Weighted mobile ring for a gas turbine

Abstract

One aspect of the invention relates to a mobile ring (120) for a turbomachine, comprising an upstream flange (200), a downstream flange (180) and a radial fastening flange (170), wherein: - the upstream flange (200) and downstream flange (180) each extend along a longitudinal axis (XX'); - the upstream flange (200) and downstream flange (180) are each extended by a radial arm, respectively an upstream radial arm (240) and a downstream radial arm (230) which extend towards the outside of the mobile ring (120), perpendicularly to the longitudinal axis (XX'); - the radial fastening flange (170) extends towards the inside of the mobile ring (120), perpendicularly to the longitudinal axis (XX'); and characterized in that the radial flange (170) has an edge face (300) equipped with at least one weight (400).

Description

weighted movable ring for gas turbine TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of turbomachinery, 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, gas turbines recover some of the kinetic energy of the gases exiting the combustion chamber in order to ensure the operation of the fan, compressor and accessories, or to drive the turbine shaft, compressor and various accessories in a turboprop.

[0004] The gas turbine module 1, according to the prior art shown in longitudinal section in [Fig. 1], comprises a distributor formed by a plurality of fixed blades 2 located in a flow channel 3, and a runner formed by a plurality of movable blades 4 also located in the flow channel 3. Each movable blade 4 is mounted by its base in a recess 5 of a rotor disk 6 centered on the longitudinal axis XX' of the turbine. The rotor disks 6 are joined together by upstream ferrules 7 and downstream ferrules 8, which are secured to each other by bolted connections 9 passing through upstream 10 and downstream 11 mounting flanges of said ferrules 7 and 8. These rotor disks 6 are connected to the turbine shaft (not shown).

[0005] As can be seen on [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 includes slats 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.

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

[0008] Each movable ring 12 also includes a downstream flange 18 bearing against a downstream retaining ring 19 provided bearing against a part provided downstream of the movable ring 12, at the level of a cavity 5, this part being for example a rotor disc 6 and / or a movable blade 4.

[0009] Finally, some movable rings 12 have an upstream flange 20, bearing against an upstream retaining ring 21 provided to bear against a part provided upstream of the movable ring 12, at the level of a cavity 5, this part being for example a rotor disc 6 and / or a movable blade 4.

[0010] The upstream flange 20 and downstream flange 18 usually extend each along the longitudinal axis XX' of the turbine.

[0011] The downstream retaining rings 19 and upstream 21 are intended to retain the moving blades 4, which are pushed by the fluid downstream of the turbine.

[0012] The downstream flange 18 and the upstream flange 20 of the movable ring 12 each typically have an end curved radially outwards from the movable ring 12 to bear against the downstream retaining ring 19 and the upstream retaining ring 21, respectively. These curved ends are in the form of radial arms 23, 24 extending substantially radially outwards from the movable ring 12, that is, perpendicularly to the longitudinal axis XX' of the turbine. Thus, a downstream radial arm 23 extends from the downstream flange 18, and an upstream radial arm 24 extends from the upstream flange 20.

[0013] The radial flange 17 usually extends radially into the movable ring 12 from a substantially median part located between the downstream flange 18 and the upstream flange 20.

[0014] Each movable ring 12 has multiple roles: Initially, 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 remain in their respective fixings, blocking the axial translation of the movable blades 4, while providing axial sealing with the associated retaining ring 19 and 21. Finally, it protects the ferrules 7 and 8 of the rotor discs 6 from the high temperatures coming from the flow vein 3.

[0015] 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 inner side of each rotor disc 6.

[0016] Therefore, during the operation of the gas turbine module 1, at the bolted connection 9, the ends of the fixing flanges 10 and 11 of the ferrules 7 and 8 and of the radial fixing flange 17 of the movable rings 12 are at a temperature which is called "cold" because it is much lower than the temperature which is called "hot" of the external middle part of the movable rings 12. On [Fig. 3], the aforementioned "cold" ends are represented with horizontal hatching, while the external "hot" 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 represented with vertical hatching.

[0017] During turbine operation, the "cold" parts undergo slight expansion, while the "hot" parts undergo significant expansion. This difference in expansion results in high thermomechanical stresses CT, particularly in the radial mounting flange 17 of the moving rings 12. These thermomechanical stresses CT are represented by a circled area in [Fig. 3]-

[0018] The expansion of the outer middle portion of the movable rings 12 tends to pull the bolted joint 9 outwards, i.e. away from the turbine shaft. This radial displacement ER of the bolted joint 9 outwards is represented by a thick black arrow in [Fig. 3].

