Patent Description:
As gas turbine engines are becoming more efficient, they are operating at higher temperatures. This requires the various components of the gas turbine engine to be able to operate at higher temperatures. In particular gas turbine engine fluid and air system seal requirements are surpassing the capability of perfluoroelastomers compounds at these elevated temperatures. Some seals, such as graphite or ceramic seals, can withstand high temperatures, but are susceptible to fluid leaks being less conformable than the elastomeric materials. Other elastomeric seals may perform better at reducing fluid leaks, but can soften, degrade or yield decomposition products adverse to adjacent components when exposed to elevated temperatures, such as temperatures from <NUM> to <NUM> degrees Fahrenheit (from <NUM> to <NUM> degrees Celsius). Other seals, such as elastomeric seals, specifically fluoroelastomers and perfluoroelastomers, run the risk of releasing fluorinated compounds which may not be suitable for use with titanium at temperatures around <NUM> degrees Fahrenheit (around <NUM> degrees Celsius) or higher. Therefore, there is a need for a seal that can withstand high temperatures while still preventing fluid leaks.

A prior art method and gas turbine engine assembly having the features of the preamble to claims <NUM> and <NUM> is disclosed in <CIT>. Other prior art disclosures that relate to seals in gas turbine engine components are disclosed in <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

In accordance with the present invention there is disclosed a method in accordance with claim <NUM>.

In an embodiment of the above, the first component is compressed towards the second component to a predetermined force after at least one fiber reinforced polyimide resin layer has cured.

In a further embodiment of any of the above, at least one fiber reinforced polyimide resin layer is heated to between <NUM> degrees Fahrenheit and less than <NUM> degrees Fahrenheit (between <NUM> degrees Celsius and less than <NUM> degrees Celsius).

In a further embodiment of any of the above, the first component and the second component transport one of a fuel, lubricating oil, or hydraulic fluid.

In a further embodiment of any of the above, at least one fiber reinforced polyimide resin layer includes fibers forming at least one of a fabric or a braid.

In a further embodiment of any of the above, the first component and the second component contribute to communicating at least one of bleed air, fuel, or lubricant in a gas turbine engine.

In a further embodiment of any of the above, the first component is disassembled from the second component during service by separating the first component from the second component after the at least one fiber reinforced polyimide resin layer has cured while maintaining the first component and the second component in a reusable condition.

In a further embodiment of any of the above, at least one second fiber reinforced polyimide resin layer is located against the first sealing surface of the first component and against the second sealing surface of the second component. At least one second fiber reinforced polyimide resin layer is compressed against the first sealing surface and the second sealing surface prior to curing at least one second fiber reinforced polyimide resin layer. At least one second fiber reinforced polyimide resin layer is heated to conform to the first sealing surface and the second sealing surface. At least one fiber reinforced polyimide resin layer is cured to provide a fluid tight seal between the first component and the second component.

In a further embodiment of any of the above, an outer diameter of the first component is less than an inner diameter of the second component.

In a further embodiment of any of the above, the first sealing surface is located on a first component flange and the second sealing surface is located on a second component flange.

In a further embodiment of any of the above, the first sealing surface is located on the outer diameter of the first component and the second sealing surface is located on the inner diameter of the second component.

In a further embodiment of any of the above, the first component is isolated from the second component with at least one fiber reinforced polyimide resin layer to prevent material reactions between the first component and the second component.

In a further embodiment of any of the above, at least one of the first sealing surface and the second sealing surface includes at least one of a surface irregularity and the at least one fiber reinforced polyimide resin layer conforms to the irregularity.

In accordance with the present invention there is disclosed a gas turbine engine assembly in accordance with claim <NUM>.

In an embodiment of the above, at least one of the first sealing surface and the second sealing surface includes at least one of a surface irregularity. The seal at least partially conforms to the surface irregularities.

In a further embodiment of any of the above, at least one fiber reinforced polyimide resin layer prevents material reactions between the first component and the second component.

In a further embodiment of any of the above, the first sealing surface is located on the outer diameter of the first component. The second sealing surface is located on the inner diameter of the second component.

