Bladed turbine assembly comprising means for limiting vibrations 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) at a free radial end of the vane (14), the platform (16) of each blade (12) of the bladed assembly (10) is positioned circumferentially facing the platform (16) of another circumferentially adjacent blade (12) of the bladed assembly (10), where the bladed assembly (10) comprises an insert (20) circumferentially arranged between and cooperating with the platforms (16), each platform (16) comprising a circumferential bearing surface (32), one circumferential end of the insert (20) is in contact with circumferential bearing surfaces (32), the direction of contact between each circumferential bearing surface (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 two platforms (16), the means comprising at least one finger (36) carried by the insert (20), a finger (36) protrudes circumferentially from the insert (20) and is received in an associated recess (38) formed circumferentially as a recess in at least one of the platforms (16), the at least one finger (36) and the associated recess (38) being designed such that the insert (20) can move relative to the platforms (16) in a radial direction.

Description

Technical Field

[0001] The present invention relates to a bladed turbine assembly which is designed to achieve vibration damping of the outer radial ends of moving blades by cooperating with each other.

[0002] The purpose of the present invention is to replace the existing solutions related to assembling blades with prestressing during installation. Background Art

[0003] During operation of the turbomachine, the blades, in particular the moving blades, are subject to various vibrations.

[0004] These vibrations are typically strongest at the outer radial end of each blade, 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 torsional prestressing of the blades.

[0006] During operation of the turbomachine, the above-mentioned prestressing forces associated with the specific installation generate frictional stresses making it possible to reduce the amplitude of the vibrations.

[0007] This mounting involves specific shaping of the platforms of the blades so as to interlock in a predetermined manner.

[0008] However, due to rotation of the blade in one direction or the other, or changes in the relative positions of the platforms of the blade, the contact stresses between the platforms may vary, which may prevent damping of vibrations.

[0009] Furthermore, in the case of blades made of ceramic matrix composite (CMC) materials, this material does not allow for as great a torsional prestress as other materials. This prestressing induces strong static stresses that may exceed the stresses that the material can withstand.

[0010] The object of the present invention is to propose a bladed turbine assembly which is designed in such a way that vibrations can be damped by friction without requiring prestressing of the blades during installation. Summary of the invention

[0011] The invention proposes a bladed turbine assembly, which extends around a main axis A and comprises at least two circumferentially adjacent blades.

[0012] Each blade comprises an airfoil extending according to a radial extension direction relative to said main axis A and a platform located at a free radial end of the airfoil,

[0013] wherein the platform of each blade of the bladed assembly is positioned circumferentially facing the platform of another circumferentially adjacent blade of the bladed assembly,

[0014] wherein the bladed assembly includes an insert that is circumferentially arranged between the platforms and cooperates with the platforms,

[0015] characterised in that each platform comprises a circumferential bearing surface against which the circumferential end of the insert comes into contact,

[0016] And the direction of contact between each circumferential bearing surface and the insert is oriented circumferentially relative to the main axis A.

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

[0018] Preferably, the circumferential bearing surface is in the shape of an arc of a circle or is inclined with respect to the radial direction.

[0019] Preferably, the circumferential bearing surface of the platform is parallel to a radial direction relative to the main axis A.

[0020] Preferably, the circumferential bearing surface comprises a groove.

[0021] Preferably, the insert comprises two contact surfaces, each of the two contact surfaces having a shape complementary to the shape of the bearing surface with which it is associated.

[0022] Preferably, at least one contact surface of the insert is in the shape of an arc of a cylinder, the axis of which is parallel to the main direction of the insert.

[0023] Preferably, each circumferential end of the insert is received in a groove associated with that circumferential end with radial play and circumferential play.

[0024] Preferably, each platform comprises a boss having a radial thickness greater than the thickness of the rest of the platform, and the groove is formed in the boss.

[0025] Preferably, the bladed assembly comprises means for retaining the insert axially between the two platforms.

[0026] Preferably, the axial retaining 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 circumferentially in the form of a recess in at least one of the platforms.

[0027] The invention also proposes an aircraft turbomachine comprising a bladed assembly according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] [ Figure 1 ] is an end view of a bladed turbine assembly according to a radial direction relative to the main axis of the bladed assembly.

[0029] [ Figure 2 ] is based on the plane perpendicular to the main axis of the bladed assembly Figure 1 A cross section of a bladed assembly is shown in .

