Annular Premixed Pilot in Fuel Nozzle

Description

FIELD OF THE INVENTION

[0001] The present invention generally involves a gas turbine engine that combusts a hydrocarbon fuel mixed with air to generate a high temperature gas stream that drives turbine blades to rotate a shaft attached to the blades and more particularly to the engine's fuel nozzle having a pilot nozzle that premixes fuel and air while achieving lower nitrogen oxides.

BACKGROUND OF THE INVENTION

[0002] Gas turbine engines are widely used to generate power for numerous applications. A conventional gas turbine engine includes a compressor, a combustor, and a turbine. In a typical gas turbine engine, the compressor provides compressed air to the combustor. The air entering the combustor is mixed with fuel and combusted. Hot gases of combustion are exhausted from the combustor and flow into the blades of the turbine so as to rotate the shaft of the turbine connected to the blades. Some of that mechanical energy of the rotating shaft drives the compressor and/or other mechanical systems.

[0003] As government regulations disfavor the release of nitrogen oxides into the atmosphere, their production as byproducts of the operation of gas turbine engines is sought to be maintained below permissible levels. One approach to meeting such regulations is to move from diffusion flame combustors to combustors that employ lean fuel and air mixtures using a fully premixed operations mode to reduce emissions of, for example, nitrogen oxides (commonly denoted NOx) and carbon monoxide (CO). These combustors are variously known in the art as Dry Low NOx (DLN), Dry Low Emissions (DLE) or Lean Pre Mixed (LPM) combustion systems.

[0004] Fuel-air mixing affects both the levels of nitrogen oxides generated in the hot gases of combustion of a gas turbine engine and the engine's performance. A gas turbine engine may employ one or more fuel nozzles to intake air and fuel to facilitate fuel/air mixing in the combustor. The fuel nozzles may be located in a head end portion of the combustor, and may be configured to intake an air flow to be mixed with a fuel input. Typically, each fuel nozzle may be internally supported by a center body located inside of the fuel nozzle, and a pilot can be mounted at the downstream end of the center body. As described for example in US Patent No. 6,438,961, a so-called swozzle can be mounted to the exterior of the center body and located upstream from the pilot. The swozzle has curved vanes that extend radially from the center body across an annular flow passage and from which fuel is introduced into the annular flow passage to be entrained into a flow of air that is swirled by the vanes of the swozzle. A fuel/air nozzle having the features specified in the preamble of claim 1 and the method for operating said fuel/air nozzle having the features specified in the preamble of claim 10 are known from the patent application US 2011/162371 A1. Various parameters describing the combustion process in the gas turbine engine correlate with the generation of nitrogen oxides. For example, higher gas temperatures in the combustion reaction zone are responsible for generating higher amounts of nitrogen oxides. One way of lowering these temperatures is by premixing the fuel air mixture and reducing the ratio of fuel to air that is combusted. As the ratio of fuel to air that is combusted is lowered, so too the amount of nitrogen oxides is lowered. However, there is a trade-off in performance of the gas turbine engine. For as the ratio of fuel to air that is combusted is lowered, there is an increased tendency of the flame of the fuel nozzle to blow out and thus render unstable the operation of the gas turbine engine. A pilot of a diffusion flame type has been used for better flame stabilization in a combustor, but doing so increases NOx.

BRIEF DESCRIPTION OF THE INVENTION

[0005] Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention.

[0006] In theory, the closer one comes to having at every point in the combustion chamber, a stoichiometric relationship between the fuel and air that undergoes combustion at a given temperature of combustion, the closer one comes to minimizing the generation of nitrogen oxides as byproducts of the combustion. With a fuel nozzle configured as described below, it becomes possible to achieve a more uniform equivalence ratio across the plane of the center body tip of the outer nozzle and thus more closely approximate achieving in the combustion chamber of the gas turbine engine such theoretical conditions of the desired stoichiometric relationship between the fuel and air that undergoes combustion at a given temperature of combustion. Moreover, to overcome one of the drawbacks of a diffusion flame type of pilot, a premix pilot also can be used as a pilot to stabilize the pilot flame, even in low fuel to air ratio to prevent an increase in NOx.

[0007] In one aspect of the invention there is provided 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. According to the invention, each downstream end of each premix conduit defines a central axis that diverges radially outwardly from the central axis of the centerbody. Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 is a block diagram of a turbine system having a fuel nozzle coupled to a combustor in accordance with an embodiment of the present technique;

FIG. 2 is a cross-sectional view of several portions of a combustor in a gas turbine system of the present disclosure;

FIG. 3 depicts an embodiment of components not in accordance with the present invention in a view that is partially in perspective and partially in cross section;

FIG. 4 depicts another embodiment of components not in accordance with the present invention in a cross sectional view;

FIG. 5 is a cross sectional view taken along the sight lines designated 5 - - 5 in FIG. 4;

FIG. 6 depicts an exemplary embodiment of components of the present invention in a cross sectional view;

FIG. 7 depicts another exemplary embodiment of components of the present invention in a cross sectional view;

FIG. 8 depicts in cross section an alternative exemplary embodiment of the section circumscribed by the dashed outline designated by the numeral 8 in FIG. 6;

FIG. 9 depicts another exemplary embodiment of components in a cross sectional view similar to the view shown in FIG. 4;

FIG. 10 schematically represents embodiments of the methods of the present invention for operating a fuel/air nozzle for a gas turbine engine; and

FIG. 11 schematically represents alternative embodiments of the methods of the present invention for operating a fuel/air nozzle for a gas turbine engine.

DETAILED DESCRIPTION OF THE INVENTION

[0009] Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of embodiments of the invention.

[0010] Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

[0011] It is to be understood that the ranges and limits mentioned herein include all sub-ranges located within the prescribed limits, inclusive of the limits themselves unless otherwise stated. For instance, a range from 100 to 200 also includes all possible sub-ranges, examples of which are from 100 to 150, 170 to 190, 153 to 162, 145.3 to 149.6, and 187 to 200. Further, a limit of up to 7 also includes a limit of up to 5, up to 3, and up to 4.5, as well as all sub-ranges within the limit, such as from about 0 to 5, which includes 0 and includes 5 and from 5.2 to 7, which includes 5.2 and includes 7.

[0012] Referring to FIG. 1, a simplified drawing of several portions of a gas turbine system 10 is illustrated. The turbine system 10 may use liquid or gas fuel, such as natural gas and/or a hydrogen rich synthetic gas, to run the turbine system 10. As depicted, a plurality of fuel nozzles 12 of the type described more fully below intakes a fuel supply 14, mixes the fuel with air, and distributes the air-fuel mixture into a combustor 16. The air-fuel mixture combusts in a chamber within the combustor 16, thereby creating hot pressurized exhaust gases. The combustor 16 directs the exhaust gases through a turbine 18 toward an exhaust outlet 20. As the exhaust gases pass through the turbine 18, the gases force one or more turbine blades to rotate a shaft 22 along an axis of the system 10. As illustrated, the shaft 22 may be connected to various components of the turbine system 10, including a compressor 24. The compressor 24 also includes blades that may be coupled to the shaft 22. As the shaft 22 rotates, the blades within the compressor 24 also rotate, thereby compressing air from an air intake 26 through the compressor 24 and into the fuel nozzles 12 and/or combustor 16. The shaft 22 also may be connected to a load 28, which may be a vehicle or a stationary load, such as an electrical generator in a power plant or a propeller on an aircraft, for example. As will be understood, the load 28 may include any suitable device capable of being powered by the rotational output of turbine system 10.

