Variable pitch vanes for stationary vane assemblies of turbine engines

Abstract

The invention relates to a variable-pitch blade (13) comprising a blade root (21), a fastener (23) supporting the blade root (21), and a hub (25), wherein the blade root (21), the fastener (23) and the hub (25) are configured to be pivotably mounted about a pitch axis Y of the blade (13), wherein the fastener (23) is coupled to the hub (25) by a torque transmission system (29) configured to transmit a torque between the hub (25) and the fastener (23) by friction and to enable a relative pivoting of the fastener (23) and the hub (25) about the pitch axis Y when the transmitted torque exceeds a given value. The invention also relates to a static blade assembly (11) comprising at least one such blade (13), to a turbomachine (1) comprising at least one such static blade assembly (11), to an aircraft (100) comprising at least one such turbomachine (1).

Description

Technical Field

[0001] This application relates to the field of turbines. In particular, it relates to a variable-pitch blade of a static blade assembly of a turbine, especially a non-ducted straightener for a turbine including at least one such blade, a turbine including at least one such static blade assembly, and an aircraft including at least one such turbine. The invention is particularly applicable to non-ducted straighteners for turbines. Background Technology

[0002] A turbine that includes at least one non-ducted propeller is referred to as an open rotor, propeller fan, or non-ducted fan. Such a turbine may include two non-ducted, counter-rotating propellers (counter-rotating open rotor, CROR) or a single non-ducted propeller (non-ducted single fan) and a straightener formed by a static blade assembly, the blades of which are called outlet guide vanes (OGVs), positioned downstream of the non-ducted propeller. This straightener functions to straighten the aerodynamic flow at the turbine's propeller outlet. The propeller may be positioned behind the gas generator (or engine) to make the gas generator a pusher type, or positioned in front of the gas generator to make it a puller type. These turbines are turboprops, which differ from turbojet engines in that they use an external propeller (non-ducted) instead of an internal fan. This allows for a very significant increase in bypass ratio, unaffected by the mass of the casing or nacelle designed to surround the blades of the propeller or fan.

[0003] Straightener blades are typically mounted on a casing that supports a splitter, which separates the main airflow through the primary air path from the main and secondary airflows flowing around the inlet casing. Unlike the upstream propeller of a non-ducted single-fan (USF) turbine, the straightener blades are fixed in rotation relative to the axis of rotation of the upstream propeller.

[0004] Advantageously, the blades of the static blade assembly have variable pitch. For this purpose, each stator blade can be pivotally mounted along the pitch axis, and the root of each blade is connected to a pitch-changing system installed in the turbine. Therefore, the variable-pitch blades can pivot during turbine operation. The integrated area of ​​the blade's pivot and root is severely limited due to the presence of numerous components surrounding the pivot and root.

[0005] Furthermore, in such turbines where mass savings are desired, the variable-pitch blades are preferably made of composite materials comprising fiber reinforcements embedded in an organic matrix. Therefore, in recent turbines, large-sized blade assemblies are increasingly made of organic matrix composites because these materials result in significant mass savings at the same mechanical performance, or significant mechanical savings at the same mass, or both. The blades of such assemblies are manufactured, for example, through two-dimensional layering of fiber reinforcements subsequently densified with resin, or more recently, through three-dimensional weaving of subsequently densified individual preforms.

[0006] In the design and manufacture of composite blade assemblies, it is necessary to consider the drag of the blade assembly on incoming air. Certification requirements for bird strike risk vary depending on the turbine size, particularly the diameter of the fan or propeller. These requirements specify the impact conditions, which represent the ejection mass of a bird striking the blade assembly at a certain velocity (corresponding to the aircraft's forward velocity at the time of impact). In some cases, limited damage may be permissible, allowing the aircraft to continue its mission or flight without problems, or to land on the tarmac for repairs. In all cases, the safety of passengers, crew, and crowded areas must be guaranteed. Therefore, while these requirements are restrictive, they are absolutely necessary.

