Improved sealing assembly for turbomachine turbine

Abstract

Improved sealing assembly for a turbomachine turbine Sealing assembly for a turbomachine turbine (6), comprising a turbine distributor (20) centered on a central axis (X), comprising at least one fixed blade (24), an external platform (26) of the blade comprising an external upstream spoiler (264) for hooking onto an internal hook (12), and an internal upstream spoiler (261) forming with the external upstream spoiler (264) an annular groove (29), a sealing ring (30) comprising a plurality of ring sectors (32) mounted end to end around the central axis (X), two adjacent ring sectors (32) respectively comprising a first and a second slot (34) arranged opposite one another, a sealing plate (36) being arranged in the first and second slots,the distributor (20) comprising an axial protrusion (25) extending axially in the annular groove (29) so as to reduce an axial distance between the sealing ring (30) and the distributor (20), and being arranged axially opposite the sealing plate (36). Figure for the abstract: Fig. 4.,

Description

Title of the invention: Improved sealing assembly for a turbomachine turbine Technical field

[0001] The present disclosure relates to the field of aeronautical turbomachines, in particular the distributors and sealing rings of these turbomachines. The present disclosure relates more particularly to a sealing assembly for a turbomachine turbine, and a turbine comprising this sealing assembly. Prior art

[0002] A turbomachine turbine, for example a low-pressure turbine, conventionally comprises several rotor and stator stages. A stator stage comprises a distributor downstream of the rotor stage, and comprising a plurality of fixed blades, or rectifiers. A rotor stage comprises a movable wheel comprising a plurality of movable blades rotating about a central axis.

[0003] In order to limit the leaks of air flowing in the hot air flow stream and to ensure the sealing of the system, the heads of the moving blades of the rotor are generally equipped with wipers adapted to cut a track of abradable material carried by a sealing ring surrounding the moving wheel. The radial distance with a small clearance in operation of the wipers with respect to the abradable track during the rotation of the moving wheel makes it possible to have operation with high efficiency.

[0004] Such a sealing ring is typically formed from a plurality of ring sectors assembled end to end around the central axis to form the ring. Still with the aim of ensuring the thermal sealing of the system, the sealing ring is typically equipped with a plurality of sealing plates, or lamellae. These sealing plates, typically made of metal, are inserted into slots made inside each ring sector, so as to extend between two circumferentially adjacent ring sectors, improving the sealing between the latter.

[0005] Although these sealing plates effectively improve the sealing of the junction between two ring sectors, and therefore of the turbine module, they nevertheless have drawbacks. In particular, losses of sealing plates are regularly observed, particularly when the turbine module is turned over or placed vertically during handling phases, for example, the plates falling by gravity, or during tests on the engine, defects in the mounting of the plates can cause them to be expelled by the air flow leaving the engine.

[0006] In the event of loss of one or more sealing plates, the module must be completely dismantled to replace the plate(s), which generates additional costs. Furthermore, it may also happen that sealing plates are disengaged from their housings during operation of the engine. Disengagement or loss of plates during operation of the engine degrades the sealing between the ring sectors, which is detrimental to the service life of the surrounding parts, in particular the hooks of the fixed casing carrying the stator of the turbine. A disengaged sealing plate also constitutes a foreign body in the turbine which can damage the latter.

[0007] There is therefore a real need for a device for a turbomachine turbine which is free, at least in part, from the aforementioned drawbacks, and in particular making it possible to improve the retention of the sealing plates. Statement of the invention

[0008] The present disclosure relates to a sealing assembly for a turbomachine turbine extending around a central axis, the turbine comprising a fixed casing having at least one internal hook which extends radially projecting from the casing towards the central axis, the sealing assembly comprising: - a turbine distributor centered on the central axis and comprising at least one fixed blade extending between a radially internal platform and a radially external platform, the radially external platform comprising an external upstream spoiler capable of hooking onto the internal hook, and an internal upstream spoiler forming with the external upstream spoiler an annular groove, the external upstream spoiler being located radially outside relative to the internal upstream spoiler, - a sealing ring suitable for being fixed to the casing and which is intended to surround a rotor stage of the turbine, and comprising a plurality of ring sectors mounted circumferentially end to end around the central axis, a first and a second circumferentially adjacent ring sectors respectively comprising a first and a second slot, the first and the second slot being arranged circumferentially opposite each other, and a sealing plate comprising a first circumferential end arranged in the first slot and a second circumferential end arranged in the second slot, the distributor comprising an axial protuberance which extends axially projecting from the annular groove so as to reduce an axial distance between the sealing ring and the distributor, and being arranged axially opposite the sealing plate.