[0013] FIG. 2 is a simplified drawing of cross sectional views of several portions of the gas turbine system 10 schematically depicted in FIG. 1. As schematically shown in FIG. 2, the turbine system 10 includes one or more fuel/air nozzles 12 located in a head end portion 27 of one or more combustors 16 in the gas turbine engine. Each illustrated fuel nozzle 12 may include multiple fuel nozzles integrated together in a group and/or a standalone fuel nozzle, wherein each illustrated fuel nozzle 12 relies at least substantially or entirely on internal structural support (e.g., load bearing fluid passages). Referring to FIG. 2, the system 10 comprises a compressor section 24 for pressurizing a gas, such as air, flowing into the system 10 via air intake 26. In operation, air enters the turbine system 10 through the air intake 26 and may be pressurized in the compressor 24. It should be understood that while the gas may be referred to herein as air, the gas may be any gas suitable for use in a gas turbine system 10. Pressurized air discharged from the compressor section 24 flows into a combustor section 16, which is generally characterized by a plurality of combustors 16 (only one of which is illustrated in FIGs. 1 and 2) disposed in an annular array about an axis of the system 10. The air entering the combustor section 16 is mixed with fuel and combusted within the combustion chamber 32 of the combustor 16. For example, the fuel nozzles 12 may inject a fuel/air mixture into the combustor 16 in a suitable fuel-air ratio for optimal combustion, emissions, fuel consumption, and power output. The combustion generates hot pressurized exhaust gases, which then flow from each combustor 16 to a turbine section 18 (FIG. 1) to drive the system 10 and generate power. The hot gases drive one or more blades (not shown) within the turbine 18 to rotate the shaft 22 and, thus, the compressor 24 and the load 28. The rotation of the shaft 22 causes blades 30 within the compressor 24 to rotate and draw in and pressurize the air received by the intake 26. It readily should be appreciated, however, that a combustor 16 need not be configured as described above and illustrated herein and in general may have any configuration that permits pressurized air to be mixed with fuel, combusted and transferred to a turbine section 18 of the system 10.

[0014] FIGs. 3 - 9 schematically illustrate various embodiments of fuel/air nozzles 12. In each of FIGs. 4, 8 and 9 for example, at least each upstream end of each premix conduit 41 defines a central axis 41d configured and disposed so that the flow of fluid that enters the entrance opening 66a of each premix conduit 41 is directed parallel to the central axis 36 of the centerbody 52. In each of FIGs. 6 and 7 for example, at least each upstream end of each premix conduit 41 defines a central axis 41d configured and disposed so
that the flow of fluid that enters the entrance opening 66a of each premix conduit 41 is directed at an acute angle away from the central axis 36 of the centerbody 52 in the range of 0.1 degrees to twenty degrees. As schematically shown in FIG. 3 for example, one embodiment of the fuel/air nozzle 12 includes premix conduits 41 that are configured with concentric axes that are parallel to the burner tube axis 36 to direct the fuel/air mixture axially from the premixed pilot nozzle 40. In the embodiments that are schematically shown in FIGs. 4, 5 and 9, there is at least one air jet 42 beside each of the premix conduits 41 wherein each of the air jets 42 can entrain some portion of fuel/air mixture to direct the mixture radially outwardly from the premix conduits 41 to form a more uniform fuel/air mixture in the burn exit plane 44 of the nozzle 12 and into the combustion chamber 32 of the combustor 16 (FIGs. 1 and 2). In the embodiment depicted in FIGs. 4 and 5, each of the air jets 42 desirably is directed radially outwardly from the premix conduits 41 so that each of the air jets 42 more readily can entrain more of the fuel/air mixture to direct more of the mixture radially outwardly from the premix conduits 41 to form a more uniform fuel/air mixture in the burn exit plane 44 of the nozzle 12 and into the combustion chamber 32 of the combustor 16 (FIGs. 1 and 2).

[0015] As schematically shown in FIG. 3 for example, a fuel/air nozzle 12 for a gas turbine engine desirably includes an axially elongating peripheral wall 50 defining an outer envelope of the nozzle 12. The peripheral wall 50 of fuel/air nozzle 12 has an outer surface 50a and an inner surface 50b facing opposite the outer surface 50a and defining an axially elongating inner cavity 50c.

[0016] As schematically shown in FIG. 3 for example, a fuel/air nozzle 12 for a gas turbine engine desirably includes a hollow, axially elongating centerbody 52 disposed within the inner cavity 50c of the fuel/air nozzle 12 and defining a central axis 36, which is the same as the central axis of the burner tube. The centerbody 52 is defined by a centerbody wall 52a that defines an upstream end 52b and a downstream end 52c disposed axially opposite the upstream end 52b. The centerbody wall 52a is defined by an exterior surface 52d and an interior surface 52e facing opposite the exterior surface 52d. The interior surface 52d of the centerbody wall 52a defines an axially elongating interior passage 53 that is disposed concentrically about the central axis 36 of the centerbody 52. A primary air flow channel 51 is defined in the annular space between the inner surface 50b of the peripheral wall 50 and the exterior surface 52d of the centerbody wall 52a.

[0017] As schematically shown in FIG. 3 for example, a fuel/air nozzle 12 for a gas turbine engine desirably includes an axially elongated, hollow fuel supply line 54 extending axially through the interior passage 53 of the centerbody 52. The fuel supply line 54 has an upstream end 54a that is disposed at the upstream end 52b of the centerbody 52 and that is configured for connection to a source of fuel (not shown). The fuel supply line 54 has a downstream end 54b that is disposed at the downstream end 52c of the centerbody 52. A secondary air flow channel is defined by an annular space between the interior surface 52e of the centerbody 52 and the exterior surface of the fuel supply line 54, and that annular space defines the axially elongating interior passage 53 schematically shown in FIG. 3.

[0018] As schematically shown in FIG. 3, the primary fuel may be supplied to the combustion chamber 32 of the combustor 16 (FIG. 2) through a plurality of air swirler vanes 56 that are fixed and extend across the flow path of the primary air flow channel 51. These air swirler vanes 56 define a so-called swozzle that extends radially from the exterior surface of centerbody wall 52a. As schematically shown in FIG. 3, each of the air swirler vanes 56 of the swozzle desirably is provided with internal fuel conduits 57 that terminate in fuel injection ports or holes 58 from which primary fuel (indicated by the arrows designated by the numeral 57a) flowing from the conduits 57 can be injected into the primary air (indicated by the arrows designated by the numeral 51a) that flows past the fuel injection ports 58 in the air swirler vanes 56. As primary air flow 51a is directed against the air swirler vanes 56, a swirling pattern is imparted to the primary air flow 51a that facilitates the mixing of the primary air flow 51a with the primary fuel that is ejected from the holes 58 of the air swirler vanes 56 into the passing primary air flow 51a. The primary air flow 51a mixed with the primary fuel then may flow into the pre-mixing annulus 51 that is defined between the peripheral wall 50 and the inner centerbody 52, wherein the primary air flow 51a and the primary fuel continue to mix together prior to entering the combustion chamber 32.

[0019] As schematically shown in FIG. 3 for example, a fuel/air nozzle 12 for a gas turbine engine desirably includes a premixed pilot nozzle 40 that has an upstream end 40a connected to the downstream end 52c of the centerbody 52. In the embodiment depicted in FIG. 3, the downstream end 52c of the centerbody 52 and the upstream end 40a of the premixed pilot nozzle 40 are defined in part by different sections of the metal cylinder that forms the centerbody 52 and the outermost wall that defines the premixed pilot nozzle 40. The premixed pilot nozzle 40 has a downstream end 40b disposed axially opposite the upstream end 40a of the premixed pilot nozzle 40.

