EP3004554B1 - Rotor disk blade for turbomachine, turbomachine rotor disk, turbomachine and method of assembly of plates onto a blade foot - Google Patents

Description

Background of the invention

The present invention relates to the general field of turbomachine blades made of composite material comprising a fibrous reinforcement densified by a matrix, and more particularly to a blade of a rotor disc for a turbomachine, to a rotor disc, of a turbomachine, to a turbomachine, as well as a method for assembling plates on a blade root.

The targeted field is that of moving blades intended to be mounted on gas turbine rotor discs for aeronautical engines or industrial turbines.

This type of dawn is originally from foundry and has a bulbous foot. The raw foot is precision machined to provide an efficient mechanical interface with its housing in the rotor disc.

The production of similar vanes in composite material for turbomachines has already been proposed. For example, reference may be made to the patent application US 2011/311368 which describes the manufacture of a turbomachine blade by producing a fibrous preform by three-dimensional or multilayer weaving and densification of the preform by a matrix. The blade root in composite material takes up the geometry of the bulb in order to ensure the absorption of the centrifugal force and to facilitate the integration of the blades in composite material in the existing engine environment.

In the case of blades made of composite material, the blade root is made using an insert positioned in a detachment of the textile preform in order to form a bulb-shaped portion at the level of the part of the blade corresponding to its root. .

However, this blade root formation technique complicates the industrial manufacture of the blade and increases its manufacturing cost because it generates significant material losses and requires delicate manipulations which slow down the production speed. In addition, the insert, also made of composite material, must be densified and machined, which leads to additional cost and possibly rejection of parts.

The textile of the preform, mobile by nature, interacts mechanically with the insert and can lead in particular to shearing of the textile, rotations of the insert, unbinding between the insert and the textile, etc.

Furthermore, the molding and densification of the part of the preform intended to form the blade root prove to be difficult, in particular because the tolerances on the profile of the bulbous root are very low (of the order of tenth of a millimetre) and that the requirements in terms of mechanical properties of this part of the blade are high, the root of the blade concentrating the majority of the forces applied to the blade.

The document US 2010/189562 discloses a composite material turbomachine blade having at its part intended to form the blade root a substantially planar portion, the geometry of the root being obtained by enclosing this portion between two metal plates held in place by a welded pin. This design facilitates the manufacture of the composite blade because the geometry of the bulbous root or equivalent which is difficult to obtain from the textile preform is ensured by adding metal plates to the sides of a flat portion which is simple to make in composite material.

However, as indicated above, the blade root corresponds to the part of the blade which concentrates most of the forces applied to the blade since it is intended to ensure the maintenance of the blade in the vis- against centrifugal forces. In the case of the maintenance of the metal plates by a welded pin as described in the document US 2010/189562 , the forces applied by the centrifugal forces are essentially taken up at the level of the portion made of composite material of the blade in contact with the pin when the friction forces between the metal plates and the sides of the blade made of composite material are insufficient to resume these efforts. In this situation, there is then a risk of damage to the composite material, or even of rupture by caulking of the latter.

Subject matter and summary of the invention

The main purpose of the present invention is therefore to propose a blade made of composite material, the geometry of the root of which can be made in an easy and reproducible manner while ensuring reliable absorption of the forces applied to the blade root.

This object is achieved by virtue of a rotor disk blade for a turbomachine made of composite material comprising a fibrous reinforcement obtained by multilayer weaving of yarns and densified by a matrix, the blade comprising a part constituting the blade and blade root forming a single part, the blade root having two substantially plane opposite lateral flanks which are formed in the respective extension of the intrados and extrados surfaces of the blade, the blade root being sandwiched between two metal plates fixed against the lateral flanks of the blade root blade by a screw and a nut passing through the plates and the blade root, such that the screw comprises a head resting on one of the two plates and in that the nut comprises a head resting on the other plate, the screw and the nut applying on the metal plates a minimum clamping force capable of ensuring an absorption, by friction between the metal plates and the lateral flanks of the blade root, of a determined centrifugal force applied to dawn,
and noteworthy in that each metal plate has on its face opposite to that in contact with the blade root at least one projecting portion, said portion having a shape capable of performing one or both of the following functions: anti-tipping and sealing .

