Variable pitch airfoil assembly for open fan rotor of engine having damping element

Abstract

A variable pitch airfoil assembly for an engine includes a disc having an annular shape extending about an axial direction and an airfoil coupled to the disc via a platform. The airfoil extends outwardly from the disc in a radial direction and is rotatable relative to the coiled pitch axis. The variable pitch airfoil assembly further includes a damping element positioned at least partially within the disk, outside of the platform, and adjacent to the periphery of the platform to provide vibration damping by friction between the damping element, the platform, and the disk while also allowing pitch variation of the airfoil.

Description

Technical Field

[0001] The present disclosure relates generally to open fan rotors for engines, and more particularly to variable pitch airfoil assemblies for open fan rotors for engines having damping elements to minimize vibrations therein. Background Art

[0002] At least some gas turbine engines, such as turbofan engines, include a fan, a core engine, and a power turbine. The core engine includes at least one compressor, a combustor, and a high-pressure turbine, which are connected together in a series flow relationship. More specifically, the compressor and the high-pressure turbine are connected by a first drive shaft to form a high-pressure rotor assembly. The air entering the core engine is mixed with fuel and ignited to form a high-energy gas flow. The high-energy gas flow flows through the high-pressure turbine to rotatably drive the high-pressure turbine, so that the first drive shaft rotatably drives the compressor. The gas flow expands when it flows through the low-pressure turbine positioned behind the high-pressure turbine. The low-pressure turbine includes a rotor assembly having a fan connected to a second drive shaft. The low-pressure turbine rotatably drives the fan through the second drive shaft. The gas turbine engine further includes various airfoils or blades throughout each stage of the engine, such as fan blades, compressor blades, turbine blades, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] A full and enabling disclosure of the present disclosure, including the best mode thereof, to one of ordinary skill in the art is set forth in the specification with reference to the accompanying drawings, in which:

[0004] Figure 1 is a schematic cross-sectional view of a gas turbine engine having an unducted fan according to an exemplary aspect of the present disclosure;

[0005] Figure 2 is a perspective view of a variable pitch fan assembly of a gas turbine engine according to an exemplary aspect of the present disclosure;

[0006] Figure 3 is a cross-sectional view of a root portion of an airfoil coupled to a disk according to an exemplary aspect of the present disclosure;

[0007] Figure 4 is a perspective view of a disk of an airfoil assembly of a gas turbine engine according to an exemplary aspect of the present disclosure;

[0008] Figure 5 is a cross-sectional view of a variable pitch fan assembly according to an exemplary aspect of the present disclosure, particularly showing an airfoil coupled to a disk;

[0009] Figure 6 is a cross-sectional view of a damping element of a variable pitch fan assembly according to an exemplary aspect of the present disclosure;

[0010] Figure 7 is a partial perspective view of a plurality of damping elements of a variable pitch fan assembly arranged around a perimeter of a blade platform according to an exemplary aspect of the present disclosure; and

[0011] Figure 8 is a partial bucket diagram of a plurality of damping elements of a variable pitch fan assembly arranged on a first side of a blade platform according to an exemplary aspect of the present disclosure. DETAILED DESCRIPTION

[0012] Reference will now be made in detail to the present embodiments of the present disclosure, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter references to refer to features in the drawings. Like or similar reference numbers in the drawings and description have been used to refer to like or similar parts of the present disclosure.

[0013] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. In addition, unless otherwise specifically stated, all embodiments described herein should be considered exemplary.

[0014] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0015] The term "at least one" in a context such as "at least one of A, B, or C" means only A, only B, only C, or any combination of A, B, and C.

[0016] The terms “turbomachine” or “turbomachinery” refer to a machine that includes one or more compressors, a heat generating section (eg, a combustion section), and one or more turbines that together produce a torque output.

[0017] The term "gas turbine engine" refers to an engine having a turbine as all or part of its power source. Example gas turbine engines that may be used in the present disclosure include an unducted turbofan engine, a ducted turbofan engine, or a turboprop engine.

[0018] The terms "upstream" and "downstream" refer to the relative directions of the flow of a fluid in a fluid path. For example, "upstream" refers to the direction from which the fluid is flowing, and "downstream" refers to the direction toward which the fluid is flowing.

[0019] As used herein, the terms "axial" and "axially" refer to directions and orientations extending substantially parallel to the centerline of the gas turbine engine. Additionally, the terms "radial" and "radially" refer to directions and orientations extending substantially perpendicular to the centerline of the gas turbine engine. Additionally, as used herein, the terms "circumferential" and "circumferentially" refer to directions and orientations extending arcuately around the centerline of the gas turbine engine.

