Flexible movable ring for gas turbine

Abstract

Flexible movable ring for gas turbine. The movable ring (120) comprises an upstream flange (200), a downstream flange (180), and a radial mounting flange (170) connected to a downstream portion, preferably a downstream end (181) of the downstream flange (180), by an intermediate portion (300). This intermediate portion helps to spread the temperature gradient between the hot and cold zones of the movable ring and to reduce thermomechanical stresses in the radial mounting flange at the bolted connection (9). The intermediate portion (300) is connected to the downstream flange (180) by a curved portion (303). These three elements form an assembly whose cross-section is in the shape of a U lying approximately along the longitudinal axis (XX') of the movable ring (120), which provides flexibility in the structure of the movable ring (120) and reduces thermomechanical stresses in the bolted connection (9). Figure to be published with the abbreviation: Figure 4

Description

Title of the invention: Flexible moving ring for gas turbine TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of turbomachines, in particular that of low pressure gas turbine modules of a turbomachine.

[0002] The present invention relates more specifically to a movable ring provided at the junction between two successive rotor discs of a low pressure gas turbine module. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] In a turbojet or turboprop, the gas turbines recover part of the kinetic energy of the gases leaving the combustion chamber in order to ensure the operation of the fan, the compressor and the accessories, or to drive the turbine shaft, the compressor as well as various accessories in a turboprop.

[0004] The gas turbine module 1 according to the prior art shown in longitudinal section in [Fig.l], comprises a distributor formed of a plurality of fixed blades 2 located in a flow stream 3, and a moving wheel formed of a plurality of moving blades 4 also located in the flow stream 3. Each moving blade 4 is mounted by its root in a cell 5 of a rotor disk 6 centered on the longitudinal axis XX' of the turbine. The rotor disks 6 are assembled together by upstream 7 and downstream 8 shells which are fixed together by bolted connections 9 passing through fixing flanges 10 and 11 of said shells 7 and 8. These rotor disks 6 are connected to the turbine shaft (not shown).

[0005] As can be seen in [Fig.2], a movable ring 12 is further provided at the junction between each successive rotor disc 6, opposite the corresponding fixed blade 2.

[0006] Each movable ring 12 preferably comprises wipers 13 provided opposite a block of abradable material 14 fixed at the free end of a sealing ring 15, this sealing ring 15 being mounted on the internal annular surface of each fixed blade 2 in order to limit the passage of gas between the tips of said blades 2 and the external casing.

[0007] Each movable ring 12 is fixed in the bolted connection 9 by a radial fixing flange 17, for example clamped between the fixing flanges 10 and 11 of the ferrules 7 and 8. The radial fixing flange 17, as well as the bolted connection 9, are usually located substantially halfway between two successive rotor discs 6.

[0008] Each movable ring 12 also comprises a downstream flange 18 which comes into support against a downstream retaining ring 19 provided to bear against a part provided downstream of the movable ring 12, at the level of a cell 5, this part being for example a rotor disc 6 and / or a movable blade 4.

[0009] Finally, certain mobile rings 12 comprise an upstream flange 20, bearing against an upstream retaining ring 21 provided to bear against a part provided upstream of the mobile ring 12, at the level of a cell 5, this part being for example a rotor disk 6 and / or a mobile blade 4.

[0010] The downstream 19 and upstream 21 retaining rings are intended to retain the moving blades 4, which are pushed by the fluid towards the downstream of the turbine.

[0011] In conventional mobile rings 12, the downstream flange 18 and the upstream flange 20 extend substantially along the longitudinal axis XX', with one end curved radially inwards to bear respectively on the downstream retaining ring 19 and on the upstream retaining ring 21. The radial flange 17 extends radially in a rectilinear manner from a substantially median portion situated between the downstream flange 18 and the upstream flange 20.

[0012] The role of each mobile ring 12 is multiple: • Firstly, it ensures radial sealing with the fixed blade 2 located opposite, preventing the fluid from slipping under the flow vein 3. • On the other hand, it ensures that the retaining rings 19 and 21 are held in their respective fixings, blocking the axial translation of the moving blades 4, while providing axial sealing with the retaining ring 19 and 21 associated with it. • Finally, it protects the shells 7 and 8 of the rotor discs 6 from the high temperatures coming from the flow vein 3.

[0013] Thus, the movable rings 12 regulate the pressure difference between the “hot” air coming from the flow vein 3 and the “cold” air coming from the cavity 22 located on the internal side of each rotor disc 6.

