U.S. patent application number 13/915393 was filed with the patent office on 2014-12-11 for shape memory alloy intersegment seals.
The applicant listed for this patent is General Electric Company. Invention is credited to Sukriti GUPTA, Niraj Kumar MISHRA.
Application Number | 20140361499 13/915393 |
Document ID | / |
Family ID | 52004817 |
Filed Date | 2014-12-11 |
United States Patent
Application |
20140361499 |
Kind Code |
A1 |
GUPTA; Sukriti ; et
al. |
December 11, 2014 |
SHAPE MEMORY ALLOY INTERSEGMENT SEALS
Abstract
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.
Inventors: |
GUPTA; Sukriti; (Bangalore,
IN) ; MISHRA; Niraj Kumar; (Bangalore, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company |
Schenectady |
NY |
US |
|
|
Family ID: |
52004817 |
Appl. No.: |
13/915393 |
Filed: |
June 11, 2013 |
Current U.S.
Class: |
277/650 |
Current CPC
Class: |
F01D 11/005 20130101;
F05D 2300/505 20130101; F05D 2240/57 20130101 |
Class at
Publication: |
277/650 |
International
Class: |
F01D 11/00 20060101
F01D011/00 |
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.degree. F. to
2400.degree. 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.degree. F. to about 2400.degree. 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.
Description
BACKGROUND OF THE INVENTION
[0001] This application relates generally to rotary machines and
more particularly, to shape-memory alloy seals for sealing flow
paths in a turbomachine.
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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 INVENTION
[0006] In 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.
[0007] 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.degree. F. to about 2400.degree. 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.
[0008] 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.
[0009] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a diagrammatic, fragmentary and
partially-sectioned view of a portion of a gas turbine;
[0011] FIG. 2 is a simplified, schematic side view of a
shape-memory alloy seal extending between two gas turbine gas path
components in accordance with a first exemplary embodiment, the
seal being shown in an inoperative condition or state;
[0012] FIG. 3 shows the seal of FIG. 2 in an operative, expanded
condition or state upon heating above a transition temperature of
the shape-memory alloy;
[0013] FIG. 4 shows the seal of FIGS. 1 and 2 in a second
inoperative condition or state upon cooling of the shape-memory
alloy to a temperature below its transition temperature;
[0014] FIG. 5 is a side elevation of a shape-memory alloy seal in
accordance with a second exemplary but nonlimiting embodiment of
the invention;
[0015] FIG. 6 is a schematic side view of the shape-memory alloy
seal shown in FIG. 5, in an operative, expanded condition or
state;
[0016] FIG. 7 shows the shape-memory alloy seal of FIG. 6, but also
showing in dotted lines, a partially retracted, second inoperative
condition or state;
[0017] FIG. 8 is a perspective view of a shape-memory alloy seal in
accordance with a third exemplary but nonlimiting embodiment;
[0018] FIG. 9 is a perspective view of a shape-memory alloy seal in
accordance with a fourth exemplary but nonlimiting embodiment;
and
[0019] FIG. 10 is a perspective view of a shape-memory alloy seal
in accordance with a fifth exemplary but nonlimiting
embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Referring now to FIG. 1, there is illustrated a
representative example of a turbine section of a gas turbine,
generally designated at 10. Hot combustion gases from an annular
array of combustors, not shown, are supplied to the turbine through
a like number of transition pieces 12 that introduce the gases into
an annular hot gas path 14 which extends axially through the
various turbine stages. Each stage comprises a plurality of
circumferentially-spaced buckets mounted on individual turbine
wheels forming part of the turbine rotor assembly, and a plurality
of stationary, circumferentially-spaced stator vanes. For example,
the first turbine stage may include a plurality of
circumferentially-spaced buckets 16 mounted on a first-stage rotor
wheel 18 and a plurality of stationary, circumferentially-spaced
stator vanes 20 (comprising the first stage nozzle assembly)
located upstream of the buckets. Similarly, the second stage may
include a plurality of buckets 22 mounted on a rotor wheel 24 and a
plurality of stationary, circumferentially-spaced stator vanes 26
(comprising the second stage nozzle assembly). Additional stages
may be provided, for example, a third stage comprised of a
plurality of circumferentially-spaced buckets 28 mounted on a
third-stage rotor wheel 30 and a plurality of stationary,
circumferentially-spaced stator vanes 32 (comprising the third
stage nozzle assembly). It will be appreciated that the stator
vanes 20, 26 and 32 are mounted on and fixed to the turbine casing
(or stator), while the buckets 16, 22 and 28 and wheels 18, 24 and
30 form part of the turbine rotor assembly. Between the rotor
wheels 18, 24 and 30 are spacers 34 and 36, which also form part of
the turbine rotor. It will be appreciated that compressor discharge
air is present in a region 37 disposed radially inwardly of the
buckets and is used to cool, for example, the root portions of the
buckets, thus establishing an axially-directed cooling air flow
radially inward of the hot gas path 14.
[0021] 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.
