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 that are configured with concentric axes that direct the fuel/air mixture axially from the premixed pilot nozzle. The premixed pilot nozzle can include an annular channel disposed radially outwardly from the premix and including 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:
 an axially elongating peripheral wall defining an outer envelope of the fuel/air nozzle, the peripheral wall having an outer surface and an inner surface facing opposite the outer surface and defining an axially elongating inner cavity;   a hollow, axially elongating centerbody disposed within the inner cavity of the fuel/air nozzle and defining a central axis, the centerbody being defined by a centerbody wall defining an upstream end and a downstream end disposed axially opposite the upstream end, the centerbody wall being defined by an exterior surface and an interior surface facing opposite the exterior surface, the interior surface of the centerbody wall defining an axially elongating interior passage disposed concentrically about the central axis of the centerbody;   an elongated, hollow fuel supply line extending axially through the interior passage of the centerbody, the fuel supply line having an upstream end disposed at the upstream end of the centerbody and configured for connection to a source of fuel, the fuel supply line having a downstream end disposed at the downstream end of the centerbody;   a primary air flow channel being defined by an annular space between the exterior surface of the centerbody and the inner surface of the peripheral wall;   a premixed pilot nozzle having an upstream end connected to the downstream end of the centerbody, the premixed pilot nozzle having a downstream end disposed axially opposite the upstream end of the premixed pilot nozzle; and   the premixed pilot nozzle further defining a plurality of axially elongated, hollow premix conduits, each premix conduit having an upstream end disposed near the downstream end of the centerbody and defining an entrance opening that communicates fluidly with the interior passage of the centerbody, each premix conduit having at least one fuel hole being connected in fluid communication with the downstream end of the fuel supply line, each premix conduit having a downstream end defining an exit opening that allows fluid to discharge from the hollow premix conduit, each downstream end of each premix conduit defining a central axis that is not parallel to the central axis of the centerbody.   
     
     
         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 centerbody. 
     
     
         3 . The fuel/air nozzle as in  claim 1 , 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 centerbody, 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 centerbody. 
     
     
         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 centerbody. 
     
     
         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 the premixed pilot nozzle defines a pilot fuel nozzle, the pilot fuel nozzle defining an upstream end and a downstream end, the upstream end of the pilot fuel nozzle being connected in fluid communication with the downstream end of the fuel supply line, the downstream end of the pilot fuel nozzle defining at least one fuel jet configured in fluid communication with the upstream end of the pilot fuel nozzle; and
 the premixed pilot nozzle further defining 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 connected 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.   
     
     
         9 . 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:
 an axially elongating peripheral wall defining an outer envelope of the fuel/air nozzle, the peripheral wall having an outer surface and an inner surface facing opposite the outer surface and defining an axially elongating inner cavity; 
 a hollow, axially elongating centerbody disposed within the inner cavity of the fuel/air nozzle and defining a central axis, the centerbody being defined by a centerbody wall defining an upstream end and a downstream end disposed axially opposite the upstream end, the centerbody wall being defined by an exterior surface and an interior surface facing opposite the exterior surface, the interior surface of the centerbody wall defining an axially elongating interior passage disposed concentrically about the central axis of the centerbody; 
 an elongated, hollow fuel supply line extending axially through the interior passage of the centerbody, the fuel supply line having an upstream end disposed at the upstream end of the centerbody and configured for connection to a source of fuel, the fuel supply line having a downstream end disposed at the downstream end of the centerbody; 
 a primary air flow channel being defined by an annular space between the exterior surface of the centerbody and the inner surface of the peripheral wall; 
 a premixed pilot nozzle having an upstream end connected to the downstream end of the centerbody, the premixed pilot nozzle having a downstream end disposed axially opposite the upstream end of the premixed pilot nozzle; and 
 the premixed pilot nozzle further defining a plurality of axially elongated, hollow premix conduits, each premix conduit having an upstream end disposed near the downstream end of the centerbody and defining an entrance opening that communicates fluidly with the interior passage of the centerbody, each premix conduit having at least one fuel hole being connected in fluid communication with the downstream end of the fuel supply line, each premix conduit having a downstream end defining an exit opening that allows fluid to discharge from the hollow premix conduit, each downstream end of each premix conduit defining a central axis that is not parallel to the central axis of the centerbody. 
   
     
     
         10 . The combustor as in  claim 9 , 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 centerbody, the annular channel defining a plurality of air jets. 
     
     
         11 . The combustor as in  claim 9 , wherein at least one of the air jets is disposed nearby 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. 
     
