Improved turbomachine rotor

Abstract

Turbomachine rotor comprising a movable ring (6) having an external peripheral toothing (7), and a plurality of blades (2) each having a blade root (3) provided with an axial retaining hook (4), the plurality of blades (2) being arranged on the external peripheral toothing (7) of the movable ring (6), each of the teeth of the external peripheral toothing (7) of the movable ring (6) being positioned opposite a groove (8) of one of the axial retaining hooks (4) of the blade root (3) with which said tooth is associated. Furthermore, at least one damping element (10, 16) extends between each tooth of the external peripheral toothing (7) of the movable ring (6) and the groove (8) of the associated axial retaining hook (4). Figure for abstract: Fig 2

Description

Title of the invention: Improved turbomachine rotor Technical field

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

[0002] More specifically, the invention relates to a turbomachine rotor as well as to a movable ring of a turbomachine rotor. 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 each tooth of the external peripheral teeth 7 is inserted into a groove 8 of one of the axial retaining hooks 4 with which the tooth is associated.

[0007] A sealing ring 9, arranged between the movable ring 6 and the axial retaining hook 4, 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 of the axial retaining hooks 4 and of the 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 protect the movable ring and to limit impacts in the axial retaining hook.

[0011] A turbomachine rotor is therefore proposed comprising a movable ring having an external peripheral toothing, and a plurality of blades each having a blade root provided with an axial retaining hook, the plurality of blades being arranged on the external peripheral toothing of the movable ring, each of the teeth of the external peripheral toothing of the movable ring being positioned opposite a groove of one of the axial retaining hooks of the blade root with which said tooth is associated.

[0012] Furthermore, at least one damping element extends between each tooth of the outer peripheral toothing of the movable ring and the associated axial retaining hook groove.

[0013] According to one characteristic, the damping element can be fixed on the external peripheral teeth of the movable ring.

[0014] According to an alternative, the damping element can be a part independent of the movable ring.

[0015] According to one embodiment, the damping element may comprise a free end inserted into the groove of the blade root axial retaining hooks, said free end comprising a folded portion including one or more folds and forming a boustrophedon structure.

[0016] According to another embodiment, the damping element may comprise a plurality of omega-shaped portions.

[0017] According to one characteristic, a plurality of damping elements can each extend between one of the teeth of the external peripheral toothing of the movable ring and the groove of the associated axial retaining hook.

[0018] According to an alternative, a single damping element extends over the entire external peripheral toothing of the movable ring, the single damping element extending between each of the teeth of the external peripheral toothing of the movable ring and the associated axial retaining hook groove.

[0019] The invention also relates to a movable rotor ring of a turbomachine, comprising an external peripheral toothing, each tooth of the external peripheral toothing being intended to be positioned opposite a groove of an axial retaining hook of a blade root with which said tooth is associated.

[0020] Furthermore, the external peripheral toothing comprises at least one damping element arranged on one of the teeth of the external peripheral toothing, the damping element being configured to extend between each tooth of the outer peripheral toothing of the movable ring and the associated axial retaining hook groove.

[0021] According to one characteristic, a plurality of damping elements, each of the damping elements can be fixed on one of the teeth of the external peripheral toothing of the movable ring.

[0022] According to an alternative, a single damping element can extend over the entire external peripheral toothing of the movable ring.

[0023] The invention also relates to a turbomachine comprising a rotor as described above. Brief description of the drawings

[0024] 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:

[0025] [Fig-1] is a sectional view of a turbomachine rotor according to the prior art.

[0026] [Fig.2] is a sectional view of the cold assembly of an axial retaining hook of a blade root and of an external peripheral toothing of a movable ring of a rotor comprising a damping element according to a first embodiment of the invention.

[0027] [Fig.3] is a sectional view of the hot assembly of an axial retaining hook of a blade root and an external peripheral toothing of a movable ring of a rotor comprising a damping element according to a first embodiment of the invention.

[0028] [Fig.4] is a sectional view of the cold assembly of an axial retaining hook of a blade root and an external peripheral toothing of a movable ring of a rotor comprising a damping element according to a second embodiment of the invention. Detailed description of an embodiment

[0029] Figures 2 and 3 illustrate a low pressure turbine stage of an aircraft turbomachine.

[0030] 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.

