LIFTED FLAME LOW NOx BURNER WITH FLAME POSITION CONTROL

Abstract

A low NOx burner includes a charging mechanism to charge a fuel stream or diluted fuel stream. A flame supported by the charged fuel stream can be held at a lifted location corresponding to high fuel dilution. If electrical power is lost or removed, the flame is shifted to a location corresponding to a lower fuel dilution.

1 . A system for supporting a low oxides of nitrogen (NOx) flame, comprising:
 a charging mechanism configured to apply a voltage to a fuel stream emitted from a fuel nozzle;   a first flame support surface disposed adjacent to the fuel nozzle and configured to support a flame when the voltage is applied to the fuel stream; and   an aerodynamic flame holder disposed adjacent to the fuel nozzle and configured to support the flame when the voltage is not applied to the fuel stream.   
     
     
         2 . (canceled) 
     
     
         3 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 1 , further comprising a fuel nozzle, the fuel nozzle including an electrically insulating body configured to isolate the fuel stream from a voltage or ground other than a voltage corresponding to the voltage applied to the fuel stream by the charging mechanism. 
     
     
         4 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 3 , wherein the fuel nozzle includes an electrically conductive body coupled to the electrically insulating body. 
     
     
         5 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 3 , wherein the first flame support surface is disposed more distal from the fuel nozzle than the aerodynamic flame holder. 
     
     
         6 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 1 , wherein the first flame support surface is configured to support the flame at a distance from the fuel nozzle corresponding to a reduced fuel concentration compared to the fuel concentration proximate the aerodynamic flame holder. 
     
     
         7 - 8 . (canceled) 
     
     
         9 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 6 , wherein the first flame support surface includes a perforated flame holder configured to support a low NOx flame in a plurality of passages extending through the perforated flame holder. 
     
     
         10 . (canceled) 
     
     
         11 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 1 , further comprising a voltage source operatively coupled to the charging mechanism. 
     
     
         12 - 15 . (canceled) 
     
     
         16 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 1 , wherein the aerodynamic flame holder is configured to cooperate with the fuel stream to support the flame when the charging mechanism loses operability for applying the voltage to the fuel stream. 
     
     
         17 . (canceled) 
     
     
         18 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 1 , wherein the first flame support surface includes a flame support electrode configured to attract a charge imparted by the voltage applied to the fuel stream. 
     
     
         19 - 20 . (canceled) 
     
     
         21 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 18 , further comprising a voltage source operatively coupled to the flame support electrode;
 wherein the voltage source is configured to drive the flame support electrode to a voltage opposite in sign from the voltage applied to the fuel stream.   
     
     
         22 . (canceled) 
     
     
         23 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 1 , wherein the charging mechanism is disposed to apply the voltage to the fuel stream at a location between the fuel nozzle and the aerodynamic flame holder. 
     
     
         24 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 23 , wherein the charging mechanism is configured to impart a charge of a selected polarity to the fuel stream by application of the voltage to the fuel stream. 
     
     
         25 - 26 . (canceled) 
     
     
         27 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 24 , wherein the charge mechanism is configured to apply a voltage to the aerodynamic flame holder selected to repel the charge imparted to the fuel stream. 
     
     
         28 . (canceled) 
     
     
         29 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 27 , wherein the aerodynamic flame holder is configured to cause one or more vortices to form in the fuel stream when the fuel stream passes in close proximity to the aerodynamic flame holder. 
     
     
         30 - 34 . (canceled) 
     
     
         35 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 1 , further comprising a fuel stream repulsion electrode configured to push the fuel stream away from the aerodynamic flame holder when the fuel stream carries a charge imparted by the applied voltage. 
     
     
         36 - 43 . (canceled) 
     
     
         44 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 1 , further comprising a fuel stream attraction electrode configured to attract the fuel stream away from the aerodynamic flame holder when the fuel stream carries a charge imparted by the applied voltage. 
     
     
         45 . (canceled) 
     
     
         46 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 1 , further comprising:
 a fuel stream repulsion electrode; and   a voltage source configured to apply a voltage to the charging mechanism and the fuel stream repulsion electrode;   wherein a loss of voltage applied by the voltage source causes the fuel stream to not be held away from the aerodynamic flame holder, and causes the flame to be supported by a vortex formed adjacent to the aerodynamic flame holder.   
     
