Engine exhaust after-treatment system and method

Abstract

Soot in engine exhaust gas is separated in a cyclonic filter and burned inside the cyclonic filter. An acoustic agglomerator has increased soot density in the engine exhaust gas before entering the cyclonic filter.

What is claimed is: 
     
         1 . An internal combustion engine comprising an after-treatment system for treating exhaust gas coming from engine combustion chambers before passing into surrounding atmosphere, wherein the after-treatment system comprises:
 a cyclonic filter for separating unburned particulate matter out of exhaust gas, the cyclonic filter comprising an enclosure having a cylindrical sidewall extending longitudinally along an axis between a first end wall and a second end wall to form an enclosure of an interior space, an exhaust gas inlet through the sidewall to the interior space, and an exhaust gas outlet from the interior space through the first end wall;   the exhaust gas inlet directing exhaust gas into cyclonic flow circumscribed by the sidewall within the interior space and carrying unburned particulate matter toward the second end wall as exhaust gas detaches from the cyclonic flow to flow out of the interior space through the exhaust gas outlet;   a first tube which extends within the interior space from the second end wall coaxial with the sidewall;   a burner providing particulate-incinerating flow which enters, passes through, and exits the first tube; and   a second tube disposed within the interior space coaxially surrounding, and cooperating with, the first tube to cause particulate-incinerating flow exiting the first tube to draw particulate matter, which is being carried by the cyclonic flow toward the second end wall, into the second tube through clearance between the two tubes for ensuing entrainment with, and incineration by, particulate-incinerating flow exiting the first tube and then out of the second tube.   
     
     
         2 . An engine as set forth in  claim 1  further comprising structure defining a flow path for conveying flow out of the second tube for entrainment with exhaust gas which has detached from the cyclonic flow. 
     
     
         3 . An engine as set forth in  claim 2  in which the structure opens within the interior space to cause the entrainment of flow out of the second tube with exhaust gas which has detached from the cyclonic flow to occur within the interior space. 
     
     
         4 . An engine as set forth in  claim 3  in which the structure comprises a third tube which cooperates with the second tube to form a first portion of the flow path by radial clearance between the second tube and the third tube, and third tube which cooperates with a fourth tube to form a second portion of the flow path by radial clearance between the third tube and the fourth tube. 
     
     
         5 . An engine as set forth in  claim 1  in which the burner is constructed to impart swirl to the particulate-incinerating flow passing through first tube. 
     
     
         6 . An engine as set forth in  claim 1  including an acoustic agglomerator for increasing density of unburned particulate matter in exhaust gas prior to exhaust gas entering the cyclonic filter. 
     
     
         7 . A method of treating exhaust gas coming from combustion chambers of an internal combustion engine before passing into surrounding atmosphere, the method comprising:
 separating unburned particulate matter out of exhaust gas by directing exhaust gas through an exhaust gas inlet of a cyclonic filter having a sidewall extending between a first end wall and a second end wall and into cyclonic flow circumscribed by the sidewall to cause unburned particulate matter to move toward the second end wall as exhaust gas detaches from the cyclonic flow to flow out of the cyclonic filter through an exhaust gas outlet in the first end wall;   providing particulate-incinerating flow which enters, passes through, and exits a first tube inside the cyclonic filter and then enters a second tube inside the cyclonic filter; and   causing particulate-incinerating flow exiting the first tube and entering the second tube to draw particulate matter, which is being carried by the cyclonic flow toward the second end wall, into the second tube through clearance between the two tubes for ensuing entrainment with, and incineration by, particulate-incinerating flow as the entrained flows pass through the second tube.   
     
     
         8 . A method as set forth in  claim 7  further comprising defining a flow path inside the cyclonic filter for conveying the entrained flows out of the second tube and into entrainment with exhaust gas which has detached from the cyclonic flow. 
     
     
         9 . A method as set forth in  claim 7  comprising imparting swirl to the particulate-incinerating flow. 
     
     
         10 . A method as set forth in  claim 7  including increasing density of unburned particulate matter in exhaust gas prior to exhaust gas entering the cyclonic filter.