Movable ring assembly for turbomachine rotor

Abstract

Movable ring assembly for a turbomachine rotor, the movable ring (6) comprising an external peripheral toothing (7), each tooth of the external peripheral toothing (7) having an inner face (7a) intended to be positioned opposite a blade root (3) of the rotor and an outer face (7b) opposite the inner face (7a) and intended to be positioned opposite an axial retaining hook (4) disposed on the blade root (3). Furthermore, the movable ring assembly (10) (6) comprises at least one protective element (11; 12) disposed on the outer face (7b) of at least one tooth of the external peripheral toothing (7). Figure for the abbreviation: Fig 4

Description

Title of the invention: Movable ring assembly for a turbine rotor Technical field

[0001] The present invention relates, in general, to a turbomachine rotor and relates, more particularly, to the holding of a plurality of blades in a turbine disk by a movable ring of a turbomachine rotor.

[0002] More specifically, the invention relates to a movable ring assembly as well as a turbomachine rotor comprising such a movable ring assembly. State of the art

[0003] Conventionally, a turbomachine comprises, from upstream to downstream relative to the direction of air circulation in the turbomachine, a fan, a low-pressure compressor stage, a high-pressure compressor stage, a combustion chamber, a high-pressure turbine stage and a low-pressure turbine stage.

[0004] With reference to [Fig. 1], a low-pressure turbine stage generally comprises a rotor disc 1 on which a plurality of removable blades 2 are mounted. The blades 2 comprise a blade root 3 machined at the base of the blade 2 and comprising a portion, for example dovetail-shaped, for their installation in axial grooves, also dovetail-shaped, machined on the rotor disc 1. The assembly is carried out by fitting the blade root 3 into the axial groove.

[0005] The blade roots 3 are axially immobilized by means of axial retaining hooks 4 of the blade on the rotor disc 1, integral with the root of the blades 3.

[0006] The ring arm 5 of a movable ring 6 is provided with external peripheral teeth 7. The movable ring 6 is mounted on the rotor disc 1 and the blades 2 so that the teeth of the external peripheral teeth 7 are inserted into the groove 8 of the axial retaining hooks 4. Each blade 2 has an axial retaining hook 4 and the teeth of the external peripheral teeth 7 of the movable ring lock each blade 2 via the groove 8.

[0007] A seal 9, arranged between the movable ring 6 and the rotor disc 1, limits air leaks.

[0008] The shape of the ring arm 5 is permissive in terms of bending leading to movement of the ring arm 5 when hot. The blade 2 is generally made of a harder material than that of the movable ring 6 and the movement of the ring arm causes repeated contacts with the axial retaining hook.

[0009] These impacts, which are added to the shocks due to vibrations during the flight phases, lead to deterioration by contact wear, in English "fretting", of the groove axial retaining hooks 4 and external peripheral teeth 7. The deformation causes deterioration by impression of the teeth up to a loss of thickness of 2 mm. Statement of the invention

[0010] The invention therefore aims to remedy these drawbacks and to propose a turbomachine rotor making it possible to reduce or even eliminate premature wear of the movable ring by limiting the contact between the movable ring and the axial retaining hook.

[0011] There is therefore proposed a movable ring assembly for a turbomachine rotor, the movable ring comprising an external peripheral toothing, each tooth of the external peripheral toothing comprising an inner face intended to be positioned opposite a blade root of the rotor and an outer face opposite the inner face and intended to be positioned opposite an axial retaining hook arranged on the blade root.

[0012] Furthermore, the movable ring assembly comprises at least one protective element disposed on the outer face of at least one tooth of the external peripheral toothing.

[0013] According to an exemplary embodiment, the protective element may be a coating on the outer face of the teeth.

[0014] According to one characteristic, the material of said coating may comprise nickel and chromium.

[0015] Advantageously, the outer face of the teeth may comprise a machined portion on which said coating is applied.