[0007] In cases of acceptable damage, such damage must be definitively identified during ground control checks. The damage may be located within aerodynamic components (within the air path area) or at fasteners (below the air path). Components below the air path are concealed by the platform, which reconfigures the air path to improve turbine aerodynamics. Therefore, this component of the blade assembly is not visible without disassembly.

[0008] In conventional ducted airframe architectures, current designs of rotating blade assemblies do not allow for any damage at the blade root before blade failure. Therefore, failure primarily occurs in the airfoil, i.e., in the visible aerodynamic components, which addresses the problem of controlling blade damage.

[0009] However, due to aerodynamic volume, manufacturing tolerances (minimum thickness), and the properties of the materials used, blades (whether rotating (fan blades, propeller blades) or static (OGV) blades) can be designed to have inherently high drag in their airfoil-forming components and inherently low drag in their root-forming components, which are located below the air path and are therefore invisible unless disassembled. For example, the low drag of the root-forming components is caused by the shape imposed by external requirements (such as assembly and disassembly constraints or external interface constraints), available volume (creating integration constraints), and the dimensions and properties of the materials used (manufacturing constraints).

[0010] In this case, the critical area (i.e., the area that may be damaged during intake) is located outside the aerodynamic air path and therefore in an area that is not visible unless disassembly is performed. However, such disassembly is not easy and therefore cannot be carried out regularly, for example, during ground control inspection operations.

[0011] Document FR3132126A1 specifically discloses an aircraft engine including blades attached to a housing. Document US7112040B2 specifically discloses a device for guiding blades having a variable pitch angle. Document US2023 / 257105A1 specifically discloses a system for controlling the angular pitch of propeller blades for an aircraft turbine. Document US4047840A specifically discloses an airfoil support for absorbing shock for an airfoil with a variable pitch angle. Document US2017 / 313404A1 specifically discloses a propeller for an aircraft turbine including a device for adjusting the pitch of the airfoil's angle of incidence. Summary of the Invention

[0012] One objective of this application is to overcome the aforementioned disadvantages by providing a variable pitch blade for a static blade assembly of a turbine, which aims to prevent blade failure outside the aerodynamic air path under intake conditions, while simplifying control and inspection operations.

[0013] Therefore, according to a first aspect, the present invention provides a variable pitch blade for a static blade assembly of a turbine, the blade including a blade root, fasteners supporting the blade root, and a hub. The blade root, fasteners, and hub are configured to be pivotally mounted around the blade's pitch axis. The fastener is connected to the hub via a torque transmission system configured to transmit torque between the hub and the fastener through friction, and configured to allow the fastener and the hub to pivot relative to each other about the pitch axis when the torque transmitted by the torque transmission system exceeds a given value.

[0014] Therefore, by introducing this torque transmission system between the fastener and the hub, the transmission of rotational force relative to the pitch axis is ensured through friction (i.e., through frictional contact). The maximum transmittable torque can be adjusted so that, under an energy intake level, the fastener and hub pivot relative to each other (in other words, slide relative to each other), an energy level that could potentially damage the blade assembly in an invisible area (more precisely, below the air path). In other words, the torque that can be transmitted between the fastener and the hub is limited to a given value by the torque transmission system. Therefore, the magnitude of the torque transmitted by friction can be determined, particularly for such high energy intake conditions. Furthermore, due to the torque transmission system, for example, under intake conditions, the energy generated by the impact of external components with the blade can be at least partially dissipated. Moreover, the relative pivoting of the fastener and hub about the pitch axis allows potential damage to be detected without needing to remove the blade from the static blade assembly after intake.

[0015] According to a second aspect, the present invention provides a static impeller assembly for a turbine, the static impeller assembly including at least one impeller according to a first aspect.

[0016] According to a third aspect, the present invention provides a turbine that includes a static blade assembly according to a second aspect.

[0017] According to the fourth aspect, an aircraft is provided, which includes at least one turbine according to the third aspect.

[0018] Advantageously and optionally, the invention is accomplished by employing features individually or in any combination thereof that is technically possible: The hub is configured to be rotated by the actuation mechanism of the static blade assembly. Thus, the blade pitch is simply achieved.

