Shim for a turbomachine rotor, and associated turbomachine and rotor assembly

Abstract

The invention relates to a shim (2) for a moving blade (3), the moving blade (3) being intended to have a blade root (30) mounted in a slot (90) which opens onto the outer periphery of a turbomachine rotor disc (1) having a longitudinal axis (X), the shim (2) comprising a base (20) which is configured to be mounted in the slot (90) and which is configured to be mounted in contact with the blade root (30). According to the invention, the base (20) has at least one portion, referred to as an elastic portion, which is corrugated so as to apply a radial force towards the outside on the blade root (30) when the blade root (30) is resting on the base (20) mounted in the slot (90). Additionally, the base (20) has an upstream longitudinal end and a downstream longitudinal end configured to bear axially against one of the disc or the blade root (30).

Description

[0001] DESCRIPTION

[0002] TITLE: SHIM FOR TURBOMACHINE ROTOR, ROTOR ASSEMBLY AND ASSOCIATED TURBOMACHINE

[0003] Field of invention

[0004] The present invention relates to the field of turbomachines such as turboprops or turbojets.

[0005] More particularly, the invention relates to a wedge for a turbomachine rotor, as well as a rotor assembly equipping such a turbomachine.

[0006] State of the prior art

[0007] A turbomachine rotor, for example a rotor implemented in a low-pressure turbine extending around a longitudinal axis and conventionally comprises one or more rotor disks carrying on their outer periphery a plurality of moving blades. The moving blades have a radially internal part, or blade root, extended by a blade. These moving blades are housed at their root in cells which open onto the outer peripheral surface of the rotor disk.

[0008] The positioning of the blade roots in the cells of the rotor disks is done by translation along an axis substantially longitudinal to the axis of the turbomachine.

[0009] In order to facilitate the assembly of the moving blades on the rotor disks, it is necessary to provide sufficient clearance to allow easy sliding of the blade roots in the cells. There is therefore a relatively large clearance once the blade root has been assembled in the cell, which can be detrimental to the proper operation of the turbomachine. Indeed, and particularly when stopped, the moving blades can move in radial translation and can therefore shift towards the engine axis of the turbomachine. The same is true when the turbomachine is operating but at reduced speed.

[0010] It is thus known to implement means for radially retaining the moving blades relative to the rotor disk in order to ensure this maintenance in radial position of each of the moving blades in the cells of the rotor disk and to prevent them from falling towards the axis of the turbomachine when the latter is not in operation, or is operating at reduced speed.

[0011] Documents FR 2994 211 and FR 3 072 122 present such moving blades equipped with stilts so as to limit their radial movements towards the axis of revolution of the engine or towards the outside when they are housed in the cells of the rotor disk. Such stilts may in particular comprise walls coming into abutment against the teeth formed between two successive cells, thus allowing the position of the moving blades to be maintained radially.

[0012] However, a disadvantage of such stilts is that they have shapes that are relatively complex to produce, and therefore represent a significant impact in terms of cost and production time of the moving blades.

[0013] Furthermore, the implementation of such stilts turns out to be even more complex when the moving blades are at least partially composed of ceramic matrix composite material.

[0014] There is therefore a need to provide another solution to secure the positioning of the moving blades on the rotor discs, and in particular to ensure the radial retention of the moving blades relative to the rotor disc.

[0015] Statement of the invention

[0016] The invention aims to remedy at least in part the drawbacks mentioned above relating to the prior art.

[0017] To do this, the invention relates to a shim for a moving blade intended to have a blade root mounted in a cell which opens at the external periphery of a turbomachine rotor disk of longitudinal axis X, the shim comprising a base configured to be mounted in the cell and which is configured to be mounted in contact with the blade root.

[0018] According to the invention, said base has at least one so-called elastic portion which is corrugated so as to apply a radial force towards the outside on said blade root when the blade root rests on the base mounted in the cell. In addition, the base has an upstream longitudinal end and a downstream longitudinal end configured to come into axial support against one of the disc or the blade root.

[0019] Thus, the invention proposes a solution making it possible to resolve at least in part certain of the drawbacks of the prior art.

[0020] In particular, by implementing an element external to the moving blade having the function of ensuring the retention of the moving blade relative to the cell of the rotor disk, the geometry of the moving blade is simplified, which allows a saving of time for the production of such a moving blade, as well as savings in material.

[0021] Furthermore, the invention allows radial retention of the moving blades which is adaptable to all types of moving blades, regardless of the material from which the moving blades are made.

