Compound angle accelerator

Abstract

Accelerators, methods of manufacturing accelerators, and gas turbine engines are provided. For example, an accelerator for a gas turbine engine defines a radial direction and an axial direction, and includes an annular outer wall, an annular inner wall, an annular passage defined between the outer wall and the inner wall, and a plurality of vanes disposed within the passage. The passage has an inlet for entry of a cooling fluid and an outlet for exit of the cooling fluid. Each vane extends from the outer wall to the inner wall proximate the outlet, wherein the outlet is angled such that an exit angle of the cooling fluid is non-zero with respect to both the radial direction and the axial direction. The accelerator can be manufactured using an additive manufacturing method. The accelerator outlet can be disposed directly upstream of a first turbine rotor blade stage of the gas turbine engine to direct the cooling fluid thereto.

Description

Technical Field

[0001] The present subject matter relates generally to gas turbine engines and, more particularly, to gas turbine engine accelerators. Background Art

[0002] Gas turbine engines typically operate at high temperatures, with some parts of a given engine operating at higher temperatures than other parts of the engine. Features such as accelerators can be used to direct cooling fluid (e.g., ambient air or engine bleed air) to engine components that require cooling. For example, an accelerator can be located upstream of a rotor blade stage within the engine, and the accelerator can direct the flow of cooling fluid to the rotor blades. However, typical accelerators are formed using a casting process, which can result in fluid leakage, etc., thereby reducing the performance of the accelerator. In addition, typical accelerators can provide cooling fluid such that the cooling fluid is largely stagnant compared to the speed of the rotor blades, which can affect the clearance and connection between the accelerator and the rotor blade stage and result in parasitic power losses in the rotor cavity and pressure losses in the cooling supply circuit, thereby affecting the performance of the system. Therefore, an improved accelerator that addresses one or more of the above challenges would be useful. Summary of the Invention

[0003] Aspects and advantages of the invention will be set forth in part in the description which follows, or may be obvious from the description, or may be learned through practice of the invention.

[0004] In one exemplary embodiment of the present subject matter, an accelerator for a gas turbine engine is provided. The accelerator defines a radial direction and an axial direction and includes an annular outer wall, an annular inner wall, an annular channel defined between the outer wall and the inner wall, and a plurality of vanes disposed within the channel. The channel has an inlet for admitting a cooling fluid into the channel and an outlet for exiting the channel. Each of the plurality of vanes extends from the outer wall to the inner wall adjacent to the outlet. The outlet is angled such that an exit angle of the cooling fluid is non-zero with respect to the radial direction and non-zero with respect to the axial direction.

[0005] In another exemplary embodiment of the present subject matter, a method for manufacturing an accelerator for a gas turbine engine is provided. The method includes depositing a layer of additive material on a bed of an additive manufacturing machine and selectively directing energy from an energy source onto the layer of additive material to melt a portion of the additive material and form an accelerator. The accelerator includes an annular outer wall, an annular inner wall, an annular channel defined between the outer wall and the inner wall, and a vane disposed within the channel. The channel includes an inlet for allowing a cooling fluid to enter the channel and an outlet for allowing the cooling fluid to flow out of the channel. The vane extends from the outer wall to the inner wall adjacent to the outlet. The outlet is angled so that the outlet angle of the cooling fluid has a non-zero radial portion and a non-zero axial portion. The outer wall, the inner wall, and the vane are integrally formed as a single, unitary component.

[0006] In another exemplary embodiment of the present subject matter, a gas turbine engine is provided. The gas turbine engine includes a combustor, a first turbine stator vane stage disposed directly downstream of the combustor and including an annular array of stator vane airfoils, a first turbine rotor blade stage disposed directly downstream of the first turbine stator vane stage and including an annular array of rotor blade airfoils coupled to a rotatable shaft, and an accelerator circumferentially surrounding the shaft. The accelerator includes an annular passage for receiving a cooling fluid. The passage includes an outlet defining a compound outlet angle for the cooling fluid. The outlet of the accelerator is disposed directly upstream of the first turbine rotor blade stage to direct the cooling fluid to the first turbine rotor blade stage.

[0007] These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims.The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] This specification sets forth a complete and enabling disclosure of the invention, including the best mode thereof, to one of ordinary skill in the art with reference to the accompanying drawings, in which:

[0009] Figure 1 Schematic cross-sectional views of exemplary gas turbine engines according to various embodiments of the present subject matter are provided.

[0010] Figure 2 According to exemplary embodiments of the present subject matter, Figure 1 Schematic cross-sectional view of a portion of the combustion section and high pressure (HP) turbine section of a gas turbine engine.

[0011] Figure 3 A rear perspective view of an accelerator according to an exemplary embodiment of the present subject matter is provided.

[0012] Figure 4 Provided Figure 3 A cross-sectional view of an exemplary accelerator.

[0013] Figure 5 Provided are diagrams illustrating the manufacture of an exemplary embodiment according to the present subject matter. Figure 3 Flowchart of the accelerator method. DETAILED DESCRIPTION

[0014] Reference will now be made in detail to the present embodiments of the present 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. The same or similar reference numerals in the drawings and the description have been used to refer to the same or similar parts of the invention.

[0015] As used herein, the terms "first," "second," and "third" may be used interchangeably to distinguish one component from another, and not to indicate the location or importance of the respective components. The terms "front" and "rear" refer to relative positions within a gas turbine engine or vehicle, and refer to the normal operating attitude of the gas turbine engine or vehicle. For example, with respect to a gas turbine engine, front refers to a position near the engine inlet, and rear refers to a position near the engine nozzle or exhaust. The terms "upstream" and "downstream" refer to relative directions relative to the flow of a fluid in a fluid path. For example, "upstream" refers to the direction from which the fluid flows, and "downstream" refers to the direction to which the fluid flows. Unless otherwise specified herein, the terms "coupled," "fixed," "attached to," and the like refer to both direct coupling, fixing, or attachment, and indirect coupling, fixing, or attachment through one or more intermediate components or features. The singular forms "a," "an," and "the" include the plural unless the context clearly dictates otherwise.