[0014] Consequently, during operation of the gas turbine module 1, the bolted end of the fixing flanges 10 and 11 of the shells 7 and 8 and of the radial fixing flange 17 of the movable rings 12 are at a so-called "cold" temperature because it is much lower than the so-called "hot" temperature of the external middle part of the movable rings 12. In [Fig. 3] the "cold" bolted ends are shown with horizontal hatching, while the "hot" external middle part of the movable rings 12, which is the part located between the downstream flange 18 and the upstream flange 20 where the radial fixing flange 17 is connected, is shown with vertical hatching.

[0015] During operation of the turbine, the “cold” parts undergo a low expansion, while the “hot” parts undergo a significant expansion. This difference in expansion results in strong thermomechanical constraints, in particular in the radial fixing flange 17 of the movable rings 12.

[0016] The expansion of the external middle part of the movable rings 12 tends to pull the bolted connection 9 outwards, that is to say away from the turbine shaft, inducing significant stresses in the flanges 18 and 20 of the rotor discs 6.

[0017] Furthermore, the centrifugal force associated with the mass of each movable ring 12 also contributes to significant stresses in the fixing flanges 10 and 11 of the rotor discs 6.

[0018] These different constraints tend to reduce the service life of the rotor discs 6, which affects the performance of the turbomachine.

[0019] There is therefore a need to increase the service life of the rotor discs 6. Summary of the invention

[0020] In order to provide a solution to the problems mentioned above and to reduce in particular the stresses in the fixing flanges of the rotor disks and in the radial fixing flange of the moving rings, the invention provides a new architecture for the moving rings, which tends to reduce the thermal gradient in them and allows the external middle part of the moving rings to expand without pulling the bolted connection outwards. The proposed invention consists of connecting the fixing flange of the moving ring to the downstream part of the downstream flange, instead of connecting it to the substantially central part located between the upstream flange and the downstream flange.

[0021] One aspect of the invention relates to a movable ring for a turbomachine with a longitudinal axis XX', comprising a radial fixing flange as well as an upstream flange and a downstream flange located respectively at the upstream and downstream ends of the movable ring and connected to each other by a joining part, where the radial flange is connected to a downstream part of the downstream flange by an intermediate part distinct from the joining part, and where the joining part comprises at least one sealing element.

[0022] Such a movable ring is shown in [Fig.4]. The intermediate part makes it possible to spread the temperature gradient existing between the “hot” and “cold” zones of the movable ring. The radial fixing flange is thus connected to the downstream flange by means of an intermediate part having an “intermediate” temperature, which advantageously reduces the thermomechanical stresses in the radial fixing flange, in particular at the bolted connection.

[0023] In [Fig.5], the "hot" zone is represented with vertical hatching, the zone “cold” by horizontal hatching and the “intermediate” temperature zone by a grid.

[0024] Furthermore, all of the functionalities of the movable ring are unchanged. Any supports of the upstream and downstream flanges on the retaining rings are unchanged, as is the mounting of the movable ring on the bolted connection.

[0025] Finally, the manufacturing process of the movable ring by turning, milling and / or drilling can generally remain similar, apart from geometric modifications. The movable ring according to the invention can therefore very easily replace a movable ring according to the prior art.

[0026] According to one aspect of the invention, the radial flange is connected to a downstream end of the downstream flange by the intermediate portion. This configuration advantageously makes it possible to increase the length of the intermediate portion, which spreads the preceding temperature gradient over a greater extent.

[0027] According to another aspect of the invention, the radial flange, the downstream flange, the upstream flange and the intermediate part are in one piece, which in particular makes it possible to reduce the manufacturing costs of the movable ring and to facilitate its assembly and maintenance.

[0028] According to an additional aspect of the invention, the intermediate part is connected to the downstream flange by a curved part, the intermediate part, the downstream flange and the curved part forming an assembly whose cross-section is in the shape of a U lying substantially along the longitudinal axis XX'. This conformation advantageously provides flexibility in the structure of the movable ring, which reduces the thermomechanical stresses in the bolted connection. Indeed, the U-shape provides an elastically deformable character to the movable ring.

[0029] According to one aspect of the invention, the upstream flange comprises a first part extending downstream substantially along the longitudinal axis XX' and connected to the joining part. Thus, the upstream flange can in particular be equipped with wipers provided opposite a block of abradable material in a conventional manner.

[0030] According to another aspect of the invention, at an upstream end, the upstream flange comprises a second part curved radially outwards or inwards, which allows it in particular to come to bear on a retaining ring in a conventional manner.

