RADIAL SPLINE ARRANGEMENT FOR LPT VANE CLUSTERS
A full hoop stator vane cluster includes an inner hoop and an outer hoop both being substantially cylindrical and coaxial. A plurality of airfoils extend radially between the hoops, and a plurality of vane splines extend radially outward from the outer hoop for attaching the vane cluster to a gas turbine engine.
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The present invention relates generally to gas turbine engines, and more particularly to the attachment of a full hoop stator vane cluster to a case of a gas turbine engine.
A gas turbine engine typically includes a high pressure spool, a combustion system and a low pressure spool disposed within an engine case to form a generally axial, serial flow path about the engine centerline. The high pressure spool includes a high pressure turbine, a high pressure shaft extending axially forward from the high pressure turbine, and a high pressure compressor connected to a forward end of the high pressure shaft. The low pressure spool includes a low pressure turbine, which is disposed downstream of the high pressure turbine, a low pressure shaft, which typically extends coaxially through the high pressure shaft, and a low pressure compressor connected to a forward end of the low pressure shaft, forward of the high pressure compressor. The combustion system is disposed between the high pressure compressor and the high pressure turbine and receives compressed air from the compressors and fuel provided by a fuel injection system. A combustion process is carried out within the combustion system to produce high energy gases to produce thrust and turn the high and low pressure turbines, which drive the compressors to sustain the combustion process.
Turbines are comprised of alternating stages of blades and airfoils that are arranged radially around a center axis of the engine within the axial flow path of the engine case. More specifically, the blades are attached to a support rotor and the airfoils are attached to the engine case. When high energy gases pass through a turbine, heat is transferred to the airfoils and the case. Due to local gas flow paths and component features and geometry, thermal expansion is not equal over the entire turbine section. Similarly, the case and the airfoils may not expand equally during operation and contract equally after operation. This phenomenon can cause thermal stresses and crack formation that can lead to failure of the components.
SUMMARYAccording to the present invention, a full hoop stator vane cluster includes an inner hoop and an outer hoop both being substantially cylindrical and coaxial. A plurality of airfoils extend radially between the hoops, and a plurality of vane splines extend radially outward from the outer hoop for attaching the vane cluster to a gas turbine engine.
In another embodiment, a gas turbine engine includes a full hoop stator vane cluster and a case. The full hoop stator vane cluster includes an inner hoop and an outer hoop both being substantially cylindrical and coaxial. A plurality of airfoils extend radially between the hoops, and a plurality of vane splines extend radially outward from the outer hoop for attaching the vane cluster to a gas turbine engine. The case is substantially cylindrical and has a plurality of case splines extending radially inward for attaching the vane cluster.
In another embodiment, a method of installing a full hoop stator vane cluster into a gas turbine engine includes inserting the vane cluster axially into a case of the gas turbine engine. Also included are moving a plurality of vane splines on the vane cluster alongside a plurality of case splines on the case and circumferentially offsetting the vane splines and the case splines. Further included are rotating the vane cluster such that the vane splines are circumferentially aligned with the case splines and attaching a vane spline to a case spline to substantially restrain relative axial and circumferential movement.
In the illustrated embodiment, gas turbine engine 10 comprises a dual-spool turbofan engine in which the advantages of the present invention are particularly well illustrated. Gas turbine engine 10, of which the operational principles are well known in the art, comprises fan 12, low pressure compressor (LPC) 14, high pressure compressor (HPC) 16, combustor section 18, high pressure turbine (HPT) 20, and low pressure turbine (LPT) 22, which are each concentrically disposed around longitudinal engine centerline axis CL. Fan 12 is enclosed at its outer diameter within fan case 23A. Likewise, the other engine components are correspondingly enclosed at their outer diameters within various engine casings, including LPC case 23B, HPC case 23C, HPT case 23D (including the mid-turbine frame), and LPT case 23E. Fan 12 and LPC 14 are connected to LPT 22 through shaft 24, and together fan 12, LPC 14, LPT 22, and shaft 24 comprise the low pressure spool. HPC 16 is connected to HPT 20 through shaft 26, and together HPC 16, HPT 20, and shaft 26 comprise the high pressure spool.
