U.S. patent application number 13/412686 was filed with the patent office on 2013-09-12 for fabricated turbine airfoil.
This patent application is currently assigned to General Electric Company. The applicant listed for this patent is Christopher Michael Prue. Invention is credited to Christopher Michael Prue.
Application Number | 20130236318 13/412686 |
Document ID | / |
Family ID | 47826985 |
Filed Date | 2013-09-12 |
United States Patent
Application |
20130236318 |
Kind Code |
A1 |
Prue; Christopher Michael |
September 12, 2013 |
FABRICATED TURBINE AIRFOIL
Abstract
The invention provides an apparatus and method for combining
materials having different thermal and mechanical properties into
an article, such as a gas turbine bucket, which includes a first
section, a second section, and a third section; wherein the first
section provides structural support for the remaining sections, the
second section is integrally joined with the first section, and the
third section connects the first and second sections.
Inventors: |
Prue; Christopher Michael;
(Simpsonville, SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Prue; Christopher Michael |
Simpsonville |
SC |
US |
|
|
Assignee: |
General Electric Company
|
Family ID: |
47826985 |
Appl. No.: |
13/412686 |
Filed: |
March 6, 2012 |
Current U.S.
Class: |
416/223A |
Current CPC
Class: |
F01D 5/20 20130101; F01D
5/147 20130101; F01D 5/005 20130101 |
Class at
Publication: |
416/223.A |
International
Class: |
F01D 5/14 20060101
F01D005/14 |
Claims
1. A fabricated turbine airfoil comprising a first section, a
second section, and a third section; wherein the first section
provides structural support for the remaining sections, the second
section is integrally joined with the first section, and the third
section connects the first and second sections.
2. The airfoil of claim 1, wherein the first section comprises an
aerodynamically shaped load bearing member, a first end, and a
second end.
3. The airfoil of claim 2, wherein the first end is integral with
or attached to a rotor.
4. The airfoil of claim 2, wherein the second end is exposed to
elevated temperatures, high velocity gases, or an otherwise
degrading environment.
5. The airfoil of claim 4, wherein the second section protects the
second end from the degrading environment.
6. The airfoil of claim 1, wherein the second section is comprised
of a different material than the first and third sections.
7. The airfoil of claim 1, wherein the third section comprises a
sleeve.
8. The airfoil of claim 1, wherein the second section is bonded to
the third section.
9. The airfoil of claim 8, wherein the bond between the second
section and the third section is formed using a braze alloy.
10. The airfoil of claim 2, wherein the third section is attached
to the second end of the first section.
11. A fabricated turbine bucket comprising a first section, a
second section, and a third section; wherein the first section
provides structural support for the remaining sections and
comprises a load bearing member, a first end, and a second end
exposed to elevated temperatures, high velocity gases, or an
otherwise degrading environment; the second section protects the
second end from the degrading environment and is integrally joined
with the first section, and the third section connects the first
and second sections.
12. The bucket of claim 11, wherein the first section comprises an
airfoil.
13. The bucket of claim 11, wherein the first end is integral with
or attached to a rotor.
14. The bucket of claim 11, wherein the second section is comprised
of a different material than the first and third sections.
15. The bucket of claim 11, wherein the third section comprises a
sleeve.
16. The bucket of claim 11, wherein the second section is bonded to
the third section.
17. The bucket of claim 16, wherein the bond between the second
section and the third section is formed using a braze alloy.
18. The bucket of claim 11, wherein the third section is attached
to the second end of the first section using any suitable method
resulting in a joint having high mechanical integrity.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to a turbine airfoil
formed as a fabricated article; and, more particularly, to an
apparatus and method for providing a fabricated gas turbine bucket;
wherein the radially outermost portion is protected from exposure
to elevated temperatures, high velocity gases, or an otherwise
degrading environment.
[0002] In a gas turbine, pressurized air from a compressor is mixed
with fuel and ignited in a combustor to generate hot pressurized
gases. The hot pressurized gases flow from the combustor to one or
more fixed and rotating turbine stages. Each rotating turbine stage
includes a plurality of airfoils, or buckets, which are radially
disposed about a rotating element, such as a disk. A stationary
element, such as a shroud, is radially disposed about the rotating
airfoils, thereby forming an annular flowpath. Energy is imparted
from the hot pressurized gases to the rotating airfoils, causing
rotation of the rotating element, thereby converting the thermal
and kinetic energy from the hot pressurized gases to mechanical
torque. Some of the mechanical torque is typically used to drive
the compressor, and the remaining torque is typically used to drive
a generator or other rotating machine.