[0019] - The blade root is attached to a fastener.

[0020] - The blade root, fasteners, and hub can be pivotally mounted around the blade's pitch axis.

[0021] - The blade includes an airfoil that extends longitudinally from the blade root along the pitch axis.

[0022] -The static impeller assembly is a non-ducted straightener.

[0023] - The static impeller assembly includes a housing.

[0024] - The hub can be pivotally mounted on the housing of the static blade assembly around the pitch axis.

[0025] At least one bearing is arranged between the housing and the hub of the static impeller assembly. This ensures simple and reliable pivoting of the hub relative to the housing.

[0026] - The pitch axis is the radial axis of the housing of the static blade assembly.

[0027] The housing of the static impeller assembly includes at least one air path panel. This improves the aerodynamics of the static impeller assembly.

[0028] - The airfoil extends through the air path of the static impeller assembly.

[0029] - The torque transmission system is reversible. Therefore, torque can be transmitted not only from the hub to the fastener, but also from the fastener to the hub.

[0030] - The static blade assembly includes an actuation mechanism, which rotatably actuates the hub. Therefore, the static blade assembly includes an actuation mechanism that enables the pitch angle of the blades of the blade assembly to be changed, so that the engine performance can be adapted to different flight phases.

[0031] The torque transmission system includes an axial clamping member along the pitch axis, which axially clamps the fastener and hub together. Therefore, a given value can be easily adjusted. In other words, the maximum transmittable torque can be adjusted via the axial clamping member.

[0032] - The axial clamping component achieves axial clamping by tightening with threads. Therefore, axial clamping is accomplished simply and reliably.

[0033] - The axial clamping component includes screws. Therefore, axial clamping is accomplished simply and reliably.

[0034] - The screw extends axially along the pitch axis.

[0035] - The screw passes through the hub, preferably through the through hole, and is screwed into the fastener. Thus, axial clamping is accomplished in a particularly simple and reliable manner.

[0036] - The screw passes through the fastener, preferably through the through hole, and is screwed into the hub. Thus, axial clamping is accomplished in a particularly simple and reliable manner.

[0037] - The axial clamping component includes a spring washer. Therefore, the given value can be adjusted simply and reliably.

[0038] - The given value depends on the axial clamping of the axial clamping member.

[0039] - The torque transmission system is formed by at least one surface of a fastener and at least one surface of a hub, the at least one surface of the fastener and at least one surface of the hub being in frictional contact to transmit torque between the hub and the fastener by friction. Thus, the transmission by friction is simply accomplished.

[0040] - The torque transmission system includes at least one friction lining. Therefore, the transmittable torque can be increased.

[0041] - One end of the fastener is truncated conical and is housed in the truncated conical portion of the hub.

[0042] - The truncated conical surface at the end of the fastener is in frictional contact with the truncated conical surface of the truncated conical mounting portion to transmit torque between the hub and the fastener through friction. Therefore, the torque transmission system is implemented in a particularly simple manner.

[0043] - The truncated conical end of the fastener is located away from the blade root and is shaped to widen in the direction of the blade root. This simplifies the mounting of the blade on the static blade assembly.

[0044] The truncated conical shape of the hub is shaped to widen in the direction of the blade root. This simplifies the mounting of the blade on the static blade assembly.

[0045] - The end of the fastener is truncated conical along the pitch axis.

[0046] - The housing of the hub is truncated conical along the pitch axis.

[0047] - The torque transmission system includes at least one first fastener disc and at least one second hub disc.

[0048] - Each first fastener disc and fastener forms a sliding connection with each other along the pitch axis.

[0049] - Each second hub disc and hub forms a sliding connection with each other along the pitch axis.

[0050] At least one first fastener disc and at least one second hub disc are in frictional contact with each other to transmit torque between the hub and the fastener via friction. Therefore, the torque transmission system is particularly compact.

