Timing system for articulated turbomachine blade, turbomachine blade equipped with this timing system and method for mounting such a timing system on an articulated blade

Abstract

Wedging system for articulated turbomachine blade, turbomachine blade equipped with this wedging system and method for mounting such a wedging system on an articulated blade One aspect of the invention relates to a wedging system (30) for a root (12) of an articulated turbomachine blade, said blade root being mounted so as to be able to rotate about a stacking axis (XX) of the blade, in a cavity (21) of a turbomachine disk (20), said wedging system comprising: a parallelepiped drive base (31) forming a support for the blade root (12), a device (32) for converting a rotational movement of the blade root into an axial translational movement, said movement conversion device being mounted at least partially around the drive base (31), and a spacer (33) mounted between the movement conversion device (32) and the disk (20) so as to block axially the position of the blade root (12) relative to the disc (20).Other aspects of the invention relate to an articulated blade wedged in the disk by means of this wedging system, a turbomachine equipped with such articulated blades and a method of mounting this wedging system on an articulated blade root. Figure to be published with the abstract: Figure 2.

Description

Title of the invention: Timing system for articulated turbomachine blade, turbomachine blade equipped with this timing system and method for mounting such a timing system on an articulated blade TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a timing system for an articulated turbomachine blade, such as a variable-pitch rectifier blade. It also relates to an articulated turbomachine blade equipped with such a timing system and to a turbomachine comprising such articulated blades. The invention further relates to a method for mounting this timing system on an articulated blade.

[0002] The invention finds applications in the field of turbomachines and, in particular, in the field of variable-pitch stator blades of a turbomachine.

[0003] The invention relates to the field of testing and makes it possible to test different angular settings of blading. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0004] It is known in aeronautics that the power of an engine can be improved by using a system of articulated blades, which can be oriented relative to the engine compressor casing. These articulated blades, also called variable-pitch blades, can be pivoted during engine operation in order to adapt their action according to the engine speed and flight conditions, so as to regulate the air flow supplying the compressor stages located downstream.

[0005] An example of an articulated blade (also simply called a blade) is shown in [Fig.l]. An articulated blade 10 generally comprises a blade 11 extending between a blade root 12 and a blade heel 13. Each articulated blade 10 is provided with a control rod, pivotally mounted in an opening passing through the compressor casing and extended by a control lever itself connected to a control ring. Actuators make it possible to rotate the control rings of the articulated blades to tilt the levers, and thus orient said blades.

[0006] In the lower part, the articulated blade is held in a cavity of the turbomachine disk by its blade root. The blade root is held radially in the cavity of the disk by cooperation of shapes between said root, generally in the form of a dovetail, and the cavity, generally in the form of a complementary cell. In operation, each row of blades is angularly wedged. "Wedge" is the setting of a chosen angular position and the maintenance of this wedged position in operation. This chosen position corresponds to a passive angle or orientation optimal orientation of the blade (relative to the axis of the turbomachine), i.e. its orientation when the compressor is stopped (or not operating).

[0007] Several wedging techniques are generally used to wedging the root of an articulated blade in a disk cavity. One of these techniques consists of clamping the blade root directly in the disk cavity. However, this technique presents a compressive force applied to the blade root, which can be problematic when the blade root is made of composite material. In addition, maintaining the wedging by clamping requires a clamping force that is difficult to control and generates a risk of loss of clamping during operation.

[0008] Other techniques consist of adding an intermediate piece to the blade root. This intermediate piece may be, for example, a shim machined specifically for each desired angular setting value, this shim making it possible to maintain the orientation of the blade. However, this technique of adding a shim requires anticipating the orientation angles to be obtained and generates uncertainties in the blade-to-blade setting due to the manufacturing tolerances of the shims. This technique also results in a play on the setting, substantially equivalent to the mounting clearance of the shim on the blade plus the mounting clearance of the blade in the disk.

