Rotating assembly for turbomachine

Abstract

Rotating assembly (10) for turbomachine, comprising: - a disc (12) having an outer periphery (16) having an alternation of pits (18) and teeth (20), - blades (14), each blade (14) comprising a radially extending blade (26), a foot (22) engaged axially and retained radially in one of the pits (18) of the disc (12), and a platform (24) arranged radially between the foot (22) and the blade (26) and extending circumferentially, the platforms (24) of the blades (14) being arranged circumferentially end to end, opposite each other. Each blade (14) includes a stop element (30, 40) extending at least radially from the foot (22), the stop element (30, 40) being arranged in axial contact with the disc (12). Figure to be published with the abbreviation: 3

Description

Title of the invention: Rotating assembly for turbomachine Technical field of the invention

[0001] The invention relates to a rotary assembly for a turbomachine, such as in particular an aircraft turbojet, as well as to a turbomachine comprising such a rotary assembly. State of the prior art

[0002] Such an assembly, which is found in particular in a turbine, comprises a disc, and blades extending radially from the disc and whose roots are axially engaged and radially retained in cells in the external periphery of the disc, said cells being arranged alternately with teeth of the disc.

[0003] The expressions axial, radial and circumferential are understood relative to a main axis of the turbomachine passing through the center of the disk, which is the axis of rotation of the rotating assemblies.

[0004] The blades also comprise internal platforms arranged circumferentially end to end so as to together define the internal boundary of the flow of hot gases circulating in the turbine. The part of the blade located internally with respect to the vein, that is to say between the internal platform and the root, is called a stilt. According to this arrangement, spaces are formed between two adjacent stilts, and form inter-stilt or inter-blade cavities. So-called cell bottom cavities are also formed by radial spaces located between the blade roots and the bottoms of the cells.

[0005] Alternatively, the rotating assembly may be part of a counter-rotating turbine comprising two rotors rotating in opposite directions to each other. In this case, the blades may extend radially inward from roots arranged at the periphery of the rotor. The platforms then define an external space relative to the vein.

[0006] In order to improve the performance of the turbomachine, and to avoid heating of the disk by the flow of hot gases from an upstream combustion chamber and flowing through the duct, it is important to limit as much as possible the circulation of these gases under the platforms and through the inter-blade cavities, using sealing means. Indeed, the part of the duct gases flowing under the platforms does not participate in the rotational drive of the blades and directly heats the teeth of the disk. It is particularly advantageous to arrange the sealing means downstream of the inter-blade cavities in order to allow pressurization of these cavities to a value substantially identical to that of the duct gases, which limits the suction effect in the cavities.

[0007] To this end, it is known to use, for example on the rotating assembly presented above, a flange, also called a ring, aimed at ensuring axial sealing of an annular zone extending radially between the platforms and the disc, on the downstream face of Péchasse and the foot.

[0008] This flange may be in the form of a metallic annular ring, formed of a radial annular wall comprising a single radial slot, or formed approximately of sectors arranged end to end, generally arranged downstream of the inter-blade cavities.

[0009] The flange is typically engaged in a groove of the disc on the one hand, and on the other hand by hooks mounted on the blades or a groove defined in the platforms of the blades.

[0010] The flange also makes it possible to implement a holding of the blades in the axial direction, which is the direction of insertion of the blade roots into the cells of the disc, since it is arranged in axial contact with the blade roots.

[0011] Examples of such rotating assemblies comprising improved rods are described in documents FR 3020407 and FR 3011031.

[0012] However, the use of such a flange for holding the blades can lead to significant wear and damage to the flange and the blades, due to axial forces, which can lead to a loss of sealing and mechanical damage to these parts. Presentation of the invention

[0013] The invention aims to remedy these drawbacks by proposing to transfer the function of axially holding the blades to other elements of the rotating assembly.

[0014] To this end, the invention relates to a rotary assembly for a turbomachine, comprising:

[0015] - a disc having an external periphery presenting an alternation of alveoli and teeth,

[0016] - blades, each blade comprising a radially extending blade, a root axially engaged and radially retained in one of the cells of the disc, and a platform arranged radially between the root and the blade and extending circumferentially, the platforms of the blades being arranged circumferentially end to end, opposite each other,

[0017] characterized in that each blade comprises a stop element extending radially from the root, the stop element being arranged in axial contact with the disc.

[0018] Such a rotating assembly makes it possible to transfer the axial holding function of the blades from the sealing flange to a stop element directly integrated into the blade.

[0019] Such a rotating assembly may comprise a flange, which does not play a role of axial maintenance of the blades, or not include such a flange.

[0020] This makes it possible to reduce the wear of the flange due to axial forces when the flange is present, or to completely dispense with said flange, simplifying the architecture of the rotating assembly and reducing its mass.

[0021] The rotating assembly may be part of a low pressure turbine or a high pressure turbine.

[0022] The stop element may be a hook projecting axially and radially from the root and / or the platform of the blade.

[0023] Such a hook allows simple and strong axial fixing of the blades, independently of any sealing flange.

[0024] The hook is for example positioned upstream of the foot of the blade.