[0030] [ Figure 3 ] is related to Figure 2 A similar view of FIG. 4 shows another relative position of the insert relative to the platform when the platform is expanded.

[0031] [ Figure 4 ] is related to Figure 1 A similar view of FIG. 1 shows an alternative embodiment of the insert.

[0032] [ Figure 5 ] is related to Figure 2 A similar view of the view shows Figure 4 A cross section of a bladed assembly is shown in .

[0033] [ Figure 6 ] is a cross-section of a bladed assembly taken in the circumferential direction, showing a first embodiment of a device for retaining an insert.

[0034] [ Figure 7 ] is related to Figure 6 A similar cross section shows another embodiment of the retaining device.

[0035] [ Figure 8 ] is a partial view of a turbine rotor element equipped with a bladed assembly according to the present invention. DETAILED DESCRIPTION

[0036] The figure shows a portion of a bladed turbine assembly 10 comprising two circumferentially adjacent blades 12. Preferably, the turbine comprising the bladed assembly 10 is an aircraft turbine.

[0037] The bladed assembly 10 is preferably a rotor disk (eg a rotor disk DR, a portion of which is located at Figure 8 Thus, the blades 12 can be mounted in corresponding cells of the disk DR by the root of the blades, while forming a ring of blades 21a, 21b that surround the disk DR while being carried by the disk.

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

[0039] The bladed assembly 10 has a main axis A which is intended to be identical or coaxial with the main axis of the turbine when the bladed assembly 10 is installed in the turbine.

[0040] Each blade 12 comprises an airfoil 14 extending in a radial direction relative to the main axis, a first radial end portion 15 , which is referred to as a root and is connected to a first radial end of the airfoil 14 , and a second radial end portion 16 , which is referred to as a platform and is connected to a second radial end of the airfoil 14 .

[0041] Preferably, the platform 16 is connected to the free radial end of the airfoil 14 , ie the radial end of the airfoil 14 that is not fastened to a rotating element supporting the blade 12 .

[0042] Thus, according to the embodiment shown in the figures, the platform 16 is located at the outer radial end of the airfoil 14. The inner radial end of the airfoil 14 carries the root 15 of the blade 12, by which the blade is mounted on the support element. Figure 8 As shown and as a preferred but non-limiting example, the root 15 of the blade 12 is mounted in a cell 17 of a disk DR of a rotor of a turbomachine.

[0043] The outer radial end of the blade 12 , opposite the root 15 for fastening the blade 12 to the rotor, also comprises a sealing strip (not shown).

[0044] The bladed assembly 10 shown in the drawings is composed of two blades 12 which are circumferentially adjacent to each other in a turbomachine.

[0045] In particular, the platforms 16 of the blades 12 are positioned close to each other according to the circumferential direction.

[0046] Each platform 16 comprises a side surface 18, which is positioned to face and be located at a distance from the side surface 18 of the platform 16 of the circumferentially adjacent blade circumferentially. Here, the two side surfaces 18 facing each other are parallel to each other and inclined relative to a plane passing through the main axis of the bladed assembly 10.

[0047] The bladed assembly 10 further comprises an insert 20 which is circumferentially arranged between the platforms of two circumferentially adjacent blades 12 and cooperates with both platforms 16 simultaneously, so that when vibrations are generated on the blades 12 , friction occurs between the insert 20 and the platforms 16 to reduce the amplitude of the vibratory movement of the platforms 16 .

[0048] Preferably, the insert 20 cooperates with the platform 16 to reduce vibration.

[0049] To this end, each side surface 18 of one of the two platforms 16 comprises a bearing surface 32 against which the insert 20 bears. Furthermore, the bearing of the insert 20 on the bearing surface 32 is oriented at least partially circumferentially relative to the main axis A.

[0050] Thus, at least one bearing surface 32 against which the insert 20 bears is inclined with respect to the radial direction.

[0051] To this end, the side surface 18 of at least one platform 16 comprises a groove 22 which receives the circumferential end associated with the groove of the insert 20. This groove 22 comprises a surface forming a bearing surface 32 of the platform and is open according to the circumferential direction in the direction of the platform 16 of the other blade 12.

[0052] The bearing surface 32 is a radially outer surface of the groove 22 which is partly oriented radially inwards, ie towards the main axis A, and partly oriented circumferentially in the direction of the further platform 16 .

