Variable-pitch blade assembly for a turbine engine comprising a lightning protection system

Abstract

The invention relates to a variable-pitch blade assembly (1) for an open-rotor turbine engine of an aircraft, the assembly comprising: a rotor (3) which is movable relative to a radial axis (X) of the turbine engine; a stator (4) which is stationary relative to the radial axis (X); and at least one lightning protection system (5). The lightning protection system (5) comprises: a pin (6), at least one face of the pin (6) being in frictional contact with the rotor (3); a screw (7) which radially extends the pin (6); and a means (8) for connecting the pin (6) and the screw (7), the connecting means (8) comprising a spring inserted between the pin (6) and the screw (7).

Description

[0001] DESCRIPTION

[0002] Variable pitch blade assembly for turbomachinery including a lightning protection system

[0003] technical field

[0004] The invention relates to the dimensioning of a turbomachine in particular for the purpose of managing a lightning strike on a turbomachine.

[0005] The invention relates to a variable-pitch bladed 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.

[0006] The blade of an unshod turbomachine is susceptible to being struck by lightning, unlike shod turbomachines which include a protective nacelle.

[0007] An unshrouded turbomachine must therefore include a lightning protection system with a grounding connection for the recovered current. This lightning protection system creates a preferential short-circuit path for lightning, thus preventing potentially dangerous structural damage to the turbomachine.

[0008] Today, lightning grounding systems on turbomachinery typically include an electrically conductive braid made of copper or aluminum cables. This braid provides a secure path that quickly dissipates the electrical current induced by lightning.

[0009] The braid is connected at one end to the turbomachine rotor and at the other end to the turbomachine stator. If lightning strikes the turbomachine blades, the resulting current is directly transmitted through the braid, which directs it towards the aircraft. However, this solution is not optimal because the braid induces significant friction, particularly when the rotor is rotating relative to the turbomachine 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 protection system must include a sufficiently long braid to allow it to be wrapped around the rotor while it is in motion.

[0010] The aforementioned disadvantages lead to problems with the architecture and space requirements of the turbomachine blades.

[0011] Description of the invention

[0012] The present invention aims to overcome the aforementioned problems and, in particular, to limit frictional forces and optimize the architecture within the turbomachine.

[0013] The invention therefore relates to a blade assembly, in particular a variable pitch blade for an unfaired turbomachine, the assembly comprising a rotor movable relative to a radial axis of the turbomachine, a stator fixed relative to the radial axis and at least one lightning recovery system.

[0014] The lightning recovery system includes a pin, at least one face of said pin being in contact by friction with the rotor, a screw extending radially from said pin and a means of connecting the pin and the screw, said connecting means comprising a spring interposed between the pin and the screw.

[0015] Advantageously, the rotor includes a blade foot and variable pitch blades fixed to the blade foot.

[0016] In one embodiment, the screw of the lightning recovery system passes through the stator along a longitudinal axis of the turbomachine, and the pin is in contact with the outer lateral surface of the rotor. Advantageously, the outer lateral surface of the rotor includes a radial groove into which the pin is inserted.

[0017] According to one embodiment, the pawn contains graphite.

[0018] Advantageously, at least the face of the pin in contact with the rotor has a coating comprising a low coefficient of friction.

[0019] According to one embodiment, the screw includes a thread into which the spring and part of the pin are inserted.

[0020] Advantageously, the face of the pin in contact with the rotor includes a concave profile conforming to the shape of the rotor.

[0021] According to one embodiment, the assembly comprises two lightning recovery systems distributed radially around the rotor.

[0022] The invention also relates to an unfaired turbomachine comprising an assembly as defined above.

[0023] Brief description of the drawings

[0024] 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:

[0025] - Figure [Fig 1] is a schematic view of a variable pitch blade assembly including a lightning recovery system;

[0026] - Figure [Fig 2] is a schematic view of a lightning recovery system;

[0027] - Figure [Fig 3] is a schematic top view of a variable pitch blade assembly including a lightning recovery system.

[0028] Detailed description Figure 1 shows an assembly of variable pitch blades of an aircraft turbomachine, the assembly being designated by the numerical reference 1. The assembly is inscribed in an orthonormal coordinate system X, Y, Z, in which the X axis designates a radial direction of the turbomachine, the Y axis designates another radial direction of the turbomachine, the Y axis being transverse to the X axis of the turbomachine, and the Z axis designates a longitudinal direction of the turbomachine, which is substantially parallel to a longitudinal direction of the aircraft when the turbomachine is installed on the latter.

[0029] Assembly 1 includes a main structure, a rotor 3 movable relative to the radial axis X of the turbomachine, a stator 4 fixed relative to the radial axis X of the turbomachine and a lightning recovery system 5.

[0030] The rotor 3 comprises a blade root 3a, variable-pitch blades (not shown in the figures) fixed to the blade root 3a, and a pivot 3b. The stator 4 surrounds the rotor 3; more specifically, the stator 4 surrounds the pivot 3b of the rotor 3 and is fixed to the main structure of the turbomachine.

[0031] As illustrated in Figure 2, the lightning recovery system 5 comprises a pin 6, a screw 7 and a linking means 8 for the pin 6 and the screw 7. At least one face of said pin 6 is in contact by friction with the rotor 3 and the screw 7 is located in the radial extension of said pin 6. The screw 8 passes through the stator 4 along the longitudinal axis Z of the turbomachine.

