Turbine bucket assembly comprising means for limiting vibrations between platforms

Abstract

The present invention provides a vane assembly (10) comprising two adjacent vanes (12), each vane (12) having a platform (16) at a free radial end, where the platform (16) of a first vane (12) comprises a side surface (18) positioned circumferentially opposite an associated side surface (18) of the platform (16) of a second vane (12), the platform (16) of the first vane (12) is intended to come into contact with the platform (16) of the second vane (12) solely via a projection (20) protruding circumferentially relative to a side surface (18) of the platform (16) of the first vane (12) in the direction of the platform (16) of the second vane (12), and the projection (20) is accommodated in a groove (22) formed in the platform (16) of the second vane (12), each of the projection (20) and the groove (22) extends in a plane substantially perpendicular to the radial direction with respect to the main axis (A), the projection (20) comprising a radially outer surface (24) oriented radially outwardly and bearing radially against a radially inwardly oriented bottom surface (30) of the groove (22), the projection (20) and the groove (22) are positioned substantially axially in the middle of a platform (16) associated with the projection and the groove.

Description

Technical Field

[0001] The present invention relates to a turbine assembly designed to achieve damping of vibration occurring at the outer radial ends of movable blades by the outer radial ends of the movable blades fitting each other.

[0002] The present invention aims to improve existing solutions. Background Art

[0003] During operation of the turbomachine, the buckets, and more specifically the movable buckets, are subject to various vibrations.

[0004] Typically, these vibrations are highest at the free radial end of each bucket, often referred to as the "platform."

[0005] In order to limit the amplitude of the vibrations at the platform, it has been proposed to assemble the blades with a torsional preload of the blades.

[0006] During operation of the turbomachine, the aforementioned preload associated with the specific installation generates friction forces which make it possible to reduce the amplitude of the vibrations.

[0007] This mounting means that the specific shapes of the platforms of the buckets interlock in a predetermined manner.

[0008] However, due to rotation of the blades in either direction or changes in the relative positions of the platforms of the blades, the contact forces between the platforms may vary, which may be detrimental to the damping of vibrations.

[0009] Furthermore, in the case of blades made of ceramic matrix composites (CMC), this material does not have such a high torsional preload compared to other materials. This preload causes high static stresses that may exceed the acceptable static stress of the material.

[0010] Document FR-A-2.612.249 describes a set of blades whose platforms cooperate to bear against each other in order to generate friction forces at specific contact points.

[0011] This document also describes that the platform comprises an additional contact portion formed by an extension of a heel which abuts against an associated surface of the other platform.

[0012] This embodiment makes the design of the platform particularly complex, since multiple contact areas have to be provided to achieve damping of vibrations.

[0013] The object of the present invention is to provide a turbine assembly which is designed such that vibrations can be damped by friction without having to preload the blades during assembly. Summary of the invention

[0014] The present invention provides a turbine blade, which extends around a main axis A and comprises at least one first blade and one second blade which are circumferentially adjacent to each other.

[0015] Each of the first and second vanes comprises a blade extending according to a radial extension direction relative to said main axis A and a platform located at a free radial end of the blade,

[0016] wherein the platform of the first bucket comprises a side surface which is positioned circumferentially opposite to an associated side surface of the platform of the second bucket,

[0017] It is characterized in that, during operation of the turbomachine, the platform of the first blade is intended to come into contact with the platform of the second blade only via a projection which protrudes circumferentially relative to the lateral surface of the platform of the first blade in the direction of the platform of the second blade and which is housed in a groove formed in the platform of the second blade.

[0018] The platforms contact each other only via the mating of the protrusions and recesses so that assembly can be simplified and there is no need to preload the assembly prior to use.

[0019] Preferably, the groove formed in the second blade and associated with the projection of the first blade opens circumferentially in the direction of the platform of the first blade to the side surface of the platform of the second blade.

[0020] Preferably, the projection of the first vane comprises at least one surface which bears against an opposing surface of the recess of the second vane.

[0021] Preferably, each of the projection and the groove extends in a plane substantially perpendicular to the radial direction relative to the main axis A, and the projection comprises a radially outer surface directed radially outwards and bearing radially against a radially inwardly directed bottom surface of the groove.

[0022] Preferably, the groove of the second vane is axially delimited by two side surfaces against which the projection of the first vane can bear axially.

