Turbomachine blading assembly comprising means for limiting vibration between platforms

Abstract

The invention proposes a bladed assembly (10) comprising two adjacent blades (12), and each blade (12) a platform (16) located at a free radial end, wherein the platform (16) of the first blade (12) comprises a lateral face (18) which is located circumferentially facing an associated lateral face (18) of the platform (16) of the second blade (12), the platform (16) of the first blade (12) coming into contact with the platform (16) of the second blade (12) via only a protrusion (20) which projects circumferentially with respect to the lateral face (18) of the platform (16) of the first blade (12) in the direction of the platform (16) of the second blade (12), and the protrusion (20) is received in a groove (22) formed in the platform (16) of the second blade, the protrusion (20) and the groove (22) each extending in a plane substantially perpendicular to a radial direction with respect to the main axis (A), the protrusion (20) comprising a radially outer face (24) which is oriented radially outwards and which bears radially against a bottom face (30) of the groove (22) which is oriented radially inwards, and the protrusion (20) and the groove (22) are located axially substantially in the middle of the platform (16) associated therewith.

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 assembly designed to dampen vibrations occurring at the outer radial ends of moving blades by cooperating with each other.

[0005] The invention aims to improve existing solutions.

[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 free radial end of each blade, commonly called 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] Document FR-A-2.612.249 describes a set of blades whose platforms cooperate with each other to bear against each other to produce friction forces at specific contact points.

[0015] This document further describes that the platforms include additional contacts made by extensions of a heel which bears against an associated face of the other platform.

[0016] Such an embodiment makes the design of the platform particularly complex since there are several contact zones to be provided to achieve vibration damping.

[0017] The aim of the invention is to propose a turbomachine assembly which is designed to allow damping of vibrations by friction without having to prestress the blades during assembly.

[0018] STATEMENT OF THE INVENTION

[0019] The invention provides a turbomachine blade extending around a main axis A and comprising at least a first blade and a second blade which are circumferentially adjacent, each of the first blade and the second 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 the first blade comprises a lateral face which is located circumferentially opposite an associated lateral face of the platform of the second blade, characterized in that the platform of the first blade is intended to come into contact with the platform of the second blade, during operation of the turbomachine, solely by means of a protrusion which projects circumferentially relative to the lateral face of the platform of the first blade in the direction of the platform of the second blade,and in that the protrusion is received in a groove formed in the platform of the second blade.,

[0020] The contact of the platforms with each other only through the cooperation of the protrusion with the groove makes it possible to simplify the assembly and not to put the assembly under prestressing before use.

[0021] Preferably, the groove formed in the second blade and which is associated with the protrusion of the first blade is circumferentially open in a lateral face of the platform of the second blade in the direction of the platform of the first blade.

[0022] Preferably, the protrusion of the first blade comprises at least one face, which bears against an opposite face of the groove of the second blade.

[0023] Preferably, each of the protrusion and the groove extends in a plane substantially perpendicular to a radial direction relative to the main axis A, and in that the protrusion comprises a radially external face which is oriented radially outwards and which bears radially against a bottom face of the groove which is oriented radially inwards.

[0024] Preferably, the groove of the second blade is delimited axially by two lateral faces against which the protrusion of the first blade is able to bear axially.

[0025] Preferably, the protrusion and the groove are located axially substantially in the middle of the platform associated with them.

[0026] Preferably, each of the first blade platform and the second blade platform has a protrusion at one circumferential end and a groove at its other circumferential end.

[0027] Preferably, the protrusion is arranged at a circumferential end of the platform of the first blade or of the second blade which is located on the intrados side of the blade of said first or second blade.

[0028] Preferably, the protrusion of the first blade is received with axial clearance in the groove of the second blade associated therewith. Preferably, the circumferential length of the groove is between 2.5 and 6 millimeters and the width of the protrusion, measured in an axial direction, is between 2.5 and 8 millimeters.

[0029] Preferably, the protrusion projects radially outwardly relative to the remainder of the platform and the groove is formed in a radial protrusion projecting radially outwardly relative to the remainder of the platform of the second blade.

[0030] The invention also relates to an aircraft turbomachine comprising a bladed assembly according to the invention.

[0031] BRIEF DESCRIPTION OF THE DRAWINGS

[0032] [Fig. 1] is a schematic perspective representation of a bladed assembly comprising two blades connected to each other by a protrusion and a groove according to the invention.

[0033] [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.

[0034] [Fig. 3A] is a view in a radially inward direction of a blade shown in Figure 1.

[0035] [Fig. 3B] is a view in a radially outward direction of the blade shown in Fig. 3A.

[0036] [Fig. 4] is a view in a radial direction towards the inside of the bladed assembly shown in Figure 1.

[0037] [Fig. 5] is a section along a radial plane passing through the main axis A of the bladed assembly shown in Figure 1.