[0051] Each first fastener disc and each second hub disc are stacked alternately along the pitch axis. This increases the transmittable torque while limiting the size of the torque transmission system.

[0052] Friction linings are arranged on at least one element selected from a group consisting of a fastener, a hub, at least one first fastener disc, and at least one hub disc. Therefore, the transmittable torque can be increased.

[0053] The fastener includes a first angular stop, and the hub includes a second angular stop. In the absence of any angular offset between the fastener and the hub caused by relative pivoting of the fastener and hub about the pitch axis (and therefore relative pivoting of the blades), the first and second angular stops are angularly offset about the pitch axis by a given value. Such excessive pivoting can disrupt the overall aerodynamics of the turbine or excessively increase the forces borne by the static blade assembly.

[0054] When a given angular offset exists between the fastener and the hub, the first angular stop and the second angular stop contact each other. Thus, the adjustment of the restriction on the relative pivoting between the fastener and the hub is simply accomplished.

[0055] - The fastener includes a notch. Therefore, the adjustment of the restriction on the relative pivoting between the fastener and the hub is made particularly simple.

[0056] - Each end of the notch forms a first angular stop. Therefore, the adjustment of the restriction on the relative pivoting of the fastener and the hub is accomplished particularly simply.

[0057] The hub includes a pin that inserts into a recess in the fastener. This allows for particularly simple adjustment of the relative pivoting limits between the fastener and the hub.

[0058] - The pin forms a second angle stop. Therefore, the adjustment of the restriction on the relative pivoting between the fastener and the hub is achieved particularly simply.

[0059] The blade includes a visual indicator that indicates an angular offset between the fastener and the hub caused by the relative pivoting of the fastener and hub about the pitch axis. Therefore, especially when the aircraft is on the ground, this visual indicator makes it easy to detect pitch changes in the blade, such as a few degrees, caused by the relative pivoting of the fastener and hub about the pitch axis.

[0060] The visual indicator includes a first indicating element fixed relative to a fastener and a second indicating element fixed relative to the housing of the static impeller assembly. Thus, the visual indicator is implemented simply.

[0061] - The first indicating element is arranged on a platform attached to the root of the impeller. Therefore, visual inspection can be easily performed, especially on the ground.

[0062] - A second indicating element is arranged on the air path panel of the static impeller assembly housing. Therefore, visual inspection can be easily performed, especially on the ground.

[0063] -Given a given pitch angle of the blade, the first indicating element aligns with the second indicating element provided there is no angular offset between the fastener and the hub caused by relative pivoting of the fastener and hub around the pitch axis. Therefore, detecting the absence of pitch variation in the blade is particularly simple.

[0064] A given angular pitch of the blade corresponds to the blade pitch when the turbine is stopped. This simplifies detection on the ground.

[0065] - The turbine also includes a ducted fan or a non-ducted propeller, a compressor section and a turbine section, and the static blade assembly is at least one of the following blade assemblies: a ducted straightener for the fan, a non-ducted straightener for the propeller, a straightener for the compressor section, and a nozzle guide blade for the turbine section. Attached Figure Description

[0066] Other features, objects, and advantages of the invention will become apparent from the following detailed description, which is entirely illustrative and non-limiting and must be read with reference to the accompanying drawings, given as a non-limiting example, in which: [ Figure 1 [Illustration] is a schematic diagram of an example of an aircraft including at least one turbine according to an embodiment; [ Figure 2 [Illustration] is a partial axial cross-sectional view of an example of a USF-type turbine according to an embodiment, which includes a single non-ducted propeller and a fixed blade assembly (e.g., a non-ducted straightener) including at least one blade; [ Figure 3 [Illustrated cross-sectional view of an exemplary embodiment of the blade according to the first embodiment;] [ Figure 4 [Illustrated cross-sectional view of an exemplary embodiment of a modified impeller according to the first embodiment;] [ Figure 5 Two schematic partial top views of an exemplary embodiment of a static blade assembly including at least one blade, according to a variation of the first embodiment, are shown, wherein the blade is in two different operating modes; [ Figure 6 [Illustrated cross-sectional view of an exemplary embodiment of the blade according to the second embodiment.]

