Patent Application
20100008782
The present application relates generally to any type of turbine and more particularly relates to systems and methods for sealing a gap between a turbine blade dovetail and a turbine rotor slot via a compliant 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 360-degree 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 describes a compliant seal assembly for sealing a gap between a dovetail tab of a bucket and a slot of a rotor. The compliant sealing assembly may include a sealing groove positioned about the slot and a compliant seal positioned about the sealing groove. The compliant seal is forced into the gap and about the dovetail tab when the bucket rotates.
The present application further provides a method of sealing a gap between a dovetail tab of a bucket and a slot of a rotor. The method may include the steps of machining a sealing groove about the slot of the rotor, positioning a compliant seal about the sealing groove, rotating the bucket, and forcing the compliant seal into the gap and about the dovetail tab.
The present application further provides for a compliant seal assembly for sealing a gap between a dovetail tab of a bucket and a slot of a rotor. The compliant seal assembly may include a sealing groove positioned about the slot and a compliant seal positioned about the sealing groove. The compliant seal is forced into the gap via centrifugal force and conforms about the dovetail tab 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.
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.
A compliant seal 120 may be positioned within the sealing slot 110. The compliant seal 120 may be made out of any type of metallic, elastic seal material. The compliant seal 120 may be largely U-shaped and may conform to the shape of the sealing groove 110, i.e., the compliant seal 120 may have a square or circular cross-section or any desired cross-sectional shape.
As is shown in
As is shown in
Use of the complaint sealing system 100 thus reduces leakage through the gap 90. Moreover, the use of the compliant seal 120 addresses the larger variations in the size range of the gap 90. No modifications are required to the bucket 10 or the rotor 20. Sealing efficiency similar to that of the commonly used aluminum coating thus may be found or improved upon without the use of the additional mass of material. The reduction in cooling flow loss thus improves overall system efficiency. High-pressure air savings may be about one percent (1%) or so. The compliant 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.
