Protection element for a compressor drum and method of repairing a compressor drum

Abstract

The present invention relates to a protection element (45.1, 45.2) for a compressor drum (20), which is intended to be arranged at least in part between a blade root (25) and the compressor drum (20), comprising: - a first lateral wall (51.1, 51.2) comprising an inner portion (54.1, 54.2) intended to cover an inner rounded portion of a pocket (24), a bearing surface portion (55.1, 55.2) intended to cover a blade root bearing surface of the pocket (24), and an outer portion (56.1, 56.2) intended to cover an outer rounded portion of the compressor drum (20), - a connecting wall (53.1, 53.2) intended to cover an outer face of the compressor drum (20), and - a second lateral wall (52.1, 52.2) comprising a projecting portion (57.1, 57.2) intended to engage with a mounting groove (46.1, 46.2) formed in a vertical face of the compressor drum (20).

Description

[0001] The present invention relates to a protective element for a low-pressure turbomachine compressor drum. More specifically, the invention relates to a protective element for a compressor drum and a method for repairing a compressor drum. The invention finds a particularly advantageous application for repairing a used low-pressure compressor drum. However, the invention can also be implemented at the end of production with a new low-pressure compressor drum.

[0002] The operating principle of a turbomachine fan is to compress the air entering the engine. A large portion of this air constitutes the secondary flow, and the remainder constitutes the primary flow. The latter passes through a low-pressure compressor attached to the fan, a high-pressure compressor, the combustion chamber, the high-pressure turbine, and finally, the low-pressure turbine before being expelled.

[0003] The compression achieved by the blower occurs in two phases. In the first phase, a moving blade accelerates the air particles by deflecting them relative to the engine axis. The moving blade consists of a plurality of blades mounted on a cylindrical hub called a "fan disc," which is driven in rotation by the low-pressure turbine.

[0004] In a second phase, a fixed vane slows down the air particles and converts some of their speed into pressure. This fixed vane is called an OGV (for "Outlet Guide Vane") or "straightener" because it directs the airflow, accelerated by the moving vane, back into line with the engine.

[0005] The same principle is applied by the low-pressure compressor located downstream of the blower. The low-pressure compressor consists of moving blades mounted on a cylindrical component called the compressor drum, as well as stators made up of fixed blades. Depending on the turbomachine, low-pressure compressors can have 3 to 5 stages, each compressor stage comprising a rotating blade wheel and a corresponding grid of stators.

[0006] As illustrated by the figure 1 For each stage of the low-pressure compressor, the movable vanes 1 are installed in a corresponding cavity 2 of the compressor drum 4 via an infeed window 3 according to the following steps: i - A first blade 1 is inserted into the cavity 2 through the insertion window 3, following arrow F1. ii - Once blade 1 is inserted, it is shifted tangentially along arrow F2 by sliding it into the cavity 2 to free the insertion window 3. The first blade 1 is now installed. iii - The next blade can then be inserted, and the operation repeated until all the blades 1 are installed inside the cavity 2.

[0007] When the turbomachine, and therefore the compressor drum 4, is rotated, the movable blades 1 are held radially by the bearing surfaces 5 of the cavity 2, as illustrated by the figure 2 . Such an assembly of the moving blades 1 in a cell 2 of compressor drum 4 is a classic and proven installation of the state of the art.

[0008] However, micro-displacements of the blades 1 inside the cell 2 at the point of a contact surface between the spans 6 of the blade feet 7 and the spans 5 of the cell 2 can locally wear down said spans 5 of the cell 2.

[0009] This wear is represented by the discontinuous lines on the figure 2 This is likely to reduce the radial clearances above the moving blades 1, which creates a risk of uncontrolled penetration of the moving blades 1 into the abradable seals. Wear may also create axial misalignments of the moving blades 1 that could interfere with the fixed blades. Furthermore, positional deviations between the moving blades 1 affect the balance of the compressor drum 4.

[0010] The mounting of moving blades 1 on a worn compressor drum 4 may also be affected, insofar as there is a risk that a moving blade 1 may be straddling an unworn part and a worn part of the bearing surfaces 5 of the compressor drum 4.