[0020] Unless otherwise specified herein, the terms "coupled," "fixed," "attached to," and the like refer to both direct coupling, fixing, or attachment as well as indirect coupling, fixing, or attachment through one or more intermediate components or features.

[0021] As used herein, the terms “first,” “second,” and “third” may be used interchangeably to distinguish one component from another, and are not intended to indicate the position or importance of each component.

[0022] For ease of description below, the terms "vertical", "radial", "axial", "longitudinal" and their derivatives shall relate to the embodiments as they are oriented in the accompanying drawings. However, it shall be understood that the embodiments may employ various alternative variations unless expressly indicated to the contrary. It shall also be understood that the embodiments shown in the drawings and described in the following specification are merely exemplary embodiments of the present disclosure. Therefore, specific dimensions and other physical characteristics associated with the embodiments disclosed herein shall not be considered limiting.

[0023] The term "adjacent" as used herein with respect to two walls or surfaces means that the two walls or surfaces are in contact with each other, or that the two walls or surfaces are separated only by one or more non-structural layers, and that the two walls or surfaces are in a series contacting relationship with the one or more non-structural layers (i.e., a first wall / surface contacts the one or more non-structural layers, and the one or more non-structural layers contacts the second wall / surface).

[0024] As used herein, the term "integrated" used to describe a structure refers to a structure that is formed from a continuous material or group of materials without seams, connecting joints, etc. The integrated, monolithic structures described herein may be formed by additive manufacturing to have the structure, or alternatively by a layup process, a casting process, etc.

[0025] Reference will now be made in detail to the present embodiments of the present disclosure, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter references to features in the drawings. Like or similar reference numbers in the drawings and description have been used to refer to like or similar parts of the present disclosure.

[0026] Variable pitch open rotor fans may experience high vibrations due to flutter, fan blade wake, engine core vibrations, or other synchronous excitations. Conventional vibration damping techniques do not allow the blades to change pitch. Therefore, in an embodiment, the present disclosure relates to a platform-under-damping concept for variable pitch fan blades. In an embodiment, the damping element is placed in the outer periphery of the blade platform, for example, in a groove of a disk. Such an embodiment utilizes centrifugal loads to load on the damper contact surface. Any movement on the blade platform (also called blade button) is damped by the relative movement between the blade platform and the damper and the damper and the hub disk.

[0027] Therefore, the present disclosure provides many technical advantages not found in the prior art, such as adequate damping for the fundamental mode, and allowing blade pitch variations. In addition, the damping elements described herein are low-cost passive devices that are retrofittable and do not require design changes to existing blade components.

[0028] Referring now to the drawings, wherein like numerals represent like elements throughout the several views, Figure 1 is a schematic cross-sectional view of a gas turbine engine 10 according to an embodiment of the present disclosure. Specifically, Figure 1 A turbofan engine having a rotor assembly having a single-stage unducted rotor blade is provided. In this manner, the rotor assembly may be referred to herein as a "unducted fan" or the entire engine 10 may be referred to as a "unducted turbofan engine". In addition, Figure 1 The engine 10 includes a third flow path extending from the compressor section to the rotor assembly above the turbine, as will be explained in greater detail below.

[0029] For reference, the engine 10 defines an axial direction A, a radial direction R, and a circumferential direction C. Further, the engine 10 defines an axial centerline or longitudinal axis 12 extending along the axial direction A. Generally speaking, the axial direction A extends parallel to the longitudinal axis 12, the radial directions R extend outwardly and inwardly from the longitudinal axis 12 to the longitudinal axis 12 in a direction orthogonal to the axial direction A, and the circumferential direction C extends three hundred sixty degrees (360°) around the longitudinal axis 12. The engine 10 extends between a front end 14 and a rear end 16, e.g., along the axial direction A.

[0030] The engine 10 includes a rotating cone 18 having a fan section 50 and a turbine 20 located downstream thereof. Generally speaking, the turbine 20 includes a compressor section, a combustion section, a turbine section, and an exhaust section in a series flow order. Specifically, as shown in FIG. Figure 1As shown, the turbine 20 includes a core shroud 22 that defines an annular core inlet 24. The core shroud 22 also at least partially surrounds a low-pressure system and a high-pressure system. For example, the core shroud 22 shown at least partially surrounds and supports a supercharger or low-pressure ("LP") compressor 26 for pressurizing air entering the turbine 20 through the core inlet 24. A high-pressure ("HP"), multi-stage, axial-flow compressor 28 receives the pressurized air from the LP compressor 26 and further increases the pressure of the air. The pressurized air flow flows downstream to the combustor 30 of the combustion section, where fuel is injected into the pressurized air flow and ignited to increase the temperature and energy level of the pressurized air.

