# Patent

## Title
Flexible seal for gas turbine engine system

## Abstract

A gas turbine engine system includes an airframe support, a gas turbine engine mounted to the airframe support, a nozzle exhaust mounted to the airframe support, and a flexible annular seal having a first end that is attached to the gas turbine engine and a second end that is attached to an exhaust nozzle. The flexible annular seal may include a flexible annular wall that permits relative deflection between the gas turbine engine and the exhaust nozzle to facilitate the reduction of undesirable load transfer.

## Background
This invention was made with government support under Contract No. 2594747 awarded by the United States Navy. The government therefore has certain rights in this invention.


BACKGROUND OF THE INVENTION
This disclosure relates to the use of a flexible seal as a solution to eliminating an over constrained mounted system when specific entities of the system must be linked to one another in a particular manner that breaks the equilibrium each individual entity contained on its own. A particular example of this application is with a gas turbine engine.
Gas turbine engines are commonly known and used to propel aircraft. One or more gas turbine engines may be rigidly secured to an airframe of the aircraft.
Various aircraft conditions may result in large deflections and/or load transfers within the gas turbine engine system as well as between the engine and airframe. If the system is not in equilibrium, there is a possibility for undesirable load to be transferred between engine components, and between the engine and mounting system. These loads may induce undesirable stresses on the engine.
SUMMARY OF THE INVENTION
The disclosed flexible seals are for facilitating reduction of undesirable load transfer due to an over constrained mounted system.
An example gas turbine engine system includes an airframe support, a gas turbine engine mounted to the airframe support, an exhaust nozzle mounted to the airframe support, and a flexible annular seal having a first end that is attached to the gas turbine engine and a second end that is attached to the exhaust nozzle.
In one example, the flexible annular seal includes a flexible annular wall having a first end that is attachable to the gas turbine engine and a second end that is attachable to the exhaust nozzle. The flexible annular wall may include an elastomer, such as an elastomer composite of silicone and glass fiber.
An example method for facilitating reduction of undesirable load transfer in a gas turbine engine system includes establishing a connection between a first end of a flexible annular seal and the gas turbine engine, establishing a connection between a second end of the flexible annular seal and an exhaust nozzle, and deflecting the flexible annular seal in response to relative movement between the gas turbine engine and the exhaust nozzle to thereby limit stress transfer between the gas turbine engine and the exhaust nozzle.