[0019] The radial displacement ER of the bolted joint 9 outwards induces significant mechanical stresses CM in the flanges 18 and 20 of the rotor discs 6. These mechanical stresses CM are particularly present in the connecting portions that link the fixing flanges 10 and 11 to the rest of the ferrule body 7, 8 where they are represented by a circled area on [Fig. 3].

[0020] In addition, the centrifugal force Ec associated with the mass of each moving ring 12 also contributes to significant thermomechanical stresses CT in the mounting flanges 10 and 11 of the rotor discs 6 and in the radial mounting flange 17 of the moving rings 12.

[0021] This centrifugal force Ec is represented by a thick hatched arrow in [Fig. 3]. It also tends to radially deform the downstream radial arm 23 and the upstream radial arm 24 of the movable rings 12 in the direction of the flow channel 3 and moves said radial arms 23, 24 (referenced in [Fig. 2]) away from the retaining rings 19, 21 on which they rest. These deformations D are each represented by a thick white arrow in [Fig. 3].

[0022] The deformations D of the radial arms 23, 24 of the movable rings 12 generate passages P for hot air from the flow stream 3 towards the radial mounting flange 17. These passages P are represented by a thin arrow in [Fig. 3]. This hot air circulation is undesirable in gas turbines. Indeed, it represents thermal leakage between the upstream radial arms 24 and downstream radial arms 23 of the movable ring 12 and the upstream retaining rings 21 and downstream retaining rings 19.

[0023] The various mechanical stresses CM and thermomechanical stresses CT, as well as the deformations D of the moving rings 12, also tend to reduce the service life of the flange holes 26, scallops 25 and connecting radii 26 of the upstream 10 and downstream 11 fixing flanges of the rotor discs 6, which are illustrated on [Fig. 4],

[0024] The reduced lifespan of the aforementioned parts affects the performance of the turbomachine.

[0025] Therefore, there is a need to increase the lifespan of rotor discs 6. SUMMARY OF THE INVENTION

[0026] The invention offers a solution to the problems mentioned above, by seeking to reduce the deformations D of the radial arms 23, 24 of the movable rings 12, which makes it possible to reduce the deformations at the bolted connection 9, in particular to reduce the leakage sections and flange openings in operation.

[0027] One aspect of the invention relates to a movable ring for a turbomachine, comprising an upstream flange, a downstream flange and a radial fixing flange, in which: the upstream and downstream flanges each extend along a longitudinal axis XX'; the upstream and downstream flanges are each extended by a radial arm, respectively an upstream radial arm and a downstream radial arm which extend outwards from the movable ring, perpendicular to the longitudinal axis XX'; the radial fixing flange extends inwards from the movable ring, perpendicular to the longitudinal axis XX'; and the radial flange has an edge equipped with at least one counterweight.

[0028] Adding extra mass inside the rotating ring modifies the seal by reducing the tension on the bolted connection. This addition reduces or prevents deformation of the rotating ring caused by centrifugal force during operation. This, in turn, reduces mechanical stress in the disc flanges, thereby minimizing leakage and the risk of the bolted connection opening outwards. Adding weights thus advantageously reduces stress in areas of critical lifespan while maintaining engine performance. Consequently, adding one or more weights significantly increases the lifespan of the rotor discs connected to the rotating ring via the bolted connection, whose mechanical behavior is improved.

[0029] It should also be noted that adding one or more weights inside the moving ring is a technology that is very simple to implement, which does not require modification of the mounting range, nor changes in the geometry of adjacent parts.

[0030] According to one aspect of the invention, the radial flange extends radially outwards from the movable ring, from a substantially median portion located between the upstream and downstream flanges. This advantageously prevents the generation of imbalances in the movable ring and allows access to the upstream and downstream sides of the bolted connection between two successive rotor discs.

[0031] According to another aspect of the invention, the radial flange comprises a single weight extending over all or almost all of its edge. This embodiment advantageously simplifies the design of the movable ring and the weight, particularly when these two elements are made of a single piece.

[0032] According to a further aspect of the invention, the radial flange comprises several weights evenly distributed along its edge. Using multiple weights allows, for example, the use of generic weights for different moving rings by simply adjusting their number, their even distribution advantageously preventing the generation of imbalances in the moving ring.

