U.S. patent application number 10/722868 was filed with the patent office on 2005-05-26 for construction of static structures for gas turbine engines.
Invention is credited to Metheny, Alfred Paul.
Application Number | 20050111966 10/722868 |
Document ID | / |
Family ID | 34592095 |
Filed Date | 2005-05-26 |
United States Patent
Application |
20050111966 |
Kind Code |
A1 |
Metheny, Alfred Paul |
May 26, 2005 |
Construction of static structures for gas turbine engines
Abstract
Porous or foam metal is utilized in certain static gas turbine
engine components that includes the main body of the metal and a
coating such as TBC or ceramics. Because of the porosity of the
metal the coating bonds to the interstices and hence, eliminates
peeling. The outer air seal for the turbine and the vanes of the
stator vane assembly are examples of components constructed in
accordance with this invention. Cooling is obtained by providing
inlet cooling holes into the porous material and exit cooling holes
in the coating so as to cool the component and apply a surface of
cooling air adjacent to the exterior surface of the coating.
Inventors: |
Metheny, Alfred Paul;
(Jupiter, FL) |
Correspondence
Address: |
Norman Friedland
Suite 400
11300 US Highway One
North Palm Beach
FL
33408
US
|
Family ID: |
34592095 |
Appl. No.: |
10/722868 |
Filed: |
November 26, 2003 |
Current U.S.
Class: |
415/116 |
Current CPC
Class: |
Y02T 50/6765 20180501;
F05D 2230/312 20130101; Y02T 50/676 20130101; Y02T 50/60 20130101;
F01D 5/284 20130101; F01D 5/183 20130101; F05D 2300/611 20130101;
F05D 2300/612 20130101; F05D 2230/313 20130101; F01D 5/288
20130101; F05D 2260/203 20130101; F01D 5/186 20130101; F05D 2230/90
20130101; F05D 2260/202 20130101; F01D 25/12 20130101; Y02T 50/67
20130101; F05D 2230/314 20130101 |
Class at
Publication: |
415/116 |
International
Class: |
F04D 031/00 |
Claims
It is claimed:
1. A static structure for a gas turbine engine comprising a main
body made from a porous material, a coating applied to the main
body, said coating being a thermal barrier coating or a ceramic
coating.
2. A static structure for a gas turbine engine as claimed in claim
1 including means for supplying cooling air from the gas turbine
engine into said porous material so as to cool the same.
3. A static structure for a gas turbine engine as claimed in claim
1 including means for supplying cooling air to said porous metal
for cooling the same, the spent cooling air from said porous metal
being fed to the outer surface of said coating through an aperture
formed in said coating whereby said exterior surface of said
coating is film cooled by said spent cooling air.
4. For a gas turbine engine, an outer air seal for a turbine rotor
including a main annular body surrounding the tips of the blades of
said turbine rotor, said main body comprising the substrate made
from a porous metal and a coating of a thermal barrier coating or
ceramic coating on the exterior of said substrate and adjacent to
the tips of said blades, said main body including a hook-like
member, an engine casing, said hook-like member fitted into a
groove formed in said engine casing for supporting said outer air
seal in proximity to the tips of said turbine blades.
5. For a gas turbine engine as claimed in claim 4 including means
for supplying cooling air to openings formed in said porous
material, whereby the cooling air flows through the pores of said
porous material for cooling the main body.
6. For a gas turbine engine as claimed in claim 5 wherein spent
cooling air from said porous material flows through openings formed
in said thermal barrier coating or ceramic coating to cool the
exterior surface of said thermal barrier coating or ceramic
coating.
7. For a gas turbine engine, stator vane assembly comprising a
plurality of circumferentially spaced vanes, said vanes made from a
porous metal material and having a coating adjacent to the outer
surface thereof, said coating being made from a thermal barrier
coating or ceramic, an outer platform, said vane being mounted to
said outer platform.
8. For a gas turbine engine as claimed in claim 7 including means
for supplying cooling air to openings formed in said porous
material, whereby the cooling air flows through the pores of said
porous material for cooling the main body.