[0031] It should be understood that, as used herein, the terms "high / low speed" and "high / low pressure" are interchangeable for high pressure / high speed systems and low pressure / low speed systems. In addition, it should be understood that the terms "high" and "low" are used in the same context to distinguish between the two systems and are not meant to imply any absolute speed or pressure values.

[0032] The high-energy combustion products flow downstream from the combustor 30 to the HP turbine 32. The HP turbine 32 drives the HP compressor 28 via a high-pressure shaft 36. In this regard, the HP turbine 32 is drivingly coupled to the HP compressor 28. The high-energy combustion products then flow to the LP turbine 34. The LP turbine 34 drives the LP compressor 26 and components of the fan section 50 via an LP shaft 38. In this regard, the LP turbine 34 is drivingly coupled to components of the LP compressor 26 and the fan section 50. In this example embodiment, the LP shaft 38 is coaxial with the HP shaft 36. After driving each of the HP turbine 32 and the LP turbine 34, the combustion products exit the turbine 20 through a turbine exhaust nozzle 40.

[0033] Thus, the turbine 20 defines a working gas flow path or core duct 46 extending between the core inlet 24 and the turbine exhaust nozzle 40. The core duct 46 is an annular duct positioned generally inwardly of the core shroud 22 in the radial direction R. The core duct 46 (e.g., the working gas flow path through the turbine 20) may be referred to as a secondary flow.

[0034] The fan section 50 includes a fan 52, which is a primary fan in this example embodiment. Figure 1 In the illustrated embodiment, the fan 52 is an open rotor or unducted fan 52. In this manner, the engine 10 may be referred to as an open rotor engine.

[0035] As shown, fan 52 includes an array of fan blades 54 ( Figure 1 Only one is shown in the figure). The fan blades 54 are rotatable, for example, about the longitudinal axis 12. As described above, the fan 52 is drivingly coupled to the LP turbine 34 via the LP shaft 38. Figure 1In the embodiment shown in FIG. 5 , the fan 52 is coupled to the LP shaft 38 via a reduction gearbox 55 , such as in an indirect drive or gear drive configuration.

[0036] In addition, the array of fan blades 54 can be arranged at equal intervals around the longitudinal axis 12. Each fan blade 54 has a root and a tip and a span defined therebetween. Each fan blade 54 defines a central blade axis 56. For this embodiment, each fan blade 54 of the fan 52 can rotate around its central blade axis 56, for example, in unison with each other. One or more actuators 58 are provided to facilitate such rotation, and therefore, can be used to change the pitch of the fan blades 54 around their respective central blade axes 56.

[0037] The fan section 50 further includes a fan guide vane array 60 including fan guide vanes 62 ( Figure 1 For this embodiment, the fan guide vanes 62 are not rotatable about the longitudinal axis 12. Each fan guide vane 62 has a root and a tip and a span defined therebetween. The fan guide vanes 62 may be as shown in FIG. Figure 1 It is shown uncovered, or alternatively, may be covered, for example, by an annular shroud spaced outwardly in the radial direction R from the tip of the fan guide vanes 62 or attached to the fan guide vanes 62 .

[0038] Each fan guide vane 62 defines a central blade axis 64. For this embodiment, each fan guide vane 62 in the fan guide vane array 60 rotates about its respective central blade axis 64, e.g., in unison with one another. One or more actuators 66 are provided to facilitate such rotation, and thus, may be used to change the pitch of the fan guide vanes 62 about their respective central blade axis 64. However, in other embodiments, each fan guide vane 62 may be fixed or unable to pitch about its central blade axis 64. The fan guide vanes 62 are mounted to a fan shroud 70.