[0067] In all the accompanying drawings, similar elements are referred to by the same reference numerals. Detailed Implementation

[0068] Figure 1 An aircraft 100 is shown, which includes at least one turbine 1, and in this example includes two turbines 1. Each turbine 1 can be mounted on the aircraft 100 via a pylon.

[0069] like Figure 2 As shown, at least one turbine 1 typically includes at least one fan or at least one propeller 3, a compressor section 5, a combustion chamber 7, a turbine section 9 located downstream of the combustion chamber 7, and an exhaust casing. Furthermore, at least one turbine 1 includes at least one static (i.e., non-rotating) blade assembly 11, whether this static blade assembly 11 is a static blade assembly 11 forming a straightener of the fan or propeller 3, a static blade assembly forming a straightener 11 of the compressor section 5, or a static blade assembly 11 forming a nozzle guide blade of the turbine section 9.

[0070] As an example, such as Figure 2 As shown, turbine 1 is a USF-type turboprop including a non-ducted propeller 3, in which case the static blade assembly 11 is a non-ducted straightener and extends downstream of propeller 3. In another example, turbine 1 may be a turbojet engine including a ducted fan, in which case the static blade assembly 11 corresponds to a ducted straightener extending downstream of the fan.

[0071] In this application, upstream and downstream are defined relative to the flow direction of gas through the static impeller assembly 11. The term "axis X" refers to the axis of rotation of the rotor of the propeller 3 (or fan). The axial direction corresponds to the direction of axis X, and the radial direction is the direction orthogonal to and through axis X. Furthermore, the circumferential (or tangential) circumferential direction corresponds to the direction orthogonal to axis X but does not pass through axis X. Unless otherwise stated, "inner" and "outer" are used with reference to the radial direction, such that the inner part or inner surface of the element is closer to axis X than the outer part or outer surface of the same element.

[0072] Therefore, the static blade assembly 11 includes one or more blades 13. The static blade assembly 11 also includes a housing 15 fixedly mounted relative to the housing 17 of the turbine 1. Therefore, the static blade assembly 2 is non-rotating. Each blade 13 of the static blade assembly 11 extends substantially radially relative to the axis X.

[0073] Therefore, the impeller 13 is defined relative to the axis X of the rotor associated with the static impeller assembly 11 (whether the axis X is the axis of rotation of the fan or propeller 3 for the fan straightener, the axis of rotation of the compressor rotor for the compressor section 5 straightener, or the axis of rotation of the turbine rotor for the turbine section 9 nozzle guide impeller (the rotor is intended to be mounted on the turbine section 9 nozzle guide impeller)).

[0074] Blade 13 is a variable-pitch blade. Therefore, blade 13 is pivotally mounted on the static blade assembly 11 about the pitch axis Y. Therefore, the static blade assembly 11 includes an actuation mechanism 19 that enables the pitch angle of blade 13 of the static blade assembly 11 to be changed so that the performance of the turbine 1 can be adapted to different flight phases.

[0075] exist Figure 3 In the first embodiment shown, the blade 13 includes a blade root 21, a fastener 23, and a hub 25. The blade root 21, fastener 23, and hub 25 are configured to be pivotally mounted about the pitch axis Y of the blade 13. In this example, the blade root 21, fastener 23, and hub 25 are pivotally mounted about the pitch axis Y of the blade 13. Therefore, the hub 25 can be pivotally mounted about the pitch axis Y on the housing 15 of the static blade assembly 11.

[0076] The blade 13 also includes an airfoil 27 that extends longitudinally from the blade root 21 along the pitch axis Y. Thus, for example, the pitch axis Y is the radial axis of the housing 15 of the static blade assembly 11. In other words, the pitch axis Y extends radially relative to the axis X. The airfoil 27 has an aerodynamic profile and is arranged in the airflow during turbine 1 operation. Therefore, the airfoil 27 extends through the air path of the static blade assembly 11. For example, the airfoil 27 and the blade root 21 are integrally formed from a composite material comprising fiber reinforcements densified from a polymer matrix, such as glass fibers.

