaller than the first hydraulic diameter Dh1, wherein the ratio of Dh1:Dh2 is in the range of 1.1 to 1.6, channels having hydraulic diameter Dh1 are plugged at the outlet end, and channels having hydraulic diameter Dh2 are flow-through channels;
• and
• passing exhaust gas having particulate matter entrained therein through the partial wall-flow filter wherein some of the particulate matter is captured and some passes through the flow through channels.