[0031] According to an additional aspect of the invention, the downstream flange comprises a part extending upstream substantially along the longitudinal axis XX' and connected to the junction part, which in particular makes it possible to provide radial orifices in this part extending upstream.

[0032] According to one aspect of the invention, at least one sealing element is in the form of a lip extending outwards, which advantageously makes it possible to limit the passage of gas between the tips of the blades and the outer casing in a conventional manner.

[0033] Another aspect of the invention relates to a turbomachine comprising a plurality of rotor discs and at least one movable ring as described above and located between two successive rotor discs. Such a turbomachine thus has a longer service life for the rotor discs, for better performance.

[0034] According to one aspect of the invention, at least one movable ring is mounted by its flange radial between two successive rotor discs by a bolted connection. Thus, the movable ring can advantageously be fixed in a conventional manner, without having to modify the rest of the turbomachine in any way.

[0035] The invention and its various applications will be better understood upon reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0036] The figures are presented for information purposes only and in no way limit the invention.

[0037] [Fig.l] represents a gas turbine module of a turbomachine according to the prior art.

[0038] [Fig.2] represents an enlarged part of the framed part in [Fig.l] illustrating a movable ring according to the prior art, the other parts being represented in ghost lines.

[0039] [Fig.3] is a view similar to [Fig.2], where the “cold” zones are represented with horizontal hatching while the “hot” zone of a movable ring according to the prior art is represented with vertical hatching.

[0040] [Fig.4] is a view similar to [Fig.2], but illustrating a movable ring according to the invention, the other parts being represented in phantom lines.

[0041] [Fig.5] is a view similar to [Fig.4], where the "cold" zones are represented with horizontal hatching, the "hot" zone of the moving ring is represented with vertical hatching, while the intermediate zone, with reduced thermal gradient, is represented with a grid. DETAILED DESCRIPTION

[0042] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0043] By convention, in the present application, the terms "upstream" and "downstream" are defined with respect to the direction of air circulation in the turbomachine. Thus, upstream is located on the air inlet side (on the left in the figures), while downstream is located on the air outlet side (on the right in the figures). Similarly, the term "longitudinal" or "axial" corresponds to a direction parallel to the longitudinal axis XX' along which the turbomachine extends, while the term "radial" means a direction substantially perpendicular to the longitudinal axis XX'. Furthermore, in the present application, the terms "inner" and "outer", and "internal" and "external" are defined radially with respect to the longitudinal axis XX' of the turbomachine.Thus, a cylindrical part extending along the longitudinal axis XX' has an inner radial face facing the longitudinal axis XX' of the turbomachine and an outer radial face, opposite its inner face and facing the outer casing of the turbomachine.

[0044] It will be noted that the longitudinal axis XX' is the same for the turbomachine and for the movable ring according to the invention.

[0045] The invention relates to a movable ring 120, capable of being mounted in a gas turbine module 1 of a turbomachine, in place of a conventional movable ring 12, at the junction between two successive rotor disks 6, opposite a corresponding fixed blade 2.

[0046] Conventionally, the movable ring 120 comprises an upstream flange 200, a downstream flange 180 and a radial fixing flange 170, the movable ring extending between said upstream flange 200 and said downstream flange 180. The upstream flange 200 and the downstream flange 180 are connected by a joining portion 125.

[0047] The downstream flange 180 is preferably provided to come into contact with a rotor disk 6 and / or a moving blade 4, for example by means of a downstream retaining ring 19, preferably at the level of a cell 5.

[0048] The upstream flange 200 is preferably provided to come into contact with a rotor disk 6 and / or a moving blade 4, for example by means of an upstream retaining ring 21, preferably at the level of a cell 5.

[0049] The radial fixing flange 170 is preferably provided for fixing the movable ring 120 between two rotor disks 6, for example by being clamped between the fixing flanges 10 and 11 of the upstream 7 and downstream 8 shells of the two adjacent rotor disks 6, and assembled to them by a bolted connection 9. For this purpose and in a conventional manner, the radial fixing flange 170 has a plurality of through-orifices extending along the longitudinal axis XX'.

[0050] The movable ring 120 according to the invention is characterized in that the radial flange 170 is connected to a downstream part of the downstream flange 180 by an intermediate part 300.

[0051] Preferably, the radial flange 170 is connected to a downstream end 181 of the downstream flange 180 by the intermediate part 300.

[0052] The radial flange 170, the downstream flange 180, the upstream flange 200 and the intermediate part 300 are preferably in one piece.

