Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal for other than internal combustion engine – or...
Reexamination Certificate
2002-01-11
2004-03-09
Pickard, Alison K. (Department: 3676)
Seal for a joint or juncture
Seal between fixed parts or static contact against...
Contact seal for other than internal combustion engine, or...
C277S632000, C277S644000, C277S646000, C277S650000, C277S930000, C060S770000, C239S265110, C239S265430, C244S131000
Reexamination Certificate
active
06702300
ABSTRACT:
TECHNICAL FIELD
This invention relates to seals that accommodate relatively large structural movements. Specifically this invention relates to a high temperature sealing system between hot structures that are required to move relative to one another in a thrust-gas-directing environment or other severe service fluid flow environment.
BACKGROUND ART
Advanced aerospace engines and vehicles as well as other applications require sealing systems capable of blocking high temperature fluid flow. Relative movements between components caused by aerodynamic and thermal loads may cause gaps to open. If left unsealed these gaps may allow hot gas and/or unburned fuel to infiltrate into the interior of the vehicle and may cause damage to or loss of the vehicle. Relative thermal growths between components due to temperature gradients and differences in coefficients of thermal expansion between materials can also produce displacements between adjoining elements with changes in temperature. Relative movements may be both in-plane and out-of-plane with respect to adjacent structures. In large components, aerodynamic and thermal loads can cause displacements of up to several inches between adjoining elements. Such conditions require seals that can withstand and block the infiltration of high temperature gases while accommodating large displacements between adjacent structures. An additional requirement in some applications is the ability to seal contoured surfaces including corners. In addition, in some applications it is desirable for such seals to allow for rapid installation and removal of adjoining structures with minimal adjustment or preparation of the sealing structures.
In advanced gas turbine applications temperatures may range up to 2000° F. In such applications braided rope seals comprised of ceramics and superalloys may be used. Thermal barriers comprised of braided carbon fibers are capable of blocking extremely hot (approximately 5500° F.) combustion gases that are produced by solid rocket motors. Such sealing barriers are further capable of dropping the temperature across their transverse dimension by as much as 2500° F. to 2800° F. However, these seal and barrier designs are not capable of accommodating movements of several inches between adjoining elements as may occur in thrust-directing environments in some advanced aerospace engines.
Thus there exists a need for a high temperature sealing system capable of sealing an interface between two relatively movable hot structures. There further exists a need for such a sealing system that will minimize invasive parasitic flow between adjoining elements which may move relative to one another within or out-of-plane by relatively large displacements.
DISCLOSURE OF INVENTION
It is an object of an exemplary form of the present invention to provide a high temperature sealing system.
It is a further object of an exemplary form of the present invention to provide a high temperature sealing system that is capable of sealing the interface between two hot structures.
It is a further object of an exemplary form of the present invention to provide a high temperature sealing system that is capable of minimizing parasitic flow between adjoining structures which move relative to one another in-plane and out-of-plane.
It is a further object of an exemplary form of the present invention to provide a high temperature sealing system that is capable of preventing parasitic flow between adjoining structures which move relative to one another in-plane or out-of-plane by several inches.
It is a further object of an exemplary form of the present invention to provide a high temperature sealing system that seals between adjacent flow-directing structures and which contributes to directing flow in a desired direction.
Further objects of the present invention will be made apparent in the following Best Modes for Carrying Out Invention and the appended claims.
The foregoing objects are accomplished in one exemplary embodiment of the invention by a sealing system for a thrust-directing system in an aerospace vehicle. The sealing system w includes a channel. The channel spans a gap that extends between the edges of two adjacent hot structures that operate to direct hot thrust gas used to propel the vehicle. The channel and adjacent structures are configured such that transversely extending edge walls of the thrust directing structures extend within the channel in both the non-displaced and displaced positions of the adjacent structures. The channel is bounded by side walls and a bottom wall. The channel side walls overlap the edge walls of the adjoining structures. The edge walls of the adjacent structures and the side walls and bottom wall of the channel are sized to enable several inches of displacement of the adjoining structures both in-plane and out-of-plane. Baffles or dams of appropriate height may be placed in the channel where necessary to prevent adverse pressure gradients in the channel from driving flow in the channel in a direction opposite to the thrust direction.
The exemplary embodiment of the present invention further includes flexible sealing elements located along the outboard sides of the side walls bounding the channel. These sealing elements are implemented as pressure seals to prevent leakage between the channel and the adjacent hot structures. In the exemplary embodiment the sealing elements are axially segmented to allow them to conform to the contour of the adjacent structures and provide a generally fluid tight seal.
In some exemplary embodiments, the limited flow into the narrow passage between the edge walls of the thrust directing structures may be sufficiently low so that there is no need for a separate mechanism for cooling of the hot gases that flow into the channel. For higher temperature environments, the sealing system can be cooled using internal cooling passages or conduits that extend in the structures that form the channel. For example the passages may be comprised of one or more conduits running through the base of the channel. Coolant such as turbomachinery generated exhaust gas or hydrogen gas can be directed through the conduits to cool and protect the sealing structures from damage due to the heat of the thruster flow gases. In other exemplary embodiments, the channel may include coolant apertures which are operative to direct coolant to flow from the coolant conduits into the channel cavity. Coolant gas that has passed through the apertures mixes with the relatively higher temperature gases from the thruster flow. In this manner, the coolant gas is operative to cool the hot gases passing through the channel. This exemplary embodiment may also provide a convenient method of disposing of turbomachinery generated exhaust gas.
In some exemplary embodiments the channel may be comprised of monolithic or composite ceramic, carbon-carbon composites, carbon/silicon carbide, superalloy metals, oxidedispersion strengthened metals, gamma titanium aluminide, or other high temperature materials. The channel may further include coatings that provide thermal and environmental resistance for the channel materials against oxidation, hydrogen reaction, and other reactions. Such coatings in exemplary embodiments may include alumina, zirconia, yttria-stabilized zirconia, hafnium carbide, hafnium diboride, silica, silicon nitride, and silicon carbide. In further alternative embodiments heat resistant space shuttle tiles may be applied to the channel and/or to the adjacent gas flow directing structures to protect them from heat and abrasion.
The flexible sealing elements in exemplary embodiments of the present invention may be spring loaded to biasingly maintain sealing engagement with the bounding wall of the adjacent structures. Alternatively or in addition, the sealing elements may be pneumatically loaded by directing high-pressure gas into a cavity adjacent to the sealing elements. In alternative embodiments sealing elements such as ceramic wafers, braided rope seals, plunger seals, or inflatable seals could be used in the sealing system
Dunlap, Jr. Patrick H.
Steinetz Bruce M.
Pickard Alison K.
Stone Kent N.
The United States of America as represented by the Administrator
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