[0016] According to another exemplary embodiment, the protective element may be a protective part arranged on the movable ring.

[0017] Advantageously, the movable ring assembly may comprise a plurality of protective pieces, each protective piece being positioned on one of the teeth of the external peripheral toothing.

[0018] According to a variant, the protective part may extend over the entire circumference of the external peripheral teeth of the movable ring, the protective part comprising a slot. The slot is made to allow the mounting of the protective part on the external peripheral teeth of the movable ring.

[0019] Advantageously, the external peripheral toothing can be surmounted by the protective part, the protective part comprising a first portion configured to cover the outer and inner faces of the teeth of the external peripheral toothing.

[0020] Advantageously, the movable ring may comprise a hook arranged in the extension of the inner face of the teeth of the external peripheral toothing and configured to receive a seal, a second portion of the protective part comprising a hook configured to integrate at least partly into the hook placed on the movable ring.

[0021] Preferably, the hook of the second portion of the protective part comprises an oblique part configured to receive a seal and extending in a direction opposite to the central axis of the movable ring.

[0022] The invention also relates to a turbomachine rotor comprising a plurality of blades each comprising a blade root provided with an axial retaining hook.

[0023] Furthermore, the rotor further comprises a movable ring assembly as described previously, the inner and outer faces of each tooth of the outer peripheral toothing of the movable ring being respectively positioned opposite a blade root and opposite an axial retaining hook.

[0024] The invention also relates to a turbomachine comprising a rotor as described above. Brief description of the drawings

[0025] Other aims, advantages and characteristics will emerge from the description which follows, given purely for illustrative purposes and with reference to the appended drawings in which:

[0026] [Fig. 1] is a sectional view of a turbomachine rotor according to the prior art.

[0027] [Fig.2] is a sectional view of a movable ring arm of a ring assembly mobile for turbomachine rotor according to a first embodiment of the invention.

[0028] [Fig.3] is a view of a movable ring arm of a movable ring assembly for a turbomachine rotor according to a second embodiment of the invention.

[0029] [Fig.4] is a sectional view of a turbomachine rotor comprising a movable ring assembly according to the second embodiment illustrated in [Fig.3].

[0030] [Fig.5] is a top view of a protective part of a movable ring assembly according to the second embodiment illustrated in [Fig.3]. Detailed description of an embodiment

[0031] Figures 2 and 3 illustrate a low pressure turbine stage of an aircraft turbomachine.

[0032] The references relating to the elements of the low pressure turbine rotor illustrated in Figures 2 and 3 of identical, equivalent or similar structure or function to those of the elements of the low pressure turbine rotor illustrated in [Fig.l] are identical.

[0033] The rotor of the low-pressure turbine stage illustrated comprises a rotor disc 1 on which a plurality of removable blades 2 are mounted. The blades 2 comprise a blade root 3 machined at the base of the blade 2 and comprising a portion, for example dovetail-shaped, for their installation in axial grooves, also dovetail-shaped, machined on the rotor disc 1. The assembly is carried out by interlocking of the blade root 3 in the axial groove.

[0034] The blade roots 3 are axially immobilized by means of axial retaining hooks 4 of the blade on the rotor disc 1, integral with the root of the blades 3.

[0035] The movable ring 6, and in particular the free end of the movable ring 6, otherwise called ring arm 5 of the movable ring 6, is provided with an external peripheral toothing 7. The external peripheral toothing 7 is formed by a plurality of teeth. The movable ring 6 is mounted on the rotor disc 1 and the blades 2 so that each tooth of the external peripheral toothing 7 is associated with a blade root 3 and is inserted into a groove 8 of an axial retaining hook 4 arranged on the blade root 3.

[0036] The teeth of the external peripheral toothing 7 comprise an inner face 7a and an outer face 7b opposite the inner face 7a. The inner face 7a is intended to be positioned opposite a blade root 3 of the rotor and the outer face 7b is intended to be positioned opposite the axial retaining hook 4 arranged on the blade root 3.

