Conical shimming device for moving blade and assembly comprising it

Abstract

Conical shimming device for movable blade and assembly comprising it. The turbomachine assembly comprises movable blades (2), each having a blade (4) fixed on a foot (5) and each immobilized by its foot (5) on the outer radial face (6) of a rotor (3) with axis (X-X') by a shimming device (1). At least one shimming device (1) for a movable blade (2) comprises a male fixing piece (8) of conical or frustoconical shape with axis of revolution (Z-Z'), fixed to the foot (5) or integral with it; said male fixing piece (8) having a tapered end (11) directed radially inwards along the axis (Z-Z'); and a female receiver housing (9) of conical or frustoconical shape complementary to the male mounting piece (8), formed in the external radial face (6) of the rotor (3) or formed in a piece fixed to the external radial face (6) of the rotor (3). Figure to be published with the abbreviation: Figure 2

Description

Title of the invention: Conical wedging device for moving blade and assembly comprising it TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of moving blades intended to be used in a test turbomachine.

[0002] The present invention relates to a timing device for such moving blades. It is intended for any type of turbomachine, land-based or aeronautical, and more particularly for aircraft turbojets. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] In most bypass turbojets, a fan is placed in front of the low-pressure compressor. This fan consists of large blades mounted radially along a Z-Z' axis on a rotor with an X-X' axis. These blades are usually referred to as moving blades or fan blades. The incidence of these blades varies from the root to the tip of the blade. The angle of orientation of the moving blades around the Z-Z' axis along which they extend (this orientation being represented by circular arrows in the figures), as well as their incidence, are decisive with respect to the overall performance of the turbomachine they equip. In turbojets, the angle of orientation of the moving blades can be modified in flight depending on the engine speed.

[0004] When various orientation angles for new moving blades are tested on a test turbomachine, particularly during performance tests, these moving blades are usually removably attached to the rotor. This attachment is designed to be quick and easy to implement for each of the moving blades. This assembly must also allow the orientation angle of the moving blades to be quickly and easily modified. Since a turbomachine generally comprises several dozen moving blades, adjusting the orientation of the moving blades is generally a long and tedious operation.

[0005] Adjusting the orientation angle of the moving blades is usually referred to as setting and the device for fixing a blade to a rotor allowing several orientation angles is usually referred to as a setting device.

[0006] Shimming is an operation which is carried out when the turbomachine is stopped, before a test. It must be clearly understood that the shimming devices concerned by the invention are not usually intended for mounting the moving blades in a turbojet intended to be used in flight. These are shimming devices intended solely for fixing blades during tests of a turbomachine, for which safety standards are lower than for a real turbomachine intended for commercial use, particularly with regard to the risk of a blade being expelled under the effect of centrifugal force.

[0007] There are currently several devices for wedging the moving blades on a test turbomachine. Among these devices are various systems for exerting pressure on the root provided at the base of each moving blade, for example by clamping the root by a jaw, by a stirrup or by a transverse screw fixed on the rotor. There are also toothed systems, in which the root of the moving blades is notched and locked in rotation by a second notched element fixed on the rotor.

[0008] Wedging devices have many disadvantages. Indeed, some wedging devices include screws that protrude into the aerodynamic vein and generate turbulence therein. Wedging devices also include parts that are complicated and expensive to manufacture. Other devices include parts that are difficult to access and / or complicated and time-consuming to implement when adjusting the orientation angle of the moving blades. Similarly, other devices are unsatisfactory in that they do not allow perfect immobilization of the moving blades in place and in orientation, a play remaining for example in the wedging. Finally, other devices are bulky and have an unsatisfactory azimuthal size.

[0009] In the field of test turbomachines, there is therefore a need for a timing device for a moving blade which is simple, inexpensive, easy to use and manufacture, quickly implemented, reliable and without play, which does not generate turbulence in the aerodynamic vein and which does not present additional azimuthal bulk at the rotor level. Summary of the invention

[0010] The invention offers a solution to the problems mentioned above by providing a wedging device using a low-slope fitting cone, for example of the Morse cone type, where the root of each moving blade is conical in shape and is received in a complementary conical housing provided in the rotor.

[0011] One aspect of the invention relates to a turbomachine assembly comprising moving blades each comprising a blade fixed to a root and each immobilized by their root on the external radial face of a rotor of axis X-X' by a wedging device, where at least one wedging device for a moving blade comprises: • a male fixing part of conical or frustoconical shape of axis of revolution Z-Z', fixed to the root or in a single piece with it; said male fixing part having a tapered end directed radially towards the interior along the Z-Z' axis; and • a female receiving housing of conical or truncated shape complementary to the male fixing part, shaped in the external radial face of the rotor or shaped in a part fixed on the external radial face of the rotor.