[0016] Additionally, as used herein, the terms "axial" or "axially" refer to the dimension along the longitudinal axis of the engine. The term "front" used in conjunction with "axial" or "axially" refers to the direction toward the engine inlet, or a component that is closer to the engine inlet than another component. The terms "rear" or "rearward" used in conjunction with "axial" or "axially" refer to the direction toward the engine exhaust, or a component that is closer to the engine exhaust than another component. The terms "radial" or "radially" refer to the dimension extending between the central longitudinal axis (or centerline) of the engine and the outer circumference of the engine. Radially inward is toward the longitudinal axis and radially outward is away from the longitudinal axis.

[0017] Approximate language, as used herein throughout the specification and claims, is applied to modify any quantitative representation that can be permitted to vary without resulting in a change in the basic function to which it is related. Thus, a value modified by one or more terms, such as "about," "approximately," and "substantially," is not limited to the precise value specified. At least in some cases, approximate language can correspond to the precision of an instrument used to measure a value, or the precision of a method or machine used to construct or manufacture a component and / or system. Approximate language can refer to a single value, a range of values, and / or a margin within + / - 1%, 2%, 4%, 10%, 15%, or 20% of the endpoints of a defined range of values.

[0018] Here and throughout the specification and claims, range limitations are combined and interchanged, and unless context or language indicates otherwise, such ranges are identified and include all sub-ranges contained therein. For example, all ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other.

[0019] Generally, the present subject matter relates to a gas turbine engine accelerator having a compound outlet angle. More specifically, the present subject matter relates to an accelerator defining a radial direction and an axial direction and including an annular outer wall, an annular inner wall, and an annular passage defined therebetween, the annular passage having an outlet for exiting a cooling fluid from the passage. The outlet is angled such that the outlet angle of the cooling fluid is non-zero relative to the radial direction and non-zero relative to the axial direction. Furthermore, at least one of the inner wall and the outer wall may have a first length defined at a first non-zero angle relative to the axial direction and a second length defined at a second non-zero angle relative to the axial direction. In an exemplary embodiment, the outlet is positioned directly upstream of a first turbine rotor blade stage to direct the cooling fluid to the first turbine rotor blade stage.

[0020] Referring now to the drawings, in which like numerals represent like elements throughout, Figure 1 is a schematic cross-sectional view of a gas turbine engine according to an exemplary embodiment of the present disclosure. More specifically, Figure 1 In the embodiment of the present invention, the gas turbine engine is a high bypass turbofan jet engine 10, referred to herein as "turbofan engine 10". Figure 1 As shown, the turbofan engine 10 defines an axial direction A (extending parallel to a longitudinal centerline 12 for reference), a circumferential direction C (extending about the longitudinal centerline 12 and the axial direction A), and a radial direction R. Generally, the turbofan 10 includes a fan section 14 and a core turbine engine 16 disposed downstream of the fan section 14 .

[0021] The depicted exemplary core turbine engine 16 generally includes a substantially tubular casing 18 defining an annular inlet 20. The casing 18 surrounds, in series flow relationship, a compressor section including a supercharger or low-pressure (LP) compressor 22 and a high-pressure (HP) compressor 24; a combustion section 26; a turbine section including a high-pressure (HP) turbine 28 and a low-pressure (LP) turbine 30; and an exhaust nozzle section 32. A high-pressure (HP) shaft or spool 34 drivingly connects the HP turbine 28 to the HP compressor 24. A low-pressure (LP) shaft or spool 36 drivingly connects the LP turbine 30 to the LP compressor 22.

[0022] For the depicted embodiment, fan section 14 includes a fan 38 having a plurality of fan blades 40 coupled in a spaced-apart manner to a disk or hub 42. As depicted, fan blades 40 generally extend outward from disk 42 in a radial direction R. Fan blades 40 and disk 42 are rotatable together about longitudinal centerline 12 via LP shaft 36. In some embodiments, a power gearbox having a plurality of gears may be included for reducing the rotational speed of LP shaft 36 to a more efficient fan rotational speed.

[0023] Still refer to Figure 1 In an exemplary embodiment, the disk 42 is covered by a rotatable forward nacelle 48 having an aerodynamic profile to facilitate airflow through the plurality of fan blades 40. Additionally, the exemplary fan section 14 includes an annular fan case or outer nacelle 50 that circumferentially surrounds the fan 38 and / or at least a portion of the core turbine engine 16. It should be understood that the fan case (nacelle) 50 can be configured to be supported relative to the core turbine engine 16 by a plurality of circumferentially spaced outlet guide vanes 52. Furthermore, a downstream section 54 of the fan case 50 can extend over an outer portion of the core turbine engine 16 to define a bypass airflow passage 56 therebetween.

[0024] During operation of the turbofan engine 10, a volume of air 58 enters the turbofan 10 through the fan case 50 and / or associated inlet 60 of the fan section 14. As the volume of air 58 passes through the fan blades 40, a first portion of the air 58, as indicated by arrow 62, is directed or routed into the bypass airflow passage 56, and a second portion of the air 58, as indicated by arrow 64, is directed or routed into the LP compressor 22. The ratio between the first portion 62 of air and the second portion 64 of air is generally referred to as the bypass ratio. The pressure of the second portion 64 of air then increases as it is routed through the compressor section and into the combustion section 26, where it is mixed with fuel and combusted to provide combustion gases 66. More specifically, the compressor section includes an LP compressor 22 and an HP compressor 24, each of which may include a plurality of compressor stages 80, each stage 80 including an annular array or circumferential row of stationary compressor blades 82 (also referred to as compressor stator blades 82) and an annular array or circumferential row of rotating compressor blades 84 (also referred to as compressor rotor blades 84) positioned immediately downstream of the compressor blades 82. The plurality of compressor blades 84 in the LP compressor 22 is coupled to the LP shaft or spool 36, and the plurality of compressor blades in the HP compressor 24 is coupled to the HP shaft or spool 34. The plurality of compressor blades 82 in the LP compressor 22 is coupled to a compressor casing, and the plurality of compressor blades 82 in the HP compressor 24 is coupled to the compressor casing; at least a portion of the HP compressor blades 82 is coupled to a compressor casing 90. In some embodiments, the compressor casing 90 may extend through both the LP compressor 22 and the HP compressor 24 and support all of the compressor blades 82. In other embodiments, the compressor casing 90 supports only a portion of the compressor blades 82 and may support only a portion of the compressor blades 82 in the HP compressor 24. As previously described, as the second portion of air 64 passes through sequential stages of compressor buckets 82 and blades 84 , the volume of air 64 is pressurized, ie, the pressure of the air 64 is increased, prior to combusting with the fuel in the combustion section 26 to form combustion gases 66 .