[0009] In this disclosure, the terms “axial”, “radial”, “circumferential”, "interior", "exterior" and their derivatives are defined relative to the central axis of the turbomachine, in other words the axis of rotation of the turbine. Furthermore, the terms "upstream" and "downstream" are defined in relation to the normal direction of air circulation in the turbomachine.

[0010] The external upstream spoiler is typically a portion of the platform extending upstream and outward from a main surface of the platform, so as to form a hook cooperating with an external face of the internal hook of the fixed casing and thus allowing the distributor to be held radially. The internal upstream spoiler of the platform may be located in the extension of its main surface, forming, with the external upstream spoiler, a clamp typically encompassing a portion of the sealing ring, and thus delimiting an annular groove. This annular groove forms a cavity open upstream.

[0011] The sealing ring can also be fixed to the internal hook of the fixed casing, and is typically interposed between the external upstream spoiler and the internal upstream spoiler of the platform, axially opposite the annular groove.

[0012] It is therefore understood that the fact of arranging an axial protuberance in the annular groove axially opposite the sealing plate makes it possible to fill at least in part the cavity formed by said annular groove, thus limiting the amplitude of possible axial displacement of the sealing plate. In other words, in the event of displacement of the sealing plate in its housing during operation of the engine or during a disassembly operation of the turbine module, its movement in the direction of the central axis is limited by the presence of the protuberance, the latter serving in particular as a stop preventing the plate from coming out further from its housing.

[0013] Thus, unlike the devices of the prior art in which the sealing plates can come out of their housing via the annular groove, the sealing plates of the sealing assembly of the present disclosure, during their axial movement downstream if necessary, come into contact with the distributor, in particular the axial protuberance, but do not have the space to come out of their housing.

[0014] It is thus possible to improve the sealing of the turbine module while limiting the risks of loss of sealing plates during operation of the engine, which makes it possible to limit the loss of sealing during operation, or during its disassembly, which facilitates maintenance operations and limits costs. Reducing the risk of loss of sealing plates also limits the risk of damage to the parts of the turbine, and therefore makes it possible to improve the service life of the latter.

[0015] In some embodiments, the axial protrusion extends axially from a bottom of the groove toward the sealing ring, the sealing ring being arranged upstream of the axial protrusion.

[0016] It is understood that the axial protrusion extends from the bottom of the annular groove upstream, that is to say towards the portion of the sealing ring comprising the sealing plate. This makes it possible to reduce the axial distance between said sealing plate and the distributor, and therefore to reduce the possible axial travel of the sealing plate.

[0017] In some embodiments, the axial protrusion extends circumferentially over a distance greater than a width of the sealing plate.

[0018] It is understood that the sealing plate has a plate shape having a first dimension, i.e. a length, in the axial direction, and a second dimension, i.e. a width, in the direction perpendicular to the axial direction. It is thus understood that the protuberance extends along the annular groove, in the bottom thereof, over a distance greater than said width of the sealing plate.

[0019] This makes it possible to improve the locking effect of the sealing plate by maximizing the contact surface between the edge of the plate and the axial protrusion, in the event of axial displacement of the plate. This also makes it possible to promote flat contacts and thus limit wear linked to these contacts.

[0020] In certain embodiments, the axial protrusion comprises a planar upstream end face of which at least a portion is arranged at the same radial position as the sealing plate.

[0021] Arranging the upstream end face at the same radial position as the sealing plate ensures that the sealing plate comes into contact with said upstream end face in the event of axial movement. Furthermore, the fact that the upstream end face is flat further promotes flat contacts between the sealing plate and the distributor, and thus further limits wear related to these contacts.