[0011] Significant wear may also impair the mechanical integrity of the low-pressure compressor drum 4, which may break during operation.

[0012] Document GB630357 describes a compressor drum in which the blades are fitted with dovetail-shaped blade feet dimensioned to act as spacers and engaging in an undercut annular groove within a support ring. A protective element is intended to be positioned inside the annular groove.

[0013] Document FR2981132 describes a turbomachine assembly in which a shim is adapted to primarily cover one of the disc's bulbs and to be held radially with respect to the disc by said disc bulb and the blade cavity adapted to cooperate with it. The disc bulb has at least one longitudinal cavity adapted to form, with said shim, a channel for the passage of a secondary cooling airflow.

[0014] The invention aims to effectively remedy the aforementioned drawbacks.

[0015] The invention is as defined in independent claims 1 and 10.

[0016] The invention thus makes it possible to restore the contact interface between the drum cavity bearing surfaces and the moving blades. The invention therefore allows the moving blades to be installed in the compressor drum in the same position as on a new drum fresh from the factory.

[0017] According to one embodiment of the invention, the connecting wall is elastically deformable so as to allow mounting of the protective element on the compressor drum.

[0018] According to one embodiment of the invention, said protective element includes a recess intended to be positioned opposite a portion of a blade introduction window made in the compressor drum.

[0019] According to one embodiment of the invention, said protective element comprises at least one recess intended to be positioned opposite a portion of a blade lock insertion window.

[0020] According to one embodiment of the invention, the connecting wall includes at least one opening for the passage of a protruding portion of a passage zone of a sealing joint.

[0021] According to one embodiment of the invention, said protective element consists of a folded sheet metal having a thickness between 0.2mm and 0.4mm.

[0022] According to one embodiment of the invention, said protective element is made of a nickel-based metallic material.

[0023] According to one embodiment of the invention, the bearing portion is covered by a layer of lubricating varnish.

[0024] According to one embodiment of the invention, a tangential length of the protection element is greater than a tangential length of one blade platform and less than or equal to a tangential length of five blade platforms.

[0025] The invention also relates to a method for repairing a compressor drum comprising: a machining step intended to remove wear on compressor drum bearing surfaces in order to define a cavity having upstream and downstream bearing surfaces having regular surfaces, a machining step of two mounting grooves respectively upstream and downstream of the cavity, and a step of installing an upstream protective element and a downstream protective element such that the protective elements cooperate respectively with a corresponding mounting groove made in the compressor drum and cover the upstream and downstream bearing surfaces of the cavity.

[0026] According to one embodiment of the invention, said method further comprises a machining step of a passage zone of a sealing joint so as to present an alternation of protruding portions and flat portions to facilitate the installation of a protective element on the compressor drum.

[0027] According to one embodiment of the invention, each protective element is installed by applying a radial force to the protective element, such that a bonding wall of the protective element is deformed to allow a protruding portion of each protective element to cooperate with a corresponding mounting groove before resuming its original flat shape so as to cover a corresponding external face of the compressor drum.

[0028] According to one embodiment of the invention, said method further comprises a machining step of external faces of the compressor drum located respectively upstream and downstream of the cell.