[0039] like Figure 1As shown, in addition to the unducted fan 52, the rear of the fan 52 also includes a ducted fan 84, so that the engine 10 includes both ducted fans and unducted fans, both of which are used to generate thrust through air movement without the need for a passage through at least a portion of the turbine 20 (e.g., for the illustrated embodiment, without the need for a passage through the HP compressor 28 and the combustion section). The ducted fan 84 can rotate about the same axis as the fan blades 54 (e.g., the longitudinal axis 12). For the illustrated embodiment, the ducted fan 84 is driven by the low-pressure turbine 34 (e.g., coupled to the LP shaft 38). In the illustrated embodiment, as described above, the fan 52 can be referred to as a primary fan, while the ducted fan 84 can be referred to as a secondary fan. It should be understood that the terms "primary" and "secondary" are used for convenience and do not imply any special importance, authority, etc.

[0040] The ducted fan 84 includes a plurality of fan blades ( Figure 1 The fan blades of the ducted fan 84 may be arranged at equal intervals around the longitudinal axis 12. Each blade of the ducted fan 84 has a root and a tip and a span defined therebetween.

[0041] The fan cowl 70 annularly surrounds at least a portion of the core cowl 22, and is generally positioned outside of at least a portion of the core cowl 22 in the radial direction R. Specifically, a downstream section of the fan cowl 70 extends over a front portion of the core cowl 22 to define a fan duct flow path, or simply a fan duct 72. According to this embodiment, the fan flow path or the fan duct 72 may be understood to form at least a portion of the tertiary flow of the engine 10.

[0042] Incoming air may enter through a fan duct inlet 76, pass through a fan duct 72, and may be exhausted through a fan exhaust nozzle 78 to generate propulsion. The fan duct 72 is an annular duct positioned generally outside the core duct 46 in the radial direction R. The fan shroud 70 and the core shroud 22 are connected together and are supported by a plurality of substantially radially extending, circumferentially spaced stationary struts 74 ( Figure 1 The fan duct 72 and the core duct 46 may be supported by the fan duct 72 and the core duct 46. ...

[0043] The engine 10 also defines or includes an inlet duct 80. The inlet duct 80 extends between the engine inlet 82 and the core inlet 24 / fan duct inlet 76. The engine inlet 82 is generally defined at the front end of the fan cowl 70 and is positioned between the fan 52 and the fan guide vane array 60 along the axial direction A. The inlet duct 80 is an annular duct positioned inside the fan cowl 70 along the radial direction R. Air flowing downstream along the inlet duct 80 is divided (but not necessarily evenly) into the core duct 46 and the fan duct 72 by the fan duct splitter or the leading edge 44 of the core cowl 22. In the illustrated embodiment, the inlet duct 80 is wider than the core duct 46 along the radial direction R. The inlet duct 80 is also wider than the fan duct 72 along the radial direction R.

[0044] It is noteworthy that for the illustrated embodiment, the engine 10 includes one or more features to improve the efficiency of the third flow thrust Fn3S (e.g., the thrust generated by the airflow through the fan duct 72 that leaves through the fan exhaust nozzle 78 and is at least partially generated by the ducted fan 84). Specifically, the engine 10 further includes an array of inlet guide vanes 86, which are positioned in the inlet duct 80, upstream of the ducted fan 84 and downstream of the engine inlet 82. The inlet guide vane 86 array is arranged around the longitudinal axis 12. For this embodiment, the inlet guide vanes 86 cannot rotate around the longitudinal axis 12. Each inlet guide vane 86 defines a central blade axis (not marked for clarity) and can rotate around its respective central blade axis, for example, in unison with each other. In this way, the inlet guide vanes 86 can be regarded as variable geometry components. One or more actuators 88 are provided to facilitate this rotation, and therefore, can be used to change the pitch of the inlet guide vanes 86 around their respective central blade axes. However, in other embodiments, each inlet guide vane 86 may be fixed or non-pitchable about its central vane axis.

[0045] Further, engine 10 includes an array of outlet guide vanes 90 positioned downstream of ducted fan 84 and upstream of fan duct inlet 76. Like array of inlet guide vanes 86, array of outlet guide vanes 90 is not rotatable about longitudinal axis 12. However, for the illustrated embodiment, unlike array of inlet guide vanes 86, array of outlet guide vanes 90 is configured as fixed-pitch outlet guide vanes.

[0046] In addition, it should be understood that for the illustrated embodiment, the fan exhaust nozzle 78 of the fan duct 72 is further configured as a variable geometry exhaust nozzle. In this manner, the engine 10 includes one or more actuators 68 for adjusting the variable geometry exhaust nozzle. For example, the variable geometry exhaust nozzle can be configured to change the total cross-sectional area (e.g., the area of ​​the nozzle in a plane perpendicular to the longitudinal axis 12) to adjust the amount of thrust generated based on one or more engine operating conditions (e.g., temperature, pressure, mass flow, etc. of the airflow through the fan duct 72). Fixed geometry exhaust nozzles may also be used.