[0009] The intermediate part added to the blade root can also be a system of connecting rods with a control ring (as on a conventional turbomachine with its VSV - Variable Stator Vanes system). However, the addition of such a system of connecting rods generates uncertainties in the blade-to-blade timing due to the entire chain of dimensions up to the control ring and the associated clearance, the chain of dimensions being involved in the functional dimensioning of the mechanical assembly and making it possible to check in particular the assembly clearances. The technique of adding a system of connecting rods presents, in addition to the uncertainties of the timing, difficult assembly and installation adjustments. In addition, this technique results in a certain heterogeneity of the mass and, consequently, an impact on the unbalance.

[0010] According to another technique, the added intermediate part can be a set of toothed wheels mounted on each blade root and meshed on a common toothed wheel around the engine axis. However, this technique presents uncertainties in the blade-to-blade timing due to the entire chain of dimensions up to the control ring and the associated clearance. It also presents a risk of jamming after operation and difficulties in mounting and adjusting the installation.

[0011] There is therefore a real need for a timing system making it possible to set and maintain the timing of the feet of the articulated blades in the cavities of the discs, at least passively (when the compressor is stopped). Summary of the invention

[0012] To address the problems mentioned above of the various known wedging techniques, the applicant proposes a system for wedging a compact, equally distributed articulated blade root with no play.

[0013] According to a first aspect, the invention relates to a wedging system for an articulated turbomachine blade root, said blade root being mounted to rotate about a blade stacking axis, in a cavity of a turbomachine disk, said wedging system comprising: • a parallelepiped drive base forming a support for the blade root, • a device for converting a rotational movement of the blade root into an axial translational movement, said movement conversion device being mounted at least partially around the drive base, and • a spacer mounted between the conversion device and the disc so as to axially block the position of the blade root relative to the disc.

[0014] Such a system for wedging an articulated blade in passive mode has the advantage, on the one hand, of not having any play and, on the other hand, of being compact due to the reduced number of parts which are all housed within a cavity of the disc.

[0015] In addition to the characteristics which have just been mentioned in the preceding paragraph, the wedging system according to one aspect of the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations: • the motion conversion device comprises a ball screw and a ball nut mounted around said ball screw. • the ball screw has an orifice receiving at least partially the drive base. • the ball screw hole is a through hole or a blind hole housed at one end of the ball screw. • the spacer is housed between the ball nut of the conversion device movement and the disk of the turbomachine. • the spacer is mounted around the ball screw.

[0016] A second aspect of the invention relates to a variable-pitch turbomachine blade comprising a blade extending between a blade heel and a blade root, said blade root being mounted to rotate inside a cavity of a turbomachine disk. This blade is characterized by the fact that it comprises a setting system as defined above.

[0017] Advantageously, the blade timing system is mounted around the stacking axis inside the cavity of the turbomachine disk.

[0018] A third aspect of the invention relates to a turbomachine comprising blades as defined above.

[0019] According to a fourth aspect, the invention relates to a method of mounting a wedging system comprising the following operations: • mounting the drive base on the blade root, • mounting the blade in the turbomachine disk, • mounting the motion conversion device around the base training, • adjustment of the blade timing, and • when the blade is wedged in the disc according to a chosen configuration, installation of the spacer to axially hold the motion conversion device.

[0020] Advantageously, the motion conversion device is mounted by shrink fitting onto the drive base.

[0021] According to certain embodiments, the motion conversion device comprises a ball screw and a ball nut mounted around said ball screw, the operation of mounting the motion conversion device then comprising: • a step of mounting the ball screw on the drive base, and • a step of screwing the ball nut around the ball screw until a predefined stop on the disc. BRIEF DESCRIPTION OF THE FIGURES

[0022] Other advantages and characteristics of the invention will appear on reading the following description, illustrated by the figures in which:

[0023] [Fig.l], already described, schematically represents an example of a variable-pitch rectifier blade seen in profile;

[0024] [Fig.2] represents a schematic sectional view of an embodiment of the wedging system according to the invention for wedging an articulated blade root mounted in a disk cavity;

[0025] [Fig. 3] represents an example of a ball screw used in an embodiment of the wedging system according to the invention;

[0026] [Fig.4] represents a schematic view of another example of a system for wedging an articulated blade root; and

[0027] [Fig. 5] shows several schematic views of the wedging system according to the invention during its assembly on an articulated blade root. DETAILED DESCRIPTION

[0028] An exemplary embodiment of a wedging system for an articulated blade root and an example of mounting such a system are described in detail below, with reference to the attached drawings. These examples illustrate the characteristics and advantages of the invention. It is however recalled that the invention is not limited to these examples.