[0037] The plurality of blades 2 is thus arranged on the external peripheral toothing 7 of the movable ring 6 and each of the teeth of the external peripheral toothing 7 of the movable ring 6 is positioned opposite a groove 8 of an axial retaining hook 4 of the blade root 3.

[0038] In the example illustrated, a seal 9, also called a gasket, is arranged between the movable ring 6 and the rotor disc 1,

[0039] After the blades 2 and the seal 9 are positioned on the rotor disc 1, the movable ring 6 is rotated a few degrees to place each of the teeth in one of the grooves 8 of the axial retaining hook 4.

[0040] The external peripheral toothing 7 makes it possible to hold the movable ring 6 upstream of the blades 2 in place during assembly and to prevent the seal 9 from disengaging upstream of the blades 2 during operation of the turbomachine.

[0041] Furthermore, at least one protective element is arranged on the outer face of at least one tooth, preferably each of the teeth, of the external peripheral toothing 7. The movable ring 6 and the protective element form a movable ring assembly 10.

[0042] During operation of the rotor of the turbomachine, the high temperature induces the movement of the movable ring 6 which opens and comes into contact with the axial retaining hook 4 repeatedly. The protective element protects the outer face 7b of the teeth subject to contact with the axial retaining hook 4, protecting the external peripheral teeth 7 against wear.

[0043] According to a first embodiment illustrated in [Fig.2], the protective element is a coating 11 applied to the outer face 7 of the teeth of the external peripheral toothing 7 making it possible to improve its mechanical friction properties.

[0044] Advantageously, the material of the coating 11 comprises nickel and chromium in order to improve the resistance properties of the outer face 7b of the coated tooth against friction and limit its wear.

[0045] The deposit of the coating 11a has the advantage of protecting the movable ring 6 from friction without significantly modifying its mass.

[0046] In the example illustrated, the outer face 7b of the teeth comprises a machined portion on which the coating is applied. It is thus possible to control the final thickness of the teeth by controlling the residual thickness of the teeth after machining. The formation of a machined portion avoids creating an excess thickness on the teeth after application of the coating.

[0047] According to a second embodiment illustrated in figures 3 and 4, the protective element can be a protective part 12 arranged on the movable ring 6. The protective part 12 is arranged on the outer face 7b of the teeth of the external peripheral toothing 7 and undergoes contact wear in place of the movable ring 6.

[0048] In the example illustrated, the protective part 12 is a part independent of the movable ring 6 facilitating the replacement of the protective part 12 when it is worn.

[0049] According to an alternative embodiment, it may be provided that the protection element is a protection part fixed to the movable ring 6.

[0050] The protective part 12 illustrated is a part of revolution and extends over the entire circumference of the external peripheral toothing 7. In this way, the single protective part 12 protects all of the teeth of the external peripheral toothing 7.

[0051] As shown in [Fig. 5], the protective part 12 preferably comprises a slot 13 on its circumference, which makes it easier to mount it on the movable ring 6. The spacing of the two ends of the protective part 12 formed by the slot makes it possible to increase its internal diameter in order to mount it on the movable ring 6. Once mounted, the protective part 12 returns to its equilibrium position by reducing its internal diameter and is positioned on the movable ring 6.

[0052] According to an alternative embodiment, the assembly 10 of movable ring 6 may comprise a plurality of protective parts, each protective part being positioned on one of the teeth of the external peripheral toothing 7.

[0053] In the embodiment illustrated in Figures 3 and 4, the external peripheral toothing 7 is surmounted by the protective part 12. The protective part 12 comprises a first portion 12a configured to cover the outer 7b and inner 7a faces of the teeth of the external peripheral toothing 7. The protective part 12 thus matches the shape of the external peripheral toothing 7.