[0022] Finally, the invention makes it possible to have a solution which is mechanically simple and inexpensive to implement, while being technically reliable. According to a particular aspect of at least one embodiment of the invention, the shim comprises an upstream tab extending from said upstream longitudinal end of said base and / or a downstream tab extending from said downstream longitudinal end of said base, said upstream and downstream tabs forming means for axially stopping a blade relative to the disc.

[0023] This makes it possible to implement simple and inexpensive upstream or downstream axial stopping means.

[0024] According to a particular aspect of at least one embodiment of the invention, said upstream tab extends in a radial direction of said turbomachine and / or said downstream tab extends in a radial direction of said turbomachine.

[0025] In other words, according to a particular aspect of at least one embodiment of the invention, said upstream tab extends in a direction orthogonal to the axial direction of said turbomachine and / or said downstream tab extends in a direction orthogonal to the axial direction of said turbomachine.

[0026] In this way, the axial stop means can be kept in contact with the rotor disc.

[0027] According to a particular aspect of at least one embodiment of the invention, said elastic portion extends longitudinally in the center of said base.

[0028] This allows for a radial force exerted by the wedge on the blade root which is relatively balanced so as not to have a tilting of the moving blade upstream or downstream.

[0029] The invention also relates to a rotor assembly for a turbomachine comprising a rotor disk carrying a plurality of moving blades housed at their blade root in cells which open at the external periphery of said disk, the assembly further comprising a plurality of shims according to one of the aforementioned embodiments, each of the shims being arranged between the blade root and the bottom of one of said cells.

[0030] According to a particular aspect of at least one embodiment of the invention, said base has a length taken along the longitudinal axis substantially equal to the length taken along the longitudinal axis of each of said cells.

[0031] According to a particular aspect of at least one embodiment of the invention, said base has a single undulation which extends from the upstream longitudinal end to the downstream longitudinal end and is in contact with said blade root at the upstream and downstream longitudinal ends of the base. In addition, the base is in contact with the bottom of said cell at a longitudinally central portion. According to a particular aspect of at least one embodiment of the invention, the rotor assembly further comprises a plurality of foils, each arranged between one of said blade roots and one of said shims.

[0032] According to a particular aspect of at least one embodiment of the invention, at least one of said blades is at least partially composed of ceramic matrix composite material.

[0033] The invention also relates to a turbomachine for aircraft comprising a rotor assembly according to one of the aforementioned embodiments.

[0034] According to a particular aspect of at least one embodiment, the turbine is a turbojet.

[0035] Presentation of figures

[0036] The invention, as well as the various advantages that it presents, will be more easily understood in the light of the following description of an illustrative and non-limiting embodiment thereof, and of the appended drawings among which:

[0037] [Fig. 1] is a schematic sectional view of a turbomachine;

[0038] [Fig. 2] is a sectional view of a portion of a turbomachine rotor assembly;

[0039] [Fig. 3] is a detailed view of area A of Figure 2;

[0040] [Fig. 4] is a perspective view of a portion of a turbomachine rotor assembly, and [Fig. 5] is another sectional view of a turbomachine rotor shim according to one embodiment of the invention.

[0041] Detailed description of an embodiment of the invention

[0042] It should be noted that the invention applies to any type of turbomachine, and in particular to aircraft turbomachines.

[0043] This turbomachine 1, which extends along an axis X, is for example intended to be mounted on an aircraft (not shown), such as an airplane or a helicopter, for example under the wing of the aircraft, on the wing or even at the rear of the fuselage of the aircraft.

[0044] The turbomachine 1 illustrated in Figure 1 is a twin-spool, twin-flow, direct-drive turbojet engine. This is not, however, limiting since the turbomachine 1 may not be intended to be mounted on an aircraft, may be another type of turbojet engine, such as a geared turbojet engine, a turboprop engine or an auxiliary power unit (also called "APU", for "Auxiliary Power Unit").

[0045] Throughout the description, an axial direction corresponds to the direction of the longitudinal axis X and a radial direction is a direction perpendicular to the longitudinal axis X and intersecting the longitudinal axis X. Similarly, an axial plane is a plane containing the longitudinal axis X and a radial plane is a plane perpendicular to the longitudinal axis X.

[0046] Similarly, the adjectives "inner" (or "internal") and outer ("or external") are used with reference to a radial direction so that the inner part of an element is, in a radial direction, closer to the longitudinal axis X than the outer part of the same element. In addition, unless otherwise specified, the terms "upstream" and "downstream" are used with reference to the overall direction of gas flow through the turbomachine in operation.

