Turbomachine blading assembly comprising means for limiting vibration between platforms

Abstract

The invention proposes a turbomachine bladed assembly (10) comprising at least two adjacent blades (12), each blade (12) comprising a radial vane (14) and a platform (16) located at a free radial end of the vane (14), wherein the platform (16) of each blade (12) of the bladed assembly (10) is located circumferentially facing a platform (16) of the other circumferentially adjacent blade (12) of the bladed assembly (10), wherein the bladed assembly (10) comprises an insert (20) arranged circumferentially between the platforms (16) and which cooperates with the platforms (16), each platform (16) comprising a circumferential bearing face (32) with which one circumferential end of the insert (20) is in contact, the direction of the contact between each circumferential bearing face (32) and the insert (20) being oriented circumferentially with respect to the main axis A, the assembly comprising means for axially retaining the insert (20) between the two platforms (16) which comprise at least one finger (36) which is carried by the insert (20), projects circumferentially from the insert (20), and is received in an associated notch (38) formed circumferentially as a recess in at least one of the platforms (16), said at least one finger (36) and the associated notch (38) being designed to allow a relative movement of the insert (20) with respect to the platforms (16) in the radial direction.

Description

[0001] Description

[0002] Title: Turbomachine blade assembly comprising means for limiting vibrations between platforms

[0003] TECHNICAL FIELD

[0004] The invention relates to a turbomachine bladed assembly designed to provide vibration damping of the outer radial ends of moving blades by cooperation with each other.

[0005] The invention aims to replace existing solutions consisting of assembling the blades with pre-stressing during assembly.

[0006] STATE OF THE PRIOR ART

[0007] During the operation of a turbomachine, the blades, and more particularly the moving blades, are subjected to various vibrations.

[0008] These vibrations are generally greatest at the outer radial tip of each blade, commonly referred to as the "platform."

[0009] To limit the amplitude of vibrations at the platforms, it was proposed to assemble the blades with torsional prestressing of the blades.

[0010] During operation of the turbomachine, the prestress mentioned above, associated with a particular assembly, produces friction forces making it possible to reduce the amplitude of vibrations.

[0011] This assembly involves particular shapes of the blade platforms, to fit together in a predefined manner.

[0012] However, due to rotation of the blade in one direction or the other, or a change in the relative position of the blade platforms, the contact force between the platforms may vary, which may adversely affect vibration damping.

[0013] Furthermore, in the case of blades made of CMC (ceramic matrix composite) material, this material does not allow for torsional pre-stresses as high as other materials. Such pre-stresses induce strong static stresses that can go beyond those permitted by the material.

[0014] The aim of the invention is to propose a turbomachine bladed assembly which is designed to allow damping of vibrations by friction without having to prestress the blades during assembly.

[0015] STATEMENT OF THE INVENTION

[0016] The invention provides a turbomachine bladed assembly extending around a main axis A and comprising at least two circumferentially adjacent blades, each blade comprising a blade extending in a radial extension direction relative to said main axis A and a platform located at a free radial end of the blade, in which the platform of each blade of the bladed assembly is located circumferentially opposite a platform of the other circumferentially adjacent blade of the bladed assembly, in which the bladed assembly comprises an insert arranged circumferentially between the platforms and which cooperates with the platforms, characterized in that each platform comprises a circumferential bearing face against which a circumferential end of the insert is in contact, and in that the direction of contact between each circumferential bearing face and the insert is oriented circumferentially relative to the main axis A.

[0017] Preferably, at least one of the two platforms comprises a groove open circumferentially towards the other of the two platforms, one face of the groove of which forms the circumferential bearing face and in which said groove, a circumferential end of the insert is received.

[0018] Preferably, said circumferential bearing face is in the shape of an arc of a circle or is inclined with respect to the radial direction. Preferably, the circumferential bearing face of a platform is parallel to a radial direction with respect to the main axis A.

[0019] Preferably, the circumferential bearing face comprises a groove.

[0020] Preferably, the insert comprises two contact faces, each contact face of which has a shape complementary to the shape of the bearing face associated with it.

[0021] Preferably, at least one contact face of the insert is in the form of a cylindrical arc whose axis is parallel to the main direction of the insert.

[0022] Preferably, each circumferential end of the insert is received with radial clearance and circumferential clearance in the groove associated therewith.

[0023] Preferably, each platform comprises a boss of radial thickness greater than the thickness of the rest of the platform, in which said boss the groove is formed.

[0024] Preferably, the bladed assembly comprises means for axial retention of the insert between the two platforms.

[0025] Preferably, the axial retention means comprise at least one finger carried by the insert which projects circumferentially from the insert and which is received in an associated notch formed in a circumferential hollow in at least one of the platforms.

