System and method for controlling an exhaust system having a selective catalyst reduction component

Abstract

A method for controlling operation of an SCR component includes receiving a signal reflecting a sensed condition of an exhaust stream associated with the SCR component, estimating an apparent aging time of the SCR component based on the sensed condition of the exhaust stream, and setting an operating condition of the SCR component based on the apparent aging time of the SCR component.

What is claimed is: 
     
         1 . A method for controlling operation of an SCR component comprising:
 receiving a signal reflecting a sensed condition of an exhaust stream associated with the SCR component;   estimating an apparent aging time of the SCR component based on the sensed condition of the exhaust stream; and   setting an operating condition of the SCR component based on the apparent aging time of the SCR component.   
     
     
         2 . A method as described in  claim 1 , wherein said receiving a signal reflecting a sensed condition of an exhaust stream associated with the SCR component comprises receiving a signal reflecting a sensed NOx content of the exhaust stream. 
     
     
         3 . A method as described in  claim 1 , wherein said receiving a signal reflecting a sensed condition of an exhaust stream associated with the SCR component comprises receiving a signal reflecting a sensed NH3 content of the exhaust stream. 
     
     
         4 . A method as described in  claim 1 , wherein said receiving a signal reflecting a condition of an exhaust stream associated with the SCR component comprises receiving a signal reflecting a sensed condition of the exhaust stream downstream from the SCR component. 
     
     
         5 . A method as described in  claim 1 , wherein said estimating an apparent aging time of the SCR component comprises:
 setting a model input SCR aging time;   executing an SCR reaction model comprising:   determining a predicted SCR reaction efficiency based on the model input SCR aging time; and   determining a predicted condition of the exhaust stream based on the predicted SCR reaction efficiency;   adjusting the model input SCR aging time and subsequently executing the SCR reaction model until the predicted condition of the exhaust stream is within a predetermined tolerance of the sensed condition of the exhaust stream; and   setting an apparent SCR aging time equal to the model input SCR aging time when the predicted condition of the exhaust stream is within the predetermined tolerance of the sensed condition of the exhaust stream.   
     
     
         6 . A method as described in  claim 5 , wherein said sensed condition of the exhaust stream comprises a sensed NOx content of the exhaust stream. 
     
     
         7 . A method as described in  claim 5 , wherein said sensed condition of the exhaust stream comprises a sensed NH3 content of the exhaust stream. 
     
     
         8 . A method as described in  claim 5 , wherein said sensed condition of the exhaust stream comprises a sensed condition downstream from the SCR component. 
     
     
         9 . A method as described in  claim 5 , wherein said determining a predicted SCR reaction efficiency comprises interpolating one or more empirical data tables representing an efficiency of an SCR reaction as a function of SCR aging time. 
     
     
         10 . A method as described in  claim 5 , wherein said determining a predicted SCR reaction efficiency comprises evaluating one or more polynomial expressions characterizing reaction efficiency as a function of SCR aging time. 
     
     
         11 . A system for controlling operation of an SCR component comprising:
 a selective catalyst reduction (SCR) component diagnostic module that is configured for receiving a signal reflecting a sensed condition of an exhaust stream associated with the SCR component and for estimating an apparent aging time of the SCR component based on the sensed condition of the exhaust stream; and   an SCR component management module that is configured for selectively adjusting an operating condition of the SCR component based on the apparent aging time of the SCR component.   
     
     
         12 . A system as described in  claim 11 , wherein said selective catalyst reduction (SCR) component diagnostic module is configured for receiving a signal reflecting a sensed NOx content of the exhaust stream. 
     
     
         13 . A system as described in  claim 11 , wherein said selective catalyst reduction (SCR) component diagnostic module is configured for receiving a signal reflecting a sensed NH3 content of the exhaust stream. 
     
     
         14 . A system as described in  claim 11 , wherein said selective catalyst reduction (SCR) component diagnostic module is configured for receiving a signal reflecting a sensed condition of the exhaust stream downstream from the SCR component. 
     
     
         15 . A system as described in  claim 11 , wherein said selective catalyst reduction (SCR) component diagnostic module is configured for:
 setting a model input SCR aging time;   executing an SCR reaction model comprising:   determining a predicted SCR reaction efficiency based on the model input SCR aging time; and   determining a predicted condition of the exhaust stream based on the predicted SCR reaction efficiency;   adjusting the model input SCR aging time and subsequently executing the SCR reaction model until the predicted condition of the exhaust stream is within a predetermined tolerance of the sensed condition of the exhaust stream; and   setting an apparent SCR aging time equal to the model input SCR aging time when the predicted condition of the exhaust stream is within the predetermined tolerance of the sensed condition of the exhaust stream.   
     
     
         16 . A system as described in  claim 15 , wherein said selective catalyst reduction (SCR) component diagnostic module is configured for receiving a signal reflecting a sensed NOx content of the exhaust stream. 
     
     
         17 . A system as described in  claim 15 , wherein said selective catalyst reduction (SCR) component diagnostic module is configured for receiving a signal reflecting a sensed NH3 content of the exhaust stream. 
     
     
         18 . A system as described in  claim 15 , wherein said selective catalyst reduction (SCR) component diagnostic module is configured for receiving a signal reflecting a sensed condition of the exhaust stream downstream from the SCR component. 
     
     
         19 . A system as described in  claim 15 , wherein said selective catalyst reduction (SCR) component diagnostic module is configured for interpolating one or more empirical data tables representing an efficiency of an SCR reaction as a function of SCR aging time. 
     
     
         20 . A system as described in  claim 15 , wherein said selective catalyst reduction (SCR) component diagnostic module is configured for evaluating one or more polynomial expressions characterizing reaction efficiency as a function of SCR aging time.