[0053] According to a preferred embodiment, the intermediate part 300 has: • a first part 301 curved radially inwards and connected to the radial flange 170, • a middle part 302 extending downstream substantially along the longitudinal axis XX', and • a second part 303 curved radially outwards and connected to the downstream end of the downstream flange 180.

[0054] According to this preferred embodiment, the intermediate part 300 is connected to the downstream flange 180 by the curved part 303. Thus, the intermediate part 300, the downstream flange 180 and the curved part 303 form an assembly whose cross-section is in the shape of a U lying substantially along the longitudinal axis XX'.

[0055] Preferably, the upstream flange 200 comprises a first part 201 extending downstream and substantially along the longitudinal axis XX' to form an upstream part of the joining part 125. At an upstream end, the upstream flange 200 may comprise a second part 202 curved radially outwards or inwards, for example to bear against the upstream retaining ring 21.

[0056] The junction part 125 or the upstream flange 200 may comprise a through orifice 203 which has the function of calibrating the flow rate of the air flow passing from the cavity 22 located on the internal side of each rotor disk 6, towards the external cavity located on the side of the flow vein 3, from where it will return towards said flow vein 3 after having cooled the cells 5 of the rotor disk 6 upstream.

[0057] Preferably, the downstream flange 180 comprises a part 182 extending upstream and substantially along the longitudinal axis XX' to form a downstream part of the junction part 125.

[0058] Conventionally, the junction portion 125, the downstream flange 180 and / or the upstream flange 200 may comprise at least one sealing element 135, preferably two, for example known as a labyrinth seal, and preferably in the form of a wiper 130, extending outwards and provided opposite a block of abradable material 14 fixed at the free end of a sealing ring 15 mounted on the internal annular surface of each fixed blade 2. At least one wiper 130 may be provided in the portion 182 extending upstream of the downstream flange 180 or in the first portion 201 extending downstream of the upstream flange 200.

[0059] The invention can be used within any type of gas turbine engine, for example a turbojet, a turboprop or a turboshaft engine. It also relates to a turbomachine comprising at least one movable ring 120 as described above. A turbomachine may comprise such a movable ring 120 between each of the rotor disks 6, the movable ring 120 being preferably mounted by its radial flange 170 between two successive rotor disks 6 by a bolted connection 9.

Claims

Claims

1. Movable ring (120) for a turbomachine with a longitudinal axis (XX'), comprising a radial fixing flange (170) as well as an upstream flange (200) and a downstream flange (180) located respectively at the upstream and downstream ends of the movable ring (120) and connected to each other by a junction part (125), characterized in that the radial flange (170) is connected to a downstream part of the downstream flange (180) by an intermediate part (300) separate from the junction part (125) and in that the junction part (125) comprises at least one sealing element (135).

2. Movable ring (120) according to claim 1, characterized in that the radial flange (170) is connected to a downstream end (181) of the downstream flange (180) by the intermediate part (300).

3. Movable ring (120) according to claim 1 or 2, characterized in that the radial flange (170), the downstream flange (180), the upstream flange (200) and the intermediate part (300) are in one piece.

4. Movable ring (120) according to any one of the preceding claims, characterized in that the intermediate part (300) is connected to the downstream flange (180) by a curved part (303), the intermediate part (300), the downstream flange (180) and the curved part (303) forming an assembly whose cross-section is in the shape of a U lying substantially along the longitudinal axis (XX').

5. Movable ring (120) according to any one of the preceding claims, characterized in that the upstream flange (200) comprises a first part (201) extending downstream substantially along the longitudinal axis (XX') and connected to the junction part (125).

6. Movable ring (120) according to any one of the preceding claims, characterized in that at an upstream end, the upstream flange (200) comprises a second part (202) curved radially outwards or inwards.

7. Movable ring (120) according to any one of the preceding claims, characterized in that the downstream flange (180) comprises a part (182) extending upstream substantially along the longitudinal axis (XX') and connected to the junction part (125).

8. Movable ring (120) according to any one of the preceding claims, characterized in that at least one sealing element (135) is in the form of a lip (130) extending outwards.

9. Turbomachine comprising a plurality of rotor discs (6), characterized in that it comprises at least one movable ring (120) according to one of the preceding claims and located between two successive rotor discs (6).

10. Turbomachine according to the preceding claim, characterized in that the at least one movable ring (120) is mounted by its radial flange (170) between two successive rotor discs (6) by a bolted connection (9).

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