Annular premixed pilot in fuel nozzle

Abstract

A combustor for a gas turbine engine has a head end portion that carries at least one fuel/air nozzle. Each fuel/air nozzle includes a premixed pilot nozzle having premix conduits where each premix conduit has an upstream end defining an opening and having a central axis and downstream end defining an outlet and having a central axis where the central axis of the downstream end is non-parallel with a central axis of a center body of the fuel/air nozzle. The premixed pilot nozzle can include an annular channel disposed radially outwardly from the premix conduits and may include air jets that direct air radially outwardly from the premix conduits.

What is claimed is: 
     
         1 . A fuel/air nozzle for a gas turbine engine, the fuel/air nozzle comprising:
 a premixed pilot nozzle having an upstream end axially spaced from a downstream end with respect to an axial center line of a center body of the fuel/air nozzle, wherein the upstream end is connected to a downstream end of the center body; and   the premixed pilot nozzle further defining a plurality of axially elongated, hollow premix conduits annularly arranged around a pilot fuel nozzle portion of the premixed pilot nozzle, each premix conduit having an upstream end defining an entrance opening that communicates fluidly with an interior passage of the center body, each premix conduit having at least one fuel hole in fluid communication with the pilot fuel nozzle portion, each premix conduit including a downstream end defining an exit opening that allows fluid to discharge from the hollow premix conduit;   wherein each downstream end of each premix conduit has a central axis that is not parallel to the central axis of the center body.   
     
     
         2 . The fuel/air nozzle as in  claim 1 , wherein each central axis of at least one premix conduit is disposed at an acute angle with respect to the central axis of the center body. 
     
     
         3 . The fuel/air nozzle as in  claim 1 , wherein the premixed pilot nozzle further defines an annular channel disposed radially outwardly from the premix conduits, the annular channel being configured to communicate fluidly with the interior passage of the center body, the annular channel defining a plurality of air jets, at least one of the air jets being disposed nearby one of the exit openings of at least one of the premix conduits and having a central axis. 
     
     
         4 . The fuel/air nozzle as in  claim 3 , wherein the central axis of the upstream end of at least one premix conduit is configured and disposed to extend in a direction parallel to the central axis of the center body. 
     
     
         5 . The fuel/air nozzle as in  claim 3 , wherein the central axis of at least one of the air jets forms an acute angle with the central axis of the center body. 
     
     
         6 . The fuel/air nozzle as in  claim 3 , wherein the annular channel is configured to taper as it proceeds in the downstream direction toward the air jets. 
     
     
         7 . The fuel/air nozzle as in  claim 1 , further comprising a swozzle including a plurality of swirl blades extending radially across the primary air flow channel, at least one of the swirl blades defining a fuel conduit having an inlet at one end thereof and an outlet at an opposite end thereof in fluid communication with the primary air flow channel. 
     
     
         8 . The fuel/air nozzle as in  claim 1 , wherein a downstream end of the pilot fuel nozzle defines a plurality of fuel jets oriented to direct a jet of fuel from the pilot fuel nozzle against a backside surface of the downstream end of the premixed pilot nozzle. 
     
     
         9 . The fuel/air nozzle as in  claim 1 , further comprising a fuel plenum wall disposed radially outwardly from the pilot fuel nozzle and defining a fuel plenum between the pilot fuel nozzle and the fuel plenum wall, the fuel plenum wall further defining a plurality of fuel holes, at least one of the fuel holes being in fluid communication with at least one of the fuel jets via the fuel plenum, each premix conduit being disposed radially outwardly from the fuel plenum wall and in fluid communication with at least one of the fuel holes. 
     
     
         10 . A combustor for a gas turbine engine, the combustor comprising:
 a head end portion;   at least one fuel/air nozzle carried by the head portion, each fuel/air nozzle further comprising:
 a center body defining a central axis of the fuel/air nozzle and an internal passage within the fuel/air nozzle; 
 a fuel supply line extending axially within the center body and in fluid communication with a source of fuel; 
 a premixed pilot nozzle having an upstream end axially spaced from a downstream end with respect to the axial center line of the center body, wherein the upstream end is connected to a downstream end of the center body; and 
 the premixed pilot nozzle further defining a plurality of axially elongated, hollow premix conduits annularly arranged around a pilot fuel nozzle portion of the premixed pilot nozzle, each premix conduit having an upstream end defining an entrance opening in fluid communication with interior passage, each premix conduit having at least one fuel hole in fluid communication with the pilot fuel nozzle portion, each premix conduit including a downstream end defining an exit opening that allows fluid to discharge from the hollow premix conduit; 
 wherein each downstream end of each premix conduit has a central axis that is not parallel to the central axis of the center body. 
   
     
     
         11 . The combustor as in  claim 10 , wherein the premixed pilot further defines an annular channel disposed radially outwardly from the premix conduits, the annular channel being configured to communicate fluidly with the interior passage of the center body, the annular channel defining a plurality of air jets. 
     
     
         12 . The combustor as in  claim 11 , wherein at least one of the air jets is disposed adjacent to one of the exit openings of at least one of the premix conduits and has a central axis that is disposed at an acute angle with respect to the central axis of the nearby one of the exit openings of at least one of the premix conduits. 
     
     
         13 . The combustor as in  claim 11 , wherein the annular channel tapers as it proceeds in the downstream direction toward the air jets. 
     
     
         14 . A method of operating a fuel/air nozzle having a premix pilot nozzle including a plurality of premix conduits annularly arranged around a pilot fuel nozzle portion of the premixed pilot nozzle, the method comprising:
 delivering a flow of pilot fuel to the premix pilot nozzle;   delivering a flow of air through the center body to the premix pilot nozzle;   mixing the pilot fuel with the flow of air in a plurality of axially elongated, hollow premix conduits wherein each premix conduit defines a central axis at the downstream end thereof that is not parallel to a central axis of the center body and that discharges the fuel/air mixture from the downstream end of the premix pilot nozzle; and   expelling the fuel/air mixture from the exit openings of the premix conduits of the premixed pilot nozzle.   
     
     
         15 . The method as in  claim 14 , further comprising expelling the fuel/air mixture from the premix conduits of the premixed pilot nozzle in a direction that is radially away from the central axis of the center body. 
     
     
         16 . The method as in  claim 15 , further comprising the step of diverting some of the flow of air to an annular channel that is disposed radially outwardly from the premix conduits of the premixed pilot nozzle. 
     
     
         17 . The method as in  claim 16 , wherein the pressure of the air expelled from the annular channel exceeds the pressure of the air entering the annular channel. 
     
     
         18 . The method as in  claim 16 , wherein the annular channel tapers as it proceeds in the downstream direction. 
     
     
         19 . The method as in  claim 16 , further comprising the step of expelling air from the annular channel of the premixed pilot nozzle in a direction that is away from the exit openings of the premix conduits. 
     
     
         20 . The method as in  claim 19 , wherein the air expelled from the annular channel is directed away from the central axis of the center body.