[0020] As schematically shown in FIGs. 3, 4 and 9 for example, the premixed pilot nozzle 40 defines a pilot fuel nozzle 60, which defines an upstream end 60a and a downstream end 60b. As schematically shown in FIGs. 4 and 9 for example, the upstream end 60a of the pilot fuel nozzle 60 is connected in fluid communication with the downstream end 54b of the fuel supply line 54. The downstream end 60b of the pilot fuel nozzle 60 defines at least one fuel jet 61 configured in fluid communication with the upstream end 60a of the pilot fuel nozzle 60. As schematically shown by the arrows designated 62 in FIGs. 4 and 9 for example, fuel 62 entering the pilot fuel nozzle 60 via the downstream end 54b of the fuel supply line 54 exits the pilot fuel nozzle 60 via a plurality of fuel jets 61 (shown in dashed line in FIG. 5).

[0021] As schematically shown in FIGs. 3, 4 and 9 for example, the premixed pilot nozzle 40 further defines an annular-shaped fuel plenum wall 63 disposed radially outwardly from the pilot fuel nozzle 60 and desirably concentrically with respect to the burner tube axis 36 shown in FIG. 3. As schematically shown in FIGs. 3, 4 and 9 for example, the fuel plenum wall 63 defines a fuel plenum 64 between the pilot fuel nozzle 60 and the fuel plenum wall 63. As schematically shown in FIGs. 4 and 9 for example, the fuel plenum wall 63 further defines a plurality of fuel holes 63a through which fuel is discharged from the fuel plenum 64. As schematically shown in FIGs. 4 and 9 for example, at least one of the fuel holes 63a is connected in fluid communication with at least one of the fuel jets 61 via the fuel plenum 64. Desirably, each of the fuel holes 63a is connected in fluid communication with each of the fuel jets 61 via the fuel plenum 64.

[0022] As schematically shown in FIGs. 3, 4 and 9 for example, the premixed pilot nozzle 40 further defines a plurality of axially elongated, hollow premix conduits 41 disposed radially outwardly from the fuel plenum wall 63. As schematically shown in the embodiment depicted in FIGs. 4 and 9 for example, each of the premix conduits 41 desirably is defined in part by the plenum wall 63. As schematically shown in FIG. 3 for example, each premix conduit 41 has an upstream end 41a that is disposed near the downstream end 52c of the centerbody 52. As schematically shown in FIGs. 4 and 9 for example, each premix conduit 41 defines at its upstream end 41a an entrance opening 66a that communicates fluidly with the interior passage 53 of the centerbody 52. The arrows designated 53a in FIGs. 4 and 9 schematically indicate the flow of air 53a that enters the entrance opening 66a of each premix conduit 41 from the interior passage 53 of the centerbody 52.

[0023] As schematically shown in FIGs. 4 and 9 for example, each premix conduit 41 is connected in fluid communication with at least one of the fuel holes 63a that is defined in the fuel plenum wall 63 of the fuel plenum 64. The arrows designated 62a in FIGs. 4 and 9 schematically indicate the flow of fuel 62a that exits from the fuel plenum 64 through the fuel holes 63a defined in the fuel plenum wall 63 and passes into each premix conduit 41. The arrows designated 62b in FIGs. 4 and 9 schematically indicate the flow of the fuel-air mix 62b that travels downstream in the premix conduits 41 of the premixed pilot nozzle 40.

[0024] As schematically shown in FIGs. 4 and 9 for example, each premix conduit 41 has a downstream end 41b that is disposed axially opposite the upstream end 41a of the premix conduit 41 and that is disposed near the downstream end 40b of the premixed pilot nozzle 40. As schematically shown in FIGs. 4 and 9 for example, each downstream end 41b of each premix conduit 41 defines an exit opening 66b that allows fluid, i.e., the fuel-air mix 62b, to discharge from the hollow premix conduit 41. As schematically shown in FIGs. 4 and 9 for example, each downstream end 41b of each premix conduit 41 defines a central axis 41c, and the walls that define each premix conduit 41 are disposed concentrically about this central axis 41c. Moreover, as schematically shown for the embodiment of the premixed pilot nozzle 40 depicted in FIGs. 4 and 9 for example, each central axis 41c is a straight line that is disposed so that the flow of the fluid that is the mix of fuel and air that discharges from the exit opening 66b of each premix conduit 41 is directed parallel to the central axis 36 of the centerbody 52.

[0025] While the fuel-air mix 62b tends to spread radially from each central axis 41c once the fuel-air mix 62b leaves the exit opening 66b of each premix conduit 41, applicants have shown that the radial spread is not very significant. Indeed, applicants' studies have shown that the equivalence ratio at the section of the burn exit plane 44 (FIGs. 4 and 9) that is located immediately downstream of the exit opening 66b of each premix conduit 41 can be almost twice the equivalence ratio that exists at the section of the burn exit plane 44 (FIGs. 4 and 9) that is located immediately downstream of the central axis 36 of the centerbody 52. High equivalence ratio at a location that is immediately downstream of the exit opening 66b of each premix conduit 41 can continuously and effectively light the fuel/air mixture through the axially elongating inner cavity 50c (FIG. 3) and can make the flame stable even if the flame is at lean-blow-out (LBO) condition. This is one of the important roles of a premix pilot, and the premix pilot 60 fulfills this role without an increase of NOx.

[0026] Various embodiments of the present invention include features that counteract this much higher equivalence ratio that exists at the section of the burn exit plane 44 (FIGs. 4 and 9) that is located immediately downstream of the exit opening 66b of each premix conduit 41. As schematically shown for the embodiments of the premixed pilot nozzle 40 that are depicted in FIGs. 3, 4, 5 and 9 for example, the premixed pilot nozzle 40 further defines an annular channel 70 that is disposed radially outwardly from the premix conduits 41. In the embodiments that are depicted in FIGs. 3, 4, 5 and 9 for example, the inner wall 43 of the annular channel 70 also serves to define the outer wall 43 of the premix conduits 41. In the embodiments that are depicted in FIGs. 3, 4, 5 and 9 for example, the centerbody wall 52a also serves to define the outer wall 52a of the annular channel 70.

[0027] As schematically shown for the embodiments of the premixed pilot nozzle 40 that are depicted in FIGs. 3, 4 and 9 for example, the upstream end of the annular channel 70 is configured to communicate fluidly with the interior passage 53 of the centerbody 52 and thus receives a flow of air from the interior passage 53 of the centerbody 52. At the downstream end of the annular channel 70, a plurality of air jets 42 is defined. At least one of the air jets 42 is disposed nearby at least one of the exit openings 66b of at least one of the premix conduits 41. Desirably, as shown in FIGs. 4, 5 and 9 for example, at least one of the air jets 42 is disposed nearby each of the exit openings 66b of each one of the premix conduits 41.

[0028] As schematically shown in FIG. 9 for example, each of the passages that defines one of the air jets 42 is defined concentrically around a central axis 42a that is disposed parallel to the central axis 41c of the downstream end 41b of the nearby premix conduit 41. In so doing, the higher velocity air leaving each air jets 42 entrains some of the fuel/air mixture leaving the premix conduits 41 and serves to direct the fuel/air mixture that exists at the section of the burn exit plane 44 (FIG. 9) that is located immediately downstream of the exit opening 66b of each premix conduit 41. The overall result is a more uniform equivalence ratio at the burn exit plane 44 (FIG. 9) of the fuel-air nozzle 12, and this also can be used by lighting source as a pilot.

