U.S. patent application number 12/038424 was filed with the patent office on 2015-03-26 for high temperature shape memory alloy actuators.
This patent application is currently assigned to General Electric Company. The applicant listed for this patent is Ronald Scott Bunker, Liang Jiang, Don Mark Lipkin. Invention is credited to Ronald Scott Bunker, Liang Jiang, Don Mark Lipkin.
Application Number | 20150083281 12/038424 |
Document ID | / |
Family ID | 41010438 |
Filed Date | 2015-03-26 |
United States Patent
Application |
20150083281 |
Kind Code |
A1 |
Lipkin; Don Mark ; et
al. |
March 26, 2015 |
HIGH TEMPERATURE SHAPE MEMORY ALLOY ACTUATORS
Abstract
A high temperature component having an actuator body including
an actuatable portion comprising a shape memory alloy containing
one more of Ni, Al, Nb, Ti and Ta and a platinum-group metal. The
shape memory alloy has an altered geometry at a predetermined
temperature. The actuator is also capable of operation in and is
resistant to high temperature oxidizing atmospheres. A method for
forming an actuator and a method for high temperature control are
also disclosed.
Inventors: |
Lipkin; Don Mark;
(Niskayuna, NY) ; Jiang; Liang; (Schenectady,
NY) ; Bunker; Ronald Scott; (Niskayuna, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lipkin; Don Mark
Jiang; Liang
Bunker; Ronald Scott |
Niskayuna
Schenectady
Niskayuna |
NY
NY
NY |
US
US
US |
|
|
Assignee: |
General Electric Company
Schenectady
NY
|
Family ID: |
41010438 |
Appl. No.: |
12/038424 |
Filed: |
February 27, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11964677 |
Dec 26, 2007 |
|
|
|
12038424 |
|
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Current U.S.
Class: |
148/563 ;
148/402 |
Current CPC
Class: |
C22F 1/10 20130101; F05D
2300/505 20130101; C22C 19/00 20130101; C22F 1/006 20130101; F01D
11/001 20130101; C21D 2201/01 20130101 |
Class at
Publication: |
148/563 ;
148/402 |
International
Class: |
C22F 1/00 20060101
C22F001/00 |
Claims
1. A high temperature gas turbine engine component comprising: an
actuator body, the actuator body having an actuatable portion
comprising a nickel-aluminum shape memory alloy containing one more
elements selected from the group consisting of Nb, Ti, Ta and
combinations thereof and a platinum-group metal selected from the
group consisting of Pt, Pd, Rh, Ru, Ir and combinations thereof,
the nickel-aluminum based shape memory alloy having an altered
geometry above a predetermined temperature; and wherein a portion
of the actuator body is bonded to a surface of the high temperature
gas turbine component along a wheelspace path, and wherein the
altered geometry of the actuatable portion disrupts a gas flow path
through the wheelspace path; and wherein the actuator body is
resistant to high temperature oxidizing atmospheres.
2. (canceled)
3. The turbine engine component of claim 1, wherein the
predetermined temperature is reached or exceeded by the turbine
engine component during operation, the actuatable portion being
substantially in a martensite phase below the predetermined
temperature and substantially in an austenite phase above the
predetermined temperature.
4. (canceled)
5. (canceled)
6. The turbine engine component of claim 1, wherein the actuator
body further comprises a superalloy.
7. The turbine engine component of claim 1, wherein the shape
memory alloy is resistant to oxidation at a temperature up to about
1150.degree. C.
8. The turbine engine component of claim 1, wherein the
nickel-aluminum based shape memory alloy comprises an alloy of the
following formula: (A.sub.1-xPGM.sub.x).sub.0.5+yB.sub.0.5-y
wherein A is an element selected from the group consisting of Ni,
and combinations of Ni and Co or Fe; B is an element selected from
the group consisting of Al, and combinations of Al and Cr, Hf, Zr,
La, Y, Ce, Ti, Mo, W, Nb, Re, Ta or V; PGM is a platinum-group
element selected from the group consisting of Pt, Pd, Ru, Rh, Ir
and combinations thereof, x is from greater than 0 to about 1
atomic fraction and y is from about 0 to about 0.23 atomic
fraction.
9. The turbine engine component of claim 8, wherein the
nickel-aluminum based shape memory alloy comprises an alloy of the
following formula: (A.sub.1-xPGM.sub.x).sub.0.5+yB.sub.0.5-y
wherein x is from about 0.05 to about 0.6 atomic fraction, and y is
from about 0.01 to about 0.2 atomic fraction.