[0047] The combination of the inlet guide vane 86 array located upstream of the ducted fan 84, the outlet guide vane 90 array located downstream of the ducted fan 84, and the fan exhaust nozzle 78 can produce a more efficient third flow thrust Fn3S during one or more engine operating conditions. In addition, by introducing geometric changes to the inlet guide vanes 86 and the fan exhaust nozzle 78, the engine 10 can produce a more efficient third flow thrust Fn3S under a relatively wide array of engine operating conditions, including takeoff and climb (where the maximum total engine thrust FnTotal is generally required) and cruise (where a smaller amount of total engine thrust FnTotal is generally required).

[0048] In addition, reference Figure 1 In an exemplary embodiment, the air passing through the fan duct 72 may be relatively cooler (e.g., lower temperature) than one or more fluids used in the turbine 20. As such, one or more heat exchangers 94 may be positioned in thermal communication with the fan duct 72. For example, one or more heat exchangers 94 may be disposed within the fan duct 72 and used to cool one or more fluids from the core engine, where air passes through the fan duct 72 as a resource for removing heat from the fluid (e.g., compressor bleed air, oil, or fuel).

[0049] Although not depicted, heat exchanger 94 may be an annular heat exchanger extending substantially 360 degrees (e.g., at least 300 degrees, such as at least 330 degrees) in fan duct 72. In this manner, heat exchanger 94 may effectively utilize air passing through fan duct 72 to cool one or more systems (e.g., lube oil system, compressor bleed air, electrical components, etc.) of engine 10. Heat exchanger 94 uses air passing through fan duct 72 as a heat sink and correspondingly increases the temperature of air exiting heat exchanger 94 downstream of fan exhaust nozzle 78.

[0050] It should be understood that Figure 1 The engine 10 shown in and described herein is merely an example, and embodiments of the present disclosure may also be incorporated into other gas turbine engines, such as a ducted turbofan engine.

[0051] Reference now Figure 1 and Figure 2 , fan section 50 includes a variable pitch fan assembly 48 coupled to a disk 42 having a plurality of disk segments 92 in a spaced-apart manner. Disk 42 may have a generally annular shape about an axial direction A. Further, in an embodiment, fan blades 54 extend outwardly from disk 42 generally along a radial direction R. Each fan blade 54 may also be rotatable relative to disk 42 about a central blade axis 56 by virtue of fan blades 54 being operably coupled to an actuator 58, which is configured to collectively and uniformly change the pitch of fan blades 54.

[0052] Especially refer to Figure 2 , showing Figure 1 1. A perspective view of an embodiment of a fan assembly 48 of a fan section 50 of an engine 10 of FIG. For the embodiment shown, the fan assembly 48 includes twelve (12) fan blades 54. From a load perspective, such a number of blades can allow the span of each fan blade 54 to be reduced so that the overall diameter of the fan assembly 48 can also be reduced (e.g., reduced to about twelve feet in an exemplary embodiment). That is, in other embodiments, the fan assembly 48 can have any suitable number of blades and any suitable diameter. In certain suitable embodiments, the fan includes at least eight (8) blades. In another suitable embodiment, the fan can have at least fifteen (15) blades. In yet another suitable embodiment, the fan can have at least eighteen (18) blades. In one or more of these embodiments, the fan includes twenty-six (26) or fewer blades, such as twenty (20) or fewer blades.

[0053] See also Figure 1 and Figure 2 The fan blade 54 generally includes a trunnion 96 and a blade spar 98 ( Figure 1 ), the fan airfoil 100 is coupled to the blade spar 98 by a physical attachment or bonding process. The trunnion 96 and the blade spar 98 may be made as an integral component by any suitable manufacturing process, including but not limited to any suitable bonding process, such as by metallurgical bonding, or a casting process, or a physical attachment process, to name a few non-limiting examples. In one example, the trunnion 96 is integral with the blade spar 98, where both are one form of metallic material, or another form of a metal / polymer matrix composite (PMC) mixture. Other material types are also contemplated.

[0054] See also Figure 2 and Figure 3 , the trunnion 96 is connected to the LP shaft 38 ( Figure 1 ) driven disk 42. The connection point between LP shaft 38 and disk 42 is Figure 14. As indicated in FIG. 4 as being located at the axial forward end of the disk 42, but in other embodiments, the LP shaft 38 may be connected to the disk 42 at other locations, including at the axial rearward end of the disk 42.