9. For a gas turbine engine as claimed in claim 8 wherein spent
cooling air from said porous material flows through openings formed
in said thermal barrier coating or ceramic coating to cool the
exterior surface of said thermal barrier coating or ceramic
coating.
Description
FEDERALLY SPONSORED RESEARCH
[0001] None
TECHNICAL FIELD
[0002] This invention relates to static structures in gas turbine
engines and more particularly to these structure that are
fabricated from foam metal material and judiciously coated.
BACKGROUND OF THE INVENTION
[0003] As is well known in the power plant technology, one of the
more insidious problems associated with gas turbine engines and
particularly those powering aircraft is the structural damage such
as cracking of the components that operate in these hostile
environments. Needless to say, because of the enormous costs in
original and replacement components like vanes and seals, there is
a tremendous need in the industry to provide a suitable material
that minimizes the repair technique that will not only serve to
repair the damaged component, but also to add life to these
components and improve performance.
[0004] The turbine power plant typically consists of an air inlet,
a fan/compressor section, a diffuser, a combustor, a turbine
section and an exhaust nozzle. In military engines an afterburner
or augmentor may be located just downstream of the turbine section
and ahead of the exhaust nozzle. The air from the inlet is
pressurized by the compressor and it is then diffused and admitted
to the combustor where fuel is added and combusted to accelerate
and heat the air so that the combined combusted products serve to
power the turbines. A portion of this energy is used to develop
thrust and another portion is used to power the fan/compressors.
Inasmuch as the heat generated in the power plant is sufficiently
hot to impair the structual integrity of the engine components,
air, typically from the compressor section, is utilized to cool
certain engine components
[0005] Hence, not only is the engine subjected to extreme
temperatures and high stress levels, it is also subjected to
foreign matter that is ingested in the inlet of the engine. All of
these conditions play an extremely important role in the selection
of the material and design of the power plant. One of the concerns
with respect to this invention is the propensity of cracks that can
occur in certain static engine components and the economics of the
original parts as well as the repair and replacement of parts. In
heretofore known materials being utilized in current day engines, a
crack or crevice developed in a component tends to propagate and if
not attended to within a given time period, this part can lead to a
failure of the part and ultimately to an engine failure. Another
concern is that the coating of engine components during the normal
operation of the engine has a tendency to degrade or peel off.
Hence, the gases that pass through the engine also include
particles of sand, dust oxides of calcium, magnesium, aluminum,
silicon and mixtures. The oxides can combine to form particularly
deleterious calcium-magnesium-aluminum-silicon oxide systems. These
contaminates can be in a molten state and can infiltrate pores and
openings in engine parts that can lead to crack formation and part
failure. The severity of the problem is manifested because the
substrate is generally formed from a metallic smooth surface.
Hence, the combined fight between the thermal loads and the stress
in addition to the bond strength acerbate the problem so that the
coating tends to peel rather than remain local. This limits the
effective thickness that the TBC can be used which, in turn, sets
the cooling requirement and engine performance. The thicker coating
allows lower cooling and hence, enhances performance. It is
therefore the goal of the engine designer to provide components
that have long life, effective thickness, are economical,
maintainable and meet engine specification requirements to achieve
the ultimate in gas turbine engine efficiency.
[0006] Porous metal material, sometimes referred to as foam metal,
has been to some degree developed and is currently undergoing
development and exhibit properties that could be adapted for engine
use. Such foam metals are fabricated by mixing metal particles with
a pliable organic hollow spheres into a liquid as a suspension.
There after the solution is processed by pressing, slip casting,
extruding or injection molding the mixture and then dried. The now
dried material is fired to bond the particles such as by sintering
so as to eliminate the organic spheres. A good understanding of the
manufacturing of foam metals can be had by referring to U.S. Pat.
No. 5,937,641 granted to Graham et al on Aug. 17, 1999 and U.S.
Pat. No. 6,592,787 granted to Pickrell, et al on Jul. 15, 2003,
both of which are incorporated herein by reference.
