Systems and methods for monitoring the health of a mid-bed oxidant injection system

Abstract

A system includes a controller programmed to determine an oxidation state of a three-way catalyst (TWC) assembly based on a first signal representative of a measured oxygen (O 2 ) storage of the TWC assembly received from a radio frequency (RF) probe disposed within the TWC assembly, to determine whether a temperature of a fluid flowing into an ammonia slip catalyst (ASC) assembly is within a desired temperature operating range based on a second signal representative of the temperature of the fluid adjacent an inlet of the ASC assembly, to determine whether a concentration of nitrogen oxides (NO X ) in the fluid exiting an outlet of the ASC assembly is within desired limits based on a third signal representative of the concentration of NO X in the fluid, and to determine whether to perform diagnostics on a component of an exhaust aftertreatment system based at least on the first, second, and third signals.

1 . A system, comprising:
 an exhaust aftertreatment system configured to treat emissions from a combustion engine, wherein the exhaust aftertreatment system comprises:
 a three-way catalyst (TWC) assembly having a first outlet; 
 an ammonia slip catalyst (ASC) assembly configured to receive a fluid from the TWC assembly, wherein the ASC assembly has an inlet and a second outlet; 
 a fluid conduit disposed between the TWC assembly and the ASC assembly and configured to transfer the fluid from the TWC assembly to the ASC assembly; 
 an oxidant injection system coupled to the fluid conduit and configured to inject oxidant into the fluid conduit upstream of the inlet of the ASC assembly to provide sufficient oxidant in the fluid flowing into the inlet of the ASC assembly to enable catalytic activity in the ASC assembly; 
 a first radiofrequency (RF) probe disposed within the TWC assembly and configured to measure oxygen (O 2 ) storage of the TWC assembly; 
 at least one temperature sensor disposed downstream of a location of oxidant injection into the fluid conduit by the oxidant injection system and upstream of the inlet of the ASC assembly, wherein the at least one temperature sensor is configured to measure a temperature of the fluid adjacent the inlet of the ASC assembly; 
 at least one nitrogen oxides (NO X ) sensor disposed downstream of the inlet of the ASC assembly and configured to measure a concentration of NO X  in the fluid exiting the outlet of the ASC assembly; and 
 a controller programmed to receive a first signal representative of a measured O 2  storage of the TWC assembly from the first RF probe, to receive a second signal representative of the temperature of the fluid adjacent the inlet of the ASC assembly, to receive a third signal representative of the concentration of NO X  in the fluid exiting the ASC assembly, and to determine whether to perform diagnostics on a component of the exhaust aftertreatment system based at least on the first, second, and third signals. 
   
     
     
         2 . The system of  claim 1 , wherein the controller is programmed to determine an oxidation state of the TWC assembly based on the measured O 2  storage. 
     
     
         3 . The system of  claim 2 , wherein the controller is programmed to determine whether the measured O 2  storage is approximately zero. 
     
     
         4 . The system of  claim 3 , wherein the controller is programmed to decrease an air to fuel ratio the combustion engine is operating at if the measured O 2  storage is greater than zero. 
     
     
         5 . The system of  claim 3 , wherein the controller is programmed to determine whether the temperature of the fluid flowing into the ASC assembly is within a desired temperature operating range if the measured O 2  storage is approximately zero. 
     
     
         6 . The system of  claim 5 , wherein the controller is programmed to control the oxidant injection system to inject oxidant or additional oxidant into fluid conduit to adjust the temperature of the fluid flowing into the ASC assembly so that the temperature is within the desired temperature operating range if the temperature of the fluid flowing into the ASC assembly is not within the desired temperature operating range. 
     
     
         7 . The system of  claim 5 , wherein the controller is programmed to determine whether the concentration of NO X  in the fluid exiting the outlet of the ASC assembly is within desired limits if the temperature of the fluid flowing into the ASC assembly is within the desired temperature operating range. 
     
     
         8 . The system of  claim 7 , wherein the controller is programmed to perform diagnostics on the component of the exhaust aftertreatment system if the concentration of NO X  in the fluid exiting the outlet of the ASC assembly is not within desired limits. 
     
     
         9 . The system of  claim 8 , comprising a second RF probe disposed within the ASC assembly and configured to measure a concentration of ammonia (NH 3 ) in the fluid within the ASC assembly. 
     