By ensuring, by tightening the plates, a non-slip contact between them and the sides of the blade root, the absorption of the centrifugal force (tensile forces) at the level of the blade root is distributed over the entire surface. of contact between the plates and the sides of the composite foot. This avoids the concentration of stresses at the level of the contact zone between the member for fixing the plates and the corresponding portion of the root made of composite material, which can lead to damage to the root of the blade. By this non-slippery contact, the sensitivity to the lack of compensation of the centrifugal moment by the aerodynamic moment of the blade of the blade is also reduced, which can cause the root of the blade to tilt in the cell of the disc in which it is housed.

According to a first aspect of the blade of the invention, the screw and the nut comprise a head of conical shape while the plates have a corresponding chamfer allowing the screw and nut to be fully integrated into the plates.

According to a second aspect of the blade of the invention, the blade root comprises an oblong hole or scalloping extending in the direction of the length of the blade for the passage of the screw and the nut. The oblong hole or scalloping allowing the release of thermodynamic constraints.

According to a third aspect of the blade of the invention, the face of each plate facing the blade root has a structured surface so as to increase the friction between the plates and the blade root. The face of each plate facing the blade root may in particular comprise straight or crossed knurling oriented according to the direction of the centrifugal forces to which the blade is subjected.

According to a fourth aspect of the blade of the invention, the metal plates have a coefficient of thermal expansion lower than the coefficient of thermal expansion of the screw and of the nut. The clamping force is thus maintained during temperature rises.

According to a fifth aspect of the blade of the invention, the metal plates, the screw and the nut have coefficients of thermal expansion changing in a similar manner over all or part of a temperature range between 0° C. and 800 °C, which allows better control of the maintenance of the tightening over the entire temperature range.

The invention also relates to a turbomachine rotor disk comprising at its outer periphery a plurality of substantially axial metal cells and a plurality of blades as defined previously, each blade being mounted by its root in a cell of the disk. The invention also relates to a turbomachine comprising at least one such rotor disk.

The invention also relates to a method for assembling plates on a blade root, said blade being made of a composite material comprising a fibrous reinforcement obtained by multilayer weaving of wires and densified by a matrix, the blade comprising a part constituting the blade and blade root forming a single piece, the blade root having two substantially planar opposite lateral flanks which are formed in the respective extension of the lower surfaces and upper surface of the blade, the blade root being clamped between two metal plates fixed against the side flanks of the blade root by a screw and a nut passing through the plates and the blade root, such that the screw comprises a head resting on one of the two plates, the nut comprising a head resting on the other plate, and in that a minimum clamping force capable of ensure recovery, by friction between the metal plates and the lateral sides of the blade root, of a determined centrifugal force applied to the blade,
and noteworthy in that each metal plate has on its face opposite to that in contact with the blade root at least one projecting portion, said portion having a shape capable of performing one or both of the following functions: anti-tipping and sealing .

As explained above, by fixing the metal plates on the blade root according to a non-slippery contact by a minimal clamping force, the absorption of the centrifugal force (tensile forces) at the level of the blade root is distributed over the entire contact surface between the plates and the sidewalls of the composite foot. This avoids the concentration of stresses at the level of the contact zone between the member for fixing the plates and the corresponding portion of the root made of composite material, which can lead to damage to the root of the blade. By this non-slippery contact, the sensitivity to the lack of compensation of the centrifugal moment by the aerodynamic moment of the blade of the blade is also reduced, which can cause the root of the blade to tilt in the cell of the disc in which it is housed.

According to one aspect of the method of the invention, the minimum clamping force is determined by dividing the centrifugal force determined by the coefficient of friction between the metal plates and the lateral flanks of the blade root.

Brief description of the drawings

• la figure 1 est une vue en perspective montrant une aube de turbomachine selon un mode de réalisation de l'invention ;
• les figures 2 et 3 est une vue en perspective montrant le montage de plaques sur le pied d'aube de la figure 1 selon un mode de réalisation de l'invention ;
• la figure 4 est une vue en perspective montrant le pied d'aube des figures 2 et 3 une fois monté ;
• la figure 5 est une vue en perspective montrant un pied d'aube comportant un trou oblong selon un autre mode de réalisation de l'invention ;
• la figure 6 est une vue partielle en perspective montrant le montage du pied d'une aube de la figure 4 sur un disque de rotor ;
• la figure 7 est une vue partielle en perspective du disque de rotor de la figure 6 muni d'aubes de la figure 4.