[0032] According to the embodiment shown in the figures, the pin 6 is substantially cylindrical in shape, one of its lateral bases being in contact by friction with an external lateral surface of the pivot 3b of the rotor 3. The pin 6 thus extends radially towards the stator 4 the external lateral surface of the pivot 3b of the rotor 3. The pin 6 and the screw 7 form an elongated element in contact with the pivot 3b of the rotor 3 and passing through the stator 4 to an exit point 9. Advantageously, the pin 6 contains graphite. The means for connecting the pin 6 and the screw 7 includes a spring interposed between said pin 6 and said screw 7. More specifically, the screw 7 includes a threaded hole 7a into which the spring and a portion of the pin 6 are inserted. The spring thus connects the screw 7 and the pin 6 and creates a mechanical force compelling the pin 6 to make contact with the rotor 3.The pin 6 is in contact with the screw 7 and more particularly with the thread 7a of the screw 7 in order to facilitate the transmission of current when lightning makes contact with assembly 1.

[0033] In addition, the external lateral surface of the rotor 3 includes a radial groove 3c into which at least part of the lightning recovery system 5 is inserted, and in particular into which the pin 6 and part of the screw 7 are inserted. The groove 3c of the rotor 3 makes it possible not to locally obstruct the variable pitch blade assembly 1, the lightning recovery system 5 being thus directly embedded in the variable pitch blade assembly 1.

[0034] As illustrated in Figure 1, the lightning-induced current passes through the blade foot 3a and the pivot 3b of the rotor 3 and is attracted by the graphite pin 6, passes through the spring and the screw 7 and goes to the exit point 9 of the lightning recovery system 5. The exit point 9 of the lightning recovery system 5 then directs the current to the aircraft structure.

[0035] Figure 3 shows a top view of the rotor 3 pivot 3b and the pin 6 in contact with the outer lateral surface of said pivot 3b. The face of the pin 6 in contact with said pivot 3b has a concave profile 10. The concave profile 10 of the pin 6 is complementary in shape to the outer lateral surface of the pivot 3b, thus improving the contact between the pin 6 and the pivot 3b. In particular, the concave profile 10 of the pin 6 follows the cylindrical shape of the rotor 3 pivot 3b.

[0036] This feature also allows for an increased contact area between the rotor 3 and the pin 6, thereby enhancing the efficiency of the lightning recovery system 5 when the current to be recovered is high. If the current to be recovered is relatively low, a simple point contact between the rotor 3 and the pin 6 may suffice. At least the face of the pin 6 in contact with the rotor 3 has a coating 1 with a low coefficient of friction, preferably between 0.02 micrometers and 0.1 micrometers. Similarly, the outer lateral face of the rotor 3 or the inner face of the groove 3c in contact with the pin 6 has a coating with a low coefficient of friction.

[0037] Furthermore, the pin 6, the screw 7, and the connecting means 8 for the pin 6 and the screw 7 are capable of withstanding the charge of the captured lightning current. The pin 6, the screw 7, and the connecting means 8 for the pin 6 and the screw 7 comprise electrically conductive materials.

[0038] 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 5 comprising several pins 6 and / or several screws 7 and / or several means of connecting the pin 6 and the screw 7. It is also possible to consider that the lightning arrester system 5 is positioned axially between the blade root 3a and the stator 4, with the pin 6 thus in contact by friction with the underside of the blade root 3a. Furthermore, a variable-pitch blade assembly 1 can include several lightning arrester systems 5 as described above.

[0039] Finally, a lightning recovery system 5 applies to any system comprising a rotating part relative to a fixed part, said system being liable to be struck by lightning.

[0040] The lightning recovery system 5 provides electrical continuity between the rotor 3 and the stator 4 of a turbomachine without generating excessive friction in assembly 1. The lightning recovery system 5 is easy to manufacture and install and does not obstruct the turbomachine locally. Furthermore, the lightning recovery system 5 is easily accessible for maintenance on the turbomachine.

Claims

DEMANDS 1. Assembly (1) of variable pitch blade for unfaired aircraft turbomachine, the assembly comprising a rotor (3) movable with respect to a radial axis (X) of the turbomachine, a stator (4) fixed with respect to said radial axis (X) and at least one lightning recovery system (5), characterized in that the lightning recovery system (5) comprises a pin (6), at least one face of said pin (6) being in contact by friction with the rotor (3), a screw (7) radially extending said pin (6) and a means of connecting (8) the pin (6) and the screw (7), said means of connecting (8) comprising a spring interposed between the pin (6) and the screw (7).

2. Assembly (1) according to claim 1, wherein the rotor (3) comprises a blade foot (3a) and variable pitch blades fixed on the blade foot (3a).

3. Assembly (1) according to any one of claims 1 and 2, wherein the screw (7) of the lightning recovery system (5) passes through the stator (4) along a longitudinal axis (Z) of the turbomachine and wherein the pin (6) is in contact with the external lateral surface of the rotor (3).

4. Assembly (1) according to any one of claims 1 to 3, wherein the external lateral surface of the rotor (3) comprises a radial groove (3c) into which the pin (6) is inserted.

5. Assembly (1) according to any one of claims 1 to 4, wherein the pin (6) comprises graphite.

6. Assembly (1) according to any one of claims 1 to 5, wherein at least the face of the pin (6) in contact with the rotor (3) has a coating (11) comprising a low coefficient of friction, preferably between 0.02 micrometer and 0.1 micrometer.

7. Assembly (1) according to any one of claims 1 to 6, wherein the screw (7) comprises a thread (7a) into which the spring and part of the pin (6) are inserted.

8. Assembly (1) according to any one of claims 1 to 7, wherein the face of the pin (6) in contact with the rotor (3) comprises a concave profile (10) conforming to the shape of the rotor (3).

9. Assembly (1) according to any one of claims 1 to 8, comprising two lightning recovery systems (5) distributed radially around the rotor (3).

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

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