[0022] In some embodiments, the axial protrusion includes a recessed upstream face arranged further downstream than the upstream end face.

[0023] Thus, while the upstream end face makes it possible to get as close as possible to the portion of the sealing ring comprising the sealing plate, the recessed upstream face makes it possible to free up space, thus facilitating the integration of the distributor into the turbine, and limiting the quantity of material and therefore the mass of the assembly.

[0024] In some embodiments, the upstream end face of the axial protrusion is radial with respect to the central axis.

[0025] In other words, the upstream end face of the axial protrusion is perpendicular to a plane comprising the sealing plate. It is understood that the sealing plate has a plate shape forming a plane parallel to the central axis, and the upstream end face is inscribed in a radial plane perpendicular to the central axis. The fact that the plane comprising the upstream end face and the plane comprising the sealing plate are perpendicular to each other makes it possible, in the event of contact between the sealing plate and the upstream end face, to prevent vibrations from twisting the sealing plate. Indeed, in the event of vibration when the planes are perpendicular, the edge of the plate in contact with the axial protuberance slides on the upstream end face, whereas the plate would tend to bend if the upstream end face formed a non-right angle with it.

[0026] In some embodiments, an axial clearance between an upstream end of the axial protrusion and the sealing ring is less than 2 mm, preferably between 0.07 mm and 1.3 mm.

[0027] Preferably, the upstream end of the axial protuberance is the plane formed by the upstream end face. Providing an axial clearance of the order of 1 mm between the axial protuberance, in particular the upstream end face, and the portion of the sealing ring comprising the sealing plate, makes it possible to minimize the axial distance between the sealing ring and the distributor to obtain the aforementioned effects, while taking into account tolerances, expansions or possible movements of the parts between them.

[0028] In some embodiments, the assembly comprises a plurality of axial protrusions distributed circumferentially around the central axis, and in which each pair of circumferentially adjacent ring sectors respectively comprises a first and a second slot arranged circumferentially opposite one another and in which is housed a sealing plate comprising a first circumferential end disposed in the first slot and a second circumferential end disposed in the second slot, each axial protrusion being disposed axially opposite a sealing plate.

[0029] Preferably, the assembly comprises as many axial protrusions as there are sealing plates. This makes it possible to limit the movement of each sealing plate, while minimizing the quantity of material necessary to form the axial protrusions, and therefore minimizing the mass of the assembly.

[0030] In some embodiments, the assembly includes a single axial protrusion extending axially from a bottom of the annular groove toward the sealing ring around the entire circumference of the dispenser.

[0031] This configuration makes it possible to fill a significant volume of the cavity formed by the annular groove, and therefore to further limit the risks of loss or disengagement of a sealing plate.

[0032] The present disclosure also relates to a turbine comprising a sealing assembly according to any one of the preceding embodiments, the turbine being a low pressure turbine.

[0033] The present disclosure also relates to a turbomachine comprising such a turbine. Brief description of the drawings

[0034] The invention and its advantages will be better understood upon reading the detailed description given below of different embodiments of the invention given as non-limiting examples. This description refers to the appended pages of figures, in which:

[0035] [Fig-1] [Fig.l] represents a schematic view in longitudinal section of a tur bomachine;

[0036] [Fig.2A-2B] Image A of Figures 2A-2B schematically represents a view in an axial plane of a sealing assembly at an inter-sector according to the prior art, and image B schematically represents a view in a radial section plane BB of image A;

[0037] [Fig.3] [Fig.3] represents a longitudinal sectional view of a portion of a turbine according to the prior art, including a rotor stage and a stator stage;

[0038] [Fig.4] [Fig.4] represents a longitudinal sectional view of a turbine portion according to the invention, including a rotor stage and a stator stage;

[0039] [Fig.5] [Fig.5] represents a detailed view of a part V of the turbine portion of [Fig.4];

[0040] [Fig.6] [Fig.6] represents a perspective view of a turbine distributor sector according to the invention. Description of the embodiments

[0041] In the remainder of the description, the terms “upstream” and “downstream” are subsequently defined in relation to the direction of flow of the gases through a turbomachine, indicated by the arrow F in [Fig. 1], representing the flow of the hot gases in the combustion chamber 4. Furthermore, the terms “internal” and “external” are considered in a radial direction perpendicular to the central axis X.