Inlet air A enters engine 10 where it is divided into streams of primary air AP and secondary air AS after passing through fan 12. Fan 12 is rotated by low pressure turbine 22 through shaft 24 (either directly as shown or through a gearbox, not shown) to accelerate secondary air AS (also known as bypass air) through exit guide vanes 28, thereby producing a major portion of the thrust output of engine 10. Primary air AP (also known as gas path air) is directed first into low pressure compressor 14 and then into high pressure compressor 16. LPC 14 and HPC 16 work together to incrementally step up the pressure of primary air A. HPC 16 is rotated by HPT 20 through shaft 24 to provide compressed air to combustor section 18. The compressed air is delivered to combustor 18, along with fuel through injectors 30, such that a combustion process can be carried out to produce the high energy gases necessary to turn high pressure turbine 20 and low pressure turbine 22, which is comprised of blades 32 and vane clusters 34 (which includes airfoils 36). Primary air AP continues through gas turbine engine 10 whereby it is typically passed through an exhaust nozzle to further produce thrust.
After being compressed in LPC 14 and HPC 16 and participating in a combustion process in combustor 18 (
Depicted in
In
Vane cluster 34 includes substantially cylindrical inner hoop 42 surrounded by substantially cylindrical outer hoop 44. Vane cluster 34 has cluster axis 46, to which inner hoop 42 and outer hoop 44 are coaxial. Connected to and extending radially between inner hoop 42 and outer hoop 44 is a plurality of airfoils 36. Because vane cluster 34 subtends substantially a full cylinder, vane cluster 34 is a full hoop stator vane cluster.
Attached to and extending radially outward from outer hoop 44 is a plurality of vane splines 40. In the illustrated embodiment, each vane spline 40 is comprised of two vane prongs 48. Vane prongs 48 extend generally radially outward from outer hoop 44 and are substantially parallel to each other. Vane prongs 48 are circumferentially separated from each other by vane slots 50. Each vane slot 50 is circumferentially wider than each vane prong 48.
Blades 32 are connected to shaft 24 (shown in
The components and configuration of vane cluster 34 as shown in
In
LPT case 23E is substantially cylindrical and is coaxial with longitudinal engine centerline axis CL (shown in
In order to attach vane cluster 34 to LPT case 23E, cluster axis 46 (shown in
In order to assemble LPT 22 (shown in
The components, configuration, and operation of vane cluster 34 and LPT case 23E allow for vane cluster 34 to be attached to LPT case 23E. Because fasteners 58 are positioned in vane slots 50 and case slots 56, relative movement between vane cluster 34 and LPT case 23 is substantially prohibited in the axial and circumferential directions. Relative movement is permitted in the radial direction. In addition, vane cluster 34 can be moved past case splines 52, which allows for the assembly of a multi-stage LPT 22 (shown in
In
Vane cluster 34 and LPT case 23E are as described previously in
The components and configuration of LPT case 23E and vane cluster 34 as shown in
In
In alternate embodiment vane splines 40′, each pair of vane prongs 48′ are joined at the outermost ends of vane prongs 48′. Thereby, vane slots 50′ are surrounded by a closed ring comprised of vane prongs 48′. Similarly, in the alternate embodiment case splines 52′, each pair of case prongs 54′ are joined at the innermost ends of case prongs 54′. Thereby, case slots 56′ are surrounded by a closed ring comprised of case prongs 56′. In the illustrated embodiment, vane splines 40′ and case splines 52′ are substantially the same shape. Alternatively, case splines 52′ can be of a corresponding shape to vane splines 40′, such that case slots 56′ can align with vane slots 50′ (for example, case splines 52 as shown in
The components and configuration of alternate embodiment vane splines 40′ as shown in
It should be recognized that the present invention provides numerous benefits and advantages. For example, LPT case 23E and vane cluster 34 can independently thermally expand during operation of gas turbine engine 10. Similarly, after operation of gas turbine engine 10 ceases, LPT case 23E and vane cluster 34 can independently thermally contract. For another example, when gas turbine engine 10 is cooled, vane splines 40 and/or case splines 52 can bear the weight of vane cluster 34. This prevents knife edge seals 60 from being crushed by the radially movable vane cluster 34.