[0029] The present invention will be better understood and other features and advantages will become apparent upon reading the following detailed description, which includes embodiments given by way of illustration with reference to the accompanying figures, presented by way of non-limiting examples, which may serve to complete the understanding of the present invention and the explanation of its implementation and, where appropriate, contribute to its definition, on which: [ Fig. 1 ] There figure 1 , already described, is a perspective view illustrating the mounting of the blades inside a low-pressure compressor drum cell; Fig. 2 ] There figure 2 , already described, is a cross-sectional view of a compressor drum cell illustrating the wear of the bearing surfaces by the blade root; Fig. 3 ] There figure 3 is a longitudinal cross-sectional view of the front part of a turbomachine; [ Fig. 4 ] There figure 4 is a perspective view of a low-pressure compressor drum on which the repair process according to the invention is implemented; [ Fig. 5 ] There figure 5 is a cross-sectional view of a cell in the low-pressure compressor drum on which the repair process according to the invention is implemented; [ Fig. 6a ] There figure 6a is a partial perspective view of a compressor drum cell after a machining step of the repair process according to the invention; [ Fig. 6b ] There figure 6b is a detailed perspective view of the alveolus of the figure 6a highlighting the machining of a groove for receiving a sealing gasket; [ Fig. 7a ] There figure 7a is a perspective view of an upstream protective element for a compressor drum according to the invention having a standard configuration; [ Fig. 7b ] There figure 7b is a perspective view of a downstream protection element for a compressor drum according to the invention having a standard configuration; [ Fig. 8a ] There figure 8a is a perspective view of an upstream protective element for a compressor drum according to the invention having a "lock" type configuration; [ Fig. 8b ] There figure 8b is a perspective view of a downstream protection element for a compressor drum according to the invention having a "lock" type configuration; [ Fig. 9 ] There figure 9 shows the different stages of installing a protective element according to the invention inside a cell of a low-pressure compressor drum; [ Fig. 10 ] There figure 10 is a perspective view of a cell in a low-pressure compressor drum in which protective elements according to the invention have been installed; [ Fig. 11 ] There figure 11 is a perspective view illustrating the positioning of the upstream and downstream protection elements according to the invention between the bearing surfaces of a blade and the bearing surfaces of a low pressure compressor drum cell.

[0030] It should be noted that, on the figures 3 à 11 The structural and / or functional elements common to the different embodiments have the same references. Thus, unless otherwise stated, such elements have identical structural, dimensional and material properties.

[0031] In the following description the terms "internal" and "external" are understood by reference to a radial direction with respect to the X1 axis of the compressor drum, i.e. an "internal" face is a radially internal face while an "external" face is a radially external face, such that the internal face is closer to the X1 axis of the drum than the external face.

[0032] There figure 3 This shows the front part of a turbomachine 10 comprising a fan 11 equipped with a movable blade 12 designed to accelerate air particles by deflecting them relative to the engine axis. The movable blade 12 comprises a plurality of blades 13 mounted on a cylindrical hub 14 called a "fan disc" driven in rotation by the low-pressure turbine.

[0033] A fixed blade 15 located downstream of the moving blade 12 slows down the air particles and transforms part of their speed into pressure. This fixed blade 15 is called an OGV (for "Outlet Guide vane") or "straightener" because it returns the airflow, accelerated by the moving blade 12, to the axis of the engine.

[0034] A low-pressure compressor 18 comprises moving blades 19 mounted on a cylindrical part called the low-pressure compressor drum 20, as well as stators 21 consisting of fixed blades. Depending on the configuration of the turbomachine 10, the low-pressure compressor 18 can have 3 to 5 stages, each compressor stage consisting of a wheel of moving blades 19 and a corresponding grid of stators 21.

[0035] The 20-axis X1 compressor drum shown on the figure 4 presents a cylindrical shape. The compressor drum 20 has a plurality of cells 24 corresponding to the number of stages of the low-pressure compressor 18. Each cell 24 is a circumferential groove extending along a circumference of the drum 20 and intended to receive blade feet 25, such that the blades 19 are angularly spaced regularly along a circumference of the compressor drum 20. The compressor drum 20 has a mounting interface 22 with the hub 14 of the blower.

[0036] As can be seen on the figure 5 A cell 24 is delimited by an upstream blade root bearing 26.1 against which a correspondingly shaped blade root bearing 25 abuts, an upstream internal rounded portion 27.1, a cell bottom 28, a downstream internal rounded portion 27.2, and a downstream blade root bearing 26.2 against which a correspondingly shaped downstream blade root bearing 26.2 abuts. In cross-sectional view, the upstream blade root bearings 26.1 and downstream blade root bearings 26.2 form an angle θ with respect to the cell bottom 28, so that the cell 24 has an overall trapezoidal shape complementary to that of a blade root 25. This ensures radial retention of the blades 19 when the compressor drum 20 is rotating.

[0037] An upstream external rounded portion 29.1 and a downstream external rounded portion 29.2 are located respectively in an extension of the upstream 26.1 and downstream 26.2 blade foot span of the corresponding cell 24.