10. The turbine engine component of claim 1, wherein the
nickel-aluminum based shape memory alloy comprises an alloy of the
following formula: (A.sub.1-xPGM.sub.x).sub.0.5+yB.sub.0.5-y
wherein A is substantially Ni and Co, PGM is one or both of Pt and
Pd, B is substantially Al and Ti, and the ratio of Ti to Al is from
about 0.1 to about 10, x is from greater than 0 to about 1 atomic
fraction and y is from about 0 to about 0.23 atomic fraction.
11. The turbine engine component of claim 8, wherein the
nickle-aluminum based shape memory alloy comprises an alloy of the
following formula: (A.sub.1-xPGM.sub.x).sub.0.5+yB.sub.0.5-y
wherein B further comprises up to 10 at % Cr and up to 2 at % of
one or both of Hf, Zr, and Y.
12. A high temperature gas turbine engine component comprising: an
actuator body, the actuator body having an actuatable portion
comprising a shape memory alloy, wherein the shape memory alloy
comprises an alloy of the following formula:
Ru.sub.0.5+y(Nb.sub.1-xTa.sub.x).sub.0.5-y wherein x is from about
0 to about 1 atomic fraction, and y is from about -0.06 to about
0.23 atomic fraction, the shape memory alloy having an altered
geometry above a predetermined temperature; wherein a portion of
the actuator body is bonded to a surface of the high temperature
gas turbine component along a wheelspace seal path, and wherein the
altered geometry of the actuatable portion disrupts a gas flow path
through the wheelspace seal path; and wherein the actuator body is
resistant to high temperature oxidizing atmospheres.
13. A method for forming a high temperature actuator body
comprising: providing a shape memory alloy containing one more
elements selected from the group consisting of Ni, Al, Nb, Ti, Ta
and combinations thereof and a platinum-group metal selected from
the group consisting of Pt, Pd, Rh, Ru, Ir and combinations
thereof; heating the alloy to a predetermined elevated temperature;
deforming the alloy to a geometry at the predetermined high
temperature to impart the high-temperature shape; and cooling the
alloy to form a high temperature shape memory actuator portion.
14. The method of claim 13, wherein the body is further configured
to modify a gas flow path at an elevated temperature.
15. The method of claim 13, wherein the process further comprises
affixing the actuator portion to a gas turbine engine component
16. The method of claim 13, wherein affixing comprises a process
selected from the group consisting of mechanical joining,
deposition, metallurgical bonding and combinations thereof.
17. The method of claim 16, wherein the affixing is mechanical
bonding selected from the group consisting of riveting, bolting,
bracing, wire tying and combinations thereof.
18. The method of claim 13, wherein the affixing is deposition
selected from the group consisting of arc spray, electro-spark
deposition, laser cladding, vacuum plasma spray, inert gas shrouded
thermal spray, plasma transfer arc, physical vapor deposition,
vacuum arc deposition and combinations thereof.
19. The method of claim 13, wherein the affixing is metallurgically
bonding selected from the group consisting of brazing,
co-extrusion, explosion bonding, hot-isostatic-pressing (HIP),
roll-bonding, forge-bonding, diffusion bonding, translational
friction welding, fusion welding, friction-stir welding, inertia
welding and combinations thereof
20. A method for providing high temperature actuation comprising:
providing a high temperature actuator, the actuator comprising: an
actuator body, the actuator body having an actuatable portion
comprising a shape memory alloy containing one more elements
selected from the group consisting of Ni, Al, Nb, Ti, Ta and
combinations thereof and a platinum-group metal selected from the
group consisting of Pt, Pd, Rh, Ru, Ir and combinations thereof,
the shape memory alloy having an altered geometry above a
predetermined temperature; and exposing the actuator to a
predetermined temperature to provide the actuatable portion with a
desired geometry.
21. The method of claim 20, wherein the predetermined temperature
is a temperature above which the actuatable portion exhibits a
substantially austenite phase, the predetermined temperature being
a temperature above which the turbine engine component is disposed
or operates in the deployed state.
22. The method of claim 20, wherein the altered geometry modifies a
gas flow path.
