Variable pitch blade assembly including a lightning recovery system equipped with conductive fibers

Abstract

A variable-pitch turbine blade assembly (1) for an aircraft turbomachine, the assembly comprising a rotor (2) movably mounted about a radial axis (X) of the turbomachine, a stator (3) fixed about the radial axis (X), and at least one lightning recovery system (4). The lightning recovery system (4) comprises an electrically conductive bar (7) having an upper face fixed to the rotor (2) and a lower face, an assembly of electrically conductive fibers (8) fixed to said lower surface of the conductive bar (7), and a means (9) for attaching said lightning recovery system (4) to the rotor (2). Figure for the abstract: Fig 1

Description

Title of the invention: Variable pitch blade assembly comprising a lightning recovery system equipped with conductive fibers. Technical field

[0001] The invention relates to the dimensioning of a turbomachine in particular for the purpose of managing an impact produced by a lightning strike on a turbomachine.

[0002] The invention relates to a variable pitch blade turbomachine (also called a variable pitch blade turbomachine) comprising a rotor and a stator and in particular an unshrouded turbomachine in which the rotor includes a blade root rotating relative to the stator.

[0003] The blade of an unshrouded turbomachine is susceptible to being struck by lightning, unlike shrouded turbomachines which include a protective nacelle.

[0004] An unshrouded turbomachine must therefore include a lightning protection system. The lightning protection system creates a preferential short-circuit path for lightning. This prevents potentially dangerous structural damage to the turbomachine.

[0005] Today, lightning recovery systems equipping turbomachinery generally include an electrically conductive grounding braid comprising copper or aluminum cables. The grounding braid provides a secure path that rapidly dissipates the electrical current induced by lightning.

[0006] The grounding braid is connected at one end to the turbomachine rotor and at the other end to the turbomachine stator. If lightning strikes the turbomachine blade, the current induced by the lightning is directly transmitted through the grounding braid, which directs it towards the aircraft.

[0007] However, this solution is not optimal because the grounding braid induces significant frictional forces, particularly when the rotor is rotating relative to the turbomachine's stator. Furthermore, the braid is difficult to integrate into a locally congested environment such as the turbomachine's stator / rotor assembly. In addition, the lightning recovery system must include a grounding braid of sufficient length so that it can wrap around the rotor when it is in motion.

[0008] The aforementioned disadvantages cause architectural and space problems at the level of the turbine blades of the turbomachine. Description of the invention

[0009] The present invention aims to overcome the aforementioned problems and, in particular, to limit frictional forces and optimize the architecture within the turbomachine.

[0010] The invention therefore relates to a variable-pitch blade assembly for an aircraft turbomachine, the assembly comprising a rotor mounted movable about a radial axis of said turbomachine, a stator fixed about the radial axis, and at least one lightning recovery system. The lightning recovery system comprises an electrically conductive bar, including an upper face fixed to the rotor and a lower face, a set of electrically conductive fibers fixed to said lower surface of the conductive bar, and a means for attaching said lightning recovery system to the rotor.

[0011] Preferably, the conductive fibers of the electrically conductive fiber assembly extend towards the rotor so that the free end of the conductive fibers of the electrically conductive fiber assembly is in contact with the stator.

[0012] Advantageously, the rotor includes a blade foot and variable pitch blades fixed on the blade foot.

[0013] According to one embodiment, the rotor includes a blade foot comprising an upper surface and a lower surface on which the lightning recovery system is fixed.

[0014] Advantageously, the lightning recovery system includes a spring blade interposed between the conductive bar and the rotor.

[0015] According to one embodiment, the electrically conductive bar comprises an electrically conductive material.

[0016] Advantageously, the set of conductive fibers comprises an electrically conductive material.

[0017] According to one embodiment, the means for attaching said lightning recovery system to the rotor includes a bolt and / or a clip, and includes an electrically conductive material.

[0018] Advantageously, the lightning recovery system includes variable characteristics such as the dimensions of the conductive bar of said lightning recovery system and the dimensions, density and rigidity of the conductive fibers of said lightning recovery system.

[0019] According to one embodiment, the assembly comprises two lightning recovery systems distributed around the rotor.