[0029] As schematically shown in FIG. 4 for example, each of the passages that defines one of the air jets 42 is defined concentrically around a central axis 42a that is disposed at an acute angle with respect to the central axis 41c of the downstream end 41b of the nearby premix conduit 41. The magnitude of this acute angle desirably is in the range of 0.1 degrees to twenty degrees. Moreover, the air jet 42 in the FIG. 4 embodiment desirably is configured and disposed so that the respective air jet 42 directs the flow of air exiting the air jet 42 in a direction away from the nearby one of the exit openings 66b of the premix conduits 41. Thus, in the embodiment schematically shown in FIG. 4 for example, each air jet 42 is pointed so that the air leaving that air jet 42 moves in a direction that is both downstream and radially away from the central axis 36 of the centerbody 52 as well as radially away from the central axis 41c of downstream end 41b of the respective nearby premix conduit 41. In so doing, the air leaving each air jets 42 entrains some of the fuel/air mixture leaving the premix conduits 41 and serves to direct the fuel/air mixture that exists at the section of the burn exit plane 44 (FIG. 4) that is located immediately downstream of the exit opening 66b of each premix conduit 41 radially outwardly toward the peripheral wall 50 (FIG. 3). The overall result is a more uniform equivalence ratio at the burn exit plane 44 (FIG. 4) of the fuel-air nozzle 12, and this also can be used by lighting source as a pilot.

[0030] In another embodiment of the present invention depicted schematically in FIG. 6 for example, with the exception of the embodiment of the premixed pilot nozzle 40 that is depicted schematically in FIG. 6, the embodiment of FIG. 6 is like the embodiment of FIGs. 3, 4, 5 and 9. As schematically in FIG. 6, each of the premix conduits 41 is itself configured concentrically about a central longitudinal axis 41c that is disposed at an acute angle with respect to the central axis 36 of the centerbody 52. The magnitude of this acute angle desirably is in the range of 0.1 degrees to twenty degrees. Thus, in the premixed pilot nozzle 40 that is depicted schematically in FIG. 6, each of the premix conduits 41 is configured and disposed so as to direct the fuel/air mixture exiting from the exit opening 66b of each premix conduit 41 radially outwardly away from the central axis 36 of the centerbody 52 so as to form a more uniform fuel/air mixture in the burn exit plane 44 of the fuel-air nozzle 12 and into the combustion chamber of a gas turbine 10 and so as to continuously and effectively light the fuel/air mixture that is supplied through an axially elongating inner cavity 50c (FIG. 3) of the fuel-air nozzle 12. Though not specifically illustrated in FIG. 6 for example, the axial length of one or more of the premix conduits 41 can extend beyond the downstream end 40b of the premixed pilot nozzle 40 in a manner concentrically around the central axis 41c of the downstream end 41b of premix conduit 41.

[0031] In another embodiment of the present invention depicted schematically in FIG. 8 for example, with the exception of the embodiment of the premix conduits 41 of the premixed pilot nozzle 40 that is depicted schematically in FIG. 6, the embodiment of FIG. 8 is like the embodiment of FIGs. 3, 4, 5, 6 and 9. In the embodiment depicted schematically in FIG. 8, each of the premix conduits 41 is itself configured concentrically about a bi-directed central longitudinal axis having a first leg 41d and a second leg 41c. As schematically in FIG. 8, the first leg 41d of the bi-directed central longitudinal axis is disposed parallel to the central axis 36 of the centerbody 52 and extends between the upstream end 41a and the downstream end 41b of each premix conduit 41. A second leg 41c of the bi-directed central longitudinal axis is disposed at an acute angle with respect to the central axis 36 of the centerbody 52 and extends through the downstream end 41b of each premix conduit 41. The magnitude of this acute angle desirably is in the range of 0.1 degrees to twenty degrees. Thus, the premix conduit 41 that is depicted schematically in FIG. 8 is configured and disposed so as to direct the fuel/air mixture exiting from the exit opening 66b radially outwardly away from the central axis 36 of the centerbody 52 so as to form a more uniform fuel/air mixture in the burn exit plane 44 of the fuel-air nozzle 12 and into the combustion chamber of a gas turbine 12 and so as to continuously and effectively light the fuel/air mixture that is supplied through an axially elongating inner cavity 50c (FIG. 3) of the fuel-air nozzle 12.

[0032] In another embodiment of the present invention depicted schematically in FIG. 7 for example, with the exception of the embodiment of the premix conduits 41 and annular channel 70 of the premixed pilot nozzle 40 that is depicted schematically in FIGs. 3, 4, 5 and 9, the embodiment of FIG. 7 is like the embodiments of FIGs. 3, 4, 5 and 9. As schematically in FIG. 7, each of the premix conduits 41 is itself configured concentrically about a central longitudinal axis 41c that is disposed at an acute angle with respect to the central axis 36 of the centerbody 52. The magnitude of this acute angle desirably is in the range of 0.1 degrees to twenty degrees. Thus, in the premixed pilot nozzle 40 that is depicted schematically in FIG. 7, each of the premix conduits 41 is configured and disposed so as to direct the fuel/air mixture exiting from the exit opening 66b of each premix conduit 41 radially outwardly away from the central axis 36 of the centerbody 52 so as to form a more uniform fuel/air mixture in the burn exit plane 44 of the fuel-air nozzle 12 and into the combustion chamber of a gas turbine 10 and so as to continuously and effectively light the fuel/air mixture that is supplied through an axially elongating inner cavity 50c (FIG. 3) of the fuel-air nozzle 12.

[0033] As schematically shown for the embodiment of the premixed pilot nozzle 40 that is depicted in FIG. 7 for example, the upstream end of the annular channel 70 is configured to taper as it proceeds in the downstream direction toward the air jets 42 that are disposed beside each of the exit openings of premix conduits 41. As described above with regard to the embodiment of FIGs. 3, 4 and 5, each of the air jets 42 is directed radially outwardly from the premix conduits 41 so that each of the air jets 42 can entrain some portion of fuel/air mixture to further direct the mixture radially outwardly from the premix conduits 41 to form a more uniform fuel/air mixture in the burn exit plane 44 of the fuel-air nozzle 12 and into the combustion chamber 32 of a combustor 16 (FIGs. 1 and 2) and to continuously and effectively light the fuel/air mixture that is supplied through an axially elongating inner cavity 50c (FIG. 3) of the fuel-air nozzle 12.

[0034] Each embodiment of the premixed pilot nozzle 40 provides a small well anchored premixed flame near the base of the fuel-air nozzle 12, thus anchoring the swirling fuel air mixture exiting the fuel-air nozzle 12. The improved flame stability enables lower fuel/air operations, thus extending LBO and the emissions operability window.

[0035] With fuel/air nozzles 12 such as the embodiments described above, it becomes feasible to implement advantageous methods of operating a fuel/air nozzle 12 for a gas turbine engine 10. One embodiment of such a method of operating a fuel/air nozzle 12 for a gas turbine engine 10 desirably includes the following steps schematically shown in FIG. 10: the step 81 of delivering a primary flow of air 51a (e.g., FIG. 3) downstream past the swozzle to swirl the primary flow of air; the step 82 of delivering a primary flow of fuel 57a (e.g., FIG. 3) through the swozzle to mix with the swirled primary flow of air 51a downstream of the swozzle; the step 83 of delivering a flow of pilot fuel 62 (e.g., FIG. 4) through a hollow fuel supply line 54 to the premix pilot nozzle 40; the step 84 of delivering a secondary flow of air 53a (e.g., FIG. 4) downstream through the centerbody 52 (e.g., FIG. 3) to the premix pilot nozzle 40; the step 85 of mixing the pilot fuel 62 with the secondary flow of air 53a in a plurality of axially elongated, hollow premix conduits 41 (e.g., FIG. 4) that discharge the fuel/air mixture 62b (e.g., FIGs. 4 and 9) from the downstream end 41b of the premix pilot nozzle 40; and the step 86 of expelling the fuel/air mixture 62b from the premix conduits 41 of the premixed pilot nozzle 40 away from the central axis 36 of the centerbody 52 (e.g., FIGs. 3, 4 and 6 - 9).