[0029] In the figures, identical elements are identified by identical references. For reasons of readability of the figures, the size scales between elements represented are not respected.

[0030] An example of the wedging system for an articulated blade root is shown in a sectional view in [Fig. 2]. In this [Fig. 2], a portion of the articulated blade 10 is shown mounted in a cavity 21 of a turbomachine disk 20. The cavity 21 comprises a neck 22 in the overall shape of a cell, adapted to receive and hold the blade root 12, in the shape of a revolution whose section is generally representative of a dovetail. The neck 22 of the cavity 21 and the blade root 12 have substantially complementary shapes which allow cooperation of shapes between said blade root and said cavity. When the turbomachine is in operation, the centrifugal force of the blade 10 rotating around the axis of rotation RR generates a mauling zone 23, also called a mauling surface, at the level of which the blade root 12 bears against the neck 22 of the cavity 21.This matting zone 23 takes up the centrifugal forces of the blade in operation and ensures the maintenance of the blade root 12.

[0031] The cavity 21 of the disc 20 comprises a chamber 23 in which the wedging system 30 according to the invention is housed. This wedging system 30 comprises a drive base 31, a motion conversion device 32 and a spacer 33, nested with each other along a stacking axis XX. This stacking axis XX extends radially along the length of the articulated blade 10. The root of the moving blade is mounted to rotate about this stacking axis XX. In other words, the stacking axis XX is a mounting axis of the wedging system, aligned with the axis of the articulated blade 10 and generally perpendicular to the rotation axis RR of the turbomachine.In the remainder of the description, the positioning of the parts relative to each other will be defined along this stacking axis XX, between the bottom 24 of the cavity of the disc (which is the part closest to the rotation axis RR, located near an internal end XI of said stacking axis) and the articulated blade 10 (which is the part furthest from the rotation axis RR, located near an external end X2 of said stacking axis).

[0032] The wedging system according to the invention therefore comprises, from the internal end XI of the stacking axis XX towards the external end X2 of said stacking axis: • a spacer 33 bearing on the bottom 24 of the cavity 21 of the disc, • a movement conversion device 32 for converting a rotational movement into a translational movement, and • a drive base 31 serving as support for the blade root 12.

[0033] The drive base 31, also simply called base, is a part of generally parallelepiped shape positioned under the blade root 12 to form a support for said blade root 12. The base 31 is an integral part of the blade root, said blade root 12 therefore being extended by said base 31. In certain embodiments, the drive base 31 has the shape of a cube or a right block. The drive base 31, dimensioned to take up the torsional forces around the stacking axis XX, is housed at least partially in the motion conversion device 32. The motion conversion device 32 has the function of transforming the rotational movement of the blade root 12 into an axial translational movement making it possible to move the blade root along the stacking axis XX.The base 31 is mounted with a tight fit in the motion conversion device so that the torsional forces of the blade about the stacking axis XX are communicated to the motion conversion device 32 which then translates along the stacking axis XX.

[0034] According to certain embodiments, the motion conversion device 32 comprises a ball screw 321 and a ball nut 322. Other embodiments of the motion conversion device 32 may be envisaged, such as, for example, a cam system.

[0035] [Fig. 2] shows the example where the motion conversion device 32 is a ball screw and ball nut assembly. According to this example, the ball screw 321 is mounted at least partially around the drive base 31, centered on the stacking axis XX. The ball nut 322 is mounted around the ball screw 321. The ball screw and ball nut assembly makes it possible to transform a rotational movement into a translational movement, thanks to the recirculation of balls along the screw pitch of the ball screw, inside the ball nut.