[0025] The combustion gases 66 are routed through the HP turbine 28, wherein a portion of the thermal and / or kinetic energy is extracted from the combustion gases 66 via sequential stages of HP turbine stator blades 68 coupled to the casing 18 and HP turbine rotor blades 70 coupled to the HP shaft or spool 34, thereby causing the HP shaft or spool 34 to rotate, thereby supporting operation of the HP compressor 24. The combustion gases 66 are then routed through the LP turbine 30, wherein a second portion of the thermal and kinetic energy is extracted from the combustion gases 66 via sequential stages of LP turbine stator blades 72 coupled to the casing 18 and LP turbine rotor blades 74 coupled to the LP shaft or spool 36, thereby causing the LP shaft or spool 36 to rotate, thereby supporting operation of the LP compressor 22 and / or rotation of the fan 38.

[0026] The combustion gases 66 are then routed through the jet exhaust nozzle section 32 of the core turbine engine 16 to provide propulsive thrust. Simultaneously, the pressure of the first portion of air 62 is significantly increased as the first portion of air 62 is routed through the bypass airflow passage 56 before being discharged from the fan nozzle exhaust section 76 of the turbofan 10, also providing propulsive thrust. The HP turbine 28, the LP turbine 30, and the jet exhaust nozzle section 32 at least partially define a hot gas path 78 for routing the combustion gases 66 through the core engine 16.

[0027] although Figure 1 The gas turbine engine is depicted as a turboshaft configuration, but it should be understood that the teachings of the present disclosure can be applied to other types of turbine engines, more generally turbomachines, and other shaft systems. For example, the turbine engine can be another suitable type of gas turbine engine, such as a turboprop engine, a turbojet engine, a turbofan engine, an aeroderivative engine, etc. The present disclosure can also be applied to other types of turbomachinery, such as a steam turbine engine.

[0028] Figure 2 A schematic cross-sectional view of a portion of the combustion section 26 and the HP turbine 28 is provided. More specifically, Figure 2An accelerator 100 is shown disposed in a gas turbine engine, such as the core turbine engine 16 of the turbofan 10. The gas turbine engine 16 includes a combustor 26, a first turbine stator blade stage 28A of an HP turbine 28 disposed directly downstream of the combustor 26, and a first turbine rotor blade stage 28B of the HP turbine 28 disposed directly downstream of the first turbine stator blade stage 28A. The first turbine stator blade stage 28A includes an annular array of stator blade airfoils 68, and the first turbine rotor blade stage 28B includes an annular array of rotor blade airfoils 70. The rotor blade airfoils 70 are coupled to a rotatable shaft, namely an HP shaft or spool 34. The accelerator 100 circumferentially surrounds the shaft 34. The accelerator 100 includes an annular passage 102 for receiving a cooling fluid F. The passage includes an inlet 104 for receiving the cooling fluid F, and an outlet 106 defining a compound outlet angle for the cooling fluid F. Outlet 106 is disposed directly upstream of first turbine rotor blade stage 28B to direct cooling fluid F to first turbine rotor blade stage 28B.

[0029] Figure 3 and 4 The accelerator 100 is shown in more detail. Figure 3 and Figure 4 As shown, the accelerator 100 defines a radial direction R and an axial direction A. The accelerator 100 includes an annular outer wall 108 and an annular inner wall 110, which define an annular passage 102 therebetween. As described above, the passage 102 has an inlet 104 for allowing the cooling fluid F to enter the passage 102 and an outlet 106 for allowing the cooling fluid F to exit the passage 102. The accelerator 100 has an overall annular shape and thus surrounds the rotor 34 so that the rotor 34 passes therethrough. The axial centerline of the accelerator 100 can be substantially aligned with the longitudinal centerline of the rotor 34 (which can be located along the longitudinal centerline 12 of the engine 10).

[0030] Furthermore, a plurality of vanes 112 are disposed within passage 102. Each vane 112 extends from outer wall 108 to inner wall 110, and each vane 112 is disposed adjacent outlet 106. Furthermore, each vane 112 has a shape configured to induce tangential flow of cooling fluid F as it exits outlet 106. That is, vanes 112 are shaped to divert the flow of cooling fluid F tangentially toward rotor blades 70 of first turbine rotor blade stage 28B. As described in greater detail herein, outer wall 108, inner wall 110, and plurality of vanes 112 are integrally formed as a single, unitary component, for example, using an additive manufacturing process.

[0031] As previously mentioned, the outlet 106 defines a compound outlet angle for the cooling fluid F. For example, Figure 4As shown, the outlet 106 is angled such that the outlet angle α of the cooling fluid F is non-zero with respect to the radial direction R and non-zero with respect to the axial direction A. That is, the outlet angle α of the cooling fluid F is angled with respect to both the radial direction R and the axial direction A such that the outlet angle α is non-zero with respect to the radial direction R (α 径向 ) is non-zero when measured and is in the axial direction A(α 轴向 ) is non-zero when measured. The cooling fluid passages of the exemplary embodiments described herein with compound exit angles α may have a greater portion of their length extending in the radial direction R than typical designs, which typically extend substantially in the axial direction such that the exit flow is substantially axial.

[0032] More specifically, if Figure 4 As shown in the exemplary embodiment of FIG, the inner wall 110 is angled relative to the axial direction A and the radial direction R. That is, the inner wall 110 is defined at a non-zero angle relative to both the axial direction A and the radial direction R. Figure 4 As shown, the channel 102 includes a middle portion 114 located between the inlet 104 and the outlet 106. In some embodiments, the middle portion 114 can be approximately midway between the inlet 104 and the outlet 106 along the length of the channel 102 measured from the inlet 104 to the outlet 106. In other embodiments, the middle portion 114 can be closer to the inlet 104 or closer to the outlet 106 rather than approximately midway between the inlet 104 and the outlet 106. In the depicted embodiment, the inner wall 110 is defined at a first non-zero angle β relative to the axial direction A over a first length L1, and the inner wall 110 is defined at a second non-zero angle γ relative to the axial direction over a second length L2. The first length L1 extends from the inlet 104 to the middle portion 114, and the second length L2 extends from the middle portion 114 to the outlet 106. As shown in FIG. Figure 4 As shown, the first non-zero angle β is greater than the second non-zero angle γ, i.e., β>γ. However, in other embodiments, the second non-zero angle γ can be greater than the first non-zero angle β, such that β<γ. In addition, the first length L1 and the second length L2 can extend over other portions of the inner wall 110, although one of the first length L1 and the second length L2 is defined adjacent to the outlet 106 to provide the exiting cooling fluid F at an angle relative to the radial direction R and the axial direction A.

