CMC distributor with improved sealing and associated turbomachine turbine

Abstract

CMC distributor with improved sealing and associated turbomachine turbine The invention relates to an annular turbine distributor (2) (1) comprising a plurality of distributor sectors (20) made of ceramic matrix composite material forming a ring, each sector (20) of the ring comprising an inner platform (24) and an outer platform (26) having along the circumferential direction (Dc) respectively a first and a second inner ends (241, 242) and a first and a second outer ends (261, 262), and at least one blade (28) extending radially between the inner and outer platforms (24, 26).For each sector (20), said first inner end (241) comprises a first inner shoulder (243) and said second inner end (242) comprises a second inner shoulder (244) shaped to cooperate by interlocking with the first inner shoulder (243) of an adjacent inner platform (24), and said first outer end (261) comprises a first outer shoulder (263) and said second outer end (262) comprises a second outer shoulder (264) shaped to cooperate by interlocking with the first outer shoulder (263) of an adjacent inner platform (26). Figure for the abstract: Fig. 3.

Description

Title of the invention: CMC distributor with improved sealing and associated turbomachine turbine Technical field

[0001] The invention relates to turbomachines, in particular aeronautical turboshaft engines or industrial turbines comprising a turbine distributor made of a ceramic matrix composite material or a matrix at least partially made of ceramic, hereinafter referred to as CMC material.

[0002] The field of application of the invention is in particular that of gas turbine aeronautical engines. The invention is however applicable to other turbomachines, for example industrial turbines. Prior art

[0003] Improving the performance of turbomachines and reducing their polluting emissions means that increasingly high operating temperatures are required.

[0004] For hot part elements of turbomachines, it was therefore proposed to use ceramic matrix composite materials subsequently referred to as CMC.

[0005] CMC materials are typically formed from a fibrous reinforcement of refractory fibers, such as carbon or ceramic fibers, densified by a ceramic or at least partially ceramic matrix.

[0006] These materials have remarkable thermo-structural properties, that is to say mechanical properties which make them suitable for constituting structural elements and the capacity to retain these properties at high temperatures. In addition, CMC materials have a density much lower than that of the metallic materials traditionally used for elements of hot parts of turbomachines.

[0007] Thus, documents WO 2010 / 061140, WO 2010 / 116066 and WO 2011 / 080443 describe the production of turbine wheel blades made of CMC with integrated platform and heel. The use of CMC materials for turbine distributors has also been proposed, in particular in documents WO 2010 / 146288, FR 2 979 662 and EP 2 443 318.

[0008] A traditional metal turbine nozzle has a crown shape composed of several assembled sectors, each sector comprising an inner platform, an outer platform and a plurality of blades extending between and attached to the inner and outer platforms. The juxtaposed inner platforms form an inner shroud and the juxtaposed outer platforms form an outer shell. The inner and outer shells delimit the gas flow path in the distributor.

[0009] Introducing a distributor, for example a high-pressure distributor, in CMC makes it possible to increase the maximum tolerated temperature compared to a metal distributor, and thus to reduce the quantity of cooling air used. This thus makes it possible to increase the performance of the turbomachine.

[0010] However, CMC, due to its different properties from metal, is more sensitive to certain mechanical stresses. In fact, CMC has greater rigidity and lower expansion. It behaves better in compression, but its admissible tensile stresses are lower than those of metal.

[0011] Furthermore, the integration of a CMC part into a metallic environment is delicate due to the differential thermal expansions between the CMC and the metal. This is all the more delicate in a turbomachine, and more particularly in a high-pressure part of the turbomachine, because the environment is hot, which exacerbates the differences in thermal expansion coefficients between the materials, the aerodynamic forces experienced by a high-pressure distributor being furthermore high in this turbine zone.

[0012] CMC distributors are known, for example a turbine distributor comprising an external support shell secured to a casing, an internal support shell, and a plurality of CMC distributor sectors forming a crown extending between the external support shell and the internal support shell. Each distributor sector bears on the internal and external support shells and comprises an internal platform, an external platform, and at least one blade extending between the external platform and the internal platform and fixed thereto.