Other characteristics and advantages of the present invention will become apparent from the description given below, with reference to the appended drawings which illustrate examples of embodiments which are devoid of any limiting character. In the figures:

• the figure 1 is a perspective view showing a turbine engine blade according to one embodiment of the invention;
• them figures 2 and 3 is a perspective view showing the mounting of plates on the blade root of the figure 1 according to one embodiment of the invention;
• the figure 4 is a perspective view showing the blade foot of the figures 2 and 3 once mounted;
• the figure 5 is a perspective view showing a blade root comprising an oblong hole according to another embodiment of the invention;
• the figure 6 is a partial perspective view showing the assembly of the foot of a blade of the figure 4 on a rotor disk;
• the figure 7 is a partial perspective view of the rotor disk of the figure 6 fitted with blades of the figure 4 .

Detailed Description of Embodiments

The invention is applicable to different types of moving blades made of composite turbomachine material, in particular compressor and turbine blades of different gas turbine bodies, for example a low-pressure turbine rotor disk blade, such as the one illustrated by figure 1 .

In a manner known per se, the dawn 10 of the figure 1 comprises a blade 12, a foot 14 formed by a part of greater thickness and extended by a stilt 16, and a platform 18 located between the stilt 16 and the blade 12. The dawn can also comprise, as illustrated here, a heel 19 in the vicinity of the free end 20 of the blade.

The blade 12 forms an aerodynamic surface which extends in the longitudinal direction from the platform 18 to its free end 20. It has a curved profile of variable thickness formed by an intrados surface 12a and an extrados surface 12b connected transversely by a leading edge 12c and a trailing edge 12d.

The blade 10 is made of a composite material using methods known to those skilled in the art. By “composite material”, we mean here any material formed from a fibrous reinforcement filled with a matrix such as for example ceramic matrix materials (CMC) (reinforcement made of carbon fibers or ceramic filled with a matrix with less partially ceramic), carbon/carbon (C/C) materials (carbon fiber reinforcement and carbon matrix), oxide/oxide materials (oxide fiber reinforcement and oxide matrix), organic matrix materials (CMO) (fiberglass, carbon or other reinforcement and organic matrix), etc. For example, reference may be made to the patent application US 2011/311368 which describes the manufacture of such a blade comprising a fibrous reinforcement obtained by three-dimensional weaving of yarns and densified by a matrix. With such a method, the constituent part of the blade 12 forms a single piece with the root 14 of the blade. In the example described here, the blade is made of ceramic matrix composite material (CMC).

Due to its particular manufacturing process, the blade 10 also has, at its root 14, two opposite lateral flanks 22, 24 which are substantially plane and which are formed in the respective extension of the intrados 12a and extrados 12b surfaces of blade 12.

According to the invention and as shown in the figures 2 to 4 , the root 14 of the blade 10 is sandwiched between two metal plates 26, 28 fixed respectively against the side flanks 22, 24 of the root.

The fixing of the metal plates 26 and 28 is carried out by means of at least one screw 30 and a nut 40 passing through, in a direction substantially perpendicular to the lateral sides, holes 260 and 280 provided respectively in the plates 26 and 28 and a orifice 25 made through the root 14 of the blade. Nut 40 is preferably a self-locking nut. The orifice 25 in the root of the blade is added during the manufacturing process of the blade, either by using an insert of corresponding shape during weaving, or by drilling the root after the first infiltration. In the embodiment described here, the screw 30 comprises a head 31 of frustoconical shape cooperating with a chamfer 261 provided in the plate 26 while the nut 40 comprises a head 41 also of frustoconical shape cooperating with a chamfer 281 provided in the plate 28. In this way, the screw head and the nut head do not protrude from the external surface of the plates 26 and 28 and allow the insertion of the root of the blade in small-sized housings. The screw 30 comprises a threaded rod 32 cooperating with an internal thread 43 formed inside a hollow rod 42 of the nut 40 during tightening of the connection for fixing the plates. The nut 40 comprises at level with its head 41 a flat 410 intended to cooperate with a flat 282 provided in the chamfer 281 of the plate 28 in order to counter the rotation of the nut 40 during its tightening with the screw 30.