[0012] The principle of the wedging device of the invention is based on the use of a fitting cone with a low slope. Due to the centrifugal force to which the moving blades are subjected during testing of turbomachines and the subsequent risk of radial ejection of said moving blades during rotation of the turbomachine, those skilled in the art have always considered that such a conical wedging device could not be envisaged for the wedging of moving blades. Indeed, the absence of a locking means specifically dedicated to preventing the radial displacement of the moving blades seems hazardous. However, tests have shown that the wedging device of the invention can ensure axial locking of at least 4000 daN for moving blades, whereas, during testing of turbomachines, the centrifugal force experienced by the blades during testing of turbomachines is 3000 daN at most.Surprisingly, in addition to ensuring blocking in other directions, the conical wedging device of the invention therefore ensures more than sufficient axial blocking.

[0013] This wedging device for a moving blade also has all the advantages sought and mentioned above. In particular, it allows very easy and very rapid mounting of the moving blades on the rotor and allows the orientation angle of the moving blades to be modified quickly, easily and freely. This mounting is also very precise because the conical shape ensures very good centering of the moving blade around the axis of revolution Z-Z' and makes it possible to perfectly maintain both the (adjustable) orientation angle of the moving blade around the axis of revolution Z-Z' and the radial inclination angle of the moving blade relative to the axis Z-Z'.

[0014] In addition to the characteristics which have just been mentioned in the preceding paragraph, the assembly 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 male fixing part has a taper of between 4.5% and 5.5%, preferably between 4.7% and 5.3%, and more preferably between 4.9% and 5.1%. • the male fixing part has an angle a at the apex of the cone or truncated cone of between 0.045 and 0.055 radians, preferably between 0.047 and 0.053 radians, and preferably between 0.049 and 0.051 radians. • the surface roughness Ra of the cone or truncated cone of the male fixing part and the female receiving housing is less than or equal to 1 pm, preferably

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[0023] preferably less than or equal to 0.9 pm and more preferably less than or equal to 0.8 pm. • the female receiving housing is delimited by a single-piece peripheral wall. • the male fixing part is made of metal, preferably steel or inconel®. • the foot of the moving blade has a platform located between the blade and the male fixing part. • the female receiver housing includes a receiving part for the platform. • the assembly includes a device for extracting the moving blade. • the extraction device comprises a lever fixed tilting on the rotor, said lever comprising a first end accessible from the outside of the rotor and a second end located opposite the tapered end of the male fixing part. • the turbomachine is a test turbomachine, preferably a double-flow test turbojet. Another aspect of the invention relates to a turbomachine comprising an assembly according to the invention. The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES The figures are presented for information purposes only and do not limit the invention. Certain dimensions have been exaggerated for clarity of the figures. [Fig.l] is a schematic perspective view of a moving blade equipped with a male fixing part according to an exemplary embodiment of the invention. [Fig.2] is a schematic sectional view of a moving blade according to [Fig.l] and mounted in a female receiving housing according to an exemplary embodiment of the invention formed in the external radial face of a rotor. [Fig.3] is a view similar to that of [Fig.2], where the movable blade is extracted from the rotor by means of an extraction device according to an exemplary embodiment of the invention. [Fig.4] is a side view of a truncated cone of a male fixing part according to an exemplary embodiment of the invention. DETAILED DESCRIPTION Unless otherwise specified, the same element appearing in different figures has a single reference. By convention, in this application, the terms “interior” and “exterior”, "lower" and "upper", and "inner" and "outer" are defined radially relative to the longitudinal axis X-X' along which the turbomachine extends. Thus, a cylindrical part extending along the axis of the engine has an inner face facing the longitudinal axis of the turbojet and an outer surface, opposite its inner surface. Similarly, the term "longitudinal" or "axial" corresponds to a direction parallel to the longitudinal axis X-X', while the term "radial" means a direction perpendicular to the axis X-X'.

[0024] The invention relates to a wedging device 1 for a moving blade 2 making it possible to quickly mount a moving blade 2 on a rotor 3 with an axis X-X' while adjusting the angle of orientation of said moving blade 2 around the axis Z-Z' along which it extends.

[0025] As illustrated in [Fig.l] to [Fig.3], a moving blade 2 usually comprises a blade 4 and a root 5 by which it can be fixed on the external radial face 6 of a rotor 3. A moving blade 2 can also comprise a platform 7, for example in the form of a disc, located in the lower part of the blade 4.