[0054] In addition, the movable ring 6 may comprise a hook 13 arranged in the extension of the inner face 7a of the teeth of the external peripheral toothing 7, configured to receive the seal 9.

[0055] The protective part 12 may, advantageously, comprise a second portion 12b provided with a hook 14 configured to match the shape of the movable ring 6 and to be integrated at least partly into the hook 13 arranged on the movable ring 6. The hook 14 of the protective part 12 then allows the integration of the sealing joint 9.

[0056] Preferably, the protective part 12 comprises a retaining means for holding it on the external peripheral toothing 7. The retaining means is preferably configured for blocking the protective part 12 in order to prevent it from escaping radially under centrifugal force.

[0057] In this respect, in the example illustrated, the hook 14 of the protective part 12 also allows the protective part 12 to be locked on the movable ring 6 to prevent its radial escape by centrifugal force during rotation of the movable ring 6.

[0058] In addition, the hook 14 of the second portion 12b of the protective part 12 preferably comprises an oblique part 14a for receiving the seal 9. The oblique part extends in a direction opposite to the axis of rotation of the movable ring 6, in the direction of the blade roots 3.

[0059] In this way, the seal integrated in the hook 14 of the protection element 12 and resting on the oblique part 14 is encouraged to rise under the centrifugal effect to obstruct the axial clearance between the movable ring 6 and the rotor disc 1 created by the opening of the movable ring 6 when hot. This prevents in particular ventilation air leaks.

Claims

Claims

1. Movable ring assembly for a turbomachine rotor, the movable ring (6) comprising an external peripheral toothing (7), each tooth of the external peripheral toothing (7) comprising an inner face (7a) intended to be positioned opposite a blade root (3) of the rotor and an outer face (7b) opposite the inner face (7a) and intended to be positioned opposite an axial retaining hook (4) arranged on the blade root (3), characterized in that it comprises at least one protective element (11; 12) arranged on the outer face (7b) of at least one tooth of the external peripheral toothing (7).

2. A movable ring assembly according to claim 1, wherein the protective element is a coating (11) applied to the outer face (7b) of the teeth.

3. A movable ring assembly according to claim 2, wherein the material of said coating (11) comprises nickel and chromium.

4. A movable ring assembly according to claim 2 or 3, wherein the outer face (7b) of the teeth comprises a machined portion on which said coating (11) is applied.

5. A movable ring assembly according to claim 1, wherein the protective member is a protective piece disposed on the movable ring.

6. A movable ring assembly according to claim 5, comprising a plurality of protective pieces, each protective piece being positioned on one of the teeth of the external peripheral toothing (7).

7. A movable ring assembly according to claim 5, wherein the protective piece extends around the entire circumference of the outer peripheral toothing (7) of the movable ring, the protective piece comprising a slot.

8. A movable ring assembly according to any one of claims 5 to 7, wherein the outer peripheral toothing (7) is surmounted by the protective part, the protective part comprising a first portion configured to cover the outer and inner faces of the teeth of the outer peripheral toothing (7).

9. A movable ring assembly according to claim 8, wherein the movable ring comprises a hook arranged in the extension of the inner face of the teeth of the external peripheral toothing (7) and configured for receiving a seal (9), a second portion of the protective part comprising a hook configured to integrate at least partially into the hook arranged on the movable ring.

10. Movable ring assembly according to claim 9, wherein the hook (14) of the second portion (12b) of the protective part (12) comprises an oblique part (14a) for receiving a seal (9) and extending in a direction opposite to the axis of rotation of the movable ring (6).

11. Turbomachine rotor comprising a plurality of blades (2) each comprising a blade root (3) provided with an axial retaining hook (4), characterized in that it further comprises a movable ring assembly (6) according to any one of the preceding claims, the inner and outer faces of each tooth of the external peripheral toothing (7) of the movable ring being respectively positioned opposite a blade root (3) and opposite an axial retaining hook.

12. Turbomachine, comprising a rotor according to claim 11.

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