Turbine distributor sector equipped with a honeycomb structure

Abstract

The turbine distributor sector (12) comprising:- at least one blade (23),- a platform (26), and- a foot (34) fixed to the platform, the foot having two faces (36, 38) oriented respectively upstream and downstream with reference to a flow of fluid passing through the blade during use of the distributor, at least one of the faces having a groove (46) opening onto a circumferential face (44) of the foot. Abstract figure: Fig. 3

Description

Title of the invention: Turbine distributor sector equipped with a honeycomb structure FIELD OF THE INVENTION

[0001] The invention relates to turbomachines, in particular their distributors. STATE OF THE ART

[0002] For example, document FR-3 082 233 discloses an aircraft turbojet engine comprising, from upstream to downstream with reference to the air flow passing through the engine, a fan, a compressor, a combustion chamber and a turbine. The turbine recovers part of the energy from the combustion of the gases for the operation of the fan, the compressor and the accessories.

[0003] One of the parts of the turbine is the stator which includes fixed distributors interposed between its rotating discs. The discs and distributors include blades traversed by the air from the main air stream of the engine.

[0004] The distributors comprise internal platforms fixed to the blades. The discs are connected to each other by junctions passing under the internal platforms of the distributors.

[0005] In operation, turbulent air flows from the main vein circulate in the cavities delimited by the junctions around the platforms. These flows cause a loss of efficiency. Indeed, during operation, the energy source comes from the work of the hot air through the turbine. All the areas where this air is not working to move the aircraft forward is a loss of efficiency. We therefore seek to reduce the areas of dry loss where the air is not working. This turbulence also generates acoustic problems.

[0006] To remedy this, it is known to provide spoilers on the blades projecting in the axial direction towards the adjacent distributors. Similarly, radial wipers integral with the discs come into contact with the foot of the distributor platform. In both cases, this is to limit the passage of air coming from the main stream.

[0007] It has also already been planned to provide the base of the platform with an "L" or "T" shape to limit air circulation. This technology is interesting insofar as it does not complicate the assembly of the turbine parts. But it has a significant impact in terms of weight. Indeed, the platform is a casting and the "L" or "T" further increases the weight.

[0008] An aim of the invention is therefore to improve the performance of the turbine by avoiding having zones in which the air does not provide useful work. Statement of the invention

[0009] For this purpose, according to the invention, a turbine distributor sector is provided comprising: - at least one blade, - a platform, and - a foot fixed to the platform, the foot having two faces oriented respectively upstream and downstream with reference to a flow of fluid passing through the blade when using the distributor, at least one of the faces having a groove opening onto a circumferential face of the foot.

[0010] Optionally, the faces each have a groove, the grooves extending towards one another, each of the grooves opening onto two circumferential faces of the foot.

[0011] The grooves receive the spoilers of the adjacent moving blades by matching their shape. This forms labyrinths on each side of the root which limit the circulation of air. The reduction of air leaks therefore improves the performance of the turbine and the turbomachine.

[0012] This configuration of the foot increases its volume. By giving a large volume to the foot, the invention therefore makes it possible to reduce the space available for the leakage air, which improves the continuity of the main air stream during all phases of the mission.

[0013] As the foot is made of a honeycomb structure, its weight is particularly low. The limitation of air circulation is therefore achieved by means of a large but not very massive part. The invention makes it possible to reduce the mass of the distributors, improves the performance level of the turbine and therefore also makes it possible to reduce fuel consumption.

[0014] The invention results in a drastic reduction in the mass of the turbine in certain embodiments. For example, on the LEAP® engine developed and marketed by Safran Aircraft Engines and GE within CFM International, the weight saving is 9 kg per engine. For the second low-pressure distributor of this engine, the saving per distributor angular sector is estimated at approximately 70 grams, or 1.8 kg per complete stage.

[0015] The foot may be made of a honeycomb structure.

[0016] The honeycomb feet are low-cost and easily replaceable parts so that repair of the turbomachine is, if necessary, easy to carry out. In addition, these feet are easily abradable in contact with the wipers secured to the rotating discs.