[0013] However, there is a need to improve the known solutions with regard to the deterministic maintenance of the distributor sector in CMC with the internal shell, in particular in terms of axial maintenance of the distributor sector and in terms of recovery of aerodynamic forces.

[0014] Furthermore, a significant pressure differential is exerted on the casing radially under the distributor in the radial and axial directions. This casing serves to create a seal between the rotor and the stator. This pressure difference is the source of a force which, if exerted on the CMC, would be high given the permissible loads of the material.

[0015] Also known, in particular from document FR 3 061 928 and FR 2 973 435, is a distributor as described above and further comprising a reinforcing mast extending radially inside the blades between the two platforms allowing the distributor to be held to the casing by the mast.

[0016] However, such a solution takes up via the mast both the forces relating to the pressure differential radially under the distributor and the aerodynamic forces on the CMC crown. In addition, for the reasons mentioned above relating to the different mechanical behavior between CMC and metallic material, it is difficult to position the CMC part on the metallic environment by clamping it.

[0017] During operation of the turbine, a significant radial clearance is generated between the mast and the blade that it passes through. More particularly, since the expansion of the mast is greater than the expansion of the blade in CMC, a radial clearance greater than 0.5 mm, or even greater than 1 mm, may appear between the mast and the blade that it passes through. This radial clearance generates uncertainty in the position of the blade, the aerodynamic plating becoming random upwards or downwards depending on the radial resultant of the aerodynamic force.

[0018] In an all-metal distributor, the distributors are usually cast and several blades make up a single distributor (often doublets or triplets, i.e. two or three blades per ring sector). In this case the passage section is controlled and repeatable by the manufacturing process.

[0019] This is no longer the case when the blades are integrated in CMC material in a metallic environment, for several reasons. On the one hand, due to the lack of control of the tolerances on the CMC parts, due to the fact that the blade in CMC material is not constrained in position to avoid damaging it, and due to the contact between the blade in CMC material and the metallic mast which takes up the forces.

[0020] There is therefore a need to improve the deterministic maintenance of the distributor in CMC of this solution.

[0021] In addition, the use of CMC ring sectors increases the number of parts required for its integration into the turbine casing, which increases the cost and weight of the assembly and requires complex assembly operations (shrinking of bushings, assembly of pins, etc.) which can in particular affect the sealing of the ring.

[0022] Document FR 2 979 573 discloses annular distributors comprising interlocking structures for circumferential blade platforms. However, these interlocking structures can only be used for platforms having simple shapes. In addition, they have bulges, or ribs which disturb the fluid flow in the flow vein. Statement of the invention

[0023] The invention aims to overcome the drawbacks mentioned above and to overcome the difficulties mentioned above by proposing a turbomachine turbine comprising a turbine distributor at least partly made of CMC, the assembly of which is simplified and adapted to maintain its distributor sectors in a deterministic manner while allowing the sectors to deform independently of the interfacing metal parts, and while guaranteeing satisfactory sealing between the ring sectors. particularly at the interfaces between the platform sections, both internal and external, in order to respect the level of reintroduction of vein air admissible in these areas.

[0024] This aim is achieved by means of an annular turbine distributor comprising a plurality of distributor sectors made of ceramic matrix composite material forming a crown defining an axial direction, a radial direction and a circumferential direction, each sector of the crown comprising: - an interior platform having, in the circumferential direction, a first interior end and a second interior end, - an outer platform having, in the circumferential direction, a first outer end and a second outer end, and - at least one blade extending radially between the inner and outer platforms.

[0025] According to a general characteristic of the invention, for each sector, said first inner end comprises a first machining forming a first inner shoulder and said second inner end comprises a second machining forming a second inner shoulder shaped to cooperate by fitting with the first inner shoulder of an inner platform of an adjacent sector, and said first outer end comprises a third machining forming a first outer shoulder and said second outer end comprises a fourth machining forming a second outer shoulder shaped to cooperate by fitting with the first outer shoulder of an inner platform of an adjacent sector.

[0026] This architectural configuration of the platforms of the ring sectors makes it possible to create, at each junction between two adjacent platforms of the crown, a baffle limiting the air flow between the non-vein sector and the gas flow flow vein.

[0027] This architectural solution makes it easy to produce nestable blade structures in the circumferential direction even when the platform has a complex shape.