[0033] In the illustrated embodiment, unlike the inner wall 110, the outer wall 108 is not defined at two different non-zero angles relative to the axial direction A. It should be understood that in other exemplary embodiments, the outer wall 108 may also be defined at two or more non-zero angles relative to the axial direction A. Furthermore, the inner wall 110 may be defined at more than two non-zero angles relative to the axial direction A. In some embodiments, the outer wall 108 may be defined at multiple non-zero angles relative to the axial direction A, while the inner wall 110 is not defined at multiple non-zero angles relative to the axial direction A (e.g., it may be defined at only one non-zero angle relative to the axial direction A). In yet other embodiments, one of the outer wall 108 and the inner wall 110 (or a portion thereof) may be substantially parallel to the axial direction A, while the other of the outer wall 108 and the inner wall 110 is defined at multiple non-zero angles relative to the axial direction A. It should be understood that the multiple non-zero angles of the outer wall 108 and / or the inner wall 110 help define a composite exit angle for the cooling fluid F.

[0034] like Figure 4 As further depicted in FIG, the passageway outlet 106 is angled radially inward such that the passageway inlet 104 is disposed radially outward of the outlet 106. More specifically, the outlet 106 is angled such that the outlet 106 directs the flow of the cooling fluid F radially inward relative to the first turbine rotor blade stage 28B. Thus, the cooling fluid F is directed toward the rotor 34 (i.e., the HP shaft or spool 34 in the exemplary embodiment shown) to help cool the rotor 34. By angling the flow of the cooling fluid F upon exiting the passageway 102 and using the vanes 112 to direct the cooling fluid flow tangentially to the rotor 34, the cooling fluid flow can be accelerated to a tangential velocity of the rotor 34 and rotor blades 70. In the exemplary embodiment, the passageway 102 of the accelerator 100 can be defined such that upon exiting the passageway 102, the flow of the cooling fluid F travels in substantially the same direction and at substantially the same velocity as the rotor 34 and rotor blades 70, which can help improve cooling efficiency by reducing relative stagnation between the cooling fluid flow and the rotor 34 and rotor blades 70.

[0035] and Figure 4 Keeping it consistent, the channel 102 defines a width W from the inner wall 110 to the outer wall 108, and the width W varies along the channel 102 from the inlet 104 to the outlet 106. In the depicted embodiment, the width W of the channel 102 decreases both from the inlet 104 to the middle portion 114 and from the middle portion 114 to the outlet 106, such that the width W at the inlet 104 is greater than the width W at the outlet 106, i.e., W 入口 >W 出口 Narrowing the passage 102 from the inlet 104 to the outlet 106 helps accelerate the flow of the cooling fluid F to a tangential velocity of the rotor 34 and the rotor blades 70 .

[0036] As in Figure 3 and Figure 4 As further described in , an annular flange 116 extends radially outward from outer wall 108. In the exemplary embodiment, flange 116 is integrally formed with outer wall 108, e.g., such that outer wall 108, inner wall 110, plurality of blades 112, and flange 116 are integrally formed as a single, unitary component. Furthermore, flange 116 defines a plurality of holes 118 therein. Holes 118 are defined around the circumference of flange 116 such that holes 118 are spaced apart from one another around the circumference of flange 116. Figure 2 As shown, in the exemplary embodiment, aperture 118 is configured to receive an attachment mechanism, such as a bolt or other suitable fastener, for example, to secure accelerator 100 in position within core turbine engine 16 .

[0037] In the exemplary embodiment depicted, the flange 116 is substantially parallel to the radial direction R. Furthermore, the flange 116 is disposed radially outward from the outlet 106 such that the flange 116 and the outlet 106 define a rearward end 120 of the accelerator 100. More specifically, the flange 116 and the outlet 106 may be generally aligned with one another along the radial direction R and may define a rearward end portion of the accelerator 100.

[0038] Additionally, a connecting portion 122, or simply connector 122, may be defined between the inlet end 124 of the outer wall 108 and the flange 116. Figure 4 In the exemplary embodiment shown, the connector 122 is substantially parallel to the axial direction A. A semicircular fillet 125 is defined between the inlet end 124 of the outer wall 108 and the connector 122. Furthermore, the connector 122 defines an inner surface 126 against which a seal, such as an abradable seal 128, may be positioned, for example, to provide a fluid seal between the accelerator 100 and the first turbine rotor blade stage 28B.

[0039] Also in the illustrated embodiment, an inner wall flange 130 extends axially forward from the inner wall 110. The inner wall flange 130 extends from the inner wall 110 adjacent the mid-portion 114 such that a fillet 132 is defined between the inner wall 110 at the mid-portion 114 and the inner wall flange 130. Furthermore, the inner wall flange 130 defines an inner surface 134 against which a seal, such as the wear seal 128, may be positioned, for example, to provide a fluid seal between the accelerator 100 and the first turbine rotor blade stage 28B.

[0040] The accelerator 100 may also define other flanges. Figure 4As most clearly shown in FIG, a flange 136 can be defined at an inlet end 138 of the inner wall 110. In the illustrated embodiment, the flange 136 extends generally in a radial direction R. Similarly, a flange 140 can be defined at an outlet end 142 of the outer wall 108. In the illustrated embodiment, the flange 140 extends generally in the radial direction R, but is slightly angled relative to the radial direction R. The flanges 136, 140 can help align the accelerator 100 with other engine components, provide areas for coupling the accelerator 100 to other engine components, and so on. Therefore, orientations of the flanges 136, 140 other than those shown may also be suitable.

[0041] In general, the exemplary embodiments of the accelerator 100 described herein can be manufactured or formed using any suitable process. However, according to several aspects of the present subject matter, the accelerator 100 can be formed using an additive manufacturing process, such as a 3D printing process. The use of such a process can allow the outer wall 108, inner wall 110, and vanes 112 of the accelerator 100 to be integrally formed, either as a single, unitary component, or as any suitable number of subcomponents. In particular, the manufacturing process can allow the outer wall 108, inner wall 110, and vanes 112 to be integrally formed and include various features not possible using existing manufacturing methods. For example, the additive manufacturing methods described herein enable the manufacture of cooling channels and accelerators of any suitable size and shape, with one or more configurations of channel walls, channel widths, and channel exit angles, as well as other features not possible using existing manufacturing methods, such as smaller features, including smaller fillets and smaller openings or holes, and smaller fillet radii. Some of these novel features are described herein.