[0003] Each gas turbine bucket generally includes an airfoil
extending radially outwardly from a shank that is connected with
and imparts mechanical energy to the rotating element. The airfoil
is typically hollow or contains a plurality of internal passages
through which a pressurized fluid, such as compressed air, is
caused to flow for the purpose of cooling the airfoil material.
Additionally, a tip may be provided to protect and impart
structural integrity to the radially outermost portion of the
airfoil. The tip must be capable of withstanding highly degrading
environmental conditions, including elevated temperatures and high
velocity gases; as well as have sufficient mechanical strength and
stiffness to maintain the aerodynamic shape of the airfoil, contain
the pressurized internal cooling fluid, and withstand high speed
rubbing in the event that the tip contacts the stationary
shroud.
[0004] It is often advantageous to form the tip from a different
material than the remainder of the airfoil. This combination may
provide multiple benefits; including tailoring the thermal and
mechanical properties of the tip to satisfy the particular
requirements stated above, reducing the overall weight of the
bucket, and facilitating repair of the bucket. However, the thermal
and mechanical loads acting on the airfoil may cause the material
combination to be substantially weaker and less durable than a
monolithic airfoil. This problem is particularly acute when
materials having different thermal and mechanical properties; such
as coefficient of thermal expansion, thermal conductivity, or
modulus of elasticity; are combined.
BRIEF DESCRIPTION OF THE INVENTION
[0005] The present invention provides an apparatus and method for
combining materials having different thermal and mechanical
properties into an article, such as a gas turbine bucket. The
invention also provides means for protecting the radially outermost
portion of a gas turbine bucket from exposure to elevated
temperatures, high velocity gases, or an otherwise degrading
environment. Aspects and advantages of the invention will be set
forth in part in the following description, or may be obvious from
the description, or may be learned through practice of the
invention.
[0006] In one embodiment, a fabricated turbine airfoil includes a
first section, a second section, and a third section; wherein the
first section provides structural support for the remaining
sections, the second section is integrally joined with the first
section, and the third section connects the first and second
sections.
[0007] In another embodiment, a method of manufacturing a
fabricated turbine airfoil includes the steps of forming a first
section including a load bearing member, a first end, and a second
end; forming a second section; forming a third section; attaching
the third section to the second end of the first section; and
attaching the second section to the third section in such a manner
that the second section is integrally joined with the first section
and the first section provides structural support for the remaining
sections.
[0008] Other objects and advantages of the present invention will
be better appreciated from the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Non-limiting and non-exhaustive embodiments are described
with reference to the following figures, wherein like reference
numerals refer to like parts throughout the various views unless
otherwise specified.
[0010] FIG. 1 is a perspective view of an embodiment of a gas
turbine bucket formed as a fabricated article in accordance with
aspects of the present invention.
[0011] FIG. 2 is an enlarged perspective view of the tip region of
the gas turbine bucket shown in FIG. 1 viewed
circumferentially.
[0012] FIG. 3 is a cross-sectional view of the tip region of the
gas turbine bucket shown in FIGS. 1 and 2 viewed along line
3-3.
DETAILED DESCRIPTION OF THE INVENTION
[0013] Referring now to the drawings, FIG. 1 illustrates an
exemplary embodiment of a gas turbine bucket 10 formed as a
fabricated article in accordance with aspects of the present
invention. The bucket 10 may include a dovetail 12 that attaches to
a rotor disk (not shown). A shank 14 extends radially outwardly
from the dovetail 12 and terminates in a platform 16 that projects
radially outwardly from and surrounds the shank 14.
[0014] A first section in the form of an airfoil 18 extends
radially outwardly from the platform 16. The airfoil 18 has a root
20 at the junction with the platform 16 and a tip 22 at its
radially outer end. The airfoil 18 has a concave pressure sidewall
24 and a convex suction sidewall 26 joined together at a leading
edge 28 and a trailing edge 30. The airfoil 18 may take any
configuration suitable for extracting energy from the hot gas
stream and causing rotation of the rotor. This results in a
substantial mechanical load on the airfoil caused by the difference
in gas pressure between the pressure sidewall 24 and the suction
sidewall 26. The airfoil 18 may be hollow or contain a plurality of
internal passages through which a pressurized fluid, such as
compressed air, is caused to flow for the purpose of cooling the
airfoil material. The shank 14 and platform 16 may be similarly
cooled. The airfoil 18, shank 14, and platform 16 are typically
formed from a cast high strength nickel-based superalloy, but may
be formed using any suitable process and from any suitable material
for performing the functions described herein.
