MULTI-SHELL TURBINE CASING SYSTEM
A multi-shell turbine casing system comprises at least one supporting cell joined to at least one retaining cell. The at least one supporting cell has at least one supporting cell wall and at least one truss section. The at least one retaining cell has at least one retaining cell wall. According to the invention, the at least one supporting cell wall and the at least one retaining cell wall form an outer shell and an inner shell. In an exemplary embodiment, the at least one truss section is oriented to provide support for the inner shell and is a triangular truss comprising cylindrical members joined by plate-type or box-type connectors. An exemplary truss section includes a plurality of horizontally oriented stabilizers joining the vertically oriented member to the outer shell. A multi-shell casing system may include additional truss sections, which may be joined to one another and to adjacent structure.
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The subject matter disclosed herein relates generally to casing systems for gas turbines and more specifically to a lightweight, reinforced casing system for a low-pressure section of a power generating gas turbine.
Gas turbines used for power generating applications, such as steam turbines, have steadily increased in size over the years. Due to their increasing size, those skilled in the art have sought effective means for reducing the weight of power generating gas turbines. Therefore, while gas turbines once typically employed casing systems constructed entirely of cast iron, today's turbines frequently employ casing systems of welded, multi-shell construction. For example, an example of a casing system comprises an outer exhaust hood that is structurally coupled to an inner shroud.
The casing system of a gas turbine typically serves the purposes of supporting the engine's rotating turbo-machinery and the static structure that surrounds that machinery as well as containing the flow of working fluid, e.g., steam, passing through the gas turbine. In order to improve thermal efficiency, it is important that the static structure be dimensionally stable so as to reduce clearances between the turbo-machinery and the static structure. It is also important that the casing system that supports the rotating turbo-machinery and withstands differential pressures associated with expansion of the working fluid be sufficiently strong to bear loads associated with the turbo-machinery. As a result, while those skilled in the art have sought to reduce weight in turbine casing systems, it is also recognized that strength and rigidity are important design criteria.
In power generating (i.e., low-pressure or LP) turbine sections of gas turbines, the size and weight of the rotating turbo-machinery is typically greater than that of other engine sections. In addition, as the size of power generating turbines continues to grow, the weight of LP casing systems has also continued to increase. To provide the necessary strength with acceptable weight, designers have implemented structural reinforcements. Unfortunately, these reinforcements can cause obstructions to airflow, resulting in undesirable aerodynamic blockages.
Accordingly, those skilled in the art seek LP turbine casing systems with decreased weight and aerodynamic blockage.
BRIEF DESCRIPTION OF THE INVENTIONAccording to the invention, a multi-shell turbine casing system comprises at least one supporting cell joined to at least one retaining cell. The at least one supporting cell has at least one supporting cell wall and at least one truss section. The at least one retaining cell has at least one retaining cell wall. According to the invention, the at least one supporting cell wall and the at least one retaining cell wall form an outer shell and an inner shell. Accordingly, a multi-shell casing system is provided with improved stiffness for withstanding differential pressures, sealing against leakages, and resisting compression under weight of turbo-machinery and with reduced axial aerodynamic blockage.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
DETAILED DESCRIPTION OF THE INVENTIONReferring now to the drawings, in which like numerals refer to like elements throughout the several views,
As one skilled in the art will appreciate, outer shell 101 (also known as an exhaust hood) supports inner shell 102 (also known as an inner casing or inner shroud) for supporting static structure and sealing arrangements of a gas turbine and for constraining a flow of gas as it expands through the stages of the gas turbine. Thus, inner shell 102 forms a substantially enclosed envelope for containing the working fluid within the inner shell 102 despite differential pressure forces that arise as a result of expansion of the gas through the turbine stages. In addition, the elements forming inner shell 102 are configured to cooperate with one another so as to form a sealed surface suitable for substantially resisting gas leakages into or out of the envelope created by inner shell 102. Outer shell 101 provides support for inner shell 102 so as to improve its rigidity and reduce flexing and movement of inner shell 102, which could adversely affect turbine clearances and thereby impact performance and/or durability of an installed engine.