[0026] The invention also proposes an aircraft turbomachine comprising a bladed assembly according to the invention.

[0027] BRIEF DESCRIPTION OF THE DRAWINGS

[0028] [Fig. 1] is an end view of a turbomachine bladed assembly in a radial direction relative to a main axis of the bladed assembly.

[0029] [Fig. 2] is a section of the bladed assembly shown in Figure 1 along a plane perpendicular to the main axis of the bladed assembly.

[0030] [Fig. 3] is a view similar to that of Figure 2, showing another relative position of the insert with respect to the platforms in the event of expansion of the latter. [Fig. 4] is a view similar to that of Figure 1, showing an alternative embodiment of the insert.

[0031] [Fig. 5] is a view similar to that of Fig. 2, showing a section of the bladed assembly shown in Fig. 4.

[0032] [Fig. 6] is a section of a bladed assembly taken in a circumferential direction, showing a first embodiment of insert retaining means.

[0033] [Fig. 7] is a section similar to that of Fig. 6, showing another embodiment of the retaining means.

[0034] [Fig. 8] is a partial view of a turbomachine rotor element equipped with a bladed assembly according to the invention.

[0035] DETAILED DESCRIPTION OF THE INVENTION

[0036] The figures show a portion of a bladed assembly 10 of a turbomachine comprising two circumferentially adjacent blades 12. Preferably, the turbomachine comprising the bladed assembly 10 is an aircraft turbomachine.

[0037] This bladed assembly 10 is preferably a component belonging to a rotor disk of the turbomachine such as the rotor disk DR, part of which is shown in FIG. 8. The blades 12 can then be mounted by their roots in corresponding cells of this disk DR, constituting a crown of blades 21a, 21b which surround the disk DR while being carried by the latter.

[0038] Here, and according to a non-limiting embodiment, the blades 12 are moving blades of a low-pressure turbine of a turbomachine. It will be understood that the invention is not limited to this embodiment and that it may also relate to moving blades of other modules of the turbomachine or fixed blades.

[0039] The bladed assembly 10 has a main axis A which is intended to be coincident with, or coaxial with, the main axis of the turbomachine when the bladed assembly 10 is mounted therein. Each blade 12 comprises a blade 14 extending in a radial direction relative to the main axis, a first radial end portion 15 called the root portion which is connected to a first radial end of the blade 14 and a second radial end portion 16 called the platform portion, which is connected to a second radial end of the blade 14.

[0040] Preferably, the platform 16 is connected to the free radial end of the blade 14, that is to say the radial end of the blade 14 which is not fixed to a rotating element supporting the blades 12.

[0041] Thus, according to the embodiment shown in the figures, the platform 16 is located at the outer radial end of the blade 14. The inner radial end of the blade 14 carries the root 15 of the blade 12, by which the blade is mounted on the support element. As visible in Figure 8 and by way of preferred but non-limiting example, the root 15 of the blade 12 is mounted in a cell 17 of the rotor disk DR of the turbomachine.

[0042] The outer radial end of the blade 12, which is opposite the foot 15 for fixing the blade 12 to the rotor, further comprises sealing lips (not shown).

[0043] The bladed assembly 10 shown in the figures consists of two blades 12 which are circumferentially adjacent in the turbomachine.

[0044] In particular, the platforms 16 of the blades 12 are located close to each other in a circumferential direction.

[0045] Each platform 16 comprises a lateral face 18 which is situated circumferentially opposite and at a distance from a lateral face 18 of the platform 16 of the circumferentially adjacent blade. Here, the two lateral faces 18 opposite each other are parallel to each other and are inclined relative to a plane passing through the main axis of the bladed assembly 10.

[0046] The bladed assembly 10 also comprises an insert 20 which is arranged circumferentially between the platforms of the two circumferentially adjacent blades 12 and which cooperates with the two platforms 16 simultaneously, so that when vibrations are produced on the blades 12, friction occurs between the insert 20 and the platforms 16 to reduce the amplitude of the vibratory movements of the platforms 16.

[0047] Preferably, the insert 20 cooperates with the platforms 16 to reduce vibrations.

[0048] For this purpose, each lateral face 18 of one of the two platforms 16 comprises a bearing face 32 against which the insert 20 bears. In addition, the support of the insert 20 on the bearing face 32 is oriented at least partly circumferentially relative to the main axis A.

[0049] Also, at least one bearing face 32 against which the insert 20 bears is inclined relative to the radial direction.

