U.S. patent application number 12/206844 was filed with the patent office on 2010-03-11 for steam turbine part including ceramic matrix composite (cmc).
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Yogesh Kesrinath Potdar, Shu Ching Quek, David Ernest Welch.
Application Number | 20100061847 12/206844 |
Document ID | / |
Family ID | 41349753 |
Filed Date | 2010-03-11 |
United States Patent
Application |
20100061847 |
Kind Code |
A1 |
Welch; David Ernest ; et
al. |
March 11, 2010 |
STEAM TURBINE PART INCLUDING CERAMIC MATRIX COMPOSITE (CMC)
Abstract
A steam turbine part includes a ceramic matrix composite (CMC).
The part may be made wholly or partially of CMC. The CMC eliminates
the possibility of oxidation and thus increases steam turbine
availability and reliability
Inventors: |
Welch; David Ernest;
(Amsterdam, NY) ; Potdar; Yogesh Kesrinath;
(Niskayuna, NY) ; Quek; Shu Ching; (Clifton Park,
NY) |
Correspondence
Address: |
Hoffman Warnick LLC
75 State Street, Floor 14
Albany
NY
12207
US
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
41349753 |
Appl. No.: |
12/206844 |
Filed: |
September 9, 2008 |
Current U.S.
Class: |
415/200 |
Current CPC
Class: |
F05D 2300/224 20130101;
F05D 2300/2112 20130101; F01D 5/282 20130101; F05D 2300/226
20130101; F01D 9/02 20130101; F05D 2300/21 20130101; F01D 5/284
20130101; F05D 2300/614 20130101 |
Class at
Publication: |
415/200 |
International
Class: |
F04D 29/40 20060101
F04D029/40; F01D 9/00 20060101 F01D009/00 |
Claims
1. A steam turbine part comprising: a ceramic matrix composite.
2. The steam turbine part of claim 1, wherein the CMC is a layer
over a metal core.
3. The steam turbine part of claim 2, further comprising a thermal
matching interface between the CMC and the metal core.
4. The steam turbine part of claim 1, wherein the CMC includes an
oxide based CMC.
5. The steam turbine part of claim 4, wherein the oxide based CMC
includes aluminum oxide (Al.sub.2O.sub.3).
6. The steam turbine part of claim 5, wherein the CMC further
includes silicon carbon (SiC).
7. The steam turbine stationary part of claim 1, wherein the CMC
includes an oxide based matrix and a ceramic based fiber.
8. The steam turbine stationary part of claim 7, wherein the oxide
based matrix includes aluminum oxide (Al.sub.2O.sub.3), titanium
boride (TiB) and silicon carbon (SiC).
9. The steam turbine part of claim 7, wherein the oxide based
matrix includes aluminum oxide (Al.sub.2O.sub.3), titanium
di-boride (TiB.sub.2), platinum carbon (PtC) and silicon carbon
(SiC).
10. The steam turbine part of claim 1, wherein the CMC includes: a
matrix selected from the group consisting of: zirconium carbide
(ZrC), hafnium carbon (HfC), titanium carbon (TiC), tantalum carbon
(TaC), niobium carbon (NbC), zirconium silicon carbon (Zr--Si--C),
hafnium silicon carbon (Hf--Si--C) and titanium silicon carbon
(Ti--Si--C); and a fiber selected from the group consisting of:
silicon carbon (SiC), carbon (C) and alpha-Al.sub.2O.sub.3 with
yttrium oxide (Y.sub.2O.sub.3) and zirconium oxide (ZrO.sub.2).
11. The steam turbine part of claim 1, wherein an exterior surface
of the part includes a textured surface.
12. The steam turbine part of claim 1, wherein the part includes a
stationary part.
13. The steam turbine part of claim 12, wherein the stationary part
is selected from a group consisting of: a valve stem, a nozzle, and
a bushing.
14. A steam turbine comprising: a part including a ceramic matrix
composite.
15. The steam turbine of claim 14, wherein the CMC is a layer over
a metal core.
16. The steam turbine of claim 15, further comprising a thermal
matching interface between the CMC and the metal core.
17. The steam turbine of claim 14, wherein the CMC includes an
oxide based CMC.
18. The steam turbine of claim 17, wherein the oxide based CMC
includes aluminum oxide (Al.sub.2O.sub.3).
19. The steam turbine of claim 18, wherein the CMC further includes
silicon carbon (SiC).
20. The steam turbine of claim 14, wherein the CMC includes: a
matrix selected from the group consisting of: zirconium carbide
(ZrC), hafnium carbon (HfC), titanium carbon (TiC), tantalum carbon
(TaC), niobium carbon (NbC), zirconium silicon carbon (Zr--Si--C),
hafnium silicon carbon (Hf--Si--C) and titanium silicon carbon
(Ti--Si--C); and a fiber selected from the group consisting of:
silicon carbon (SiC), carbon (C) and alpha-Al.sub.2O.sub.3 with
yttrium oxide (Y.sub.2O.sub.3) and zirconium oxide (ZrO.sub.2).