[0055] In one embodiment, as shown, trunnion 96 is coupled to disk 42 via top bearing 102 and bottom bearing 104. It will be appreciated that top bearing 102 and bottom bearing 104 help locate and support trunnion 96 within disk 42, but also critically allow relative movement between trunnion 96 and disk 42. Top bearing 102 may be used in some form to provide a wheelbase to react to torque during operation of fan blade 54. Bottom bearing 104 may be used in some form to provide primary radial retention of fan blade 54.

[0056] A plurality of inserts may be used to occupy the space defined between the top bearing 102 and the bottom bearing 104 and also between the inner wall of the disc 42 and the outer surface of the trunnion 96. Such inserts may be connected to either the trunnion 96 or the disc 42. Figure 3 1 and 2. Inserts 106 and 108 are shown in FIG. Inserts 106 and 108 may take a variety of forms, including but not limited to foam inserts. In one form, foam inserts 106 and 108 may be closed foam structures formed of any suitable material, including but not limited to metal foam. Foam inserts 106 and 108 may be used to reduce the volume required when supplying hydraulic fluid to cause trunnion 96 to move and thereby generate loads on top bearing 102 and bottom bearing 104.

[0057] Figure 3 The illustrated structure includes the use of multiple sealing elements to prevent foreign matter intrusion or lubricant leakage. O-rings 110 can be used to seal between various stationary parts and moving parts. For example, O-rings 110 are located between the relatively stationary foam insert 106 and the inner surface of the disk 42. O-rings 110 are also located between the foam insert 108 and the bearing seat of the top bearing 102, wherein such O-rings allow sliding movement between the bearing seat of the top bearing 102 and the foam insert 106.

[0058] Reference now Figure 3 and Figure 4 The disk 42 includes several features, including a plurality of trunnion holes 112, each trunnion hole 112 being configured to receive an associated trunnion 96, such as Figure 3 The trunnion 96 is shown. Each trunnion hole 112 is arranged along a central hole axis 114, and the trunnion 96 is inserted along the central hole axis 114. When inserted, the trunnion 96 can be rotated about the central hole axis 114 to rotate the fan blade 54, wherein such rotation can be achieved by a bell crank 116 attached to the trunnion 96. An actuator (e.g., Figure 158) can be used to manipulate the orientation of the bell crank 116, thereby manipulating the orientation of the fan blades 54. It will be appreciated that in some embodiments, the central blade axis 56 ( Figure 1 ) may coincide with the center hole axis 114, but need not coincide in other embodiments. It will also be understood that the center blade axis 56 and the center hole axis 114 are substantially transverse to the longitudinal axis 12 ( Figure 1 ). In some forms, one or both of the central blade axis 56 and the central bore axis 114 are perpendicular to the longitudinal axis 12.

[0059] like Figure 4 As particularly shown in FIG. 4 , the disk 42 is annular in shape and includes several features to facilitate its incorporation into the gas turbine engine 10 ( Figure 1 ). The annular shape includes a relatively large open interior 118. The disk 42 is configured to rotate about the longitudinal axis 12 when mounted on the gas turbine engine 10. The front end 120 can be connected to the rotating cone 18 ( Figure 1 ) connection, the rear end 122 can be connected to the LP shaft 138 ( via a plurality of fasteners inserted through corresponding fastener holes in the plurality of fastener holes 124 Figure 1 ).

[0060] Reference now Figure 5 , a cross-sectional view of a portion of a variable pitch airfoil assembly 150 for an engine is shown according to the present disclosure. Specifically, the variable pitch airfoil assembly 150 may be a variable pitch fan assembly, which is described herein. Figure 1 1 is a portion of a fan section 50 of a gas turbine engine 10. As shown, the variable pitch airfoil assembly 150 includes a disk 152 having an annular shape extending about an axial direction A. In an embodiment, for example, the disk 152 may be configured similarly to the disk 42 ( Figure 1-4 ). In addition, as shown, the variable pitch airfoil assembly 150 includes an airfoil 154 coupled to the disk 152 via a platform 156. In addition, as shown, the airfoil 154 extends outwardly from the disk 152 in a radial direction R and is rotatable relative to the disk 152 about a pitch axis 158.