[0042] As used herein, the terms "additive manufacturing" or "additive manufacturing techniques or processes" generally refer to manufacturing processes in which successive layers of material are provided upon one another to "build up" a three-dimensional component layer by layer. The successive layers are typically fused together to form a unitary component that may have multiple integral subcomponents. Although additive manufacturing techniques are described herein as being capable of manufacturing complex objects by building up the object point by point, layer by layer, and typically in a vertical direction, other manufacturing methods are possible and within the scope of the present subject matter. For example, although the discussion herein relates to adding material to form successive layers, one skilled in the art will understand that the methods and structures disclosed herein may be practiced with any additive manufacturing technique or manufacturing process. For example, embodiments of the present invention may use a layer additive process, a layer subtractive process, or a hybrid process.

[0043] Suitable additive manufacturing techniques in accordance with the present disclosure include, for example, fused deposition modeling (FDM), selective laser sintering (SLS), 3D printing (e.g., by inkjet and laser jet), stereolithography (SLA), direct selective laser sintering (DSLS), electron beam sintering (EBS), electron beam melting (EBM), laser engineered net shaping (LENS), laser net shape manufacturing (LNSM), direct metal deposition (DMD), digital light processing (DLP), direct selective laser melting (DSLM), selective laser melting (SLM), direct metal laser melting (DMLM), and other known processes.

[0044] In addition to using a direct metal laser sintering (DMLS) or direct metal laser melting (DMLM) process, in which an energy source is used to selectively sinter or melt portions of a powder layer, it should be appreciated that, in accordance with alternative embodiments, the additive manufacturing process can be a "binder jetting" process. In this regard, binder jetting involves the continuous deposition of additive powder layers in a similar manner as described above. However, rather than using an energy source to generate an energy beam to selectively melt or fuse the additive powder, a liquid binder is selectively deposited onto each layer of powder. The liquid binder can be, for example, a light-cured polymer or another liquid binder. Other suitable additive manufacturing methods and variations are intended to fall within the scope of the present subject matter.

[0045] The additive manufacturing processes described herein can be used to form components using any suitable material. For example, the material can be a plastic, a metal, a concrete, a ceramic, a polymer, an epoxy, a photosensitive polymer resin, or any other suitable material that can be in a solid, liquid, powder, sheet, wire, or any other suitable form. More particularly, in accordance with exemplary embodiments of the present subject matter, the additive manufactured components described herein can be formed partially, entirely, or in some combination of materials including, but not limited to, pure metals, nickel alloys, chromium alloys, titanium, titanium alloys, magnesium, magnesium alloys, aluminum, aluminum alloys, iron, iron alloys, stainless steel, and nickel or cobalt-based superalloys (e.g., those available from Special Metals Corporation under the name HAYNES®). These materials are examples of materials suitable for use in the additive manufacturing processes described herein, and can be generally referred to as "additive materials."

[0046] ​In addition, those skilled in the art will understand that a variety of materials and methods for combining these materials may be used and are considered to be within the scope of the present disclosure. As used herein, reference to "melting" may refer to any suitable process for producing a bonding layer of any of the above-mentioned materials. For example, if the object is made of a polymer, then melting may refer to producing a thermosetting bond between the polymer materials. If the object is an epoxy resin, the bond may be formed by a cross-linking process. If the material is a ceramic, the bond may be formed by a sintering process. If the material is a powdered metal, the bond may be formed by a melting or sintering process. Those skilled in the art will understand that other methods of melting materials to produce parts by additive manufacturing are possible, and the subject matter disclosed herein may be practiced using these methods.

[0047] In addition, the additive manufacturing process disclosed herein allows a single component to be formed from multiple materials. Therefore, the components described herein can be formed from any suitable mixture of the above-mentioned materials. For example, a component can include multiple layers, segments, or parts formed using different materials, processes, and / or on different additive manufacturing machines. In this way, components with different materials and material properties can be constructed to meet the needs of any specific application. In addition, although the additive manufacturing process for forming the components described herein is described in detail, it should be understood that in alternative embodiments, all or a portion of these components may be formed via casting, machining, and / or any other suitable manufacturing process. In fact, any combination of suitable materials and manufacturing methods can be used to form these components.

[0048] An exemplary additive manufacturing process will now be described. An additive manufacturing process uses three-dimensional (3D) information of a component (e.g., a 3D computer model) to manufacture the component. Thus, a 3D design model of the component can be defined prior to manufacturing. In this regard, a model or prototype of the component can be scanned to determine the 3D information of the component. As another example, a model of the component can be constructed using a suitable computer-aided design (CAD) program to define the 3D design model of the component.

[0049] The design model can include 3D digital coordinates of the entire construction of the component, including the exterior and interior surfaces of the component. For example, the design model can define the body, surfaces, and / or internal passages, such as openings, support structures, etc. In one exemplary embodiment, the three-dimensional design model is converted into a plurality of slices or segments, for example, along the central (e.g., vertical) axis of the component or any other suitable axis. Each slice can define a thin cross-section of the component for a predetermined height of the slice. Multiple consecutive cross-sectional slices together form the 3D component. The component is then "built" slice by slice or layer by layer until it is complete.

[0050] In this manner, the components described herein can be manufactured using an additive process, or more specifically, each layer is formed successively, for example, by melting or polymerizing plastic using laser energy or heat, or by sintering or melting metal powder. For example, certain types of additive manufacturing processes can use an energy beam, such as an electron beam or electromagnetic radiation such as a laser beam, to sinter or melt powdered material. Any suitable laser and laser parameters can be used, including considerations regarding power, laser beam spot size, and scan speed. The build material can be formed from any suitable powder or material selected for strength, durability, and longevity, particularly at high temperatures.

[0051] Each successive layer may be, for example, between approximately 10 μm and 200 μm, but the thickness may be selected based on any number of parameters and may have any suitable dimensions according to alternative embodiments. Thus, utilizing the additive forming methods described above, the components described herein may have a cross-section as thin as one thickness (e.g., 10 μm) of the associated powder layer used in the additive forming process.

