Particulate trap regeneration

Abstract

A particulate trap is regenerated with a valving mechanism downstream of the trap for periodically creating a reverse pressure of about 15 to 60 psig throughout the entire trap, a reversing apparatus operative after the reverse pressure is created for starting a regeneration cycle by creating a substantially instantaneous reverse pressure drop across the porous walls of the trap to dislodge accumulated particulate cake and by causing the filtered exhaust gas to flow back through the porous walls to remove the dislodged particulate from the trap, and controls for starting and stopping a regeneration cycle.

I claim: 
     
         1 . In a system for regenerating a particulate trap in an exhaust system of an internal combustion engine and including a wall-flow particulate trap having a plurality of porous walls for filtering engine exhaust and removing particulates therefrom to form a particulate cake on the porous walls, a valving mechanism downstream of said trap for periodically creating a reverse pressure throughout said entire trap, a reversing apparatus operative after the reverse pressure is created for periodically creating a substantially instantaneous reverse pressure drop across the porous walls of said trap to dislodge accumulated particulate cake and causing the filtered exhaust gas to flow back through the porous walls to remove the dislodged particulate from said trap, and controls for starting and stopping a regeneration cycle, the improvement comprising: the valving mechanism downstream of the trap is operative to increase the back pressure to a range from about 20 psig to about 35 psig which is within the limit of the exhaust valve operation. 
     
     
         2 . A system according to  claim 1 , further characterized in that the valving mechanism downstream of the trap is also operative as an exhaust brake. 
     
     
         3 . A system for regenerating a particulate trap as set forth in  claim 1  wherein the valving mechanism includes a relief valve having a first open position permitting flow of filtered exhaust to atmosphere and a second position restricting flow of the filtered exhaust until the pressure throughout the exhaust system reaches a pre-selected level. 
     
     
         4 . A system for regenerating a particulate trap as set forth in  claim 1  including a purge duct upstream of said trap for receiving the dislodged particulate from said trap, and wherein the reversing apparatus includes a valve associated with the purge duct. 
     
     
         5 . A system for regenerating a particulate trap as set forth in  claim 4  wherein the controls are operative for opening the purge duct valve to thereby drop the pressure at the inlet side of the filter and thereby create a pressure drop sufficient to dislodge portions of the cake. 
     
     
         6 . A particulate trap system according to  claim 1  wherein the controls are actuated following attainment of a pre-selected trap exhaust pressure drop during normal filtration operation of the engine. 
     
     
         7 . A particulate trap system according to  claim 1  wherein the wall-flow particulate trap has a porosity in the range of about 42 to 52%. 
     
     
         8 . A particulate trap regeneration system comprising:
 (a) a particulate trap in an exhaust system of an internal combustion engine, the trap having a plurality of porous walls for filtering engine exhaust and removing particulates therefrom to form a particulate cake on the porous walls;   (b) a valving mechanism downstream of the trap for periodically creating a reverse pressure of about 15 to 60 psig throughout the entire trap;   (c) a reversing apparatus operative after the reverse pressure is created for starting a regeneration cycle by creating a substantially instantaneous reverse pressure drop across the porous walls of the trap to dislodge accumulated particulate cake and by causing the filtered exhaust gas to flow back through the porous walls to remove the dislodged particulate from the trap; and   (d) controls for starting and stopping a regeneration cycle.   
     
     
         9 . The system of  claim 8  wherein the valving mechanism includes a relief valve having a first open position permitting flow of filtered exhaust to atmosphere and a second position restricting flow of the filtered exhaust until the pressure throughout the exhaust system reaches a pre-selected level. 
     
     
         10 . The system of  claim 9  additionally comprising a purge duct upstream of the trap for receiving the dislodged particulate from said trap, and wherein the reversing apparatus includes a purge duct valve, associated with the purge duct. 
     
     
         11 . The system of  claim 10  wherein the controls are operative for opening the purge duct valve to thereby drop the pressure at the inlet side of the filter and thereby create a pressure drop sufficient to dislodge portions of the cake. 
     
     
         12 . A method of regenerating a particulate trap in an exhaust system of an internal combustion engine, comprising the steps of: creating a back pressure throughout the entire exhaust system from a location downstream of the trap to a level of at least about 20 psig; releasing the back pressure at a location upstream of the trap to create a pressure drop across the entire trap and reverse flow through the entire trap sufficient to remove particulate matter stored in the trap; collecting the released particulate matter; and thereafter resuming normal filtration. 
     
     
         13 . The method of  claim 12  wherein the back pressure created is about 20 to 35 psig. 
     
     
         14 . The method of  claim 12  wherein the back pressure is released to create a substantially instantaneous pressure drop across the entire trap. 
     
     
         15 . The method of  claim 14  wherein the back pressure is released by opening a purge duct valve. 
     
     
         16 . The method of  claim 15  wherein the back pressure is created with an exhaust brake.