Improved centering device for assembling turbine bladed discs

Abstract

Improved centering device for assembling turbine bladed discs. Centering device (1) for assembling turbine bladed discs, the centering device being centered on a central axis (X) and comprising an assembly and centering frame (10) according to claim 1 and a rotor disc (30), the frame (10) cooperating on the one hand with a turbine stator (20, 22), and on the other hand with the rotor disc (30), the rotor disc (30) comprising at least a second centering means (38) cooperating with a first centering means (18) of the frame (10) so as to position the rotor disc (30) radially and circumferentially relative to the frame (10). Figure for the abstract: Fig. 1.

Description

Title of the invention: Improved centering device for the assembly of turbine bladed discs Technical field

[0001] The present disclosure relates to the assembly of single-piece bladed discs, in particular for low-pressure turbines, but not exclusively. In particular, the present disclosure relates to a centering device for the assembly of turbine bladed discs, and a centering method during the assembly of such turbine bladed discs. Prior art

[0002] A gas turbine, in particular a low-pressure turbine of a turbomachine, typically comprises a plurality of fixed blades arranged axially alternately with a plurality of moving blades in the passage of hot gases from the combustion chamber of the turbomachine. The moving blades of the turbine are carried by a single-piece rotor disc and surrounded over the entire circumference by a fixed stator ring. This ring partly defines the passage for the flow of hot gases through the blades of the turbine.

[0003] When assembling the low-pressure turbine, the centering of the rotor discs relative to the stator is decisive for the proper operation of this turbine and the turbomachine.

[0004] In a known manner, during assembly, a fixed casing of the turbine is first fixed to an assembly frame. A first rotor disk stage is then placed on the assembly frame. During this removal, a tool is used to center the first stage relative to a central column of the assembly frame. Clamping the first rotor disk stage on the assembly frame allows the centering imposed by the tool to be maintained. After removal of the tool, a clearance measurement is typically carried out in four positions on the circumference of the disk, in order to measure the clearance between the end of the rotor blades and the sealing parts of the stator ring and thus evaluate the offset of the first rotor stage relative to the stator.

[0005] The clamping of the first rotor disc stage is then removed and the disc is moved manually in order to improve the centering relative to the stator, by adjusting the clearances measured in the previous step so that they all have the same value. A clamping of the first rotor disc stage on the assembly frame is then carried out again, and the following stages are then assembled on the first stage.

[0006] Thus, the centering of the turbine rotor is guaranteed by the correct centering of the first rotor stage. In the case where the latter is poorly centered, the stacking of the following stages can lead to excessive off-centering due to the accumulation of tolerances of each stage, resulting in a non-compliant rotor position in relation to the stator. This poor positioning can generate clearances between the rotor and the stator that are either too tight or too open depending on the angular position where these clearances are measured.

[0007] When the measured clearances do not conform to the desired tolerances, typically 0.02 mm, a complete disassembly of the turbine may be necessary to recenter the first rotor stage and thus obtain better centering of the rotor relative to the stator on the following stages.

[0008] However, current assembly and centering devices and methods such as those described above do not allow the previously mentioned tolerances to be respected. This is due in particular to the uncertainty linked to the manual displacement of the first stage of the rotor disk, and to the tolerances linked to the sealing parts of the stator ring when taking the clearance to recenter the disk. The disassembly of the turbine module, often necessary to limit the decentering of the rotor due to the accumulation of these uncertainties, is time-consuming and harms the quality of the work, the efficiency and the yield of the assembly of low-pressure turbines.

[0009] There is therefore a need to remedy at least in part the aforementioned drawbacks. Statement of the invention

[0010] The present disclosure relates to an assembly and centering frame for a centering device for assembling bladed turbine disks, the frame being intended to be centered on a central axis of a disk, the frame being configured to cooperate on the one hand, with a turbine stator, and on the other hand, with a rotor disk, the frame comprising at least one first centering means capable of cooperating with at least one second centering means of the rotor disk so as to position the rotor disk radially and circumferentially relative to the frame.

[0011] The present disclosure also relates to a centering device for assembling bladed turbine disks, the centering device being centered on a central axis and comprising an assembly and centering frame according to the present disclosure and a rotor disk, the frame cooperating on the one hand with a turbine stator, and on the other hand with the rotor disk, the rotor disk comprising at least a second centering means cooperating with a first centering means of the frame so as to position the rotor disk radially and circumferentially relative to the frame.

[0012] In the present disclosure, the terms "axial", "radial", "tangential", "internal", "external" and their derivatives are defined with respect to the main axis of the turbine, which is typically the axis of rotation of the rotor of this turbine.