BRIEF DESCRIPTION OF THE DRAWINGS
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows.
FIG. 1 schematically illustrates an example gas turbine engine system having a flexible seal between a gas turbine engine and an exhaust nozzle.
FIG. 2 schematically illustrates a possible deflection condition between the gas turbine engine and the exhaust nozzle.
FIG. 3 schematically illustrates another possible deflection condition between the gas turbine engine and the exhaust nozzle.
FIG. 4 illustrates an example lay-up of the elastomer composite of the flexible seal.
FIG. 5 illustrates an example of a single prominence elastomer composite flexible seal.
FIG. 6 illustrates a cross-section of the flexible seal of FIG. 5 and how it is linked to adjacent parts.
FIG. 7A illustrates an example of a double prominence elastomer composite flexible seal.
FIG. 7B illustrates a perspective view of the flexible seal of FIG. 7A.
FIG. 8A illustrates a cross-section of the flexible seal of FIG. 7A.
FIG. 8B illustrates a perspective view of a portion of the flexible seal of FIG. 7B.
FIG. 9 illustrates another example of a flexible seal having a plurality of corrugate sections.
FIG. 10 illustrates an example deflection state of a flexible seal.
FIG. 11 illustrates an example deflection state of a flexible seal having a plurality of corrugate sections.
FIG. 12 illustrates another example deflection state of a flexible seal having a plurality of corrugate sections.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 schematically illustrates a flexible seal 24 linking together a gas turbine engine 12 with an exhaust nozzle system 20. The gas turbine engine 12 generally includes a compression section 14, a combustion section 16, and a turbine section 18 that cooperate in a known manner to provide propulsion. Other engine sections, such as a fan section 27, may be included depending on the type of engine. The nozzle exhaust system 20 includes a nozzle duct 22 and, optionally, an afterburner system 30 (i.e. augmentor). An airframe 29 mounts to the gas turbine engine 12 near the compression section 14 and the turbine section 18. The airframe 29 also mounts to the nozzle exhaust system 20 between the afterburner system 30 and the nozzle duct 22.
As separate entities mounted to the airframe 29, the gas turbine engine 12 and the nozzle exhaust system 20 have deterministic load paths to the airframe 29. In contrast, when the gas turbine engine 12 and nozzle exhaust system 20 are hard linked together, the system no longer acts deterministically. The gas turbine engine 12 and airframe 29 act as an integral system. As such, the gas turbine engine 12 is a load bearing member supporting the airframe 29 and vise versa. These types of systems can transfer undesirable loads between one another. For example, a high impact landing can cause significant airframe 29 deflections, creating a high bending load in the gas turbine engine 12.
The gas turbine engine 12 and the nozzle exhaust system 20 must be coupled for the gas turbine engine 12 to operate properly within the aircraft. However, the gas turbine engine 12 and nozzle exhaust system 20 must remain in equilibrium with the airframe 29 in order to handle loads properly.
In the illustrated example, the axis 26 and axis 28 are generally parallel and coaxial, such as when there is no deflection between the gas turbine engine 12 and the nozzle exhaust system 20. However, under certain conditions, the nozzle exhaust system 20 may deflect relative to the gas turbine engine 12. In this regard, a flexible seal 24 located between the nozzle exhaust system 20 and the gas turbine engine 12 deflects to thereby minimize the load being transferred between the gas turbine engine 12 and the nozzle exhaust system 20 and allow system equilibrium to be maintained.
For example, the nozzle exhaust system 20 may deflect relative to the gas turbine engine 12 in response to the aircraft taking off, landing, an air maneuver, a bolter maneuver relative to an aircraft carrier, or thermally induced loads. That is, the flexible seal 24 may accommodate relatively large axial and transverse displacements between two rigid structures without significant load transfer.
FIG. 2 illustrates one example of a deflected state between the gas turbine engine 12 and the nozzle exhaust system 20. In this example, the deflection is such that the axes 26 and 28 become non-coaxial but remain generally parallel. Thus, the nozzle exhaust system 20 shifts relative to the engine 12. In this regard, the flexible seal 24 deflects and absorbs the loads from both the engine 12 and the nozzle 20. A rigid connection between the engine 12 and the nozzle exhaust system 20 would result in large transverse loads under this condition. As a result large stresses could form and put the parts in jeopardy of not meeting their necessary requirements.
FIG. 3 illustrates another example of a deflected state between the engine 12 and the nozzle exhaust system 20. In this example, the nozzle exhaust system 20 deflects relative to the engine 12 such that the axes 26 and 28 become non-parallel and non-coaxial. Similar to the example of FIG. 2, the flexible seal 24 deflects and gives the two parts the freedom to move without inducing large loads in each part.
Thus, as illustrated in the above examples, the flexible seal 24 is operable under a variety of different deflection conditions. As can be appreciated, the flexible seal 24 may also maintain load equilibrium under a variety of other deflection states than shown in these examples.
FIG. 4 illustrates a portion of the flexible seal 24. In this example, the flexible seal 24 includes an elastomer composite 38. The elastomer composite 38 includes reinforcement fibers 40 that are disposed within an elastomer matrix 42. Optionally, the flexible seal 24 may include only the elastomer, without the addition of reinforcement fillers.
The reinforcement fibers 40 may be selected from any suitable type of material for providing strength and flexibility of the flexible seal 24. In one example, the reinforcement fillers 40 are glass fibers and may be continuous, discontinuous, woven, non-woven, or provided in any suitable type of arrangement. For example, the glass fibers are somewhat flexible, but are strong in an axial fiber direction to provide the flexible seal 24 with strength while maintaining a desired degree of flexibility.
The elastomer matrix 42 may also be selected from any suitable type of material for providing flexibility and other desired properties of the flexible seal 24. For example, the elastomer matrix 42 may include any suitable type of elastomer material, such as silicone, which may also resist the temperatures associated with the exhaust gases.
The elastomer composite 38 may be formed into a desired shape of the flexible seal 24 using any suitable forming process. In one example, the elastomer composite 38 is formed using a molding process. One example molding process includes laying-up a desired number of plies of the reinforcement fibers 40, infiltrating the reinforcement fibers 40 with the elastomer matrix 42, and curing the elastomer matrix 42. Autoclave and flexible bagging techniques may also be employed. Given this description, one of ordinary skill in the art will recognize other type of molding or forming processes to meet their particular needs.
FIG. 5 illustrates an example flexible seal 52 that may be used as the flexible seal 24. Referring also to FIG. 6, the flexible seal 52 includes a flexible annular wall 54 that extends around a central axis 56. The flexible annular wall 54 includes a convex outer surface 58 and a concave inner surface 60 relative to the axis 56.