The gas turbine engine <NUM> includes multiple fluid lines, each with fluid connections <NUM>, such as fuel line connections, bleed air connections, hydraulic fluid connections, and lubricant fluid connections, and scavenge air connections for collecting air with scavenged oil. The fluid connections are often located in parts of the gas turbine engine <NUM> that are subject to elevated temperatures radiating from hot parts, such as the combustor section <NUM> and the turbine section <NUM> or from hot fluids within the fluid lines. The temperature in the area of these fluid connections <NUM> can exceed <NUM> degrees Fahrenheit (<NUM> degrees Celsius) and may even exceed <NUM> degrees Fahrenheit (<NUM> degrees Celsius).

<FIG> is a cross-sectional view of an example fluid connection <NUM> of <FIG>. The fluid connection <NUM> includes a first component <NUM>, a second component <NUM>, and a seal <NUM> between the first component <NUM> and the second component <NUM>. In the illustrated examples, the first component <NUM> includes a fluid line in fluid communication with a fluid source <NUM>, such as a fuel tank or a high pressure fuel pump and the second component <NUM> includes a fitting. The first component <NUM> and the second component <NUM> could be made of the same metallic material or a different metallic material. The metallic material could be steel, titanium, or a nickel based alloy. In the illustrated example, the seal <NUM> separates the first component <NUM> from the second component <NUM>. This separation of the first component <NUM> from the second component <NUM> is particularly beneficial when the first component <NUM> and the second component <NUM> are made of a different metallic materials. In particular, the isolation from galvanic coupling is beneficial when the different metallic materials will interact adversely to each other in a manner such as but not including corrosion.

As shown in <FIG>, the first component <NUM> is cylindrical, however, the first component <NUM> could have other cross sectional shapes suitable for carrying the fluids under the operating pressure range. The first component <NUM> includes a first sealing surface <NUM> that mates with the seal <NUM>. The second component <NUM> includes a cylindrical portion <NUM> and a flange portion <NUM> extending from a distal end of the cylindrical portion <NUM>. The flange portion <NUM> is fastened to the engine static structure <NUM> through the use of a mechanical fastener <NUM>, such as a bolt. The cylindrical portion <NUM> includes a second sealing surface <NUM> on a radially inner side that mates with the seal <NUM>. In the illustrated example of <FIG>, the seal <NUM> has already reached a cured state that follows a profile of the first sealing surface <NUM> and the second sealing surface <NUM>.

A second sealing surface <NUM> on the second component <NUM> could also be sealed relative to a sealing surface <NUM> on the engine static structure <NUM> through a second seal 70B that is similar to the seal <NUM> described above. The second component <NUM> is fixed relative to the engine static structure <NUM> through bolts <NUM> that compress the second seal 70B.

<FIG> illustrates a cross-sectional view of the fluid connection <NUM>, prior to curing the seal <NUM> and connecting with the fluid source <NUM>. Also, the fluid connection <NUM> includes surface irregularities <NUM> in the first sealing surface <NUM> and surface irregularities <NUM> in the second sealing surface <NUM>. The surface irregularities <NUM>, <NUM> could be the result of manufacturing the first and second components <NUM>, <NUM> such as but not limited to asperities or surface roughness or could result from damage or repair of damage occurring along the first or second sealing surfaces <NUM>, <NUM>, respectively. The conformation of the seal <NUM>, typical of an elastomeric seal capability, to be functional with variations in seal thickness across the sealing surfaces also allows the seal <NUM> to accommodate manufacturing tolerances of both the first and second components <NUM>, <NUM> including diametric and axial tolerance mismatch as well as out-of-parallel mismatch such as differences in either parallelism or concentricity in assembly or in manufacture of the individual components.

Traditionally, seals used in applications above <NUM> degrees Fahrenheit (<NUM> degrees Celsius) were made from a graphite or ceramic material. However, seals made from graphite or ceramic do not follow contours of the first and second sealing surfaces <NUM>, <NUM> or fill surface irregularities and asperities <NUM>, <NUM> well because of the rigidity of the material. This resulted in prior art seals used in applications above <NUM> degrees Fahrenheit (<NUM> degrees Celsius) being prone to allow fluid to flow between the first and second sealing surfaces <NUM>, <NUM> and the seal and result in a fluid leak at the fluid connection <NUM>.