[0038] [Fig. 6] and [Fig. 7] are views similar to those of Figures 1 and 2, illustrating another embodiment of the invention.

[0039] [Fig. 8] is a partial view of a turbomachine rotor element equipped with a bladed assembly according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0040] The figures show a part of a bladed assembly 10 of a turbomachine consisting of a plurality of blades 12. Preferably, the turbomachine comprising the bladed assembly 10 is an aircraft turbomachine.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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. The outer radial end of the blade 12, which is opposite the root 15 for fixing the blade 12 to the rotor, further comprises sealing lips (not shown).

[0047] It will be understood that the invention is not limited to this embodiment and that the platform may be located at the inner radial end of the blade 14 when the vane 12 is fixed to the support element by its outer radial end.

[0048] The bladed assembly 10 shown in the figures consists of two blades 12 which are circumferentially adjacent in the turbomachine, namely a first blade located to the left of the figures, and a second blade 12 located to the right of the figures.

[0049] In particular, the platforms 16 of the blades 12 are located close to each other in a circumferential direction.

[0050] The platform 16 of the first blade 12 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 second blade 12, which is associated with it. 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 A of the bladed assembly 10.

[0051] During rotation of the bladed assembly 10 around its main axis A, in particular during operation of the turbomachine, the centrifugal action created on this occasion causes the platform 16 of the first blade 12 to come into contact with the platform 16 of the second blade 12.

[0052] For this, the platform 16 of the first blade 12 comprises a protrusion 20 which is received and cooperates with an associated groove 22 formed in the platform 16 of the second blade 12.

[0053] The cooperation of the protrusion 20 with the groove 22 associated with it makes it possible, during operation of the turbomachine, to generate friction forces limiting the vibrations of the platforms 16.

[0054] According to one embodiment, the two platforms 16 are in contact with each other only via the protrusion 20 and the groove 22.

[0055] The protrusion 20 projects relative to the lateral face 18 of the platform 16 of the first blade 12, in the circumferential direction and in the direction of the platform 16 of the second blade 12. The protrusion 20 further extends in a plane substantially perpendicular to the radial direction, that is to say in a plane parallel to the main axis A and parallel to the circumferential direction.

[0056] The protrusion 20 comprises a radially external face 24 oriented radially outwards, two lateral faces 26, taken in the axial direction, and an end face 28 located at the free circumferential end of the protrusion 20.

[0057] The groove 22 also extends in a plane substantially perpendicular to the radial direction, that is to say in a plane parallel to the main axis A and parallel to the circumferential direction.

[0058] It opens circumferentially into the lateral face 18 of the platform 16 of the second blade 12 which faces the platform 16 of the first blade 12 in order to receive the protrusion 20 carried by the first blade 12.

[0059] The groove 22 also opens radially inwards.

[0060] The groove 22 thus comprises a bottom face 30 oriented radially inwards, two lateral faces 32 taken in the axial direction and a circumferential end face 34.

[0061] According to a preferred embodiment, the protrusion 20 and the groove 22 are located axially substantially in the middle of the platform 16 associated with them.

[0062] According to the embodiment shown in Figures 2 to 5, the protrusion 20 is located radially in the plane of the rest of the platform 16 of the first blade 12 and the groove 22 consists of a cavity formed in the platform 16 of the second blade 12.

[0063] As can be seen in more detail in Figure 5, the platform of the second blade 12 comprises a boss 36 extending radially outwards and which is located at the level of the groove 22 of the platform 16. This boss has the function of locally increasing the quantity of material of the platform 16, thus improving its mechanical strength.

[0064] According to another embodiment shown in Figures 6 and 7, the protrusion 20 projects radially outwards relative to the rest of the platform 16. The same is true for the groove 22 which is formed in a radial protrusion 38 projecting radially outwards relative to the rest of the platform.

[0065] 16 of the second dawn 12.

[0066] According to this other embodiment, the groove 22 only opens circumferentially at the level of the lateral face 18 of the platform 16 of the second blade 12 which faces the platform 16 of the first blade 12.

[0067] The radial thickness of the groove 22 is substantially greater than the radial thickness of the protrusion 20, to allow the blades 12 to be assembled with each other.

[0068] The protrusion 20 and the groove 22 are preferably produced by machining the platform, in particular when the blade 12 is made of CMC material.

[0069] During operation of the turbomachine, the forces acting on the platforms 16, in particular the centrifugal force, cause deformations thereof, causing in particular a radial displacement of each protrusion 20 greater than the rest of the blade 12 of which the protrusion 20 is part, that is to say of the first blade 12. This phenomenon is all the more significant when the protrusion 20 is carried by a circumferential end of the intrados of the platform 16 of the first blade 12, with reference to the direction of flow of a gas flow (not shown) in the turbomachine.