[0007] This invention solves the problem of providing certain
engine component parts, namely the outer air seal for the turbine
and the stator vanes, by fabricating these components from a foam
metal, coating the same with a suitable thermal barrier or ceramic
coating and judiciously locating openings in the components for
cooling purposes so as to withstand the temperatures of the hostile
environment. According to this invention the problem of cracking
and coating peeling is either eliminated or significantly reduced.
When the component is injured where a blemish, crack or crevice is
formed on the surface of the part, the material is such that the
propensity for the blemish, crack or crevice to propagate is
eliminated so that the repair process is significantly
enhanced.
SUMMARY OF THE INVENTION
[0008] An object of this invention is to fabricate static power
plant components from a foam metal, coat the same with a thermal
barrier or ceramic coating and include air inlet or exit openings
to cool the parts internally. Letting the cooling air discharge
from the coating as it migrates thereto through the porous metal
serves to provide transporational cooling of the exterior surface
of the coating.
[0009] Another object of this invention is to fabricate an outer
air seal for a gas turbine engine from a foam metal, coat the same
with a thermal barrier or ceramic coating and include air inlet or
exit openings to cool the parts internally.
[0010] Another object of this invention is to fabricate the vanes
of a stator vane for a gas turbine engine from a foam metal, coat
the same with a thermal barrier or ceramic coating and include air
inlet openings to cool the parts internally.
[0011] The foregoing and other features of the present invention
will become more apparent from the following description and
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a fragmentary view partly in section and partly in
elevation of the outer air seal for the turbine blades in the
turbine section of a gas turbine engine showing the details of this
invention;
[0013] FIG. 2 is an enlarged perspective view of a section of the
segmented or ring outer air seal of FIG. 1;
[0014] FIG. 3 is a fragmentary view partly in section and partly in
elevation showing the details of this invention in the vane portion
of the stator vane for a gas turbine engine; and
[0015] FIG. 4 is a sectional view showing the details of this
invention taken along lines 4-4 of FIG. 3.
[0016] FIG. 5 is a fragmentary view of the coated porous metal to
illustrate the transpirational cooling attained by this
invention.
[0017] These figures merely serve to further clarify and illustrate
the present invention and are not intended to limit the scope
thereof
DETAILED DESCRIPTION OF THE INVENTION
[0018] While the preferred embodiment of this invention is directed
to bladed outer air seals, sometimes referred to as BOAS, and vanes
of a stator vane assembly for gas turbine engines, as one skilled
in this art will realize, other components of the gas turbine
engine may lend themselves to utilize the invention. What is deemed
important in this invention is that the substrate has minute holes
that serve as a bond or integral bond of the coating so that the
coating does not have a tendency to peel and hence, the crack or
blemish stays localized to enhance the repair of the part.
Additionally, the particular coating material and the method of
application that is utilized may vary from component to component
and for various engine applications. The coatings referred to in
this patent application are well known coatings utilized in turbine
power plant technology and any appropriate state-of-the art
coatings utilized with this invention are deemed to be within the
scope of this invention. As one skilled in this art will realize,
while the construction of the vanes of a stator vane assembly and
outer air seals are novel and not obvious, these components are
mere examples of how this invention can be applied in a gas turbine
engine and hence, for the lack of another description, they serve
as examples of this invention.
[0019] The first part of this description refers to the outer air
seal (BOAS) generally illustrated by reference numeral 10 for the
turbine of a gas turbine engine (not shown) and depicted in FIGS. 1
and 2 as comprising the outer air seal main body 12 supported to
the engine case 14 and surrounding the axial flow turbine rotor
assembly 15 consisting of blade 16 (only one of several
circumferentially spaced blades is shown). The turbine blade is
suitably mounted to the disk 18 which, in turn, is coupled to the
engine shaft (not shown) for rotary motion. Ahead of and in back of
the turbine blade 16 are the stator vane assemblies 20 and 22,
respectively and each stator vane assembly includes a plurality of
circumferentially spaced vanes 24 and 26 (only one being shown)
that serve to direct the engine working medium into adjacent
turbine blades.