[0033] According to one aspect of the invention, the edge of the radial flange comprises a series of scallops distributed around its periphery, each scallop having a through-hole and being equipped with a weight located towards the inside of the movable ring relative to the through-hole. This embodiment advantageously allows the use of pre-existing scallops to equip a movable ring with weights.

[0034] According to another aspect of the invention, the radial flange, the downstream flange, the upstream flange, and at least one counterweight are formed from a single piece. This advantageously simplifies the manufacture of the moving ring and the counterweights, and in particular prevents the counterweights from separating, which could then cause serious damage to the turbomachine.

[0035] According to a further aspect of the invention, at least one weight is fixed to the edge of the radial flange. This advantageously allows the position of the weights on the movable ring to be replaced and / or modified, these operations being all the easier when the fixing is removable.

[0036] According to one aspect of the invention, the fixing of at least one weight on the edge of the radial flange is carried out by bolting, screwing, gluing, welding or brazing.

[0037] According to another aspect of the invention, at least one weight is made of a nickel-based alloy. Indeed, this type of metal alloy is advantageously durable, resistant to corrosion and high temperatures, and withstands high temperatures while resisting creep.

[0038] According to a further aspect of the invention, the total mass added by the weight(s) is between 2 and 10 kg, preferably between 4 and 7 kg, and more preferably between 4.5 and 5.5 kg. Indeed, an additional mass of approximately 5 kg appears to significantly improve the mechanical behavior of the bolted connection of a movable ring equipping a low-pressure gas turbine module.

[0039] According to one aspect of the invention, the shape of at least one weight is symmetrical with respect to a plane orthogonal to the longitudinal axis XX', which advantageously avoids any phenomenon of imbalances in the moving ring.

[0040] Another aspect of the invention relates to a turbomachine comprising a plurality of rotor disks, which turbomachine includes at least one movable ring according to the invention as described above and located between two successive rotor disks. Advantageously, such a turbomachine features rotor disks with an increased service life.

[0041] According to one aspect of the invention, at least one movable ring is mounted by its radial flange between two successive rotor discs by means of a bolted connection.

[0042] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0043] The figures are presented for illustrative purposes only and are in no way limiting to the invention.

[0044] [Fig. 1] represents a turbomachine gas turbine module according to the prior art.

[0045] [Fig. 2] represents an enlarged part of the framed part on [Fig. 1] illustrating a movable ring according to earlier art, the other parts being represented in ghost lines.

[0046] [Fig. 3] is a similar view to [Fig. 2], where the "cold" and "hot" zones are shown, along with the various stresses, strains, deformations and hot air leaks that result from the operation of the turbomachine.

[0047] [Fig. 4] is a partial perspective view of a downstream fixing flange where a scallop, a through orifice and a connecting radius are illustrated.

[0048] [Fig. 5] is a view similar to [Fig. 2], but illustrating an example of a movable ring according to the invention, the other parts being represented in ghost lines.

[0049] [Fig. 6] is a partial perspective view of an example of a movable ring according to the invention comprising several weights distributed on its edge.

[0050] [Fig. 7] is a partial perspective view of an example of a movable ring according to the invention comprising a single weight on its edge. DETAILED DESCRIPTION

[0051] Unless otherwise specified, the same element appearing on different figures has a unique reference.

[0052] By convention, in this application, the terms "upstream" and "downstream" are defined with respect to the direction of airflow within the turbomachine. Thus, upstream is located on the air inlet side (left side in the figures), while downstream is located on the air outlet side (right side 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" refers to a direction substantially perpendicular to the longitudinal axis XX'. Furthermore, in this application, the terms "inside" and "outside," 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' comprises 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. It should be noted that the longitudinal axis XX' is the same for the turbomachine and for the movable ring according to the invention.

[0053] The invention relates to a movable ring 120, suitable for mounting in a gas turbine module of a turbomachine, in place of a conventional movable ring 12, at the junction between two successive rotor discs 6, opposite a corresponding fixed blade 2.

[0054] Typically, the movable ring 120 comprises an upstream flange 200, a downstream flange 180, and a radial mounting flange 170. These flanges 170, 180, and 200 may be circular. They are preferably annular. upstream flanges 200 and downstream flange 180 each extend along the longitudinal axis XX', while the radial fixing flange 170 extends radially towards the inside of the movable ring 120, perpendicular to the longitudinal axis XX' and preferably in a straight line.