23. The method of claim 20, wherein the actuator body is affixed to
or is adjacent to a component selected from the group consisting of
a turbine nozzle, a turbine exhaust structure, a turbine shroud, a
turbine shroud hanger, a turbine blade, a turbine disk, a hot gas
path seal, a combustor and combinations thereof.
24. The method of claim 20, wherein the actuator body is fabricated
into a component selected from the group consisting of a turbine
nozzle, a turbine exhaust structure, a turbine shroud, a turbine
shroud hanger, a turbine blade, a turbine disk, a hot gas path
seal, a combustor and combinations thereof.
Description
FIELD OF THE INVENTION
[0001] The present disclosure generally relates to components, such
as gas turbine engine components, comprising structures with shape
memory alloy for actuation at high temperatures.
BACKGROUND OF THE INVENTION
[0002] In a gas turbine engine, air is pressurized in a compressor,
mixed with fuel in a combustor and is ignited to generate hot
combustion gases. The hot combustion gases flow into a turbine
section of the engine. The turbine section of the engine typically
includes a plurality of stages that may include a combination of
turbine blades and turbine vanes. The expanding combustion gases
drive the turbine by exerting pressure on the blades that rotate a
turbine shaft. The rotation of the turbine shaft is utilized to
generate electricity or produce mechanical drive power. The vanes
typically include an airfoil configuration and guide the combustion
gases to the turbine blades of the next stage of the turbine. These
combustion gases expose the turbine blades and vanes to high
temperatures and corrosive atmospheres.
[0003] Significant advances in high temperature capabilities have
been achieved through the development of high-performance
materials, including iron, nickel and cobalt-based superalloys, to
handle the combination of operating stresses and temperatures while
maintaining mechanical integrity and dimensional stability. Further
improvements in turbine efficiency and reliability have come from
the use of environmental coatings capable of protecting superalloys
from oxidation and hot corrosion. However, because no shape memory
alloys have been found to withstand the high temperatures and
oxidative atmospheres present during operation of a turbine engine,
shape-changing actuators do not exist for these and similar
high-temperature applications.
[0004] Shape memory alloys based on the Ni--Ti system have been
commercially employed in a variety of low temperature applications.
However, above temperatures of about 250.degree. C. the Ni--Ti
systems experience rapid degradation in shape memory response due
to phase changes and oxidation.
[0005] Therefore, a component comprising shape memory alloys for
use in high temperature applications is desired, having the ability
to operate and/or actuate in high temperatures and oxidative
atmospheres, such as the operational conditions of a turbine
engine.
SUMMARY OF THE INVENTION
[0006] One embodiment of the disclosure includes a high temperature
gas turbine engine component having an actuator body including an
actuatable portion comprising a shape memory alloy containing Ni,
Al, Nb, Ti and/or Ta and a platinum-group metal (PGM). The actuator
body has an altered geometry at a predetermined temperature. The
actuator is also resistant to high temperature oxidation.
[0007] Another embodiment of the disclosure includes a method for
forming a high temperature shape memory alloy for actuation. The
method includes providing a shape memory alloy containing one or
more elements selected from the group consisting of Ni, Al, Nb, Ti,
Ta and combinations thereof and a platinum-group metal selected
from the group consisting of Pt, Pd, Rh, Ru, Ir and combinations
thereof. The alloy is heated to a predetermined elevated
temperature. The alloy is then deformed at the predetermined
temperature to impart a shape memory for high temperature.
Depending on the functional needs, the shape memory alloy may be
thermo-mechanically treated iteratively to achieve better
reversibility of the shape memory alloy. The alloy is then affixed
to a structure/component to form a high temperature shape memory
actuator.
[0008] Still another embodiment of the present disclosure includes
a method for providing high temperature actuation control. The
method includes providing a high temperature actuator including an
actuator body having an actuatable portion comprising a shape
memory alloy containing one or more elements selected from the
group consisting of Ni, Al, Nb, Ti, Ta and combinations thereof and
a platinum-group metal selected from the group consisting of Pt,
Pd, Rh, Ru, Ir and combinations thereof. The actuator body has an
altered geometry at a predetermined temperature. The actuator is
resistant to high temperature oxidation. The method includes
exposing the actuator to a predetermined temperature to change the
geometry of the actuatable portion. The predetermined temperature
can be achieved via changes in environmental temperature,
electrical resistance heating, or the like.