[0070] As previously stated, the protrusion 20 which is carried by the platform 16 of the first blade 12 is received in the facing groove 22 which is formed in the platform 16 of the second blade 12. The radial displacement of the protrusion 20 leads to radial support of the radially external face 24 of the protrusion 20 against the bottom face 30 of the groove 22, radially outwards.

[0071] Also, during operation of the turbomachine, the platforms 16 are subjected to vibrations, in particular in a plane perpendicular to the radial direction. The radial support of the radially external face 24 of the protrusion 20 against the bottom face 30 of the groove 22 produces friction forces in directions perpendicular to the radial direction, thus counteracting the vibrations of the platforms 16.

[0072] Furthermore, when the protrusion 20 is received in the groove 22, the two lateral faces 26 are located axially opposite the lateral faces 32 of the groove 22. According to a preferred embodiment, an axial clearance is present between the lateral faces 26, 32 opposite each other and, during operation of the turbomachine, the protrusion 20 is able to come into contact against one or the other of the two lateral faces 32 of the groove 22, to limit the amplitude of the relative vibrations of the two platforms 16.

[0073] According to a preferred embodiment, each platform 16 of the set of blades 12 of the bladed assembly 10 comprises a protrusion 20 on a first circumferential side, preferably the intrados side, and comprises a groove 22 on the other circumferential side.

[0074] Thus, each platform 16 cooperates with the two platforms 16 which are circumferentially adjacent to it to limit vibrations.

[0075] By way of non-limiting example, the circumferential depth of the groove 22, that is to say the distance between the lateral face 18 into which the groove 22 opens and the circumferential end face 34 of the groove 22 is greater than 2.5 mm, to ensure sufficient damping taking into account the tolerances and operating clearances and is less than 6 mm to guarantee good mechanical strength of the platform 16.

[0076] According to another example, the circumferential length of the protrusion 20 and the groove 22 is between 1 mm and 50% of the circumferential length of the platform 16.

[0077] The axial width of the protrusion 20, that is to say the axial distance between the lateral faces 26, is greater than 2.5 mm to ensure sufficient damping taking into account the tolerances and operating clearances, and it is less than 8 mm to guarantee good mechanical strength of the protrusion 20. It is in any case less than the axial length of the platform 16.

[0078] As can be seen in Figure 3A, the protrusion 20 is generally inclined relative to the platform 16 and more particularly relative to the lateral face 18. The same is true for the groove 22 which is inclined relative to the lateral face 18 of the platform 16 of the second blade 12.

Claims

Demands 1. Bladed assembly (10) of a turbomachine extending about a main axis (A) and comprising at least one circumferentially adjacent first blade (12) and second blade (12), each of the first blade (12) and second blade (12) comprising a blade (14) extending in a radial extension direction with respect to said main axis (A) and comprising a platform (16) located at a free radial end of the blade (14), wherein the platform (16) of the first blade (12) comprises a lateral face (18) which is circumferentially located opposite an associated lateral face (18) of the platform (16) of the second blade (12), wherein the platform (16) of the first blade (12) is intended to come into contact with the platform (16) of the second blade (12) during operation of the turbomachine,by means solely of a projection (20) extending circumferentially from the lateral face (18) of the platform (16) of the first blade (12) towards the platform (16) of the second blade (12), and in that the projection (20) is received in a groove (22) formed in the platform (16) of the second blade, characterized in that each of the projection (20) and the groove (22) extends in a plane substantially perpendicular to a radial direction with respect to the principal axis (A), the projection (20) having a radially external face (24) which is oriented radially outwards and which bears radially against a bottom face (30) of the groove (22) which is oriented radially inwards, and in that the projection (20) and the groove (22) are located axially approximately in the middle of the platform (16) associated with them.

2. Bladed assembly (10) according to claim 1, characterized in that the groove (22) formed in the second blade (12) and which is associated with the protrusion (20) of the first blade (12) is open circumferentially in a lateral face (18) of the platform (16) of the second blade (12) in the direction of the platform (16) of the first blade (12).

3. Bladed assembly (10) according to one of claims 1 or 2, characterized in that the protrusion (20) of the first blade (12) has at least one face (24, 26) which is in contact with an opposite face (30, 32) of the groove (22) of the second blade (12).

4. Bladed assembly (10) according to any one of claims 1 to 3, characterized in that the groove (22) of the second blade (12) is axially delimited by two lateral faces (32) against which the protrusion (20) of the first blade (12) is able to rest axially.

5. Bladed assembly (10) according to any one of claims 1 to 4, characterized in that each of the platform (16) of the first blade (12) and of the platform (16) of the second blade (12) has an outgrowth (20) at one circumferential end and a groove (22) at its other circumferential end.

6. Bladed assembly (10) according to any one of claims 1 to 5, characterized in that the protrusion (20) is disposed at a circumferential end of the platform (16) of the first blade (12) or of the second blade (12), the circumferential end being located on the intrados side of the blade of said first or second blade (12).

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