[0036] Another embodiment of such a method of operating a fuel/air nozzle 12 for a gas turbine engine 10 desirably includes the following steps schematically shown in FIG. 11: the step 81 of delivering a primary flow of air 51a (e.g., FIG. 3) downstream past the swozzle to swirl the primary flow of air; the step 82 of delivering a primary flow of fuel 57a (e.g., FIG. 3) through the swozzle to mix with the swirled primary flow of air 51a downstream of the swozzle; the step 83 of delivering a flow of pilot fuel 62 (e.g., FIG. 4) through a hollow fuel supply line 54 to the premix pilot nozzle 40; the step 84 of delivering a secondary flow of air 53a (e.g., FIG. 4) downstream through the centerbody 52 (e.g., FIG. 3) to the premix pilot nozzle 40; the step 85 of mixing the pilot fuel 62 with the secondary flow of air 53a in a plurality of axially elongated, hollow premix conduits 41 (e.g., FIG. 4) that discharge the fuel/air mixture 62b (e.g., FIGs. 4 and 9) from the downstream end 41b of the premix pilot nozzle 40; the step 87 of diverting some of the secondary flow of air 53a (e.g., FIGs. 4, 7 and 9) to an annular channel 70 that is disposed radially outwardly from the premix conduits 41 of the premixed pilot nozzle 40; and the step 88 of expelling air from the annular channel 70 away from the premixed pilot nozzle 40 (e.g., FIGs. 4, 7 and 9). Desirably, the pressure of the air expelled from the annular channel 70 exceeds the pressure of the air entering the annular channel 70. Desirably, as schematically shown in FIG. 7 for example, the annular channel 70 includes an upstream end that is configured to taper as it proceeds in the downstream direction. Desirably, as schematically shown in FIG. 7 for example, a further embodiment of the method comprises the step of expelling the fuel/air mixture from the premix conduits 41 of the premixed pilot nozzle 40 away from the central axis 36 of the centerbody 52. Desirably, as schematically shown in FIG. 4 for example, a further embodiment of the method comprises the step of expelling the fuel/air mixture 62b from the premix conduits 41 of the premixed pilot nozzle 40 in a direction that is parallel to the central axis 36 of the centerbody 52. Desirably, as schematically shown in FIGs. 4 and 7 for example, a further embodiment of the method comprises the step of expelling the fuel/air mixture 62b from the annular channel 70 in a direction that is radially away from the central axis 36 of the centerbody 52.

[0037] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other and examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

1. A fuel/air nozzle (12) for a gas turbine engine (10), the fuel/air nozzle comprising:

an axially elongating peripheral wall (50) defining an outer envelope of the fuel/air nozzle (12), the peripheral wall (50) having an outer surface (50a) and an inner surface (50b) facing opposite the outer surface (50a) and defining an axially elongating inner cavity (50c);

a hollow, axially elongating centerbody (52) disposed within the inner cavity (50c) of the fuel/air nozzle (12) and defining a central axis, the centerbody being defined by a centerbody wall (52a) defining an upstream end (52b) and a downstream end (52c) disposed axially opposite the upstream end (52b), the centerbody wall (52a) being defined by an exterior surface (52a) and an interior surface (52e) facing opposite the exterior surface (52d), the interior surface (52e) of the centerbody wall (52a) defining an axially elongating interior passage (53) disposed concentrically about the central axis of the centerbody (52);

an elongated, hollow fuel supply line (54) extending axially through the interior passage (53) of the centerbody (52), the fuel supply line (54) having an upstream end (54a) disposed at the upstream end (52b) of the centerbody (52) and configured for connection to a source of fuel (14), the fuel supply line (54) having a downstream end (54b) disposed at the downstream end (52c) of the centerbody (52);

a primary air flow channel (51) being defined by an annular space between the exterior surface (52a) of the centerbody (52) and the inner surface (50b) of the peripheral wall (50);

a premixed pilot nozzle (40) having an upstream end (40a) connected to the downstream end (52c) of the centerbody (52), the premixed pilot nozzle (40) having a downstream end (40b) disposed axially opposite the upstream end (40a) of the premixed pilot nozzle (40); and

the premixed pilot nozzle (40) further defining a plurality of axially elongated, hollow premix conduits (41), each premix conduit (41) having an upstream end (41a) disposed near the downstream end (52c) of the centerbody (52) and defining an entrance opening that communicates fluidly with the interior passage (53) of the centerbody (52), each premix conduit (41) having at least one fuel hole (63a) being connected in fluid communication with the downstream end (54b) of the fuel supply line (54), each premix conduit (41) having a downstream end (41b) defining an exit opening (66b) that allows fluid to discharge from the hollow premix conduit (41), characterized in that each downstream end (41b) of each premix conduit (41) defines a central axis (41c) that diverges radially outwardly from the central axis of the centerbody (52).

2. The fuel/air nozzle as in claim 1, wherein each central axis (41c) of at least one premix conduit (41) is disposed at an acute angle with respect to the central axis of the centerbody (52).

3. The fuel/air nozzle as in claim 1 or 2, wherein the premixed pilot nozzle (40) further defines an annular channel (70) disposed radially outwardly from the premix conduits (41), the annular channel (70) being configured to communicate fluidly with the interior passage (53) of the centerbody (52), the annular channel (70) defining a plurality of air jets (61), at least one of the air jets (61) being disposed nearby one of the exit openings (66b) of at least one of the premix conduits (41) and having a central axis.

4. The fuel/air nozzle as in claim 3, wherein the central axis (41d) of the upstream end (41a) of at least one premix conduit (41) is configured and disposed to extend in a direction parallel to the central axis of the centerbody (52).

5. The fuel/air nozzle as in claim 3 or 4, wherein the central axis (42a) of at least one of the air jets (42) forms an acute angle with the central axis of the centerbody.

6. The fuel/air nozzle as in any of claims 3 to 5, wherein the annular channel (70) is configured to taper as it proceeds in the downstream direction toward the air jets (61).

7. The fuel/air nozzle as in any preceding claim, further comprising a swozzle including a plurality of swirl blades (56) extending radially across the primary air flow channel (51), at least one of the swirl blades (56) defining a fuel conduit (57) having an inlet at one end thereof and an outlet at an opposite end thereof in fluid communication with the primary air flow channel (51).

8. The fuel/air nozzle as in any preceding claim, wherein the premixed pilot nozzle (40) defines a pilot fuel nozzle (60), the pilot fuel nozzle (60) defining an upstream end (60a) and a downstream end (60b), the upstream end (60c) of the pilot fuel nozzle (60) being connected in fluid communication with the downstream end (54b) of the fuel supply line (54), the downstream end (60b) of the pilot fuel nozzle (60) defining at least one fuel jet (61) configured in fluid communication with the upstream end (60a) of the pilot fuel nozzle (60); and
the premixed pilot nozzle (40) further defining a fuel plenum wall (63) disposed radially outwardly from the pilot fuel nozzle (60) and defining a fuel plenum (64) between the pilot fuel nozzle (60) and the fuel plenum wall (63), the fuel plenum wall (63) further defining a plurality of fuel holes (63a), at least one of the fuel holes (63c) being connected in fluid communication with at least one of the fuel jets (61) via the fuel plenum (64), each premix conduit (41) being disposed radially outwardly from the fuel plenum wall (43) and in fluid communication with at least one of the fuel holes (63a).

9. A combustor (16) for a gas turbine engine (10), the combustor comprising:

a head end portion (27); and

at least one fuel/air nozzle (12) carried by the head portion (27), the at least one fuel/air nozzle as recited in any of claims 1 to 8.