[0020] These components are well known and for more details thereof
reference should be made to U.S. Pat. No. 6,393,331 granted to
Chetta et al on May 21, 2002 and U.S. Pat. No. 5,839,878 granted to
Maier on Nov. 24, 1998. Suffice it to say that this invention is
particularly concerned with static structures in the engine where
it is desirable to provide a component that is characterized as
being capable of withstanding the high temperatures and hostile
environment while affording the advantages being described herein.
In the BOAS the outer air seal main body is made from a high
temperature porous material, like a foam metal such as that
manufactured by Porvair Advanced Materials, 700 Shepherd Street,
Hendersonville, N.C. 26792 USA that could be made from Hastalloy,
Inconel, FeCRAly and the like. The material selected must be
capable of being reduced to a powder so that it can be processed
into a porous material that exhibits a low density high strength
structure. As noted from FIGS. 1 & 2 the outer air seal 10 is a
ring-like structure that includes the hook members 30 and 32 that
fit into a complementary groove 34 and 36 respectively and the
ring-like structure may be a complete 360.degree. ring, 180.degree.
rings or it may be segmented into a number of segments to form the
ring. The outer air seal main body consists of the shaped porous
member 40 and the coating 42. The coating may be any well known
thermal barrier coating (TBC) or ceramic coating that is capable of
withstanding the temperature environment of the engine. Various
coating process may be utilized as for example, plasma spray,
chemical vapor deposition, physical vapor deposition or reactive
coatings. Standard surface preparations required for each of these
processes may be utilized. For more details of these types of
coatings reference should be made to U.S. Pat. No. 5,272,014
granted to Leyendecker on December 1993, and U.S. Pat. No.
5,656,364 granted to Rickerby on August, 1997, U.S. Pat. No.
5,702,829 granted to Paidassi on December, 1997, U.S. Pat. No.
4,588,450 granted to Purohit on May 1986 And U.S. Pat. No.
6,129,988 granted to Vance et al on October, 2000 all of which are
incorporated herein by reference.
[0021] In order to assure the structural integrity of the BOAS, a
plurality of openings 68 formed an the outer face that serve to
receive cooling air and admit the air internally of the porous
metal where the air migrates through the metal to cool the
component.
[0022] Another component that lends itself to utilizing porous
metal or foam metal is the vane 70 (one of a plurality of
circumferentially spaced vanes being shown) of the stator vane
assembly 72 depicted in FIGS. 3 and 4. The vane assembly 72 may be
fabricated by a plurality of single vanes 70 attached to an upper
platform or shroud 76 and a lower platform (not shown) or may
consist of a plurality of segmented vanes mounted in the platforms
and attached to form the ring construction. These techniques are
well known in this technology and like the BOAS, this invention is
directed to the structure of the main body of the vane 70. This
member utilizes the same types of foam metal 78 and coating 80 that
is described in the embodiment depicted in FIGS. 1 and 2. For the
sake of simplicity and convenience, a description thereof is
omitted and the details are incorporated herein by reference.
Similar to the BOAS, a plurality of openings 82 formed an the outer
face that serve to receive cooling air and admit the air internally
of the porous metal where the air migrates through the metal to
cool the component assuring that the component is cooled so as to
maintain its structural integrity.
[0023] FIG. 5 is exemplary of the option of designing the coating
so that it provides transpirational cooling such that the foam
metal that is subjected to cooling air, as air from the compressor,
for example, flows through the minuscule pores of the porous metal
80 and into the apertures 90 formed in the coating. The pressure
ratio of the air across the coating is designed so that the
aperture 90 produces film cooling whereby the air discharging from
aperture 90 flows along the surface of the coating and hence
provides another cooling from the spent air used to cool the porous
metal.
[0024] What has been shown by this invention is the static
structure of a gas turbine engine capable of operating in the high
temperature hostile environment and characterized by providing a
coating that when blemished or cracked the propensity of the
blemish or crack of propagating is if not eliminated, is reduced,
because the bond of the coating adheres to the minute interstices
of the porous material. Hence, the problem of the coating peeling
from the substrate is minimized or eliminated.
[0025] Although this invention has been shown and described with
respect to detailed embodiments thereof, it will be appreciated and
understood by those skilled in the art that various changes in form
and detail thereof may be made without departing from the spirit
and scope of the claimed invention.
* * * * *