Shim for turbomachine turbine disk, turbomachine rotor assembly, turbomachine rotor, turbomachine and method for assembly of a turbomachine rotor assembly

Abstract

The invention relates to a shim (400) for a turbine engine turbine disc (40), comprising a metal sheet forming an envelope that at least partially surrounds a tooth (42) of the turbine disc, the tooth separating a first and a second cavity (41) of the disc, each cavity being adapted to receive a root (20) of a movable blade (10) of the turbine. The envelope is adapted to at least partially cover: - each of the side walls (44) of the tooth, and - a downstream rim (46) of the tooth (42). The invention also relates to an assembly for a turbine engine rotor, to a turbine engine rotor, and to a method for installing a turbine engine rotor assembly.

Description

DOMAINE TECHNIQUE DE L'INVENTION

[0001] The present invention relates to a shim for a turbomachine turbine disc. It also relates to a rotor assembly comprising such a shim mounted around a tooth of the disc. Furthermore, it relates to a method for mounting this assembly. Finally, it relates to a turbomachine rotor comprising a plurality of this assembly, as well as a turbomachine comprising a plurality of this assembly.

[0002] The invention has applications in the field of aeronautics and, in particular, in the field of turbomachine rotors to protect both the blade root and the disc rim and increase the lifespan of the rotors. ARRIERE-PLAN TECHNOLOGIQUE DE L'INVENTION

[0003] FR2981132A1, FR2918702A1 and US629046681 disclose prior art.

[0004] It is known in aeronautics that a rotor blade 10, an example of which is shown on the figure 1 The assembly comprises a blade 12 having, at its lower end, a platform 11 extended radially by a foot 20 intended to be inserted into a cavity formed in the outer periphery of a rotor disc. The foot 20 of the rotor blade 10 – also called the movable blade – is retained radially in the disc cavity by a cohesive fit between the foot, generally dovetail-shaped, and the cavity, generally hollow-shaped. At its upper end, the blade 12 has a heel 13 intended to be arranged edge-to-edge with the heels of adjacent movable blades so as to form a rotating circumferential ring defining a surface of revolution around the axis of rotation X of the disc.

[0005] During rotor operation, the contact between the feet of the moving blades (more simply called blade feet), which are for example made of titanium aluminide, and the disc, which is for example made of nickel-based alloy, causes premature wear of the blade feet and / or the cavities of the disc.

[0006] To limit wear on the blade roots and the disk cavities, it is known to place a contact piece 30, called a shim, at the contact interfaces, commonly referred to as bearing surfaces, between the blade roots and the disk cavities. Typically, the shim is a shim for a moving blade, mounted around the root 20 of said moving blade. This shim, referenced as 30, is in contact with the disk and absorbs a major part of the energy dissipated by friction in the contact between the root of the moving blade and the disk, thus limiting wear on the blade root.

[0007] There figure 2 represents, in an enlarged form, foot 20 of the movable blade 10 of the figure 1 , around which is mounted a conventional sash 30. This sash 30 has a generally U-shaped cross-section, formed by two lateral branches 32, or lateral surfaces (only one of which is visible on the figure 2 ), intended to cover the lateral sides 22 of the foot 20 of the movable blade 10 and to hold the shim 30 on the blade foot 20. The shim 30 also has a base 31, also called the lower surface, which connects the lateral surfaces 32 to each other and covers the lower face 21 of the blade foot 20.

[0008] The 30mm shim therefore serves to protect the blade root and the disc cavity by preventing wear on these parts. It thus guarantees the mechanical integrity of the parts (blade root and disc) with which it is in contact.

[0009] To prevent the shim 30 from disengaging from the blade foot 20, the lower surface 31 of the shim generally includes radial tabs 33 bearing against the upstream 23 and downstream 24 faces of the foot 20. The radial tabs 33 (only one of which is visible on the figure 2 ) are strips cut at the end of the lower surface 31 and folded radially along the upstream and downstream faces 23, 24 of the blade foot 20. These radial strips 33 extend over a greater or lesser width, between the lateral branches 32 of the shim, and form stops which prevent relative axial movements between the blade foot 20 and the shim 30.

