SHAPE MEMORY ALLOY INTERSEGMENT SEALS
A high-temperature seal for use in sealing gaps between adjacent turbine components includes a seal body constructed of a shape-memory alloy having inoperative size and shape that, in use, expands to an operative size and shape where it is in sealing engagement with the adjacent turbine component upon reaching a predetermined transition temperature. Upon subsequent cooling to a temperature below the predetermined temperature, the seal body reverts to the first inoperative shape or to another inoperative size and shape.
This application relates generally to rotary machines and more particularly, to shape-memory alloy seals for sealing flow paths in a turbomachine.
At least some known rotary machines such as, but not limited to, steam turbines and gas turbines, include a plurality of seal assemblies in a steam-flow path, air path, or combustion gas path to facilitate increasing operating efficiency. Typically, the seal assemblies are positioned between adjacent stationary components (for example, between a high-pressure area and a low pressure area of a stationary nozzle assembly comprised of multiple arcuate segments), or between a stationary component, e.g., a nozzle assembly) and a rotary component (for example, a rotor wheel supporting an annular array of buckets) to prevent leakage into or out of the hot gas path.
Known seal assemblies include seals such as, but not limited to, brush seals, leaf seals, shingle seals, etc. In the context of a rotary machine, the seals are also typically provided in the form of arcuate segments arranged in an annular array about the machine rotor.
At least some known seal assemblies include a seal housing and an adjustable clearance control mechanism that is coupled to the stationary component. The seal housing includes at least a high-pressure-side front wall that is separated from a low-pressure-side back wall by a fixed gap that is set by the manufacturer. The clearance control mechanism actuates the seal housing including the seals to adjust a clearance between seal tips and the rotary component. Because current seal systems often involve springs that are biased in a given direction, typically opposite the actuation direction, seal assembly and/or installation is hindered by the fact that such springs must oftentimes be compressed to permit installation and in many cases removal of the seals. In addition, the mechanical, hydraulic or pneumatic mechanisms required to actuate such springs add complexity and expense.
It would therefore be desirable to provide a unique seal arrangement that simplifies operation and reduces assembly installation and/or replacement time, thereby providing an overall increase in the efficiency of, for example, a steam or gas turbine.
BRIEF DESCRIPTION OF THE INVENTIONIn one exemplary but nonlimiting embodiment, there is provided a high-temperature seal for use in sealing gaps between adjacent turbine components comprising a seal body constructed of a shape-memory alloy having a first inoperative size and shape that, in use, expands to a predetermined operative size and shape where it is in sealing engagement with the adjacent turbine component upon reaching a predetermined transition temperature, and upon subsequent cooling to a temperature below the predetermined temperature, reverts to a second inoperative size and shape different than the first inoperative size and shape.
In another exemplary aspect, there is provided a high-temperature seal for use in sealing gaps between adjacent turbine components comprising a seal body including substantially planar center portion and a pair of profiled end portions, at least the profiled portions formed of a shape-memory alloy material designed to expand upon exposure to temperatures in a range of from about 600° F. to about 2400° F. to an operative shape, thereby causing the profiled portions to engage surfaces of the adjacent turbine components; and wherein the profiled end portions are designed to revert to an inoperative shape when the temperatures drop below the range.
In still another aspect, there is provided a high-temperature seal for use in sealing gaps between surfaces of adjacent turbine components comprising a seal body including substantially planar center portion and a pair of profiled end portions each profiled end portion comprising at least one curl; at least the pair of profiled end portions formed of a shape-memory alloy material designed to change shape upon heating to temperatures higher than a predetermined transition temperature from an inoperative shape to an operative shape, thereby causing the profiled end portions to expand and establish a seal between the surfaces of the adjacent turbine components; and wherein the center portion is rigidified by a separate seal component and covered with a cloth seal fabric.
These and other aspects, advantages and salient features of the invention will become apparent from the following detailed description, in conjunction with the drawings identified below.
Referring now to
Referring to the first stage of the turbine, the stator vanes 20 forming the first-stage nozzle assembly are disposed between inner and outer bands 38 and 40, respectively, supported from the turbine casing. As noted above, the nozzle assembly of the first stage is formed of a plurality of arcuate vane segments, with stator vanes extending between the inner and outer bands 38, 40. A nozzle retaining ring 44 connected to the turbine casing is coupled to the outer band and secures the first-stage nozzle assembly. Shroud segments 46 arranged in an annular array, surround the rotatable buckets, e.g., the buckets 16 of the first stage. The shroud segments include an axial facing surface 50, which lies in sealing engagement with a confronting axial facing surface 48 of the nozzle-retaining ring 44. A seal 52 is shown at the interface to prevent leakage along a gap between these surfaces from the high pressure region to a lower pressure region. This is one of several locations where a seal as described herein may be employed.
In the manufacture of an article intended to change shape during operation, the article (a seal in this case) is formed to have an operative shape at or above a transition temperature. This operative shape is developed by working and annealing an article preform of the alloy at or above a temperature at which the solid state micro-structural phase change occurs. The temperature at which such phase change occurs generally is called the critical or transition temperature of the alloy.