[0022] FIG. 1 also illustrates other exemplary locations at 54 and
56 where seals may be applied to minimize radially-outward leakage
in gaps between confronting stationary surfaces. Other locations
where seals as described herein may be employed include confronting
stationary and rotating components as indicated, for example at 58
where the rotating spacer 34 confronts the stationary inner nozzle
ring 60. Similar locations are found in connection with all of the
turbine stages along the gas path.
[0023] FIG. 2 illustrates diagrammatically an exemplary seal
installation amenable to the utilization of a shape-memory alloy
seal. Here, the shape-memory alloy seal (shown diagrammatically at
62) is seated within adjacent grooves 64, 66 of respective,
adjacent stationary components 68, 70. The segments 68, 70
represent any confronting stationary surfaces along the gas path
where leakage may occur along a gap 72 between the confronting
surfaces of the components. The seal 62 in accordance with
exemplary embodiments described below may be a constructed of a
shape-memory alloy that is designed to change shape in response to,
for example, temperatures experienced in use. The change in shape
is due to a temperature related, solid state micro-structural phase
change that enables the alloy to change from one physical shape to
another physical shape. The shape change may be manifest as a
change in size, i.e., expanded but similarly shaped, and/or a
change in shape, i.e., expanded to a different shape (generally
referred to herein as a shape change).
[0024] 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.
[0025] 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.degree. F. and 2400.degree.
F. specified in the elevated temperature environment of
turbomachinery.
[0026] 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 (FIG. 2) or another intermediate (or second) but
still inoperative shape (FIG. 4) when the temperature drops below
the critical or transition temperature. The two-way seal has the
added benefit of facilitating removal of the seal upon cooling
below the transition temperature.
[0027] In FIG. 5, a shape-memory alloy seal 74 in accordance a
second exemplary but nonlimiting embodiment is shown in its normal
(room temperature) or inoperative shape or state. The seal 74 is
formed to include a pair of flexible, profiled portions, or curls
76, 78 at opposite ends of a flat middle portion 80. It is the end
curls 76, 78 that provide the sealing function. When heated above
the predetermined critical or transition temperature of the
shape-memory alloy, the seal 74 will deform to an operative shape,
where the end curls expand to engage surfaces of the respective
adjacent components, for example, surfaces within the grooves 64,
66 of the segments 68, 70 in FIG. 2, to thereby prevent radial
leakage through the gap 72 between the segments. The expansion of
the end curls 76, 78 is shown diagrammatically in FIG. 6. It will
be appreciated that if the seal alloy changes shape in the middle
section 80, and if that aspect of the shape change is not needed to
achieve the desired sealing, the middle section may be physically
confined to minimize or even prevent shape change in that section
of the seal by confining the middle section within any
substantially-rigid structure, as exemplified at 82. As explained
above, the seal curls 76, 78 could revert to the shape shown in
FIG. 5 upon cooling below the transition temperature; or revert to
an intermediate or second inoperative shape as shown dotted lines
in FIG. 7. Thus, it is possible to control the shape of the seal as
a function of temperature, as dictated by the properties of the
materials used.
[0028] In another exemplary but nonlimiting example illustrated in
FIG. 8, a shape-memory alloy seal 84 is comprised of an elongated
center portion 86 and a pair of end curls 88, 90 at opposite ends
of the center portion. In this exemplary embodiment, the center
portion 86 is formed integrally with a rigid reinforcement plate 92
bonded thereto by welding, brazing, adhesive or other suitable
means. The center portion 86 thus facilitates assembly and
placement of the seal but does not in and of itself contribute to
the sealing function. It is the flexible end curls 76, 78 that
provide the sealing function, exhibiting one-way or two-way
shape-change characteristics as described above.
[0029] The end curls 86, 88 may have a normal (room-temperature)
inoperative shape as shown in FIG. 8. When heated above its
transition or critical temperature in use, the end curls 86, 88
will expand in a manner similar to the expanded end curls 76, 78
described in connection with FIGS. 5-7. In a two-way version of the
seal, the curls 86, 88 will return to their original shape or to
some intermediate but still inoperative inoperative shape as
determined by material properties and temperatures.
[0030] FIG. 9 illustrates a variation of the seal shown in FIG. 8.
Here, the opposite ends of the seal 94 are formed with double end
curls 96, 98, i.e., each end is formed with a pair of curls or
convolutions 100, 102 and 104, 106, respectively. The center
section 108 is again rigidified by a reinforcement plate 110,
otherwise similar to the plate 92 in the embodiment shown in FIG.
8. This arrangement provides for extended sealing range and
increased sealing bias, useful in specific applications. Here
again, one or two-way shape-change characteristics as described
above are contemplated.
[0031] FIG. 10 illustrates another exemplary embodiment where the
shape-memory seal 112 is formed as a cloth seal with shape-memory
alloy features substantially as described above. Specifically, the
seal is formed with a center section 114 and opposite end curls
116, 118. The center section 114 is sandwiched between rigid plates
120, 122 one or both of which may be covered with conventional
cloth seal fabric. The end curls 116, 118 are formed to exhibit
one-way or two-way shape-change characteristics as described
above.
[0032] 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.
[0033] 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.
* * * * *