The flexible annular wall 54 extends between a first end 62 that is attachable to the discharge duct 18 and a second end 64 that is attachable to the nozzle duct 22 of the nozzle exhaust system 20. In this example, the first end 62 and the second end 64 include respective flanges 66 and 68. Each of the flanges 66 and 68 include openings 70 for receiving fasteners 72 to secure the flexible seal 52 within the gas turbine engine system 10. Alternatively, other desired shapes of the ends 62 and 64 may be provided for attaching the flexible seal 52.
Optionally, a reinforcement ring 74 may be used on a back side of either of the flanges 66 and 68 to secure the fasteners 72 and to provide stiffness to the flanges 66 and 68.
In the illustrated example, the fasteners 72 secure a clamp member 76, such as a Marmon clamp, to the respective flanges 66 and 68. The clamp members 76 secure the gas turbine engine 12 and the nozzle exhaust system 20 with the flexible seal 52. Once secured, the flexible annular wall 54 may deflect in response to relative deflection between the nozzle exhaust system 20 and the gas turbine engine 12 as described above. As can be appreciated, other suitable type of clamps or attachment techniques may be used to secure the gas turbine engine 12 and the nozzle exhaust system 20 with the flexible seal 52.
FIGS. 7A and 7B illustrate another example of a flexible seal 82 that may be used as the flexible seal 24 described above. In this example, the flexible seal 82 includes two corrugate sections 84 and 86 that are each somewhat similar to the flexible seal 52 of the previous example. Referring also to FIGS. 8A and 8B, each of the corrugate sections 84 and 86 includes a flexible annular wall 88 that extends about a central axis 89 between a first end 90 for attachment to the gas turbine engine 12 and a second end 92 for attachment to the nozzle exhaust system 20. Similar to the previous example, the first end 90 and the second end 92 include respective flanges 94 and 96 having openings 98 for receiving fasteners 100 to secure a reinforcement ring 102 with a clamp 104.
In this example, the flexible annular wall 88 is continuous such that the flexible seal 82 forms a single, monolithic piece. That is, the flexible annular wall 88 extends continuously, without a mechanical joint, between the first end 90 and the second end 92 and completely around the axis 89. The continuity may facilitate resistance of the flexible annular wall 88 to fatigue or other durability related factors.
The flexible seal 82 includes a central section 106 between the first corrugate section 84 and the second corrugate section 86. The central section 106 forms a valley 108 and a peak 110 between the corrugate sections 84 and 86. The central section 106 is flexible, similar to the corrugate sections 84 and 86. In some examples, a lower degree of flexibility of the central section 106 may be desired to resist ballooning of the central section 106 outwards, such as from gas pressure within the flexible seal 82. In this regard, a reinforcement member 112, such as a strap, may be provided within the valley 108 to stiffen the central section 106. Alternatively, a reinforcement member 112′, such as plies of reinforcement material, may be integrally formed into the flexible annular walls 88 to stiffen the central section 106. For example, the reinforcement member 112′ may be molded directly into the flexible annular walls 88 during a processing step, such as laying-up the reinforcement member 112′ during molding.
As illustrated in FIG. 9, two of the flexible seals 52 from the example of FIGS. 5 and 6 may be secured together to form a flexible seal 124 that may be used as the flexible seal 24. In this regard, each of the flexible seals 52 forms a respective corrugate section 126 and 128 that are mechanically attached together using a clamp 130. The clamp 130 is also annular and coextends circumferentially with the flanges 66 and 68. For example, the flange 66 of one of the flexible seals 52 is sealed against the flange 68 of the other flexible seal 52, and the clamp members 132 and 134 secure the flanges 66 and 68 via fasteners 136.
The above example flexible seals 52, 82, and 124 not only provide a sealed connection between the gas turbine engine 12 and the nozzle exhaust system 20, but they also provide a relatively low spring rate that permits deflection between the nozzle exhaust system 20 and the gas turbine engine 12 without significant transfer of load. Depending upon an amount of available space and a desired spring rate in a particular aircraft, a single seal such as the flexible seal 52, a double seal such as the flexible seal 82 or 124, or a flexible seal having more than two corrugate sections may be used to provide a desirable spring rate. For example, a greater number of corrugated sections generally provides a lower spring rate to accommodate the deflections of the adjacent parts.
In the disclosed examples, the spring rates and the deflections of the flexible seals 52, 82, or 124 depend at least in part on the geometry of the annular seal walls 54 or 88. FIG. 10 illustrates an example deflection state of the flexible seal 52. In this example, portions 150 and 152 of the flexible annular wall 54 bend in response to relative deflection between the gas turbine engine 12 and the nozzle exhaust system 20. The portion 150 contracts under compression of the bending, and portion 152 expands under tension of the bending. The curved shape of the annular seal wall 54 facilitates smooth deflection of the flexible seal 52 to provide a relatively low spring rate without significant transfer of load. As can be appreciated, the flexible seal 52 may also have other deflection states, depending on the deflection state, as illustrated in the example of FIGS. 1-3, for example.
FIG. 11 illustrates an example deflection state of the flexible seal 82. As can be appreciated, the deflection of the flexible seal 124 would be similar to the flexible seal 82. In this example, portions 160 and 162 of the flexible annular wall 88 bend in response to relative deflection between the gas turbine engine 12 and the nozzle exhaust system 20. The portions 160 contract under compression of the bending, and portion 162 expands under the tension of the bending. The curved shape of the annular seal wall 88 facilitates smooth deflection of the flexible seal 82 to provide a relatively low spring rate without significant transfer of load.
In this example, using the two corrugate sections 84 and 86 provides a relatively lower spring rate than the flexible seal 52. Likewise, using additional corrugate sections would provide relatively lower spring rates than using the two corrugate sections 84 and 86.
FIG. 12 illustrates another example deflection state of the flexible seal 82. In this example, a plane 170 corresponding to the central section 106 pivots relative to the corrugate sections 84 and 86 in response to deflection between the gas turbine engine 12 and the nozzle exhaust system 20 (e.g., torsional deflection or a combination of torsional and bending deflection). The pivoting causes one of the portions 160 and 162 to contract and the other portions 160 and 162 to expand. As can be appreciated, the flexible seal 82 and 124 may also have other deflection states, such as contraction of both portions 160 and 162 or expansion of both portions 160 and 162, for example.
Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments.
The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can be determined by studying the following claims.