[0015] FIG. 2 illustrates the tip 22 in greater detail. A second
section 100 is integrally joined to and closes off the tip 22 in a
manner such that the aerodynamic and structural continuity of the
airfoil pressure sidewall 24, suction sidewall 26, leading edge 28,
and trailing edge 30 is maintained. The second section 100 may take
any configuration suitable for maintaining the aerodynamic shape
and efficiency of the bucket 10, and may be formed using any
suitable process and from any suitable material for imparting
structural integrity to and providing environmental protection for
the tip 22. It will be appreciated that the second section 100 may
extend radially inwardly to any suitable location on the radial
span of the airfoil 18, so long as the airfoil 18 structurally
supports the second section 100 as the bucket 10 rotates or when it
is stationary.
[0016] The second section 100 may be formed from a different
material than the airfoil 18; such as a refractory metal or
metallic composite, intermetallic compound, ceramic, or ceramic
composite. In an exemplary embodiment, the second section 100 is
formed from a ceramic material by first forming a near net "green"
shape using an isostatic pressing process, followed by an
intermediate firing step to strengthen the green shape, followed by
a machining step to achieve the desired shape, followed by a firing
step to achieve the final dimensions and properties of the second
section 100. It will be appreciated that these process steps are
not exhaustive, and that any suitable process and sequence of
process steps may be used, depending upon the material forming the
second section 100; and the final dimensional tolerance, surface
finish, and mechanical properties desired.
[0017] FIG. 3 illustrates a cross-section of the tip 22 viewed
along line 3-3. The second section 100 includes a neck 120 forming
a radially inward facing surface 140. A third section in the form
of a sleeve 160 is disposed between the radially inward facing
surface 140 and a radially outward facing surface 180 of the
airfoil 18 in such a manner that the sleeve 160 nests within the
airfoil pressure sidewall 24 and suction sidewall 26 and the
majority of centrifugal load is taken in the shear direction. It
will be appreciated that the radially inward facing surface 140 and
the radially outward facing surface 180 may be disposed in any
suitable manner for providing mechanical integrity to the assembly.
The sleeve 160 may be either continuous or discontinuous, and may
be formed using any suitable process and from any suitable material
for providing mechanical integrity to the assembly and resistance
to thermal distortion. In an exemplary embodiment, the sleeve 160
is formed from a nickel-based superalloy using a stamping or
extrusion process followed by machining to the final shape,
dimensions, and surface finish desired.
[0018] The sleeve 160 may be bonded to the radially inward facing
surface 140 using a brazing process. In an exemplary embodiment, a
braze alloy such as Palniro.TM.-1 (50% gold, 25% nickel, 25%
palladium) may be used with a suitable heat treatment to achieve
high mechanical integrity of the resulting joint. It will be
appreciated that mechanical features may be added to the sleeve 160
and the radially inward facing surface 140 in order to improve the
mechanical strength of the bond, particularly in the shear
direction.
[0019] The sleeve 160 may be attached to the radially outward
facing surface 180 using any suitable method; such as brazing,
welding, mechanical attachment, or a combination thereof; in order
to achieve high mechanical integrity of the resulting joint,
particularly in the shear direction, as well as provide means for
removal of the sleeve 160 and second section 100 assembly during
repair and refurbishment of the bucket 10.
[0020] Summarizing, the present invention contemplates a fabricated
airfoil; wherein the radially outermost portion is protected from
exposure to elevated temperatures, high velocity gases, or an
otherwise degrading environment. Exemplary embodiments of the
fabricated airfoil are described in detail above.
[0021] Although the apparatus and methods described herein are
described in the context of creating a turbine airfoil, it is
understood that the apparatus and methods are not limited to
turbomachinery applications. Furthermore, although the foregoing
description contains many specifics, these should not be construed
as limiting the scope of the present invention, but merely as
providing illustrations of some of the presently preferred
embodiments. Similarly, other embodiments of the invention may be
devised which do not depart from the spirit or scope of the present
invention. Features from different embodiments may be employed in
combination. The scope of the invention is, therefore, indicated
and limited only by the appended claims and their legal
equivalents, rather than by the foregoing description. All
additions, deletions and modifications to the invention as
disclosed herein which fall within the meaning and scope of the
claims are to be embraced thereby.
[0022] As used herein, an element or step recited in the singular
and proceeded with the word "a" or "an" should be understood as not
excluding plural elements or steps, unless such exclusion is
explicitly recited. Furthermore, references to "one embodiment" of
the present invention are not intended to be interpreted as
excluding the existence of additional embodiments that also
incorporate the recited features.
[0023] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal languages of the claims.
* * * * *