Exhaust aftertreatment device

Abstract

An exhaust aftertreatment device for an internal combustion engine is disclosed which contains multiple, parallel channels of a porous material, such as cordierite or silicon carbide, in which about some of the channels are plugged at an upstream end and other channels remain unplugged. In one embodiment, the substrate has an SCR coating and the engine has a urea supply system. Other embodiments include using TWC and LNT formulations. Several washcoat configurations and other specific geometries and dimensions to encourage crossflow, diffusion, and adsorption are disclosed herein.

1 . An exhaust aftertreatment device, comprising: 
 a substrate comprised of multiple channels of a porous material, said channels being substantially parallel, said substrate being disposed in an exhaust stream; and    plugs placed in a portion of said channels near one end of said substrate wherein another portion of said channels is unplugged along the entire channel length.    
   
   
       2 . The device of  claim 1  wherein said substrate further comprises a washcoat of an acidic material which is capable of adsorbing a reductant.  
   
   
       3 . The device of  claim 2  wherein said washcoat renders said substrate to be a SCR catalyst and said reductant is ammonia.  
   
   
       4 . The device of  claim 1  wherein said plugs are placed in about half of said channels.  
   
   
       5 . The device of  claim 1  wherein said plugs are placed in said channels evenly spaced on said end of said substrate.  
   
   
       6 . The device of  claim 1  wherein the device is placed in an internal combustion engine exhaust with said plugs receiving said engine exhaust.  
   
   
       7 . The device of  claim 1  wherein said substrate material has a porosity greater than 10% prior to applying a washcoat material.  
   
   
       8 . The device of  claim 1  wherein said substrate is comprised of cordierite.  
   
   
       9 . The device of  claim 1  wherein said substrate is comprised of silicon carbide.  
   
   
       10 . The device of  claim 1 , further comprising: flow restrictors on said unplugged channels, said flow restrictors being located at an opposite end of said substrate from said plugs.  
   
   
       11 . A method of manufacturing an exhaust aftertreatment device, comprising: 
 forming a porous substrate of multiple, parallel channels;    plugging some, but not all, of said channels near a first end of said channels; and    washcoating said substrate after said plugging wherein a second end of said channels are unplugged wherein said channels without plugs are unplugged along the entire channel length.    
   
   
       12 . The method of  claim 11 , further comprising: forming flow restrictors in channels without plugs, said flow restrictors being placed in said second end of said channels.  
   
   
       13 . The method of  claim 11  wherein about half of said channels are plugged.  
   
   
       14 . The method of  claim 11  wherein said substrate has a porosity greater than 20% prior to said washcoating.  
   
   
       15 . The method of  claim 11  wherein said substrate is comprised of cordierite.  
   
   
       16 . The method of  claim 11  wherein said substrate has 250 to 600 cells per square inch.  
   
   
       17 . The method of  claim 11  wherein said substrate has a porosity greater than 50% prior to said washcoating.  
   
   
       18 . An exhaust aftertreatment device, comprising: a substrate having multiple channels of a porous material, a centerline of said channels being substantially parallel, said channels further comprising a first group of unplugged channels and a second group of channels in which plugs are placed in said channels near one end of said substrate, said substrate being situated in an exhaust stream of an internal combustion engine wherein said first group of unplugged channels are unplugged along the entire length of said substrate.  
   
   
       19 . The device of  claim 18 , further comprising: a urea injector coupled to an exhaust of said engine, said injector located upstream of said substrate.  
   
   
       20 . The device of  claim 19 , further comprising: 
 an ammonia sensor coupled to said exhaust of said engine downstream of said substrate; and    an electronic control unit coupled to said engine, said urea injector, and said ammonia sensor, said electronic control unit commanding said urea injector based on an output of said ammonia sensor.    
   
   
       21 . The device of  claim 1  wherein a solid acidic material is deposited on a surface of said substrate thereby providing sites for urea reductant to be adsorbed.  
   
   
       22 . The device of  claim 1  wherein said substrate is made of cordierite having 80 to 600 cells per square inch.  
   
   
       23 . The device of  claim 1  wherein said first group and said second group are substantially similar in number.  
   
   
       24 . The device of  claim 1  wherein said first group is substantially greater in number than said second group.  
   
   
       25 . The device of  claim 1  wherein said substrate is made of cordierite having at least 10% porosity prior to washcoating.  
   
   
       26 . The device of  claim 1  wherein said substrate has a porosity greater than 50%.  
   
   
       27 . The device of  claim 1  wherein said substrate comprises tapered channels wherein said first group decreases in diameter from an upstream end to a downstream end and said second group increases in diameter from said upstream end to said downstream end.  
   
   
       28 . The device of  claim 1  wherein a length of said substrate is greater than 1.5 times a diameter of said substrate.  
   
   
       29 . The device of  claim 1  wherein said first group of channels has a washcoat and said second group of channels is impregnated with washcoat materials.  
   
   
       30 . The device of  claim 1  wherein said substrate is washcoated so as to render said substrate a LNT.  
   
   
       31 . The device of  claim 1  wherein said substrate is washcoated so as to render said substrate a TWC.  
   
   
       32 . The device of  claim 1  wherein said substrate is washcoated so as to render said substrate an oxidation catalyst.  
   
   
       33 . The device of  claim 1  wherein said channels are square in cross section and each of said first group of channels is adjacent to members of said second group of channels.  
   
   
       34 . The device of  claim 1  wherein said first group of channels comprises an outer ring of said substrate and said second group of channels comprises and inner portion of said substrate.