[0055] The downstream flange 180 is preferably designed to bear against a rotor disc 6 and / or a moving blade 4, for example via a downstream retaining ring 19, preferably at the level of a cavity 5. For this purpose, the downstream flange 180 is extended by a downstream radial arm 230 which extends for example radially outwards from the moving ring 120, perpendicular to the longitudinal axis XX' to bear against the downstream retaining ring 19.

[0056] Similarly, the upstream flange 200 is preferably designed to bear against a rotor disc 6 and / or a moving blade 4, for example via an upstream retaining ring 21, preferably at the level of a cavity 5. For this purpose, the upstream flange 200 is extended by an upstream radial arm 240 which extends for example radially outwards from the moving ring 120, perpendicular to the longitudinal axis XX' to bear against the upstream retaining ring 21.

[0057] The radial mounting flange 170 is preferably designed to fix the movable ring 120 between two rotor discs 6, for example by being clamped between the mounting flanges 10 and 11 of the upstream 7 and downstream 8 ferrules of the two adjacent rotor discs 6, and assembled to them by a bolted connection 9. For this purpose, and in a conventional manner, the radial mounting flange 170 has a plurality of through holes 320 extending along the longitudinal axis XX'. The through holes 320, also known as flange holes, allow the passage of a screw 500 onto which a nut 600 is then screwed.

[0058] In a conventional manner, the downstream flange 180 and / or the upstream flange 200 may include at least one slit 130, preferably two, 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.

[0059] The movable ring 120 according to the invention is distinguished in that the radial flange 170 has an edge 300 equipped with at least one weight 400 (see [Fig. 5], [Fig. 6] and [Fig. 7]).

[0060] The edge is the thinnest or narrowest side of an object. The edge 300 of the radial flange 170 therefore represents its free edge. Since this edge 300 is no longer visible in [Fig. 5], [Fig. 6], and [Fig. 7] following the addition of a counterweight 400, it is represented by a dashed line in these figures.

[0061] A weight, or counterweight, is a small metallic mass acting by inertia, gravity, or centrifugal force in various devices, as defined by the National Center for Textual and Lexical Resources (CNRTL) for the field of mechanics. A 400 weight is therefore a small mass element that locally adds weight to a device.

[0062] The radial flange 170 extends preferentially radially outwards from the movable ring 120 from a substantially median part located between the upstream flange 200 and downstream flange 180.

[0063] According to an embodiment of the invention illustrated in [Fig. 6], the radial flange 170 comprises several weights 400 distributed regularly along its edge 300, itself in several parts.

[0064] According to another embodiment of the invention illustrated in [Fig. 7], the radial flange 170 comprises a single weight 400 which extends over all or almost all of its edge 300. By almost all of the edge 300 is meant more than 90%, or even more than 95%, of the total length of the edge 300. Indeed, a weight 400 is likely to have one or more interruptions or slots 350, and therefore may not be continuous over the entire edge 300.

[0065] In the case where the edge 300 of the radial flange 170 has a succession of scallops 310 distributed around its periphery, each scallop 310 may have a through-hole 320 and be fitted with a weight 400 located towards the inside of the movable ring 120 relative to the through-hole 320. Preferably, these are individual weights 400 for each scallop 310, although the same weight 400 may fit all or part of the scallops 310. The term "scallop" here refers to an area in which a Material removal is performed on a stress-neutral area. As a reminder, a scalloped edge is illustrated in [Fig. 4].

[0066] The radial flange 170, the downstream flange 180 and the upstream flange 200 are preferably made of a single piece.

[0067] According to one embodiment of the invention, at least one weight 400 is in one piece with the movable ring 120.

[0068] According to another embodiment of the invention, at least one weight 400 is fixed on the edge 300 of the radial flange 170.

[0069] It should be noted that it is possible to combine these two embodiments of the invention, with at least one weight 400 being in one piece with the movable ring 120 while at least one weight 400 is fixed on the latter.

[0070] The fixing of at least one weight 400 on the edge 300 of the radial flange 170 can be carried out by bolting, screwing, gluing, welding or brazing.

[0071] According to one embodiment of the invention, at least one weight 400 is made of the same material as the movable ring 120, for example in a nickel-based alloy.

[0072] Of course, the additional mass represented by the 400 weight(s) of the invention must be adapted to the dimensions and operating regime of the turbine.