[0010] However, despite the presence of the radial tabs 33, turbomachine maintenance operators have observed that the shims tend to move axially, damaging and even severing the radial tabs 33. Indeed, due to their radial bending during the manufacturing phase and / or their unbending during the assembly phase, the radial tabs are weakened, and the friction generated by the repeated axial movement of the shims causes them to sever or break. Once the radial tabs are broken, the shims 30 can partially or even completely disengage from the blade roots 20, as shown in the figure 3 .

[0011] The disengagement of one (or more) shims 30 can lead to the release of the shims into the turbomachine's air stream and damage the blades located downstream of the Low Pressure Turbine, particularly the titanium aluminide (TiAl) blades, which are especially sensitive to impacts. The disengagement of a shim 30 can also cause increased wear between the blade root 20 and the disc 40, since the protective piece is no longer present, and consequently, the mechanical strength of these parts is degraded in this area.

[0012] This phenomenon of disengagement from flashy products is initiated and maintained by two cumulative factors: The mechanical strength of the shim is insufficient and cannot withstand the stresses generated between the blade root and the disc during operation, nor the thermal stresses caused by the repeated thermal expansion and contraction of the blade root and the disc throughout the operating cycles. Indeed, with the successive temperature increases and decreases of the blade root, the shim also expands and contracts, leading to damage and its partial, then total, degradation.

[0013] During maintenance, the disengagement of one or more shims necessitates removing the rotor for repair. However, removing and repairing a rotor incurs significant costs in parts and labor, as well as downtime for the turbomachine.

[0014] Furthermore, significant wear was observed on the disc rim on the downstream face of the disc teeth. Indeed, the axial stop of the blade foot 20 downstream is generally achieved by means of a retaining ring inserted into a hook on the blade. A cross-sectional view of a blade foot 20 mounted in a cavity 41 of the disc 40 is shown in the figure. figure 4 This view of the figure 4 shows the disc 40 in which the foot 20 of the movable blade 10 is housed. It also shows the hook 15 of the movable blade 10, projecting on the downstream face, in which a retaining piece called the retaining ring 50 is slid. The retaining ring 50 extends circularly along the downstream face of the disc 40 so as to retain all the blade feet 20 in the cavities of the disc and prevent any axial movement of said blade feet downstream.

[0015] The retaining ring 50 is therefore in contact not only with the downstream face of the blade feet 20, but also with the downstream rim 46 of the disc 40, at the level of the disc teeth. This contact between the retaining ring 50 and the downstream rim of the disc teeth creates contact wear zones 48, as shown in the figure 5 Each 48 zone of contact wear presents a risk of crack initiation and propagation, which significantly impacts the disc's lifespan. During maintenance, a crack initiated by contact wear leads to premature disc removal followed by repair or replacement. However, disc removal and repair or replacement incur substantial costs in parts and labor, as well as downtime for the turbomachine. RESUME DE L'INVENTION

[0016] To address the problems mentioned above of disengagement of moving blade shims and contact wear of the disc rim, the applicant proposes a turbine disc shim, positioned at least partially around a tooth of the disc and extending, on the one hand, along the disc rim and, on the other hand, between the side wall of the disc cavity and the foot of the moving blade.

[0017] According to a first aspect, the invention relates to a shim for a turbomachine turbine disc, comprising a casing surrounding at least partially a tooth of the turbine disc, said tooth separating a first and a second cavities of the disc, each adapted to receive a foot of a movable turbine blade, such that the casing is adapted to cover at least partially the lateral walls of the tooth, characterized in that the casing is adapted to cover at least partially a downstream rim of said tooth.

[0018] The shim according to the invention has the advantage of protecting not only the contact area between the blade root and the disc cavity but also the contact area between the retaining ring and the disc rim. Furthermore, it prevents the shim from disengaging.