[0050] For this, the lateral face 18 of at least one platform 16 comprises a groove 22 receiving a circumferential end of the insert 20 which is associated with it. This groove 22 comprises a face forming the bearing face 32 of the platform and it opens in the circumferential direction towards the platform 16 of the other blade 12.

[0051] The bearing face 32 is the radially external face of the groove 22, which is oriented partly radially inwards, that is to say towards the main axis A, and partly circumferentially in the direction of the other platform 16.

[0052] According to a first embodiment shown in Figures 1 to 3, the bearing face 32 of one of the two platforms 16, here the right-hand platform 16, extends in a plane parallel to the radial direction. Thus, the support of the insert 20 against this bearing face 32 is oriented entirely circumferentially relative to the main axis A.

[0053] According to this first embodiment, only the bearing face 32 of the other platform 16, that is to say here the left platform 16, comprises a groove 22 comprising a bearing face 32.

[0054] Thus, according to this embodiment, the insert 20 is both circumferentially compressed between the two bearing faces 32 of the two platforms 16 and it bears radially outwards against the bearing face 32 of the left platform, partly delimiting the groove 22. During operation of the turbomachine in which the bladed assembly 10 is arranged, the bearing of the insert 20 against the inclined bearing face 32 causes the insert 20 to bear against the other bearing face 32, which is oriented radially, in the circumferential direction.

[0055] By this circumferential support, friction forces between the insert 20 and the bearing face 32 are produced, consequently reducing the vibrations of the two circumferentially adjacent platforms 16.

[0056] As can be seen in Figure 3, the inclination of a bearing face also makes it possible to compensate for the dimensional variations of the blades 12 caused by their expansion. During the expansion of the blades 12, the circumferentially adjacent platforms 16 are caused to move circumferentially apart from each other. Since at least one bearing face 32 is inclined relative to the radial direction, even if the platforms 16 move circumferentially apart from each other, that is to say the bearing faces 32 move circumferentially apart from each other, the insert 20 moves radially relative to the main axis A, while remaining in contact with the two bearing faces 32.

[0057] The vibration damping function is thus preserved.

[0058] According to another embodiment shown in Figures 4 and 5, the lateral face 18 of each platform 16 comprises a groove 22 receiving a circumferential end of the insert 20 associated with it. This groove 22 comprises a face forming the bearing face 32 of the platform and it opens in the circumferential direction towards the platform 16 of the other blade 12.

[0059] The bearing face 32 is the radially external face of the groove 22, which is oriented partly radially inwards, that is to say towards the main axis A, and partly circumferentially in the direction of the other platform 16.

[0060] The insert 20 comprises contact faces 34 which are intended to come into contact with the bearing faces 32 of the platforms 16. Each contact face 34 has a shape complementary to the shape of the bearing face 32 associated with it. The contact face 34 and the bearing face 32 associated with it are arranged circumferentially opposite each other. Thus, according to the embodiment shown in Figures 1 and 2, a contact face 34 is oriented partly radially outwards, that is to say which moves away from the main axis A, and partly circumferentially in the direction of the platform 16 associated with the contact face 34. The other contact face 34 extends in a plane parallel to the radial direction so that the support of the insert 20 against the associated support face 32 is oriented entirely circumferentially relative to the main axis A.

[0061] According to the embodiment shown in Figures 4 and 5, each of the two contact faces 34 is oriented partly radially outwards, that is to say away from the main axis A, and partly circumferentially in the direction of the platform 16 associated with the contact face 34.

[0062] Whatever the embodiment, in order to allow relative movement of the platforms 16 relative to one another, in particular due to the expansion of the blades 12, the insert 20 is received with play in the groove 22 or the two grooves 22. Preferably, each circumferential end of the insert 20 is received with radial play and circumferential play in each of the two grooves 22.

[0063] For this, the radial dimension as well as the depth, measured circumferentially, of each groove 22 is greater than the radial thickness of the insert 20 and the circumferential length of the part of the insert which is received in each groove 22.

[0064] To compensate for this difference in expansion, and according to an alternative embodiment shown in Figure 5, the contact face 34 of the insert 20 is curved radially outwards. Preferably, the contact face 34 of the insert 20 is in the form of a cylindrical arc whose axis is parallel to the substantially axial main direction of the insert 20.

[0065] In addition to this curved shape of the insert 20, the bearing face 32 of each groove 22 is also curved and forms a cylindrical arc whose axis is parallel to the substantially axial main direction of the lateral face 18. Preferably, the radius of the cylinder associated with each bearing face 32 of a groove 22 is greater than the radius of the cylinder associated with the contact face 34 of the insert 20.

[0066] By these convex shapes of the walls and faces facing each other, whatever the deformation of one and / or the other of the blades 12 and the displacement of their platforms 16, the contact between the insert 20 and each platform 16 is distributed in a cylinder-cylinder contact, that is to say a contact distributed over the entire length of the insert 20.