[0038] The compressor drum 20 also has an upstream external face 30.1 and a downstream external face 30.2. The external faces 30.1, 30.2 have an annular shape with axial orientation relative to the axis X1. The external faces 30.1, 30.2 are located radially towards the outside of the compressor drum 20 with respect to the axis X1.

[0039] An upstream vertical face 31.1 and a downstream vertical face 31.2 each extend in a radial plane with respect to the axis X1 of the compressor drum 20. Each vertical face (upstream 31.1 respectively downstream 31.2) is located on the opposite side of the corresponding face comprising the external rounded portion (upstream 29.1 respectively downstream 29.2), the blade foot span (upstream 26.1 respectively downstream 26.2), and the internal rounded portion (upstream 27.1 respectively downstream 27.2).

[0040] The upstream vertical face 31.1, the upstream external face 30.1, the upstream external rounded portion 29.1, the upstream blade foot span 26.1, and the upstream internal rounded portion 27.1 are made in an upstream wall 35.1 of the cell 24. The downstream vertical face 31.2, the downstream external face 30.2, the downstream external rounded portion 29.2, the downstream blade foot span 26.2, and the downstream internal rounded portion 27.2 are made in a downstream wall 35.2 of the cell 24.

[0041] As can be seen on the figures 6a And 6b , the compressor drum 20 further includes a blade foot 25 inlet window 36 and two blade lock inlet windows 37 arranged on either side of the blade foot 25 inlet window 36.

[0042] Furthermore, a passage zone 40 for a sealing gasket is defined by two circumferential walls 41 extending from the outer face 30.1, between which a groove 42 for receiving the sealing gasket (not shown) extends. In the example shown, the sealing gasket is intended to be positioned upstream of the cell 24. However, depending on the stage of the low-pressure compressor 18, the sealing gasket may be installed upstream or downstream of the cell 24.

[0043] A repair procedure for a used low-pressure compressor drum 20 is described below.

[0044] A machining step is performed on the drum 20 to eliminate wear on the bearing surfaces 26.1, 26.2 of the compressor drum 20, thereby defining a cavity 24 with upstream bearing surfaces 26.1 and downstream bearing surfaces 26.2 having regular surfaces. The machining is preferably carried out so that the cavity 24 has an axisymmetric configuration, excluding the blade or locking inlet windows 36, 34.

[0045] A machining step is also performed on the compressor drum 20 to allow the installation of the protective elements 45.1, 45.2 described in more detail below. Following this operation, two mounting grooves 46.1, 46.2 are made respectively upstream and downstream of the cavity 24 in the upstream vertical face 31.1 and in the downstream vertical face 31.2.

[0046] In addition, the upstream external faces 30.1 and downstream external faces 30.2 of the low-pressure compressor drum 20 are machined to obtain regular surfaces. In particular, the passage area 40 of the sealing gasket is machined to form an alternation of projecting portions 48 and flat portions 49 to facilitate the installation of a protective element 45.1, 45.2 on the low-pressure compressor drum 20.

[0047] Once the machining steps are completed, an upstream protective element 45.1 and a downstream protective element 45.2 are installed in such a way that the protective elements 45.1, 45.2 cooperate respectively with a corresponding mounting groove 46.1, 46.2 made in the drum 20 and respectively cover the upstream bearing surface 26.1 and the downstream bearing surface 26.2 of the cavity 24.

[0048] The protective elements 45.1, 45.2 thus fill the gap between the bearing surfaces of the moving blade 19 and the bearing surfaces of the cavity 24 of the compressor drum 20, as shown in the figure 11 .

[0049] More specifically, each protective element 45.1, 45.2 (upstream or downstream) is intended to be disposed at least in part between a blade foot 25 and the compressor drum 20.

[0050] Following a standard upstream geometry represented on the figure 7a and 12, the upstream protection element 45.1 also called "upstream flashing" includes a first upstream side wall 51.1, a second upstream side wall 52.1 and an upstream connecting wall 53.1 ensuring the connection between the first upstream side wall 51.1 and the second upstream side wall 52.1.