[0019] The use of a shim according to the invention in a turbomachine limits the number of engine removals, reduces the number of parts to be replaced during engine removal, and therefore lowers turbomachine maintenance costs. It also increases turbine lifespan and improves flight safety.

[0020] In this application, the terms "lower," "upper," "inner," and "outer" are interpreted with reference to the position of a part or surface relative to the axis of rotation of the turbomachine, a lower or inner surface being closer to the axis of rotation than an outer or outer surface. The term "lateral" is interpreted as "located on the sides of a part that extends radially" along an axis substantially perpendicular to the axis of rotation X. The term "axial" is to be interpreted as "along the direction of the axis of rotation," and the term "radial" as "along a direction perpendicular to the axis of rotation" or "along the direction of a radius of the blade ring." The terms "upstream" and "downstream" are to be interpreted with reference to the direction of airflow within the turbomachine.

[0021] In addition to the characteristics mentioned in the preceding paragraph, the turbine disc shim according to one aspect of the invention may have one or more additional characteristics from among the following, considered individually or in all technically possible combinations: In one example, the shim circumferentially covers a portion of the distal rim of the tooth. This portion of the distal rim is radially bounded between the tooth's apex and a tangent line whose plane, parallel to the x-axis, passes through the endpoints of the tooth's bearing surfaces opposite the apex. In another example, the shim comprises two lateral longitudinal edges, each extending into an area covered by a principal surface adapted to cover an external face of the disc tooth. In yet another example, the two lateral longitudinal edges are parallel and separated by a distance less than the circumferential width of the principal surface. The two lateral longitudinal edges connect an external surface of the shim and an internal surface of the shim adapted to face the tooth.It comprises a main surface adapted to cover an outer face of the disc tooth, a first and a second lateral surface extending from the main surface to cover lateral walls of the disc tooth, and a downstream surface extending between the main surface and the lateral surfaces to at least partially cover a downstream rim of the disc tooth. It comprises at least one tab extending radially along an upstream rim of the disc tooth. It comprises two tabs extending radially along the upstream rim of the disc tooth and distributed along said upstream rim. The tab(s) is / are formed as an extension of the main surface and folded along the upstream rim. It comprises a substantially C-shaped cross-section, with a main body of the C covering the outer face of the disc tooth and two arms of the C covering the lateral walls of the disc tooth. The casing is formed from a metal sheet.

[0022] A second aspect of the invention relates to a turbomachine rotor assembly, comprising: at least one first and a second movable blades configured to be movable in rotation about an axis of rotation of the rotor and each comprising a blade foot having a lower face and two lateral flanks extending on either side of the lower face, a disc comprising at least one first and a second cavities adapted to each receive a blade foot, and a tooth separating the first and second cavities, and a shim according to the first aspect of the invention.

[0023] Advantageously, the first lateral surface of the shim is housed between one of the lateral walls of the disc tooth and the lateral flank of the blade foot of the first movable blade and the second lateral surface of the shim is housed between another of the lateral walls of the disc tooth and the lateral flank of the blade foot of the second movable blade.

[0024] A third aspect of the invention relates to a method for assembling a rotor assembly for a turbomachine according to the second aspect. This method is characterized by the fact that it comprises the following steps: positioning of a shim according to the first aspect of the invention around a tooth of the disc so that said shim covers at least the lateral walls and the downstream rim of the tooth of the disc, folding of at least one tab so as to position it along the upstream rim of the tooth of the disc, and installation of the first blade foot in the first cavity of the disc and of the second blade foot in the second cavity so that a portion of the shim is positioned between the first blade foot and one of the lateral walls of the tooth of the disc and another portion of the shim is positioned between the second blade foot and the other lateral wall of the tooth of the disc.

[0025] A fourth aspect of the invention relates to a turbomachine rotor, characterized by the fact that it comprises a plurality of assemblies as defined above, juxtaposed circularly next to each other.