[0067] To receive each groove 22, a platform 16 has a boss 28, that is to say a radial excess thickness. This excess thickness results in an increase in the mass of the platform 16. Thus, the greater the length of the insert 20, or of the associated grooves 22, the greater the mass of the platform 16.

[0068] According to another aspect of the invention shown in Figures 6 and 7, the bladed assembly 10 comprises means for axial retention of the insert 20 between the two platforms 16.

[0069] According to a first embodiment, the axial length of the insert 20 and of the groove 22 associated with it is less than the axial length of the platform 16 and the groove 22 does not open into each axial end of the platform 16. Thus, the insert 20 is able to come into axial abutment against an axial end of the groove 22 in which it is partly received.

[0070] According to a second embodiment shown in Figure 7, these axial retention means consist of fingers 36 which project circumferentially relative to the rest of the insert 20 and which are received in associated notches 38 formed in the platforms 16.

[0071] The fingers 36 and notches 38 are designed to allow relative movement of the insert 20 with respect to the platforms 16 in the radial direction.

[0072] The platform 16 and the functional surfaces thereof, i.e. the boss 28, the lateral face 18 and the walls of the groove 22 are made of CMC, i.e. Ceramic Matrix Composite, by weaving, molding and then possibly machining the functional parts.

[0073] The insert 20 is for example made of a refractory metallic material based on nickel or cobalt or else in a monolithic or fiber-reinforced ceramic material. It will be understood that the material constituting the insert is not limited to these examples and that other materials can be used so as to adapt to the chosen application, in terms of temperature resistance and mass reduction while respecting the maintenance of the insert 20 and generating the desired level of damping.

Claims

Demands 1. Bladed assembly (10) of a turbomachine extending about a principal axis (A) and comprising at least two circumferentially adjacent blades (12), each blade (12) comprising a blade (14) extending in a radial direction with respect to said principal axis A and a platform (16) located at a free radial end of the blade (14), wherein the platform (16) of each blade (12) of the bladed assembly (10) is located circumferentially opposite a platform (16) of the other circumferentially adjacent blade (12) of the bladed assembly (10), wherein the bladed assembly (10) comprises an insert (20) arranged circumferentially between the platforms (16) and which cooperates with the platforms (16), wherein each platform (16) comprises a circumferential bearing face (32) against which a circumferential end of the insert (20) is in contact,and the direction of contact between each circumferential bearing face (32) and the insert (20) is oriented circumferentially with respect to the principal axis A, characterized in that it comprises means for axial retention of the insert (20) between the two platforms (16) which include at least one finger (36) carried by the insert (20) which extends circumferentially from the insert (20) and which is received in an associated notch (38) formed circumferentially in at least one of the platforms (16), said at least one finger (36) and the associated notch (38) are designed to allow relative displacement of the insert (20) with respect to the platforms (16) in the radial direction.

2. Bladed assembly (10) according to claim 1, characterized in that at least one of the two platforms (16) has a groove (22) open circumferentially towards the other of the two platforms (16), of which one face of the groove (22) forms the circumferential bearing face (32) and in which said groove (22), a circumferential end of the insert (20) is received.

3. Bladed assembly (10) according to claim 1 or 2, characterized in that said circumferential bearing face (32) is in the shape of an arc of a circle or is inclined with respect to the radial direction.

4. Bladed assembly (10) according to any one of the preceding claims, characterized in that the circumferential bearing face (32) of a platform (16) is parallel in a radial direction with respect to the principal axis A.

5. Bladed assembly (10) according to any one of claims 1 to 3, characterized in that the circumferential bearing face (32) has a groove (22).

6. Bladed assembly (10) according to any one of the preceding claims, characterized in that the insert (20) has two contact faces (34) of which each contact face (34) is of complementary shape to the shape of the support face (32) associated with it.

7. Bladed assembly (10) according to the preceding claim, in combination with claim 3, characterized in that at least one contact face (34) of the insert (20) is in the form of a cylindrical arc whose axis is parallel to the main direction of the insert (20).

8. Bladed assembly (10) according to the preceding claim, characterized in that each circumferential end of the insert (20) is received with a radial clearance and a circumferential clearance in the groove (22) associated with it.

9. Bladed assembly (10) according to any one of the preceding claims, characterized in that each platform (16) has a boss (28) of radial thickness greater than the thickness of the rest of the platform (16), in which said boss (28) the groove (22) is formed.

10. Aircraft turbomachine comprising a bladed assembly (10) according to any one of the preceding claims. 5

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