Patent Application
20140367494
1. Field of the Invention
The subject invention relates to fuel injectors for gas turbine engines, and more particularly, to a fuel injector having a nozzle tip assembly with an additively manufactured nozzle body.
2. Description of Related Art
Gas turbine engines must satisfy high demands with respect to reliability, weight, performance, economic efficiency and durability. Among other things, the use of advanced manufacturing methods and material selection play a decisive role in meeting these requirements.
Conventional methods for manufacturing gas turbine components include forging and investment casting. For example, the highly stressed components in the compressor region of a gas turbine are typically manufactured by forging, whereas the rotor and stator blades of the turbine are typically manufactured by investment casting.
Fuel injectors for gas turbine engines often include a complex nozzle tip assembly for delivering atomized fuel to the engine combustor that includes a cast swirler and multiple sub-assemblies. In addition, intricate assembly methods are required to meet specified performance criteria for many nozzle assemblies.
The conventional construction of a fuel injector nozzle includes components that are bonded together by braze. The components typically have milled slots or drilled holes that control the flow of fuel through the nozzle and prepare the fuel for atomization. These components are typically nested within one another and form a narrow diametral gap therebetween which is often filled with a braze alloy.
The braze alloy is usually applied as a braze paste, wire ring, or as a thin sheet shim on the external surfaces or within pockets inside the assembly. The assembly is then heated and the braze alloy melts and flows into the narrow diametral gap and securely bonds the components together upon cooling.
Such conventional methods and systems generally have been considered satisfactory for their intended purpose. However, when using traditional brazing techniques, the braze alloy must flow from a ring or pocket to the braze area. In doing so, it is often prone to flow imprecisely when melted.
In some instances, braze fillets can be formed on or in certain features. If this happens, intricate or narrow passages can become plugged. These fillets and plugs can negatively affect nozzle performance. Moreover, braze may not flow to the desired braze area in the quantity needed to ensure a proper braze joint. This is typical when the braze alloy cannot be located in close proximity to the desired braze joint location.
The difficulty in controlling braze flow when employing traditional brazing techniques is a limiting factor in the design of fuel and air flow passages within a fuel nozzle assembly. That is, the shape and size of the flow passages is limited by the ability to control the flow of braze.
There remains a need in the art for an efficient process to manufacture complex fuel nozzles that reduces the number of component parts and sub-assemblies needed for the fuel nozzle assembly and the use of brazing operations to assemble the nozzle components.
The subject invention is directed to a new and useful fuel injector for a gas turbine engine. The fuel injector has, among other things, a nozzle tip assembly that includes a nozzle body substantially monolithically formed by additive manufacturing.
By way of example, the nozzle body may be formed by direct metal laser sintering (DMLS), or a similar additive manufacturing technique. As a result, the nozzle tip assembly can be manufactured faster and with fewer components and sub-assemblies than the prior art nozzle tip assembly for the same fuel injector.
The monolithically formed nozzle body of the subject invention has an outer fuel circuit formed therein for accommodating transfer of a gaseous fuel and an inner fuel circuit for accommodating transfer of a liquid fuel. In addition, the nozzle body has an outer air circuit formed between the outer fuel circuit and the inner fuel circuit.
Gaseous fuel transfer ports are defined within the nozzle body that extend between the outer fuel circuit and the outer air circuit, and liquid fuel transfer ports are defined within the nozzle body that extend between the inner fuel circuit and the outer air circuit. In addition, a plurality of axial turning vanes are formed within the outer air circuit.
The nozzle tip assembly depends from an end of a feed arm. The feed arm has a first fuel passage that communicates with and delivers gaseous fuel to the outer fuel circuit of the nozzle body and a second fuel passage that communicates with and delivers liquid fuel to the inner fuel circuit of the nozzle body. The nozzle tip assembly further comprises a pressure atomizer that is disposed within an inner air circuit of the nozzle body. The pressure atomizer can serve as a pilot for the nozzle tip assembly.