[0052] Furthermore, using additive processes, the surface finish and characteristics of a component can be varied according to the needs of the application. For example, the surface finish can be adjusted (e.g., made smoother or rougher) by selecting appropriate laser scanning parameters (e.g., laser power, scanning speed, laser focal spot size, etc.) during the additive process, particularly at the periphery of a cross-sectional layer corresponding to the surface of the part. For example, a rougher finish can be achieved by increasing the laser scanning speed or reducing the size of the formed melt pool, and a smoother finish can be achieved by reducing the laser scanning speed or increasing the size of the formed melt pool. The scanning pattern and / or laser power can also be varied to change the surface finish of a selected area.

[0053] Notably, in exemplary embodiments, several features of the components described herein were previously impossible to achieve due to manufacturing limitations. However, the inventors have advantageously leveraged current advances in additive manufacturing technology to develop exemplary embodiments of such components generally in accordance with the present disclosure. While the present disclosure is not generally limited to the use of additive manufacturing to form these components, additive manufacturing does offer a variety of manufacturing advantages, including ease of manufacture, reduced costs, and greater precision.

[0054] In this regard, using additive manufacturing methods, even multi-part components can be formed as a single, continuous piece of metal, and thus may include fewer subcomponents and / or joints compared to existing designs. Integrating these multi-part components through additive manufacturing can advantageously improve the overall assembly process. For example, integration reduces the number of separate parts that must be assembled, thereby reducing the associated time and overall assembly costs. Furthermore, existing issues related to, for example, leakage, joint quality between separate parts, and overall performance can be advantageously reduced.

[0055] Further, the additive manufacturing methods described above enable more complex shapes and contours of the components described herein. For example, such components can include thin additive manufactured layers, unique pseudo-flange geometries, customized cooling cavity sizes and shapes, and / or customized cooling fluid passage numbers, shapes, and paths. As a specific example, using additive manufacturing methods such as described herein, one or more housing segments of a compressor housing can be formed with uniquely shaped outer surface protrusions that define one or more cavities and / or one or more passages therein. Further, the cross-sectional shape, number, and / or relative position of each cavity and passage within the protrusions can vary between the protrusions of the housing segments. Further, while additive manufacturing enables the manufacture of a single monolithic component such as described herein from a single material, additive manufacturing processes also enable the manufacture of a single component with different materials, such that different portions of the component can exhibit different performance characteristics. The continuous, additive nature of the manufacturing process enables the construction of these novel features. As a result, the components described herein can exhibit improved performance and reliability.

[0056] It should be appreciated that the accelerator 100 described herein has a passage 102 with a compound exit angle for fluid flow through the passage, for purposes of explaining aspects of the subject matter only. For example, the accelerator 100 is used herein to describe example configurations, structures, and methods of manufacturing the accelerator 100. It should be appreciated that the additive manufacturing techniques discussed herein can be used to manufacture other housings or similar components for any suitable device, for any suitable purpose, and for any suitable industry. Thus, the example components and methods described herein are for purposes of illustrating example aspects of the subject matter only and are not intended to limit the scope of the disclosure in any way.

[0057] Having now presented the structure and configuration of the accelerator 100 according to example embodiments of the subject matter, an example method 500 for forming an accelerator according to example embodiments of the subject matter is provided. A manufacturer can use the method 500 to form the outer wall 108 and the inner wall 110 that define the passage 102 therebetween, along with the various other features described herein, and thus form the accelerator 100 or any other suitable accelerator. It should be appreciated that the example method 500 is discussed herein only to describe example aspects of the subject matter and is not intended to be limiting.

[0058] Reference is now made to Figure 5Method 500 includes, at block 502, depositing a layer of additive material on a bed of an additive manufacturing machine. Method 500 further includes, at block 504, selectively directing energy from an energy source onto the layer of additive material to melt a portion of the additive material and form an accelerator. For example, the accelerator may be 100 formed for the HP turbine 28 of the core turbine engine 16 of the turbofan jet engine 10 described herein. More specifically, as described herein, accelerator 100 may include an annular outer wall 108, an annular inner wall 110, an annular channel 102 defined between outer wall 108 and inner wall 110, and one or more vanes 112 disposed within the channel. Channel 102 may include an inlet 104 for allowing a cooling fluid F to enter channel 102 and an outlet 106 for allowing the cooling fluid F to exit channel 102. One or more vanes 112 may each extend from outer wall 108 to inner wall 110 at a location adjacent to channel outlet 106. In addition, the channel outlet 106 can be angled such that the outlet angle α of the cooling fluid F is non-zero relative to both the radial direction R and the axial direction A defined by the accelerator 100. Using the additive manufacturing process of method 500, the outer wall 108, the inner wall 110, and the vanes 112 are integrally formed as a single, unitary component. It should be understood that the accelerator 100 formed by the additive process of method 500 can also include any or all of the additional features described herein, such as the flange 116 having the hole 118 defined therein, the connector 122, and the flanges 136, 140.

[0059] Thus, the present subject matter relates to components, systems, and methods for providing cooling flow to a rotor blade stage. More specifically, the present subject matter relates to an accelerator that introduces a tangential velocity component into the cooling air (e.g., turbine stage 1 cooling air) that is greater than the rotor speed to minimize parasitic power losses in the rotor cavity and pressure losses in the cooling supply circuit (e.g., stage 1 blade cooling supply circuit). Furthermore, the accelerator described herein provides efficient pumping characteristics to minimize the temperature of the blade cooling flow. Furthermore, as described herein, the accelerator can be additively manufactured to achieve optimized blade geometry and aerodynamic performance beyond conventional casting techniques. Furthermore, the accelerator described herein includes compound exit angles for the cooling fluid, which enables a smaller axial footprint of the engine while maintaining rotor clearance, and enables a close coupling between the accelerator and the rotor blade while maintaining rotor clearance. More importantly, the accelerator described herein reduces the arc-shaped exit velocity drop between the accelerator outlet and the cooling plate inlet, which increases the close coupling between the accelerator and the rotor blade stage while reducing the travel length and velocity degradation of the cooling fluid jet, thereby improving cooling system performance. Other benefits and advantages of the present subject matter may also be achieved.

