Turbomachine bladed device comprising a blade root positioning assistance device

Abstract

The invention relates to a turbomachine bladed disk comprising a disk, provided with at least one groove made at the periphery of the disk, and at least one blade (26) comprising a blade root (26a) housed in a groove of the disk, the blade root (26a) comprising a first contact surface (26b) and the groove comprising a second contact surface, characterized in that at least one of the first contact surface (26b) and the second contact surface comprises at least partially a device (40) for assisting the positioning of the root (26a) in the groove, comprising an electrical circuit of variable conductivity depending on the nature of the contact between the first contact surface (26b) and the second contact surface. Figure for abstract: Figure 4

Description

Title of the invention: Turbomachine bladed device comprising a blade root positioning assistance device TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the general field of turbomachines, and more specifically to the field of devices for positioning the root of a turbomachine blade, for example a fan blade, in an associated groove of a rotor disk of the turbomachine.

[0002] The invention applies to any type of land or aeronautical turbomachines, and in particular to aircraft turbomachines such as turbojets and turboprops.

[0003] The invention thus proposes a turbomachine bladed disc comprising a device for assisting in positioning the root of a blade of the bladed disc, an associated positioning assistance method, as well as a turbomachine comprising such a bladed disc. STATE OF THE ART

[0004] In a turbomachine, for example a turbojet, the blades, composed of a root and a blade defined by two sides called respectively intrados and extrados, are mounted in groove-shaped housings, called cells or grooves, specially arranged on the periphery of the rotor disks. These grooves can be straight or curvilinear. The blades are mounted with a clearance between their root and the walls of the grooves.

[0005] For the proper operation of the turbojet, it is necessary that the blades are correctly positioned during assembly in the grooves so that the blade roots and the grooves of the disk are in contact throughout the engine's rotation range. The contact surfaces between the blade roots and the grooves are called mauling surfaces. The mauling surfaces of the roots and those of the grooves must therefore be in perfect contact during assembly. It is thus possible to take up the clearance between the bottom of the grooves and the end of the blade roots to ensure the correct positioning of the blade roots on the disc surfaces.In addition, this contact makes it possible to limit the tilting of the blades in their grooves and, in certain cases of malfunction, for example in the event of an impact following the ingestion of a foreign body or in the event of loss of a blade, to also limit the risk of wear by friction or other possible deterioration of the bearing surfaces of the blades or the disc.

[0006] On certain older generation turbomachines, the correct positioning of the blade roots in the grooves could be ensured by the existence of fins whose were provided with the blades. However, on most current turbomachines, the positioning of the feet in the grooves is done manually.

[0007] In a known manner, this positioning and holding in place of the blades is ensured by wedges slid into the grooves, under each blade root. An example of the embodiment of such wedges is for example described in the European patent application EP 2 014 873 A1 of the Applicant.

[0008] However, it happens that the locking of the blade in position by means of such a wedge between the disc tooth and the root of the blade is carried out incorrectly and that the blade is locked askew, with an unwanted orientation, which is then detrimental to its behavior in operation.

[0009] There is thus a need to ensure the correct positioning of the blade root in the groove during assembly. In particular, there is a need to prevent the blade root from being assembled in the groove with an inappropriate orientation of the root likely to impact the behavior of the blade during operation of the turbomachine. Statement of the invention

[0010] The invention aims to at least partially remedy the needs mentioned above and the drawbacks relating to the embodiments of the prior art.

[0011] The invention thus relates, according to one of its aspects, to a turbomachine bladed disk comprising a disk, provided with at least one groove made at the periphery of the disk, and at least one blade comprising a blade root housed in a groove of the disk, the blade root comprising a first contact surface and the groove comprising a second contact surface,

[0012] characterized in that at least one of the first contact surface and the second contact surface comprises at least partially a device for assisting in positioning the foot in the groove, comprising an electrical circuit of variable conductivity depending on the nature of the contact between the first contact surface and the second contact surface.