[0028] The invention thus makes it possible to improve the sealing between the different platforms of the distributor sectors, such as the sectors of a low-pressure distributor, and therefore to control the level of pressurization of the internal cavities as well as the level of reintroduction of air coming from the vein.

[0029] Furthermore, the formation of the shoulders in the platforms of the ring sectors requires simplified machining of the interfaces compared to the machining of a slot for a tab for example.

[0030] Furthermore, the architectural solution can be adapted to any integration of dis distributor which must be sectorized and for which radial sealing between two sectorized parts must be ensured, and for any material from which the distributor is manufactured.

[0031] According to a first embodiment of the distributor, the crown formed by the assembly of the sectors may comprise an inner ferrule formed by the assembly of the inner platforms and an outer ferrule formed by the assembly of the outer platforms, the inner ferrule comprising a continuous radially outer surface, and the outer ferrule comprising a continuous radially inner surface opposite the radially outer surface of the inner ferrule, the ferrules being intended to delimit between them an air flow vein.

[0032] In other words, the platforms are formed in a plate of a certain thickness which is then machined on each of the circumferential ends to produce the shoulders without modifying the radial surfaces of the platforms.

[0033] According to a second embodiment of the distributor, the distributor may further comprise a sealing sheet, which may be annular, arranged radially inside an inner shell formed by the inner platforms of the sectors assembled to form the crown, and a radial spring arranged radially inside the sealing sheet and pressing the sealing sheet against the inner shell.

[0034] The sealing sheet and the radial spring which presses it against the inner ferrule ensure sealing at the level of the fitting of the first and second inner shoulders.

[0035] According to a third embodiment of the dispenser, the inner platform of each sector may have circumferential ends having the shape of broken lines in a plane comprising the circumferential direction and the axial direction.

[0036] In another object of the invention, there is provided a turbomachine turbine comprising a casing, an external metal support shell secured to the casing and defining an axial direction, a radial direction and a circumferential direction, an internal metal support shell, an annular turbine distributor as defined above forming a crown extending between the external support shell and the internal support shell.

[0037] According to a first embodiment of the turbine, said at least one blade of each sector may have a hollow profile defining an internal housing extending radially, and the turbine may further comprise, for each sector, at least one mast secured to the metal shell and radially passing through the sector via the housing of a blade.

[0038] The invention thus proposes a solution for controlling the passage section of the flow of vein in a distributor comprising an assembly of hollow CMC blades crossed by metal masts despite being held in an unconstrained position.

[0039] The configuration thus proposed makes it possible to control the passage section of the hollow blade made of CMC material positioned on a metal mast despite being held in an unconstrained position.

[0040] According to a second embodiment of the turbine, the masts and the external metal shell can be made in a single piece.

[0041] This makes it possible to limit as much as possible the leaks which would be present in the case of a sectored shell or masts attached to the external shell.

[0042] According to a third embodiment of the turbine, the mast can be hollow.

[0043] The mast thus makes it possible to bring air into the cavity radially inside the internal shell in order to pressurize it and thus prevent the air circulating in the vein extending between the internal and external platforms of the distributor sectors from being reintroduced outside this vein and thus reducing the performance and increasing the risk of overheating of the parts.

[0044] The invention also relates to a turbomachine comprising an assembly as defined above.

[0045] The invention also relates to an aircraft comprising at least one turbomachine as defined above. Brief description of the drawings

[0046] [Fig-1] [Fig.l] is a schematic sectional view of a sector of a turbine according to an embodiment of the invention.

[0047] [Fig.2] [Fig.2] represents a schematic perspective view of a single distributor sector of the turbine of [Fig.l].

[0048] [Fig.3] [Fig.3] is a schematic front perspective view of three adjacent sectors of the turbine distributor of [Fig.l].

[0049] [Fig.4] [Fig.4] schematically represents an exploded perspective view of a portion of the turbine sector of [Fig.l].

[0050] [Fig.5] [Fig.5] schematically represents a radial spring of the distributor of [Fig.l]. Description of the embodiments

[0051] In [Fig.l] is illustrated a schematic sectional view of a sector of a turbine according to an embodiment of the invention.