[0042] [Fig. 1] illustrates a double-flow turbomachine 100 comprising in a known manner from upstream to downstream successively at least one fan S, a gas turbine engine part 1 successively comprising at least one low-pressure compressor stage 2, high-pressure compressor stage 3, a combustion chamber 4, at least one high-pressure turbine stage 5 and low-pressure turbine stage 6. The rotors of the compressors 2, 3, turbines 5, 6 and fan S rotate around the central axis X of the turbomachine 100, and can be coupled together by different transmission and gear systems.

[0043] In the remainder of the description, reference is made to the low-pressure turbine 6. It will be noted, however, that the invention can be applied equally well to the low-pressure turbine 6 as to the high pressure turbine 5. This low pressure turbine 6 comprises a plurality of rotor stages and stator stages succeeding one another from upstream to downstream. For the purposes of simplification, only one rotor stage and one stator stage are shown in the remainder of the description.

[0044] In this respect, image 2A of figures 2A-2B schematically represents a section in an axial plane of a sealing ring 30 described below surrounding the rotor, or rotor stage 40, and image 2B schematically represents a section in a radial plane of the ring sector 30 and of the rotor 40 of image 2A according to the section plane BB, making it possible to visualize the junction between two ring sectors.

[0045] Each rotor stage 40 comprises a plurality of mobile rotor blades 42 each comprising a blade, a root mounted on a disk (not shown) coupled to a shaft of the turbomachine. The rotor stage 40 rotates around the central axis X of rotation, inside the sealing ring 30 (hereinafter called "ring 30") of the stator, comprising a plurality of curved ring sectors 32 joined end to end circumferentially, to form the ring 30 enveloping the rotor 40.

[0046] The circumferential ends of each ring sector 32 comprise a slot 34 configured to partially receive a strip, or sealing plate 36 (hereinafter “plate” 36). Each plate 36 is therefore housed in the slots 34 of the circumferentially adjacent ring sectors 32, said slots 34 being circumferentially opposite one another. It is thus understood that a plate 36 is arranged so as to extend circumferentially between each pair of circumferentially adjacent ring sectors 32. In other words, the ring 30 comprises as many plates 36 as there are junctions between the ring sectors 32.

[0047] An abradable track 38 is carried by a radially inner face of each ring sector 32. In this example, the head of a moving blade 42 is equipped with two wipers 44a, 44b configured to cut into the track of abradable material 38 carried by the ring sector 32.

[0048] These wipers 44a, 44b make it possible to improve the sealing of the junction between the moving part, that is to say the rotor 40, and the fixed part including the ring 30, by limiting the bypassing of the blades 42 by non-working air. Similarly, the plates 36, typically made of metal, make it possible to improve the thermal sealing at the junction between two ring sectors 32, by limiting the leaks of non-working air at this location.

[0049] [Fig. 3] represents, in an axial section plane, a portion of a stator stage according to the prior art, in particular a sealing assembly comprising a sealing ring 30 and a distributor 20.

[0050] In [Fig.3], a single ring sector 32 (carrying an abradable track 38) is visible, and only a portion of the distributor 20 is also visible. The distributor 20 and ring 30 are both attached to a fixed outer casing 10, in the manner described below.

[0051] The distributor 20 typically comprises a plurality of fixed vanes 24 (or straighteners) distributed circumferentially around the central axis X, and extending between an inner shroud and an outer shroud. The distributor 20 may be formed in a single piece, or comprise a plurality of sectors 22 assembled end to end circumferentially around the central axis X so as to form the distributor 20.

[0052] Each sector 22 comprises one or more fixed blades 24 extending between an internal platform 28 (not visible in [Fig. 3]) and an external platform 26, the assembly of the internal and external platforms forming the internal shroud and the external shroud. The external platform 26 extends axially between an internal upstream spoiler 261 and an internal downstream spoiler 262.