10. A method of operating a fuel/air nozzle (12) for improved flame stability and NOx in a gas turbine engine (10), the fuel/air nozzle (12) being defined by a peripheral wall (50), a hollow centerbody (52) disposed within the peripheral wall (50) and defining a central axis, a swozzle extending from the exterior (52d) of the upstream end (52b) of the centerbody (52) and radially toward the peripheral wall (50), and at the downstream end (52c) of centerbody (52) a premix pilot nozzle (40) including a plurality of premix conduits (41) having exit openings (66b), the method comprising the steps of:

delivering (81) a primary flow of air (51) downstream past the swozzle to swirl the primary flow of air (51);

delivering (82) a primary flow of fuel through the swozzle to mix with the swirled primary flow of air (51) downstream of the swozzle;

delivering (83) a flow of pilot fuel through a hollow fuel supply line (54) to the premix pilot nozzle (40);

delivering (84) a secondary flow of air downstream through the centerbody (52) to the premix pilot nozzle (40);

mixing (85) the pilot fuel with the secondary flow of air in a plurality of axially elongated, hollow premix conduits (41), characterized in that each premix conduit (41) defines a central axis at the downstream end (41b) thereof that diverges radially outward from the central axis of the centerbody (52) and that discharges the fuel/air mixture from the downstream end (40b) of the premix pilot nozzle (40); and that the method further comprises the step of expelling the fuel/air mixture from the exit openings (66b) of the premix conduits (41) of the premixed pilot nozzle (40).

11. The method as in claim 10, further comprising the step of diverting some of the secondary flow of air to an annular channel (70) that is disposed radially outwardly from the premix conduits (41) of the premixed pilot nozzle (40).

12. The method as in claim 11, wherein the pressure of the air expelled from the annular channel (70) exceeds the pressure of the air entering the annular channel (70).

13. The method as in claim 11 or 12, wherein the annular channel (70) tapers as it proceeds in the downstream direction.

14. The method as in any of claims 11 to 13, further comprising the step of expelling air from the annular channel (70) of the premixed pilot nozzle (40) in a direction that is away from the exit openings (66b) of the premix conduits (41).

15. The method as in claim 14, wherein the air expelled from the annular channel (70) is directed away from the central axis of the centerbody (52).

Ansprüche

1. Kraftstoff-/Luftdüse (12) für ein Gasturbinentriebwerk (10), wobei die Kraftstoff-/Luftdüse umfasst:

eine sich axial erstreckende Umfangswand (50), die eine Außenhülle der Kraftstoff-/Luftdüse (12) definiert, wobei die Umfangswand (50) eine äußere Oberfläche (50a) und eine innere Oberfläche (50b) aufweist, die der äußeren Oberfläche (50a) gegenüberliegt und einen sich axial erstreckenden Hohlraum (50c) definiert;

einen hohlen, sich axial erstreckenden Mittelkörper (52), der in dem inneren Hohlraum (50c) der Kraftstoff-/Luftdüse (12) angeordnet ist und eine Mittelachse definiert, wobei der Mittelkörper durch eine Mittelkörperwand (52a) definiert ist, die ein stromaufwärtiges Ende (52b) und ein stromabwärtiges Ende (52c) definiert, das axial gegenüber des stromabwärtigen Endes (52b) angeordnet ist, wobei die Mittelkörperwand (52a) durch eine externe Oberfläche (52a) und eine interne Oberfläche (52e) definiert wird, die der externen Oberfläche (52d) gegenüberliegt, wobei die interne Oberfläche (52e) der Mittelkörperwand (52a) einen sich axial erstreckenden internen Durchgang (53) definiert, der konzentrisch um die Mittelachse des Mittelkörpers (52) angeordnet ist;

eine langgestreckte, hohle Kraftstoffzufuhrleitung (54), die sich axial durch den internen Durchgang (53) des Mittelkörpers (52) erstreckt, wobei die Kraftstoffzufuhrleitung (54) ein stromaufwärtiges Ende (54a) aufweist, das am stromaufwärtigen Ende (52b) des Mittelkörpers (52) angeordnet ist und zur Verbindung mit einer Kraftstoffquelle (14) konfiguriert ist, wobei die Kraftstoffzufuhrleitung (54) ein stromabwärtiges Ende (54b) aufweist, das am stromabwärtigen Ende (52c) des Mittelkörpers (52) angeordnet ist;

einen Primärluftströmungskanal (51), der durch einen ringförmigen Raum zwischen der externen Oberfläche (52a) des Mittelkörpers (52) und der inneren Oberfläche (50b) der Umfangswand (50) definiert ist;

eine Vormischungspilotdüse (40), die ein stromaufwärtiges Ende (40a) aufweist, das mit dem stromabwärtigen Ende (52c) des Mittelkörpers (52) verbunden ist, wobei die Vormischungspilotdüse (40) ein stromabwärtiges Ende (40b) axial gegenüber dem stromaufwärtigen Ende (40a) der Vormischungspilotdüse (40) aufweist; und

die Vormischungspilotdüse (40) weiter eine Vielzahl von axial langgestreckten, hohlen Vormischkanälen (41) definiert, wobei jeder Vormischkanal (41) ein stromaufwärtiges Ende (41a) nahe dem stromabwärtigen Ende (52c) des Mittelkörpers (52) aufweist und eine Eintrittsöffnung definiert, die fluidisch mit dem internen Durchgang (53) des Mittelkörpers (52) verbunden ist, wobei jeder Vormischkanal (41) mindestens ein Kraftstoffloch (63a) in Fluidverbindung mit dem stromabwärtigen Ende (54b) der Kraftstoffzufuhrleitung (54) aufweist, wobei jeder Vormischkanal (41) ein stromabwärtiges Ende (41b) aufweist, das eine Austrittsöffnung (66b) definiert, die es Fluid ermöglicht, aus dem hohlen Vormischkanal (41) abgegeben zu werden, dadurch gekennzeichnet, dass jedes stromabwärtige Ende (41b) jedes Vormischkanals (41) eine Mittelachse (41c) definiert, die radial nach außen von der Mittelachse des Mittelkörpers (52) divergiert.

2. Kraftstoff-/Luftdüse nach Anspruch 1, wobei jede Mittelachse (41c) von mindestens einem Vormischkanal (41) in einem spitzen Winkel in Bezug auf die Mittelachse des Mittelkörpers (52) angeordnet ist.

3. Kraftstoff-/Luftdüse nach Anspruch 1 oder 2, wobei die Vormischungspilotdüse (40) weiter einen ringförmigen Kanal (70) definiert, der radial nach außen von den Vormischkanälen (41) angeordnet ist, wobei der ringförmige Kanal (70) zum fluidischen Verbinden mit dem internen Durchgang (53) des Mittelkörpers (52) konfiguriert ist, wobei der ringförmige Kanal (70) eine Vielzahl von Luftstrahlen (61) definiert, wobei mindestens einer der Luftstrahlen (61) nahe einer der Austrittsöffnungen (66b) von mindestens einem der Vormischkanäle (41) angeordnet ist und eine Mittelachse aufweist.

4. Kraftstoff-/Luftdüse nach Anspruch 3, wobei die Mittelachse (41d) des stromaufwärtigen Endes (41a) von mindestens einem Vormischkanal (41) konfiguriert und angeordnet ist, um sich in einer Richtung zu erstrecken, die parallel zu der Mittelachse des Mittelkörpers (52) verläuft.

5. Kraftstoff-/Luftdüse nach Anspruch 3 oder 4, wobei die Mittelachse (42a) von mindestens einem der Luftstrahlen (42) einen spitzen Winkel mit der Mittelachse des Mittelkörpers bildet.

6. Kraftstoff-/Luftdüse nach einem der Ansprüche 3 bis 5, wobei der ringförmige Kanal (70) konfiguriert ist, um sich in fortschreitender stromabwärtiger Richtung in Richtung der Luftstrahlen (61) zu verjüngen.