[0013] The turbine stator can be fixed to the assembly and centering frame by shrink-fitting a fixed casing of said stator onto the frame, so as to position and immobilize the stator. relative to the frame. Preferably, the assembly and centering frame has an annular shape.

[0014] It is understood that the first centering means and the second centering means are arranged respectively on the frame and on the rotor disk in such a way as to allow, when they cooperate with each other, the rotor disk to be precisely positioned relative to the frame.

[0015] Positioning the rotor disc relative to the frame on which the stator is fixed, and not relative to the stator itself, makes it possible to improve the accuracy of the centering. Indeed, it is possible, during the manufacture of the frame, to machine the centering means in such a way that the dimensional tolerances are sufficiently precise to allow correct centering. Thus, the frame allows not only the assembly of the turbine, but also the centering of the rotor relative to the stator.

[0016] The device according to the present disclosure thus makes it possible to reduce assembly time, while improving the precision of the centering of the rotor during assembly, positioning tools and manual adjustments no longer being necessary. The risks of requiring disassembly of the turbine module to recenter the rotor are also limited. The efficiency and effectiveness of the assembly are therefore improved.

[0017] In some embodiments, the frame comprises three first centering means, and the rotor disk comprises three second centering means.

[0018] Preferably, the number of first centering means is identical to the number of second centering means. The presence of three first centering means and three second centering means makes it possible to further improve the centering precision.

[0019] In some embodiments, the rotor disk is a rotor disk of a first stage of a low pressure turbine rotor.

[0020] Improving the centering accuracy of the first stage of the low-pressure turbine rotor consequently makes it possible to improve the centering quality of the following stages and of the entire turbine.

[0021] In some embodiments, the second centering means is disposed at a radially outer end of a hub of the rotor disk.

[0022] The rotor disc typically comprises an internal structural part, namely the hub (or web, or rim) extending between a radially internal end and a radially external end, and an external part comprising a plurality of teeth and cells intended to receive the moving rotor blades, distributed circumferentially on a radially external periphery of the rotor disc and around the radially external end of the hub.

[0023] It is thus understood that the second centering means is arranged radially at the inside of the external part, that is to say radially under the teeth and alveoli of the disc and adjacent to them.

[0024] The precision of the positioning of the second centering means arranged at this location makes it possible to improve the precision of the centering of the rotor, and in particular of the rotor blades.

[0025] In some embodiments, the second centering means is disposed at a radially inner end of a hub of the rotor disk.

[0026] This makes it possible to simplify the implementation of the second centering means, for example by simply carrying out machining on the periphery of the radially internal end of a hub, so as to create a housing capable of receiving the first centering means.

[0027] In some embodiments, the first centering means comprises a centering pin extending axially from an axial face of the frame, and the second centering means comprises a housing into which the centering pin is inserted.

[0028] The second centering means may in particular comprise two protuberances forming between them a housing in which the centering pin is inserted. Alternatively, the housing may be produced by machining in the disc, for example at the radially internal end of the hub.

[0029] These means have the advantage of being simple to produce. Furthermore, the production of pins or machining allows precise control of manufacturing tolerances, which makes it possible to further improve the precision of the centering of the rotor disk when the first and second centering means, in other words the pin and the housing, cooperate with each other.

[0030] In some embodiments, the first centering means is a machining formed in a hollow on an axial face of the frame, and the second centering means is a rib extending axially projecting from a face of the rotor disk and being disposed in the machining of the frame.

[0031] A rib may be a thin longitudinal projection extending over one face of the rotor disc, and the machining may be a thin, longitudinal groove cut into the frame and of a shape complementary to the rib. This configuration makes it possible to simplify the structure of the disc and to minimize its mass. Alternatively, the first centering means is a rib and the second centering means is machining.

[0032] In some embodiments, the frame comprises, with respect to the central axis, a radially outer end, a radially inner end, a main portion which extends radially and connects the radially inner end to the radially outer end, in which the radially outer end of the frame comprises an external stator mounting flange and the radially inner end comprises a central portion from which the first centering means extends.

[0033] The fixed stator casing can be fixed to the external flange by shrink fitting, so as to immobilize the stator relative to the frame. Positioning the rotor disc on the central portion allows the rotor disc to be precisely centered relative to the entire frame, and therefore relative to the stator.

[0034] In some embodiments, the turbine stator includes an outer casing having an upstream hook and a downstream hook on which a sealing ring is mounted, the sealing ring being disposed radially within the outer casing.