[0051] The first upstream side wall 51.1 comprises an upstream internal portion 54.1 intended to cover the upstream internal rounded portion 27.1 of a cell 24, an upstream span portion 55.1 intended to cover an upstream blade foot span 26.1 of the cell 24 and an upstream external portion 56.1 intended to cover an upstream external rounded portion 29.1 of the drum located in an extension of the upstream blade foot span 26.1. The upstream span portion 55.1 forms a non-zero angle with respect to the upstream connecting wall 53.1.

[0052] The upstream connecting wall 53.1 is designed to cover the upstream external face 30.1 of the compressor drum 20. The upstream connecting wall 53.1 has a flat shape. The upstream connecting wall 53.1 is elastically deformable to allow mounting of the upstream protective element 45.1 on the compressor drum 20. The upstream connecting wall 53.1 has at least one opening 60 for the passage of a projecting portion 48 of the seal passage area 40. The number of passage openings depends on the configuration of the seal passage area 40 at the location where the upstream protective element 45.1 is positioned.

[0053] The second upstream side wall 52.1 has a projecting upstream portion 57.1 designed to cooperate with the upstream mounting groove 46.1 formed in a vertical upstream face 31.1 of the drum. The projecting upstream portion 57.1 extends inwards towards the upstream protective element 45.1. The second upstream side wall 52.1 has an S-shape. The upstream protective element 45.1 has axisymmetry at the level of the recess 24.

[0054] Similarly, following a standard downstream geometry represented on the figures 7b And 11 , the downstream protection element 45.2 comprises a first downstream side wall 51.2, a second downstream side wall 52.2 and a downstream connecting wall 53.2 ensuring the connection between the first downstream side wall 51.2 and the second downstream side wall 52.2.

[0055] The first downstream side wall 51.2 comprises an internal downstream portion 54.2 intended to cover the internal downstream rounded portion 27.2 of a cell 24, a downstream span portion 55.2 intended to cover a downstream blade foot span 26.2 of a cell 24 and an external downstream portion 56.2 intended to cover the external downstream rounded portion 29.2 of the drum 20 located in an extension of the downstream blade foot span 26.2. The downstream span portion 55.2 forms a non-zero angle with respect to the downstream connecting wall 53.2.

[0056] The downstream connecting wall 53.2 is designed to cover the downstream outer face 30.2 of the compressor drum 20. The downstream connecting wall 53.2 has a flat shape. The downstream connecting wall 53.2 is elastically deformable to allow the downstream protective element 45.2 to be mounted on the compressor drum 20.

[0057] The second downstream side wall 52.2 has a downstream projecting portion 57.2 intended to cooperate with the downstream mounting groove 46.2 formed in the downstream vertical face 31.2 of the drum 20. The downstream projecting portion 57.2 extends inwards towards the downstream protective element 45.2. The second downstream side wall 52.2 has an S-shape. The downstream protective element 45.2 has axisymmetry at the level of the recess 24.

[0058] Following a lock-type geometry shown on the figure 8a The upstream protection element 45.1 includes an upstream recess 63.1 intended to be positioned opposite an upstream portion of a blade inlet window 36 made in the low-pressure compressor drum 20. The upstream recess 63.1 is made in the upstream external portion 56.1 and in the upstream connecting wall 53.1 of the upstream protection element 45.1. The upstream protection element 45.1 also includes recesses 64.1 intended to be positioned opposite a portion of a blade lock inlet window 37.

[0059] Similarly, following a lock-type geometry shown on the figure 8b The downstream protection element 45.2 includes a downstream recess 63.2 intended to be positioned opposite a downstream portion of a blade inlet window 36 made in the compressor drum 20. The downstream recess 63.2 is made in the downstream external portion 56.2 and in the downstream connecting wall 53.2 of the downstream protection element 45.2. The downstream protection element 45.2 also includes recesses 64.2 intended to be positioned opposite a portion of a blade lock inlet window 37.

[0060] Preferably, each protective element 45.1, 45.2 is made of a folded sheet metal piece with a thickness between 0.2 mm and 0.4 mm. The thickness of the sheet metal can be adapted to the repair requirements to compensate for the level of wear on the cavity 24. The thin sheet metal is sufficiently deformable to allow the protective element 45.1, 45.2 to conform to the shape of the machined cavity 24.