[0026] A fifth aspect of the invention relates to a turbomachine, characterized by the fact that it comprises a plurality of assemblies as defined above, mounted so as to form a rotor. BREVE DESCRIPTION DES FIGURES

[0027] Other advantages and features of the invention will become apparent from the following description, illustrated by the figures in which: There figure 1 The figure already described represents a schematic perspective view of a moving turbine blade of a turbomachine according to the prior art; figure 2 The diagram, already described, represents a schematic perspective view of a movable blade base equipped with a clapper according to the prior art; figure 3 The diagram, already described, schematically represents a perspective view of a broken shim, in the process of being disengaged from the waterwheel; The figure 4 The diagram, already described, schematically represents a radial cross-sectional view of a blade root mounted in a disk cavity and held in place by a retaining ring; figure 5 The diagram, already described, schematically represents a perspective view of a portion of a disc rim prematurely worn by contact with a retaining ring; figure 6 schematically represents a perspective view of a disc tooth equipped with a shim according to an embodiment of the invention when a blade foot is mounted in the cavity adjacent to the tooth; The figure 7 schematically represents a perspective view of a turbine disc shim according to a preferred embodiment of the invention; The figure 8 schematically represents a perspective view, from upstream, of a shim according to an embodiment of the invention, mounted on a tooth of a turbine disc; and The figure 9 schematically represents a perspective view, from downstream, of a shim according to an embodiment of the invention, mounted on a tooth of a turbine disc. DESCRIPTION DETAILLEE

[0028] An example of a turbine disc guard, configured to protect both the disc rim and the blade root without risk of disengagement, is described in detail below, with reference to the accompanying drawings. This example illustrates the features and advantages of the invention. It should be noted, however, that the invention is not limited to this example.

[0029] In the figures, identical elements are identified by identical references. For the sake of readability, the size scales between represented elements are not respected.

[0030] A turbomachine rotor comprises a disk and a plurality of movable blades, each held in a cavity in the disk by its root. The root of each blade is housed in a cavity in the disk. An example of disk cavities is shown in perspective on the figure 6 Each cavity 41 (not referenced on the figure 6 but visible) of the disc 40, in the form of a hollow, is generally provided in the outer periphery of the disc 40. Each cavity 41 is separated from a neighboring cavity by a tooth 42 of the disc. A foot 20 of a movable rotor blade, in the form of a dovetail, is engaged in each cavity 41 and is held radially in said cavity by the cooperation of form between the foot and the cavity.

[0031] A cavity 41 of the disc 40 has a bottom surface 43 and two lateral surfaces, each formed by the lateral wall 44 of an adjacent tooth 42. A tooth 42 of the disc 40 therefore has two lateral walls 44 as well as an external face 45, a downstream rim 46 and an upstream rim 47 (not visible on the figure 6 ). The downstream rim 46 and upstream rim 47 are also called respectively the downstream or upstream radial surface of the tooth.

[0032] Each blade foot 20 comprises a lower face 21, facing the bottom surface 43 of the cavity 41, and two lateral flanks 22 forming the contact interfaces of the blade foot 20 with the disk cavity 41.

[0033] During rotor rotation, the moving blades are subjected to centrifugal forces; under the effect of these centrifugal forces, the lateral sides 22 of the blade roots 20 come into contact with the lateral walls 44 of the teeth 42 of the disc 41 (or lateral surfaces of the cavity 41). According to the invention, a shim 400, made of a metal sheet (metal or alloy), is positioned around each tooth 42 of the disc 40 so as to enclose at least the areas to be protected. Thus, each shim 400 preferably covers at least the lateral walls 44 of the tooth 42 to which it is attached, as well as the downstream rim 46 of said tooth 42.

[0034] An example of a 400 tinsel according to a preferred embodiment is shown on the figure 7 An example of this 400 shim mounted on a tooth 42 of the disc 40 is shown on the figure 8 according to a perspective view from downstream. The 400 series, according to this preferred embodiment, comprises: a main surface 450 adapted to cover the outer face 45 of the tooth 42, a first and a second lateral surfaces 440 to cover the lateral walls 44 of the tooth 42, and a downstream surface 460 to cover at least partially the downstream rim 46 of the tooth 42 of the disc.