[0052] A turbine 1 of a turbomachine, for example a low or high pressure turbine of an aeronautical turboshaft, as partially shown in [Fig.l], comprises a plurality of fixed distributors 2 which alternate with movable wheels 3 in the direction flow of the gas flow F, indicated by an arrow in [Fig.l], in the turbine 1 and which are mounted in a turbine casing.

[0053] Each movable wheel 3 comprises a plurality of blades 30 having an inner shroud 34, and at least one blade 38 extending from the inner shroud 34 and connected thereto. On the inner side of the inner shroud 34, the blade 30 is extended by a root 37 engaged in a housing of a disc 39. On the outer side, the tip of the blades 30 is opposite an abradable material 32 carried by a ring to ensure sealing at the tips of the blades.

[0054] Throughout this text, the terms "inner" or "internal" and "outer" or "external" are used with reference to the position or orientation relative to the axis of rotation of the turbine 1 which defines the axial direction DA of the turbine 1.

[0055] The blades of the moving wheel may be traditional metal blades or blades made of CMC material obtained for example as described in documents WO 2010 / 061140, WO 2010 / 116066, WO 2011 / 080443.

[0056] At least one of the distributors 2 of the turbine 1 is formed by joining several sectors of annular distributors 20 made of CMC material to form a complete ring. The arrow DA indicates the axial direction of the distributor 2 while the arrow Dr indicates the radial direction of the distributor 2 and the reference Dc indicates the circumferential direction.

[0057] Each distributor sector 20 of the distributor 2 comprises an inner platform 24, an outer platform 26 and a blade 28 extending between the inner and outer platforms 24 and 26 and fixed thereto. Alternatively, several blades could extend between the inner and outer platforms of the same distributor sector. Once assembled with the casing of the turbine 1, the sectors 20 form a single distributor ring 2 having an inner shroud formed by the juxtaposition of the inner platforms 24 of the sectors 20 and an outer shroud formed by the juxtaposition of the outer platforms 26 of the sectors 20.

[0058] The inner shell and the outer shell form between them a fluid flow vein 45 inside which the gas flow F flows during operation of the turbine 1.

[0059] Throughout the text, the terms “upstream” and “downstream” are used with reference to the direction of flow of the gas flow F in the vein 45 indicated by an arrow.

[0060] The inner platforms 24 each have an outer surface 24e intended to be in contact with the gas flow F, and therefore arranged radially opposite the outer platforms 26 forming the outer shell. The inner platforms 24 further have an inner surface 24i arranged opposite the axis of rotation of the turbine 1.

[0061] The outer platforms 26 each have an outer surface 26e arranged facing the casing radially on the outside. The outer platforms 26 further have an inner surface 26i intended to be in contact with the gas flow F, and therefore arranged radially facing the inner platforms 24 forming the inner shell and facing the axis of rotation of the turbine 1.

[0062] The distributor 2 is held between an internal metal ferrule 5 and an external metal ferrule 9 between which extends the crown formed by the assembly of the ring sectors 20 of the distributor 2. The external metal ferrule 9 is integral with the casing and has an internal surface 91 and an external surface 92 in the radial direction DR.

[0063] As illustrated in [Fig.l] as well as in [Fig.2] which presents a schematic perspective view of a distributor sector 20 and in [Fig.3] which presents a schematic front perspective view of three successive sectors 20, the inner platform 24 of each sector 20 has, in the circumferential direction Dc, a first end and a second end opposite the first end, hereinafter referred to as the first inner end 241 and the second inner end 242, and the outer platform 26 of each sector 20 has, in the circumferential direction Dc, a first end and a second end opposite the first end, hereinafter referred to as the first outer end 261 and the second outer end 262.

[0064] The inner platform 24 comprises a first machining carried out in the thickness of the first inner end 241 to form a first inner shoulder 243, the thickness of the inner and outer platforms 24 and 26 being measured in the radial direction DR. The inner platform 24 comprises a second machining carried out in the thickness of the second inner end 242 to form a second inner shoulder 244.

[0065] Similarly, the outer platform 26 comprises a third machining carried out in the thickness of the first outer end 261 to form a first outer shoulder 263 and a fourth machining carried out in the thickness of the second outer end 262 to form a second outer shoulder 264.

