Particulate filter cleaning methods and apparatus

Abstract

An internal combustion engine is run to emit an exhaust flow containing particulate. The exhaust flow passes through a filter element to remove at least a portion of the particulate from the exhaust flow. The removed particulate accumulates on the filter element. The filter element is cleaned. The cleaning includes detonating a fuel-oxidizer combination in a conduit and impacting the filter element with a wave from the detonation.

1 . A method comprising:
 operating an internal combustion engine in a first mode comprising:
 running the engine to emit an exhaust flow containing particulate from the engine; 
 passing the exhaust flow through a filter element to remove at least a portion of 
   the particulate from the exhaust flow, the removed particulate accumulating on the filter element;   cleaning the filter element, the cleaning comprising:
 detonating a fuel-oxidizer combination in a conduit; and 
 impacting the filter element with a wave from the detonation. 
   
   
   
       2 . The method of  claim 1  wherein:
 the removed particulate accumulates as soot; and   the impacting and an associated blowdown jet incinerate the soot to form ash.   
   
   
       3 . The method of  claim 2  wherein the cleaning further comprises:
 collecting the ash in a trap.   
   
   
       4 . The method of  claim 3  wherein the cleaning comprises:
 a plurality of said detonations and impacts.   
   
   
       5 . The method of  claim 4  further comprising:
 removing collected ash from the trap after a plurality of the cleanings.   
   
   
       6 . The method of  claim 1  wherein:
 the cleaning comprises:
 measuring a pressure difference across the filter element; 
 responsive to the pressure difference reaching a first predetermined value, 
   initiating said detonating; and   repeating the detonating until the measured pressure difference decreases to a second predetermined value, lower than the first predetermined value.   
   
   
       7 . The method of  claim 1  wherein:
 the cleaning occurs while the internal combustion engine is running.   
   
   
       8 . The method of  claim 1  wherein:
 the cleaning occurs while the internal combustion engine is not running.   
   
   
       9 . The method of  claim 1  wherein:
 the cleaning comprises:
 introducing the fuel as at least one of propane and MAPP gas; and 
 introducing the oxidizer as essentially oxygen. 
   
   
   
       10 . The method of  claim 1  wherein:
 the running comprises running as a compression ignition engine.   
   
   
       11 . The method of  claim 1  wherein:
 heat is transferred from the exhaust flow to the fuel-oxidizer combination in the conduit.   
   
   
       12 . An apparatus comprising:
 an internal combustion engine; and   an exhaust system coupled to the internal combustion engine and including:
 an exhaust flowpath; 
 a particulate filter element along the exhaust flowpath; 
 a conduit having a first end and a second end, the second end being an outlet facing the filter element downstream of the filter element along the exhaust flowpath; 
 a source of fuel and oxidizer coupled to the conduit to deliver the fuel and oxidizer; and 
 an ignitor coupled to the conduit to ignite the fuel and oxidizer in the conduit. 
   
   
   
       13 . The apparatus of  claim 12  wherein:
 the exhaust system further comprises:
 a first pressure sensor positioned to measure a pressure upstream of the filter element; 
 a second pressure sensor positioned to measure a pressure downstream of the filter element; and 
 a controller coupled to the first pressure sensor, second pressure sensor, source, and ignitor, and configured to operate the conduit responsive to outputs of the first and second pressure sensors to discharge waves from the conduit to impact the filter element. 
   
   
   
       14 . The apparatus of  claim 12  wherein:
 the fuel consists essentially of at least one of propane and MAPP gas; and   the oxidizer consists essentially of pure oxygen.   
   
   
       15 . The apparatus of  claim 12  wherein:
 the fuel consists essentially of diesel fuel; and   the oxidizer consists essentially of pure oxygen.   
   
   
       16 . The apparatus of  claim 12  wherein:
 the filter element does not have a separate heater; and   there is no separate second filter element positioned for blowback filtering of ash from said filter element.   
   
   
       17 . The apparatus of  claim 12  wherein:
 the apparatus is a wheeled vehicle.   
   
   
       18 . An apparatus comprising:
 an internal combustion engine; and   an exhaust system coupled to the internal combustion engine to pass an exhaust flow from the internal combustion engine and comprising:
 a filter element positioned to filter particulate from the exhaust flow; and 
 detonative cleaning means for cleaning the filter element. 
   
   
   
       19 . The apparatus of  claim 18  wherein:
 the internal combustion engine is a diesel engine;   the detonative cleaning means comprises:
 a conduit having a first end and a second end, the second end being an outlet facing the filter element; 
 a source of fuel and oxidizer coupled to the conduit to deliver the fuel and oxidizer; and 
 an ignitor coupled to the conduit to ignite the fuel and oxidizer in the conduit; 
   the exhaust system further comprises:   a controller coupled to the source and ignitor and configured to discharge waves from the conduit responsive to a measured pressure difference across the filter element.   
   
   
       20 . A method for retrofitting a pollution source or reengineering a configuration of the pollution source, the pollution source having an internal combustion engine, the method comprising:
 adding a filter element in an exhaust gas flowpath from the internal combustion engine;   adding a detonative cleaning apparatus positioned to discharge a wave to impact the filter element.   
   
   
       21 . The method of  claim 20  wherein:
 the filter replaces a larger baseline filter.   
   
   
       22 . The method of  claim 20  wherein:
 the detonative cleaning apparatus comprises:
 a conduit having a first end and a second end, the second end being an outlet facing the filter element; 
 a source of fuel and oxidizer coupled to the conduit to deliver the fuel and oxidizer; and 
 an ignitor coupled to the conduit to ignite the fuel and oxidizer in the conduit. 
   
   
   
       23 . The method of  claim 1  wherein:
 the cleaning comprises momentarily reversing flow through the filter element.   
   
   
       24 . The method of  claim 2  wherein:
 the blowdown jet passes through the filter element in a reverse direction from the exhaust flow.   
   
   
       25 . The apparatus of  claim 12  wherein:
 the particulate filter element has, along the exhaust flowpath, an upstream surface and a downstream surface; and   the second end faces the downstream surface.   
   
   
       26 . The method of  claim 11  wherein:
 the heat is transferred from an exhaust pipe to the fuel-oxidizer combination in a space within the conduit surrounding the exhaust pipe.