[0031] 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 in a dovetail, for their installation in axial grooves, also at the tail dovetail, machined on the rotor disc 1. Assembly is carried out by fitting the blade root 3 into the axial groove.

[0032] 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.

[0033] 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 external peripheral teeth 7.

[0034] 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 one of the axial retaining hooks 4 and inserted into a groove 8 of the axial retaining hook 4 with which the tooth is associated.

[0035] A sealing ring 9, arranged between the movable ring 6 and the axial retaining hook 4, limits air leaks.

[0036] After the blades 2 and the sealing ring 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.

[0037] 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 sealing ring 9 from disengaging upstream of the blades 2 during operation of the turbomachine.

[0038] The plurality of blades 2 of the rotor 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 one of the axial retaining hooks 4 of the blade root 3 with which said tooth is associated.

[0039] Furthermore, at least one damping element 10 extends between each tooth of the external peripheral toothing 7 of the movable ring 6 and the groove 8 of the associated axial retaining hook 4.

[0040] By damping element is meant an element capable of damping shocks and vibrations. In particular, the element is advantageously capable of damping the vibrations generated by the turbomachine and the shocks of the ring arm 5 of the movable ring 6 in the groove 8 of the axial retaining hook 4 of the blade root 3, in particular during the flight phases in the case of an aircraft.

[0041] The damping element 10 forms a dynamic damping means receiving the wear in place of the external peripheral toothing 7 of the movable ring 6 and in place of the axial retaining hook 4 of the blade root 3. In addition, the damping element 10 makes it possible to prevent the teeth of the external peripheral toothing 7 from breaking.

[0042] In the example illustrated in Figures 2 and 3, the movable ring 6 comprises a plurality of damping elements 10. The damping elements 10 are arranged in so that each extends between one of the teeth of the external peripheral toothing 7 of the movable ring 6 and the groove 8 of the axial retaining hook 4 with which the tooth is associated.

[0043] The plurality of damping elements 10 makes it possible to maintain the general shape of the movable ring 6 and in particular of its outer periphery.

[0044] According to the first embodiment illustrated, the damping element 10 comprises a first free end 10a inserted into the groove 8 of the axial retaining hooks 4 of the blade root 3. The first free end 10a advantageously comprises a folded portion including one or more folds and forming a bous-trophedon structure.

[0045] By boustrophedon is meant a structure folded so as to form two or more parts extending along parallel planes connected, for example, by portions of circles.

[0046] In the example illustrated, the damping element 10 is fixed to the external peripheral toothing 7 of the movable ring 6 via, in this example, a second end 10b.

[0047] The damping element 10 has a dynamic spring function allowing the damping of shocks and vibrations.

[0048] For example, the folded portion of the first end 10a may comprise first and second opposite surfaces 11 and 12 for pressing into the groove 8 of the axial retaining hooks 4.

[0049] Preferably, the damping element 10 is configured to maintain, when cold, a clearance between the damping element 10 and the groove 8 of the axial retaining hook 4, and configured to, when hot, be pressed against the groove 8.

[0050] In the example illustrated, when hot, the first and second surfaces 11 and 12 are pressed against opposite surfaces of the groove 8 defined, respectively by a bulbous portion 4a of the axial retaining hook 4 and against a portion 4b of contact with the rotor disc 1.

[0051] In the illustrated example, the damping element 10 comprises two folds, namely, starting from the second end 10b towards the first end 10a, a first part 13, a second part 14 and a third part 15 which are substantially parallel. The thickness from the first part 13 to a third part 15 decreases.

[0052] The number of folds and the thickness of the parts can be adapted and are dependent on the protection against shocks and vibrations to be applied.

[0053] According to a manufacturing example, the folded portion of the damping element 10 according to the first embodiment can be produced by successive cold forming using suitable tooling such as a holding blank clamp and press-type equipment in order to achieve the folds which, in this example, are 180°.

[0054] Preferably, the damping elements 10 are fixed to the movable ring 6 by brazing. This leads to simple repair and replacement.

[0055] According to an alternative, the damping elements 10 may be independent parts of the movable ring 6, further facilitating the replacement of the damping elements 10.