These and other features of the additively manufactured fuel injector assembly of the subject invention and the manner in which it is employed will become more readily apparent to those having ordinary skill in the art from the following enabling description of the preferred embodiments of the subject invention taken in conjunction with the several drawings described below.
So that those skilled in the art to which the subject invention appertains will readily understand how to make and use the nozzle tip assembly of the subject invention without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein:
Referring now to the drawings, there is illustrated in
The fuel injectors employed on 501-K gas turbine engines can fulfill a variety of application requirements including gas, liquid or dual fuel systems with automatic changeover capability. Water injection may also be employed for emissions control.
As shown in
Inlet fitting 18 communicates with a central fuel passage 22 that extends through the main feed arm 12. The central fuel passage 22 preferably delivers gaseous fuel to the nozzle tip assembly 16. Inlet fitting 20 communicates with a main external feed tube 24 of the feed arm 12. The main external feed tube 24 delivers main liquid fuel to the nozzle tip assembly 16. A third inlet fitting (not shown), communicates with a pilot external feed tube 24a, which delivers pilot liquid fuel to the nozzle tip assembly 16. While not illustrated in
With continuing reference to
More particularly, the prior art nozzle tip assembly 16 includes a generally cylindrical outer shroud 40 and an outer sleeve 42. An outer gas passage 44 is defined between the outer shroud 40 and the outer sleeve 42. The outer gas passage 44 communicates with the central fuel passage 22 of feed arm 12. An end ring 43 supports the rear end portion of the outer sleeve 42 within the shroud 40.
An air swirler 45 is positioned coaxially within the outer sleeve 42. An air mixing channel 46 is formed between the outer surface of the air swirler 45 and the inner surface of the outer sleeve 42. The air swirler 45 includes a plurality of circumferentially spaced apart radial swirl vanes 48 disposed within the air mixing channel 46 for imparting swirl to air flowing therethrough.
A plurality of circumferentially disposed gas exit ports 50 extend between the outer gas passage 44 and the air mixing channel 46, upstream from the radial swirl vanes 48. The air mixing channel 46 has a converging outer wall formed by an air lip 52 positioned downstream from the radial swirl vanes 48.
The air swirler 45 has a central bore that supports a separate inner air sleeve 54. A liquid fuel transfer annulus 55 is defined between the exterior surface of the inner air sleeve 54 and the interior surface of the air swirler 45. The fuel transfer annulus 55 receives fuel from a fuel inlet (not shown in
A plurality of radially outwardly extending fuel exit ports 58 extend between the fuel transfer annulus 55 and the air mixing channel 46. The forward end of the inner air sleeve 54 forms a fuel conic 60 downstream from the exit ports 58 that defines a prefilming surface for liquid fuel exiting the ports 58.
The inner air sleeve 54 defines a central bore that supports and retains a pressure atomizer 62, which can serve as a pilot for the nozzle tip assembly 16 under certain operating conditions. The pressure atomizer 62 has an axial bore 64 extending therethrough from a proximal inlet end 64a to a distal exit end 64b. The proximal inlet end 64a of axial bore 64 is preferably threaded to accept a plug that retains the pressure atomizer distributor and an associated seal (not shown). The distal exit end 64b is tapered to effect the flow of pressurize fuel flowing therethrough. The pressure atomizer 62 also includes a fuel inlet passage 66 that communicates with the pilot external feed tube 24a. The inlet passage 66 delivers liquid fuel into the axial bore 64 of the pressure atomizer 62.
In sum, the prior art nozzle tip assembly 10 includes the following separately machined component parts: an outer shroud 40, outer sleeve 42, end ring 43, air swirler 45, air lip 52, inner air sleeve 54 and a pressure atomizer 62. Each of these parts must are joined together using numerous braze and weld joints, which tend to limit the efficient manufacturability of the assembly 10.
In contrast to the prior art fuel injector 10, the novel fuel injector of the subject invention, which is shown in
Those skilled in the art will readily appreciate that the term additive manufacturing, as used herein, encompasses techniques such as laser additive deposition, laser metal deposition, direct laser deposition, direct metal deposition, laser cladding and the like.