[0026] The invention also relates to an assembly for a turbomachine comprising moving blades 2 mounted on a rotor 3 by a timing device 1 according to the invention.

[0027] The wedging device 1 according to the invention comprises a male fixing part 8 provided on the moving blade 2 and a female receiving housing 9 provided in the external radial face 6 of the rotor 3 and intended to receive said male fixing part 8.

[0028] The male fixing part 8 forms a pivot and is in the shape of a cone or a truncated cone, each with an axis of revolution Z-Z'. Indeed, the axis of revolution Z-Z' of the cone or truncated cone is identical to the axis around which the moving blade 2 can pivot during its angular orientation.

[0029] The male fixing part 8 has a flared end 10 which is fixed to the root 5 of the moving blade 2 or in one piece with it, and a tapered end 11 which is intended to be received in the female receiving housing 9. When the male fixing part 8 is mounted on a rotor 3, the tapered end 11 of the male fixing part 8 is directed radially inwards along the axis Z-Z'.

[0030] The female receiving housing 9 is in the shape of a cone or a truncated cone, each with an axis of revolution Z-Z', this cone or truncated cone being of a shape complementary to that of the male fixing part 8, so that the male fixing part 8 can be received in a fitted manner in the female receiving housing 9. The female receiving housing 9 is shaped in the external radial face 6 of the rotor 3 or is shaped in a part fixed on the external radial face 6 of the rotor 3.

[0031] As seen in [Fig.4], the male fixing part 8 is of truncated cone shape. This truncated cone has a large diameter D located on the external side, a small diameter d located on the internal side, a radial length L and an angle a at the apex.

[0032] According to a preferred embodiment of the invention, the male fixing part 8 has a conicity of between 4.5% and 5.5%, preferably between 4.7% and 5.3%, and more preferably between 4.9% and 5.1%. As a reminder, the conicity is equal to (D - d) / L x 100.

[0033] According to a preferred embodiment of the invention, the angle α at the apex of the cone or truncated cone is between 0.045 and 0.055 radians, preferably between 0.047 and 0.053 radians, and preferably between 0.049 and 0.051 radians.

[0034] According to a preferred embodiment of the invention, the surface roughness Ra of the cone or truncated cone of the male fastening part 8 and the female receiving housing 9 is less than or equal to 1 μm, preferably less than or equal to 0.9 μm and more preferably less than or equal to 0.8 μm. This very low roughness allows a tight fit of the male fastening part 8 in the female receiving housing 9, with satisfactory adhesion with respect to the centrifugal force during the rotation of the rotor 3. When fitting the male fastening part 8 into the female receiving housing 9, the male fastening part 8 can be slightly deformed in compression, which further improves the adhesion previously mentioned.

[0035] During tests of a bypass turbojet operating at maximum speed, moving blades 2 mounted on a rotor 3 with a setting device 1 having the preferred geometries given above resisted a centrifugal force of 3000 daN and remained in place on the rotor 3 with the original orientation angle which had been given to them. This holding in place of the moving blades 2, which also resists the centrifugal force, is obtained by the friction of the conical or frustoconical external surface 12 of the male fixing part 8 against the internal face of the peripheral wall 13 which delimits the female receiving housing 9, this adhesion between the two parts in tight engagement works a little like a light hooping.For these tests, the dimensions of the truncated cone of the male fixing part 8 were substantially as follows: D = 45 mm, d = 40 and L = 70 mm, with a taper of approximately 0.051 and an angle α at the apex of approximately 3 degrees, or approximately 0.0525 radians.

[0036] The male fixing part 8 is made of metal, preferably steel or inconel®. Since the blade 4 is usually made of composite material, the root 5 of the moving blade 2 preferably comprises a platform 7 located between the blade 4 and the male fixing part 8. This platform 7 forms the interface between the blade 4 and the male fixing part 8 and allows better mutual attachment of these parts 4, 8.

[0037] In the case where the root 5 of the mobile blade 2 comprises such a platform 7, the female receiving housing 9 also comprises a receiving part 20 for the platform 7 so as to reconstitute the aerodynamic zone and not present any disturbance in the aerodynamic vein around the rotor 3.

[0038] According to another embodiment of the invention, the male fixing part 8 can be in one piece with the blade 4.

[0039] The female receiving housing 9 is preferably delimited by a peripheral wall 13 which is a single piece. Thus the female receiving housing 9 is not formed from several assembled parts, which in particular avoids an assembly of several parts, and risks of geometry defects or play between the male fixing part 8 and the female receiving housing 9 into which it is inserted.