[0077] Fastener 23 supports the blade root 21. In other words, the blade root 21 is attached to fastener 23. Fastener 23 is connected to hub 25 via torque transmission system 29.

[0078] The hub 25 is rotatably mounted relative to the housing 17 of the static blade assembly 11. For this purpose, at least one bearing 31 is arranged between the housing 17 of the static blade assembly 11 and the hub 25. In this example, two bearings 31 are arranged between the housing 17 of the static blade assembly 11 and the hub 25. The hub 25 is configured to be rotatably actuated by the actuation mechanism 19 of the static blade assembly 11. Therefore, this rotational actuation allows for adjustment of the pitch angle of the blades 13. Thus, the hub 25 is rotatably actuated by the actuation mechanism 19.

[0079] The torque transmission system 29 is configured to transmit torque between the hub 25 and the fastener 23 via friction. The torque transmission system 29 is reversible. Therefore, torque can be transmitted not only from the hub 25 to the fastener 23, but also from the fastener 23 to the hub 25. Thus, the pitch of the blade 13 is achieved in all phases of normal aircraft operation, particularly in different flight phases.

[0080] The torque transmission system 29 is also configured to allow the fastener 23 and hub 25 to pivot relative to each other about the pitch axis Y. This pivoting is thus made possible when the torque transmitted by the torque transmission system 29 exceeds a given value. The given maximum value is adjusted such that the fastener and hub pivot relative to each other during an energy level intake that could potentially damage the blade 13 or, more generally, the static blade assembly 11 in an invisible region (more precisely, below the air path).

[0081] The torque transmission system 29 includes an axial clamping member 33 along the pitch axis Y. The axial clamping member 33 axially clamps the fastener 23 and the hub 25 together. For example, the axial clamping member 33 is axially clamped by threaded tightening. For example, the axial clamping member 33 includes a screw and a spring washer. In this example, the screw extends axially along the pitch axis Y. In a first possibility of this example, the screw passes through the hub 25, preferably through a through-hole, and is screwed into the fastener 23. In a second possibility of this example, the screw passes through the fastener 23, preferably through a through-hole, and is screwed into the hub 25. In a third possibility of this example, the clamping member 33 is attached to the hub 25, for example, in the case of a screw in the clamping member 33, the pair (screw, hub 25) is integral, and the screw is screwed into the fastener 23. In the fourth possibility of this example, the clamping member 33 is attached to the fastener 23, for example, in the case of a screw in the fastener 23, the pair (screw, fastener 23) are integral, and the screw is screwed into the hub 25.

[0082] In this example, the given value depends on the axial clamping of the axial clamping member 33. Therefore, the given value can be easily adjusted by the clamping performed by the axial clamping member 33.

[0083] The torque transmission system 29 is also formed by at least one surface SA of the fastener 23 and at least one surface SM of the hub 25, the at least one surface SA of the fastener 23 and at least one surface SM of the hub 25 being in frictional contact to transmit torque between the hub 25 and the fastener 23 by friction.

[0084] Optionally, the torque transmission system 29 includes at least one friction lining. For example, the friction lining is disposed on the surface SA of the fastener 23 and / or the surface SM of the hub 25.

[0085] In this example, one end 35 of the fastener 23 is truncated conical and is received in the truncated conical housing 37 of the hub 25. The end 35 of the fastener 23 is truncated conical along the pitch axis Y, and the housing 37 of the hub 25 is also truncated conical along the pitch axis Y. The truncated conical end 35 of the fastener 23 is located away from the blade root 21 and is shaped to widen in the direction of the blade root 21. Similarly, the truncated conical housing 37 of the hub 25 is shaped to widen in the direction of the blade root 21. To enable torque transmission via friction, surface SA is the truncated conical surface of the end 35 of the fastener 23, and surface SM is the truncated conical surface of the truncated conical housing 37. Therefore, surface SA and surface SM are in frictional contact to transmit torque between the hub 25 and the fastener 23 via friction.