7. Kraftstoff-/Luftdüse nach einem der vorstehenden Ansprüche, weiter umfassend einen Umstellmechanismus mit einer Vielzahl von Verwirbelungsschaufeln (56), die sich radial über den Primärluftströmungskanal (51) erstrecken, wobei mindestens eine der Verwirbelungsschaufeln (56) einen Kraftstoffkanal (57) definiert, der einen Einlass an einem Ende davon und einen Auslass an einem gegenüberliegenden Ende davon in Fluidverbindung mit dem primären Luftstromkanal (51) aufweist.

8. Kraftstoff-/Luftdüse nach einem der vorstehenden Ansprüche, wobei die Vormischungspilotdüse (40) eine Pilotkraftstoffdüse (60) definiert, wobei die Pilotkraftstoffdüse (60) ein stromaufwärtiges Ende (60a) und ein stromabwärtiges Ende (60b) definiert, wobei das stromaufwärtige Ende (60c) der Pilotkraftstoffdüse (60) in Fluidverbindung mit dem stromabwärtigen Ende (54b) der Kraftstoffzufuhrleitung (54) steht, wobei das stromabwärtige Ende (60b) der Pilotkraftstoffdüse (60) mindestens einen Kraftstoffstrahl (61) definiert, der in Fluidverbindung mit dem stromaufwärtigen Ende (60a) der Pilotkraftstoffdüse (60) konfiguriert ist; und
die Vormischungspilotdüse (40) weiter eine Kraftstoffsammelraumwand (63) definiert, die radial nach außen von der Pilotkraftstoffdüse (60) angeordnet ist und einen Kraftstoffsammelraum (64) zwischen der Pilotkraftstoffdüse (60) und der Kraftstoffsammelraumwand (63) definiert, wobei die Kraftstoffsammelraumwand (63) weiter eine Vielzahl von Kraftstofflöchern (63a) definiert, wobei mindestens eines der Kraftstofflöcher (63c) über den Kraftstoffsammelraum (64) in Fluidverbindung mit mindestens einem der Kraftstoffstrahle (61) verbunden ist, wobei jeder Vormischkanal (41) radial nach außen von der Kraftstoffsammelraumwand (43) und in Fluidverbindung mit mindestens einem der Kraftstofflöcher (63a) angeordnet ist.

9. Flammrohr (16) für einen Gasturbinenmotor (10), wobei das Flammrohr umfasst:

einen Kopfendabschnitt (27); und

mindestens eine Kraftstoff-/Luftdüse (12), die von dem Kopfabschnitt (27) getragen wird, wobei die mindestens eine Kraftstoff-/Luftdüse nach einem der Ansprüche 1 bis 8 ist.

10. Verfahren zum Betreiben einer Kraftstoff-/Luftdüse (12) zur verbesserten Flammenstabilität und NOx in einem Gasturbinentriebwerk (10), wobei die Kraftstoff-/Luftdüse (12) durch eine Umfangswand (50), einen hohlen Mittelkörper (52), der innerhalb der Umfangswand (50) angeordnet ist und eine Mittelachse definiert, definiert ist, wobei sich ein Umstellmechanismus von der Außenseite (52d) des stromaufwärtigen Endes (52b) des Mittelkörpers (52) und radial in Richtung der Umfangswand (50) erstreckt und wobei am stromabwärtigen Ende (52c) des Mittelkörpers (52) eine Vormischungspilotdüse (40) eine Vielzahl von Vormischkanälen (41) mit Austrittsöffnungen (66b) aufweist, wobei das Verfahren die folgenden Schritte umfasst:

Abgeben (81) eines Primärluftstroms (51) stromabwärts hinter dem Umstellmechanismus, um den Primärluftstrom (51) zu verwirbeln;

Abgeben (82) eines primären Kraftstoffstroms durch den Umstellmechanismus, um sich mit dem verwirbelten Primärluftstrom (51) stromabwärts des Umstellmechanismus zu vermischen;

Abgeben (83) eines Pilotkraftstoffstroms durch eine hohle Kraftstoffzufuhrleitung (54) an die Vormischungspilotdüse (40);

Abgeben (84) eines Sekundärluftstroms stromabwärts durch den Mittelkörper (52) zur Vormischungspilotdüse (40);

Mischen (85) des Pilotkraftstoffs mit dem sekundären Luftstrom in einer Vielzahl von axial langgestreckten, hohlen Vormischkanälen (41), dadurch gekennzeichnet, dass

jeder Vormischkanal (41) eine Mittelachse an dem stromabwärtigen Ende (41b) davon definiert, die von der Mittelachse des Mittelkörpers (52) radial nach außen divergiert und die das Kraftstoff-Luft-Gemisch von dem stromabwärtigen Ende (40b) der Vormischungspilotdüse (40) ablässt; und dadurch, dass das Verfahren weiter die folgenden Schritte umfasst:
Ausstoßen des Kraftstoff-Luft-Gemisches aus den Austrittsöffnungen (66b) der Vormischkanäle (41) der Vormischungspilotdüse (40).

11. Verfahren nach Anspruch 10, weiter umfassend den Schritt des Ablenkens eines Teils des Sekundärluftstroms zu einem ringförmigen Kanal (70), der radial außerhalb der Vormischkanäle (41) der Vormischungspilotdüse (40) angeordnet ist.

12. Verfahren nach Anspruch 11, wobei der Druck der Luft, die aus dem ringförmigen Kanal (70) ausgestoßen wird, den Druck der Luft, die in den ringförmigen Kanal (70) eintritt, übersteigt.

13. Verfahren nach Anspruch 11 oder 12, wobei sich der ringförmige Kanal (70) in fortschreitend stromabwärtiger Richtung verjüngt.

14. Verfahren nach einem der Ansprüche 11 bis 13, weiter umfassend den Schritt des Ausstoßens von Luft aus dem ringförmigen Kanal (70) der Vormischungspilotdüse (40) in einer Richtung, die von den Austrittsöffnungen (66b) der Vormischkanäle (41) entfernt ist.

15. Verfahren nach Anspruch 14, wobei die Luft, die aus dem ringförmigen Kanal (70) ausgestoßen wird, von der Mittelachse des Mittelkörpers (52) weggeleitet wird.

Revendications

1. Buse de carburant/air (12) pour un moteur à turbine à gaz (10), la buse de carburant/air comprenant :

une paroi périphérique s'allongeant axialement (50) définissant une enveloppe externe de la buse de carburant/air (12), la paroi périphérique (50) ayant une surface externe (50a) et une surface interne (50b) opposée à la surface externe (50a) et définissant une cavité interne s'allongeant axialement (50c) ;

un corps central creux s'allongeant axialement (52) disposé dans la cavité interne (50c) de la buse de carburant/air (12) et définissant un axe central, le corps central étant défini par une paroi de corps central (52a) définissant une extrémité amont (52b) et une extrémité aval (52c) disposée axialement à l'opposé de l'extrémité amont (52b), la paroi de corps central (52a) étant définie par une surface externe (52a) et une surface interne (52e) opposée à la surface externe (52d), la surface interne (52e) de la paroi de corps central (52a) définissant un passage interne s'allongeant axialement (53) disposé concentriquement autour de l'axe central du corps central (52) ;

une conduite d'alimentation en carburant creuse allongée (54) s'étendant axialement à travers le passage interne (53) du corps central (52), la conduite d'alimentation en carburant (54) ayant une extrémité amont (54a) disposée à l'extrémité amont (52b) du corps central (52) et configurée pour se raccorder à une source de carburant (14), la conduite d'alimentation en carburant (54) ayant une extrémité aval (54b) disposée à l'extrémité aval (52c) du corps central (52) ;

un canal d'écoulement d'air primaire (51) étant défini par un espace annulaire entre la surface externe (52a) du corps central (52) et la surface interne (50b) de la paroi périphérique (50) ;