[0009] Other features and advantages of the present disclosure will
be apparent from the following more detailed description of the
preferred embodiment, taken in conjunction with the accompanying
drawings which illustrate, by way of example, the principles of the
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows a cross-sectional view depicting a portion of
the turbine section of a gas turbine engine according to an
embodiment of the present disclosure.
[0011] FIG. 2 shows an enlarged view of a portion of the turbine
section of a gas turbine engine according to an embodiment of the
present disclosure shown in FIG. 1.
[0012] FIG. 3 shows an actuator according to an embodiment of the
present disclosure.
[0013] FIG. 4 shows an actuator according to another embodiment of
the present disclosure.
[0014] FIG. 5 shows photographs of Example 1 and Comparative
Example 2 shape memory alloy coatings subject to thermal
cycling.
[0015] FIG. 6 shows a graph of weight gain versus thermal oxidizing
cycles of Example 1 and Comparative Example 2 shape memory alloy
coatings.
[0016] Wherever possible, the same reference numbers will be used
throughout the drawings to refer to the same or like parts.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Disclosed herein are materials for use in high temperature
actuators. "Actuators", "actuate", "actuatable" and grammatical
variations thereof, as used herein, are meant to include devices or
components and motions or function including the moving or
controlling of a mechanical device or system in response to
exposure to a condition, such as exposure to a predetermined
temperature or range of temperatures. For example, a shape memory
alloy may be incorporated into an actuator, wherein the shape
memory alloy may be utilized to manipulate or move surfaces or
portions of components in a controlled manner when exposed to a
predetermined temperature. In addition, shape memory alloy
containing actuators may irreversibly deploy or otherwise move
during initial exposure to a temperature and remain substantially
motionless thereafter. The actuators, according to certain
embodiments, include components or portions of components including
one or more shape memory alloys capable of use at high temperatures
and oxidizing conditions, such as the conditions present in a gas
turbine engine.
[0018] Turbine engine components are generally formed of high
temperature alloys, such as superalloys, and are known for high
temperature performance in terms of tensile strength, creep
resistance and oxidation resistance. Examples include nickel-based
alloys, cobalt-based alloys, iron-based alloys, and titanium-based
alloys. In one embodiment, shape memory alloy material may be
fabricated into a turbine component to provide the desired
component actuator functionality. The fabrication may comprise
mechanical attachment or metallurgical bonding of the shape memory
alloy into the actuator body and/or turbine component.
[0019] Shape memory alloys according to embodiments of the present
disclosure are characterized by a temperature-dependent phase
change. These phases include a martensite phase and an austenite
phase. In the following discussion, the martensite phase generally
refers to a lower temperature phase whereas the austenite phase
generally refers to a higher temperature phase. The martensite
phase is generally more deformable, while the austenite phase is
generally less deformable. When the shape memory alloy is in the
martensite phase and is heated to above a certain temperature, the
shape memory alloy begins to change into the austenite phase. The
temperature at which this phenomenon starts is referred to as the
austenite start temperature (A.sub.s). The temperature at which
this phenomenon is complete is called the austenite finish
temperature (A.sub.f). When the shape memory alloy is in the
austenite phase and is cooled, it begins to transform into the
martensite phase. The temperature at which this phenomenon starts
is referred to as the martensite start temperature (M.sub.s). The
temperature at which the transformation to martensite phase is
completed is called the martensite finish temperature
(M.sub.f).
[0020] Shape memory alloys can exhibit a one-way shape memory
effect, an intrinsic two-way shape memory effect, or an extrinsic
two-way shape memory effect, depending on the particular alloy
composition, processing history, and--in the case of extrinsic--the
actuator construction. Annealed shape memory alloys typically only
exhibit the one-way shape memory effect. Heating above the
austenite finish temperature subsequent to low-temperature
deformation (below M.sub.f) of the shape memory material will
recover the original, high-temperature austenite (above A.sub.f)
shape. Hence, one-way shape memory effects are observed upon
heating.