In accordance with the invention, the tightening of the screw 30 with the nut 40 is carried out according to a minimum tightening force capable of ensuring recovery by friction between the metal plates 26 and 28 and the lateral flanks 22 and 24 of the foot of blade of a determined centrifugal force or tensile force applied to the blade. Indeed, the minimum tightening force must make it possible to ensure non-slip contact between, on the one hand, the internal face 26a of the metal plate 26 and the flank 22 of the blade root 14 and, on the other hand , the internal face 28a of the metal plate 28 and the flank 24 of the blade root 14. The contact between the metal plates and the flanks of the blade root must remain non-slip in the face of the maximum tensile force encountered in operation which corresponds to the maximum centrifugal force exerted on the blade during its use. The minimum clamping force to be applied to the plates is calculated from the following formula: $$\begin{array}{c}\mathrm{Effort}\mathrm{of}\mathrm{Tightening}=\mathrm{strength}\mathrm{centrifugal}\mathrm{applied}\mathrm{to}\mathrm{I}\prime \mathrm{dawn}/\mathrm{coefficient}\mathrm{of}\\ \mathrm{friction}\end{array}$$

The tightening of the screw is for example carried out with a dynamometric wrench which makes it possible to control the tightening force applied.

The inner faces 26a and 28a of the metal plates 26 and 28 respectively opposite the sides 22 and 24 of the blade root 14 may comprise a structured surface in order to achieve mechanical anchoring of the metal plates on the sides of the blade root. In the example described here, the internal faces 26a and 28a of the metal plates 26 and 28 each comprise a straight knurling 265, 285 oriented perpendicular to the axis of the blade and, consequently, to the direction of the tensile force. applied at dawn. With such knurling, a coefficient of friction is obtained between the plates and the sides of the blade root close to 1, the clamping force to be applied in this case being equal to the maximum centrifugal force. The knurling can also be crossed or ribbed. The coefficient of friction between the plates and the flanks of the blade root can also be increased by forming a rough layer or abrasive, such as a layer of solder, between the metal plates and the sides of the blade root.

In addition, in order to avoid the appearance of local stresses between the screw-nut connection and the composite material of the blade and to allow the relaxation of the thermomechanical stresses, the passage orifice of the connection made in the blade root may have an oblong shape, as shown in the figure 5 which shows a root 114 of a blade 100 comprising an oblong passage orifice 125 extending along the length of the blade 100. The connection passage orifice formed in the blade root may have other suitable shapes such as scalloping.

In order to maintain the tightening force over the entire temperature range that the blade is likely to encounter in operation, a range typically between 0°C and 800°C, a material with a coefficient of thermal expansion greater than the coefficient of thermal expansion of the plates so that, during rises in temperature, the screw-nut system expands less than the plates, thus ensuring the maintenance of the prestress applied to the plates. By way of non-limiting examples, the screw and the nut can be made of high-performance nickel-based alloy of the Haynes ^® 242 ^® or Waspaloy ^® type, while the plates are made of A286 stainless steel or Inconel ^® 718.

Furthermore, the blade, the metal plates, the screw and the nut are made of materials which preferably have coefficients of thermal expansion changing in a similar manner over all or part of a temperature range between 0°C and 800°C. Indeed, by having a quasi-uniformity in the evolution curves of the coefficients of thermal expansion of all of these elements, the tightening behavior is better controlled during temperature variations. By way of non-limiting examples, a blade made of composite material with plates made of A286 stainless steel or Inconel ^® 718 and a screw-nut system made of a high-performance alloy based on nickel of the Haynes ^® 242 ^® or Waspaloy ^® type have coefficients of thermal expansion evolving in an identical manner. The metal plates are machined according to a shape making it possible to give the blade root a geometry adapted to the housing of the disc or wheel in which it must be inserted. In the example described here, the plates 26 and 28 are machined so as to respectively form portions of reduced thickness 262 and 282 giving the blade root, once mounted thereon, a bulbous shape capable of cooperating with a housing 51 of a rotor disc 50 as shown in the figures 6 and 7 . As illustrated on the figures 6 and 7 , each blade 10 is mounted on the disc 50 by engaging the root 14 clamped between the plates 26 and 28 in a housing or cell 51. Each housing 51 is separated from the adjacent housing by a tooth 52 comprising an upper part 53 having a bulging shape intended to retain the blade during the rotation of the disc.

According to the invention, the plates 26 comprise two portions 263 and 264 projecting from the outer surface of the plate and extending substantially perpendicular to this surface. Similarly, the plates 28 include two portions 283 and 284 projecting from the outer surface of the plate and extending substantially perpendicular to this surface. As illustrated on the figure 7 , the portions 263, 264, 283 and 284 act both as an anti-tilt wall for the blade and provide a sealing function, the portions 263 and 264 of a blade respectively coming into contact with the portions 283 and 284 from another adjacent blade.