[0047] As visible in Figure 1, the turbomachine 1 comprises, from upstream to downstream, a fan 10, a compressor section 12, a combustion chamber 14 and a turbine section 16. The longitudinal axis X forms the axis of rotation of at least a portion of the compressor section 12 and of the turbine section 16, which are capable of being driven in rotation around the longitudinal axis X relative to a casing 18 of the turbomachine 1.

[0048] In operation, the fan 10 sucks in an air flow, a portion of which, circulating within a primary vein 100, is successively compressed within the compressor section 12, ignited within the combustion chamber 14, and expanded within the turbine section 16 before being ejected from the turbomachine 1. In this way, the turbomachine 1 generates thrust. This thrust can also, for example, be used for the benefit of the aircraft on which the turbomachine 1 is attached and fixed.

[0049] Compressors and turbines comprise an alternation of mobile discs mounted to rotate around the longitudinal axis X of the turbomachine, called rotor discs, and fixed discs, called stator discs.

[0050] Each rotor disk assembly comprises a plurality of cells 90 hollowed out on their peripheral surface and which open at the outer periphery of the disk. These cells are intended to each accommodate a moving blade, and more particularly a blade root 30, such that each rotor disk carries a plurality of moving blades, each moving blade being intended to have a blade root mounted in one of the cells which opens at the outer periphery of the rotor disk.

[0051] In the embodiment presented below, the moving blades are preferably at least partially composed of ceramic matrix composite material.

[0052] Due to the difference in dimensions between each cell and each blade root, in particular to facilitate assembly and make translation of the blade root possible in the cell, the blade root is not completely held radially in the cell, and there remains at least one space 8 between the bottom of the cell 90 and the blade root 30. As a result, the assembly further comprises a plurality of shims mounted in the cells 90, and arranged between the blade root 30 and the bottom of one of the cells 90.

[0053] These shims can, for example, be made at least partially from a metal or a metal alloy.

[0054] An embodiment of the invention is now presented in relation to Figures 2 to 5. As illustrated, the wedge 2 for the turbomachine rotor 1 comprises a base 20. This base is intended to be housed in a space 8 formed between a cell 90 hollowed out on the outer peripheral surface of a rotor disc 9 and a blade root 30 housed in the cell 90, and to come into contact with the blade root 30 and the disc

[0055] In the illustrated embodiment, the base 20 has a length taken along the longitudinal axis, or axial length, substantially equal to the axial length of each of the cells 90.

[0056] In this way, the implementation of the shims does not disrupt the proper functioning of the rotor assembly.

[0057] According to the invention, the base 20 has at least one elastic portion which is corrugated so as to apply a radial force towards the outside on the blade root 30.

[0058] This radial force exerted by the base on the blade root thus ensures radial support of the moving blade in the cell and prevents the moving blade from shifting radially or even sinking into the cell.

[0059] This prevents overlapping or dislocation of moving blades when they are positioned in the cells.

[0060] Furthermore, and so as to amplify the radial retention of the moving blade in the cell and to stabilize this retention, the base 20 has an upstream longitudinal end and a downstream longitudinal end configured to come into axial support against one of the disk or the blade root 30.

[0061] Here, the upstream and downstream longitudinal ends bear against the blade root 30. However, an embodiment could be provided in which the upstream and downstream longitudinal ends bear against the disc, for example at the level of an axial face of the disc or at the level of the bottom of the cell.

[0062] It would also be possible to provide an embodiment in which the upstream longitudinal end bears axially against one of the bottom of the cell or the blade root, and the downstream longitudinal end bears axially against the other of the bottom of the cell or the blade root.

[0063] The base 20 therefore has an elasticity which allows the shim to deform during assembly in order to then apply a pushing force, i.e. a force towards the outside of the turbomachine. More particularly in this embodiment, and as can be seen in particular in FIG. 2, the elastic portion extends in the center of the base 20, so that the shim provides a radial force which is relatively balanced and prevents the moving blade from tilting upstream or downstream. However, embodiments could be provided in which the elastic portion would be offset towards the upstream longitudinal end or the downstream longitudinal end so as to compensate for a distribution of mass or force of the moving blade.

[0064] This elastic portion therefore corresponds here to a central portion which is here, as visible for example in figure 3, in contact with the bottom of the cell 90, while the base 20 is in contact with the blade root 30.

[0065] As illustrated in this embodiment, the wedge 2 further comprises axial stop means in the form of an upstream tab 21 and a downstream tab 22.

[0066] The upstream tab 21 extends here from an upstream end of the base 20 and extends in a radial direction of the turbomachine, more particularly radially towards the inside of the turbomachine.