[0021] Intrinsic and extrinsic two-way shape memory materials are
characterized by a shape transition both upon heating from the
martensite phase to the austenite phase, as well as upon cooling
from the austenite phase back to the martensite phase. Intrinsic
two-way shape memory behavior must be induced in the shape memory
material through processing. Such procedures may include
deformation of the material while in the martensite phase, followed
by repeated heating and cooling through the transformation
temperature under constraint. Once the material has been trained to
exhibit the two-way shape memory effect, the shape change between
the low- and high-temperature states is generally reversible and
persists through a high number of thermal cycles. In contrast,
structures that exhibit the extrinsic two-way shape memory effect
combine a shape memory alloy that exhibits a one-way effect with
another element that provides a restoring force to recover the
low-temperature shape. Examples of extrinsic two-way shape memory
effect include affixing shape memory alloy to a dissimilar
material, modifying the surface of the shape memory alloy via laser
annealing or shot peening, and the like. In such cases, a portion
of the actuator body is used to induce the one-way shape memory
actuation on heating, while another portion of the actuator body is
used to provide the shape-restoring force on cooling through the
transformation temperature.
[0022] One embodiment of the disclosure includes a method for
forming a shape memory actuator. Shape memory alloys according to
the present disclosure may be utilized in actuator mechanisms to
provide actuation in response to a predetermined temperature. The
shape memory alloys are imparted with a desired geometry and/or
configuration for actuation during operation of the actuator. The
method includes providing a shape memory alloy containing Ni, Al,
Nb, Ti, Ta or combinations thereof and a platinum-group metal. The
alloy may be made by known methods for making shape memory alloys.
For example, the alloys may be made using vacuum melting, such as
vacuum induction melting, or vacuum arc melting, to form an ingot
of the shape memory alloy composition, optionally followed by
deformation processing, such as rolling, extrusion, forging,
drawing, and/or swaging. Alternatively, the shape memory alloy can
be manufactured by deposition (e.g., thermal spray, physical vapor
deposition, vacuum arc deposition). In addition, the alloy may also
be made via powder consolidation. Once made, the alloy is heated to
a temperature sufficient to impart the desired high temperature
shape, for example to a temperature above the austenite finish
temperature. The alloy is deformed at the elevated temperature to
impart a geometry desired for high temperature operation. Upon
cooling to the martensite phase, the shape memory alloy retains the
geometry of the austenite phase. Any subsequent deformation of this
alloy below A.sub.s will be recovered upon reheating to above
A.sub.f. The reversibility of the shape memory effect can be
improved via thermo-mechanical training. This training may include
slightly deforming the alloy in the low-temperature martensite
state. An example of slightly deforming may include imparting a
plastic strain of about 2%. The alloy is then annealed at a
temperature near or above A.sub.f. The deformation and annealing
process is repeated for a number of cycles, such as one to ten
cycles, or until the desired reversibility of the shape memory
effect is attained.
[0023] Suitable shape memory alloy materials for providing
actuation include, but are not intended to be limited to,
nickel-aluminum based alloys, particularly nickel-aluminum alloys
having platinum-group metal (i.e., PGM) additions (rhodium,
ruthenium, palladium, iridium, and platinum). The alloy composition
is selected so as to provide the desired shape memory effect for
the application such as, but not limited to, transformation
temperature and strain, the strain hysteresis, actuation force,
yield strength (of martensite and austenite phases), damping
ability, resistance to oxidation and hot corrosion, ability to
actuate through repeated cycles, capability to exhibit two-way
shape memory effect, and a number of other engineering design
criteria. For actuation in gas turbine engine applications, the
shape memory alloy possesses excellent resistance to oxidation (up
to about 1150.degree. C. for the hottest applications) and--in the
case where actuation near the operating temperature is required--a
high transformation temperature. Suitable shape memory alloy
compositions may include, but are not limited to alloys having the
formula (A.sub.1-xPGM.sub.x).sub.0.5+yB.sub.0.5-y, wherein A is one
or more of Ni, Co and Fe; PGM comprises one or more platinum-group
elements, including Pt, Pd, Rh, Ru, and Ir, and B includes one or
more of Al, Cr, Hf, Zr, La, Y, Ce, Ti, Mo, W, Nb, Re, Ta, and V; x
ranges from greater than 0 to about 1 or from about 0.1 to about
0.6 atomic fraction and y ranges from about 0 to about 0.23 or from
about 0.01 to about 0.2 atomic fraction. In addition, the alloy may
further include up to about 1 at % carbon and/or boron. One
embodiment includes the formula wherein A is Ni, PGM is one or more
of Pt and Pd; B is one or more of Al, Cr, Hf and Zr. Another
embodiment includes the formula wherein A is Ni; PGM is Pd; B is Ti
and Al; x is about 0.4 and y is from about -0.1 to about 0.1. Still
another embodiment includes B comprising Ti and Al with a Ti to Al
ratio of from about 0.1 to about 10. Still another embodiment
includes B comprising up to 10 at % Cr and up to 2 at % of one or
both of Hf, Zr, and Y
[0024] Still another embodiment includes alloy systems having the
formula Ru.sub.0.5+y(Nb.sub.1-xTa.sub.x).sub.0.5-y. These alloy
systems further include phases, such as the martensite phase and
the austenite phase, suitable for shape memory properties. One
embodiment of the ruthenium containing system includes an alloy
wherein y is about -0.06 to about 0.23 atomic fraction and x is
from about 0 to about 1.