[0017] The invention also makes it possible to avoid producing the aforementioned “L” or “T” in a foundry. It makes it possible to reduce the total volume of the part of the distributor manufactured in a foundry and which notably includes the blade and the platform. Indeed, the volume and mass of the latter are reduced in comparison with current solutions. This allows a reduction in the consumption of raw material and the cost of the molds. Since the typology of the distributor is simplified, the invention also makes it possible to reduce the risks of non-conformity during manufacturing. It can also be implemented with a reduced number of parts and does not require the addition of an additional part compared with current solutions.

[0018] Advantageously, the foot extends projecting from an upstream edge of the platform and / or from a downstream edge of the platform.

[0019] In one embodiment, the foot is in one piece.

[0020] It can be provided that the foot forms a free end of the sector.

[0021] In one embodiment, the sector comprises at least one rib extending from one side of the platform facing the foot, for example at least two ribs.

[0022] This rib allows the rigidity of the platform to be preserved despite the reduction in its mass and volume. The rib also forms a weight constituting a reserve of material during cooling of the blade after manufacturing by casting.

[0023] It can be provided that the or each rib has an axis having an inclination relative to a chord of the blade of between 0 and 20°.

[0024] According to the invention, there is also provided a turbomachine comprising: - a casing, - a rotor comprising at least one rotating disk comprising blades having at least one spoiler extending in a direction radial to an axis of the turbomachine, and - at least one distributor, in particular low pressure, rigidly secured to the casing, the distributor comprising: - blades, - a platform, and - a foot fixed to the platform which may be made of a honeycomb structure and having at least one groove receiving at least one spoiler of the blades.

[0025] Optionally, the turbomachine comprises at least two rotating discs each comprising blades having spoilers, the distributor being interposed between the rotating discs and the foot comprising two grooves receiving the spoilers of the respective blades.

[0026] In one embodiment, the turbomachine comprises wipers rigidly secured to the rotating disks, the foot extending opposite the wipers, the wipers being interposed between the foot and the axis of the turbomachine.

[0027] It can be provided that the distributor is a low pressure turbine distributor, the turbomachine further comprising at least one high pressure turbine distributor. DESCRIPTION OF THE FIGURES

[0028] We will now present an embodiment of the invention by way of non-limiting example with the support of the drawings in which:

[0029] [Fig. 1] [Fig. 1] is a partial half-sectional view of an aircraft turbojet engine forming an embodiment of the invention;

[0030] [Fig.2] [Fig.2] is a larger scale view of detail D of [Fig.l];

[0031] [Fig.3] [Fig.3] is a larger scale view of one of the sectors of the figure previous;

[0032] [Fig.4]

[0033] [Fig.5]

[0034] Figures 4 and 5 are bottom views of one of the distributor sectors of the preceding figures, with and without the ribs;

[0035] [Fig.6] [Fig.6] is a sectional view along plane AA of the sector of [Fig.5]; and

[0036] [Fig.7] [Fig.7] illustrates the inclination of the axis of the ribs.

[0037] We will describe with reference to the figures an embodiment of the invention. In this case, it is an aircraft turbojet 1 forming a double-flow, double-spool turbomachine. The turbomachine has a main axis XX which serves as the axis of rotation of the rotor relative to the stator.

[0038] It comprises from upstream to downstream, therefore from left to right in [Fig.l], a fan, a low pressure compressor, a high pressure compressor, a combustion chamber (these elements being not illustrated and otherwise conventional), a high pressure turbine 10 and a low pressure turbine 12. These elements, with the exception of the fan, form a central part of the turbojet. Their mobile parts rotating around the axis XX form the rotor, rotatably mounted in a casing 6 of the machine.

[0039] The high pressure compressor, the combustion chamber and the high pressure turbine 10 form a high pressure body which together with the low pressure compressor and the low pressure turbine 12 defines a main air flow vein 11. A nacelle (not shown) surrounds the fan 2 and the central part so as to form a fan compartment and to define a secondary air flow vein.

[0040] We will now focus on the low pressure turbine 12. This comprises rotating discs 14 forming part of the rotor and fixed distributors 16 forming part of the stator and rigidly secured to the casing 6.

[0041] The discs 14 are here four in number, this number not being limiting and being able to vary for example between 1 and 10. They each have an annular shape and comprise blades 18 each elongated in a direction radial to the axis XX. With reference to [Fig. 2], each blade 18 comprises an external or upper platform 20 and an internal or lower platform 22. The external platform 20 extends at the radial end of the blade 18 furthest from the axis XX and the internal platform 22 at its end closest to the axis. The blades 18 extend in the main air flow vein 11 and are movable in rotation about the axis XX.