[0056] It is also possible to provide in another embodiment that instead of a plurality of damping elements 10, a single damping element 10 extends over the entire outer periphery of the movable ring, i.e. over the entire external peripheral toothing 7 of the movable ring 6. The single damping element 10 can thus extend between each of the teeth of the external peripheral toothing 7 of the movable ring 6 and each of the grooves 8 of the associated axial retaining hook 8.

[0057] According to a second embodiment illustrated in [Fig. 4], the damping element 16 is an independent part. A damping element 16 is inserted between each of the teeth of the external peripheral toothing 7 and each groove 8 of the axial retaining hook 4. The damping element 16 illustrated comprises a plurality of omega-shaped sections or, in other words, portions of a circle, connected to each other.

[0058] The illustrated damping element 16 comprises three omega-shaped portions 17, 18 and 19. The omega shape makes it possible to dampen shocks and vibrations.

[0059] Preferably, the external peripheral toothing 7 of the movable ring 6 is dimensioned so that, when it is mounted in the axial retaining hooks 4, the teeth have a pressing surface in the groove 8.

[0060] Preferably, each tooth is pressed in the groove 8 against the bulbous portion 4a of the axial retaining hook 4 and the damping elements 16 are pressed against the portion 4b in contact with the rotor disc 1 of the axial retaining hook 4.

[0061] It may also be provided that the damping element 16 is fixed to the external peripheral toothing 7.

[0062] The presence of the damping elements 10, 16 makes it possible to limit the umbrella movements of the ring arm 5 under the effect of heat during operation of the turbomachine and thus to limit the loss of the sealing ring 9.

[0063] According to another embodiment, it may be provided that the damping element(s) form a single piece with the external peripheral toothing 7 of the movable ring 6.

Claims

Claims

1. A turbomachine rotor comprising a movable ring (6) having an external peripheral toothing (7), and a plurality of blades (2) each having a blade root (3) provided with an axial retaining hook (4), the plurality of blades (2) being arranged on the external peripheral toothing (7) of the movable ring (6), each of the teeth of the external peripheral toothing (7) of the movable ring (6) being positioned opposite a groove (8) of one of the axial retaining hooks (4) of the blade root (3) with which said tooth is associated, characterized in that at least one damping element (10) extends between each tooth of the external peripheral toothing (7) of the movable ring (6) and the groove (8) of the associated axial retaining hook (4).

2. Rotor according to claim 1, wherein the damping element (10) is fixed on the external peripheral toothing (7) of the movable ring (6).

3. Rotor according to claim 1, in which the damping element (16) is a part independent of the movable ring (6).

4. Rotor according to any one of the preceding claims, in which the damping element (10) comprises a free end (10a) inserted into the groove (8) of the axial retaining hooks (4) of the blade root (3), said free end (10a) comprising a folded portion including one or more folds and forming a bous-trophedon structure.

5. A rotor according to any one of claims 1 to 3, wherein the damping element (16) comprises a plurality of omega-shaped portions.

6. Rotor according to any one of the preceding claims, comprising a plurality of damping elements (10, 16) each extending between one of the teeth of the external peripheral toothing (7) of the movable ring (6) and the groove (8) of the associated axial retaining hook (4).

7. A rotor according to any one of claims 1 to 6, wherein a single damping element extends over the entire outer peripheral toothing (7) of the movable ring (6), the single damping element extending between each of the teeth of the outer peripheral toothing (7) of the movable ring (6) and the associated axial retaining hook (4) groove (8).

8. Movable rotor ring of a turbomachine, comprising an external peripheral toothing (7), each tooth of the external peripheral toothing (7) being intended to be positioned opposite a groove (8) of an axial retaining hook (4) of a blade root (3) with which said tooth is associated, characterized in that the external peripheral toothing (7) comprises at least one damping element arranged on one of the teeth of the external peripheral toothing (7), the damping element (10) being configured to extend between each tooth of the external peripheral toothing (7) of the movable ring (6) and the groove (8) of the associated axial retaining hook (4).

9. A movable ring according to claim 8, comprising a plurality of damping elements (10), each of the damping elements being fixed to one of the teeth of the external peripheral toothing (7) of the movable ring (6).

10. Movable ring according to claim 8, comprising a single damping element extending over the entire external peripheral toothing (7) of the movable ring (6).

11. Turbomachine, comprising a rotor according to any one of claims 1 to 7.

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