[0013] Thanks to the invention, it is possible to check the correct positioning of the blades in the grooves of the disk of a turbomachine bladed disk. In particular, during assembly, it is possible to be informed about the quality of the positioning of the blades by means of a positioning assistance device functioning as an in situ sensor whose conductivity varies according to the quality of contact.

[0014] The positioning device according to the invention may further comprise one or more of the following characteristics taken in isolation or in any possible technical combination.

[0015] The first contact surface of the blade root may be a root masting surface. extending substantially longitudinally along the axis of rotation of the bladed disc. In addition, the second contact surface of the groove may be a groove matting surface extending substantially longitudinally along the axis of rotation of the bladed disc.

[0016] Furthermore, the electrical circuit may be a flexible printed electrical circuit fixed to at least one of the first contact surface and the second contact surface, in particular by gluing.

[0017] In particular, the electrical circuit may comprise at least two nested conductive patterns between which electrical conductivity is established upon contact with a conductive metal surface, the conductivity increasing with the metal surface in contact with the electrical circuit.

[0018] Each conductive pattern may comprise a terminal for connection to a conductivity measuring device, in particular an ohmmeter, in particular located on a surface of the blade root and / or the disk accessible by an operator, for example a front surface of the blade root and / or the disk, substantially transverse to the axis of rotation of the bladed disk.

[0019] Furthermore, the positioning aid device may preferably be located on a root bearing surface and on a front surface of the blade root, substantially transverse to the axis of rotation of the bladed disc.

[0020] Furthermore, the invention also relates, according to another of its aspects, to a method for assisting in the positioning in a groove of a blade root of a blade of a bladed disc as defined above, comprising the steps consisting of: - positioning the blade root in a groove of the disc, - carrying out a measurement of the electrical conductivity at the positioning aid device, in particular by means of an ohmmeter, - orient the blade root in the groove so as to obtain a maximum value of the electrical conductivity measured at the positioning aid device, - possibly, position a shim in the groove under the blade root.

[0021] The maximum value of the electrical conductivity measured at the positioning aid device can advantageously be predetermined by means of a calibration step consisting of placing a metallic element in contact with the electrical circuit to define a target conductivity to be achieved during assembly.

[0022] Furthermore, the invention also relates, according to another of its aspects, to a turbomachine comprising a bladed disc as defined previously. BRIEF DESCRIPTION OF THE FIGURES

[0023] Other advantages, aims and particular characteristics of the invention will emerge from the following non-limiting description of at least one embodiment of the present invention, with reference to the appended figures, in which: • [Fig.l] schematically represents in section an example of a turbomachine in accordance with the invention, • [Fig.2] is a schematic view along direction II of the fan of the turbomachine of [Fig.l], • [Fig.3] schematically represents in section an example of a foot fan blade positioned in a groove of the fan disc with the presence of a shim slipped under the blade root, and • [Fig.4] schematically represents in perspective an example of fan blade foot equipped with a positioning device according to the invention.

[0024] Throughout these figures, identical references may designate identical or similar elements.

[0025] Furthermore, the different parts shown in the figures are not necessarily shown on a uniform scale, in order to make the figures more readable. DETAILED DESCRIPTION OF THE INVENTION

[0026] Throughout the description, given as a non-limiting example of embodiment, it is noted that the terms upstream and downstream are to be considered with respect to a main direction F of normal flow of the gases (from upstream to downstream) for a turbomachine 1. Furthermore, the axis X of the turbomachine 1 is called the axis of radial symmetry of the turbomachine 1. The axial direction of the turbomachine 1 corresponds to the axis of rotation X of the turbomachine 1. A radial direction of the turbomachine 1 is a direction perpendicular to the axis X of the turbomachine 1.

[0027] Furthermore, unless otherwise specified, the adjectives and adverbs axial, radial, axially and radially are used with reference to the aforementioned axial and radial directions. Furthermore, unless otherwise specified, the terms inner and outer are used with reference to a radial direction so that the inner part of an element is closer to the X axis of the turbomachine 1 than the outer part of the same element.