[0053] according to Figures 1 to 3 In the first embodiment shown, the bearing surface 32 of one of the two platforms 16 (here the right-hand platform 16 ) extends in a plane parallel to the radial direction. The bearing of the insert 20 against this bearing surface 32 is therefore oriented completely circumferentially relative to the main axis A.

[0054] According to this first embodiment, only the support surface 32 of the other platform 16 , here the left-hand platform 16 , comprises a recess 22 with a support surface 32 .

[0055] Thus, according to this embodiment, the insert 20 is compressed circumferentially between the two bearing surfaces 32 of the two platforms 16 and it bears radially outwards against the bearing surface 32 of the left-hand platform which partially defines the groove 22 .

[0056] During operation of a turbomachine arranged with the bladed assembly 10 , the bearing of the insert 20 against the inclined bearing surface 32 results in a bearing of the insert 20 according to a circumferential direction against a further bearing surface 32 oriented radially.

[0057] By means of this circumferential bearing, friction stresses are generated between the insert 20 and the bearing surface 32 , thereby reducing vibrations of two circumferentially adjacent platforms 16 .

[0058] like Figure 3 As shown, the inclination of the bearing surfaces also makes it possible to compensate for dimensional changes of the blade 12 caused by the expansion of the blade. During the expansion of the blade 12, the circumferentially adjacent platforms 16 move circumferentially away from each other. Since at least one of the bearing surfaces 32 is inclined relative to the radial direction, the insert 20 moves radially relative to the main axis A while maintaining contact with the two bearing surfaces 32, even if the platforms 16 move circumferentially away from each other (that is, the bearing surfaces 32 move circumferentially away from each other).

[0059] The vibration damping function is therefore retained.

[0060] according to Figure 4 and Figure 5 In another embodiment shown, the side surface 18 of each platform 16 comprises a groove 22 which receives the circumferential end associated with the groove of the insert 20. This groove 22 comprises a surface forming a bearing surface 32 of the platform and is open according to the circumferential direction in the direction of the platform 16 of the other blade 12.

[0061] The bearing surface 32 is a radially outer surface of the groove 22 which is partly oriented radially inwards, ie towards the main axis A, and partly oriented circumferentially in the direction of the further platform 16 .

[0062] The insert 20 comprises contact surfaces 34 intended to bear against the bearing surfaces 32 of the platform 16. Each contact surface 34 has a shape complementary to that of the bearing surface 32 to which it is associated. The contact surfaces 34 and the bearing surfaces 32 to which they are associated are arranged circumferentially facing each other.

[0063] Therefore, according to Figure 1 and Figure 2 In the embodiment shown, the contact surface 34 is partially oriented radially outwards, that is to say in a manner moving away from the main axis A, and partially oriented circumferentially in the direction of the platform 16 associated with the contact surface 34. The other contact surface 34 extends in a plane parallel to the radial direction, so that the bearing of the insert 20 against the associated bearing surface 32 is completely oriented circumferentially relative to the main axis A.

[0064] according to Figure 4 and Figure 5 In the embodiment shown, each of the two contact surfaces 34 is oriented partially radially outwards, that is to say in a manner displaced away from the main axis A, and partially circumferentially in the direction of the platform 16 with which the contact surface 34 is associated.

[0065] Whatever the embodiment, in order to enable the platforms 16 to move relative to each other, in particular due to the expansion of the blades 12, the insert 20 is received with clearance in the groove 22 or in the two grooves 22. Preferably, each circumferential end of the insert 20 is received in each of the two grooves 22 with radial and circumferential clearance.

[0066] To this end, the radial dimensions and the circumferentially measured depth of each groove 22 are greater than the radial thickness of the insert 20 and the circumferential length of the portion of the insert received in each groove 22 .

[0067] To compensate for this expansion difference, and according to Figure 5 In the alternative embodiment shown in , the contact surface 34 of the insert 20 is curved radially outwards. Preferably, the contact surface 34 of the insert 20 is in the shape of an arc of a cylinder whose axis is parallel to the substantially axial main direction of the insert 20.

[0068] In addition to this curved shape of the insert 20 , the bearing surface 32 of each groove 22 is also curved and in the shape of an arc of a cylinder whose axis is parallel to the substantially axial main direction of the lateral surface 18 .

[0069] Preferably, the radius of the cylinder associated with each bearing surface 32 of the groove 22 is greater than the radius of the cylinder associated with the contact surface 34 of the insert 20 .