[0036] An example of a ball screw 321 is shown schematically in a perspective view in [Fig. 3]. This ball screw 321 comprises a cylindrical body 321a extending along the stacking axis XX and the outer wall of which is provided with a screw thread 321b. This ball screw 321 comprises an upper transverse face 321d equipped with an orifice 321c receiving at least partially the drive base 31. In other words, the orifice 321c is provided to house the entire base 31 so that the base is flush with the transverse face 321d of the ball screw or only part of the base 31 so that the base 31 projects from the transverse face 321d of the ball screw. The orifice 321c may be a through orifice or a blind orifice made in the transverse face 321d of the ball screw which is the face opposite the blade root 12. This orifice 321c has previously been machined so as to be mounted on the base 31 with slight shrinkage.

[0037] The ball nut 322 is equipped, on its inner wall, with an additional screw thread forming, with the screw thread 321b of the ball screw 321, a circular path ball assembly. This ball nut 322, screwed around the ball screw 321, can be in abutment on a support surface 25 of the disc 20. The ball nut 322, thus screwed around the ball screw 321 until it comes into contact with the support surface 25, forms a stop for the motion conversion device 32.

[0038] The wedging system 30 also comprises a spacer 33 housed between the motion conversion device 32 and the bottom 24 of the cavity 21 of the disc. This spacer 33 is positioned under the motion conversion device 32 or nested with said device 32 and centered around the stacking axis XX. Its function is to prevent the motion conversion device 32 from moving and thus maintain the blade root 12 in the chosen wedging position.

[0039] In the example of [Fig. 2] where the motion conversion device 32 is a ball screw and ball nut assembly, the spacer 33 is a shim provided with a central orifice 33a of dimensions adapted to the external dimensions of the ball screw 321. The spacer 33 comprises a first transverse face 33b bearing against the bottom 24 of the cavity, a second transverse face 33d against which the ball nut 322 bears and an intermediate face 33c (formed by the bottom of the central orifice 33a) against which the ball screw bears. The spacer 33 is thus nested between the ball screw 321, the ball nut 322 and the bottom 24 of the cavity of the disc and prevents any movement of the ball screw, the ball nut and the base 31.Indeed, in operation, the torsional forces of the blade 10 around the stacking axis XX are communicated to the threaded part of the ball screw 321; these forces force the threaded part of the ball screw 321 or the ball nut 322 to translate along the stacking axis. However, the translation of the ball screw and the ball nut is blocked by the spacer 33; the blade therefore remains locked in the position and orientation set during assembly.

[0040] Another example of a wedging system 30 is shown in [Fig. 4]. This [Fig. 4] shows a blade root 12 inserted into a neck 22 of a disk cavity 20. The blade root 12 is extended by a base 31 housed in an orifice of a ball screw 321. In this example, the ball screw 321 is held in the cavity of the disk 20 by a pivot rod 40, passing through the bottom 24 of the cavity of the disk and housed in a lower transverse face 321e (the lower transverse face 321e being the face of the ball screw opposite the upper transverse face 321d). A ball nut 322, in abutment against a support surface 25 formed by the disc 20, is mounted around the ball screw 321. A spacer 33 is inserted under the ball nut 322 to block the translation of said ball nut 322 along the axis of rotation of the blade.This spacer 33 may be covered with an elastomer coating so as to introduce slight friction and counteract the residual rotation of the ball nut 322.

[0041] Whatever the embodiment, the movement conversion device 32 of the wedging system 30 makes it possible to convert all or almost all of the forces of torsion around the stacking axis XX in translational force along this same axis. In the event of residual torsion, a flexible coating, such as for example an elastomeric deposit, can be added to the contact interfaces between the ball nut 322 and the disc 20 and / or the ball nut 322 and the spacer 33 so as to increase the coefficient of friction at these interfaces.

[0042] [Fig. 5] represents in four diagrams the method of mounting the wedging system according to the invention on a blade root 12. Step A shows the installation of the ball screw 321 on the blade root 12. As explained previously, the blade root 12 is extended by a base 31 previously fixed on said blade root. Once the blade root 12 is installed in the cavity 21 of the disc, the ball screw 321 is mounted on the blade root by inserting the base 31 into the orifice of the ball screw by a shrink-fitting type technique allowing a play-free fit. Once the ball screw is installed, the ball nut 322 is mounted around the ball screw by screwing. A pivot rod 40 is then introduced into the ball screw 321, via the lower transverse face of said ball screw, in order to maintain the ball screw and ball nut assembly in alignment with the blade root 12 (step B of [Fig.5]).The position and orientation of the articulated blade can then be adjusted so that said blade is in the chosen configuration. The ball nut 322 is then screwed and adjusted until it comes into contact with the bearing surface 25 of the disc 20 (step C of [Fig. 5]). In step C, it is still possible to modify the position and / or orientation of the articulated blade. In step D, the spacer 33 is interposed between the bottom 24 of the cavity and the ball nut 322 and / or the ball screw 321 so as to axially hold said ball nut and said ball screw.