[0028] With reference to [Fig.l], a turbomachine 1 according to the invention of the double-flow turbojet type centered on an axis X is shown schematically in longitudinal section. It comprises from upstream to downstream: a fan 2, a low-pressure compressor 3, a high-pressure compressor 4, a combustion chamber 5, a high-pressure turbine 6 and a low-pressure turbine 7.

[0029] [Fig. 2] represents a schematic view of the fan 2 of [Fig. 1] according to the direction IL. The fan 2 comprises a fan disc 22 in which a plurality of grooves 24, or cells, are made at the level of its periphery ex These grooves 24 are for example rectilinear and extend axially from upstream to downstream along the entire length of the disc 22. They are also regularly distributed all around the axis X of the disc 22. In this way, each groove 24 defines with its neighbor a tooth 25 which also extends axially from upstream to downstream along the entire length of the disc 22. Equivalently, a groove 24 is delimited between two neighboring teeth 25.

[0030] The fan 2 further comprises a plurality of blades 26 of curvilinear profile, only four blades 26 being shown in [Fig. 2]. Each blade 26 has a root 26a which is mounted in a respective groove 24 of the fan disc 22. For this purpose, the root 26a may have a fir tree or dovetail shape adapted to the geometry of the grooves 24.

[0031] [Fig. 3] also represents the known insertion of a blocking wedge 23 under the foot 26a, in the shape of a bulb or dovetail, of a fan blade 26, in the groove 24.

[0032] In order to ensure the proper functioning of the turbomachine 1, the blades 26 must be correctly positioned during assembly in the grooves 24 of the fan disk 22. In particular, the mauling surfaces 26b of the roots 26a of the blades 26 and the mauling surfaces 24b of the grooves 24 must be in perfect contact during assembly.

[0033] However, as deliberately exaggeratedly shown in dotted lines in [Fig. 3], it may happen that the assembly, generally manual, is poorly carried out and that the root 26a of the blade 26 is positioned at an angle in the groove 24 so that its poor assembly impacts the behavior of the blade 26 during operation of the turbomachine 1.

[0034] Advantageously, as shown in [Fig. 4], a device 40 for positioning the blade 26 in the groove 24 is present on at least one of a first contact surface 26b of the blade root 26a and a second contact surface 24b of the groove 24.

[0035] In the example shown here in [Fig. 4], the positioning aid device 40 is located mainly on a root mauling surface 26b and a portion of this positioning device 40 is also located on a front surface 26c of the blade root 26a, transverse to the axis of rotation X of the bladed disc 2. However, it could be otherwise, and in particular the positioning device 40 could be present mainly on a groove mauling surface 24b and on a front surface of the disc 22. Also, each root mauling surface 26b and / or groove 24b could comprise such a positioning aid device 40.

[0036] The positioning assistance device 40 comprises an electrical circuit of variable conductivity depending on the nature of the contact between the first contact surface 26b and the second contact surface 24b, here therefore between the matting surface of foot 26b and the groove matting range 24b. Advantageously, this electrical circuit is insulated in contact with the surface on which it is positioned.

[0037] The electrical circuit may in particular be a flexible printed electrical circuit, for example a self-adhesive graphite track, which covers the surface of the matting surface 26b.

[0038] This electrical circuit advantageously comprises at least two nested conductive patterns 41 and 42 between which an electrical conductivity is established in contact with a conductive metal surface, the conductivity increasing with the metal surface in contact with the electrical circuit. Thus, when the surface of the matting surface 26b comes into contact with the surface of the matting surface 24b, there is electrical conduction between the two patterns 41 and 42 of the electrical circuit of the positioning assistance device 40 and the electrical conductivity increases with the metal surface in contact with the electrical circuit.

[0039] Furthermore, each conductive pattern 41, 42 comprises a connection terminal 41a, 42a to a conductivity measuring device, for example an ohmmeter, which is located on a surface accessible by an operator during assembly, for example here the front surface 26c of the blade root 26a, transverse to the axis of rotation X of the bladed disc 2.