     
         10 . The system of  claim 9 , wherein the controller is programmed to receive a fourth signal representative of the concentration of NH 3  in the fluid within the ASC assembly, and to determine if the concentration of NH 3  is equal to a reference value. 
     
     
         11 . The system of  claim 10 , wherein the controller is programmed to perform diagnostics on the ASC assembly if the concentration of NH 3  is not equal to the reference value. 
     
     
         12 . The system of  claim 11 , wherein the controller is programmed to perform diagnostics on the at least one NO X  sensor if the concentration of NH 3  is equal to the reference value. 
     
     
         13 . The system of  claim 1 , comprising the combustion engine coupled to the exhaust aftertreatment system. 
     
     
         14 . A system, comprising:
 a controller programmed to determine an operational state of an exhaust aftertreatment system coupled to a combustion engine, wherein the exhaust aftertreatment system comprises a three-way catalyst (TWC) assembly fluidly coupled to an ammonia slip catalyst (ASC) assembly located downstream of the TWC assembly, and wherein the controller is programmed to determine an oxidation state of the TWC assembly of the exhaust aftertreatment system based on a first signal representative of a measured oxygen (O 2 ) storage of the TWC assembly received from a first radio frequency (RF) probe disposed within the TWC assembly, to determine whether a temperature of a fluid flowing into the ASC assembly is within a desired temperature operating range based on a second signal representative of the temperature of the fluid adjacent an inlet of the ASC assembly received from a temperature sensor, to determine whether a concentration of NO X  in the fluid exiting an outlet of the ASC assembly is within desired limits based on a third signal representative of the concentration of nitrogen oxides (NO X ) in the fluid exiting the ASC assembly received from a NO X  sensor, and to determine whether to perform diagnostics on a component of the exhaust aftertreatment system based at least on the first, second, and third signals.   
     
     
         15 . The system of  claim 14 , wherein the controller is programmed to determine whether the temperature of the fluid flowing into the ASC assembly is within the desired temperature operating range if the measured O 2  storage is approximately zero. 
     
     
         16 . The system of  claim 15 , wherein the controller is programmed to determine whether the concentration of NO X  in the fluid exiting the outlet of the ASC assembly is within desired limits if the temperature of the fluid flowing into the ASC assembly is within the desired temperature operating range. 
     
     
         17 . The system of  claim 16 , wherein the controller is programmed to perform diagnostics on the component of the exhaust aftertreatment system if the concentration of NO X  in the fluid exiting the outlet of the ASC assembly is not within desired limits. 
     
     
         18 . The system of  claim 17 , wherein the controller is programmed to determine if a concentration of ammonia (NH 3 ) in the fluid within the ASC assembly is equal to a reference value based on a fourth signal representative of the concentration of NH 3  in the fluid within the ASC assembly received from a second RF probe disposed within the ASC assembly. 
     
     
         19 . The system of  claim 18 , wherein the controller is programmed to perform diagnostics on the ASC assembly if the concentration of NH 3  is not equal to the reference value, and to perform diagnostics on the NO X  sensor if the concentration of NH 3  is equal to the reference value. 
     
     
         20 . A method for monitoring an operational state of an exhaust aftertreatment system coupled to a combustion engine, wherein the exhaust aftertreatment system comprises a three-way catalyst (TWC) assembly fluidly coupled to an ammonia slip catalyst (ASC) assembly located downstream of the TWC assembly, comprising:
 receiving, at a controller, a first signal representative of a measured oxygen (O 2 ) storage of the TWC assembly from a first radio frequency (RF) probe disposed within the TWC assembly;   receiving, at the controller, a second signal representative of a temperature of a fluid flowing into an inlet of the ASC assembly from a temperature sensor;   receiving, at the controller, a third signal representative of a concentration of nitrogen oxides (NO X ) in the fluid exiting the ASC assembly from a NO X  sensor;   determining, via the controller, whether to perform diagnostics on a component of the exhaust aftertreatment system based at least on the first, second, and third signals; and   receiving, at the controller, a fourth signal representative of a concentration of ammonia (NH 3 ) in the fluid within the ASC assembly; and   if the controller determines to perform diagnostics on the component, determining, via the controller, the component of the exhaust aftertreatment system to perform diagnostics on based on the fourth signal.