[0035] The present disclosure also relates to a centering method for assembling turbine bladed discs, using a centering device according to any one of the preceding embodiments, and comprising steps of: - mounting a turbine stator on the centering device frame, - arrangement of a rotor disc on the frame, by making a first means for centering the frame cooperate with a second means for centering the rotor disc, so as to position the rotor disc relative to the frame.

[0036] For the reasons described above, the method according to the present disclosure makes it possible to reduce the assembly time, to improve the precision of the centering of the rotor relative to the stator, and consequently to improve the efficiency and quality of the assembly.

[0037] In some embodiments, the mounting of the stator on the frame is carried out by shrink-fitting a fixed external casing of the stator onto an external flange of the frame.

[0038] The present disclosure also relates to a method of assembling a low-pressure turbine of a turbomachine, comprising the centering of a first rotor disk stage on the frame of the centering device by a centering method described previously, and the successive assembly of a plurality of turbine stages on said first stage.

[0039] Since the centering accuracy of the first rotor stage is improved, the centering accuracy of all the turbine stages, particularly the low-pressure turbine, is also improved. The risks of complete disassembly of the turbine module are therefore limited. Brief description of the drawings

[0040] The invention and its advantages will be better understood upon reading the detailed description given below of different embodiments of the invention given as non-limiting examples. This description refers to the appended pages of figures, in which:

[0041] [Fig-1] [Fig. 1] is a partial perspective view of a centering device according to a first embodiment;

[0042] [Fig.2] [Fig.2] represents a detailed view of the device of [Fig.l];

[0043] [Fig.3] [Fig.3] represents a perspective view of an assembly frame and centering of the device according to the first embodiment, as well as a detailed view of a portion of said frame;

[0044] [Fig.4] [Fig.4] represents a partial perspective view of a first floor of rotor disk of the device according to the first embodiment;

[0045] [Fig.5] [Fig.5] schematically represents the steps of an assembly process of a turbine;

[0046] [Fig.6] [Fig.6] is a partial perspective view of a centering device according to a second embodiment;

[0047] [Fig.7] [Fig.7] is a detailed view of the device of [Fig.6], showing the co operation between a first and a second centering means. Description of the embodiments

[0048] Figures 1 and 2 represent partial perspective views of a centering device 1 according to different orientations of a first embodiment of the invention.

[0049] The centering device 1 comprises an assembly and centering frame 10 (hereinafter "frame 10"), a turbine stator 20 fixed on the frame 10, and a turbine rotor disc 30 arranged on the stator 20 and the frame 10. In this example, the stator and the rotor are low pressure turbine stators and rotors.

[0050] [Fig. 3] shows a perspective view of the frame 10 alone. The frame 10 is typically axisymmetrical around a central axis X, corresponding to the central axis of the turbine and therefore of the rotor disk when the latter is arranged on the frame 10. In the remainder of the description, the terms “axial”, “radial”, “tangential”, “internal”, “external” and their derivatives are defined relative to the central axis X, and the radial direction R.

[0051] The frame 10 comprises an annular main portion 12 on which the stator 20 is intended to be arranged. An external flange 14 extends along a radially external end of the main portion 12, over its entire circumference. The frame 10 further comprises, at a radially internal end of the main portion 12, a central portion 16. The central portion 16 comprises a cylindrical vertical wall 161 extending axially from the main portion 12, and an axial face 162 extending from the vertical wall 161 in a plane perpendicular to the central axis X.

[0052] Furthermore, the frame 10 comprises at least one first centering means 18, in this example three centering means 18. However, the frame 10 may comprise a greater number of first centering means without departing from the scope of the invention. In this embodiment, the first centering means are pins 18 extending axially from the axial face 162. The pins 18 are preferably distributed uniformly on the axial face 162 and at regular intervals circumferentially around the central axis X.

[0053] Furthermore, the stator 20 typically comprises a fixed casing 22 capable of being fixed to the frame 10, for example by shrink-fitting onto the external flange 14, and of resting on the main portion 12. The fixed casing 22 carries a fixed stator ring 24, which may be made up of an assembly of ring sectors. A radially internal face of the fixed ring 24 is intended to delimit a hot air flow duct of the turbine, and comprises a sealing material cooperating with tabs arranged at the end of the blades 40 of the rotor.

[0054] [Fig. 4] shows a partial perspective view of a portion of the rotor disc 30 alone. The rotor disc 30 is a first stage of a low-pressure turbine rotor, on which the subsequent stages of the turbine are intended to be positioned during assembly of the turbine. When the rotor disc 30 is arranged on the frame 10, the rotor disc 30 and the frame 10 are concentric with the central axis X.