[0061] Each protective element 45.1, 45.2 is made of a nickel-based metallic material, specifically Inconel (registered trademark). This material offers superior wear resistance to titanium and allows for the production of thin parts sufficiently rigid to withstand the stresses of wear at the interface between the moving blades 19 and the compressor drum 20.

[0062] The bearing surface 55.1, 55.2 can be coated with a layer of lubricating varnish. This improves the contact conditions between a moving blade 19 and the corresponding bearing surface 26.1, 26.2 of the cavity 24 to maximize the service life of the compressor drum 20.

[0063] Preferably, a tangential dimension of the protective element 45.1, 45.2 is such that several movable blades 19, particularly between 1 and 5, can be in contact with it. Advantageously, a tangential length of the protective element 45.1, 45.2 is greater than the tangential length of a blade platform 65 in order to prevent the spans of a blade 19 from coming into contact with two neighboring protective elements 45.1, 45.2, which would cause a discontinuity of contact between the movable blade 19 and the compressor drum 20.

[0064] Furthermore, the tangential length of the protective element 45.1, 45.2 is less than or equal to a tangential length of five blade platforms 65 in order to allow deformation of the protective element 45.1, 45.2 for its mounting on the compressor drum 20. Indeed, a greater length of the protective element 45.1, 45.2 would increase its rigidity which would prevent obtaining the deformation necessary for its mounting on the compressor drum 20.

[0065] The following is described, with reference to the figure 9 , the different assembly steps of the protective element 45.1. The steps are identical with the protective element 45.2 except for the direction of assembly.

[0066] As illustrated by the left view, the protective element 45.1 is positioned along arrow F1, such that the internal portion 54.1 and the bearing portion 55.1 are respectively opposite the internal rounded portion 27.1 and the bearing portion 26.1 of a cell 24. The connecting wall 53.1 has a flat shape before its assembly.

[0067] As illustrated by the central view, a radial force is applied to the protective element 45.1, such that the connecting wall 53.1 is deformed to allow the protruding portion 57.1 of the protective element 45.1 to cooperate with the mounting groove 46.1.

[0068] As illustrated by the view on the right, the connecting wall 53.1 then returns to its original flat shape so as to cover the external face 30.1 of the compressor drum 20. Thus, the upstream protective element 45.1 or downstream 45.2 is held respectively around an upstream wall 35.1 or downstream wall 35.2 of a cell 24.

[0069] As illustrated by the figure 10 A plurality of upstream protective elements 45.1 are arranged edge to edge to follow the circumference of an upstream wall 35.1 of the drum cavity 24. Similarly, a plurality of downstream protective elements 45.2 are arranged edge to edge to follow the circumference of a downstream wall 35.2 of the drum cavity 24. The geometry of the protective element 45.1, 45.2 (standard or locking) is adapted according to the configuration of the cavity 24 within the area where the protective element 45.1, 45.2 is installed.

[0070] The blades 19 can then be installed inside the cavity 24 via the introduction window 36, following the method previously described with reference to the figure 1 Blade locks are then put in place via the windows 37 to prevent the blades 19 from moving inside the cell 24.

[0071] The invention also relates to the assembly formed by a protective element 45.1, 45.2 and the compressor drum 20.

[0072] Of course, the different features, variants and / or embodiments of the present invention can be combined with each other in various ways as long as they are not incompatible or mutually exclusive.

[0073] Furthermore, the invention is defined by the claims, but is not limited to the embodiments described above and provided solely by way of example. It encompasses various modifications, alternative forms, and other variations that a person skilled in the art might consider within the scope of the present invention, and in particular all combinations of the different modes of operation described above, which may be taken separately or in combination.