[0023] Preferably, the projections and recesses are located axially substantially in the middle of the platform with which they are associated.

[0024] Preferably, each of the platform of the first bucket and the platform of the second bucket includes a protrusion at a circumferential end and a groove at the other circumferential end.

[0025] Preferably, the protrusion is arranged at a circumferential end of the platform of the first or second vane, the circumferential end being located on the soffit side of the blade of the first or second vane.

[0026] Preferably, the projection of the first blade is received with axial play in the groove of the second blade associated with the projection.

[0027] Preferably, the circumferential length of the groove is between 2.5 mm and 6 mm, and the width of the protrusion measured in the axial direction is between 2.5 mm and 8 mm.

[0028] Preferably, the projection projects radially outwardly relative to the remainder of the platform, and the groove is formed in the radial projection projecting radially outwardly relative to the remainder of the platform of the second bucket.

[0029] The invention also relates to an aircraft turbomachine comprising a blade assembly according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] [ Figure 1 ] is a schematic perspective view of a blade assembly according to the present invention, which includes two blades connected to each other by a protrusion and a groove.

[0031] [ Figure 2 ]yes Figure 1 The bucket assembly is shown in section according to a plane perpendicular to the main axis of the bucket assembly.

[0032] [ Figure 3A ] is based on Figure 1 A view of the bucket in a radially inward direction is shown.

[0033] [ Figure 3B ] is based on Figure 3A A view of the bucket in a radially outward direction is shown.

[0034] [ Figure 4 ] is based on Figure 1 A radially inward view of the bucket assembly is shown.

[0035] [ Figure 5 ] is a cross section taken along a radial plane that passes through Figure 1 The main axis A of the bucket assembly is shown.

[0036] [ Figure 6 ]and[ Figure 7 ] is similar to Figure 1 and Figure 2 , showing another embodiment of the present invention.

[0037] [ Figure 8 ] is a partial view of a turbine rotor element equipped with a blade assembly according to the present invention. DETAILED DESCRIPTION

[0038] The figure shows a portion of a turbine blade assembly 10 consisting of a plurality of blades 12. Preferably, the turbine including the blade assembly 10 is an aircraft turbine.

[0039] Preferably, the blade assembly 10 is a component of a rotor disk (for example, a rotor disk DR) of a turbine, a portion of which is Figure 8 The blades 12 can then be mounted in the corresponding cells of the disk DR by the roots of the blades, thereby forming the crowns of the blades 21a, 21b, which surround the disk DR while being carried by the disk DR.

[0040] In this case and according to a non-limiting embodiment, the blades 12 are movable blades of a low-pressure turbine of a turbomachine. It should be understood that the invention is not limited to this embodiment and that the invention may also relate to movable blades or fixed blades of other modules of a turbomachine.

[0041] The bucket assembly 10 has a main axis A which is intended to be coincident or coaxial with the main axis of the turbomachine when the bucket assembly 10 is mounted in the turbomachine.

[0042] Each bucket 12 comprises a blade 14 extending according to a radial direction relative to the main axis, a first radial end portion 15 (so-called root end) connected to a first radial end of the blade 14 and a second radial end portion 16 (so-called platform) connected to a second radial end of the bucket 14.

[0043] Preferably, the platform 16 is connected to the free radial end of the blade 14 , ie the radial end of the blade 14 that is not fastened to the supporting rotating element of the bucket 12 .

[0044] 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 supports the root 15 of the vane 12, by means of which the vane is mounted on a support element. Figure 8 As shown and by way of preferred but non-limiting example, the root 15 of the blade 12 is mounted in a cell 17 of a rotor disk DR of the turbomachine.

[0045] The outer radial end of the blade 12 opposite the root 15 for fastening the blade 12 to the rotor also comprises a sealing lip (not shown).

[0046] It should 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 blade 12 is fastened to the support element by the outer radial end of the blade.

[0047] The bucket assembly 10 shown in the figure is composed of two buckets 12 circumferentially adjacent to each other in the turbine (ie, a first bucket located on the left side in the figure and a second bucket 12 located on the right side in the figure).

[0048] In particular, the platforms 16 of the buckets 12 are positioned close to each other according to the circumferential direction.