[0025] The stop element may be a plate extending in a radial and circumferential plane from the foot and / or the platform, each plate being arranged in axial contact with the disc.

[0026] Such a plate secured to the rest of the blade is capable of fulfilling both the role of axially holding the blades and that of sealing the disc.

[0027] The plate may have a substantially rectangular shape in said radial and circumferential plane.

[0028] The plate may extend beyond a circumferential edge of the platform and extends into axial contact with the root and / or platform of a neighboring blade.

[0029] Such a characteristic allows axial maintenance of the blades in both directions, from one end to the other.

[0030] The plate may comprise a proximal circumferential edge relative to the foot, the foot having a first circumferential edge, said proximal circumferential edge extending beyond said first circumferential edge of the foot, at a circumferential distance greater than or equal to a quarter of a minimum circumferential width of the foot.

[0031] The plate may comprise a distal circumferential edge relative to the root, a circumferential distance separating said distal edge from a second circumferential edge of the root of a neighboring blade being less than or equal to a quarter of a minimum circumferential width of the root.

[0032] These characteristics make it possible to maintain a better seal of the part located between the disc and the platforms.

[0033] The plate may have a circumferential width greater than or equal to a circumferential width of the platform minus half of a minimum circumferential width of the foot.

[0034] The plate may be located axially downstream of the foot and the platform.

[0035] This feature allows the maintenance of a high pressure in the part located between the disc and the platforms so as to balance the pressures on both sides. other than said platforms.

[0036] A clearance measured circumferentially between two neighboring plates can be between 0.1 and 0.5 millimeters.

[0037] The invention also relates to a turbomachine comprising at least one rotary assembly as previously.

[0038] The turbomachine may be an aircraft turbojet and the rotating assemblies may be part of a rotor of said turbojet. Brief description of the figures

[0039] [Fig-1] [Fig.l] is an axial schematic view from upstream of an assembly rotary according to a first embodiment of the invention,

[0040] [Fig.2] [Fig.2] is a schematic circumferential sectional view of the assembly rotary of [Fig.l],

[0041] [Fig.3] [Fig.3] is an axial schematic view from downstream of a rotating assembly according to a second embodiment of the invention, and

[0042] [Fig.4] [Fig.4] is a schematic radial sectional view of the rotating assembly of the [Fig.3]. Detailed description of the invention

[0043] [Fig.l] represents a rotary assembly 10 according to the invention, seen from upstream in the direction of a main axis A of the rotary assembly 10.

[0044] In all that follows, the terms axial, radial and circumferential are understood relative to the main axis A. The terms upstream and downstream are understood relative to the flow of air in the direction of the main axis A in normal operation.

[0045] The rotating assembly 10 is for example part of a turbomachine rotor, such as an aircraft turbojet rotor, in particular a low-pressure turbine.

[0046] Alternatively, the rotating assembly may be part of a high pressure turbine.

[0047] [Fig.2] is a view of this same rotating assembly 10 in schematic section in a radial and axial plane.

[0048] The rotary assembly 10 comprises a disc 12 movable in rotation around the main axis A, and a plurality of blades 14 distributed around the disc 12.

[0049] The disc 12 has a substantially circular shape and comprises an external peripheral surface 16 defining an alternation of cells 18 and teeth 20.

[0050] The teeth 20 define between them the cells 18, which are provided to receive and hold the blades 14 in the circumferential and radial directions.

[0051] The blades 14 extend from the disc 12 into a substantially annular vein 21 in which a flow of air flows in the axial direction.

[0052] Each blade 14 comprises a foot 22, or stilt, a platform 24 and a blade 26.

[0053] The feet 22 of the blades 14 have a shape comprising a widening, for example in dovetail or equivalent, to ensure their radial maintenance in the cells 18.

[0054] The platforms 24 are arranged circumferentially end to end so as to together define an internal boundary of the gas flow stream.

[0055] According to this arrangement, spaces 28 are formed between two circumferentially adjacent feet 22, in the annular zone extending radially from the platforms 24 to the disc 12, and are called inter-stilt or inter-blade cavities.

[0056] The blades 26 extend radially from the platforms and have aerodynamic shapes designed to transform a portion of the energy provided by the flow of gases in the vein 21 into rotational movement for the rotating assembly 10.

[0057] According to the invention, each blade 14 comprises a stop element 30 extending radially from the root 22, the stop element 30 being arranged in axial contact with the disc 12.

[0058] In the first embodiment shown in Figures 1 and 2, the stop element 30 is a hook extending from the foot 22 to an upstream face of the disc 12.

[0059] The hook 30 is similar to the hooks usually intended to hold a sealing flange upstream or downstream of the blades and the disc, as explained above.

[0060] The hook 30 is made in one piece with the foot 22 and, optionally, with the platform 24, and for example molded with the rest of the blade 14 in a foundry.

[0061] The hook 30 allows the blade 14 to be held in place in the axial direction.

[0062] According to a variant not shown, each blade may comprise two hooks 30 spaced apart from each other circumferentially, for symmetrical support of the blade 14.