[0070] Through these convex shapes of the facing walls and surfaces, the contact between the insert 20 and each platform 16 is distributed as a cylinder-cylinder contact, i.e. a contact distributed over the entire length of the insert 20, regardless of the deformation of one and / or the other of the blades 12 and the movement of the platform 16 of the blade.

[0071] To accommodate each groove 22, the platform 16 comprises a boss 28, ie comprises radial extra thickness. The result of this extra thickness is an increase in the mass of the platform 16. Thus, the greater the length of the insert 20 or the associated groove 22, the greater the mass of the platform 16.

[0072] according to Figure 6 and Figure 7 In another aspect of the invention shown, the bladed assembly 10 comprises means for retaining the insert 20 axially between the two platforms 16 .

[0073] According to a first embodiment, the axial length of the insert 20 and of the groove 22 associated with it is smaller than the axial length of the platform 16, and the groove 22 does not open to each axial end of the platform 16. The insert 20 can therefore be axially stopped against the axial ends of the groove 22 in which it is partially housed.

[0074] according to Figure 7 In the second embodiment shown, these axial retaining means are constituted by fingers 36 which project circumferentially relative to the rest of the insert 20 and are received in associated notches 38 made in the platform 16 .

[0075] The fingers 36 and the recesses 38 are designed to enable relative movement of the insert 20 with respect to the platform 16 according to a radial direction.

[0076] The platform 16 and its functional surfaces, ie the bosses 28 , the side surfaces 18 and the walls of the grooves 22 , are made of a ceramic matrix composite (CMC) by weaving, molding and then optionally machining the functional parts.

[0077] The insert 20 is made of, for example, a refractory metal material containing nickel or cobalt or of an integral or fiber-reinforced ceramic material. It should be understood that the material forming the insert is not limited to these examples, and other materials may be used to adapt to the selected application in terms of temperature resistance and mass reduction while maintaining the insert 20 and generating the desired damping level.

Claims

1. A bladed turbine assembly (10) extending about a main axis (A) and comprising at least two circumferentially adjacent blades (12), Each blade (12) comprises an airfoil (14) extending according to a radial extension direction relative to said main axis A and a platform (16) located at a free radial end of said airfoil (14), in, The platform (16) of each blade (12) of the bladed assembly (10) is positioned circumferentially facing the platform (16) of another circumferentially adjacent blade (12) of the bladed assembly (10), The bladed assembly (10) comprises an insert (20) which is circumferentially arranged between the platforms (16) and cooperates with the platforms (16). wherein each platform (16) comprises a circumferential bearing surface (32) against which the circumferential end of the insert (20) comes into contact, and the direction of contact between each circumferential bearing surface (32) and the insert (20) is oriented circumferentially relative to the main axis A, characterized in that the bladed turbine assembly includes a device for axially retaining the insert (20) between two platforms (16), the device comprising at least one finger (36) carried by the insert (20), the finger protruding circumferentially from the insert (20), and the finger being received in an associated recess (38) formed circumferentially in the form of a recess in at least one of the platforms (16), the at least one finger (36) and the associated recess (38) being designed so that the insert (20) can move relative to the platform (16) according to a radial direction.

2. The bladed assembly (10) according to claim 1, characterized in that: At least one of the two platforms (16) comprises a groove (22) which is circumferentially open toward the other of the two platforms (16), one surface of the groove (22) of at least one of the two platforms forms the circumferential support surface (32), and the circumferential end of the insert (20) is received in the groove (22).

3. The bladed assembly (10) according to claim 1 or 2, characterized in that: The circumferential support surface (32) is in the shape of an arc of a circle or is inclined relative to the radial direction.

4. A bladed assembly (10) according to any one of the preceding claims, characterised in that The circumferential bearing surface (32) of the platform (16) is parallel to a radial direction relative to said main axis A.

5. The bladed assembly (10) according to any one of claims 1 to 3, characterized in that: The circumferential bearing surface (32) includes a groove (22).

6. A bladed assembly (10) according to any one of the preceding claims, characterised in that The insert (20) comprises two contact surfaces (34), each of which has a shape complementary to the shape of a bearing surface (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 surface (34) of the insert (20) is in the shape of an arc of a cylinder, the axis of which 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 in a groove (22) associated with the circumferential end with radial play and circumferential play.

9. A bladed assembly (10) according to any one of the preceding claims, characterised in that Each platform (16) includes a boss (28) having a radial thickness greater than the thickness of the remaining portion of the platform (16), and the groove (22) is formed in the boss (28).

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

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