[0020] The invention also relates to an unfaired turbomachine for aircraft comprising an assembly as defined above. Brief description of the drawings

[0021] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example and made with reference to the accompanying drawings in which:

[0022] - Figure [Fig. 1] is a schematic view of a variable pitch blade assembly including a lightning recovery system;

[0023] - Figure [Fig.2] is a schematic view from below of a pitched blade assembly variable including a lightning recovery system;

[0024] - Figure [Fig.3] is a schematic view of a lightning recovery system. Detailed description

[0025] Figure 1 shows a variable-pitch blade assembly of an unfaired aircraft turbomachine, the assembly being designated by the numerical reference 1. The assembly is in an orthonormal coordinate system X, Y, Z, in which the X axis designates a radial direction of the turbomachine, the Y axis designates a tangential direction of the turbomachine, and the Z axis designates a longitudinal direction of the turbomachine, oriented towards the top of the aircraft.

[0026] The assembly 1 comprises a main structure, a rotor 2 mounted movable relative to the radial axis X of the turbomachine, in particular movable in rotation about the radial axis X, a stator 3 fixed relative to the radial axis X of the turbomachine, in particular fixed in rotation about the radial axis X, and a lightning recovery system 4.

[0027] The rotor 2 comprises a blade root 2a, variable-pitch blades (not shown in the figures) fixed to the blade root 2a, and a pivot 2b that extends radially inward from the blade root 2a. The stator 3 surrounds the rotor 2; more specifically, the stator 3 circumferentially surrounds the pivot 2b of the rotor 2 and is fixed to the main structure of the turbomachine. The blade root 2a of the rotor 2 comprises an upper surface 5 and a lower surface 6.

[0028] As illustrated in the figures, the lightning recovery system 4 comprises an electrically conductive bar 7, an electrically conductive fiber assembly 8 and a means of attaching the lightning recovery system 4 to the rotor 2.

[0029] The electrically conductive bar 7 is a conductive plate comprising an electrically conductive material. It comprises an upper face and a lower face.

[0030] The electrically conductive fiber assembly 8 is fixed to the underside of the conductive bar 7, and extends radially inwards from the underside of the conductive bar 7, i.e. towards the stator 3, in particular such that the free end of the conductive fibers of the conductive fiber assembly 8 electricity is in contact with the stator 3. The assembly of conductive fibers 8 comprises an electrically conductive material, for example brass.

[0031] The dimensions of the conductive bar 7 vary depending on the current induced by the lightning. If the need for current recovery is high, the conductive bar 7 may have a large width 1 and length L, also increasing the quantity of conductive fibers 8 attached to the conductive bar 7.

[0032] The desired friction torque between the rotor 2 and the stator 3 is estimated in order to determine the characteristics of the conductive fibers 8, in particular their density within the lightning recovery system 4, their stiffness, and their height. In the embodiment illustrated in the figures, the desired friction torque within assembly 1 is less than or equal to five Newton-meters.

[0033] The thickness of the lightning recovery system 4 is also estimated as a function of the available space between the blade foot 2a and the stator 3. The lightning recovery system 4 as described includes a small radial footprint which is advantageous since the radial space available between the rotor 2 and the stator 3 is very limited.

[0034] The variable characteristics of the lightning recovery system 4 allow the solution to be optimized according to the available space in the variable pitch blade assembly 1 and the current to be recovered.

[0035] The fastening means 9 for the lightning recovery system 4 on the rotor 2 comprises, for example, a bolt positioned in the center of the conductive bar 7, as shown in [Fig. 2], or comprises two bolts positioned at the ends of the conductive bar 7, as shown in [Fig. 3]. The bolts advantageously comprise an electrically conductive material such as copper. Alternatively, the fastening means 9 for the lightning recovery system 4 on the rotor 2 may comprise a fastening clip and / or adhesive. The fastening means 9 further comprises an electrically conductive material. The fastening means 9 is easily removable for maintenance purposes on the lightning recovery system 4.

[0036] According to the embodiment illustrated in the figures, the lightning recovery system 4 is fixed under the blade foot 2a, in particular on the lower surface 6 of the blade foot 2a of the rotor 2 and is interposed between said blade foot 2a of the rotor 2 and the stator 3. The lightning recovery system 4 is positioned on the lower surface 6 of the blade foot 2a and extends along the length L of the conductive bar 7, the length L of the conductive bar extending here in a direction orthogonal to the axis of rotation of the rotor 2.