[0053] Furthermore, the external platform 26 comprises an external upstream spoiler 264 extending upstream and outward from a main surface 263 of the external platform 26, and an external downstream spoiler 265 extending downstream and outward from said main surface 263. The external upstream spoiler 264 is formed so as to hook onto an internal hook 12 disposed on an internal face of the fixed external casing 10, cooperating with an external face of said internal hook 12. The internal hook 12 and the external upstream spoiler 264 are oriented in opposition to each other so as to allow such hooking. A similar hooking system is provided at the downstream end of the external platform 26, via the external downstream spoiler 265.

[0054] Furthermore, each ring sector 32 is also fixed to the internal hook 12, on an internal face thereof, and is also held by the distributor 20. Indeed, the internal upstream spoiler 261 and the external upstream spoiler 264 together form a clamp enclosing a portion of the ring sector 32. Taking this arrangement into account, an annular groove 29 is formed between the internal upstream spoiler 261 and the external upstream spoiler 264, the latter thus delimiting a cavity C open towards the upstream.

[0055] The plates 36 arranged between each circumferentially adjacent ring sector 32 are thus axially opposite this annular groove 29. In the event of disengagement, the plates 36 are therefore likely to escape from the space left by this annular groove 29, in particular into the cavity C.

[0056] A sealing assembly according to the present disclosure is shown in [Fig. 4]. More specifically, [Fig. 4] represents, in an axial sectional plane, a portion of a stator stage according to the invention, in particular a sealing assembly comprising a sealing ring 30 and a distributor 20. Furthermore, [Fig. 5] represents a detailed view of a part V of the turbine portion of [Fig. 4].

[0057] The sealing ring 30 according to the invention is identical to the sealing ring 30 according to the prior art described previously, and will therefore not be described again. Similarly, the characteristics of the distributor 20 according to the invention, identical to those of the distributor 20 according to the prior art described previously, in particular the shape of the external platform 26 and the spoilers 264, 265, will not be described again.

[0058] [Fig. 6] also represents a perspective view of a sector 22 of the distributor 20 according to the invention. In this example, the sector 22 comprises six fixed vanes 24 extending between the internal platform 28 and the external platform 26.

[0059] The distributor 20 of the sealing assembly according to the invention differs from that of the prior art, in that the sector 22 comprises an axial protuberance 25 arranged in the annular groove 29. The axial protuberance 25 extends axially upstream from a bottom 292 of the annular groove 29, and over a width L along the annular groove 29.

[0060] At its upstream end, the axial protuberance 25 comprises an upstream end face 252, which is flat and inscribed in a radial plane R perpendicular to the central axis X, and a recessed upstream face 254 which is arranged recessed relative to the upstream end face 252. In other words, the upstream end face 252 is arranged further upstream along the central axis X than the recessed upstream face 254.

[0061] The shape and dimensions of the axial protuberance 25 are such that, when the elements of the sealing assembly are assembled, a portion of the upstream end face 252 is arranged axially opposite a portion of the ring sector 32 comprising the plate 36 (FIGS. 4 and 5). In other words, the plate 36 extends in a plane P substantially parallel to the central axis X, the plane P being secant to the radial plane R comprising the upstream end face 252, preferably perpendicular to the latter.

[0062] Thus, a portion of the upstream end face 252 is arranged at the same radial position as the portion of the ring sector 32 comprising the plate 36, and is axially separated from a downstream end 322 of said portion of the ring sector 32 by an axial clearance J. In other words, the axial protuberance 25 makes it possible to axially bring the distributor 20 closer to said downstream end 322 of the ring sector 32, at the location where the plate 36 is located. The downstream end 322 is therefore no longer axially separated from the distributor 20 by its distance from the bottom 292 of the annular groove 29, but by the axial clearance J.

[0063] The axial clearance J between the upstream end, more precisely the upstream end face 252 of the axial protuberance 25, and the downstream end 322 of the sealing ring 32, is between 0.07 mm and 1.3 mm, preferably equal to 1 mm, so as to take into account the differential expansions between the different parts.