[0040] During assembly, the operator can therefore connect an ohmmeter to the terminals 41a, 42a of the electrical circuit so as to access a measurement of the electrical conductivity resulting from the contact between the blade root 26a and the groove 24. This measurement advantageously makes it possible to judge the quality of the contact thus made and therefore the correct positioning of the blade root 26a in the groove 24. Indeed, by positioning the blade 26, the operator will seek to maximize the value of the electrical conductivity.

[0041] For this, a possible calibration step can be carried out by first placing a metallic element, such as a piece of metal of the same nature as the metal of the groove 24, in contact with the electrical circuit to define a target electrical conductivity value to be achieved during assembly.

[0042] After assembly, it is possible to lock the blade 26 in position by sliding a shim 23 under the blade root 26a. Advantageously, the positioning aid device 40 thus placed on the blade root 26a remains discreet and can be left in place without affecting the operation of the turbomachine 1.

[0043] Of course, the invention is not limited to the embodiments which have just been described. Various modifications can be made thereto by those skilled in the art.

[0044] In particular, although the invention has been described with reference to a fan disc 22, it is applicable to any type of rotating disc to the periphery of which moving blades are fixed.

Claims

Claims

1. A bladed disc (2) of a turbomachine (1) comprising a disc (22), provided with at least one groove (24) made at the periphery of the disc (22), and at least one blade (26) comprising a blade root (26a) housed in a groove (24) of the disc (22), the blade root (26a) comprising a first contact surface (26b) and the groove (24) comprising a second contact surface (24b), characterized in that at least one of the first contact surface (26b) and the second contact surface (24b) comprises at least partially a device (40) for assisting the positioning of the root (26a) in the groove (24), comprising an electrical circuit of variable conductivity depending on the nature of the contact between the first contact surface (26b) and the second contact surface (24b).

2. A bladed disc (2) according to claim 1, wherein the first contact surface (26b) of the blade root (26a) is a root mauling surface (26b) extending substantially longitudinally along the axis of rotation (X) of the bladed disc (2), and wherein the second contact surface (24b) of the groove (24) is a groove mauling surface (24b) extending substantially longitudinally along the axis of rotation (X) of the bladed disc (2).

3. A bladed disc (2) according to claim 1 or 2, wherein the electrical circuit is a flexible printed electrical circuit fixed to at least one of the first contact surface (26b) and the second contact surface (24b), in particular by gluing.

4. Bladed disc (2) according to one of the preceding claims, in which the electrical circuit comprises at least two nested conductive patterns (41, 42) between which an electrical conductivity is established in contact with a conductive metal surface, the conductivity increasing with the metal surface in contact with the electrical circuit.

5. Bladed disc (2) according to claim 4, in which each conductive pattern (41, 42) comprises a connection terminal (41a, 42a) to a conductivity measuring device, in particular an ohmmeter, in particular located on a surface of the blade root (26a) and / or the disc (22) accessible by an operator, for example a front surface (26c) of the blade root (26a) and / or the disc (22), substantially transverse to the axis of rotation (X) of the bladed disc (2).

6. A bladed disc (2) according to any one of the preceding claims preceding, in which the positioning aid device (40) is located on a root bearing surface (26b) and on a front surface (26c) of the blade root (26a), substantially transverse to the axis of rotation (X) of the bladed disc (2).

7. A bladed disc (2) according to any preceding claim, wherein the bladed disc (2) comprises a fan (2).

8. Method for assisting in positioning in a groove (24) a blade root (26a) of a blade (26) of a bladed disc (2) according to any one of the preceding claims, comprising the steps of: - positioning the blade root (26a) in a groove (24) of the disc (22), - measuring the electrical conductivity at the positioning aid device (40), in particular by means of an ohmmeter, - orienting the blade root (26a) in the groove (24) so ​​as to obtain a maximum value of the electrical conductivity measured at the positioning aid device (40), - optionally, positioning a shim (23) in the groove (24) under the blade root (26a).

9. The method of claim 8, wherein the maximum value of the electrical conductivity measured at the positioning aid device (40) is predetermined by means of a calibration step of placing a metallic element in contact with the electrical circuit to define a target conductivity to be achieved during assembly.

10. Turbomachine (1) comprising a bladed disc (2) according to any one of claims 1 to 7.

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