[0061] Especially refer to Figure 5-8 , the variable pitch airfoil assembly 150 further includes at least one damping element 160 for damping vibrations thereof. In an embodiment, for example, as shown, the damping element 160 is at least partially positioned within the disk 152, outside the platform 156 and adjacent to a perimeter 162 ( Figure 5 and Figure 6 ) so as to provide vibration damping through friction between the damping element 160, the platform 156 and the disk 152.

[0062] In a specific embodiment, if Figure 5-6As shown, the damping element 160 is positioned within the recess 164 of the disk 152, adjacent to the periphery 162 of the platform 156. Figure 6 152, the damping element 160 includes a first surface 166 and a second surface 168, the first surface 166 contacts the inner surface 170 of the groove 164 of the disk 152, and the second surface 168 contacts the outer surface 172 of the platform 156, which is defined, for example, by the perimeter 162 of the platform 156. More specifically, as shown, the first surface 166 of the damping element 160 is flat, while the second surface 168 of the damping element 160 is curved so as to follow the curvature of the platform 156. Therefore, in the illustrated embodiment, friction between the damping element 160, the platform 156, and the disk 152 is generated due to the centrifugal force loading the first surface 166 and the second surface 168 of the damping element 160.

[0063] It should be appreciated that any suitable number of damping elements 160 may be arranged in the variable pitch airfoil assembly 150 to provide a desired amount of damping, and the damping elements 160 may be arranged in any suitable manner. Figure 7 As shown, the variable pitch airfoil assembly 150 includes a plurality of damping elements 160 positioned at least partially within the disk 152, around the platform 156 ( Figure 6 ) around the perimeter 162. In addition, as shown, the plurality of damping elements 160 are evenly spaced around the perimeter of the platform 156. In an alternative embodiment, as shown in FIG. Figure 8 As shown, the plurality of damping elements 160 are positioned on a first side 174 of the perimeter 162 of the platform 156. In such an embodiment, the plurality of damping elements 160 are configured to ensure multiple points of contact with the platform 156, thereby ensuring effectiveness regardless of the blade pitch angle. Additionally, as shown, the plurality of damping elements 160 contact each other on the first side 174 of the perimeter 162 of the platform 156. In further embodiments, the plurality of damping elements 160 may be arranged on the first side 174 of the perimeter 162 of the platform 156 with a space or gap therebetween.

[0064] Further aspects are provided by the subject matter of the following clauses:

[0065] A variable pitch airfoil assembly for an engine, the variable pitch airfoil assembly comprising: a disk having an annular shape extending about an axial direction; an airfoil coupled to the disk via a platform, the airfoil extending outwardly from the disk in a radial direction and rotatable about a pitch axis relative to the disk; and a damping element at least partially positioned within the disk, outside the platform and adjacent to a periphery of the platform so as to provide vibration damping by friction between the damping element, the platform and the disk while also allowing variation in the pitch of the airfoil.

[0066] A variable pitch airfoil assembly as described in any of the preceding clauses, wherein the damping element is positioned within a recess of the disk adjacent to a periphery of the platform.

[0067] A variable pitch airfoil assembly as described in any of the preceding clauses, wherein the damping element comprises a first surface contacting an interior surface of the recess of the disc and a second surface contacting the platform.

[0068] A variable pitch airfoil assembly as described in any preceding clause, wherein the first surface of the damping element is planar and the second surface is arcuate.

[0069] A variable pitch airfoil assembly as described in any of the preceding clauses, further comprising a plurality of damping elements positioned at least partially within the disk around a perimeter of the platform.

[0070] A variable pitch airfoil assembly as described in any of the preceding clauses, wherein the plurality of damping elements are evenly spaced around the perimeter of the platform.

[0071] A variable pitch airfoil assembly as described in any of the preceding clauses, wherein the plurality of damping elements are positioned on a first side of the periphery of the platform.

[0072] A variable pitch airfoil assembly as described in any of the preceding clauses, wherein the plurality of damping elements contact each other at a first side of the periphery of the platform.

[0073] A variable pitch airfoil assembly as described in any of the preceding clauses, further comprising a plurality of airfoils coupled to the disk in a spaced apart manner via a plurality of trunnions.

[0074] A variable pitch airfoil assembly as described in any preceding clause, wherein the disk comprises a plurality of disk segments.

[0075] A variable pitch airfoil assembly as described in any preceding clause, wherein the variable pitch airfoil assembly is a variable pitch fan assembly and the airfoil is a fan blade.