     
         12 . The combustor as in  claim 9 , wherein the annular channel tapers as it proceeds in the downstream direction toward the air jets. 
     
     
         13 . A method of operating a fuel/air nozzle for improved flame stability and NOx in a gas turbine engine, the fuel/air nozzle being defined by a peripheral wall, a hollow centerbody disposed within the peripheral wall and defining a central axis, a swozzle extending from the exterior of the upstream end of the centerbody and radially toward the peripheral wall, and at the downstream end of centerbody a premix pilot nozzle including a plurality of premix conduits having exit openings, the method comprising the steps of:
 delivering a primary flow of air downstream past the swozzle to swirl the primary flow of air;   delivering a primary flow of fuel through the swozzle to mix with the swirled primary flow of air downstream of the swozzle;   delivering a flow of pilot fuel through a hollow fuel supply line to the premix pilot nozzle;   delivering a secondary flow of air downstream through the centerbody to the premix pilot nozzle;   mixing the pilot fuel with the secondary 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 the central axis of the centerbody 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.   
     
     
         14 . The method as in  claim 13 , further comprising the step of 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 centerbody. 
     
     
         15 . The method as in  claim 13 , further comprising the step of diverting some of the secondary flow of air to an annular channel that is disposed radially outwardly from the premix conduits of the premixed pilot nozzle. 
     
     
         16 . The method as in  claim 15 , wherein the pressure of the air expelled from the annular channel exceeds the pressure of the air entering the annular channel. 
     
     
         17 . The method as in  claim 15 , wherein the annular channel tapers as it proceeds in the downstream direction. 
     
     
         18 . The method as in  claim 15 , 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. 
     
     
         19 . The method as in  claim 18 , wherein the air expelled from the annular channel is directed away from the central axis of the centerbody. 
     
     
         20 . A fuel/air nozzle for a gas turbine engine, the fuel/air nozzle comprising:
 an axially elongating peripheral wall defining an outer envelope of the fuel/air nozzle, the peripheral wall having an outer surface and an inner surface facing opposite the outer surface and defining an axially elongating inner cavity;   a hollow, axially elongating centerbody disposed within the inner cavity of the fuel/air nozzle and defining a central axis, the centerbody being defined by a centerbody wall defining an upstream end and a downstream end disposed axially opposite the upstream end, the centerbody wall being defined by an exterior surface and an interior surface facing opposite the exterior surface, the interior surface of the centerbody wall defining an axially elongating interior passage disposed concentrically about the central axis of the centerbody;   an elongated, hollow fuel supply line extending axially through the interior passage of the centerbody, the fuel supply line having an upstream end disposed at the upstream end of the centerbody and configured for connection to a source of fuel, the fuel supply line having a downstream end disposed at the downstream end of the centerbody;   a primary air flow channel being defined by an annular space between the exterior surface of the centerbody and the inner surface of the peripheral wall;   a premixed pilot nozzle having an upstream end connected to the downstream end of the centerbody, the premixed pilot nozzle having a downstream end disposed axially opposite the upstream end of the premixed pilot nozzle;   the premixed pilot nozzle further defining a plurality of axially elongated, hollow premix conduits, each premix conduit having an upstream end disposed near the downstream end of the centerbody and defining an entrance opening that communicates fluidly with the interior passage of the centerbody, each premix conduit defining at least one fuel hole connected in fluid communication with the downstream end of the fuel supply line, each premix conduit having a downstream end defining an exit opening that allows fluid to discharge from the hollow premix conduit, at least each upstream end of each premix conduit defining a central axis configured and disposed so that the flow of fluid that enters the entrance opening of each premix conduit is directed parallel to the central axis of the centerbody; and   an annular channel disposed radially outwardly from the premix conduits, the annular channel being configured to communicate fluidly with the interior passage of the centerbody.   
     
     
         21 . The fuel/air nozzle as in  claim 20 , wherein the upstream end of at least one premix conduit defines a central axis that is not parallel to the central axis of the downstream end of that at least one premix conduit. 
     
     
         22 . The fuel/air nozzle as in  claim 20 , wherein the annular channel defines a plurality of air jets at a downstream end thereof. 
     
     
         23 . The fuel/air nozzle as in  claim 22 , wherein 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 that forms an acute angle with the central axis of the centerbody. 
     
     
         24 . The fuel/air nozzle as in  claim 23 , wherein the central axis of at least one of the air jets directs a flow of air exiting the air jet in a direction away from the central axis of the centerbody. 
     