     
         47 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 1 , further comprising one or more field electrodes disposed to apply an electric field to the flame, the electric field being selected to enhance combustion of the flame. 
     
     
         48 . (canceled) 
     
     
         49 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 48 , further comprising a voltage source operatively coupled to the one or more field electrodes, the voltage source being configured to drive the one or more field electrodes with a time-varying voltage. 
     
     
         50 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 48 , wherein the one or more field electrodes are disposed more distal from a fuel nozzle than the first flame support surface. 
     
     
         51 - 54 . (canceled) 
     
     
         55 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 1 , wherein the charging mechanism includes a sharp electrode configured to operate as a charge ejecting corona electrode. 
     
     
         56 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 1 , wherein the charging mechanism includes a serrated electrode. 
     
     
         57 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 1 , wherein the charging mechanism includes an electrically conductive fuel nozzle. 
     
     
         58 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 1 , wherein the charging mechanism includes an ionizer configured to supply ions to the fuel stream after exit of the fuel stream from the fuel nozzle. 
     
     
         59 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 1 , wherein the charging mechanism includes an ionizer configured to supply ions to the fuel stream prior to exit of the fuel stream from the fuel nozzle. 
     
     
         60 . The system for supporting a low oxides of nitrogen (NOx) flame of  claim 1 , wherein the charging mechanism includes an ionizer configured to ionize flue gas or air prior to a merging of the flue gas or air with the fuel stream. 
     
     
         61 . A burner, comprising:
 a means for applying a voltage to a fuel stream;   a first means for holding a flame supported by the fuel stream at a first location when the voltage is applied to the fuel stream; and   a second means for holding a flame supported by the fuel stream at a second location when the voltage is not applied to the fuel stream.   
     
     
         62 . The burner of  claim 61 , further comprising a means for supplying the fuel stream to the means for applying a voltage to the fuel stream. 
     
     
         63 . The burner of  claim 61 , further comprising a means for outputting a voltage operatively coupled to the means for applying a voltage to a fuel stream. 
     
     
         64 . The burner of  claim 61 , wherein the means for applying a voltage and the first means for holding a flame are configured to cooperate to support a low NOx flame. 
     
     
         65 . The burner of  claim 61 , wherein the means for at least applying a voltage and the second means for holding a flame are configured to cooperate to support a high stability flame. 
     
     
         66 . The burner of  claim 61 , wherein the first means for holding a flame and the second means for holding a flame are configured to cooperate to shift a flame from the first location to the second location when the means for applying a voltage fails to apply a voltage to the fuel stream. 
     
     
         67 . A method for supporting a flame that is stable under changing conditions, comprising:
 applying a voltage to a fuel stream;   supporting a lean, low NOx flame at a first location with the fuel stream;   stopping application of the voltage to the fuel stream;   shifting the flame from the first location to a second location; and   supporting a rich, high stability flame at the second location.   
     
     
         68 . The method for supporting a flame that is stable under changing conditions of  claim 67 , further comprising:
 resuming the applying a voltage to the fuel stream; and   shifting the flame from the second location to the first location.   
     
     
         69 . The method for supporting flame that is stable under changing conditions of  claim 68 , wherein the shifting the flame from the second location to the first location and the resuming the applying a voltage to the fuel stream include resuming the applying a voltage to the fuel stream and shifting the lame from the second location to the first location substantially simultaneously. 
     
     
         70 - 71 . (canceled) 
     
     
         72 . The method for supporting a flame that is stable under changing conditions of  claim 68 , further comprising applying a voltage to an aerodynamic flame holder selected to repel a charges imparted to the fuel stream by the voltage applied to the fuel stream. 
     
     
         73 . (canceled) 
     
     
         74 . The method for supporting a flame that is stable under changing conditions of  claim 68 , wherein shifting the flame from the second location to the first location includes causing a mutual repulsion between like charges in the fuel stream. 
     