[0060] Further aspects of the invention are provided by the subject matter of the following clauses:

[0061] An accelerator for a gas turbine engine, the accelerator defining a radial direction and an axial direction, the accelerator comprising an annular outer wall; an annular inner wall; an annular passage defined between the outer wall and the inner wall, the passage having an inlet for entry of a cooling fluid into the passage and an outlet for exit of the cooling fluid from the passage; and a plurality of vanes disposed within the passage, each vane of the plurality of vanes extending from the outer wall to the inner wall proximate the outlet, wherein the outlet is angled such that an exit angle of the cooling fluid is non-zero with respect to the radial direction and non-zero with respect to the axial direction.

[0062] The accelerator of any of the preceding clauses, wherein the outer wall, the inner wall, and the plurality of vanes are integrally formed as a single unitary component.

[0063] The accelerator of any of the preceding clauses, wherein the outlet is angled radially inward such that the inlet is disposed radially outward of the outlet.

[0064] The accelerator of any of the preceding clauses, wherein each vane of the plurality of vanes has a shape configured to induce a tangential flow of the cooling fluid as the cooling fluid exits from the outlet.

[0065] The accelerator of any of the preceding clauses, wherein the passage defines a width from the inner wall to the outer wall, and wherein the width varies along the passage from the inlet to the outlet.

[0066] The accelerator of any of the preceding clauses, wherein the passage includes an intermediate portion between the inlet and the outlet, and wherein the width of the passage decreases from the inlet to the intermediate portion and from the intermediate portion to the outlet such that the width at the inlet is greater than the width at the outlet.

[0067] The accelerator of any of the preceding clauses, wherein the inner wall is angled with respect to the axial direction.

[0068] The accelerator of any of the preceding clauses, wherein the passage includes an intermediate portion between the inlet and the outlet, wherein the inner wall is defined at a first non-zero angle with respect to the axial direction over a first length defined from the inlet to the intermediate portion, and wherein the inner wall is defined at a second non-zero angle with respect to the axial direction over a second length defined from the intermediate portion to the outlet.

[0069] The accelerator of any of the preceding clauses, wherein the first non-zero angle is greater than the second non-zero angle.

[0070] The accelerator of any of the preceding clauses, further comprising an annular flange extending radially outward from the outer wall.

[0071] An accelerator as in any preceding clause, wherein the flange defines a plurality of apertures therein, the plurality of apertures being spaced apart from one another around a circumference of the flange.

[0072] An accelerator as in any preceding clause, wherein the flange is substantially parallel to the radial direction.

[0073] An accelerator according to any preceding clause, wherein the outer wall, inner wall, plurality of vanes and flange are integrally formed as a single unitary component.

[0074] An accelerator according to any of the preceding clauses, further comprising a connector defined between the inlet end of the outer wall and the flange, wherein the connector is substantially parallel to the axial direction.

[0075] An accelerator according to any preceding clause, wherein the outer wall, inner wall, plurality of vanes, flange and connector are integrally formed as a single unitary component.

[0076] An accelerator according to any of the preceding clauses, further comprising an inner wall flange extending axially forward from the inner wall, wherein the channel includes a middle portion, the middle portion being located between the inlet and the outlet, and wherein the inner wall flange extends from the inner wall adjacent to the middle portion so that a fillet is defined between the inner wall at the middle portion and the inner wall flange.

[0077] An accelerator according to any preceding clause, wherein the outer wall, inner wall, plurality of vanes and inner wall flange are integrally formed as a single unitary component.

[0078] An accelerator according to any preceding clause, wherein the outer wall, the inner wall, the plurality of vanes, the flange defining the plurality of apertures therein, the connector and the inner wall flange are integrally formed as a single unitary component.

[0079] The accelerator according to any of the preceding clauses, further comprising a second inner wall flange defined at the inlet end of the inner wall, the second inner wall flange extending substantially in a radial direction.

[0080] An accelerator as in any preceding clause, wherein the outer wall, inner wall, plurality of vanes and second inner wall flange are integrally formed as a single unitary component.

[0081] An accelerator according to any preceding clause, wherein the outer wall, the inner wall, the plurality of vanes, the flange defining the plurality of apertures therein, the connector, the inner wall flange and the second inner wall flange are integrally formed as a single unitary component.

[0082] An accelerator according to any of the preceding clauses, further comprising an outer wall flange defined at the outlet end of the outer wall, the outer wall flange extending generally in a radial direction.

[0083] The accelerator of any of the preceding clauses, wherein the outer wall flange is slightly angled with respect to the radial direction.

[0084] The accelerator of any of the preceding clauses, wherein the outer wall, the inner wall, the plurality of vanes, and the outer wall flange are integrally formed as a single unitary component.

[0085] The accelerator of any of the preceding clauses, wherein the outer wall, the inner wall, the plurality of vanes, the flange defining the plurality of holes therein, the connector, the inner wall flange, the second inner wall flange, and the outer wall flange are integrally formed as a single unitary component.

[0086] The accelerator of any of the preceding clauses, wherein the accelerator is formed by depositing layers of additive material on a bed of an additive manufacturing machine; and selectively directing energy from an energy source onto the layers of additive material to melt a portion of the additive material, wherein the outer wall, the inner wall, and the plurality of vanes are integrally formed as a single unitary component.

[0087] The accelerator of any of the preceding clauses, wherein the outlet defines a compound outlet angle for the cooling fluid.

[0088] A method of manufacturing an accelerator for a gas turbine engine, the method comprising depositing layers of additive material on a bed of an additive manufacturing machine; and selectively directing energy from an energy source onto the layers of additive material to melt a portion of the additive material and form an accelerator, the accelerator comprising an annular outer wall, an annular inner wall, an annular passage defined between the outer wall and the inner wall, and vanes disposed within the passage, wherein the passage includes an inlet for the cooling fluid to enter the passage and an outlet for the cooling fluid to exit the passage, wherein the vanes extend from the outer wall to the inner wall proximate the outlet, wherein the outlet is angled such that an outlet angle of the cooling fluid has a non-zero radial portion and a non-zero axial portion, and wherein the outer wall, the inner wall, and the vanes are integrally formed as a single unitary component.

[0089] The method of any of the preceding clauses, wherein the accelerator further comprises an annular flange extending radially outward from the outer wall, wherein the flange is integrally formed with the outer wall.

[0090] The method of any of the preceding clauses, wherein the flange defines a plurality of holes therein, the plurality of holes being defined about a circumference of the flange.

[0091] The method of any of the preceding clauses, wherein the flange is disposed radially outward from the outlet such that the flange and the outlet define a back end of the accelerator.