[0025] Although the shape memory alloy may be formed into an
actuator body or a portion of an actuator body, the shape memory
alloy may also be directly affixed to the high temperature
component. The specific method of affixing will depend, in part, on
the desired geometry and the compositions of the shape memory alloy
and the actuatable component. The various methods of affixing the
shape memory alloy to the base component structure may generally be
categorized as mechanical joining, deposition or metallurgical
bonding. Suitable methods of mechanical joining include, but are
not limited to, riveting, bolting, bracing or wire tying. Suitable
methods of deposition include, but are not limited to, cladding or
coating via arc spray, electro-spark deposition, laser cladding,
vacuum plasma spray, inert gas shrouded thermal spray, plasma
transfer arc, physical vapor deposition, or vacuum arc deposition.
Methods of metallurgically bonding include, but are not limited to,
brazing, co-extrusion, explosion bonding, hot-isostatic-pressing
(HIP), forge-bonding, diffusion bonding, inertia welding,
translational friction welding, fusion welding, friction-stir
welding, and the like.
[0026] Although reference has been made to affixing the shape
memory alloy onto the turbine component, it is also noted that a
turbine component comprising the shape memory alloy of the present
disclosure may be separate and/or detached from fixed or rotating
turbine components. For example, suitable components may include a
separated seal component having a structure that is free-floating
within a cavity that expands to a desired geometry upon
heating.
[0027] FIG. 1 is a view depicting a centerline cross-section of a
gas turbine engine utilizing a shape memory actuator according to
an embodiment of the present disclosure. The turbine section 100 is
a three-stage turbine, although any number of stages may be
employed, depending on the turbine design. Turbine disks 101 are
mounted on a shaft (not shown) extending through a bore in disks
101 along the centerline 103 of the engine, as shown. Turbine
blades 102 are affixed to the disks 101. Specifically, a first
stage blade 105 is attached to first stage disk 106, while second
stage blade 107 is attached to second stage disk 108 and third
stage blade 109 is attached to third stage disk 110. Vanes 111
extend from a casing 113. Hot combustion gases flow over vanes 111
and blades 102 in the hot gas flow path. The first stage blade 105,
the second stage blade 107, the third stage blade 109 and the vanes
111 extend into the hot gas flow path. The vanes 111 serve to
direct the hot gas flow while blades 102 mounted on disks 101
rotate as the hot gases impinge on them, extracting energy to
operate the engine.
[0028] Wheelspace seals 115 serve to seal the disks 101 and the
lower portions of the turbine blades 102 from the hot combustion
gases, and to maintain the hot combustion gases in the hot gas flow
path. The seals 115 form a boundary to prevent leakage of the hot
gases. Whereas seals 115 are subject to leakage during rotation,
particularly at operational temperatures, it is desirable to
minimize the amount of leakage that occurs. The actuators,
including actuator bodies comprising shape memory alloy material
according to an embodiment of the disclosure, may be utilized to
deploy at elevated temperatures, such as the operational
temperatures of the gas turbine engine, to reduce the amount of
leakage that occurs through the seals 115.