Prior to assembling the first and second components <NUM>, <NUM> with the seal <NUM>, the first and second sealing surfaces <NUM>, <NUM> are prepared to provide sufficient level of adhesion with the uncured seal <NUM>. In particular, it is desirable to have the first and second components <NUM>, <NUM> able to be separated from each other without destroying either the first or second component <NUM>, <NUM>. The second sealing surface <NUM> on the second component <NUM> and the sealing surface on the engine static structure <NUM> are prepared in a similar manner as the first and second sealing surfaces <NUM>, <NUM>.

Conventionally, the intent of bond surface preparation is to maximize strength and durability of the adhesion at the substrate to adhesive interface. In order to improve the strength and durability, bond surfaces are typically cleaned of surface oxides and degreased in order to remove organic surface contaminants by promoting improved adhesion via chemical bonding. However, because it is desirable to maintain that the first and second components <NUM>, <NUM> be separable from the seal <NUM> and each other during maintenance of the gas turbine engine <NUM>, the preparation of the first and second sealing surfaces <NUM>, <NUM> will not be done strictly per the above best practices.

Methods to limit the capability of the adhesion at the first and second sealing surfaces <NUM>, <NUM> are related to limiting the extent of mechanical and/or chemical adhesion. In regards to mechanical adhesion, there might be some applications where the condition of the first and second sealing surfaces <NUM>, <NUM> would be roughened such as by abrasion, to promote mechanical adhesion and also improving sealing capability by increasing the effective path length over the surface resisting the fluid pressure from inducing leakage. Limiting the surface roughening of the mating surfaces would decrease mechanical adhesion and is often needed for sealing materials that cannot sufficiently conform to the surface to take advantage of the increased area.

Chemical and dispersive adhesion applies for bonded joints and acts in conjunction with mechanical adhesion. The strength of the bonding contributed by these aspects of adhesion can be limited by providing a surface that inhibits or prevents chemical bonding or physiosorption. One way to inhibit bonding is to not remove a pre-existing surface layer such as an oxide on first and second sealing surfaces <NUM>, <NUM> or intentionally form additional or thicker layer of oxides on at least one of the first and second sealing surfaces <NUM>, <NUM>. It is recognized that oxidized surfaces of polymers is intended to be included in the general category of oxides above. Another way to inhibit chemical bonding is to apply a frangible layer to the sealing surfaces such as a brittle primer or ceramic/oxide layer. A third way to inhibit chemical and dispersive adhesion is to apply a non-adherent film or coating, durable over the operating range of the joint, such as a dry film lubricant. The frangible layer or non-adherent film / coat may be selectively incomplete over the gasket contact surfaces in a pattern such as concentric bands that do not have continuous path from high to low pressure side of the joint, thereby maintaining the fluid tightness while providing for natural fault lines allowing for future separation of the sealing surfaces. Omitting the degreasing step prior to mating surfaces is another way to minimize the adhesion at the substrate surface by keeping the non-adherent film already present from engine operation on the surface without having to add a new film. Typically, good chemical bonds fail within the layer of adhesive, not at the bond interface or within the surface treatment. By using a frangible layer or by pre-faulting the mating surfaces, the failure will be designed to be at the interface between the seal <NUM> and the surface <NUM>, <NUM> or in the surface pre-treatment. This failure mechanism is what allows the seal and mating surfaces to be separable while still allowing the one or both of the sealing surfaces <NUM>, <NUM> to be re-used.

After the first and second sealing surfaces <NUM>, <NUM> have been prepared, a desirable number of layers of fiber reinforced polyimide resin are placed between the first and second component <NUM>, <NUM>. The number of plies of fiber reinforced polyimide resin is dependent on the following: the desired size of the seal, the needed separation distance for galvanic isolation, the needed volume of material to fill surface irregularities. The fiber reinforced polyimide resin requires less compression set than materials without fiber reinforcement, thickness is more easily adjustable (can be built up thicker than just resin), and handling is easier than uncured resin. The fabric itself also gives flexibility, for example, the fabric can be constructed with different architectures, like braids or weaves.

