US 20050111966 A1
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.
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
3. A static structure for a gas turbine engine as claimed in
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
6. For a gas turbine engine as claimed in
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
9. For a gas turbine engine as claimed in
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.
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.
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
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.
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.
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.
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.
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.
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.
The foregoing and other features of the present invention will become more apparent from the following description and accompanying drawings.
These figures merely serve to further clarify and illustrate the present invention and are not intended to limit the scope thereof
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.
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
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
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.
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
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.
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.