System for dispensing fuel into an exhaust system of a diesel engine

Abstract

A system is disclosed for dispensing fuel into the transient flow of an exhaust system to control exhaust emissions. A controller initiates the delivery of fuel into the exhaust when an emissions control device, such as a diesel particulate filter, requires increased exhaust temperatures for regeneration. In operation, pressurized fuel and pressurized air are supplied to a fuel delivery device, wherein a fuel injector pre-mixes fuel with air. The fuel-air mixture is then dispensed into the exhaust flow through a nozzle, causing a rapid pressure drop in the mixture that results in the pressurized air expanding rapidly, breaking the fuel spray into fine particles.

1 . A system for dispensing a mixture of liquid and air into an exhaust stream comprising: 
 an injector housing defining an air passage and a liquid passage, the injector housing also defining a cooling passage structure that includes a plurality of passage lengths that extend along a side of the housing for cooling the side of the housing;    an air inlet for providing pressurized air to the air passage of the injector housing;    a liquid inlet for providing liquid to the liquid passage of the injector housing;    a mixing location in fluid communication with the air passage;    an injector mounted within the injector housing for injecting liquid from the liquid passage into the mixing location, wherein the liquid injected by the injector mixes with pressurized air from the air passage at the mixing location;    a dispenser for dispensing the mixture of liquid and air into the exhaust stream.    
   
   
       2 . The system of  claim 1 , wherein the mixing location includes a mixing chamber defined at least partially within the injector housing.  
   
   
       3 . The system of  claim 1 , wherein the dispenser includes a dispensing tube that projects outwardly from the injector housing, the dispensing tube including an orifice spaced from the injector housing, wherein the mixing location includes a mixing chamber defined at least partially within the dispensing tube.  
   
   
       4 . The system of  claim 1 , wherein the dispenser includes a dispensing tube that projects outwardly from the injector housing, the dispensing tube including an orifice spaced from the injector housing.  
   
   
       5 . The system of  claim 1 , further comprising a source of liquid for supplying liquid to the liquid inlet of the injector housing, wherein the injector housing also defines a liquid return outlet for returning undispensed liquid from the injector housing back to the source of liquid, and wherein at least some of the liquid from the source of liquid flows through the passage lengths of the cooling passage structure to cool the injector housing.  
   
   
       6 . The system of  claim 5 , wherein the passage lengths of the cooling passage structure are generally parallel to one another.  
   
   
       7 . The system of  claim 1 , wherein the injector housing includes a first block coupled to a second block, and wherein the injector is mounted between the first and second blocks.  
   
   
       8 . The system of  claim 7 , further comprising a liquid pressure regulator mounted between the first and second blocks.  
   
   
       9 . The system of  claim 8 , further comprising a liquid return outlet in fluid communication with the liquid pressure regulator, the liquid return outlet and the air inlet being defined by the second block and the liquid inlet being defined by the first block.  
   
   
       10 . The system of  claim 1 , further comprising a pressure sensor mounted to the injector housing for determining a pressure at the mixing location.  
   
   
       11 . The system of  claim 1 , further comprising a pressurized air flow regulating orifice for regulating air flow through the air passage.  
   
   
       12 . The system of  claim 1 , wherein the orifice diameter is approximately 0.04 to 0.07 inches.  
   
   
       13 . The system of  claim 1 , further comprising a pump box for providing liquid to the liquid inlet, the pump box containing a pump, a liquid filter and one or more safety switches.  
   
   
       14 . The system of  claim 1 , wherein the pressure of the liquid within the liquid passage is approximately 30 to 50 pounds per square inch (gauge) greater than the pressure of the supply air.  
   
   
       15 . The system of  claim 1 , wherein the pressure is approximately 40 to 60 pounds per square inch gauge pressure at the mixing location.  
   
   
       16 . An apparatus for dispensing a substance into an exhaust stream within an exhaust conduit comprising: 
 a mounting base including a first portion having a curved surface for engaging an exterior surface of the exhaust conduit, and a second portion including a mounting surface offset from the curved surface by a spacing; and    an injector housing mounted at the mounting surface of the mounting base and a tube through which the substance is dispensed, the tube extending from the injector housing across the spacing and through the curved surface, wherein the tube is adapted to project into the exhaust conduit when the apparatus is mounted to the exhaust conduit.    
   
   
       17 . The apparatus of  claim 16 , wherein the mounting base is secured to the exhaust conduit by at least one u-bolt.  
   
   
       18 . The apparatus of  claim 16 , wherein the spacing includes an air gap of at least one-half of an inch.  
   
   
       19 . An exhaust system for treating engine exhaust, the exhaust system comprising: 
 an exhaust conduit receiving exhaust from a combustion engine;    a treatment device positioned within the exhaust conduit for treating the exhaust; and    an injector device mounted to the exhaust conduit at a location between the treatment device and the engine, the injector device including: 
 an injector housing positioned outside the exhaust conduit, the injector housing defining an air passage and a liquid passage;  
 an air inlet for providing pressurized air to the air passage of the injector housing;  
 a liquid inlet for providing liquid to the liquid passage of the injector housing;  
 a mixing location in fluid communication with the air passage;  
 an injector mounted within the injector housing for injecting liquid from the liquid passage into the mixing location, wherein the liquid injected by the injector mixes with pressurized air from the air passage at the mixing location;  
 a dispensing tube that projects outwardly from the injector housing, the tube extending from the injector housing, through a wall of the exhaust conduit, to an interior of the exhaust conduit, the dispensing tube including an orifice for dispensing the mixture of liquid and air into the exhaust within the exhaust conduit.  
   
   
   
       20 . The exhaust system of  claim 19 , wherein the orifice is located adjacent a central axis of the exhaust conduit.  
   
   
       21 . The exhaust system of  claim 19 , wherein the orifice diameter is approximately 0.04 to 0.07 inches.  
   
   
       22 . The exhaust system of  claim 19 , further comprising a mount secured to the exhaust conduit for spacing the injector housing from the exhaust conduit.  
   
   
       23 . The exhaust system of  claim 19 , wherein an air flow rate within the air passage does not exceed 1 standard cubic foot per minute.  
   
   
       24 . A method for introducing a liquid reactant into a vehicle exhaust pipe, the method comprising: 
 mixing the liquid reactant with compressed air at a location outside the exhaust pipe to form a liquid/air mixture, the compressed air having a flow rate that never exceeds 1 standard cubic foot per minute;    delivering the liquid/air mixture to an orifice of a dispenser; and    introducing the liquid/air mixture into the interior or the exhaust pipe through the orifice of the dispenser.