Counterflow fuel injection nozzle in a burner-boiler system

Abstract

A counterflow fuel injection nozzle for injecting fuel is disclosed. The nozzle includes a nozzle wall having an interior surface that defines a nozzle interior, the interior for receiving a fuel therein. The nozzle further has a fuel passageway formed in the nozzle wall for distributing the fuel from the interior to a location exterior of the nozzle, the fuel distributed to the exterior location in a fuel flow injection direction. An airstream is provided in a prevailing air flow direction in the location exterior of the nozzle. At least one vector component of the fuel flow injection direction opposes at least one vector component of the prevailing air flow direction. In this manner, by distributing fuel into an air flow at a counterflow angle, improved control of mixing of the fuel in the air is achieved. The counterflow nozzle may be included as part of a new burner or as a retrofit to existing burners in order to incorporate counterflow mixing. Advantageously, burner turndown ratios and stability are enhanced through the use of the counterflow fuel injection nozzles with burners that use FGR (i.e., have lower O 2 in combustion air supplied to the burner).

1 . A counterflow fuel injection nozzle for injecting fuel, the nozzle comprising: 
 a nozzle wall having an interior surface that defines a nozzle interior, the interior for receiving a fuel therein, the nozzle further having a fuel passageway formed in the nozzle wall for distributing the fuel from the interior to a location exterior of the nozzle, the fuel distributed to the exterior location in a fuel flow injection direction;    wherein, when an airstream is provided in a prevailing air flow direction in the location exterior of the nozzle, at least one vector component of the fuel flow injection direction opposes at least one vector component of the prevailing air flow direction.    
     
     
         2 . The counterflow fuel injection nozzle of  claim 1  wherein the fuel passageway terminates in an opening having a diameter in a range of between about 0.063 inches to about 0.141 inches.  
     
     
         3 . The counterflow fuel injection nozzle of  claim 1  wherein the nozzle wall includes a plurality of the fuel passageways, each of which terminate in an opening.  
     
     
         4 . The counterflow fuel injection nozzle of  claim 3  wherein each of the plurality of the fuel passageway openings has a diameter D and there is a distance L between the plurality of openings and wherein a ratio L/D is used as a design parameter.  
     
     
         5 . The counterflow fuel injection nozzle of  claim 4  wherein the ratio of L/D is approximately 5.  
     
     
         6 . The nozzle of  claim 1  wherein the fuel is natural gas.  
     
     
         7 . The counterflow fuel injection nozzle of  claim 3  wherein each of the plurality of passageways has a unique noninterfering fuel injection direction.  
     
     
         8 . The counterflow fuel injection nozzle of  claim 3 , wherein the nozzle includes one of a primary centralized circumferentially disposed notch and a groove into which fuel is initially distributed from at least one of the plurality of passageways.  
     
     
         9 . The counterflow fuel injection nozzle of  claim 1  wherein the distributing occurs by injecting the fuel at a fuel flow injection angle that is in a range of about 15 degrees to about 90 degrees.  
     
     
         10 . The counterflow fuel injection nozzle of  claim 9  wherein the fuel flow injection angle is substantially 30 degrees.  
     
     
         11 . A method of mixing a fuel and air in a burner system, the system comprising a counterflow fuel injection nozzle having a nozzle wall that defines a nozzle interior for receiving the fuel, the nozzle further having a fuel passageway formed in the nozzle wall, the method comprising: 
 passing the air in a prevailing air flow direction exterior of the nozzle wall;    distributing the fuel in a fuel flow injection direction from the nozzle interior through the fuel passageway into the air passing in the prevailing air flow direction exterior of the nozzle wall; and    counterflow mixing the fuel distributed in the fuel flow injection direction with the air passing in the prevailing air flow direction such that at least one vector component of the fuel flow injection direction opposes at least one vector component of the prevailing air flow direction.    
     
     
         12 . The method of  claim 10  wherein the fuel is natural gas.  
     
     
         13 . The method of  claim 10  wherein the distributing occurs by injecting the fuel at a fuel flow injection angle that is in a range of about 30 degrees to about 90 degrees.  
     
     
         14 . The method of  claim 13  wherein the fuel flow injection angle is substantially 45 degrees.  
     
     
         15 . A gas mixing nozzle retrofit for a burner, the retrofit comprising: 
 a counterflow fuel injection nozzle wall having an interior surface that defines a nozzle interior, the interior for receiving a fuel therein, the nozzle further having a fuel passageway formed in the nozzle wall for distributing the fuel from the interior to a location exterior of the nozzle, the fuel distributed to the exterior location in a fuel flow injection direction;    wherein, when an airstream is provided in a prevailing air flow direction in the location exterior of the nozzle, at least one vector component of the fuel flow injection direction opposes at least one vector component of the prevailing air flow direction; and    wherein the counterflow fuel injection nozzle is used to replace a non-counterflow fuel injection nozzle that does not provide for at least one vector component of the fuel flow injection direction that opposes at least one vector component of the prevailing air flow direction when an airstream is provided in a prevailing air flow direction in the location exterior of the nozzle.    
     
     
         16 . The counterflow fuel injection nozzle of  claim 15  wherein the fuel is natural gas.  
     
     
         17 . The counterflow fuel injection nozzle of  claim 15  wherein the nozzle wall includes a plurality of the fuel passageways, each of which terminate in an opening .  
     
     
         18 . A burner system comprising: 
 a fuel line for introducing fuel to create a flame in a combustion chamber within the burner system; and    a counterflow fuel injection nozzle, the nozzle having: 
 nozzle wall having an interior surface that defines a nozzle interior, the interior for receiving a fuel therein, the nozzle further having a fuel passageway formed in the nozzle wall for distributing the fuel from the interior to a location exterior of the nozzle, the fuel distributed to the exterior location in a fuel flow injection direction;  
   wherein, when an airstream is provided in a prevailing air flow direction in the location exterior of the nozzle, at least one vector component of the fuel flow injection direction opposes at least one vector component of the prevailing air flow direction.