[0092] A gas turbine engine comprising: a combustor; a first turbine stator vane stage disposed directly downstream of the combustor, the first turbine stator vane stage comprising an annular array of stator vane airfoils; a first turbine rotor blade stage disposed directly downstream of the first turbine stator vane stage, the first turbine rotor blade stage comprising an annular array of rotor blade airfoils coupled to a rotatable shaft; and an accelerator circumferentially surrounding the shaft, the accelerator comprising an annular passage for receiving a cooling fluid, the passage comprising an outlet defining a compound outlet angle for the cooling fluid, wherein the outlet of the accelerator is disposed directly upstream of the first turbine rotor blade stage to direct the cooling fluid to the first turbine rotor blade stage.

[0093] This written description uses examples to disclose the application, including the best mode, and also to enable any person skilled in the art to practice the application, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the application is defined by the claims, and can include other examples that occur to those skilled in the art. Such other examples are intended to fall 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. An accelerator for a gas turbine engine, the accelerator defining a radial direction and an axial direction, characterized in that: The accelerator comprises: annular outer wall; annular inner wall; an annular channel having a width, the annular channel being defined between the outer wall and the inner wall, the channel having an inlet for a cooling fluid to enter the channel and an outlet for the cooling fluid to exit the channel, wherein the width of the annular channel continuously decreases between the inlet and the outlet; and a plurality of vanes disposed within the passage, each vane of the plurality of vanes extending from the outer wall to the inner wall adjacent the outlet, wherein the outlet is angled such that an outlet angle of the cooling fluid is non-zero with respect to the radial direction and non-zero with respect to the axial direction.

2. The accelerator according to claim 1, characterized in that in, The outer wall, the inner wall, and the plurality of vanes are integrally formed as a single, unitary component.

3. The accelerator according to claim 1, characterized in that in, The outlet is angled radially inwardly such that the inlet is disposed radially outwardly of the outlet.

4. The accelerator according to claim 1, wherein in, Each vane of the plurality of vanes has a shape configured to induce a tangential flow of the cooling fluid as the cooling fluid exits the outlet.

5. The accelerator according to claim 1, characterized in that in, The channel defines a width from the inner wall to the outer wall, and wherein the width varies along the channel from the inlet to the outlet.

6. The accelerator according to claim 5, characterized in that in, The channel includes a middle portion located between the inlet and the outlet, and wherein the width of the channel decreases both from the inlet to the middle portion and from the middle portion to the outlet, such that the width at the inlet is greater than the width at the outlet.

7. The accelerator according to claim 1, characterized in that in, The inner wall is angled relative to the axial direction.

8. The accelerator according to claim 7, characterized in that in, The channel includes a middle portion located between the inlet and the outlet, wherein the inner wall is defined at a first non-zero angle relative to the axial direction over a first length, and wherein the inner wall is defined at a second non-zero angle relative to the axial direction over a second length, the first length being defined from the inlet to the middle portion, and the second length being defined from the middle portion to the outlet.

9. The accelerator according to claim 8, characterized in that in, The first non-zero angle is greater than the second non-zero angle.

10. The accelerator according to claim 1, wherein Further including: An annular flange extends radially outward from the outer wall.

11. The accelerator according to claim 10, characterized in that in, The flange defines a plurality of holes therein, the plurality of holes being spaced apart from one another around a circumference of the flange.

12. The accelerator according to claim 10, characterized in that in, The flange is substantially parallel to the radial direction.

13. The accelerator according to claim 10, wherein: Further including: a connector defined between the inlet end of the outer wall and the flange, Wherein, the connector is substantially parallel to the axial direction.

14. The accelerator according to claim 10, characterized in that Further including: an inner wall flange, the inner wall flange extending axially forward from the inner wall, wherein the channel comprises a middle portion, the middle portion being located between the inlet and the outlet, and The inner wall flange extends from the inner wall adjacent the middle portion such that a rounded corner is defined between the inner wall and the inner wall flange at the middle portion.

15. The accelerator according to claim 1, wherein in, The accelerator comprises a plurality of layers formed by: depositing layers of additive material on a bed of an additive manufacturing machine; as well as selectively directing energy from an energy source onto the layer of additive material to melt a portion of the additive material, Wherein, the outer wall, the inner wall and the plurality of blades are integrally formed as a single integral component.

16. A method of manufacturing an accelerator for a gas turbine engine, characterized in that: The method comprises: depositing layers of additive material on a bed of an additive manufacturing machine; and selectively directing energy from an energy source onto the additive material layer to melt a portion of the additive material and form the accelerator, the accelerator comprising an annular outer wall, an annular inner wall, an annular channel defined between the outer wall and the inner wall, and blades disposed within the channel, wherein the channel comprises an inlet for a cooling fluid to enter the channel and an outlet for the cooling fluid to flow out of the channel, the channel having a width, wherein the width of the channel continuously decreases between the inlet and the outlet, wherein the vanes extend from the outer wall to the inner wall adjacent to the outlet, wherein the outlet is angled such that the outlet angle of the cooling fluid has a non-zero radial portion and a non-zero axial portion, and Wherein, the outer wall, the inner wall and the blade are integrally formed into a single integral component.

17. The method according to claim 16, characterized in that in, The accelerator further includes an annular flange extending radially outward from the outer wall, wherein the flange is integrally formed with the outer wall.

18. The method according to claim 17, characterized in that in, The flange defines a plurality of holes therein, the plurality of holes being defined around a circumference of the flange.

19. The method according to claim 17, wherein in, The flange is disposed radially outward from the outlet such that the flange and the outlet define a rearward end of the accelerator.

20. A gas turbine engine, characterized in that: include: burner; a first turbine stator vane stage disposed directly downstream of the combustor, the first turbine stator vane stage comprising an annular array of stator vane airfoils; a first turbine rotor blade stage disposed directly downstream of the first turbine stator bucket stage, the first turbine rotor blade stage comprising an annular array of rotor blade airfoils coupled to a rotatable shaft; as well as an accelerator circumferentially surrounding the shaft, the accelerator comprising an annular passage for receiving a cooling fluid, the passage having an inlet for admitting the cooling fluid into the passage, the passage including an outlet defining a compound exit angle for the cooling fluid, the passage having a width, wherein the width of the passage continuously decreases between the inlet and the outlet, The outlet of the accelerator is arranged directly upstream of the first turbine rotor blade stage to guide the cooling fluid to the first turbine rotor blade stage.

Images