Patent Grant
8011894
The present application relates generally to any type of turbine and more particularly relates to systems and methods for sealing a gap formed between a turbine bucket dovetail and a turbine rotor via a pivot plate and a rope seal.
Gas turbines generally include a turbine rotor (wheel) with a number of circumferentially spaced buckets (blades). The buckets generally may include an airfoil, a platform, a shank, a dovetail, and other elements. The dovetail of each bucket is positioned within the turbine rotor and secured therein. The airfoils project into the hot gas path so as to convert the kinetic energy of the gas into rotational mechanical energy. A number of cooling medium passages may extend radially through the bucket to direct an inward and/or an outward flow of the cooling medium therethrough.
Leaks may develop in the coolant supply circuit based upon a gap between the tabs of the dovetails and the surface of the rotor due to increases in thermal and/or centrifugal loads. Air losses from the bucket supply circuit into the wheel space may be significant with respect to blade cooling medium flow requirements. Moreover, the air may be extracted from later compressor stages such that the penalty on energy output and overall efficiency may be significant during engine operation.
Efforts have been made to limit this leak. For example, one method involves depositing aluminum on a dovetail tab so as to fill the gap at least partially. Specifically, a circular ring may be pressed against the forward side of the dovetail face. Although this design seals well and is durable, the design cannot be easily disassembled and replaced in the field. Rather, these rings may only be disassembled when the entire rotor is disassembled.
There is thus a desire for improved dovetail tab sealing systems and methods. Such systems and methods should adequately prevent leakage therethrough so as to increase overall system efficiency while being installable and/or repairable in the field.
The present application thus provides a sealing system for sealing a gap between a dovetail tab of a bucket and a rotor. The sealing system may include a sealing slot positioned about the dovetail tab and a pivot plate positioned within the sealing slot. The sealing slot may include a pivot point and a rest ledge such that the pivot plate pivots about the pivot point and into the gap when the bucket rotates.
The present application further provides a sealing system for sealing a gap between a dovetail tab of a bucket and a rotor. The sealing system may include a sealing slot positioned about the dovetail tab, a pivot plate positioned within the sealing slot, and a rope seal positioned about the pivot plate. The sealing slot may include a pivot point and a rest ledge such that the pivot plate pivots about the pivot point and into the gap when the bucket rotates.
The present application further provides a method of sealing a gap between a dovetail tab of a bucket and a rotor. The method may include positioning a pivot plate within a sealing slot of the dovetail tab, rotating the bucket, and pivoting the pivot plate into the gap under centrifugal force. The method further may include positioning a seal about the plate and deforming the seal against the sealing slot when the bucket rotates.
These and other features of the present application will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims.
a is a side plan view of a dovetail tab that may be used with the sealing systems as are described herein.
Referring now to the drawings, in which like numerals refer to like elements throughout the several views,
As is known, the bucket 10 may include an airfoil 30, a platform 40, a shank 50, a dovetail 60, and other elements. It will be appreciated that the bucket 10 is one of a number of circumferentially spaced buckets 10 secured to and about the rotor 20 of the turbine. The bucket 10 of
As described above, the rotor 20 may have a number of slots 25 for receiving the dovetails 60 of the buckets 10. Likewise, the airfoils 30 of the buckets 10 project into the hot gas stream so as to enable the kinetic energy of the stream to be converted into mechanical energy through the rotation of the rotor 20. The dovetail 60 may include a first tang or tab 70 and a second tab 80 extending therefrom. Similar designs may be used herein. A gap 90 may be formed between the ends of the tabs 70, 80 of the dovetail 60 and the rotor 20. A high pressure cooling flow may escape via the gap 90 unless a sealing system of some type is employed.
The sealing system 100 also may include a plate 140. The plate 120 may be positioned within the sealing slot 110. The plate 140 may be made out of conventional metals. The plate 140 may have a substantially curved shape so as to largely conform to the shape of the sealing slot 110. Specifically, the plate 140 defines two upper arms 150 that extend between the pivot point 120 and the rest ledge 130. As is described in more detail below, the sealing slot 110 has a certain amount of give between the pivot point 120 and the rest ledge such that the plate 140 can pivot therein. The plate 140 further defines a wedge 160 below the two upper arms 150. The wedge 160 largely conforms to the size and shape of the tab 70.
Positioned about one side of the plate 140 may be a rope seal 170. The rope seal 170 may be made out of graphite, braded metallics, and similar types of substantially deformable, temperature resistant materials. The rope seal 170 may have a largely circular cross-section although other shapes may be used herein. Likewise, a plate seal that extends across the plate 140 in whole or in part and other configurations may be used herein.
As is shown in
As is shown in
Use of the sealing system 100 thus reduces leakage through the gap 90. Sealing efficiency similar to that of the commonly used aluminum coating thus may be found and improved upon without the use of the aluminum material. The reduction of cooling flow thus improves overall system efficiency. The sealing system 100 may be used with other sealing systems and methods.
It should be apparent that the foregoing relates only to certain embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.
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| Number | Date | Country | |
|---|---|---|---|
| 20100008769 A1 | Jan 2010 | US |