[0035] The main surface 450 and the lateral surfaces 440 extend in line with each other, with a first lateral surface 440a extending from one side of the main surface 450, and a second lateral surface 440b extending from the other side of the main surface, opposite the first lateral surface. The main surface 450 and the lateral surfaces 440 have a C-shaped cross-section, the main body of the C being formed by the main surface 450, and the two arms of the C being formed by the two lateral surfaces 440a and 440b.

[0036] The downstream surface 460 extends radially along the downstream rim 46 of the tooth 42, between the two lateral surfaces 440a, 440b and the main surface 450 so that the whole (main, lateral and upstream surfaces) has overall the shape of a hood.

[0037] Thus, with such a shape of the shim 400, each lateral flank 22 of a blade foot 20 is separated from the lateral wall 44 of the adjacent tooth 42 (or lateral surface of the cavity 41) by a lateral surface 440 of the shim 400. In other words, the first lateral surface 440a of the shim 400 is positioned between the lateral flank 22 of a blade foot 20 and one of the lateral walls 44 of the tooth 42 and the second lateral surface 440b of the shim 400 is positioned between the lateral flank 22 of another blade foot 20 and the other lateral wall 44 of the tooth 42 of the disc 40 so that the two lateral walls of the tooth 42 and the lateral flank 22 of each of the adjacent blade feet are protected from friction by contact between them.

[0038] With the shape of the shim 400 described previously, the downstream rim 46 of the tooth 42 of the disc is covered by the downstream surface 460 of the shim 400. Thus, the downstream rim 46 is not in direct contact with the retaining ring 50 allowing the axial stop of the blade foot 20 downstream so that said downstream rim 46 is protected from the risks of friction by contact with said ring.

[0039] In one embodiment of the invention, the shim 400 comprises at least one tab 480 extending radially along the upstream rim 47 of the tooth 42 of the disc to lock the positioning of said shim around the tooth 42. An example of this embodiment is shown in the figure 9 according to a perspective view from upstream. The tab 480 is formed from the same metal sheet as the entire shim 400, by cutting said sheet. The tab 480 extends from the end of one of the surfaces of the shim 400, for example from the main surface 450 or from one of the lateral surfaces 440, and is folded along the rim 47 of the tooth 42. In the example of the figure 9 , the tongue 480 extends in line with the main surface 450. The tongue 480, once folded, extends along a radial plane against the upstream rim 47, ensuring axial support of the shim 400 around the tooth 42.

[0040] According to some embodiments, the 400 flashing comprises several 480 tabs, for example two as in the example of the figure 9, all folded along the upstream rim 47. When there are several tabs 480, these are preferably distributed around the contour of the upstream rim 47 in order to optimize the retention of the shim around the tooth 42.

[0041] The shim 400, as described above, is made, for example, by folding or stamping a metal sheet. The tab(s) are made by cutting the metal sheet. They are only folded once the shim is correctly positioned on the tooth 42 of the disc.

[0042] Indeed, once the shim 400 is manufactured, it is mounted on the tooth 42 of the disc by sliding it along the outer face 45 and the lateral walls 44 of said tooth, from downstream to upstream. In other words, the shim 400 is threaded axially around a tooth 42 of the disc. It is in position when its downstream surface 460 is in contact with the downstream face 46 of the tooth 42. The shim 400 then covers the lateral walls 44, the outer face 45, and the downstream face 46 of the tooth 42 of the disc. When they exist, the tabs 480 are then folded radially along the upstream face 47 of the tooth 42 so as to lock the shim around the tooth 42. Two blade feet 20 can then each be installed in one of the cavities 41 adjacent to the tooth 42. The lateral surfaces 480a, 480b of the shim 400 are then each positioned in a cavity 41, between one of the blade feet and one of the lateral walls 44 of the tooth 42.

