Partial wall-flow filter and diesel exhaust system and method

Abstract

A exhaust system and method for venting exhaust from an engine, such as a diesel engine, through an exhaust line coupled to the engine includes a first particulate filter disposed in the exhaust line and “close-coupled” with the engine, and a second particulate filter spaced a distance (d) from the first filter. The first particulate filter is “close-coupled” so that it operates in a passive regeneration mode to a greater extent than the second particulate filter. The first particulate filter may be a partial wall-flow filter including some plugged and some open channels. Some of the plugged channels may be plugged adjacent to an inlet end and others may be plugged adjacent to an outlet end. A partial wall-flow filter is also described having some unplugged flow-through channels and some plugged channels wherein some plugged channels are located adjacent to the inlet end and some are located adjacent to the outlet end.

1 . An exhaust system for venting exhaust from an engine through an exhaust line coupled to the engine, comprising:
 a first particulate filter disposed in the exhaust line and close-coupled with the engine, the first particulate filter operating in a first relative extent in a passive regeneration mode; and   a second particulate filter positioned inline with, and spaced a distance from, the first particulate filter and operating to a second relative extent in a passive regeneration mode less substantially than the first relative extent.   
   
   
       2 . The diesel exhaust system of  claim 1  wherein the first particulate filter exhibits an initial filtration efficiency of greater than 45%. 
   
   
       3 . The diesel exhaust system of  claim 2  wherein the initial filtration efficiency is greater than 50%. 
   
   
       4 . The diesel exhaust system of  claim 2  wherein the initial filtration efficiency is greater than 60%. 
   
   
       5 . The diesel exhaust system of  claim 2  wherein the initial filtration efficiency is greater than 70%. 
   
   
       6 . The diesel exhaust system of  claim 1  wherein the first particulate filter exhibits greater than 50% plugged channels as compared to a total number of channels. 
   
   
       7 . The diesel exhaust system of  claim 6  further comprising greater than 60% plugged channels as compared to the total number of channels. 
   
   
       8 . The diesel exhaust system of  claim 1  wherein the first particulate filter exhibits a total porosity of greater than 45%. 
   
   
       9 . The diesel exhaust system of  claim 8  further comprising total porosity greater than 50%. 
   
   
       10 . The diesel exhaust system of  claim 8  further comprising total porosity greater than 55%. 
   
   
       11 . The diesel exhaust system of  claim 8  further comprising total porosity greater than 60%. 
   
   
       12 . The diesel exhaust system of  claim 8  further comprising total porosity of 63% or greater. 
   
   
       13 . The diesel exhaust system of  claim 1  wherein the first particulate filter exhibits:
 a total porosity of greater than 45%,   greater than 50% plugged channels as compared to a total number of channels, and   at least some unplugged channels.   
   
   
       14 . The diesel exhaust system of  claim 13  wherein the total porosity is greater than 60%. 
   
   
       15 . The diesel exhaust system of  claim 1  wherein the first particulate filter exhibits:
 a total porosity of greater than 60%,   greater than 60% of the channels are plugged channels as compared to a total number of channels, and   at least some unplugged flow-through channels.   
   
   
       16 . The diesel exhaust system of  claim 1  wherein the first particulate filter exhibits:
 a total porosity of greater than 60%,   greater than 50% of the channels are plugged channels as compared to a total number of channels,   at least some unplugged flow-through channels, and   some of the plugged channels are plugged adjacent to an inlet end and some of the plugged channels are plugged adjacent to an outlet end.   
   
   
       17 . The diesel exhaust system of  claim 1  wherein the first particulate filter includes some unplugged flow-through channels and some plugged channels wherein at least some of the plugged channels are plugged adjacent to both an inlet end and an outlet end. 
   
   
       18 . The diesel exhaust system of  claim 17  wherein a percentage of plugged channels adjacent to the inlet end is less than a percent of plugged channels adjacent to the outlet end. 
   
   
       19 . The diesel exhaust system of  claim 1 , wherein the first particulate filter comprises a ceramic honeycomb substrate comprising a plurality of channels, wherein a first percentage of the channels are plugged and a second percentage of the channels are open and wherein the number of plugged channels divided by a total number of channels, and expressed as a percentage, is greater than 50%. 
   
   
       20 . The diesel exhaust system of  claim 19  wherein the percentage of plugged channels to total channels is greater than 60%. 
   
   
       21 . The diesel exhaust system of  claim 1  wherein the first filter includes an inlet end and outlet end, and the plugged channels are positioned only adjacent the outlet end. 
   