## Claims

1. A flexible seal for use in a gas turbine engine system, comprising:
a flexible annular wall having a first end that is attachable to a gas turbine engine and a second end that is attachable to a nozzle exhaust, wherein the flexible annular wall comprises a first corrugate section including a first flange and a second corrugate section including a second flange mechanically secured against the first flange;
wherein the flexible annular wall comprises an elastomer composite having reinforcement fibers disposed within an elastomer matrix;
wherein the reinforcement fibers comprise glass fibers and the elastomer matrix comprises silicone.

2. A flexible seal for use in a gas turbine engine system, comprising:
a flexible annular wall having a first end that is attachable to a gas turbine engine and a second end that is attachable to a nozzle exhaust, wherein the flexible annular wall comprises a first corrugate section including a first flange and a second corrugate section including a second flange mechanically secured against the first flange;
wherein each of the first end and the second end comprises a flange for attachment;
wherein at least one of the flanges of the first end or second end comprises for receiving fasteners; and
a Marmon clamp secured to the flanges of the first end and second end using the fasteners.

3. A flexible seal for use in a gas turbine engine system, comprising:
a flexible annular wall having a first end that is attachable to a gas turbine engine and a second end that is attachable to a nozzle exhaust, wherein the flexible annular wall comprises a first corrugate section, a second corrugate section and a flexible central section joining the first corrugate section and the second corrugate section,
wherein the flexible central section has a lower degree of flexibility than the first corrugate section and the second corrugated section.

4. A flexible seal for use in a gas turbine engine system, comprising:
a flexible annular wall having a first end that is attachable to a gas turbine engine and a second end that is attachable to a nozzle exhaust, wherein the flexible annular wall comprises a first corrugate section, a second corrugate section and a flexible central section joining the first corrugate section and the second corrugate section,
wherein the flexible annular wall includes a reinforcement member within the flexible central section such that the flexible central section has a greater stiffness than the first corrugate section and the second corrugate section.