Once the first and second components <NUM>, <NUM> have been assembled with the seal <NUM>, a clamping force is applied with a clamp <NUM> (<FIG>) to opposing ends of the second component <NUM> that draws the opposing ends together and compresses the seal <NUM> against the first and second sealing surfaces <NUM>, <NUM>. After a predetermined clamping force has been applied to the seal <NUM>, the first and second components <NUM>, <NUM> along with the seal <NUM> are heated to a point where the polyimide resin flows and imidizes. In one example, this requires heating the first and second components <NUM>, <NUM> and the seal <NUM> to a temperature greater than <NUM> degrees Fahrenheit (<NUM> degrees Celsius) and less than <NUM> degrees Fahrenheit (<NUM> degrees Celsius). In another example, the first and second components <NUM>, <NUM> and the seal <NUM> are heated to a temperature between <NUM> degrees Fahrenheit (<NUM> degrees Celsius) and <NUM> degrees Fahrenheit (<NUM> degrees Celsius).

Once the resin in the seal <NUM> is flowing, the seal <NUM> will follow a profile of the first and second sealing surfaces <NUM>, <NUM> and fill any surface irregularities <NUM>, <NUM> that may be present in the first and second sealing surfaces <NUM>, <NUM> as shown in <FIG>. After the first and second components <NUM>, <NUM> and the seal <NUM> have been heated to a point where the seal <NUM> flows and the seal <NUM> is allowed to cure. The second component <NUM> may need to have additional clamping force applied to a predetermined torque to account for the change in shape of the seal <NUM>. Although the illustrated example shows a clamping force being applied to the second component <NUM>, the first and second components <NUM>, <NUM> could have different profiles and a clamping force could be applied to the first component <NUM> as long as it compresses the seal <NUM> against the first and second sealing surfaces <NUM>, <NUM>.

When the first component <NUM> needs to be separated from the second component <NUM>, such as during maintenance of the gas turbine engine <NUM>, the first and second components <NUM>, <NUM> are able to be separated from each other. The ability to separate the first and second components <NUM>, <NUM> from each other is partially due to the steps taken above to limit the capability of the adhesion between first component <NUM> and the seal <NUM> and the second component <NUM> and the seal <NUM>. In particular, the preparation of the first and second sealing surfaces <NUM>, <NUM> to reduce adhesion contributes to separation of the first and second components <NUM>, <NUM>. Because the first and second components <NUM>, <NUM> are intended to be separated, the seal <NUM> forms a non-structural connection.

Once the first and second components <NUM>, <NUM> are separated from each other by the application of a separating force such as introducing relative motion between the components <NUM>, <NUM>, there may be remnants of the seal <NUM> material on the first and second sealing surfaces <NUM>, <NUM>. The remnants of the seal <NUM> can be removed by methods such as, but not limited to, sanding, scraping, or grinding before the first and second components are reattached by following the above method again. Also, because the above method can account for surface irregularities in the first and second sealing surfaces <NUM>, <NUM>, damage introduced during separation and removal of remnants of the seal <NUM> will not reduce the ability of the seal <NUM> to form a fluid tight connection again between the first component and the cured seal and the second component and cured seal. Therefore, this process can be repeated for the lifetime of the part.

<FIG> illustrate another example connection <NUM> formed by the method described above. The connection <NUM> is similar to the connection <NUM> except where described below or shown in the Figures. The fluid connection <NUM> includes a first component <NUM> that is accepted within an opening <NUM> in a second component <NUM>. A seal <NUM> is located adjacent a first sealing surface <NUM> on the first component <NUM> and a second sealing surface <NUM> on the second component <NUM>. In one example, the first component <NUM> is received within the second component <NUM> by heating the second component <NUM> to expand the opening <NUM> and/or chilling the first component <NUM> to create more clearance with the opening <NUM>. The seal <NUM> then becomes compressed when the first component <NUM> and the second component <NUM> return to ambient temperatures. Once the first and second components are fit together, any excess seal <NUM> material protruding from the opening <NUM> can be trimmed before the connection <NUM> is heated and cured as described above.

