Diesel aftertreatment systems

Abstract

A method and a system for improved reductant delivery to an exhaust gas aftertreatment device for a lean burn internal combustion engine exhaust is presented. The system includes a heated evaporator unit into which a mixture of reductant and air in injected, wherein the mixture is vaporized and introduced into the exhaust gas aftertreatment device. Introducing the reductant mixed with air into the heated evaporator unit prevents lacquering and soot deposits on the heated element housed inside the unit, and also speeds up the vaporization process due to better reductant distribution thus reducing system response delays and improving conversion efficiency of the exhaust gas aftertreatment device. The reductant delivery system is further improved by adding a catalyst to it, and by preventing the reductant and air mixture from coming into direct contact with the surface of the heating element.

1 . A reductant delivery system, comprising: 
 an evaporator unit including at least a heating element;    a mixing device having at least one inlet and at least one outlet coupled to said evaporator unit; and    a controller for introducing reductant and air into said mixing device through said inlet, injecting a mixture of said reductant and said air through said outlet into said evaporator unit thereby causing evaporation of said reductant and air mixture.    
     
     
         2 . The system as set forth in  claim 1  wherein said reductant is hydrocarbon.  
     
     
         3 . The system as set forth in  claim 1  further comprising a delivery tube for housing said injected reductant and air mixture, wherein said reductant and air mixture evaporates inside said delivery tube without coming into direct contact with a surface of said heating element.  
     
     
         4 . The system as set forth in  claim 1  wherein said heating element is an electrically heated elongated heater plug.  
     
     
         5 . The system as set forth in  claim 4  wherein said heater plug is cylindrically shaped.  
     
     
         6 . The system as set forth in  claim 4  wherein said heater plug is rectangular shaped.  
     
     
         7 . The system as set forth in  claim 1  wherein said evaporator unit further comprises an oxidation catalyst.  
     
     
         8 . The system as set forth in  claim 1  wherein said mixing device outlet is configured to inject said mixture of said reductant and said air onto at least two predetermined areas on a surface of said heating element.  
     
     
         9 . The system as set forth in  claim 8  wherein said controller is further adapted to enable and disable injection of said mixture of said reductant and said air onto said predetermined areas of said heating device.  
     
     
         10 . A method for vaporizing a substance in a reductant delivery system for an exhaust gas aftertreatment device, the system having at least a heating element, the method comprising: 
 generating a mixture by mixing a predetermined amount of reductant with a predetermined amount of air; and    injecting said mixture into the reductant delivery system thereby causing said mixture to vaporize.    
     
     
         11 . The method as set forth in  claim 10  wherein said reductant is hydrocarbon.  
     
     
         12 . The method as set forth in  claim 10  wherein the exhaust gas aftertreatment device is an Active Lean NOx Catalyst (ALNC).  
     
     
         13 . The method as set forth in  claim 12  further comprising directing said vaporized mixture into said ALNC.  
     
     
         14 . A method for controlling a reductant delivery system having at least a heating element, the system coupled upstream of an exhaust gas aftertreatment device of an internal combustion engine in a mobile vehicle, the method comprising: 
 injecting air into the system;    injecting a reductant into the system thereby creating a vaporized mixture; and    directing said vaporized mixture into the exhaust gas aftertreatment device.    
     
     
         15 . The method as set forth in  claim 14  wherein said reductant is hydrocarbon.  
     
     
         16 . The method as said forth in  claim 14  wherein the engine is a diesel engine.  
     
     
         17 . The method as set forth in  claim 14  wherein the exhaust gas aftertreatment device is an ALNC.