     
         25 . The fuel/air nozzle as in  claim 20 , wherein the annular channel is configured to taper as it proceeds in the downstream direction toward the air jets. 
     
     
         26 . 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:
 an axially elongating peripheral wall defining an outer envelope of the fuel/air nozzle, the peripheral wall having an outer surface and an inner surface facing opposite the outer surface and defining an axially elongating inner cavity; 
 a hollow, axially elongating centerbody disposed within the inner cavity of the fuel/air nozzle and defining a central axis, the centerbody being defined by a centerbody wall defining an upstream end and a downstream end disposed axially opposite the upstream end, the centerbody wall being defined by an exterior surface and an interior surface facing opposite the exterior surface, the interior surface of the centerbody wall defining an axially elongating interior passage disposed concentrically about the central axis of the centerbody; 
 an elongated, hollow fuel supply line extending axially through the interior passage of the centerbody, the fuel supply line having an upstream end disposed at the upstream end of the centerbody and configured for connection to a source of fuel, the fuel supply line having a downstream end disposed at the downstream end of the centerbody; 
 a primary air flow channel being defined by an annular space between the exterior surface of the centerbody and the inner surface of the peripheral wall; 
 a premixed pilot nozzle having an upstream end connected to the downstream end of the centerbody, the premixed pilot nozzle having a downstream end disposed axially opposite the upstream end of the premixed pilot nozzle; and 
 the premixed pilot nozzle further defining a plurality of axially elongated, hollow premix conduits, each premix conduit having an upstream end disposed near the downstream end of the centerbody and defining an entrance opening that communicates fluidly with the interior passage of the centerbody, each premix conduit being connected in fluid communication with the downstream end of the fuel supply line, each premix conduit having a downstream end defining an exit opening that allows fluid to discharge from the hollow premix conduit, each downstream end of each premix conduit defining a central axis configured and disposed so that the flow of fluid that discharges from exit opening is directed parallel to the central axis of each premix conduit; and 
 an annular channel disposed radially outwardly from the premix conduits, the annular channel being configured to communicate fluidly with the interior passage of the centerbody. 
   
     
     
         27 . The combustor as in  claim 26 , wherein the annular channel defines a plurality of air jets at a downstream end thereof. 
     
     
         28 . The combustor as in  claim 27 , wherein 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 that forms an acute angle with the central axis of the centerbody. 
     
     
         29 . The combustor as in  claim 28 , wherein the central axis of at least one of the air jets directs a flow of air exiting the air jet in a direction away from the central axis of the centerbody. 
     
     
         30 . The combustor as in  claim 26 , wherein the annular channel is configured to taper as it proceeds in the downstream direction toward the air jets. 
     
     
         31 . A method of operating a fuel/air nozzle for a gas turbine engine, the fuel/air nozzle being defined by a peripheral wall, a hollow centerbody disposed within the peripheral wall and defining a central axis, a swozzle extending from the exterior of the upstream end of the centerbody and radially toward the peripheral wall, and at the downstream end of centerbody a premix pilot nozzle including a plurality of premix conduits having exit openings, the method comprising the steps of:
 delivering a primary flow of air downstream past the swozzle to swirl the primary flow of air;   delivering a primary flow of fuel through the swozzle to mix with the swirled primary flow of air downstream of the swozzle;   delivering a flow of pilot fuel through a hollow fuel supply line to the premix pilot nozzle;   delivering a secondary flow of air downstream through the centerbody to the premix pilot nozzle;   mixing the pilot fuel with the secondary flow of air in a plurality of axially elongated, hollow premix conduits that discharge the fuel/air mixture from the downstream end of the premix pilot nozzle;   diverting some of the secondary flow of air to an annular channel that is disposed radially outwardly from the premix conduits of the premixed pilot nozzle; and   expelling the fuel/air mixture from the exit openings of the premix conduits of the premixed pilot nozzle.   
     
     
         32 . The method as in  claim 31 , further comprising the step of expelling the fuel/air mixture from the premix conduits of the premixed pilot nozzle in a direction that is parallel to the central axis of the centerbody. 
     
     
         33 . The method as in  claim 31 , further comprising the step of 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 centerbody. 
     
     
         34 . The method as in  claim 31 , wherein the pressure of the air expelled from the annular channel exceeds the pressure of the air entering the annular channel. 
     
     
         35 . The method as in  claim 31 , wherein the annular channel tapers as it proceeds in the downstream direction. 
     
     
         36 . The method as in  claim 31 , 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.