Air shield for a fuel injector of a combustor

Abstract

An air shield for an injector of a combustor includes a first section that extends axially from a first end to a second end, and a channel defined by the air shield. The channel includes at least one inlet proximate to the second end. The at least one inlet is configured to receive a channel airflow that is a portion of a surrounding airflow. The channel is configured to control a distribution of the channel airflow to the injector.

What is claimed is: 
     
         1 . An air shield for an injector of a combustor, said air shield comprising:
 a first section that extends axially from a first end to a second end; and   a channel defined by said air shield, said channel comprises at least one inlet proximate to said second end, said at least one inlet is configured to receive a channel airflow that is a portion of a surrounding airflow, said channel is configured to control a distribution of the channel airflow to the injector.   
     
     
         2 . The air shield of  claim 1 , wherein said first section includes a neck proximate to said second end and a pair of shoulder regions that extend from said neck, said at least one inlet is located on at least one of said neck and said shoulder regions. 
     
     
         3 . The air shield of  claim 2 , wherein said at least one inlet includes a respective aperture near each of said shoulder regions. 
     
     
         4 . The air shield of  claim 1 , wherein said channel is further configured to distribute the channel airflow substantially evenly around a perimeter of an inlet of the injector. 
     
     
         5 . The air shield of  claim 4 , wherein said air shield further comprises an annular dome region proximate said first end, said annular dome region comprises a peak configured to be positioned over a rim of the inlet of the injector. 
     
     
         6 . The air shield of  claim 5 , wherein said air shield further comprises a scroll region proximate said first end, said scroll region is defined by a radius that generally decreases along an arcuate path configured to lie about the inlet of the injector. 
     
     
         7 . The air shield of  claim 6 , wherein said air shield further comprises a transition region shaped to transition the channel airflow to a velocity that approaches the injector generally tangential to the inlet of the injector. 
     
     
         8 . The air shield of  claim 1 , wherein said air shield is configured to enclose at least a portion of a fuel supply line to the injector. 
     
     
         9 . The air shield of  claim 1 , wherein said air shield further comprises a second section, said first section comprises a telescoping portion at said second end that is configured to extend at least partially over said second section. 
     
     
         10 . The air shield of  claim 1 , wherein said air shield is configured to extend circumferentially along the combustor for a maximum distance of about one times to about three times a diameter of the injector. 
     
     
         11 . A combustor for a gas turbine, said combustor comprising:
 a liner that defines a primary combustion zone;   a sleeve that substantially circumscribes said liner;   a secondary combustion zone downstream from, and in flow communication with, said first combustion zone;   an injector coupled to said sleeve upstream from said secondary combustion zone, said injector comprises at least one transfer tube in flow communication with said primary combustion zone; and   an air shield comprising:
 a first section that extends axially from a first end to a second end; and 
 a channel defined by said air shield, said channel comprises at least one inlet proximate to said second end, said at least one inlet is configured to receive a channel airflow that is a portion of a surrounding airflow of said combustor, said channel is configured to control a distribution of the channel airflow to said injector. 
   
     
     
         12 . The combustor of  claim 11 , wherein said first section includes a neck proximate to said second end and a pair of shoulder regions that extend from said neck, said at least one inlet is located on at least one of said neck and said shoulder regions. 
     
     
         13 . The combustor of  claim 12 , wherein said at least one inlet includes a respective aperture near each of said shoulder regions. 
     
     
         14 . The combustor of  claim 11 , wherein said channel is further configured to distribute the channel airflow substantially evenly around a perimeter of an inlet of said injector. 
     
     
         15 . The combustor of  claim 14 , wherein said air shield further comprises an annular dome region proximate said first end, said annular dome region comprises a peak positioned over a rim of said inlet of said injector. 
     
     
         16 . The combustor of  claim 14 , wherein said air shield further comprises a scroll region proximate said first end, said scroll region is defined by a radius that generally decreases along an arcuate path about said inlet of said injector. 
     
     
         17 . The combustor of  claim 16 , wherein said air shield further comprises a transition region shaped to transition the channel airflow to a velocity that approaches said injector generally tangential to said inlet of said injector. 
     
     
         18 . The combustor of  claim 11 , wherein said air shield is configured to enclose at least a portion of a fuel supply line to said injector. 
     
     
         19 . The combustor of  claim 11 , wherein said air shield further comprises a second section, said first section comprises a telescoping portion at said second end that is configured to extend at least partially over said second section. 
     
     
         20 . The combustor of  claim 11 , wherein said air shield extends circumferentially along said combustor for a maximum distance of about one times to about three times a diameter of said injector.