Claims

1. A protective element (45.1, 45.2) for a compressor drum (20) to be disposed at least partially between a blade foot (25) and the compressor drum (20), the compressor drum (20) having at least one cell (24) which is a circumferential groove extending along a circumference of the compressor drum (20) for receiving blade feet (25), the protective element (45.1, 45.2) including: - a first lateral wall (51.1, 51.2) including an internal portion (54.1, 54.2) for covering an internal rounded portion (27.1, 27.2) of a cell (24) in the compressor drum (20), a bearing area portion (55.1, 55.2) for covering a blade foot bearing area (26.1, 26.2) of the cell (24), and an external portion (56.1, 56.2) for covering an external rounded portion (29.1, 29.2) of the compressor drum (20), - a connecting wall (53.1, 53.2) for covering an external face (30.1, 30.2) of the compressor drum (20), and - a second lateral wall (52.1, 52.2) including a projecting portion (57.1, 57.2), characterized in that the projecting portion (57.1, 57.2) of the second side wall (52.1, 52.2) is provided for cooperating with a mounting groove (46.1, 46.2) made in a vertical face (31.1, 31.2) extending in a radial plane with respect to the axis (X1) of the compressor drum (20).

2. The protective element according to claim 1, characterized in that the connecting wall (53.1, 53.2) is elastically deformable so as to allow the protective element (45.1, 45.2) to be mounted on the compressor drum (20).

3. The protective element according to claim 1 or 2, characterized in that it includes a recess (63.1, 63.2) to be arranged opposite a portion of a blade introduction window (36) in the compressor drum (20).

4. The protective element according to any one of the claims 1 to 3, characterized in that it includes at least one recess (64.1, 64.2) to be arranged opposite a portion of a blade lock introduction window (37).

5. The protective element according to any one of the claims 1 to 4, characterized in that the connecting wall (53.1, 53.2) includes at least one opening (60) for the passage of a protruding portion (48) of a passage zone (40) of a sealing joint.

6. The protective element according to any one of the claims 1 to 5, characterized in that it is formed by a folded sheet metal with a thickness between 0.2mm and 0.4mm.

7. The protective element according to any one of the claims 1 to 6, characterized in that it is made from a nickel-based metallic material.

8. The protective element according to any one of the claims 1 to 7, characterized in that the bearing area portion (55.1, 55.2) is covered by a layer of lubricating varnish.

9. The protective element according to any one of the claims 1 to 8, characterized in that a tangential length of the protective element (45.1, 45.2) is superior to a tangential length of one blade platform (65) and inferior or equal to a tangential length of five blade platforms (65).

10. A method for repairing a compressor drum (20) including at least one cell (24) which is a circumferential groove extending along a circumference of the compressor drum (20) for receiving blade feet (25), characterized in that said method includes: - a machining step for removing wear on bearing areas (26.1, 26.2) of the compressor drum (20) in order to define a cell (24) having upstream and downstream bearing areas (26.1, 26.2) with regular surfaces, - a machining step of two mounting grooves (46.1, 46.2) respectively in two upstream and downstream vertical faces (31.1, 31.2), each extending in a radial plane with respect to the axis (X1) of the compressor drum (20), respectively upstream and downstream of the cell (24), and - an installation step for an upstream protective element (45.1) and a downstream protective element (45.2) such that the protective elements (45.1, 45.2) cooperate respectively with a corresponding mounting groove (46.1, 46.2) in the compressor drum (20) and cover the upstream and downstream bearing areas (26.1, 26.2) of the cell (24).

11. The method according to claim 10, characterized in that it further includes a machining step for a passage zone (40) for a sealing joint so as to present an alternation of protruding portions (48) and flat portions (49) to facilitate an installation of a protective element (45.1, 45.2) on the compressor drum (20).

12. The method according to Claim 10 or 11, characterized in that each protective element (45.1, 45.2) is installed by applying a radial force to the protective element (45.1, 45.2), such that a connecting wall (53.1, 53.2) of the protective element (45.1, 45.2) is deformed to allow a protruding portion (57.1, 57.2) of each protective element (45.1, 45.2) to cooperate with a corresponding mounting groove (46.1, 46.2) before resuming its initial flat shape so as to cover a corresponding external face (30.1, 30.2) of the compressor drum (20).

13. The method according to any one of the claims 10 to 12, characterized in that it further comprises a machining step of external faces (30.1, 30.2) of the compressor drum (20) respectively upstream and downstream of the cell (24).

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