[0043] It is clear from the foregoing that, unlike the shims of the prior art, the shim 400 according to the invention is mounted on the disc, around a disc tooth, and not around the blade root. This mounting improves the mechanical strength of the shim without deforming or weakening it. Furthermore, it protects the downstream rim of the disc, in addition to the contact area between the blade root and the wall of the disc cavity 41.

[0044] The 400 shim material, more broadly, allows for cost reduction by improving the durability of rotor parts, preventing potential engine removals due to premature contact wear, reducing the number of parts replaced during engine removal, and lowering maintenance costs and the frequency of maintenance. It thus improves customer satisfaction and eliminates a recurring problem.

Claims

1. A foil (400) for a turbomachine turbine disk (40), comprising a casing at least partially surrounding a tooth (42) of a turbine disk (40), said tooth (42) separating a first and a second cavity (41) of the disk, each adapted to receive a root (20) of a movable vane of the turbine, the casing is adapted to at least partially cover each of the side walls (44) of the tooth (42), characterised in that the casing is adapted to at least partially cover a downstream rim (46) of said tooth (42).

2. The foil according to claim 1, characterised in that it includes: - a main surface (450) adapted to cover an outer face (45) of the tooth of the disk, - a first and a second side surface (440a, 440b) extending from the main surface (450) to cover side walls (44) of the tooth of the disk, and - a downstream surface (460) extending between the main surface (450) and the side surfaces (440) to at least partially cover a downstream rim (46) of the tooth of the disk.

3. The foil according to claim 1 or 2, characterised in that it includes a tab (480) radially extending along an upstream rim (47) of the tooth (42) of the disk.

4. The foil according to claim 2 or 3, characterised in that it includes at least two tabs (480) radially extending along the upstream rim (47) of the tooth of the disk and distributed along said upstream rim.

5. The foil according to claim 2 and claim 3 or 4, characterised in that the tab (480) is formed as an extension of the main surface (450) and folded along the upstream rim (47).

6. The foil according to any of claims 1 to 5, characterised in that it includes a substantially C-shaped cross-section, with a main body of the C which covers the outer face (45) of the tooth of the disk and two arms of the C which cover the side walls (44) of the tooth of the disk.

7. The foil according to any of claims 1 to 6, characterised in that the casing is formed from a metal sheet.

8. An assembly for a turbomachine rotor including: - at least a first and a second movable vane (10) configured to be rotatably movable about an axis of rotation (X) of the rotor and each including a vane root (20) provided with a lower face (21) and two side flanks (22) extending on either side of the lower face, - a disk (40) including at least • a first and a second cavity (41) each adapted to receive a vane root (20), and • a tooth (42) separating the first and the second cavity (41), and - a foil (400) according to any of claims 1 to 7.

9. The assembly according to claim 8, characterised in that the first side surface (440a) of the foil is housed between one of the side walls (44) of the tooth (42) of the disk and the side flank (22) of the vane root of the first movable vane and the second side surface (440b) of the foil is housed between another of the side walls (44) of the tooth (42) of the disk and the side flank (22) of the vane root of the second movable vane.

10. A method for mounting a rotor assembly for a turbomachine according to any of claims 8 to 9, characterised in that it includes the following steps of: - positioning a foil (400) according to any of claims 1 to 7 around a tooth (42) of the disk (40) so that said foil covers at least the side walls (44) and the downstream rim (46) of the tooth of the disk, - folding at least one tab (480) so as to position it along the upstream rim (47) of the tooth of the disk, and - installing the root (20) of the first movable vane into the first cavity (41) of the disk and the root (20) of the second movable vane into the second cavity (41) so that a portion of the foil (400) is positioned between the root of the first movable vane and one of the side walls (44) of the tooth of the disk and another portion of the foil (400) is positioned between the root of the second movable vane and the other side wall (44) of the tooth of the disk.

11. A turbomachine rotor, characterised in that it includes a plurality of assemblies according to any of claims 8 and 9, juxtaposed circularly next to one another.

12. The turbomachine, characterised in that it includes a plurality of assemblies according to any of claims 8 and 9 mounted so as to form a rotor.

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