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims
1. A full hoop stator vane cluster comprising:
- an inner hoop having a substantially cylindrical shape;
- an outer hoop having a substantially cylindrical shape and being substantially coaxial with the inner hoop;
- a plurality of airfoils extending radially between the inner hoop and the outer hoop; and
- a plurality of vane splines extending radially outward from the outer hoop for attaching the vane cluster to a gas turbine engine.
2. The vane cluster of claim 1, wherein a vane spline comprises:
- two substantially parallel vane prongs that are circumferentially separated from each other.
3. The vane cluster of claim 2, wherein the prongs are joined circumferentially outward from the outer hoop, such that each vane spline includes a closed ring.
4. The vane cluster of claim 2, wherein an amount of circumferential separation between the vane prongs is wider than a circumferential width of each vane prong.
5. The vane cluster of claim 2, wherein an amount of circumferential separation between two consecutive vane splines is wider than a circumferential width of an individual vane spline.
6. A gas turbine engine comprising:
- a full hoop stator vane cluster comprising: an inner hoop having a substantially cylindrical shape; an outer hoop having a substantially cylindrical shape and being substantially coaxial with the inner hoop; a plurality of airfoils extending radially between the inner hoop and the outer hoop; and a plurality of vane splines extending radially outward from the outer hoop; and
- a case having a substantially cylindrical shape and including a first plurality of case splines extending radially inward for attaching to the vane cluster.
7. The gas turbine engine of claim 6, wherein a vane spline comprises:
- two substantially parallel vane prongs that are circumferentially separated from each other.
8. The gas turbine engine of claim 7, wherein the vane prongs are joined circumferentially outward from the outer hoop, such that each vane spline forms a closed ring.
9. The gas turbine engine of claim 7, wherein an amount of circumferential separation between two consecutive vane splines is wider than a circumferential width of an individual vane spline.
10. The gas turbine engine of claim 6, wherein a case spline comprises:
- two substantially parallel case prongs that are circumferentially separated from each other.
11. The gas turbine engine of claim 10, wherein the case prongs are joined circumferentially inward from the case, such that each case spline forms a closed ring.
12. The gas turbine engine of claim 10, wherein an amount of circumferential separation between two consecutive case splines is wider than a circumferential width of an individual case spline.
13. The gas turbine engine of claim 6, wherein the vane splines and the case splines are substantially the same shape.
14. The gas turbine engine of claim 6, and further comprising:
- a second plurality of case splines axially separated from the first plurality of case splines such that the plurality of vane splines can be interposed between the first and second pluralities of case splines.
15. The gas turbine engine of claim 6, and further comprising:
- a plurality of fasteners oriented substantially axially that attach the vane cluster to the case, each fastener connecting a vane spline to a case spline.
16. The gas turbine engine of claim 6, wherein an amount of circumferential separation between two consecutive vane splines is wider than a circumferential width of an individual case spline.
17. The gas turbine engine of claim 6, wherein an amount of circumferential separation between two consecutive case splines is wider than a circumferential width of an individual vane spline.
18. A method of installing a full hoop stator vane cluster into a gas turbine engine, the method comprising:
- inserting the vane cluster axially into a case of the gas turbine engine;
- offsetting circumferentially the vane splines from the case splines, such that the vane splines are aligned between the case splines;
- rotating the vane cluster such that the vane splines are circumferentially aligned with the case splines; and
- attaching a vane spline to a case spline to substantially restrain relative axial and circumferential movement.
19. The method of claim 18, and further comprising:
- moving the vane splines axially between two sets of case splines.
20. The method of claim 18, wherein attaching the vane spline to the case spline comprises:
- inserting a fastener substantially axially between the case prongs of the case spline and between the vane prongs of the vane spline.
Type: Application
Filed: Jun 29, 2011
Publication Date: Jan 3, 2013
Applicant: UNITED TECHNOLOGIES CORPORATION (Hartford, CT)
Inventors: Ioannis Alvanos (West Springield, MA), Gabriel L. Suciu (Glastonbury, CT)
Application Number: 13/172,279
International Classification: F01D 5/22 (20060101); B21K 25/00 (20060101);