une buse pilote prémélangée (40) ayant une extrémité amont (40a) raccordée à l'extrémité aval (52c) du corps central (52), la buse pilote prémélangée (40) ayant une extrémité aval (40b) disposée axialement à l'opposé de l'extrémité amont (40a) de la buse pilote prémélangée (40) ; et

la buse pilote prémélangée (40) définissant en outre une pluralité de conduits de prémélange creux axialement allongés (41), chaque conduit de prémélange (41) ayant une extrémité amont (41a) disposée près de l'extrémité aval (52c) du corps central (52) et définissant une ouverture d'entrée qui communique de manière fluidique avec le passage interne (53) du corps central (52), chaque conduit de prémélange (41) ayant au moins un trou de carburant (63a) qui est raccordé en communication fluidique avec l'extrémité aval (54b) de la conduite d'alimentation en carburant (54), chaque conduit de prémélange (41) ayant une extrémité aval (41b) définissant une ouverture de sortie (66b) qui permet au fluide de se décharger du conduit de prémélange creux (41), caractérisé en ce que chaque extrémité aval (41b) de chaque conduit de prémélange (41) définit un axe central (41c) qui diverge radialement vers l'extérieur de l'axe central du corps central (52).

2. Buse de carburant/air selon la revendication 1, dans laquelle chaque axe central (41c) d'au moins un conduit de prémélange (41) est disposé en formant un angle aigu par rapport à l'axe central du corps central (52).

3. Buse de carburant/air selon la revendication 1 ou 2, dans laquelle la buse pilote de prémélange (40) définit en outre un canal annulaire (70) disposé radialement vers l'extérieur des conduits de prémélange (41), le canal annulaire (70) étant configuré pour communiquer de manière fluidique avec le passage interne (53) du corps central (52), le canal annulaire (70) définissant une pluralité de jets d'air (61), au moins l'un des jets d'air (61) étant disposé près de l'une des ouvertures de sortie (66b) d'au moins l'un des conduits de prémélange (41) et ayant un axe central.

4. Buse de carburant/air selon la revendication 3, dans laquelle l'axe central (41d) de l'extrémité amont (41a) d'au moins un conduit de prémélange (41) est configuré et disposé pour s'étendre dans une direction parallèle à l'axe central du corps central (52).

5. Buse de carburant/air selon la revendication 3 ou 4, dans laquelle l'axe central (42a) d'au moins l'un des jets d'air (42) forme un angle aigu avec l'axe central du corps central.

6. Buse de carburant/air selon l'une quelconque des revendications 3 à 5, dans laquelle le canal annulaire (70) est configuré pour s'amincir à mesure qu'il progresse dans la direction aval vers les jets d'air (61).

7. Buse de carburant/air selon l'une quelconque des revendications précédentes, comprenant en outre un swozzle comprenant une pluralité de pales de turbulence (56) s'étendant radialement en travers du canal d'écoulement d'air primaire (51), au moins l'une des pales de turbulence (56) définissant un conduit de carburant (57) ayant une entrée à une de ses extrémités et une sortie à son extrémité opposée en communication fluidique avec le canal d'écoulement d'air primaire (51).

8. Buse de carburant/air selon l'une quelconque des revendications précédentes, dans laquelle la buse pilote prémélangée (40) définit une buse de carburant pilote (60), la buse de carburant pilote (60) définissant une extrémité amont (60a) et une extrémité aval (60b), l'extrémité amont (60c) de la buse de carburant pilote (60) étant raccordée en communication fluidique avec l'extrémité aval (54b) de la conduite d'alimentation en carburant (54), l'extrémité aval (60b) de la buse de carburant pilote (60) définissant au moins un jet de carburant (61) configuré en communication fluidique avec l'extrémité amont (60a) de la buse de carburant pilote (60) ; et
la buse pilote de prémélange (40) définissant en outre une paroi de plénum de carburant (63) disposée radialement vers l'extérieur de la buse de carburant pilote (60) et définissant un plénum de carburant (64) entre la buse de carburant pilote (60) et la paroi de plénum de carburant (63), la paroi de plénum de carburant (63) définissant en outre une pluralité de trous de carburant (63a), au moins l'un des trous de carburant (63c) étant raccordé en communication fluidique avec au moins l'un des jets de carburant (61) via le plénum de carburant (64), chaque conduit de prémélange (41) étant disposé radialement vers l'extérieur de la paroi de plénum de carburant (43) et en communication fluidique avec au moins l'un des trous de carburant (63a).

9. Chambre de combustion (16) pour un moteur à turbine à gaz (10), la chambre de combustion comprenant :

une partie d'extrémité de tête (27) ; et

au moins une buse de carburant/air (12) portée par la partie de tête (27), la au moins une buse de carburant/air étant telle que mentionnée dans l'une quelconque des revendications 1 à 8.

10. Procédé de fonctionnement d'une buse de carburant/air (12) pour améliorer la stabilité des flammes et le NOx dans un moteur à turbine à gaz (10), la buse de carburant/air (12) étant définie par une paroi périphérique (50), un corps central creux (52) disposé dans la paroi périphérique (50) et définissant un axe central, un swozzle s'étendant de l'extérieur (52d) de l'extrémité amont (52b) du corps central (52) et radialement vers la paroi périphérique (50) et, à l'extrémité aval (52c) du corps central (52), une buse pilote de prémélange (40) comprenant une pluralité de conduits de prémélange (41) ayant des ouvertures de sortie (66b), le procédé comprenant les étapes consistant à :

délivrer (81) un écoulement d'air primaire (51) en aval via le swozzle pour soumettre l'écoulement d'air primaire (51) à une turbulence ;

délivrer (82) un écoulement de carburant primaire à travers le swozzle pour se mélanger à l'écoulement d'air primaire turbulent (51) en aval du swozzle ;

délivrer (83) un écoulement de carburant pilote à travers une conduite d'alimentation en carburant creuse (54) à la buse pilote de prémélange (40) ;

délivrer (84) un écoulement d'air secondaire en aval à travers le corps central (52) à la buse pilote de prémélange (40) ;

mélanger (85) le carburant pilote à l'écoulement d'air secondaire dans une pluralité de conduits de prémélange creux axialement allongés (41), caractérisé en ce que chaque conduit de prémélange (41) définit un axe central à l'extrémité aval (41b) de celui-ci qui diverge radialement vers l'extérieur de l'axe central du corps central (52) et qui décharge le mélange de carburant/air de l'extrémité aval (40b) de la buse pilote de prémélange (40) et le procédé comprend en outre l'étape d'expulsion du mélange de carburant/air des ouvertures de sortie (66b) des conduits de prémélange (41) de la buse pilote prémélangée (40).

11. Procédé selon la revendication 10, comprenant en outre l'étape de déviation d'une certaine partie de l'écoulement d'air secondaire vers un canal annulaire (70) qui est disposé radialement vers l'extérieur des conduits de prémélange (41) de la buse pilote prémélangée (40).

12. Procédé selon la revendication 11, dans lequel la pression de l'air expulsé du canal annulaire (70) dépasse la pression de l'air pénétrant dans le canal annulaire (70).

13. Procédé selon la revendication 11 ou 12, dans lequel le canal annulaire (70) s'amincit à mesure qu'il progresse dans la direction aval.

14. Procédé selon l'une quelconque des revendications 11 à 13, comprenant en outre l'étape d'expulsion d'air du canal annulaire (70) de la buse pilote prémélangée (40) dans une direction qui s'écarte des ouvertures de sortie (66b) des conduits de prémélange (41).

15. Procédé selon la revendication 14, dans lequel l'air expulsé du canal annulaire (70) est dirigé en s'écartant de l'axe central du corps central (52).

Drawing