[0086] according to Figure 4 In a variation of the first embodiment shown, fastener 23 includes a first angular stop 39, and hub 25 includes a second angular stop 41. In the absence of any angular offset between fastener 23 and hub 25 caused by relative pivoting about the pitch axis Y, the first angular stop 39 and the second angular stop 41 are angularly offset about the pitch axis Y by a given value.

[0087] When the torque transmitted by the torque transmission system 29 exceeds a given value, relative pivoting occurs between the fastener 23 and the hub 25 about the pitch axis Y. In this case, the first angle stop 39 and the second angle stop 41 pivot relative to each other, and when there is a given angular offset between the fastener 23 and the hub 25, the first angle stop 39 and the second angle stop 41 contact each other.

[0088] In this example, fastener 23 includes a notch 43. Therefore, each angular end of the notch 43 forms a first angular stop 39. Hub 23 includes a pin 45 that inserts into the notch 43 of fastener 23. Therefore, pin 45 forms a second angular stop 41.

[0089] according to Figure 5 In another variation of the first embodiment shown, the blade 13 includes a visual indicator 47. This visual indicator 47 indicates an angular offset between the fastener 23 and the hub 25 caused by the relative pivoting of the fastener 23 and the hub 25 about the pitch axis Y.

[0090] For this purpose, the visual indicator 47 includes a first indicator element 49 fixed relative to the fastener 23 and a second indicator element 51 fixed relative to the housing 15 of the static wheel assembly 11.

[0091] For example and such Figure 5As shown in the left view, at a given pitch angle of blade 13, without any angular offset between fastener 23 and hub 25 caused by relative pivoting about the pitch axis Y, the first indicating element 49 is aligned with the second indicating element 51. In this example, the given angular offset of blade 13 corresponds to the pitch of blade 13 when turbine 1 is stopped. Therefore, the second indicating element 51 forms a visual reference. Figure 5 As shown in the right-hand view, during the relative pivoting of the fastener 23 and hub 25 about the pitch axis Y, such as after intake, this visual reference can easily make the offset relative to the first indicator element 49 visible.

[0092] For example, a first indicating element 49 is disposed on a platform 53 attached to the blade root 21. In this example, the platform 53 has a circular outer periphery. For example, the housing 15 of the static blade assembly 11 includes at least one air path panel 55 on which a second indicating element 51 is disposed. In this example, the platform 53 is flush with the air path panel 55.

[0093] Figure 6 A blade 13 according to a second embodiment is schematically shown. This blade 13 according to the second embodiment is similar to the blade 13 previously described in the first embodiment, with similar elements designated by the same reference numerals. However, the main difference between the blade 13 according to the second embodiment and the blade 13 previously described in the first embodiment is that the torque transmission system 29 includes at least one first fastener disc 57 and at least one second hub disc 59. Therefore, the at least one first fastener disc 57 and the at least one second hub disc 59 are in frictional contact with each other to transmit torque between the hub 25 and the fastener 23 through friction.

[0094] On one hand, each first fastener disc 57 and fastener 23 is slidably connected to each other along the pitch axis Y. For example, fastener 23 has a T-shaped longitudinal section along the pitch axis Y, and each first fastener disc 57 can slide in the T-shaped base forming the fastener 23. Additionally, each second hub disc 59 and hub 25 is slidably connected to each other along the pitch axis Y. For example, the slidable connection between the two elements is achieved by the ribs of the first element engaging in the recesses of the second element, and can slide along the pitch axis Y.

[0095] In this example, the torque transmission system 29 includes two to six first fastener discs 57, preferably four, and the torque transmission system 29 includes two to six second hub discs 59, preferably four. Each first fastener disc 57 and each second hub disc 59 are stacked alternately on top of each other along the pitch axis Y.

