Method and apparatus for exhaust aftertreatment in a spark-ignition direct-injection internal combustion engine

Abstract

The disclosure sets forth a spark-ignition, direct-fuel injection internal combustion engine selectively operative at an air/fuel ratio lean of stoichiometry and fluidly connected to an exhaust aftertreatment system. The exhaust aftertreatment system consists essentially of an electro-thermal heating element adjoining a converter element. A control system comprising a control module is signally connected to a sensing device and adapted to monitor a temperature of the converter element and operatively connected to the engine and operative to connect the electro-thermal heating element to an electric power source.

1 . Apparatus, comprising:
 a spark-ignition, direct-injection internal combustion engine selectively operative at an air/fuel ratio lean of stoichiometry and directly fluidly connected to an exhaust aftertreatment system;   the exhaust aftertreatment system consisting essentially of an electro-thermal heating element adjoining a converter element wherein no other exhaust aftertreatment devices are disposed between the engine and the exhaust aftertreatment system; and   a control system comprising a control module signally connected to a sensing device adapted to monitor a temperature of the converter element and operatively connected to the engine and operative to connect the electro-thermal heating element to an electric power source.   
     
     
         2 . The apparatus of  claim 1 , comprising the exhaust aftertreatment system located at a distance from the engine such that a temperature of the exhaust gas feedstream entering the converter element is less than 750° C. during normal engine operation. 
     
     
         3 . The apparatus of  claim 2 , further comprising the converter element located at a distance at least 0.7 meters from an exhaust valve of the internal combustion engine. 
     
     
         4 . The apparatus of  claim 1 , wherein the converter element comprises a ceramic substrate having a washcoat containing at least one of a metal consisting of platinum, palladium, and rhodium and an alkali and/or alkali earth metal compound consisting of one of barium and potassium. 
     
     
         5 . The apparatus of  claim 1 , comprising the control module operative to control a current control device to connect the electro-thermal heating element to the electric power source when the signal output from the sensing device indicates the temperature of the converter element is less than a predetermined threshold. 
     
     
         6 . The apparatus of  claim 5 , further comprising the control module operative to selectively control the internal combustion engine at an air/fuel ratio rich of a stoichiometric air/fuel ratio and operative to connect the electro-thermal heating element to the electric power source to control the temperature of the exhaust gas feedstream entering the converter element to about 700° C. for a predetermined period of time to desulfate the converter element. 
     
     
         7 . The apparatus of  claim 5 , further comprising the control module operative to selectively connect the electro-thermal heating element to the electric power source when the engine is shutdown during ongoing vehicle operation. 
     
     
         8 . The apparatus of  claim 1 , further comprising the control module operative to selectively control the internal combustion engine at a stoichiometric air/fuel ratio for a period of time determined to substantially desorb the adsorbed NOx from the converter element. 
     
     
         9 . The apparatus of  claim 1 , wherein the electro-thermal heating element comprises a metal-foil substrate having a washcoat chemically deposited onto the surface thereof. 
     
     
         10 . The apparatus of  claim 9 , wherein the washcoat includes catalytically active material. 
     
     
         11 . Apparatus, comprising
 a spark-ignition, direct-injection internal combustion engine selectively operative at an air/fuel ratio lean of stoichiometry and directly fluidly connected to an exhaust aftertreatment system;   the exhaust aftertreatment system consisting essentially of an electro-thermal heating element adjoining a catalyzed NOx adsorber device wherein no other exhaust aftertreatment devices are disposed between the engine and the exhaust aftertreatment system; and   a control system comprising a control module signally connected to a sensing device adapted to monitor a temperature of the converter element and operatively connected to the engine and operative to connect the electro-thermal heating element to an electric power source.   
     
     
         12 . The apparatus of  claim 11 , wherein the catalyzed NOx adsorber device comprises a monolithic substrate having a washcoat containing at least one of a metal consisting of platinum, palladium, and rhodium and containing an alkali metal compound consisting of one of barium and potassium. 
     
     
         13 . The apparatus of  claim 11 , further comprising the control module operative to selectively control the internal combustion engine at a stoichiometric air/fuel ratio for a period of time determined based upon desorption of adsorbed NOx from the converter element. 
     
     
         14 . Apparatus, comprising:
 a spark-ignition, direct-fuel injection internal combustion engine selectively operative at an air/fuel ratio lean of stoichiometry and directly fluidly connected to an exhaust aftertreatment system;   the exhaust aftertreatment system consisting essentially of an electro-thermal heating element adjoining a particulate filter NOx reduction catalyst wherein no other exhaust aftertreatment devices are disposed between the engine and the exhaust aftertreatment system; and   a control system comprising a control module signally connected to a sensing device adapted to monitor a temperature of the converter element and operatively connected to the engine and operative to connect the electro-thermal heating element to an electric power source.   
     
     
         15 . The apparatus of  claim 14 , further comprising the control module operative to selectively control the internal combustion engine at an air/fuel ratio rich of a stoichiometric air/fuel ratio and operative to connect the electro-thermal heating element to the electric power source to control the temperature of the exhaust gas feedstream entering the converter element to about 700° C. for a period of time determined to purge carbon from the converter element. 
     
     
         16 . Apparatus, comprising
 a spark-ignition, direct-injection internal combustion engine selectively operative at an air/fuel ratio lean of stoichiometry and directly fluidly connected to an exhaust aftertreatment system;   the exhaust aftertreatment system consisting essentially of an electro-thermal heating element adjoining a converter element and a selective catalytic reduction element wherein no other exhaust aftertreatment devices are disposed between the engine and the exhaust aftertreatment system; and   a control system comprising a control module signally connected to a sensing device adapted to monitor a temperature of the converter element and operatively connected to the engine and operative to connect the electro-thermal heating element to an electric power source.   
     
     
         17 . The apparatus of  claim 16 , comprising the exhaust aftertreatment system located at a distance from the engine such that a temperature of the exhaust gas feedstream entering the converter element is less than 750° C. during normal engine operation. 
     
     
         18 . The apparatus of  claim 17 , wherein the converter element comprises one of a particulate filter NOx reduction catalyst and a catalyzed NOx adsorber device. 
     
     
         19 . The apparatus of  claim 17 , wherein the selective catalytic reduction element comprises a substrate having zeolite and one of copper and iron coated thereon. 
     
     
         20 . The apparatus of  claim 19 , wherein the control system further comprises a sensing device operative to monitor the exhaust gas feedstream downstream of the exhaust aftertreatment system.