METHOD FOR REPAIRING AN END PLATE OF A TURBOMACH ROTOR

Description

TECHNICAL FIELD

[0001] The invention relates to the repair of a flange of a turbomachine rotor, such as a turbojet fan disc flange. STATE OF THE PRIOR ART

[0002] In a turbojet engine, marked 1 in the figure 1 , air is admitted into an inlet sleeve 2 to pass through a blower comprising a series of rotating blades 3 before splitting into a central primary flow and a secondary flow surrounding the primary flow.

[0003] The primary flow is compressed by low pressure 4 and high pressure 5 compressors before reaching a combustion chamber 6, after which it expands by passing through a high pressure turbine 7 and a low pressure turbine 8, before being evacuated, generating auxiliary thrust. The secondary flow is propelled directly by the fan to generate main thrust.

[0004] As visible on the figure 2, the fan 3 of such a turbojet engine comprises a disk 9 forming part of a rotor rotating around a longitudinal axis AX, and which carries a set of blades regularly distributed around its circumference, such as the blade 10.

[0005] This disc 9 comprises an upstream flange 11 carrying on the one hand balancing weights 12, and on the other hand a flange 13 ensuring axial locking of the blades. The flange 13 is fixed to the flange by means of screws engaged in nuts crimped into the upstream flange 11, while the weights are fixed to this flange by riveting.

[0006] Document FR 3 084 697 A1 describes a crown of a turbomachine rotor flange with flange fixing holes and weight fixing holes. Each weight fixing hole is equipped with a crimped nut.

[0007] Document FR 3 001 515 A1 describes a crown of a turbomachine rotor flange with flange fixing holes and weight fixing holes.

[0008] During maintenance operations, it can happen that the disassembly of the weights leads to local damage to the flange that carries them, because fixing these weights to the flange by riveting is problematic to separate them from it. The flange or crown also has a local low thickness at the level of the weights, so as to facilitate their fixing by riveting, which increases the risk of damage during disassembly during which significant forces can be exerted.

[0009] Deterioration can result in degradation of the riveting holes making them unusable, and in local deformation of the wall constituting the flange.

[0010] In such a case, it is necessary to replace the entire disc, since it is a complex alloy part, so it is not possible to consider reworking such a part.

[0011] The aim of the invention is to provide a solution for ensuring repair of a damaged disc flange at the level of a balancing weight attachment. STATEMENT OF THE INVENTION

[0012] For this purpose, the subject of the invention is a method for repairing a crown of a turbomachine rotor flange, this crown comprising at least two flange fixing holes and at least one weight fixing hole located between the two flange fixing holes, each flange fixing hole being equipped with a crimped nut, the crown comprising a damaged portion between two flange fixing holes, the method comprising the steps of: remove the two crimped nuts; remove the damaged crown portion, for example by machining; add a crown portion-shaped bar filling the removed crown portion, this bar comprising at least one weight fixing hole, and two mounting holes; fix the bar to the crown by means of two crimped nuts passing through the mounting holes, each being crimped into a flange fixing hole.

[0013] This solution thus makes it possible to repair the flange crown instead of having to replace the entire rotor component carrying this flange.

[0014] The invention also relates to a method thus defined, in which the same operations are carried out at a location of the crown situated 180° from the damaged crown portion to compensate for the imbalance introduced at the level of the damaged portion.

[0015] The invention also relates to a method thus defined, in which the bar is attached to a downstream face of the crown relative to the direction of circulation of fluid in the turbomachine.

[0016] The invention also relates to a method thus defined, in which the crimped nuts used to fix the bar have a greater length than the crimped nuts initially mounted on the crown.

[0017] The invention also relates to a method thus defined, in which the bar has a shape comprising a notch.

[0018] The invention also relates to a turbomachine comprising a rotor having a flange repaired in accordance with the method thus defined.