[0096] In this example, the axial clamping member 33 axially clamps the fastener 23 and the hub 25 together via an end disc 61. The end disc 61 is housed in the hub 25 and spaced a distance from the fastener 23 along the pitch axis Y. The end disc 61 contacts the second hub disc 59, preferably in frictional contact. In this example, the hub 25 includes a disc-shaped end 63 inserted between the fastener 23 and the first fastener disc 57. Thus, the hub 25, at least one first fastener disc 57, and at least one second hub disc 59 are axially compressed between the fastener 23 and the end disc 61 by the axial clamping member 33.

[0097] Optionally, the torque transmission system 29 includes at least one friction lining. For example, the friction lining is disposed on at least one element selected from the group consisting of fastener 23, hub 25, at least one first fastener disc 57, and at least one hub disc 59.

[0098] Variations of the first embodiment, and variations of the first and second embodiments, can be combined with each other in any technically possible combination.

Claims

1. A variable pitch blade (13) of a static blade assembly (11) of a turbine (1), the variable pitch blade (13) comprising: The root of the wheel blade (21), Fasteners (23) supporting the root (21) of the blade, and Hub (25) The blade root (21), the fastener (23), and the hub (25) are configured to be pivotally mounted about the pitch axis (Y) of the variable pitch blade (13). The fastener (23) is connected to the hub (25) via a torque transmission system (29), the torque transmission system (29) being configured to transmit torque between the hub (25) and the fastener (23) by friction, and being configured to allow the fastener (23) and the hub (25) to pivot relative to each other about the pitch axis (Y) when the torque transmitted by the torque transmission system (29) exceeds a given value.

2. The variable pitch blade (13) according to claim 1, wherein, The torque transmission system (29) includes an axial clamping member (33) along the pitch axis (Y) that axially clamps the fastener (23) and the hub (25) together.

3. The variable pitch blade (13) according to claim 1, wherein, The torque transmission system (29) is formed by at least one surface (SA) of the fastener (23) and at least one surface (SM) of the hub (25), the at least one surface of the fastener and at least one surface of the hub being in frictional contact to transmit torque between the hub (25) and the fastener (23) by friction.

4. The variable pitch blade (13) according to claim 3, wherein, One end (35) of the fastener (23) is truncated conical and is housed in the truncated conical portion (37) of the hub (25). The truncated conical surface (SM) of the end (35) of the fastener (23) is in frictional contact with the truncated conical surface (SA) of the truncated conical portion (37) to transmit torque between the hub (25) and the fastener (23) by friction.

5. The variable pitch blade (13) according to claim 1, wherein, The torque transmission system (29) includes at least one first fastener disc (57) and at least one second hub disc (59), each first fastener disc (57) and the fastener (23) being slidably connected to each other along the pitch axis (Y), and each second hub disc (59) and the hub (25) being slidably connected to each other along the pitch axis (Y). At least one first fastener disc (57) and at least one second hub disc (59) are in frictional contact with each other to transmit torque between the hub (25) and the fastener (23) by friction.

6. The variable pitch blade (13) according to claim 1, wherein, The fastener (23) includes a first angle stop (39), and the hub (25) includes a second angle stop (41), wherein, in the absence of any angular offset between the fastener (23) and the hub (25) caused by the relative pivoting of the fastener (23) and the hub (25) about the pitch axis (Y), the first angle stop (39) and the second angle stop (41) are angularly offset about the pitch axis (Y) by a given value.

7. The variable pitch blade (13) according to claim 1, wherein, The variable pitch blade includes a visual indicator (47) that indicates an angular offset between the fastener (23) and the hub (25) caused by the relative pivoting of the fastener (23) and the hub (25) about the pitch axis (Y).

8. A static blade assembly (11) of a turbine (1), said static blade assembly comprising at least one variable pitch blade (13) according to any one of claims 1 to 7, wherein, The blade root (21), the fastener (23) and the hub (25) can be pivotally mounted around the pitch axis (Y) of the variable pitch blade (13).

9. A turbine (1) comprising at least one static blade assembly (11) according to claim 8.

10. An aircraft (100) comprising at least one turbine (1) according to claim 9.

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