Premixer conduit for exhaust aftertreatment system

Abstract

An exhaust aftertreatment system is disclosed. The exhaust aftertreatment system includes a premixer conduit that defines an exhaust flow path, a baffle disposed in the exhaust flow path, and a reductant injector in fluid communication with the exhaust flow path. The baffle is positioned in the premixer conduit, which includes a premixer inlet, a transition section, and a premixer outlet. The transition section is disposed between the premixer inlet and the premixer outlet. The premixer inlet is in fluid communication with the engine. The reductant injector is positioned downstream of the baffle and upstream of the premixer outlet.

What is claimed is: 
     
         1 . An exhaust aftertreatment system for an engine, comprising:
 a premixer conduit having an internal surface defining an exhaust flow path therein, the premixer conduit having a premixer inlet in fluid communication with the engine and a premixer outlet opposite the premixer inlet along a flow direction of the exhaust gases, the premixer outlet of the premixer conduit being in fluid communication with a selective catalytic reduction catalyst;   a baffle disposed in the exhaust flow path, the baffle and the internal surface of the premixer conduit defining an annular flow path therebetween;   a reductant injector disposed downstream of the baffle and upstream of the premixer outlet of the premixer conduit along a flow direction of the exhaust gases, the reductant injector being in fluid communication with the exhaust flow path and a reductant source, wherein an upstream radial dimension of the baffle is smaller than a downstream radial dimension of the baffle, the upstream radial dimension and the downstream radial dimension each defined transverse to a respective local flow direction of the exhaust gases, and wherein a ratio of a radial dimension of the exhaust flow path at the premixer inlet of the premixer conduit and a radial dimension of the exhaust flow path at the premixer outlet of the premixer conduit is not less than 0.5 and not greater than 1.0.   
     
     
         2 . The exhaust aftertreatment system of  claim 1 , wherein the premixer conduit includes a transition section disposed between the premixer inlet  200  of the conduit and the premixer outlet of the premixer conduit, an upstream radial dimension of the transition section being smaller than a downstream radial dimension of the transition section. 
     
     
         3 . The exhaust aftertreatment system of  claim 2 , wherein the baffle is disposed downstream of the transition section along the flow direction of the exhaust gases. 
     
     
         4 . The exhaust aftertreatment system of  claim 2 , wherein the baffle is disposed within the transition section along the flow direction of the exhaust gases. 
     
     
         5 . The exhaust aftertreatment system of  claim 2 , wherein the transition section includes a frustoconical surface extending from the upstream radial dimension of the transition section to the downstream radial dimension of the transition section. 
     
     
         6 . The exhaust aftertreatment system of  claim 2 , wherein the transition section includes a radial step along the flow direction of the exhaust gases. 
     
     
         7 . The exhaust aftertreatment system of  claim 1 , wherein the reductant injector is disposed a first distance away from a downstream face of the baffle, and a ratio of the first distance to the downstream radial dimension of the baffle ranges from about 0.2 to about 0.7. 
     
     
         8 . The exhaust aftertreatment system of  claim 1 , wherein a ratio of the flow area of the annular flow path to a flow area of the exhaust flow path at the reductant injector ranges from about 0.3 to 1.0. 
     
     
         9 . The exhaust aftertreatment system of  claim 1 , wherein a longitudinal axis of the reductant injector is substantially perpendicular to the flow direction of the exhaust gases at the reductant injector. 
     
     
         10 . The exhaust aftertreatment system of  claim 1 , wherein the premixer conduit further includes an elbow disposed upstream of the baffle along the flow direction of the exhaust gases. 
     
     
         11 . The exhaust aftertreatment system of  claim 2 , wherein the premixer conduit further includes an elbow disposed upstream of the transition section along the flow direction of the exhaust gases.