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates generally to steam turbines. More
particularly, the invention relates to a steam turbine part
including ceramic matrix composite (CMC).
[0002] In steam turbines, valves open and close openings between
sections of the turbine and are exposed to steam under pressure.
One of the design criteria for any steam turbine is reliability,
followed by availability and operability. Valve stems, which are
typically made of a Nickel alloy, are subjected full steam pressure
and temperatures. These pressure and temperatures can reach up to
24.8 mega Pascals (MPa) (3600 pounds per square inch (psi)) and
621.degree. C. (1150.degree. F.) in current designs. Next
generation steam turbines, however, are expected to reach up to
29.6 MPa (4300 psi) and 760.degree. C. (1400.degree. F.). Under
these latter conditions, Nickel alloy valve stems will oxidize and
build up oxide. The valve stem is expected to have up-down motion
in a bushing made of similar material. Thus, both valve stem and
bushing may develop oxide. To maintain reliability, it is necessary
to sustain sufficient clearance at the design and manufacturing
stage, so as to allow the stem to work smoothly until major
overhaul and/or replacement of the stem (typically 5-10 years) can
be performed. One approach to solve this solution is providing
additional clearance for the oxide. Unfortunately, providing
excessive clearance results in steam leakage which impairs
performance. In addition, at high steam temperatures, any
reasonable engineering clearance (e.g. 10 millimeter radial) will
disappear due to oxide build-up on Nickel based super-alloys in
probably 2-4 years, thus potentially resulting in valve stem
binding, making the valve non-functional. If a stem binds in its
normal, valve open condition, such an event may result in an
inability to shut off steam flow and over-speeding of the
turbine.
BRIEF DESCRIPTION OF THE INVENTION
[0003] A steam turbine part includes a ceramic matrix composite
(CMC). The part may be made wholly or partially of CMC. The CMC
eliminates the possibility of oxidation under which a layer of
partially or fully oxide based ceramic/fiber combination is
applied, and thus increases steam turbine availability and
reliability.
[0004] A first aspect of the disclosure provides a steam turbine
part for a steam turbine, the stationary part comprising: a ceramic
matrix composite.
[0005] A second aspect of the disclosure provides a steam turbine
comprising: a part including a ceramic matrix composite.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a perspective partial cut-away illustration of a
steam turbine.
[0007] FIG. 2 is a cross-sectional view of a steam turbine part in
the form of a valve stem made completely of ceramic matrix
composite (CMC).
[0008] FIG. 3 is a cross-sectional view of a steam turbine part in
the form of a valve stem made partially of CMC.
[0009] FIG. 4 is a cross-sectional view of a steam turbine part in
the form of a valve stem having only surfaces exposed to steam made
of a CMC.
[0010] FIG. 5 is a cross-sectional view of a steam turbine part in
the form of a valve stem made of a CMC having a textured exterior
surface.
DETAILED DESCRIPTION OF THE INVENTION
[0011] At least one embodiment of the present invention is
described below in reference to its application in connection with
and operation of a steam turbine. However, it should be apparent to
those skilled in the art and guided by the teachings herein that
the present invention is likewise applicable to any suitable
turbine and/or engine. Embodiments of the present invention provide
a steam turbine part where the stationary part includes a ceramic
matrix composite (CMC).
[0012] Referring to the drawings, FIG. 1 shows a perspective
partial cut-away illustration of a steam turbine 10. Steam turbine
10 includes a rotor 12 that includes a rotating shaft 14 and a
plurality of axially spaced rotor wheels 18. A plurality of
rotating blades 20 are mechanically coupled to each rotor wheel 18.
More specifically, blades 20 are arranged in rows that extend
circumferentially around each rotor wheel 18. A plurality of
stationary vanes 22 extends circumferentially around shaft 14, and
the vanes are axially positioned between adjacent rows of blades
20. Stationary vanes 22 cooperate with blades 20 to form a stage
and to define a portion of a steam flow path through turbine
10.
[0013] In operation, steam 24 enters an inlet 26 of turbine 10 and
is channeled through stationary vanes 22. Vanes 22 direct steam 24
downstream against blades 20. Steam 24 passes through the remaining
stages imparting a force on blades 20 causing shaft 14 to rotate.
At least one end of turbine 10 may extend axially away from rotor
12 and may be attached to a load or machinery (not shown) such as,
but not limited to, a generator, and/or another turbine.
[0014] In one embodiment of the present invention as shown in FIG.
1, turbine 10 comprises five stages. The five stages are referred
to as L0, L1, L2, L3 and L4. Stage L4 is the first stage and is the
smallest (in a radial direction) of the five stages. Stage L3 is
the second stage and is the next stage in an axial direction. Stage
L2 is the third stage and is shown in the middle of the five
stages. Stage L1 is the fourth and next-to-last stage. Stage L0 is
the last stage and is the largest (in a radial direction). It is to
be understood that five stages are shown as one example only, and
each turbine may have more or less than five stages. Also, as will
be described herein, the teachings of the invention do not require
a multiple stage turbine.