[0042] The distributors 16 have a similar arrangement. They are also four in number here, this number not being limiting and being able to vary for example between 1 and 10. They each have an annular shape and comprise blades 23 each elongated in a direction radial to the axis XX. Each blade 23 comprises an external or upper platform 24 and an internal or lower platform 26. The external platform 24 extends at the radial end of the blade furthest from the axis and the internal platform 26 at its end closest to the axis. The blades extend in the main air flow vein 11.

[0043] The blades 23 of the distributors 16 are arranged alternately with the vanes 18 of the rotating discs 14 along the axis XX so that each of the three most downstream distributors, with reference to the flow of air in the vein, is interposed between two of the rotating discs 14.

[0044] The rotating discs 14 are rotatably mounted around the axis XX and are rigidly secured to each other. The distributors 16 are fixed and rigidly secured to the casing.

[0045] With reference to [Fig. 3], the lower platform 26 of each blade 18 comprises upstream 28 and downstream 30 spoilers extending in the radial direction towards the respective distributors adjacent to the blade 18. The spoilers 28, 30 have a cylindrical or frustoconical shape having the axis XX as their axis.

[0046] The distributors 16 are each divided into sectors 32 arranged in succession along the circumferential direction to the axis XX. Each sector 32 carries one or more of the blades 23, at least 2 blades and without limitation in number, fixed to the external 24 and internal 26 platforms which are common to the blades 23 of the sector. Such a sector is illustrated in Figures 4 and 5.

[0047] As illustrated in particular in the figures, each sector 32 comprises a foot 34 fixed to the internal platform 26, in this case by means of a brazing. The foot is made up of a honeycomb structure.

[0048] It is for example made from an alloy resistant to corrosion at high temperature and under severe mechanical stress, containing mainly nickel, such as the alloy marketed under the reference Hastelloy X by the Haynes group (the Hastelloy brand being registered). This alloy comprises 47.5% nickel, 22% chromium and 18.5% iron as well as cobalt, molybdenum and tungsten. Other materials are possible for making the foot.

[0049] In the present example, the foot 34 has a general shape of a volume with six faces, namely an upstream face 36, a downstream face 38, an external face 40 oriented in the direction opposite to the axis XX, an internal face 42 oriented in the direction of the axis and two circumferential end faces 44, all generally planar.

[0050] The two axial faces 36 and 38 are opposite each other and have two respective annular grooves 46 extending towards each other, that is to say towards a median zone of the foot. Each of the grooves opens onto the two circumferential faces 44.

[0051] The foot 34 is fixed to the internal platform 26 by its external face. The internal face of the platform 26 carries for this purpose ribs 48, in the same number as the blades 23 and arranged in line with the latter. The ribs 48 extend on one side of the internal platform 26 facing the foot 34. [Fig. 4] illustrates the lower face of the internal platform 26, the blades 23 being illustrated by transparency. The ribs 48 reinforce the rigidity of the internal platform and act as a weight during the cooling of the blades 23 at the end of the casting step for the manufacture of the blades 23 and the platforms 26 in a single piece.

[0052] Their height h in a radial direction perpendicular to the face of the internal platform 26 is for example 5 mm, as illustrated in [Fig.6]. Their width 1 in the circumferential direction to the axis XX is for example between 90 and 110% of the thickness e of the base of the blades 23.

[0053] The ribs 48 are in coincidence with the respective blades 23 of the sector 32, as shown in FIGS. 4 to 6. The ribs 48 have an elongated shape. Each rib 48 has a longitudinal axis 51 having an inclination relative to a pitch angle of the blade 23 or a chord 53 taken at the root of the blade of between 0 and 20°, as illustrated in [Fig. 7]. These two directions are themselves inclined relative to the axis XX.

[0054] The foot 34 is fixed by brazing to the ribs 48. For example, for this purpose, a brazing powder can be interposed between the foot 34 and the internal platform 26 and carried out appropriate cooking of the powder to make the solder ensuring the attachment of the foot to the platform.