[0037] In the embodiment illustrated in the figures, the lightning recovery system 4 further comprises a spring blade 10 interposed between the bar conductive bar 7 and rotor 2, in particular interposed between the conductive bar 7 and the lower surface 6 of the blade foot 2a of rotor 2. The spring blade 10 creates a mechanical force imposing contact between the conductive bar 7 and the rotor 2 and also imposing contact between the conductive fibers 8 and the stator 3. The lightning recovery system 4 may include any type of spring element interposed between the conductive bar 7 and the rotor 2.

[0038] When lightning strikes the variable-pitch blade assembly 1, the lightning-induced current flows through the blade root 2a of the rotor 2 and is attracted by the conductive bar 7, passes through the conductive fibers 8, and travels to the stator 3. The current is then directed to the aircraft structure. The lightning recovery system 4 thus essentially comprises conductive materials to create a preferred path for the lightning-induced current.

[0039] Of course, the invention remains within the scope of the invention even if assembly 1 has a different composition. It is thus possible to design a lightning arrester system 4 comprising a conductive bar 7 of a different shape. It is also possible to consider that the lightning arrester system 4 is positioned at the pivot 2b of the rotor 2, interposed between said pivot 2b and the stator 3. Furthermore, a variable-pitch blade assembly 1 can comprise several lightning arrester systems 4 as described above, and in particular two lightning arrester systems 4 distributed around the rotor 2, specifically distributed circumferentially around the rotor 2.

[0040] Finally, a lightning recovery system 4 applies to any system comprising a part rotating with respect to a fixed part, said system being liable to be struck by lightning.

[0041] The lightning recovery system 4 provides electrical continuity between the rotor 2 and the stator 3 of a turbomachine without generating excessive friction in assembly 1. The lightning recovery system 4 is easy to manufacture and install and does not obstruct the turbomachine locally. Furthermore, the lightning recovery system 4 is easily accessible for maintenance on the turbomachine.

Claims

Demands

1. Assembly (1) of variable pitch blade for aircraft turbomachine, the assembly comprising a rotor (2) mounted movable about a radial axis (X) of said turbomachine, a stator (3) fixed about the radial axis (X) and at least one lightning recovery system (4), characterized in that the lightning recovery system (4) comprises an electrically conductive bar (7), comprising an upper face fixed to the rotor (2) and a lower face, an assembly of electrically conductive fibers (8) fixed to said lower surface of the conductive bar (7) and a means of fixing said lightning recovery system (4) to the rotor (2).

2. Assembly (1) according to claim 1, wherein the rotor (2) comprises a blade foot (2a) and variable pitch blades fixed on the blade foot (2a).

3. Assembly (1) according to any one of claims 1 and 2, wherein the rotor (2) comprises a blade foot (2a) comprising an upper surface (5) and a lower surface (6) on which the lightning recovery system (4) is fixed.

4. Assembly (1) according to any one of claims 1 to 3, wherein the lightning recovery system (4) comprises a spring blade (10) interposed between the conductive bar (7) and the rotor (2).

5. Assembly (1) according to any one of claims 1 to 4, wherein the electrically conductive bar (7) comprises an electrically conductive material.

6. Assembly (1) according to any one of claims 1 to 5, wherein the assembly of conductive fibers (8) comprises an electrically conductive material.

7. Assembly (1) according to any one of claims 1 to 6, wherein the means for attaching (9) said lightning recovery system (4) to the rotor (2) comprises a bolt and / or a clip, and comprises an electrically conductive material.

8. Assembly (1) according to any one of claims 1 to 7, wherein the lightning recovery system (4) comprises variable features such as the dimensions of the conductive bar (7) of said lightning recovery system (4) and the dimensions, density and stiffness of the conductive fibers (8) of said lightning recovery system (4).

9. Assembly (1) according to any one of claims 1 to 8, comprising two lightning recovery systems (4) distributed around the rotor (2).

10. Unfaired aircraft turbomachine, comprising an assembly (1) according to any one of claims 1 to 9.

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