[0066] The sectors 20 forming the annular distributor 2 are identical. The first inner shoulder 243 and the second inner shoulder 244 are shaped to cooperate with each other by fitting together, and the first outer shoulder 263 and the second outer shoulder 264 are shaped to cooperate with each other by fitting together. Thus, the first inner shoulder 243 and the first outer shoulder 263 of a first sector 20 fit respectively with the second inner shoulder 244 and the second outer shoulder 264 of a second sector 20 circumferentially adjacent to the first sector 20.

[0067] Furthermore, each blade 28 has a hollow profile having an internal housing 280 extending over the entire height of the blade 28, that is to say between the inner platform 24 and the outer platform 26 of the ring sector 20. The inner platform 24 of each distributor sector 20 comprises an orifice 245 whose shape corresponds to the section of the inner housing 280 in the plane in which the inner platform 24 extends. Similarly, the outer platform 26 of each distributor sector 20 comprises an orifice 265 whose shape corresponds to the section of the inner housing 280 in the plane in which the inner platform 26 extends. The orifices 245 and 265 of the inner 24 and outer 26 platforms are made in the extension of the inner housing 280 of the blade 28.

[0068] The inner housing 280 of the blade 28 and the ports 245 and 265 of the inner 24 and outer 26 platforms may be connected to a cooling system delivering a flow of cooling air from the housing into the blade 28 and the inner 24 and outer 26 platforms.

[0069] Further, as illustrated, the inner platform 24 of each sector 20 has circumferential ends having broken line shapes in a plane comprising the circumferential direction Dc and the axial direction DA.

[0070] As illustrated in [Fig. 1] and in [Fig. 4] which presents a partial schematic exploded perspective view of the turbine 1 of [Fig. 1], the external support shell 9 comprises, for each distributor sector 20, a mast 6 extending in the radial direction DR from the inner surface 91 of the external metal shell 9.

[0071] As illustrated, the mast 6 comprises a rod 62 extending projecting from the head 61 in the radial direction DR inwards and configured to pass through the outer metal ferrule 9, the inner housing 280 of the blade 28 and the orifices 245 and 265 of the inner 24 and outer 26 platforms being aligned with the inner housing 280 of the blade 28.

[0072] In other words, the mast 6 comprises a first radially internal end 6i and a second radially external end 6e, a body 62 extending substantially in the radial direction DR between the first and second ends 6i and 6e of the mast 6.

[0073] The mast 6 is hollow to bring air into the cavity radially inside the inner shell in order to pressurize it and thus prevent the air circulating in the vein extending between the inner and outer platforms of the distributor sectors from being reintroduced outside this vein and thus reducing the performance and increasing the risk of overheating of the parts. The mast 6 thus comprises an internal housing 60 extending in the radial direction DR between the first and second ends 6i and 6e of the mast 6.

[0074] The external metal ferrule 9 comprises an upstream end 94 and a downstream end 95 in the axial direction DA. On its downstream end 95, the external metal ferrule 9 comprises a shoulder 96 extending radially inwards from the inner surface 91 of the outer metal ferrule 9 over the entire circumference of the outer metal ferrule 9, and forming a bearing surface 960 in the axial direction DA, the bearing surface 960 of the outer metal ferrule being oriented in the axial direction DA facing the flow of the stream F, in other words facing the upstream.

[0075] The outer platform 26 comprises an axial stop 260 extending radially outward from the outer surface 26e of the outer platform 26, the axial stop 260 having an axial bearing surface 262 oriented in the axial direction DA in the direction of flow of the stream F, that is to say facing the downstream. The axial bearing surface 262 of the axial stop 260 is thus opposite, and even in contact with, the bearing surface 960 of the shoulder 96 of the external metal ferrule 9.

[0076] Furthermore, the internal support ferrule 5 comprises orifices configured to receive the masts 6. The mast 6 makes it possible to provide a means of fixing the CMC distributor sector 20 from above, i.e. to the casing, while minimizing the bending moment, insofar as the bending length is reduced by approximately half by the mast 6 passing through the distributor sector. Each distributor sector 20 is thus maintained deterministically, i.e. in such a way as to prevent the distributor sector 20 from starting to vibrate and by controlling its position, and this while allowing the distributor sector 20 to deform under the effects of temperature and pressure, among other things, independently of the interfacing metal parts.

