Mixing device for an exhaust system

Abstract

A mixing device for mixing a gas and a liquid in an exhaust system has an injector for injecting the liquid, a shell, an inlet, an outlet and an exhaust gas flow path between the inlet and the outlet. The mixing device defines an axis, and the flow path has a first part, a second part and a third part. The first part extends generally parallel to the axis to direct a flow in a generally forward direction, the first part extending up to a first axial position. The second part extends generally parallel to the axis to direct flow in a generally reverse direction. The third part extends generally parallel to the axis to direct a flow in the generally forward direction. The third part is a volume that allows mixing and extends past the first axial position.

1 . A mixing device for mixing a gas and a liquid in an exhaust system, said mixing device comprising:
 an injector for injecting a liquid, wherein said mixing device has a shell, an inlet, an outlet, and an exhaust gas flow path between said inlet and said outlet; and   wherein the mixing device defines an axis with said exhaust gas flow path having a first part, a second part, and a third part, said first part extending generally parallel to said axis to direct a flow in a generally forward direction, said first part extending up to a first axial position, said second part extending generally parallel to said axis to direct flow in a generally reverse direction, and said third part extending generally parallel to said axis to direct a flow in said generally forward direction wherein said third part is a volume that allows mixing and extends past said first axial position.   
   
   
       2 . The mixing device as defined in  claim 1  in which said exhaust gas flow path is substantially symmetrical about a center line of said mixing device. 
   
   
       3 . The mixing device as defined in  claim 1  in which said inlet is defined by a central tube at least partially positioned within said shell and the outlet is defined at least partially by said shell. 
   
   
       4 . The mixing device as defined in  claim 3  in which said central tube includes a blanked off tube end. 
   
   
       5 . The mixing device as defined in  claim 4  in which said central tube includes tube perforations proximate said blanked off tube end. 
   
   
       6 . The mixing device as defined in  claim 5  including a sleeve positioned within said shell and surrounding said tube perforations and being spaced from said tube perforations, said sleeve having a blanked off sleeve end proximate said blanked off tube end. 
   
   
       7 . The mixing device as defined in  claim 6  in which said sleeve includes sleeve perforations remote from said blanked off sleeve end. 
   
   
       8 . The mixing device as defined in  claim 6  in which said third part is in an annulus and said sleeve partially defines said annulus. 
   
   
       9 . The mixing device as defined in  claim 4  in which said blanked off tube end is supported by a baffle. 
   
   
       10 . The mixing device as defined in  claim 6  in which said blanked off sleeve end is supported by a baffle. 
   
   
       11 . The mixing device as defined in  claim 9  in which a portion of said baffle acts to blank off at least one of said blanked off tube end and/or said blanked off sleeve end. 
   
   
       12 . The mixing device as defined in  claim 3  in which said central tube is cylindrical. 
   
   
       13 . The mixing device as defined in  claim 6  in which said sleeve is cylindrical. 
   
   
       14 . The mixing device as defined in  claim 7  in which an open area of the tube perforations is approximately equal to an open area of the sleeve perforations. 
   
   
       15 . The mixing device as defined in  claim 7  in which at least one of an open area of said tube perforations and an open area of said sleeve perforations is greater than or equal to 1.5 times a cross section area of said inlet. 
   
   
       16 . The mixing device as defined in  claim 1  in which said cross section area of said third part is approximately equal to or greater than said cross section area of said first part, and/or said cross section area of said third part is approximately equal to said cross section area of said second part, and/or said cross section area of said second part is approximately equal to or greater than said cross sectional area of said first part. 
   
   
       17 . The mixing device as defined in  claim 7  in which said sleeve perforations do not axially overlap with said tube perforations. 
   
   
       18 . (canceled) 
   
   
       19 . The mixing device as defined in  claim 1  in which an outlet is defined by a central tube positioned within said shell and an inlet is defined by an annulus, said annulus being partially defined by said shell. 
   
   
       20 . The mixing device as defined in  claim 1 , in which the injector is positioned upstream of the mixing device, in particular to inject a reagent at the inlet of the mixing device. 
   
   
       21 . An exhaust system comprising:
 a mixing device including an injector for injecting a liquid, wherein said mixing device has a shell, an inlet, and an outlet, and an exhaust gas flow path between said inlet and said outlet and wherein said injector is positioned upstream of said mixing device to inject a reagent at said inlet;   wherein said mixing device defines an axis with said flow path having a first part, a second part, and a third part, said first part extending generally parallel to said axis to direct a flow in a generally forward direction, said first part extending up to a first axial position, said second part extending generally parallel to said axis to direct flow in a generally reverse direction, and said third part extending generally parallel to said axis to direct a flow in said generally forward direction wherein, said third part is a volume that allows mixing and extends past said first axial position; and   an integrated catalyst.   
   
   
       22 .- 143 . (canceled)