[0063] The axial sealing of the spaces 28 is important, because if a portion of the gases circulates through these cavities, it does not participate in the rotational drive of the blades 14 and directly heats the teeth 20 of the disc 12 forming the bottom of the inter-blade cavities, which leads to an increase in the temperature of the disc 12 which can damage it and reduce its service life.

[0064] For this purpose, the rotating device 10 may comprise a flange 32, for example engaged in a groove 34 of the platforms 14 and held by hooks 36 of the disc 12.

[0065] The flange 32 may be an annular part having a single radial slot, or else sectorized, as described previously.

[0066] The flange 32 ensures the sealing of the spaces 28 on the downstream side, without ensuring axial support of the blades 14, this role being ensured by the stop elements 30. Thus, the wear of the flange is reduced and its operating life increased.

[0067] Alternatively, as mentioned above, the blades may be part of a counter-rotating rotor disc, and be arranged with peripheral roots and blades extending radially inwards, so that the inter-blade spaces are radially outer spaces. The invention is applicable to this type of disc in an undifferentiated manner.

[0068] A second embodiment of the rotating assembly 10 is shown in Figures 3 and 4, similar to the first embodiment except as follows.

[0069] The stop element of each blade 14 in the second embodiment is constituted by a plate 40 extending radially and circumferentially, integral with the root 22 and the platform 24 of the blade 14.

[0070] The plates 40 of the neighboring blades 14 are arranged circumferentially end to end so as to ensure both the maintenance of the blades 14 in the axial direction and the axial sealing of the inter-blade spaces 28.

[0071] A clearance measured circumferentially between two neighboring plates 40 is between 0.1 and 0.5 millimeters, depending on the size of the disc 12 and the blades 14.

[0072] Each plate 40 is arranged in axial contact with the disc 12, and extends circumferentially beyond a circumferential edge 41 of the platform 24, in axial contact with the root 22 and / or the platform 24 of a neighboring blade 14, to block the axial movements of this neighboring blade 14.

[0073] Each plate 40 has a proximal edge 42 and a distal edge 44 relative to the foot 22.

[0074] The proximal edge 42 extends beyond a first circumferential edge 46 of the foot 22, in the direction of a median plane of the foot 22. A circumferential distance between said proximal edge 42 and said first circumferential edge 46 is greater than or equal to a quarter of a minimum thickness e of the foot 22 measured circumferentially.

[0075] The minimum thickness of the foot 22 is its thickness measured at its circumferentially narrowest point, over its radial extent, as shown in [Fig.3]

[0076] Similarly, the distal edge 44 extends beyond a second circumferential edge 48 of the root 22 of the neighboring blade 14 in contact with the plate 40, in the direction of a median plane of the root 22 of said neighboring blade 14. A circumferential distance between said distal edge 44 and said second circumferential edge 48 is greater than or equal to a quarter of the minimum thickness e of the root 22.

[0077] This arrangement of the plate 40 allows effective maintenance of the sealing of the inter-blade spaces 28.

Claims

Claims

1. Rotary assembly (10) for a turbomachine, comprising: - a disc (12) having a periphery (16) having an alternation of cells (18) and teeth (20), - blades (14), each blade (14) comprising a blade (26) extending radially, a root (22) axially engaged and radially retained in one of the cells (18) of the disc (12), and a platform (24) arranged radially between the root (22) and the blade (26) and extending circumferentially, the platforms (24) of the blades (14) being arranged circumferentially end to end, one opposite the other, characterized in that each blade (14) comprises a stop element (30, 40) extending at least radially from the root (22), the stop element (30, 40) being arranged in axial contact with the disc (12), wherein the stop element (40) is a plate extending in a radial and circumferential plane from the foot (22) and / or the platform (24),each plate (40) being arranged in axial contact with the disc (12), and wherein the plate (40) extends beyond a circumferential edge (41) of the platform (24) and extends in axial contact with the root (22) and / or the platform (24) of a neighboring blade (14).,

2. A rotary assembly (10) according to claim 1, wherein the plate (40) comprises a proximal circumferential edge (42) relative to the foot (22), the foot (22) having a first circumferential edge (46), said proximal circumferential edge (42) extending beyond said first circumferential edge (46) of the foot (22), at a circumferential distance greater than or equal to a quarter of a minimum circumferential width (e) of the foot (22).

3. Rotary assembly (10) according to one of the preceding claims, in which the plate (40) comprises a distal circumferential edge (44) relative to the root (22), a circumferential distance separating said distal edge (44) from a second circumferential edge (48) of the root (22) of a neighboring blade (14) being less than or equal to a quarter of a minimum circumferential width (e) of the root (22).

4. A rotary assembly (10) according to any preceding claim, wherein the plate (40) has a circumferential width greater than or equal to a circumferential width of the platform (24) less half a minimum circumferential width (e) of the foot (22).

5. A rotary assembly (10) according to any preceding claim, wherein the plate (40) is located axially downstream of the foot (22) and the platform (24).

6. A rotating assembly (10) according to any preceding claim, wherein a clearance measured circumferentially between two adjacent plates (40) is between 0.1 and 0.5 millimeters.

7. Turbomachine comprising at least one rotary assembly (10) according to one of the preceding claims.

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