[0077] Furthermore, as illustrated in Figures 1 and 4, the distributor 2 comprises an annular sealing sheet 7 and an annular radial spring 8 which is notably illustrated schematically in perspective in [Fig.5].

[0078] The sealing sheet 7 is produced in the form of a regularly perforated ring to be passed through by the masts 6. It is arranged radially between the internal platforms 24 and the radial spring 8, the radial spring 8 being radially inside the sealing sheet 7.

[0079] The radial spring 8 comprises a main annular portion 80 having a C shape in a section plane comprising the radial direction DR and the axial direction DA and spring elements 82 each having an S shape, two spring elements 82 framing, in the circumferential direction Dc, each blade 28.

[0080] In the case where each distributor sector comprises several blades, the turbine comprises, at most, a corresponding number of masts for each distributor sector.

[0081] The turbomachine turbine according to the invention comprises a turbine distributor at least partly made of CMC, the assembly of which is simplified and adapted to maintain its distributor sectors in a deterministic manner while allowing the sectors to deform independently of the interfacing metal parts, and improving the seal between the mast and the external metal ferrule.

Claims

Claims

1. Annular distributor (2) of turbine (1) comprising a plurality of distributor sectors (20) made of ceramic matrix composite material forming a crown defining an axial direction (DA), a radial direction (DR) and a circumferential direction (Dc), each sector (20) of the crown comprising: - an inner platform (24) having, in the circumferential direction (Dc), a first inner end (241) and a second inner end (242), - an external platform (26) having, in the circumferential direction (Dc), a first external end (261) and a second external end (262), and - at least one blade (28) extending radially between the inner and outer platforms (24, 26), characterized in that, for each sector (20), said first inner end (241) comprises a first machining forming a first inner shoulder (243) and said second inner end (242) comprises a second machining forming a second inner shoulder (244) shaped to cooperate by fitting with the first inner shoulder (243) of an inner platform (24) of a circumferentially adjacent sector (20), and said first outer end (261) comprises a third machining forming a first outer shoulder (263) and said second outer end (262) comprises a fourth machining forming a second outer shoulder (264) shaped to cooperate by fitting with the first outer shoulder (263) of an inner platform (26) of a circumferentially adjacent sector (20) the distributor (2) further comprising a sealing sheet (7) arranged radially inside an inner shell formed by the inner platforms (24) of the sectors (20) assembled to form the crown, and a radial spring (8) arranged radially inside the sealing sheet (7) and pressing the sealing sheet (7) against the inner shell.

2. Dispenser (2) according to claim 1, in which the crown formed by the assembly of the sectors (20) comprises an inner ferrule formed by the assembly of the inner platforms (24) and an outer ferrule formed by the assembly of the outer platforms (26), the inner shell having a continuous radially external surface, and the outer shell having a radially internal surface opposite the radially external surface of the inner shell, the shells being intended to delimit between them an air flow vein.

3. Dispenser (2) according to one of claims 1 or 2, in which the inner platform (24) of each sector (20) has circumferential ends having broken line shapes in a plane comprising the circumferential direction (Dc) and the axial direction (DA).

4. A turbomachine turbine (1) comprising a casing, an external metal support shroud (9) secured to the casing and defining an axial direction (DA), a radial direction (DR) and a circumferential direction (Dc), an internal metal support shroud (5), an annular turbine distributor (2) according to one of claims 1 to 3 forming a crown extending between the external support shroud (9) and the internal support shroud (5).

5. Turbine (1) according to claim 4, wherein said at least one blade (28) of each sector (20) has a hollow profile defining an internal housing (280) extending radially, and the turbine (1) further comprising, for each sector (20), at least one mast (6) secured to the metal shell (9) and radially passing through the sector (20) via the housing (280) of a blade (28).

6. Turbine (1) according to claim 5, in which the masts (6) and the external metal shell (9) are made in a single piece.

7. Turbine (1) according to any one of claims 5 or 6, in which the mast (6) is hollow.

8. Turbomachine comprising a turbine (1) according to one of claims 4 to 7.

9. Aircraft comprising at least one turbomachine according to claim 8.

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