   
       22 . The diesel exhaust system of  claim 1  wherein the honeycomb substrate has an inlet end and an outlet end, and the plugged channels include plugs adjacent to both the inlet end and the outlet end. 
   
   
       23 . The diesel exhaust system of  claim 1  wherein the first filter plugged channels and unplugged flow-through channels and a hydraulic diameter of the plugged channels is different than a hydraulic diameter of the unplugged flow-through channels. 
   
   
       24 . The diesel exhaust system of  claim 1  wherein the first particulate filter is positioned downstream of a turbocharger disposed in the exhaust line. 
   
   
       25 . The diesel exhaust system of  claim 1 , further comprising a diesel oxidation catalyst positioned between the first particulate filter and the second particulate filter. 
   
   
       26 . The diesel exhaust system of  claim 1  wherein the second particulate filter is positioned inline with, and spaced a distance (d) of greater than or equal to 12 inches (30.5 cm) from the first particulate filter. 
   
   
       27 . The diesel exhaust system of  claim 1  wherein the first particulate filter includes a first inlet temperature (T 1 ) and the second particulate filter includes a second inlet temperature (T 2 ), wherein a ratio of inlet temperatures (T 1 /T 2 ) is greater than or equal to 1.1. 
   
   
       28 . The diesel exhaust system of  claim 1  wherein the first particulate filter is positioned at a distance from the engine wherein during operation, the inlet temperature (T 1 ) is at a temperature above 250° C. for a some portion of the operation. 
   
   
       29 . A diesel exhaust system, comprising:
 a first particulate filter close-coupled with the exhaust manifold, the first particulate filter having a first percentage of plugged channels and a second percentage of unplugged flow-through channels; and   a second particulate filter positioned inline with and spaced a distance (d) of greater than or equal to 12 inches (30.5 cm) from the first particulate filter and including only plugged channels such that the first filter exhibits passive regeneration to a substantially greater extent than the second filter.   
   
   
       30 . The diesel exhaust system of  claim 29  wherein the second particulate filter is a wall flow filter including only plugged channels. 
   
   
       31 . The diesel exhaust system of  claim 29  wherein the first particulate filter includes plugged channels and unplugged flow-through channels, and the plugged channels include some channels that are plugged adjacent to an inlet end and other channels that are plugged adjacent to an outlet end. 
   
   
       32 . A method of operating a diesel exhaust system, comprising the steps of:
 passing an exhaust gas through a first particulate filter disposed in an exhaust line wherein the first particulate filter includes a first inlet temperature (T 1 ), the first particulate filter having a first percentage of plugged channels and a second percentage of unplugged flow-through channels wherein the exhaust gas is first filtered; and   passing the first filtered exhaust gas through a second particulate filter positioned inline with and spaced a distance from the first particulate filter wherein the second particulate filter includes a second inlet temperature (T 2 ), wherein the first exhaust gas undergoes a second filtering and a ratio of inlet temperatures (T 1 /T 2 ) is greater than or equal to 1.1.   
   
   
       33 . A partial wall-flow filter, comprising:
 plugged channels and unplugged, flow-through channels wherein the plugged channels include some channels that are plugged adjacent to an inlet end and other channels that are plugged adjacent to an outlet end.   
   
   
       34 . The partial wall-flow filter of  claim 33 , further comprising a percentage of plugged channels to total channels greater than 50%. 
   
   
       35 . The partial wall-flow filter of  claim 33 , further comprising a total porosity of greater than 45%. 
   
   
       36 . The partial wall-flow filter of  claim 33 , further comprising a total porosity of greater than 50%. 
   
   
       37 . The partial wall-flow filter of  claim 33 , further comprising a total porosity of greater than 60%. 
   
   
       38 . The partial wall-flow filter of  claim 33 , further comprising a total porosity of greater than 50%, and greater than 10% of the plugged channels located adjacent to an inlet end and greater than 40% located adjacent to the outlet end. 
   
   
       39 . The partial wall-flow filter of  claim 33 , further comprising wherein a number of channels plugged adjacent to the inlet end is less than a number of channels that are plugged adjacent to the outlet end. 
   
   
       40 . The partial wall-flow filter of  claim 33 , further comprising wherein a number of channels plugged adjacent to the outlet end is less than a number of channels that are plugged adjacent to the inlet end. 
   
   
       41 . The partial wall-flow filter of  claim 33 , further comprising an oxidation catalyst residing on a porous wall of the partial wall-flow filter.