[0049] The platform 16 of the first blade 12 comprises a side surface 18 which is located circumferentially opposite and at a distance from the side surface 18 of the platform 16 of the second blade 12, the side surface of the platform of the second blade being associated with the side surface of the platform of the first blade. In this case, the two opposite side surfaces 18 are parallel to each other and inclined relative to a plane passing through the main axis A of the blade assembly 10.

[0050] During rotation of the bucket assembly 10 about the main axis A of the bucket assembly, in particular during operation of the turbomachine, the centrifugal action thereby generated causes the platform 16 of the first bucket 12 to come into contact with the platform 16 of the second bucket 12 .

[0051] To this end, the platform 16 of the first bucket 12 comprises a protrusion / projection 20 which is received in and cooperates with an associated groove 22 formed in the platform 16 of the second bucket 12 .

[0052] The cooperation between the protrusion 20 and the groove 22 associated therewith makes it possible to generate a friction force that limits the vibrations of the platform 16 during the operation of the turbomachine.

[0053] According to one embodiment, the two platforms 16 are in contact with each other only via the protrusions 20 and the grooves 22 .

[0054] The protrusion 20 protrudes relative to the side surface 18 of the platform 16 of the first blade 12 according to the circumferential direction and in the direction of the platform 16 of the second blade 12. The protrusion 20 also extends in a plane substantially perpendicular to the radial direction, i.e. in a plane parallel to the main axis A and to the circumferential direction.

[0055] The projection 20 comprises a radially outer surface 24 oriented radially outwards, two side surfaces 26 considered in the axial direction, and an end surface 28 at the free circumferential end of the projection 20 .

[0056] The groove 22 also extends in a plane substantially perpendicular to the radial direction, ie in a plane parallel to the main axis A and parallel to the circumferential direction.

[0057] The groove opens circumferentially into the lateral surface 18 of the platform 16 of the second bucket 12 (this lateral surface facing the platform 16 of the first bucket 12 ) in order to accommodate the protrusion 20 carried by the first bucket 12 .

[0058] The groove 22 is also open radially inwardly.

[0059] The groove 22 thus comprises a bottom surface 30 oriented radially inwards, two side surfaces 32 considered according to the axial direction, and a circumferential end surface 34 .

[0060] According to a preferred embodiment, the protrusions 20 and recesses 22 are positioned generally axially in the middle of the platform 16 with which they are associated.

[0061] according to Figures 2 to 5 In the embodiment shown, the protrusion 20 is located radially in the plane of the remainder of the platform 16 of the first bucket 12 , and the recess 22 consists of a cavity formed in the platform 16 of the second bucket 12 .

[0062] like Figure 5 As shown in more detail in , the platform of the second bucket 12 comprises a boss 36 extending radially outwards and situated at the recess 22 of the platform 16. This boss is intended to locally increase the amount of material of the platform 16 and thus improve the mechanical strength of the platform.

[0063] according to Figure 6 and Figure 7 In another embodiment shown, the projection 20 projects radially outwards relative to the rest of the platform 16. The same applies to the groove 22 formed in the radial projection 38 projecting radially outwards relative to the rest of the platform 16 of the second bucket 12.

[0064] According to this other embodiment, the groove 22 is open circumferentially only at the side surface 18 of the platform 16 of the second bucket 12 , the side surface 18 of the platform 16 of the second bucket 12 facing the platform 16 of the first bucket 12 .

[0065] The radial thickness of the groove 22 is generally greater than the radial thickness of the protrusion 20 to enable the buckets 12 to be assembled with each other.

[0066] Preferably, in particular when the bucket 12 is made of CMC material, the protrusions 20 and the grooves 22 are manufactured by machining the platform.

[0067] During operation of the turbine, forces acting on the platforms 16, in particular centrifugal forces, cause deformation of these platforms, in particular leading to a radial movement of each protrusion 20 that is more significant than the radial movement of the rest of the blade 12 to which the protrusion 20 belongs, namely the first blade 12. This phenomenon is even more significant when the protrusion 20 is carried by the circumferential end of the soffit of the platform 16 of the first blade 12, relative to the flow direction of the gas flow (not shown) in the turbine.

[0068] As previously described, projections 20 carried by platform 16 of first bucket 12 are received in opposing recesses 22 formed in platform 16 of second bucket 12. Radial movement of projections 20 causes radially outer surfaces 24 of projections 20 to bear radially outwardly against bottom surfaces 30 of recesses 22.