[0015] As understood, steam turbine 10 includes a number of parts.
For purposes of description, the invention may be described
relative to a stationary valve stem 102, as shown in FIGS. 2-4.
Other stationary parts may include, for example, a stationary valve
bushing 104 (FIGS. 2-3), a nozzle, casings, etc. It is also
understood that the teachings of the invention may also be applied
to moving parts such as a valve head or rotor blade. Part 100
includes a ceramic matrix composite (CMC). CMC may include any
ceramic material, perhaps including reinforcing fiber or fabric
weave, capable of resisting oxidation. In one embodiment, CMC
includes an oxide based matrix, which acts to eliminate oxidation.
For example, CMC 110 may include an aluminum oxide
(Al.sub.2O.sub.3) matrix. In an alternative embodiment, CMC 110 may
also include silicon carbon (SiC) fibers to increase hardness. In
another embodiment, CMC 110 includes an oxide based matrix and a
ceramic based fiber. For example, the oxide based matrix may
include (Al.sub.2O.sub.3), titanium boride (TiB) and silicon carbon
(SiC). In another example, the oxide based matrix may include
Al.sub.2O.sub.3, titanium di-boride (TiB.sub.2), platinum carbon
(PtC) or silicon carbon (SiC). The ceramic based fiber may include
any of the above-listed oxide-based matrices or a ceramic based
material such as silicon carbon (SiC). Other matrices may include,
for example, zirconium carbide (ZrC), hafnium carbon (HfC),
titanium carbon (TiC), tantalum carbon (TaC), and niobium carbon
(NbC) and mixed carbides such as zirconium silicon carbon
(Zr--Si--C), hafnium silicon carbon (Hf--Si--C) or titanium silicon
carbon (Ti--Si--C). Other fibers may include, for example, silicon
carbon (SiC), carbon (C), alpha-Al.sub.2O.sub.3 with yttrium oxide
(Y.sub.2O.sub.3) and zirconium oxide (ZrO.sub.2) additives, or
variations thereof. In any event, CMC 110 should act to increase
the ductility or energy absorption in the material system for part
100 and the capability to resist steam corrosion and wearing which
in certain cases may include layers on the CMC 110 or fibers.
[0016] In one embodiment, shown in FIG. 2, part 100 may be made
entirely of CMC. In an alternative embodiment, shown in FIG. 3,
part 100 may be made partially of CMC. In the example shown, part
100 includes a CMC layer 112 over a metal core 114, e.g., of steel.
In this case, a thermal matching interface 116 may be necessary
between CMC layer 112 and metal core 114 to aid in matching the
different thermal expansion rates. Thermal matching interface 116
may include, for example, a compliant layer between CMC layer 112
and metal core 114. Alternatively, as shown in FIG. 4, only
surfaces 118 of a part 100 that are exposed to steam may include
CMC 110. As understood, a variety of configurations may be employed
within the scope of the invention.
[0017] Part 100 may be formed using any now known or later
developed technique, e.g., creating a pre-preg of reinforcing
material as a freestanding part or mounted to a metal core 114
(FIG. 3), repeatedly infusing the prepreg with a ceramic and curing
the ceramic.
[0018] Referring to FIG. 5, in one alternative embodiment, an
exterior surface 120 of part 100 may include a textured surface
120. Textured surface 120 may be formed, for example, by providing
a woven textile fabric as an outer portion of a pre-preg such that
the fabric creates the textured surface 120. The increased surface
area for the steam path created by textured surface 120 may
increase efficiency by reducing leakage.
[0019] Although embodiments of the invention have been described
relative to a valve stem for a steam turbine, the teachings should
not be so limited. In particular, the invention can be applied to
practically any part of a steam turbine for which oxidation is a
limiting factor. For example, the teachings of the invention may be
applied to nozzles, casings, etc.
[0020] The above-described invention increases steam turbine
availability for next generation steam turbines through reduction
of oxide growth rates.
[0021] The terms "first," "second," and the like, herein do not
denote any order, quantity, or importance, but rather are used to
distinguish one element from another, and the terms "a" and "an"
herein do not denote a limitation of quantity, but rather denote
the presence of at least one of the referenced item. The modifier
"about" used in connection with a quantity is inclusive of the
stated value and has the meaning dictated by the context, (e.g.,
includes the degree of error associated with measurement of the
particular quantity). The suffix "(s)" as used herein is intended
to include both the singular and the plural of the term that it
modifies, thereby including one or more of that term (e.g., the
metal(s) includes one or more metals). Ranges disclosed herein are
inclusive and independently combinable (e.g., ranges of "up to
about 25 wt %, or, more specifically, about 5 wt % to about 20 wt
%", is inclusive of the endpoints and all intermediate values of
the ranges of "about 5 wt % to about 25 wt %," etc).
[0022] 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.
* * * * *