[0055] The rotor disk 30 typically comprises a hub 32 (or web, or rim), which is the central and structural portion of the disk. The hub 32 extends between a radially inner end 321, approaching which the hub 32 becomes wider, and a radially outer end 322. The rotor disk 30 also comprises an outer portion 34 having a plurality of teeth 35 and sockets 37 for receiving the movable rotor blades 40. The teeth 35 and sockets 37 are distributed circumferentially on a periphery of the outer portion 34 of the rotor disk 30 and around the radially outer end 322 of the hub 32.

[0056] It will be noted that the rotor disc 30 also comprises an axial sleeve 36 ([Fig.2]) at the end of which a flange with orifices 362 allows the fixing of the following stages of the turbine rotor.

[0057] Furthermore, the rotor disk 30 comprises at least one second centering means 38, in this example three centering means (only one is visible in [Fig.4]). However, the rotor disk 30 may comprise a greater number of second centering means without departing from the scope of the invention, the number of second centering means being equal to the number of first centering means.

[0058] In this embodiment, the second centering means 38 comprise two protuberances 381 circumferentially adjacent to one another so as to form a housing 382 between them. The second centering means 38, and therefore the protuberances 381 and the housing 382, ​​are arranged at the radially external end 322 of the hub 32, that is to say radially under the external part 34 and adjacent thereto.

[0059] The second centering means 38, and therefore the protrusions 381 and the housing 382, ​​are preferably distributed uniformly on the hub 32 and at regular intervals. circumferentially around the central axis X. Furthermore, the second centering means 38 are formed such that the width of the housings 382 is substantially equal to the diameter of the pins 18, in order to ensure the precision of the centering. In particular, the dimensioning of the pins 18 and the housings 382 allows positioning of the rotor disk 30 relative to the frame 10, and therefore relative to the stator 20, with a tolerance of 0.02 mm for example.

[0060] Preferably, the diameter of the pins 18 and the width of the housings 382 are dimensioned so as to be substantially equal to the dimensions of the orifices 362.

[0061] The centering means 18, 38 may be provided during the manufacture of the frame 10 and the rotor disk 30, for example by additive manufacturing. In particular, the pin 18 and the protrusions 381 may be provided during the manufacture of the frame 10 and the rotor disk 30, then machined so as to adjust their dimensions to the desired values.

[0062] A method for assembling bladed discs of a low-pressure turbine is shown schematically in [Fig.5], and comprises firstly the centering of the first rotor disc stage 30 (step S100), using the centering device 1, then the successive assembly of a plurality of turbine stages on said first stage 30 (step S200).

[0063] The centering S100 of the first rotor disk stage 30 itself comprises a first step (step SI 10) comprising the fixing of the turbine stator 20 on the assembly and centering frame 10.

[0064] To do this, the external flange 14 is dimensioned such that its diameter is substantially equal to the diameter of a base 22a of the fixed casing 22. The base 22a can thus be fixed by force, for example by shrinking onto the external flange 14. The fixed casing 22, and consequently the stator 20 including the fixed ring 24 fixed to the fixed casing 22, are thus centered on the frame 10 and extend around the central portion 16 of the latter.

[0065] A second step of the centering method (step S120) comprises arranging the first rotor disk stage 30 on the frame 10, by making the pins 18 of the frame 10 cooperate with the second centering means 38 of the rotor disk 30, so as to position and center the rotor disk 30 relative to the frame 10. In particular, each pin 18 is inserted into a housing 382.

[0066] The stator 20 and the first rotor stage 30 are thus both centered relative to the frame 10, and therefore positioned and centered relative to each other, without requiring additional tooling to perform such centering, nor a step of clamping the rotor on the frame. The following stages can thus be arranged successively on the first stage to perform step S200.

[0067] [Fig. 6] represents a partial perspective view of a centering device 1' according to a second embodiment of the invention, and [Fig. 7] a detailed view of [Fig. 6] showing the cooperation between a pin 18 and the second centering means 38.

[0068] The centering device 1' according to the second embodiment differs from the centering device 1 according to the first embodiment in that the second centering means 38, and therefore the protrusions 381 and the housing 382, ​​are arranged at the radially internal end 321 of the hub 32, and not at the radially external end 322. In particular, protrusions 381 are formed along the radially internal circumference of the hub 32, forming between them a housing 382 intended to receive a pin 18 ([Fig.7]).

[0069] Alternatively, the housing 382 could be formed by making a notch along the radially inner circumference of the hub 32, without requiring the presence of protrusions 381.