     
         75 - 78 . (canceled) 
     
     
         79 . The method for supporting a flame that is stable under changing conditions of  claim 67 , wherein applying a voltage to the fuel stream includes applying the voltage to the fuel stream at a position between a fuel nozzle and an aerodynamic flame holder at the second location. 
     
     
         80 . The method for supporting a flame that is stable under changing conditions of  claim 67 , wherein applying a voltage to the fuel stream includes imparting a charge having a selected polarity to the fuel stream. 
     
     
         81 . (canceled) 
     
     
         82 . The method for supporting a flame that is stable under changing conditions of  claim 67 , wherein applying a voltage to the fuel stream includes ejecting a charge from a sharp electrode. 
     
     
         83 . (canceled) 
     
     
         84 . The method for supporting a flame that is stable under changing conditions of  claim 67 , wherein applying a voltage to the fuel stream includes applying a voltage to the fuel stream via a conductive fuel nozzle. 
     
     
         85 . The method for supporting a flame that is stable under changing conditions of  claim 67 , wherein applying the voltage to the fuel stream includes supplying ions to the fuel stream nozzle. 
     
     
         86 - 87 . (canceled) 
     
     
         88 . The method for supporting a flame that is stable under changing conditions of  claim 67 , wherein supporting a lean, low NOx flame at a first location with the fuel stream includes supporting the flame with a first flame support surface at the first location disposed more distal from a fuel nozzle than the second location. 
     
     
         89 . The method for supporting a flame that is stable under changing conditions of claim  86 , wherein supporting the flame with a first flame support surface at the first location includes supporting a perforated flame holder at the first location, the perforated flame holder being configured to support a flame in a plurality of gas passages formed to extend through the perforated flame holder. 
     
     
         90 . The method for supporting a flame that is stable under changing conditions of  claim 67 , wherein:
 applying a voltage to a fuel stream includes applying a voltage having a fi polarity to the fuel stream; and   supporting a lean, low NOx flame at a first location includes attracting the flame to the first location by applying, to a flame support electrode at the first location, a voltage having a second polarity, opposite the first polarity.   
     
     
         91 - 94 . (canceled) 
     
     
         95 . The method for supporting a flame that is stable under changing conditions of  claim 67 , wherein supporting a rich, high stability flame at a second location includes supporting the flame with a first aerodynamic flame support surface disposed at the second location. 
     
     
         96 - 97 . (canceled) 
     
     
         98 . The method for supporting a flame that is stable under changing conditions of  claim 67 , wherein supporting a lean, low NOx flame at a first location with the fuel stream includes supporting the flame at a distance from a fuel nozzle corresponding to a reduced fuel concentration compared to a fuel concentration proximate to the second location. 
     
     
         99 - 101 . (canceled) 
     
     
         102 . The method for supporting a flame that is stable under changing conditions of claim  101 , further comprising applying a voltage to an aerodynamic flame holder or a repelling electrode at the second location, the voltage being selected to repel a charge carried by the fuel stream. 
     
     
         103 - 104 . (canceled) 
     
     
         105 . The method for supporting a flame that is stable under changing conditions of  claim 67 , wherein shifting the flame from the first location to a second location includes causing the fuel stream to pass in close proximity to an aerodynamic flame holder at the second location when no voltage is applied to the fuel stream. 
     
     
         106 - 107 . (canceled) 
     
     
         108 . The method for supporting a flame that is stable under changing conditions of  claim 67 , further comprising, while the lean, low NOx flame is supported at the first location, applying an electric field to the flame with one or more field electrodes, the electric field being selected to enhance combustion in the flame. 
     
     
         109 . (canceled) 
     
     
         110 . The method for supporting a flame that is stable under changing conditions of  claim 108 , wherein applying an electric field to the flame with one or more field electrodes includes applying a time-varying voltage to the one or more field electrodes. 
     
     
         111 . The method for supporting a flame that is stable under changing conditions of  claim 108 , wherein applying an electric field to the flame with one or more field electrodes includes applying the electric field with one or more field electrodes disposed more distal from a fuel nozzle than the first location. 
     
     
         112 - 114 . (canceled) 
     
     
         115 . The method for supporting a flame that is stable under changing conditions of  claim 108 , wherein applying an electric field to the flame with one or more field electrodes includes flattening the flame with the electric field.