[0040] The fact that the peripheral wall 13 is made of a single piece distinguishes the female receiving housing 9 of the invention from receiving housings of the prior art, formed of several pieces which enclose a part of the root 5 of a moving blade 2 to immobilize it. Indeed, these receiving housings have numerous disadvantages and are not based on the same principle as the invention.

[0041] According to a preferred embodiment of the invention, the wedging device 1 comprises a device 14 for extracting the moving blade 2 (see [Fig.2] and [Fig.3]).

[0042] The extraction device 14 comprises for example a lever 15 fixed tilting on the rotor 3, preferably on an internal face 16 of said rotor 3, said lever 15 comprising a first end 17 accessible from the outside of the rotor 3, for example by a through orifice 18, preferably radial, provided in the external radial face 6 of the rotor 3, and a second end 19 situated opposite the tapered end 11 of the male fixing part 8.

[0043] According to this embodiment, when pressure is exerted inwards on the first end 17 of the lever 15, the latter tilts around its axis of rotation R, and the second end 19 of the lever 15 exerts an equivalent force pressure directed outwards, under the male fixing part 8, which makes it possible to extract the latter from the female receiving housing 9 (see [Fig. 3]).

[0044] The extraction device 14 therefore makes it possible to uncouple the moving blade 2 without having to exert force on the blade 4, which is likely not to be sufficiently strong with respect to the forces that it would have to undergo if it were stressed, in particular in traction, with a view to extracting the male fixing part 8 from the female receiving housing 9. Furthermore, it is generally difficult to grip a moving blade 2 with a tool with a view to exerting such stresses.

[0045] A force may for example be exerted on the first end 17 of the lever 15 by means of a rod introduced from the outside through the through-hole 18 and for example struck by a mallet, or by screwing a screw into said through-hole 18, which may then be at least partially threaded. These embodiments advantageously make it possible to disengage the moving blade 2 quickly and simply from the outside, without having to dismantle any part beforehand.

[0046] Other extraction devices can of course be envisaged.

[0047] It will be noted that the wedging device 1 can be used for the assembly of any any part mounted on a rotor, in particular when it is desired to be able to quickly and simply modify the angle of orientation of said part around the Z-Z' axis along which it extends radially relative to said rotor.

Claims

Claims

1. Assembly for a turbomachine comprising moving blades (2) each comprising a blade (4) fixed on a root (5) and each immobilized by their root (5) on the external radial face (6) of a rotor (3) of axis (X-X') by a wedging device (1), characterized in that at least one wedging device (1) for a moving blade (2) comprises: - a male fixing part (8) of conical or frustoconical shape of axis of revolution (Z-Z'), fixed to the root (5) or in a single piece therewith; said male fixing part (8) having a tapered end (11) directed radially inwards along the axis (Z-Z'); and - a female receiving housing (9) of conical or truncated shape complementary to the male fixing part (8), formed in the external radial face (6) of the rotor (3) or formed in a part fixed on the external radial face (6) of the rotor (3).

2. Assembly according to claim 1, characterized in that the male fixing part (8) has a conicity of between 4.5% and 5.5%, preferably between 4.7% and 5.3%, and more preferably between 4.9% and 5.1%.

3. Assembly according to claim 1 or 2, characterized in that the male fixing part (8) has an angle a at the apex of the cone or truncated cone of between 0.045 and 0.055 radians, preferably of between 0.047 and 0.053 radians, and preferably of between 0.049 and 0.051 radians.

4. Assembly according to any one of the preceding claims, characterized in that the surface roughness Ra of the cone or truncated cone of the male fixing part (8) and of the female receiving housing (9) is less than or equal to 1 pm, preferably less than or equal to 0.9 pm and more preferably less than or equal to 0.8 pm.

5. Assembly according to any one of the preceding claims, characterized in that the female receiving housing (9) is delimited by a peripheral wall (13) in one piece.

6. Assembly according to any one of the preceding claims, characterized in that the male fixing part (8) is made of metal, preferably mainly made of steel or inconel®.

7. Assembly according to any one of the preceding claims, characterized in that the foot (5) of the moving blade (2) comprises a platform (7) located between the blade (4) and the male fixing part (8).

8. Assembly according to the preceding claim, characterized in that the female receiving housing (9) comprises a receiving part (20) for the platform (7).

9. Assembly according to any one of the preceding claims, characterized in that it comprises a device (14) for extracting the moving blade (2).

10. Assembly according to the preceding claim, characterized in that the extraction device (14) comprises a lever (15) fixed tilting on the rotor (3), said lever (15) comprising a first end (17) accessible from the outside of the rotor (3) and a second end (19) located opposite the tapered end (11) of the male fixing part (8).

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