[0070] To take into account this arrangement of the second centering means 38, the axial face 162 of the central portion 16 is elongated relative to the axial face 162 of the first embodiment. In other words, the axial face 162 extends radially over a larger surface area, compared to the axial face 162 of the first embodiment, the pins 18 being arranged close to a radially internal end of the axial face 162.

[0071] The other features not mentioned, as well as the assembly and centering method, remain identical to the first embodiment.

[0072] In a modified example (not shown) of the first and second embodiments, the first centering means 18 is a machining formed for example on the axial face 162 of the frame 10, and the second centering means 38 is a rib extending on a face of the hub 32 of the rotor disk 30 and being arranged in the machining of the frame 10.

[0073] The rib may be a thin longitudinal projection extending for example on a face of the hub 32 of the rotor disk 30, and the machining a thin and longitudinal groove hollowed out for example on the axial face 162 of the frame 10 and of a shape complementary to the rib.

[0074] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated / mentioned embodiments may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

[0075] It is also obvious that all the characteristics described with reference to a method are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a process.

Claims

Claims

1. Frame (10) for assembling and centering a centering device (1) for assembling bladed turbine disks, the frame (10) being intended to be centered on a central axis (X) of a disk, the frame (10) being configured to cooperate on the one hand, with a turbine stator (20, 22), and on the other hand, with a rotor disk (30), the frame (10) comprising at least one first centering means (18) capable of cooperating with at least one second centering means (38) of the rotor disk (30) so as to position the rotor disk (30) radially and circumferentially relative to the frame (10).

2. Centering device (1) for assembling bladed turbine discs, the centering device being centered on a central axis (X) and comprising an assembly and centering frame (10) according to claim 1 and a rotor disc (30), the frame (10) cooperating on the one hand with a turbine stator (20, 22), and on the other hand with the rotor disc (30), the rotor disc (30) comprising at least a second centering means (38) cooperating with a first centering means (18) of the frame (10) so as to position the rotor disc (30) radially and circumferentially relative to the frame (10).

3. Centering device (1) according to claim 2, wherein the frame (10) comprises three first centering means (18), and the rotor disc (30) comprises three second centering means (38).

4. Centering device (1) according to claim 2 or 3, wherein the rotor disc (30) is a rotor disc of a first stage of a low pressure turbine rotor.

5. Centering device (1) according to any one of claims 2 to 4, wherein the second centering means (38) is arranged at a radially outer end (322) of a hub (32) of the rotor disc (30).

6. Centering device (1) according to any one of claims 2 to 4, wherein the second centering means (38) is arranged at a radially inner end (321) of a hub (32) of the rotor disc (30).

7. Centering device (1) according to any one of claims 2 to 6, wherein the first centering means (18) comprises a centering pin extending axially from an axial face (162) of the frame (10), and the second centering means (38) comprises a housing (382) into which the centering pin is inserted.

8. A centering device (1) according to any one of claims 2 to 6, wherein the first centering means (18) is a machining formed in a hollow on an axial face (162) of the frame (10), and the second centering means (38) is a rib extending axially projecting from a face of the rotor disc (30) and being arranged in the machining of the frame (10).

9. Centering device (1) according to any one of claims 2 to 8, wherein the frame (10) comprises, with respect to the central axis (X), a radially external end, a radially internal end, a main portion (12) which extends radially and connects the radially internal end to the radially external end, wherein the radially external end of the frame (10) comprises an external flange (14) for mounting the stator (20) and the radially internal end comprises a central portion (16) from which the first centering means (18) extends.

10. A centering device (1) according to any one of claims 2 to 9, wherein the turbine stator (20) comprises an outer casing (22) having an upstream hook and a downstream hook on which a sealing ring (24) is mounted, the sealing ring (24) being arranged radially inside the outer casing (22).

11. Centering method for assembling bladed turbine discs, using a centering device (1) according to any one of claims 2 to 10, and comprising steps of: - mounting a turbine stator (20) on the frame (10) of the centering device (1), - arranging a rotor disc (30) on the frame (10), by making a first centering means (18) of the frame (10) cooperate with a second centering means (38) of the rotor disc (30), so as to position the rotor disc (30) relative to the frame (10).

12. A method according to claim 11, wherein the mounting of the stator (20) on the frame (10) is carried out by shrink-fitting a fixed external casing (22) of the stator (20) onto an external flange (14) of the frame (10).

13. A method of assembling a low-pressure turbine of a turbomachine, comprising centering a first rotor disk stage (30) on the frame (10) of the centering device (1) by a centering method according to claim 11 or 12, and successively assembling a plurality of turbine stages on said first stage.

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