Diesel aftertreatment systems

Abstract

A method for controlling a temperature of a heated element of a reductant delivery system for a lean exhaust gas aftertreatment device coupled downstream of an internal combustion engine is presented. The method teaches achieving a desired temperature of a heating element by selecting a control signal to the heating element from a predetermined temperature map based on engine operating conditions, such as exhaust gas temperature, engine speed, load, etc. Therefore, durability of the heating element and its power consumption are improved by, for example, controlling its temperature to prevent overheating, and having the ability to turn the heating element off when the exhaust gas temperatures are sufficiently high.

1 . A reductant delivery system, comprising: 
 an evaporator unit including at least a heating device;    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, said controller adjusting a temperature of said heating device to evaporate said mixture.    
     
     
         2 . The system as set forth in  claim 1  wherein said reductant is urea.  
     
     
         3 . The system as set forth in  claim 1  wherein said reductant is hydrocarbon.  
     
     
         4 . The system as set forth in  claim 1  wherein said reductant delivery system further comprises a container for housing said injected reductant and air mixture, wherein said reductant and air mixture evaporates inside said container without coming in direct contact with a surface of said heating element.  
     
     
         5 . The system as set forth in  claim 1  wherein said heating device is an electrically heated elongated heater plug.  
     
     
         6 . The system as set forth in  claim 5  wherein said heater plug is cylindrically shaped.  
     
     
         7 . The system as set forth in  claim 5  wherein said heater plug is rectangular in shape.  
     
     
         8 . The system as set forth in  claim 2  wherein said evaporator unit further comprises a hydrolyzing catalyst.  
     
     
         9 . The system as set forth in  claim 3  wherein said evaporator unit further comprises an oxidation catalyst.  
     
     
         10 . The system as set forth in  claim 1  wherein said controller supplies a pulse-width modulated signal of a predetermined duty cycle to adjust said heating device temperature.  
     
     
         11 . The system as set forth in  claim 10  wherein said controller turns off power to said heating device when said heating device temperature is above a predetermined temperature.  
     
     
         12 . A method for controlling a temperature of a heating element of a reductant delivery system for an exhaust gas aftertreatment device, the device coupled downstream of an internal combustion engine, the method comprising: 
 estimating operating conditions; and    adjusting the temperature of the heating element based on said operating conditions.    
     
     
         13 . The method as set forth in  claim 12  wherein said operating conditions are engine operating conditions.  
     
     
         14 . The method as set forth in  claim 12  wherein said engine operating conditions comprise at least engine speed.  
     
     
         15 . The method as set forth in  claim 12  wherein said operating conditions comprise at least an exhaust gas mixture temperature.  
     
     
         16 . The method as set forth in  claim 12  wherein said operating conditions comprise at least engine load.  
     
     
         17 . The method as set forth in  claim 12  wherein said engine is a diesel engine.  
     
     
         18 . The method as set forth in  claim 17  wherein the exhaust gas aftertreatment device is an ALNC.  
     
     
         19 . The method as set forth in  claim 17  wherein the exhaust gas aftertreatment device is an SCR catalyst.  
     
     
         20 . A method for operating a reductant delivery system for an exhaust gas aftertreatment device, the system including at least a heating element, the method comprising: 
 operating in a first mode where a reductant and air mixture is injected into the reductant delivery system and the heating element is turned on; and    operating in a second mode where said reductant and air mixture is injected into the reductant delivery system, and the heating element is turned off.    
     
     
         21 . The method as set forth in  claim 20  wherein said reductant is urea.  
     
     
         22 . The method as set forth in  claim 21  wherein the exhaust gas aftertreatment device is an SCR catalyst.  
     
     
         23 . The method as set forth in  claim 20  wherein said reductant is hydrocarbon.  
     
     
         24 . The method as set forth in  claim 23  wherein the exhaust gas aftertreatment device is an ALNC.  
     
     
         25 . The method as set forth in  claim 20  wherein the heating element is turned off when a temperature of the exhaust gas aftertreatment device is above a predetermined threshold.  
     
     
         26 . A method for controlling a reductant delivery system for an exhaust gas aftertreatment device coupled downstream of an internal combustion engine exhaust, comprising: 
 injecting a mixture of reductant and air into the reductant delivery system;    adjusting a temperature of a heating element housed inside the reductant delivery system thereby causing said mixture to evaporate; and    introducing said evaporated mixture into the exhaust gas aftertreatment device.    
     
     
         27 . The method as set forth in  claim 26  wherein the engine is a diesel engine.  
     
     
         28 . The method as set forth in  claim 27  wherein the exhaust gas aftertreatment device is an ALNC.  
     
     
         29 . The method as set forth in  claim 28  wherein said mixture of reductant and air is a mixture of hydrocarbon and air.  
     
     
         30 . The method as set forth in  claim 27  wherein the exhaust gas aftertreatment device is an SCR catalyst.  
     
     
         31 . The method as set forth in  claim 30  wherein said mixture of reductant and air is a mixture of urea and air.  
     
     
         32 . A method for operating a reductant delivery system for an exhaust gas aftertreatment device coupled downstream of an internal combustion engine, the system including at least a heating element, the method comprising: 
 operating the system in a first mode by injecting a reductant and air mixture into the system and adjusting a temperature of said heating element to evaporate said reductant and air mixture; and    operating the system in a second mode by injecting said reductant and air mixture into the system, and adjusting said temperature of said heating element to combust said reductant and air mixture.