For purposes of this invention, near-equiatomic Nb—Ru and Ta—Ru alloys have been found to be particularly well-suited, with transition temperatures of between 600° F. and 2400° F. specified in the elevated temperature environment of turbomachinery.
Depending on specific applications, the shape-memory alloy seal 62 may have one-way or two-way shape characteristics. For example, the shape-memory alloy seal 62 may transition change to an operative shape upon reaching its predetermined temperature, and remain in that operative shape after the seal cools below the transition temperature. A two-way seal on the other hand, reverts to an inoperative shape, which may be its original first, inoperative shape (
In
In another exemplary but nonlimiting example illustrated in
The end curls 86, 88 may have a normal (room-temperature) inoperative shape as shown in
For all of the above-described embodiments, it will be appreciated that whether the sealing surfaces engage or simply establish predetermined clearances under operating conditions will depend on specific applications, for example, whether both surface are stationary, or if one of the adjacent surfaces is rotating, etc.
While various embodiments are described herein, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made by those skilled in the art, and are within 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 essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims
1. A high-temperature seal for use in sealing gaps between adjacent turbine components comprising:
- a seal body constructed of a shape-memory alloy having a first inoperative size and shape that, in use, expands to a predetermined operative size and shape where it is in sealing engagement with the adjacent turbine component upon reaching a predetermined transition temperature, and upon subsequent cooling to a temperature below the predetermined temperature, reverts to a second inoperative size and shape different than said first inoperative size and shape.
2. The high-temperature seal of claim 1 wherein said seal body is provided with a planar center portion constructed of a substantially rigid alloy material and a pair of end portions constructed of an alloy with shape-memory characteristics.
3. The high-temperature seal of claim 2 wherein said center portion is comprised of shape-memory alloy material but is rigidified by a separate seal component attached to said center portion.
4. The high-temperature seal of claim 2 wherein said end portions each comprise a single curl.
5. The high-temperature seal of claim 2 wherein said end portions each comprise a double curl.
6. The high-temperature seal of claim 2 wherein at least said planar center portion is wrapped with a cloth seal material.
7. The high-temperature seal of claim 1 wherein said predetermined transition temperature lies in a range of from 600° F. to 2400° F.
8. The high-temperature seal of claim 1 wherein said seal body is rectangular in its first inoperative shape
9. The high-temperature seal of claim 1 wherein said seal body is substantially rectangular in its second inoperative shape but larger in size that in its first inoperative shape.
10. A high-temperature seal for use in sealing gaps between adjacent turbine components comprising a seal body including substantially planar center portion and a pair of profiled end portions, at least said profiled portions formed of a shape-memory alloy material designed to expand upon exposure to temperatures in a range of from about 600° F. to about 2400° F. to an operative shape, thereby causing said profiled portions to engage surfaces of said adjacent turbine components; and wherein said profiled end portions are designed to revert to an inoperative shape when the temperatures drop below said range.
11. The high-temperature seal of claim 10 wherein said substantially planar center portion comprises a substantially rigid alloy material with or without shape-memory characteristics.
12. The shape-memory alloy seal of claim 10 wherein said profiled end portions each comprise a single curl.
13. The shape-memory alloy seal of claim 10 wherein said profiled end portions each comprise a double curl.
14. The shape-memory alloy seal of claim 10 wherein said substantially planar center portion is wrapped with a cloth seal material.
15. A high-temperature seal for use in sealing gaps between surfaces of adjacent turbine components comprising:
- a seal body including substantially planar center portion and a pair of profiled end portions each profiled end portion comprising at least one curl; at least said pair of profiled end portions formed of a shape-memory alloy material designed to change shape upon heating to temperatures higher than a predetermined transition temperature from a first inoperative shape to an operative shape, thereby causing said profiled end portions to expand and establish a seal between said surfaces of said adjacent turbine components; and wherein said center portion is rigidified by a separate seal component and covered with a cloth seal fabric.
16. The high-temperature seal of claim 15 wherein said separate seal component and said cloth seal fabric cover both sides of said substantially planar center portion.
17. The high-temperature seal of claim 15 wherein at least said profiled end portions exhibit one-way shape-change characteristics.
18. The high-temperature seal of claim 15 wherein said exhibit two-way shape-change characteristics.
19. The high-temperature seal of claim 18 wherein said profiled end portions revert to said inoperative shape at temperatures below said transition temperatures.
20. The high-temperature seal of claim 18 wherein said profiled end portions revert to a second inoperative shape other than said first inoperative shape at temperatures below said transition temperature.
Type: Application
Filed: Jun 11, 2013
Publication Date: Dec 11, 2014
Inventors: Sukriti GUPTA (Bangalore), Niraj Kumar MISHRA (Bangalore)
Application Number: 13/915,393
International Classification: F01D 11/00 (20060101);