[0073] For example, the total mass added by the 400 weight(s) can be between 2 and 10 kg, preferably between 4 and 7 kg and more preferably between 4.5 and 5.5 kg.

[0074] A simulation was carried out in the context of a LEAP 1 B type low pressure turbine where the total mass added by a single weight 400 extending over the entire edge 300 of the radial flange 170 is approximately 5 kg.

[0075] The estimated gain in stresses for adding a 400 weight of approximately 5 kg to the existing geometry of a LEAP 1 B type low pressure turbine is given in the table below.

[0076] [Table 1]

[0077] This stress gain estimate was made by analogy of compensation of centrifugal force induced by the additional retaining mass of the ring and by experience of the finite element models available to the depositor.

[0078] Based on this estimate, we can deduce that the addition of at least one weight 400 located towards the inside of the movable ring 120 tends to significantly improve the mechanical behavior of the bolted connection.

[0079] The shape of each weight 400 can be arbitrary, but is preferably symmetrical with respect to a plane orthogonal to the longitudinal axis XX'. As an example, each weight 400 can have a pentagonal cross-section, with a rectangular body 401 with rounded corners and a connection 402 which tapers outwards from the movable ring 120 to connect said body 401 to the edge 300 of the radial flange 170.

[0080] The simulation described above was performed with a body 401 having a width Le of approximately 8 mm and a height Hc of approximately 3 mm, and a connection 402 having a width Le of approximately 8 mm at its widest point and a width LR of approximately 3 mm at its narrowest point, with a height HR of approximately 2 mm. These dimensions are only non-limiting examples and do not necessarily reflect actual values.

[0081] Although the invention is initially intended for low-pressure gas turbines, it can be used in any type of gas turbine engine, for example, a turbojet, a turboprop, or a turboshaft engine. It also relates to a turbomachine comprising a plurality of rotor discs 6 and at least one movable ring 120 as described above. A turbomachine may include such a movable ring 120 between each of the rotor discs 6, the movable ring 120 preferably being mounted by its radial flange 170 between two successive rotor discs 6 by a bolted connection 9.

[0082] Although described through a number of examples, variants and embodiments, the movable ring and turbomachine according to the invention include various variants, modifications and improvements which will be obvious to a person skilled in the art, it being understood that these variants, modifications and improvements form part of the scope of the invention.

Claims

DEMANDS

1. A movable ring (120) for a turbomachine, comprising an upstream flange (200), a downstream flange (180) and a radial mounting flange (170), in which: - the upstream (200) and downstream (180) flanges each extend along a longitudinal axis (XX'); - the upstream (200) and downstream (180) flanges are each extended by a radial arm, respectively an upstream radial arm (240) and a downstream radial arm (230) which extend radially outwards from the movable ring (120), perpendicular to the longitudinal axis (XX'); - the radial fixing flange (170) extends radially inwards towards the movable ring (120), perpendicular to the longitudinal axis (XX'); and - characterized in that the radial fixing flange (170) has an edge (300) equipped with at least one weight (400).

2. Movable ring (120) according to claim 1, characterized in that the radial fixing flange (170) comprises a single weight (400) which extends over all or almost all of its edge (300).

3. Movable ring (120) according to claim 1, characterized in that the radial fixing flange (170) has several weights (400) distributed regularly along its edge (300).

4. Movable ring (120) according to the preceding claim, characterized in that the edge (300) of the radial fixing flange (170) has a succession of scallops (310) distributed around its periphery, each scallop (310) having a through orifice (320) and being equipped with a weight (400) located towards the inside of the movable ring (120) with respect to the through orifice (320).

5. Movable ring (120) according to any one of the preceding claims, characterized in that the radial fixing flange (170), the downstream flange (180), the upstream flange (200) and at least one weight (400) are of a single piece.

6. Movable ring (120) according to any one of the preceding claims, characterized in that at least one weight (400) is fixed on the edge (300) of the radial fixing flange (170).

7. A movable ring (120) according to the preceding claim, characterized in that the attachment of at least one weight (400) to the edge (300) of the radial mounting flange (170) is effected by bolting, screwing, bonding, welding, or brazing.

8. A movable ring (120) according to any one of the preceding claims, characterized in that the total mass added by the weight(s) (400) is between 2 and 10 kg, preferably between 4 and 7 kg, and more preferably between 4.5 and 5.5 kg.

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

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

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