The use of metal plates makes it possible to give the blade root a precise and reproducible geometry, and this in small dimensions, the low pressure compressor blade root described above typically having a width I of the order of 10mm ( figure 6 ) and must be inserted in a housing having equivalent dimensions without clearance.

Claims (11)

1. A rotor disk blade (10) for a turbine engine, the blade being made of composite material comprising fiber reinforcement obtained by multilayer weaving of yarns and densified by a matrix, the blade (10) having a portion constituting an airfoil (12) and a blade root (14) forming a single piece, the blade root (14) having two substantially plane opposite lateral flanks (22, 24) that are formed respectively extending the pressure side surface (12a) and the suction side surface (12b) of the airfoil (10), the blade root (14) being clamped between two metal plates (26, 28) fastened against the lateral flanks (22, 24) of the blade root by a bolt (30) and a nut (40) passing through the plates (26, 28) and the blade root (14), the bolt (30) having a head (31) bearing against one of the two plates (26) the nut (40) having a head (41) bearing against the other plate (28), the bolt and the nut (30, 40) applying some minimum level of clamping force against the metal plates (26, 28) for ensuring that a determined centrifugal force applied to the blade (10) is taken up by friction between the metal plates (26, 28) and the lateral flanks (22, 24) of the blade root (14),
   characterized in that each metal plate (26; 28) includes on its face opposite from its face in contact with the blade root (14) at least one projecting portion (263; 283), said projecting portion presenting a shape suitable for providing one or both of the following functions: opposing tilting and providing sealing.
2. A blade according to claim 1, characterized in that the bolt (30) and the nut (40) have respective heads (31; 41) of conical shape, and in that the metal plates (26, 28) include corresponding countersinks (261; 281).
3. A blade according to claim 1 or 2, characterized in that the blade root (14) includes an oblong hole (125) or festooning extending in the long direction of the blade (10) for passing the bolt and the nut.
4. A blade according to any one of claims 1 to 3, characterized in that the face (26a; 28a) of each plate (26; 28) facing the blade root presents a surface that is structured.
5. A blade according to claim 4, characterized in that the face (26a; 28a) of each plate (26, 28) facing the blade root (14) includes knurling (265; 285).
6. A blade according to any one of claims 1 to 5, characterized in that the metal plates (26, 28) have a coefficient of thermal expansion that is less than the coefficient of thermal expansion of the bolt (30) and of the nut (40).
7. A blade according to any one of claims 1 to 6, characterized in that the blade (10), the metal plates (26, 28), the bolt (30), and the nut (40) present coefficients of thermal expansion that vary in similar manner over all or part of a temperature range extending from 0°C to 800°C.
8. A turbine engine rotor disk (50) having a plurality of substantially axial metal slots (51) in its outer periphery, the disk being characterized in that it further includes a plurality of blades (10) according to any one of claims 1 to 7, each blade (10) being assembled by means of its root in a slot of the disk.
9. A turbine engine including at least one rotor disk (50) according to claim 8.
10. A method of assembling plates (26, 28) on a blade root (14), said blade being made of a composite material comprising fiber reinforcement obtained by multilayer weaving of yarns and densified by a matrix, the blade (10) having a portion constituting an airfoil (12) and a blade root (14) forming a single piece, the blade root (14) having two substantially plane opposite lateral flanks (22, 24) that are formed respectively extending the pressure side surface (12a) and the suction side surface (12b) of the airfoil (12), the blade root (14) being clamped between two metal plates (26, 28) fastened against the lateral flanks (22, 24) of the blade root (14) by a bolt (30) and a nut (40) passing through the plates (26, 28) and the blade root (14), the bolt (30) having a head (31) bearing against one of the two plates (26), the nut (40) having a head (41) bearing against the other plate (28), wherein, when tightening the bolt (30) with the nut (40), some minimum level of clamping force is applied to the metal plates (26, 28) to ensure that a determined centrifugal force applied to the blade (10) is taken up by friction between the metal plates (26, 28) and the lateral flanks (22, 24) of the blade root (14), characterized in that each metal plate (26; 28) includes on its face opposite from its face in contact with the blade root (14) at least one projecting portion (263; 283), said projecting portion presenting a shape suitable for providing one or both of the following functions: opposing tilting and providing sealing.
11. A method according to claim 10, characterized in that the minimum clamping force is determined by dividing the determined centrifugal force by the coefficient of friction between the metal plates (26, 28) and the lateral flanks (22, 24) of the blade root (14).

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