[0043] The system as just described allows the blades to be set one by one in passive mode, i.e. when the turbomachine is stopped. It allows each blade to be adjusted and set differently in a continuous and non-discrete manner by means of a reduced number of parts, all housed in a cavity of the disk - which makes the system compact - and distributed in a balanced manner around the stacking axis - which minimizes unbalance. In addition, the system has no play. This setting system also allows, when the turbomachine is in operation, to convert the torque exerted by the blades into a compression force along the stacking axis XX.

[0044] Although described through a certain number of examples, variants and embodiments, the wedging system according to the invention, the blade comprising this wedging system and the method of mounting this system comprise various variants, modifications and improvements which will appear obvious to those skilled in the art, it being understood that these variants, modifications and improvements are part of the scope of the invention.

Claims

Claims

1. Wedging system (30) for a root (12) of an articulated turbomachine stator blade, said blade root being mounted to rotate about a stacking axis (XX) of the blade, in a cavity (21) of a turbomachine disk (20), said wedging system comprising: - a parallelepiped drive base (31) forming a support for the blade root (12), - a device (32) for converting a rotational movement of the blade root into an axial translational movement, said movement conversion device being mounted at least partially around the drive base (31), and - a spacer (33) mounted between the movement conversion device (32) and the disk (20) so as to axially block the position of the blade root (12) relative to the disk (20).

2. A wedging system according to claim 1, characterized in that the motion conversion device (32) comprises a ball screw (321) and a ball nut (322) mounted around said ball screw.

3. Wedging system according to claim 2, characterized in that the ball screw (321) comprises an orifice (321c) at least partially receiving the drive base (31).

4. A wedging system according to claim 3, characterized in that the orifice (321c) of the ball screw (321) is a through orifice or a blind orifice housed at one end of the ball screw.

5. Wedging system according to any one of claims 2 to 4, characterized in that the spacer (33) is housed between the ball nut (322) of the motion conversion device and the disc (20) of the turbomachine.

6. A wedging system according to any one of claims 2 to 5, characterized in that the spacer (33) is mounted around the ball screw (321).

7. Variable-pitch turbomachine blade (10) comprising a blade (11) extending between a blade heel (13) and a blade root (12), said blade root being mounted to rotate inside a cavity (21) of a turbomachine disk (20), characterized in that it comprises a wedging system (30) according to any one of claims 1 to 6.

8. Turbomachine blade according to claim 7, characterized in that the wedging system (30) is mounted around the stacking axis (XX) inside the cavity (21) of the turbomachine disk.

9. Turbomachine comprising blades according to any one of claims 7 and 8.

10. Method for mounting a wedging system (30) according to any one of claims 1 to 6 on a root (12) of an articulated turbomachine blade, said method comprising the following operations: - mounting the drive base (31) on the blade root (12), - mounting the articulated blade (10) in the disk (20) of the turbomachine, - mounting (A, B) of the motion conversion device (32) around the drive base (31), - adjusting (C) the timing of the articulated blade, and - when the articulated blade (10) is wedged in the disk (20) according to a chosen configuration, installation of the spacer (33) to axially hold the motion conversion device.

11. Mounting method according to claim 10, characterized in that the motion conversion device (32) is mounted by shrink fitting onto the drive base (31).

12. Mounting method according to claim 10 or 11, characterized in that the motion conversion device (32) comprises a ball screw (321) and a ball nut (322) mounted around said ball screw, the operation of mounting the motion conversion device (32) then comprising: - a step (A) of mounting the ball screw on the drive base, and - a step (B, C) of screwing the ball nut (322) around the ball screw (321) up to a predefined stop (25) on the disc.

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