Method and system for removing ash within a particulate filter

Abstract

Methods and systems are provided for injecting water to reduce an ash load on a PF. In one example, a method may include injecting water from a reservoir to between a PF and a three-way catalyst in order to reduce an ash load.

1 . A method, comprising:
 injecting water from a reservoir to between a particulate filter and a three-way catalyst, the particulate filter located downstream of the three-way catalyst.   
     
     
         2 . The method of  claim 1 , wherein the injecting is responsive to an exhaust pressure signal between the three-way catalyst and the particulate filter being above a threshold pressure. 
     
     
         3 . The method of  claim 1 , wherein the injecting is responsive to a particulate filter temperature being above a threshold temperature. 
     
     
         4 . The method of  claim 1 , wherein the three-way catalyst comprises a porous substrate coated with one or more precious metals, the three-way catalyst configured to convert one or more emissions in exhaust gas flowing through the three-way catalyst, and wherein the particulate filter comprises a mesh structure with less precious metal coating, the particulate filter configured to trap soot in exhaust gas flowing through the particulate filter. 
     
     
         5 . The method of  claim 1 , wherein the injecting is responsive to an estimated ash load after a soot regeneration has been completed. 
     
     
         6 . The method of  claim 5 , wherein the estimated ash load is based on an exhaust pressure after the soot regeneration, and further comprising adjusting a water injection amount based on the estimated ash load. 
     
     
         7 . The method of  claim 5 , wherein the soot regeneration is performed responsive to an exhaust gas pressure between the three-way catalyst and the particulate filter being above a threshold exhaust gas pressure. 
     
     
         8 . A system, comprising:
 an engine with a plurality of cylinders;   an engine exhaust emission control device comprising a particulate filter positioned downstream of a three-way catalyst brick;   an exhaust gas pathway coupling an engine exhaust manifold to the engine exhaust emission control device;   an injector fluidically coupled to a water reservoir via a conduit, the injector fluidically coupled between the three-way catalyst brick and the particulate filter;   a pressure sensor coupled between the three-way catalyst brick and the particulate filter; and   a controller having computer readable instructions stored on non-transitory memory for:
 estimating an ash load in the particulate filter based on a pressure measured by the pressure sensor; and 
 injecting water via the injector responsive to the estimated ash load exceeding a threshold ash load. 
   
     
     
         9 . The system of  claim 8 , further comprising an EGR pathway coupled to the exhaust gas pathway upstream of the emission control device, and wherein the instructions further comprise instructions for adjusting an EGR flow rate responsive to the injection of water. 
     
     
         10 . The system of  claim 8 , wherein the three-way catalyst brick and the particulate filter are housed in a common housing of the emission control device and separated via an air gap, and wherein the common housing includes a boss positioned between the three-way catalyst brick and the particulate filter to accommodate the injector, the injector positioned to inject water into the air gap. 
     
     
         11 . The system of  claim 8 , wherein the water reservoir is coupled to one or more of a charge air cooler and an air conditioner, the water reservoir is replenished via condensate from one or more of the charge air cooler and the air conditioner. 
     
     
         12 . The system of  claim 8 , wherein the three-way catalyst brick and the particulate filter are housed in separate housings and fluidically coupled via the exhaust pathway, and wherein the injector is coupled to the exhaust pathway between the three-way catalyst brick and the particulate filter. 
     
     
         13 . The system of  claim 12 , wherein the estimated ash load is determined following completion of a regeneration of the particulate filter. 
     
     
         14 . A method of an engine, comprising:
 combusting fuel in the engine via spark ignition and directing exhaust gas from the engine to a particulate filter;   responsive to an exhaust gas pressure upstream of the particulate filter exceeding a first threshold pressure, regenerating the particulate filter to remove particulate matter stored on the particulate filter; and   responsive to the exhaust gas pressure upstream of the particulate filter exceeding a second threshold pressure following completion of the regeneration, injecting water between the particulate filter and a three-way catalyst upstream of the particulate filter to remove ash from the particulate filter.   
     
     
         15 . The method of  claim 14 , wherein the exhaust pressure is measured between the three-way catalyst and the particulate filter. 
     
     
         16 . The method of  claim 15 , wherein regenerating the particulate filter includes increasing an exhaust gas temperature to at least a threshold temperature for a predetermined duration, where the exhaust gas temperature and predetermined duration are determined based at least in part on a particulate matter load on the particulate filter. 
     
     
         17 . The method of  claim 16 , further comprising determining that the regeneration has reached completion when the exhaust gas temperature has been maintained at least at the threshold temperature for the predetermined duration. 
     
     
         18 . The method of  claim 16 , wherein the exhaust gas temperature is increased as a result of an increase in engine load. 
     
     
         19 . The method of  claim 14 , wherein the first threshold pressure is greater than the second threshold pressure. 
     
     
         20 . The method of  claim 14 , further comprising injecting water to between the three-way catalyst and the particulate filter when a particulate filter temperature exceeds a threshold particulate filter temperature.