[0019] The invention also relates to a turbojet comprising a turbomachine thus defined. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] There Figure 1 is a longitudinal sectional view of a known turbojet engine; The Figure 2is a longitudinal sectional view of a fan disc with a portion of blade carried by this disc; The Figure 3 is a perspective view of a portion of a fan disc to be repaired in accordance with the invention; The Figure 4 is a longitudinal sectional view showing a crimped nut fitted to an upstream ring of the fan disc to be repaired; The Figure 5 is a perspective view of a portion of a fan disc after machining during its repair in accordance with the invention; The Figure 6 is an overall view of a repair bar according to the invention; The Figure 7 is a perspective view of a portion of a rotor disc when a repair bar is added in accordance with the invention; The Figure 8 is a perspective view of a portion of a fan rotor disc repaired in accordance with the invention; The Figure 9is a longitudinal sectional view of a crimped nut used to implement the repair according to the invention, with the repair bar according to the invention installed; The Figure 10 is a front view of a portion of disc repaired according to the invention and carrying a weight; The Figure 11 is an overview of a variant of the repair bar according to the invention. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0021] On the figure 3 , a portion of a fan disk 14 extending around an axis AX comprises at its external periphery a series of bases 15 intended to each receive a blade root to hold it, these bases 15 being regularly distributed at the external periphery of the disk 14. Each base 15 has a general shape corresponding to the female part of a dovetail type connection, and extends in a direction substantially parallel to the axis AX.

[0022] This fan disc 14 comprises at its upstream face a substantially flat upstream crown 16, forming a flange, extending perpendicular to the axis AX. This crown is located upstream relative to the direction of flow circulation in the engine in service, the upstream and downstream being identified respectively by AM and AV in the figures.

[0023] This crown 16 is delimited externally by a circular external edge 17 and internally by an essentially circular internal edge 18, being connected to the body of the disc 14 by means of a cylindrical portion extending its external edge 17.

[0024] As visible on the figure 3 , this crown 16 has holes 19 for fixing a locking flange not shown, and holes 21 for fixing weights which are installed during the balancing of the entire rotor of which this disc 14 is a part.

[0025] Each hole 19 is fitted with a corresponding crimped nut 22. As shown in the figure 4 , such a crimped nut 22 comprises a body or head 23 extended by a skirt 24 formed in one piece with the head. This skirt 24 is engaged and crimped in the hole 21 so as to secure the nut 22 to the hole 19 which carries it: the head 23 is located on the downstream side of the crown and the skirt 24 passes through this crown to extend inside the hole towards the upstream face 27.

[0026] In the case of the disc 14, the upstream crown 16 is located at a distance from the body of this disc 14, a space thus being available between the downstream face 26 of the crown and the disc body, the flange being applied to the upstream face 27 of this crown 16.

[0027] Thus, and as visible on the figure 4, the head 23 of the crimped nut 22 is located on the downstream side of the crown 16, such that the upstream face 27 of this crown is cleared to receive the flange, the crimping skirt 24 having along the axis AX a thickness very slightly less than that of the crown 16.

[0028] The holes 19 are regularly distributed all around the axis AX by being formed in the crown 16. Between each pair of consecutive flange fixing holes 19, the crown has two weight fixing holes 21 and an internal notch 28 formed in the internal edge of the crown.

[0029] When dismantling the weights carried by the holes 21, the portion of the crown 16 carrying the fixing holes 21 may be damaged, to the point that it is no longer possible to fix a weight there again.

[0030] According to the invention, a machining or similar operation is then carried out to remove this damaged portion of crown, by forming an extended notch 29 in the internal edge of the crown 16, as visible in the Figure 5 This operation thus makes it possible to completely remove the entire damaged portion of the crown, without penalizing the fixing of the upstream flange, since the parts of the crown comprising the holes 19 remain present. In addition, the crimped nuts 22 equipping these holes 19 are removed, so as to completely free the region for fixing the weights.

[0031] Once these operations have been carried out, a bar 31 in the shape of a portion of a crown, shown alone on the figure 6 is placed against the downstream face 26 of the crown 16, as visible on the figure 7 , so that once it is in place, it covers the area that was removed, as clearly visible on the figure 8 .

[0032] As visible on the figures 6 and 7 , this bar 31 in the form of a crown portion has at its ends two mounting holes 32, and it has a length corresponding to the distance separating two flange fixing holes 19. Thus, the two mounting holes 32 of the bar 31 coincide with the two flange fixing holes 19 located on either side of the crown portion 16 having been removed.

[0033] As visible on the figure 6 , the bar 31 has the overall shape of a portion of the crown 16 with an angular extent slightly greater than the angle separating the holes 19, measured around the axis AX. This portion of crown 16 thus makes it possible to fill the damaged portion which has been removed while being fixed to the crown at its ends.