[0076] A variable pitch airfoil assembly as described in any preceding clause, wherein the variable pitch fan assembly is an unducted fan assembly of an engine.

[0077] An engine comprises: a ductless fan section; a turbine, the turbine being located downstream of the ductless fan section, the turbine comprising a compressor section, a combustion section, a turbine section and an exhaust section, the ductless fan section comprising a variable pitch fan assembly, the variable pitch fan assembly comprising: a disk, the disk having an annular shape extending about an axial direction; a plurality of fan blades, the plurality of fan blades being coupled to the disk via a plurality of blade platforms, each of the plurality of fan blades extending outwardly from the disk in a radial direction and being rotatable relative to the disk about a respective pitch axis; and a plurality of damping elements, the plurality of damping elements being at least partially positioned within the disk, outside each of the plurality of blade platforms and adjacent to a periphery of each of the plurality of blade platforms so as to provide vibration damping by friction between the plurality of damping elements, the plurality of blade platforms and the disk, while also allowing a pitch variation of each of the plurality of fan blades.

[0078] An engine as claimed in any preceding clause, wherein the plurality of damping elements are positioned within the plurality of grooves of the disk adjacent to the periphery of the plurality of blade platforms.

[0079] An engine according to any of the preceding clauses, wherein each of the plurality of damping elements comprises a first surface contacting an inner surface of one of the plurality of grooves of the disk and a second surface contacting one of the plurality of blade platforms, wherein the first surfaces of the plurality of damping elements are flat and the second surfaces are curved.

[0080] An engine as in any preceding clause, wherein friction between the plurality of damping elements, the plurality of blade platforms and the disk is generated due to centrifugal forces loading the first and second surfaces of the plurality of damping elements.

[0081] An engine as described in any preceding clause, wherein the plurality of damping elements adjacent the perimeter of each of the plurality of blade platforms are evenly spaced around the perimeter.

[0082] An engine as described in any of the preceding clauses, wherein a plurality of damping elements adjacent to a perimeter of each of the plurality of blade platforms are positioned on a first side of the perimeter.

[0083] An engine as described in any of the preceding clauses, wherein a plurality of damping elements adjacent a perimeter of each of the plurality of blade platforms contact each other on a first side of the perimeter.

[0084] An engine as described in any preceding clause, wherein a plurality of fan blades are coupled to the disk in a spaced apart manner via a plurality of trunnions.

[0085] This written description uses examples to disclose the present disclosure, including the best mode, and also to enable any person skilled in the art to practice the present disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the present disclosure is defined by the claims, and may include other examples that occur to one skilled in the art. Such other examples are intended to fall within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that do not differ substantially from the literal language of the claims.

Claims

1. A variable pitch airfoil assembly for an engine, characterized in that: The variable pitch airfoil assembly comprises: a disk having an annular shape extending about an axial direction; an airfoil coupled to the disk via a platform, the airfoil extending outwardly from the disk in a radial direction and rotatable relative to the disk about a pitch axis; and A damping element is positioned at least partially within the disk, exterior to the platform and adjacent to a perimeter of the platform to provide vibration damping by friction between the damping element, the platform and the disk while also allowing for pitch variation of the airfoil.

2. The variable pitch airfoil assembly according to claim 1, wherein: Wherein the damping element is positioned within a recess of the disk adjacent to the periphery of the platform.

3. The variable pitch airfoil assembly according to claim 2, wherein: The damping element includes a first surface contacting an inner surface of the groove and a second surface contacting the platform.

4. The variable pitch airfoil assembly according to claim 3, characterized in that: The first surface of the damping element is flat, and the second surface is arc-shaped.

5. The variable pitch airfoil assembly according to claim 1, wherein: Further included is a plurality of damping elements positioned at least partially within the pan around the perimeter of the platform.

6. The variable pitch airfoil assembly according to claim 5, characterized in that: Wherein the plurality of damping elements are evenly spaced around the perimeter of the platform.

7. The variable pitch airfoil assembly according to claim 5, wherein: Wherein the plurality of damping elements are positioned on a first side of the perimeter of the platform.

8. The variable pitch airfoil assembly according to claim 7, wherein: Wherein the plurality of damping elements contact each other at the first side of the periphery of the platform.

9. The variable pitch airfoil assembly of claim 1, wherein: Further included is a plurality of airfoils coupled to the disk in a spaced-apart manner via a plurality of trunnions.

10. The variable pitch airfoil assembly of claim 1, wherein: The disk comprises a plurality of disk segments.

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