Composition and Method for Controlling Excessive Exhaust Gas Temperatures

Abstract

A method of operating an internal combustion engine having a reductant delivery and storage system in an emission control system is disclosed. The method includes an approach for reducing thermal damage to aftertreatment devices in an exhaust system by reducing excessive exhaust gas temperatures created during particulate filter regeneration.

1 - 17 . (canceled) 
     
     
         18 . A method for a vehicle exhaust system having an SCR catalyst, stored aqueous urea, and a soot filter, comprising:
 during a first filter regeneration condition: supplying the urea upstream of the soot filter, including increasing a supplied urea amount as a soot amount in the soot filter increases, in response to exhaust-system overtemperature; and   during a second filter regeneration condition: lowering an exhaust oxygen content in response to exhaust-system overtemperature without supplying the urea.   
     
     
         19 . The method of  claim 18 , wherein the exhaust-system overtemperture comprises an exhaust-system temperature exceeding a threshold value. 
     
     
         20 . The method of  claim 18 , wherein the exhaust-system overtemperature comprises an exhaust-system temperature exceeding a threshold rate of change. 
     
     
         21 . The method of  claim 18 , wherein the exhaust-system overtemperature comprises a temperature downstream of the soot filter exceeding a temperature upstream of the soot filter by a threshold amount. 
     
     
         22 . The method of  claim 18 , wherein lowering the oxygen content of the exhaust comprises throttling an intake airflow to an engine coupled to the exhaust system. 
     
     
         23 . The method of  claim 18 , wherein lowering the oxygen content of the exhaust comprises increasing exhaust-gas recirculation to an engine coupled to the exhaust system. 
     
     
         24 . The method of  claim 18 , wherein an amount of the stored urea is above a threshold amount during the first condition and below the threshold amount during the second condition. 
     
     
         25 . The method of  claim 18 , wherein the oxygen content of the exhaust is not lowered during the first condition. 
     
     
         26 . The method of  claim 18 , wherein supplying the urea upstream of the soot filter comprises decreasing the supplied urea amount as an amount of the stored urea decreases. 
     
     
         27 . The method of  claim 18 , wherein supplying the urea upstream of the soot filter comprises adjusting the amount of aqueous urea based on a concentration of the urea. 
     
     
         28 . The method of  claim 18 , wherein the exhaust system is a diesel-engine exhaust system and the soot filter is a DPF. 
     
     
         29 . A method for a vehicle exhaust system having an SCR catalyst, stored aqueous urea, and a DPF, comprising:
 during DPF regeneration:
 when the stored urea is available during exhaust-system overtemperature: 
   supplying the urea upstream of the soot filter, including increasing a supplied urea amount as a DPF stored soot amount increases; and
 when the stored urea is unavailable during exhaust-system overtemperature: 
   lowering an exhaust oxygen content without supplying the urea.   
     
     
         30 . The method of  claim 29 , wherein the exhaust-system overtemperture comprises an exhaust-system temperature exceeding a threshold value. 
     
     
         31 . The method of  claim 29 , wherein the exhaust-system overtemperature comprises an exhaust-system temperature exceeding a threshold rate of change. 
     
     
         32 . The method of  claim 29 , wherein the exhaust-system overtemperature comprises a temperature downstream of the soot filter exceeding a temperature upstream of the soot filter by a threshold amount. 
     
     
         33 . The method of  claim 29 , wherein lowering the oxygen content of the exhaust comprises throttling an intake airflow to an engine coupled to the exhaust system. 
     
     
         34 . The method of  claim 29 , wherein lowering the oxygen content of the exhaust comprises increasing exhaust-gas recirculation to an engine coupled to the exhaust system. 
     
     
         35 . The method of  claim 29 , wherein the oxygen content of the exhaust is not lowered during the first condition. 
     
     
         36 . The method of  claim 29 , wherein supplying the urea upstream of the soot filter comprises decreasing the supplied urea amount as an amount of the stored urea decreases. 
     
     
         37 . The method of  claim 29 , wherein supplying the urea upstream of the soot filter comprises adjusting the amount of aqueous urea based on a concentration of the urea. 
     
     
         38 . The method of  claim 29 , wherein the exhaust system is a diesel-engine exhaust system.