[0069] Furthermore, during operation of the turbine, the platform 16 is subjected to vibrations, in particular in a plane perpendicular to the radial direction. The radial outer surface 24 of the protrusion 20 radially bears against the bottom surface 30 of the groove 22 to generate friction according to a direction perpendicular to the radial direction, thereby counteracting the vibrations of the platform 16.

[0070] Furthermore, when the protrusion 20 is received in the groove 22 , the two side surfaces 26 are positioned axially opposite to the side surfaces 32 of the groove 22 .

[0071] According to a preferred embodiment, there is an axial gap between the mutually opposing side surfaces 26 , 32 and during operation of the turbine, the protrusion 20 can come into contact with either of the two side surfaces 32 of the groove 22 to limit the amplitude of the relative vibration of the two platforms 16 .

[0072] According to a preferred embodiment, each platform 16 of the set of buckets 12 of the bucket assembly 10 comprises a protrusion 20 on a first circumferential side, preferably on the soffit side, and a recess 22 on the other circumferential side.

[0073] Therefore, each platform 16 cooperates with the two platforms 16 circumferentially adjacent to the platform 16 to limit vibration.

[0074] As a non-limiting example, the circumferential depth of the groove 22 (i.e., the distance between the side surface 18 to which the groove 22 leads and the circumferential end surface 34 of the groove 22) is greater than 2.5 mm to ensure sufficient damping while taking into account tolerances and operating clearances, and the circumferential depth of the groove 22 is less than 6 mm to ensure good mechanical strength of the platform 16.

[0075] According to another example, the circumferential length of the protrusions 20 and the grooves 22 is between 1 mm and 50% of the circumferential length of the platform 16 .

[0076] The axial width of the protrusion 20 (i.e., the axial distance between the side surfaces 26) is greater than 2.5 mm to ensure sufficient damping while taking into account tolerances and operating clearances, and the axial width of the protrusion 20 is less than 8 mm to ensure good mechanical strength of the protrusion 20. In any case, the axial width of the protrusion 20 is less than the axial length of the platform 16.

[0077] like Figure 3AAs shown, the protrusion 20 is generally inclined relative to the platform 16, more specifically relative to the side surface 18. The same applies to the groove 22, which is inclined relative to the side surface 18 of the platform 16 of the second bucket 12.

Claims

1. A turbine blade assembly (10), the turbine blade assembly extending about a main axis (A) and comprising at least one first blade (12) and one second blade (12) circumferentially adjacent to each other, Each of the first and second blades (12) comprises a blade (14) extending according to a radial extension direction relative to the main axis (A) and a platform (16), the platform being located at a free radial end of the blade (14), in, The platform (16) of the first bucket (12) includes a side surface (18) positioned circumferentially opposite an associated side surface (18) of the platform (16) of the second bucket (12), wherein, during operation of the turbine, the platform (16) of the first blade (12) is intended to come into contact with the platform (16) of the second blade (12) only via a projection (20), which projects circumferentially in the direction of the platform (16) of the second blade (12) relative to the lateral surface (18) of the platform (16) of the first blade (12), and 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 the radial direction relative to the main axis (A), and that the projection (20) comprises a radially outer surface (24) which is oriented radially outwards and which bears radially against a bottom surface (30) of the groove (22) which is oriented radially inwards, And wherein the protrusion (20) and the groove (22) are located substantially axially in the middle of the platform (16) associated with the protrusion and the groove.

2. The blade assembly (10) according to claim 1, characterized in that: The groove (22) formed in the second blade (12) and associated with the projection (20) of the first blade (12) opens circumferentially in the direction of the platform (16) of the first blade (12) to the side surface (18) of the platform (16) of the second blade (12).

3. The blade assembly (10) according to claim 1 or 2, characterized in that: The projection (20) of the first vane (12) includes at least one surface (24, 26) that bears against an opposing surface (30, 32) of the recess (22) of the second vane (12).

4. The blade 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 side surfaces (32) against which the projection (20) of the first blade (12) can bear axially.

5. The blade assembly (10) according to any one of claims 1 to 4, characterized in that: Each of the platform (16) of the first bucket (12) and the platform (16) of the second bucket (12) includes a protrusion (20) at a circumferential end and a groove (22) at the other circumferential end.

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

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