[0055] The powder may consist of a composite powder for diffusion brazing assembly of turbojet blades made of superalloys, formed by mixing a powder of a base metal of the Astroloy or NK17CDAT type and a powder of a diffusion brazing metal comprising boron, or nickel, chromium and boron, or boron and silicon. For example, the powder comprises 75% by weight of Astroloy powder and 25% by weight of NiCrB1055 powder. Astroloy (NK17CDAT) is a nickel-based superalloy which comprises, by weight, 16.9% of cobalt, 14.8% of chromium, 3.87% of aluminum, 3.45% of titanium, 5.1% of molybdenum, 0.015% of carbon. NiCrB105 is also a nickel-based superalloy, which contains, by weight, 15% chromium and 4% boron.

[0056] The foot 34 extends projecting from an upstream edge 50 and a downstream edge 52 of the internal platform 26. Here it is in one piece and forms a free internal end of the sector.

[0057] As illustrated in Figures 2 and 3, the two grooves 46 receive the spoilers 28 and 30 of the respective adjacent blades 18.

[0058] The machine comprises wipers 54 integral in rotation with the rotating discs 14. The internal face 42 of the foot extends opposite the wipers. The foot is formed so as to be abraded by the wipers in order to limit as much as possible the passage of air under the foot 34.

[0059] The foot 34 does not come into contact with the spoilers 28, 30. Furthermore, it is only in contact with the rotating discs at the level of the lips. It is also observed that the foot 34 does not encroach on the main vein 11.

[0060] As can be seen, the foot 34 occupies a large part of the volume available under the internal platform 26 between the two adjacent blades 18, for example more than 30%, or even 50% of this volume. Its shape and dimensions are defined according to the operating clearances of the turbine. For example, minimum clearances of 5 to 15% can be provided to ensure the proper operation of the turbine.

[0061] Numerous modifications may be made to the invention without departing from its scope.

[0062] The invention is applicable to any stator part capable of receiving a honeycomb foot on an internal platform. It is applicable to turbomachines other than turbojets. It applies to single-flow turbojets.

Claims

Claims

1. Sector (32) of distributor (16) of turbine (12) comprising: - at least one blade (23), - a platform (26), and - a foot (34) fixed to the platform (26) by means of a brazing, the foot having two faces (36, 38) oriented respectively upstream and downstream with reference to a flow of fluid passing through the blade during use of the distributor (16), at least one of the faces (36, 38) having a groove (46) opening onto a circumferential face (44) of the foot.

2. Sector according to the preceding claim, in which the faces each have a groove, the grooves extending towards one another, each of the grooves opening onto two circumferential faces (44) of the foot.

3. Sector according to one of the preceding claims, in which the foot consists of a honeycomb structure.

4. Sector according to one of the preceding claims, in which the foot (34) extends projecting from an upstream edge (50) of the platform (26) and / or from a downstream edge (52) of the platform.

5. Sector according to any one of the preceding claims in which the foot (34) is in one piece.

6. Sector according to any one of the preceding claims in which the foot (34) forms a free end of the sector (32).

7. Sector according to any one of the preceding claims which comprises at least one rib (48) extending from one side of the platform (26) facing the foot (34), for example at least two ribs (48).

8. Sector according to the preceding claim in which the or each rib (48) has an axis having an inclination relative to a chord of the blade (23) of between 0 and 20°.

9. Turbomachine (1) comprising: - a casing (6), - a rotor comprising at least one rotating disc (14) comprising blades (18) having at least one spoiler (28, 30) extending in an axial direction to an axis (XX) of the turbomachine, and - at least one distributor (16) rigidly secured to the casing, the distributor comprising: - blades (23), - a platform (26), and - a foot (34) fixed to the platform by means of a brazing, the foot being able to consist of a honeycomb structure and having at least one groove (46) receiving the at least one spoiler of the blades (18).

10. Turbomachine according to the preceding claim, comprising at least two rotating discs (14) each comprising blades (18) having spoilers (28, 30), the distributor being interposed between the rotating discs (14) and the foot (34) comprising two grooves (46) receiving the spoilers of the respective blades (18).

11. Turbomachine according to one of claims 9 or 10 which comprises wipers (54) rigidly secured to the rotating discs (14), the foot (34) extending opposite the wipers, the wipers being interposed between the foot and the axis of the turbomachine.

12. Turbomachine according to one of claims 9 to 11 in which the distributor is a low pressure distributor.

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