To improve strength of the casing system while reducing weight, casing system 100 includes stiffening plates that are oriented vertically to add stiffness and to resist compression under weight of static elements that are to be supported by the inner shell 102 of casing system 100 and to withstand gas pressures exerted on the inner shell. It should be appreciated that where design considerations call for strength in supporting weight, vertical orientations of the truss sections may be favored. However, where structural integrity is intended for resisting strain arising from differential pressure loads, other supporting orientations, such as horizontal and other intermediate angles, will be appropriate. The stiffening plates are also arranged and configured so as to improve structural integrity at locations of supporting pads that are positioned and configured to provide structural support for rotating turbo-machinery. This use of stiffening plates helps to facilitate the segmentation of casing system 100. Inner shell 102 is supported on outer shell 101 through the plate arrangement formed in casing system 100, particularly in first supporting cell 110, and second supporting cell 120. This arrangement is configured to provide sufficient stiffness to fortify inner shell 102 against differential pressure loads and other loads, e.g., the weight of the turbo-machinery, that inner shell 102 will support, i.e., vertically and/or in other orientations as discussed above.
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In combination, walls of first supporting cell 210, second supporting cell 220, first retaining cell 230, and second retaining cell 240 form a multi-shell casing system comprising outer shell 201, also known as an exhaust hood, and inner shell 202. Inner shell 202 is supported on outer shell 201 through the plate arrangement formed in casing system 200, primarily in first supporting cell 210, and second supporting cell 220. This support arrangement is configured to provide sufficient stiffness to fortify inner shell 202 against the weight of the turbo-machinery and differential pressures that inner shell 202 will support, i.e., vertically and in other directions.
As shown in
To enhance the rigidity and strength of first supporting cell 210, first truss 260 also includes a plurality of stabilizers 266, 267, 268 joining connector 263 to plates 213 and 214 and to cell wall 215, which forms a portion of outer shell 201. Similarly, a base end of first truss 260 includes a plurality of stabilizers 269, 270, 271 joining connector 265 to plates 213 and 214 and to cell wall 215. Thus, first truss 260 lends stability and strength to first supporting cell 210 with decreased weight and aerodynamic blockage. The reduced blockage associated with the trusses also helps to reduce or avoid vacuum pull issues that can arise from incorporation of structure within first supporting cell 210 and second supporting cell 220.
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To enhance the rigidity and strength of second supporting cell 220, second truss 280 also includes a plurality of stabilizers 286, 287, 288 joining connector 283 to plates 221 and 222 and to cell wall 225, which forms a portion of outer shell 201. Similarly, a base end of second truss 280 includes a plurality of stabilizers 289, 290, 291 joining connector 285 to plates 221 and 222 and to cell wall 225. Thus, second truss 280 lends stability and strength to second supporting cell 220 with decreased weight and aerodynamic blockage.
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In combination, walls of first supporting cell 510, second supporting cell 520, third supporting cell 530, first retaining cell 540, second retaining cell 550, and third retaining cell 560 form a multi-shell casing system comprising outer shell 501 and inner shell 502. Inner shell 502 is supported by outer shell 501, and the plate arrangement formed in first supporting cell 510, second supporting cell 520, and third supporting cell 530 reinforces casing system 500. This arrangement is configured to provide sufficient stiffness to fortify inner shell 502 and to resist excessive deformation under loads that are to be supported by inner shell 502. For example, inner shell 502 is configured so as to maintain (e.g., by sealing) and withstand (e.g., through structural integrity) differential pressures resulting from expansion of the working fluid in the turbine. Thus leakages are to be prevented through sealing, and turbine hardware, bearings, and sealing arrangements are supported.
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To enhance the rigidity and strength of second supporting cell 520, each truss 523, 524, 525 includes a plurality of stabilizers, which join each box-type connector to adjacent structure of second supporting cell 520. For example, truss 524 also includes a plurality of stabilizers 586, 587, 588 joining connector 584 to the box-type connectors of trusses 523, 525 and to cell wall 529, which forms a portion of outer shell 501. Similarly, a base end of truss 524 includes a plurality of stabilizers 589, 590, 591 joining connector 585 to adjacent box-type connectors of trusses 523, 525 and to cell wall 529. Plate 521 and cell wall 529 of second supporting cell 520 include stress distribution panels for coupling to stabilizers of trusses 523, 524, 525 and for distributing stresses and transmitting loads carried by those stabilizers. Thus, trusses 523, 524, and 525 lend stability and strength to second supporting cell 520 with decreased weight and aerodynamic blockage.