[0029] FIG. 2 shows an enlarged view of area 117 from FIG. 1,
showing a portion of the gas turbine forward of first stage blade
105 and first stage disk 106. A plurality of shape actuators 201
fabricated of shape memory alloy are affixed along the wheelspace
seal path 203, wherein combustion gas leakage may take place. The
shape actuators 201 may be affixed to the surfaces along wheelspace
seal path 203 in any suitable manner, including joining to the
metallic surface or otherwise incorporating or affixing the
actuator 201 to the surface. The shape actuator 201 is configured
to permit motion or actuation at or below the temperature of gas
turbine engine operation. In particular, the actuation may occur
when the temperature within the wheelspace seal path 203 begins to
exceed about the austenite start temperature. At the austenite
start temperature, the geometry of the shape memory alloy within
shape actuator 201 begins to change. While the process may be
irreversible, the shape actuator 201 may include two-way shape
memory characteristics, wherein cooling of the shape actuator 201
(e.g., a reduction in temperature within the wheelspace seal path
203) below about the martensite start temperature results in phase
change to the martensite phase and a return to its corresponding
low-temperature geometry. The altered geometry of the shape memory
alloy permits motion of the shape actuator 201. The motion may be
provided by affixing the actuator 201 to a rigid surface at a
single point or a plurality of points, wherein the shape actuator
201 may include a straight, bent or curved geometry when in the
austenite phase. The bending or other motion in this embodiment
provides a reduced cross-section through which leakage may occur
within the wheelspace seal path 203, thereby improving the
performance of the seal 115, particularly at operational
temperatures. Although FIG. 2 shows a plurality of actuators 201,
any number or a single actuator 201 may be utilized, wherein the
positioning of the actuators 201 may include any position that
provides the desired functionality during assembly and/or
deployment. Actuators 201 may be individually disposed or segmented
to accommodate the configuration of individual parts, such as
around the circumferential direction of vanes 111. Alternately, one
or more actuators 201 may be affixed to the surfaces of a turbine
component during or after the turbine assembly.
[0030] FIG. 3 shows an example of an actuator 201 affixed to a
surface in a manner that permits pivotal movement within seal path
203 upon exposure to temperatures above about the austenite start
temperature. The actuator 201 in this example is affixed to a
surface a turbine component at location and at a distance from the
pivot axis so as to allow rotation of the actuator about the pivot
axis during actuation.
[0031] FIG. 4 shows an example of an actuator 201 affixed along a
location on the surface a turbine component in a manner that
permits bending or arcing of at least a portion of the actuator 201
into the wheelspace seal path 203 upon exposure to temperatures
above about the austenite start temperature.
[0032] While FIGS. 1-4 have been described with respect to turbine
seals, the present disclosure is not limited to use in turbine
seals. The present disclosure may include shape actuators 201 for
use in any high temperature and/or oxidizing atmosphere. While not
so limited, the shape actuators 201 include the shape memory alloy
according to the present disclosure that may be used in, adjacent
to, or in cooperation with turbine nozzles, blades, shrouds, shroud
hangers, combustors, exhaust nozzles, disks, and other seals
exposed to high temperatures. Specifically, the shape actuators 201
may include exhaust nozzles or associated structures, wherein the
exhaust nozzle geometry may be altered or configured at operational
temperatures by use of the shape memory alloys therein to provide
control or management of the flow of exhaust gases. In another
embodiment, shape actuators 201, according to embodiments of the
present disclosure, may include exhaust chevrons to provide
take-off noise reduction and cruise aerodynamic efficiency. Further
still, shape actuators 201, according to embodiments of the present
disclosure, include cooling air diverters for controlling,
regulating and/or optimizing cooling air flow distribution within a
gas turbine engine.
EXAMPLE
[0033] Single crystal superalloy Rene N5 test coupons were coated
with a test material. The test coupons were 25 millimeters in
diameter and 3.25 mm in thickness. An Example 1 included a 50
micrometer coating of (Ni,Pt)Al having an approximate composition
according to the formula Ni-40Al-6Co-5Pt-4Cr (at %). A Comparative
Example 2 included a 275 micrometer NiTi coating having a
composition according to the formula Ni-47Ti (at %). The
Comparative Example 2 is representative of the broadly used
NiTi-family of shape memory alloys. The coupons were subjected to
repeated thermal cycles in air, wherein they were heated to a
temperature of 1150.degree. C. for a duration of 1 hour, followed
by cooling to room temperature. FIG. 5 shows Example 1 and
Comparative Example 2, prior to thermal cycling, after 1 cycle and
after 100 cycles. It is noted that Comparative Example 2 failed due
to severe oxidation after a single cycle, while Example 1 remained
intact even after 100 cycles at 1150.degree. C. FIG. 6 graphically
illustrates the relative mass gain for Example 1 and Comparative
Example 2. As is seen from this example, a high-temperature
resistant composition of shape memory alloy can withstand the harsh
oxidizing environment representative of turbine operation, while
the NiTi-based shape memory alloy known in the art for
low-temperature operation is too severely oxidized to be useful at
high temperatures.
[0034] While the invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from 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 the 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.
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