In accordance with an exemplary embodiment, the present invention relates to the use of a rapid construction method for producing the nozzle body 125 of nozzle assembly 116. Specifically, the invention utilizes a rapid manufacturing technology known as direct metal laser sintering (DMLS) to manufacture a monolithic nozzle body that eliminates joints, brazing and other aspects of the prior art nozzle construction.
DMLS is an additive layer process that produces a metal component directly from a CAD model using a laser and a fine metal powder (e.g., cobalt and/or chrome alloy powders and Nickel-based alloy powders are especially suited for the turbine nozzle application disclosed herein, but the invention is not so limited).
The CAD model is sliced into thin layers (on the order of 0.02 mm) and the layers are then reconstructed layer by layer, with the laser fusing programmed areas of each powder layer in succession to the underlying layer. The layer thickness is generally chosen based on a consideration of accuracy versus speed of manufacture. Initially, a steel plate is typically fixed inside the machine to serve as both a support and a heat sink.
A dispenser delivers the powder to the support plate and a coater arm or blade spreads the powder on the plate. The machine software controls the laser beam focus and movement so that wherever the laser beam strikes the powder, the powder melts into a solid. The process continues layer by layer until the buildup is completed.
Referring now to
Inlet fitting 118 communicates with a central fuel passage 122 that extends through the main feed arm 112 to deliver gaseous fuel to the nozzle tip assembly 116. Inlet fitting 120 communicates with a main external feed tube 124 that delivers main liquid fuel to the nozzle tip assembly 116. A third inlet fitting (not shown) communicates with a pilot external feed tube 124a that delivers pilot liquid fuel to the nozzle tip assembly 116.
The nozzle tip assembly 116 includes a monolithically formed nozzle body 125 which defines an outer shroud portion 140 and an outer sleeve portion 142. An outer gas passage 144 is defined between the outer shroud portion 140 and the outer sleeve potion 142. The outer gas passage 144 communicates with the central fuel passage 122 of feed arm 112. The end sections of the outer shroud portion 140 and the outer sleeve portion 142 are bridged by integral supporting structure 143.
An air swirler portion 145 is formed coaxially within the outer sleeve portion 142 of nozzle body 125. An air mixing channel 146 is formed between the outer surface of the air swirler portion 145 and the inner surface of the outer sleeve portion 142 of nozzle body 125. The air swirler portion 145 includes a plurality of circumferentially spaced apart radial swirl vanes 148 that extend between the air swirler portion 145 and the outer sleeve portion 142 of nozzle body 125. The swirl vanes 148 impart swirl to air flowing through the air mixing channel 146.
A plurality of circumferentially disposed gas exit ports 150 extend between the outer gas passage 144 and the air mixing channel 146, upstream from the radial swirl vanes 148. The air mixing channel 146 has a converging outer wall formed by an integral air lip portion 152 projecting from the shroud portion 140 downstream from the radial swirl vanes 148.
The air swirler portion 145 of nozzle body 125 is monolithically formed with an inner air sleeve portion 154. A liquid fuel transfer annulus 155 is defined between the inner air sleeve portion 154 and the air swirler portion 145. The fuel transfer annulus 155 receives fuel from a fuel inlet 156 that communicates with the lower end of fuel tube 124 (see
A plurality of radially outwardly extending fuel exit ports 158 extend between the fuel transfer annulus 155 and the air mixing channel 146. The forward end of the air sleeve 154 forms a fuel conic 160 downstream from the exit ports 158 that defines a prefilming surface for liquid fuel exiting the ports 158.
As best seen in
The pressure atomizer 162 also includes a pilot liquid fuel inlet 166 that communicates with the pilot liquid fuel feed tube 124a. The fuel inlet passage 166 delivers pilot liquid fuel into the axial bore of the pressure atomizer 162.
While the subject invention has been shown and described with reference to a preferred embodiment, those skilled in the art will readily appreciate that various changes and/or modifications may be made thereto without departing from the spirit and scope of the subject invention as defined by the appended claims.