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Accordingly, a multi-shell casing system for low pressure stages of gas turbines is provided with improved stiffness for resisting loads imposed on the casing system such as differential pressure loads, loads imposed by supporting static structure of a gas turbine and, where desirable, loads from weight of turbo-machinery supported by the casing system. This improved system also reduces the amount of structural materials used for specific designs, resulting in weight and cost benefits. In addition, the improved system reduces axial aerodynamic blockage, resulting in improvements in cycle performance. Finally, the invention helps to reduce or avoid vacuum pull issues associated with conventional plate stiffening systems.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
Claims
1. A multi-shell turbine casing system comprising:
- at least one supporting cell joined to at least one retaining cell,
- the at least one supporting cell having at least one supporting cell wall,
- the at least one retaining cell having at least one retaining cell wall, and
- the at least one supporting cell wall and the at least one retaining cell wall forming an outer shell and an inner shell,
- wherein the supporting cell comprises at least one truss section.
2. A multi-shell turbine casing system as in claim 1, wherein the at least one truss section is oriented and configured to resist compression under weight of turbo-machinery supported by the inner shell.
3. A multi-shell turbine casing system as in claim 1, wherein the at least one truss section is triangular.
4. A multi-shell turbine casing system as in claim 1, wherein the at least one truss section comprises at least three members.
5. A multi-shell turbine casing system as in claim 1, wherein the at least one truss section comprises a plurality of members joined by one or more plate-type connectors.
6. A multi-shell turbine casing system as in claim 1, wherein the at least one truss section comprises a plurality of members joined by one or more box-type connectors.
7. A multi-shell turbine casing system as in claim 1, wherein the at least one truss section comprises at least one vertically oriented member and a plurality of horizontally oriented stabilizers joining the at least one vertically oriented member to the outer shell.
8. A multi-shell turbine casing system as in claim 7, wherein a plurality of the plurality of horizontally oriented stabilizers are joined to a base end of the at least one vertically oriented member.
9. A multi-shell turbine casing system as in claim 7, wherein a plurality of the plurality of horizontally oriented stabilizers are joined to a distal end of the at least one vertically oriented member.
10. A multi-shell turbine casing system as in claim 7, wherein at least one of the plurality of horizontally oriented stabilizers are joined to a wall of the outer shell.
11. A multi-shell turbine casing system as in claim 1, comprising two or more vertically oriented truss sections configured to provide structural support for the inner shell.
12. A multi-shell turbine casing system as in claim 11, wherein one of the vertically oriented truss sections comprises a first vertically oriented member and the other truss section comprises a second vertically oriented member, the system further comprising at least one horizontally oriented stabilizer joining the first vertically oriented member to the second vertically oriented member.
13. A multi-shell turbine casing system as in claim 11, further comprising at least one horizontally oriented stabilizer joining at least one vertically oriented member to a wall of the outer shell.
14. A multi-shell turbine casing system as in claim 13, wherein the horizontally oriented stabilizer is joined to a distal end of the vertically oriented member.
15. A multi-shell turbine casing system as in claim 13, wherein the horizontally oriented stabilizer is joined to a base end of the vertically oriented member.
16. A multi-shell turbine casing system as in claim 1, comprising three or more vertically oriented truss sections configured to provide structural support for the inner shell.
17. A multi-shell turbine casing system as in claim 16, wherein one of the vertically oriented truss sections comprises a first vertically oriented member and a second of the truss sections comprises a second vertically oriented member and a third of the truss sections comprises a third vertically oriented member, the system further comprising at least one horizontally oriented stabilizer joining the first vertically oriented member to the second vertically oriented member and at least one horizontally oriented stabilizer joining the second vertically oriented member to the third vertically oriented member.
18. A multi-shell turbine casing system as in claim 17, further comprising at least one horizontally oriented stabilizer joining the vertically oriented member to a wall of the outer shell.
19. A multi-shell turbine casing system as in claim 17, wherein the supporting cell comprises at least one vertically oriented plate and at least one horizontally oriented stabilizer joining the vertically oriented member to the plate.
20. A multi-shell turbine casing system as in claim 18, wherein the wall comprises at least one stress distribution panel for distributing load transmitted by the horizontally oriented stabilizer.
Type: Application
Filed: Jul 18, 2011
Publication Date: Jan 24, 2013
Applicant: GENERAL ELECTRIC COMPANY (Schenectady, NY)
Inventors: Ravi Kumar Nethi (Bangalore), Gonoor Rajendra (Bangalore)
Application Number: 13/185,026
International Classification: F01D 25/26 (20060101);