[0064] Furthermore, the width L of the axial protuberance 25 is greater than the width d (image 2B) of the plate 36 in the circumferential direction. It is understood that the distributor 20 comprises an axial protuberance 25 axially opposite each plate 36, and therefore comprises as many axial protuberances 25 as plates 36.

[0065] Alternatively, the distributor 20 may comprise a single axial protuberance 25 extending over the entire length of the annular groove 29, i.e. over the entire circumference of the distributor 20. Consequently, the upstream end face 252 is axially separated from the downstream end 322 of the ring sectors 32 over the entire circumference of the distributor 20 and of the ring 30.

[0066] It will be noted that the invention is not limited to the upstream end of the external platform 26, but could also be applied to configurations in which the axial protuberance 25 is arranged at the downstream end of the external platform 26, or at the level of the internal platform 28.

[0067] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated / mentioned embodiments may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

Claims

1. Sealing assembly for a turbomachine turbine (6) extending around a central axis (X), the turbine (6) comprising a fixed casing (10) having at least one internal hook (12) which extends radially projecting from the casing (10) towards the central axis (X), the sealing assembly comprising: - a turbine distributor (20) centered on the central axis (X) and comprising at least one fixed vane (24) extending between a radially internal platform (28) and a radially external platform (26), the radially external platform (26) comprising an external upstream spoiler (264) capable of hooking onto the internal hook (12), and an internal upstream spoiler (261) forming with the external upstream spoiler (264) an annular groove (29), the external upstream spoiler (264) being located radially to the outside relative to the internal upstream spoiler (261), - a sealing ring (30) capable of being fixed to the casing (10) and which is intended to surround a rotor stage (40) of the turbine,and comprising a plurality of ring sectors (32) mounted circumferentially end to end around the central axis (X), a first and a second circumferentially adjacent ring sectors (32) respectively comprising a first and a second slot (34), the first and the second slot being arranged circumferentially opposite each other, and a sealing plate (36) comprising a first circumferential end arranged in the first slot and a second circumferential end arranged in the second slot, the distributor (20) comprising an axial protuberance (25) which extends axially projecting from the annular groove (29) so as to reduce an axial distance between the sealing ring (30) and the distributor (20), and being arranged axially opposite the sealing plate (36).,

2. An assembly according to claim 1, wherein the axial protrusion (25) extends axially from a bottom (292) of the annular groove (29) towards the sealing ring (30), the sealing ring (30) being arranged upstream of the axial protrusion (25).

3. An assembly according to claim 1 or 2, wherein the axial protrusion (25) extends circumferentially over a distance (L) greater than a width (d) of the sealing plate (36).

4. An assembly according to any one of claims 1 to 3, wherein the axial protuberance (25) comprises a flat upstream end face (252) of which at least one portion is arranged at the same radial position as the sealing plate (36).

5. An assembly according to claim 4, wherein the axial protrusion (36) comprises a recessed upstream face (254) arranged further downstream than the upstream end face (252).

6. An assembly according to claim 4 or 5, wherein the upstream end face (252) of the axial protuberance (25) is radial with respect to the central axis (X).

7. An assembly according to any one of claims 1 to 6, wherein an axial clearance (J) between an upstream end of the axial protrusion (36) and the sealing ring (30) is less than 2 mm, preferably between 0.07 mm and 1.3 mm.

8. An assembly according to any one of claims 1 to 7, comprising a plurality of axial protrusions (25) distributed circumferentially around the central axis (X), and in which each pair of circumferentially adjacent ring sectors (32) respectively comprises a first and a second slot (34) arranged circumferentially opposite one another and in which is housed a sealing plate (36) comprising a first circumferential end disposed in the first slot (34) and a second circumferential end disposed in the second slot (34), each axial protrusion (25) being disposed axially opposite a sealing plate (36).

9. An assembly according to any one of claims 1 to 7, comprising a single axial protuberance (25) extending axially from a bottom (292) of the annular groove (29) towards the sealing ring (30) over the entire circumference of the distributor (20).

10. A turbine (6) comprising a sealing assembly according to any preceding claim, the turbine (6) being a low pressure turbine.

11. Turbomachine (100) comprising a turbine (6) according to claim 10.

Images