Reductant decomposition and mixing system

Abstract

A selective catalytic reduction (SCR) system includes a mixer that has a plurality of blades spaced about a central tube. The mixer can be configured to receive a reductant and exhaust gas mixture. The SCR system also includes a closed-end tube that is downstream of the mixer and configured to receive the reductant and exhaust gas mixture from the mixer. The closed-end tube includes a closed end opposing an open end. The closed end is substantially perpendicular to an exhaust flow direction. The closed-end tube further includes a sidewall that extends between the open and closed end. The sidewall can include a plurality of perforations. The flange plate of the SCR system includes an annular disk that has a plurality of openings through which reductant and exhaust gas mixture received from the closed-end tube is flowable. The flange plate is coupled to and supports in place the closed-end tube.

What is claimed is: 
     
         1 . A selective catalytic reduction (SCR) system, comprising:
 a mixer comprising a plurality of blades spaced about a central tube, the mixer configured to receive a reductant and exhaust gas mixture;   a closed-end tube downstream of the mixer configured to receive the reductant and exhaust gas mixture from the mixer, the closed-end tube comprising a closed end opposing an open end, the closed end being substantially perpendicular to an exhaust flow direction, wherein the closed-end tube comprises a sidewall extending between the open and closed end, the sidewall comprising a plurality of perforations; and   a flange plate comprising an annular disk, the annular disk comprising a plurality of openings through which reductant and exhaust gas mixture received from the closed-end tube is flowable, wherein the flange plate is coupled to and supports in place the closed-end tube.   
     
     
         2 . The SCR system of  claim 1 , wherein the SCR system is one of an in-line system, end-to-end system, or end-to-side system. 
     
     
         3 . The SCR system of  claim 1 , further comprising a linear exhaust conduit extending between a reductant doser and an inlet of an SCR catalyst, wherein the mixer, closed-end tube, and flange plate are positioned within the linear exhaust conduit between the reductant doser and the inlet of the SCR catalyst. 
     
     
         4 . The SCR system of  claim 3 , wherein the linear exhaust conduit comprises a decomposition tube and an SCR catalyst housing, and wherein the mixer is positioned within the decomposition tube, at least a portion of the closed-end tube is positioned within the SCR catalyst housing, and the flange plate is positioned within the SCR catalyst housing. 
     
     
         5 . The SCR system of  claim 3 , wherein the mixer is a secondary mixer, the SCR system further comprising a primary mixer positioned within the linear exhaust conduit downstream of the reductant doser and upstream of the secondary mixer. 
     
     
         6 . The SCR system of  claim 1 , wherein the plurality of blades induces a vortical swirling exhaust gas flow pattern and the central tube induces a linear exhaust gas flow pattern within the exhaust gas vortical swirling flow pattern. 
     
     
         7 . The SCR system of  claim 1 , wherein the plurality of perforations of the closed-end tube induces a radially outwardly directed exhaust gas flow pattern. 
     
     
         8 . The SCR system of  claim 1 , wherein the plurality of openings of the flange plate induces a plurality of concentrated radially outer regions of exhaust gas. 
     
     
         9 . The SCR system of  claim 1 , wherein the SCR system is configured such that an entirety of exhaust gas passing through the mixer is received by the closed-end tube and passes through the plurality of perforations of the closed-end tube, and wherein the SCR system is configured such that an entirety of exhaust gas passing through the plurality of perforations of the closed-end tube passes through the plurality of openings of the flange plate. 
     
     
         10 . An exhaust gas mixer, comprising:
 an inner tube defining a central conduit;   an outer tube positioned about the inner tube in coaxial alignment with the inner tube; and   a plurality of blades coupled to and positioned between the inner and outer tubes.   
     
     
         11 . The exhaust gas mixer of  claim 10 , wherein a radius of the inner tube is equal to or more than half a radius of the outer tube. 
     
     
         12 . The exhaust gas mixer of  claim 10 , wherein each of the plurality of blades comprises a radially inner edge fixed to the inner ring and a radially outer edge fixed to the outer ring. 
     
     
         13 . The exhaust gas mixer of  claim 12 , wherein the radially inner edge and radially outer edge are non-parallel to a central axis of the inner tube. 
     
     
         14 . The exhaust gas mixer of  claim 13 , wherein the radially inner edge defines a first angle relative to the central axis and the radially outer edge defines a second angle relative to the central axis, and wherein the first and second angles are different. 
     
     
         15 . The exhaust gas mixer of  claim 14 , wherein the first angle is between about 30° and about 50°, and the second angle is between about 50° and about 70°. 
     
     
         16 . The exhaust gas mixer of  claim 10 , wherein each of the plurality of blades comprises a leading edge and a trailing edge, and wherein each of the plurality of blades is curved in a direction extending from the leading edge to the trailing edge. 
     
     
         17 . An exhaust tube for receiving an exhaust gas stream flowing in a flow direction, comprising:
 an open upstream end configured to receive the exhaust gas stream flowing in the flow direction;   a closed downstream end defining an exhaust impact surface substantially perpendicular to the flow direction, the exhaust impact surface redirecting the exhaust gas stream in a redirected direction substantially perpendicular to the flow direction; and   a sidewall extending between the open upstream and closed downstream ends, the sidewall comprising a plurality of perforations through which the redirected exhaust gas is flowable.   
     
     
         18 . The exhaust tube of  claim 17 , wherein the exhaust impact surface is convex. 
     
     
         19 . The exhaust tube of  claim 17 , wherein an entirety of the exhaust gas stream received by the exhaust tube flows through the plurality of perforations. 
     
     
         20 . The exhaust tube of  claim 17 , wherein the sidewall extends parallel to the flow direction, and wherein the redirected exhaust gas flows through the plurality of perforations in the redirected direction.