<FIG> illustrates another example connection <NUM> formed by the method described above. The connection <NUM> is similar to the connection <NUM> except where described below or shown in the Figures. The fluid connection <NUM> includes a first component <NUM> having a first component flange <NUM> and a second component <NUM> having a second component flange <NUM>. A seal <NUM> is located between a first sealing surface <NUM> on the first component flange <NUM> and a second sealing surface <NUM> on the second component <NUM>. The first component flange <NUM> and the second component flange <NUM> are compressed together through the use of a clamp <NUM> or bolts <NUM>. Once the first and second components <NUM>, <NUM> are compressed together, the connection <NUM> is heated and cured as described above.

<FIG> and <FIG> illustrate yet another example connection <NUM> formed by the method described above. The connection <NUM> is similar to the connection <NUM> except where described below or shown in the Figures. The fluid connection <NUM> includes a first component <NUM> having a first sealing surface <NUM> and a second component <NUM> having a second sealing surface <NUM>. A first sleeve half <NUM> and a second seal half <NUM> compress a seal <NUM> against the first and second components <NUM> and <NUM> to create a fluid tight seal between the first component <NUM> and the second component <NUM>. Once the first and second sleeve halves <NUM>, <NUM> are compressed together against the seal <NUM>, the connection <NUM> is heated and cured as described above.

<FIG> illustrate yet another example connection <NUM> formed by the method described above. The connection <NUM> is similar to the connection <NUM> except where described below or shown in the Figures. The fluid connection <NUM> includes a first component <NUM> having a first sealing surface <NUM> and a second component <NUM> having a second sealing surface <NUM>. A sealing wrap <NUM> surrounds the first and second components <NUM>, <NUM>. The sealing wrap <NUM> includes a seal <NUM> having a first end 470A and a second end 470B and a metal sheet <NUM> having a first end 471A and a second end 471B. The first ends 470A and 471A are staggered relative to each other such that the first end 470A extends past the first end 471A. Similarly, the second end 470B extends past the second end 471B such that the metal sheet <NUM> does not contact either the first component <NUM> or the second component <NUM>. As the sealing wrap <NUM> is wound tighter, the seal <NUM> is compressed against the first and second components <NUM>, <NUM>. Once the seal <NUM> is adequately compressed against the first and second components <NUM>, <NUM>, the connection <NUM> is heated and cured as described above.

Although the different non-limiting embodiments are illustrated as having specific components, the embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments.

Claim 1:
A method of sealing a first component (<NUM>;<NUM>;<NUM>;<NUM>;<NUM>) to a second component (<NUM>;<NUM>;<NUM>;<NUM>;<NUM>) comprising the steps of:
locating at least one fiber reinforced polyimide resin layer against a first sealing surface (<NUM>;<NUM>;<NUM>;<NUM>;<NUM>) on a first component (<NUM>...<NUM>) and against a second sealing surface(<NUM>;<NUM>;<NUM>;<NUM>;<NUM>) on a second component (<NUM>... <NUM>);
compressing the at least one fiber reinforced polyimide resin layer against the first sealing surface (<NUM>...<NUM>) and the second sealing surface (<NUM>...<NUM>) prior to curing the at least one fiber reinforced polyimide resin layer;
heating the at least one fiber reinforced polyimide resin layer to promote flow and conformation to the first sealing surface (<NUM>...<NUM>) and the second sealing surface (<NUM>...<NUM>);
curing the at least one fiber reinforced polyimide resin layer to provide a fluid tight seal between the first component (<NUM>...<NUM>) and the second component (<NUM>... <NUM>); characterised by:
coating at least one of the first sealing surface (<NUM>...<NUM>) and the second sealing (<NUM>...<NUM>) with an adhesion reducing material comprising at least one of a frangible oxide, a frangible primer, a non-adherent film, or a non-adherent coating.