[0067] Furthermore, the wedge 2 also comprises a downstream tab 22 extending from a downstream end of the base 20. This downstream tab 22 extends here in a radial direction of the turbomachine, and more particularly radially towards the outside of the turbomachine.

[0068] However, since the orientation of the tabs depends in particular on the implementation of an upstream or downstream flange at the level of the rotor disk, another embodiment could be provided in which the upstream tab would extend radially towards the outside of the turbomachine and the downstream tab would extend radially towards the inside of the turbomachine.

[0069] Because the base 20 has an axial length substantially equal to the axial length of each of the cells 90, the upstream 21 and downstream 22 tabs in this embodiment are in contact with the rotor disk 9.

[0070] These tabs here form axial stopping means for the moving blade, respectively upstream and downstream, and ensure that the moving blade does not shift axially relative to the cell of the rotor disk.

[0071] As illustrated in particular in figures 3 and 4, the rotor assembly for a turbomachine further comprises a plurality of foils 4.

[0072] Each of these foils 4 is here arranged between one of the blade roots 30 and one of the shims 2. More particularly, each foil 4 is here mounted so as to be in contact with the blade root and to form a layer making it possible to protect the blade root against wear and deformation.

[0073] As a result, the base exerts a radial force on the blade root via the foil which is positioned between the two components, the blade root therefore being in indirect contact with the shim. As illustrated in particular in FIG. 2, each foil 4 comprises a foil base configured to be in contact with a lower face of the blade root 30, and two lateral fins configured to be in contact with lateral surfaces of the blade root.

[0074] In other words, each foil 4 has a substantially U-shape with two fins connected by a foil base.

[0075] It should be noted that, as visible in Figure 2, the contact surface between the blade root 30 and the foil 4, the connection angles between each fin and the base of the foil have a rounded shape.

[0076] As can be seen in the various figures, the base of the foil is in contact with the base 20 of the wedge so that the base 20 of the wedge 2 applies a radial force towards the outside on said blade root 30 and therefore on the base of the foil 4.

[0077] More precisely, in this embodiment the elastic portion of the base 20, which therefore extends longitudinally in the center of the base 20, applies a radial force towards the outside of the central portion of the base of the foil 4.

[0078] As for the upstream and downstream longitudinal ends of the base 20, they are, in this embodiment, in abutment against upstream and downstream longitudinal ends of the base of the foil 4.

Claims

CLAIMS

1. Rotor assembly for a turbomachine comprising a turbomachine rotor disc (9) (1) with a longitudinal axis (X), said rotor disc (9) carrying a plurality of movable blades (3) each having a blade root (30) mounted in a cell (90) which opens at the outer periphery of said rotor disc (9), the assembly further comprising a plurality of shims (2), each of said shims (2) comprising a base (20) arranged between the blade root (30) and the bottom of one of said cells (90), said base (20) having at least one so-called elastic portion which is corrugated so as to apply a radial force towards the outside on said blade root (30) when the blade root (30) rests on the base (20) mounted in the cell (90), the base (20) having an upstream longitudinal end and a downstream longitudinal end configured to come into axial support against one of the disc or the foot of the blade (30),said base (20) having a length taken along the longitudinal axis substantially equal to the length taken along the longitudinal axis of each of said cells (90), said base (20) having a single undulation which extends from the upstream longitudinal end to the downstream longitudinal end and is in contact with said blade root (30) at the upstream and downstream longitudinal ends of the base (20) and in that the base (20) is furthermore in contact with the bottom of said cell (90) at a longitudinally central portion of the base (20).,

2. Assembly (2) according to claim 1, characterized in that said wedge comprises an upstream tab (21) extending from said upstream longitudinal end of said base (20) and / or a downstream tab (22) extending from said downstream longitudinal end of said base (20), said upstream (21) and downstream (22) tabs forming means for axially stopping a blade relative to the disc.

3. Assembly (2) according to the preceding claim, characterized in that said upstream tab (21) extends in a radial direction of said turbomachine and / or said downstream tab (22) extends in a radial direction of said turbomachine.

4. Assembly (2) according to one of the preceding claims, characterized in that said elastic portion extends longitudinally in the center of said base (20).

5. Rotor assembly for a turbomachine according to one of the preceding claims, characterized in that it further comprises a plurality of foils (4), each arranged between one of said blade roots (30) and one of said shims (2).

6. Rotor assembly for a turbomachine according to one of the preceding claims, characterized in that at least one of said blades (3) is at least partially composed of ceramic matrix composite material.

7. Turbomachine comprising a rotor assembly according to one of claims 1 to 6.

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