[0034] The bar 31 can have different shapes, approaching that of the removed crown portion: in the example of the figure 6 it has a notch 38 at its internal edge, allowing the attachment of other elements to the rotor. Depending on the configuration, this bar can also be without a notch as in the example of the figure 11 .

[0035] The attachment of the replacement bar 31 to the crown 16 is ensured, as illustrated in the figure 10 by two repair crimped nuts 33 which are slightly different from the initial crimped nuts 22. Each repair crimped nut 33 also has a head 34 extended by a crimping skirt 36, but this crimping skirt 36 is longer than the skirt 24 of the initial crimped nuts 22. This skirt thus has a length, along the axis AX, which corresponds to the thickness of the crown 16 increased by the thickness of the bar 31.

[0036] The fixing of the bar 31 is ensured by first placing it in position against the downstream face 26, then by engaging each crimped nut 33 jointly in a hole 32 of the bar and in a corresponding hole 19 of the crown 16. Once the assembly is in place, the two nuts 33 are crimped, for example by means of suitable pliers, in order to flare the upstream end of the skirts of these nuts so as to block them in the holes which carry them, in accordance with the configuration of the figure 9 .

[0037] Additionally, and as visible on the figures 6 to 8 , the bar 31 comprises two weight fixing holes 37 and a notch 38, which are placed at the same positions respectively as the fixing holes 21 and the notch 28 of the initial crown 16.

[0038] Once the assembly is in place, as shown in the figure 8, a new weight 39 can be fixed by riveting in the holes 37 of the repair bar, which corresponds to the configuration illustrated in the figure 10 .

[0039] After fixing the weight, the upstream flange can be attached to the disc, being fixed to it by means of screws passing through it to each screw into a corresponding crimped nut carried by the crown 16.

[0040] As can be understood, the tightening of the fixing screws of the flange attached to the crimped nuts ensures the complete fixing of the bar to the crown by pressing it effectively against the downstream face 26 of the crown.

[0041] In practice, when a portion of the weight attachment is damaged on the crown 16, a repair is carried out as explained above at the location of the damage in order to allow the attachment of a new weight. In addition, the same repair is carried out (removal of a portion of the crown and addition of a bar to fill the removed portion) in the region of the crown diametrically opposite that of the damage, to ensure that the repair does not compromise the balancing of the disc.

[0042] In other words, the difference in mass induced by the addition of a bar at the damaged location is compensated by the addition of another bar in the diametrically opposite region of the crown (at 180°), even if this other region is not damaged. Thus, it is not necessary to carry out a new balancing of the disc because the repair does not introduce any imbalance.

[0043] As understood, if multiple regions of the crown are damaged, the repair is applied to each damaged region, and to each region located 180° from a damaged region.

[0044] Generally speaking, the invention makes it possible to restore the interface of the disc with the weight by mechanically reworking the damaged part of the flange without having to change the disc. The attached bar is advantageously made of the same material as the disc, so as to maintain unchanged mechanical characteristics.

Claims

1. Method for repairing a ring (16) of a turbomachine rotor end plate, this ring (16) including at least two plate-securing holes (19) and at least one balance-weight securing hole (21) located between the two plate securing holes (19), each plate-securing hole (19) being equipped with a crimped nut (22), the ring (16) including a damaged portion between two plate-securing holes (19), the method including the steps of: - removing the two crimped nuts (22); - removing the damaged ring portion, for example by machining; - attaching a bar (31) in the form of a ring portion making up for the removed ring portion (16), this bar (31) including at least one balance-weight fixing hole (37), and two mounting holes (32); - attaching the bar (31) to the ring (16) by means of two crimped nuts (33) passing through the mounting holes while each being crimped in a plate-attaching hole (19).

2. Repair method according to claim 1, wherein the same operations are implemented at a point on the ring (16) located at 180° from the damaged ring portion to compensate for the imbalance introduced at the damaged portion.

3. Method according to claim 1, wherein the bar is attached to a downstream face (26) of the ring (16) with respect to the direction of circulation of fluid in the turbomachine.

4. Method according to one of claims 1 to 3, wherein the crimped nuts (33) used for securing the bar (31) have a greater length than the crimped nuts (22) initially mounted on the ring (16).

5. Method according to claim 1, wherein the bar (31) has a form including a scallop (38).

6. Turbomachine including a rotor having an end plate including a ring repaired with a method according to claim 1.

7. Turbojet engine including a turbomachine according to claim 6.