Maintenance procedure for a high-pressure turbine blade of a turbomachine
The use of removable shims between blade roots and the disc addresses the issue of increasing clearance due to wear and thermal erosion, enhancing turbomachine performance and reducing maintenance costs.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- SAFRAN AIRCRAFT ENGINES SAS
- Filing Date
- 2022-03-18
- Publication Date
- 2026-05-22
AI Technical Summary
The clearance between the tips of turbine blades and the casing in turbomachines increases over time due to wear and thermal erosion, leading to performance degradation, increased consumption, and operating temperatures, necessitating costly blade replacements.
A method involving the use of removable shims between the blade roots and the disc to adjust the radial clearance, allowing for the restoration of optimal performance without replacing or repairing the blades.
Reduces radial clearance effectively and improves turbomachine performance by compensating for wear and corrosion, thus avoiding costly blade replacements.
Abstract
Description
Title of the invention: Method for maintaining a high-pressure turbine blade of a turbomachine Technical field of the invention
[0001] The invention relates to a method for maintaining a high-pressure turbine bladed wheel of a turbomachine, such as a turbojet or aircraft turboprop. Prior art
[0002] Figure 1 represents a twin-flow, twin-body turbomachine 1. The axis of the turbomachine is referenced as X. In what follows, the terms axial and radial are defined with respect to the X axis.
[0003] The turbomachine 1 comprises, from upstream to downstream in the direction of gas flow within the turbomachine 1, a blower 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.
[0004] The air from the blower 2 is divided into a primary flow A flowing into a primary vein 8, and a secondary flow B flowing into a secondary vein 9.
[0005] The low pressure compressor 3, the high pressure compressor 4, the combustion chamber 5, the high pressure turbine 6 and the low pressure turbine 7 are provided in the primary vein 8.
[0006] The high-pressure turbine 6 and the high-pressure compressor 4 are coupled in rotation via a first shaft 10 so as to form a high-pressure body.
[0007] The low-pressure turbine 7, the low-pressure compressor 3 and the blower 2 are coupled in rotation via a second shaft (not shown) so as to form a low-pressure body.
[0008] As shown in [Fig.2], the high-pressure turbine 6 conventionally comprises a disc 11 on which blades 12 are mounted. Each blade 12 comprises a blade 13 extending radially outwards from a blade root 14 mounted in a cavity 15 of the disc 11.
[0009] The apex 16 of the blade 12 is formed by the radially external end of the blade 12. The foot 14 and the blade 13 are here separated by a radially internal platform 17. The foot 14 has a general fir tree shape, here with four branches or lobes 18. The shape of the cavity 15 is complementary to the shape of the foot 14.
[0010] Each branch or lobe 18 bears against a complementary opposite surface of the disc 11. The surfaces of the foot 14 and the disc 11 bearing against each other are called spans 19. In the embodiment illustrated in [Fig.4], the foot 14 has four spans 19, arranged symmetrically with respect to a median radial plane P.
[0011] The blades 12 are surrounded by an annular casing 20. A clearance j is formed between the vertices 16 of the blades 12 and the casing 20 surrounding the blades 12.
[0012] In order to maximize the efficiency of the turbomachine, it is necessary to limit the flow of gas flowing in the gaps located between the tips of the blades and the casing.
[0013] In operation, this play tends to increase over time due to two phenomena.
[0014] The first phenomenon is the wear of the blade tip generated by the friction between the blade tip and the casing facing it.
[0015] The second phenomenon is thermal erosion, i.e. oxidation, of the top of the blade, due to the high temperatures to which the blade is subjected in operation, in particular in the case of a high-pressure turbine.
[0016] Increasing this clearance leads to a degradation of the turbomachine's performance and, consequently, to an increase in the turbomachine's consumption and operating temperatures, further aggravating the oxidation phenomenon.
[0017] Currently, when a blade is too worn or too oxidized at its tip, it is replaced and discarded. Such maintenance is therefore very costly and / or leads to unplanned removals of the turbomachine due to performance limits being reached. Presentation of the invention
[0018] The invention aims to remedy the aforementioned problems in a simple, reliable and inexpensive way.
[0019] To this end, the invention proposes a method for maintaining a high-pressure turbine wheel of a turbomachine, extending along an axis, comprising a disc including recesses, and radially extending blades, each comprising a blade and a radially internal root, the root of each blade being mounted in a recess of the disc, said root bearing on the disc via surfaces of the root and the disc forming bearing surfaces, characterized in that at least one shim is removably mounted between the root of at least one blade and the disc, at the level of the corresponding bearing surfaces, said method comprising the following steps:
[0020] - measure a radial clearance between the apex of at least one blade, i.e. the end radially external to the blade, and a turbomachine housing located opposite the bladed wheel,
[0021] - if the radial play is greater than a determined value, remove said shim.
[0022] The method according to the invention thus aims to determine the state of wear or deformation of the high-pressure turbine by measuring the radial clearance between the tip of the blade and the housing and, if the aforementioned radial clearance is too large, removing the shims. Removing the shims then makes it possible to reduce the radial clearance between the tip of the blade and the housing, so as to restore acceptable performance, at a lower cost, without replacing or repairing the blades or the housing.
[0023] At least one shim can be mounted between the foot of each blade and the disc, at the level of the corresponding bearing surfaces, all shims being removed if the radial clearance is greater than said determined value.
[0024] In this way, disparities or steps formed by differences in the positioning of the blade tips on the circumference of the turbomachine are avoided. Such steps can generate aerodynamic disturbances affecting the proper functioning of the turbomachine.
[0025] The shim can be mounted removably on the paddle foot.
[0026] The shim can be removably mounted on the disc, for example in the alveolus or on a tooth of the disc delimited between two adjacent alveoli.
[0027] The shim may include a radial stop surface, bearing against a complementary stop surface of the foot of the blade or the disc.
[0028] Such a feature makes it easier to achieve the correct axial positioning of the shim and also makes it possible to retain the shim axially in position during the operation of the turbomachine.
[0029] The slender can have a thickness of between 0.1 and 0.9 mm.
[0030] The shim can be made from a cobalt-based alloy.
[0031] The shim is for example made from an alloy known under the reference MP 159.
[0032] The base of the dawn can be a base in the general shape of a fir tree.
[0033] Each foot can have a symmetrical shape with respect to a radial plane median.
[0034] A single shim can be mounted between the vane foot and the disc. This single shim can be inserted between several spans of the vane and the disc.
[0035] Several shims can be mounted removably between the foot of at least one blade and the disc.
[0036] In such a case, the flashings can be arranged symmetrically with respect to the aforementioned median radial plane.
[0037] It is also possible to arrange a stack of several shims between the blade foot bearings and the disc bearings. In this case, one or more shims can be removed during each maintenance operation.
[0038] Each foot can have two pairs of stalks, cooperating with two pairs of stalks of the disc cavity. The foot can thus have a four-sided fir tree shape branches or four lobes, such a shape being frequently used in the case of a bladed high-pressure turbine wheel. The cavity naturally has a shape complementary to that of the base.
[0039] The shim can be produced by stamping sheet metal or by sintering a metal powder.
[0040] The invention also relates to a high-pressure turbine bladed wheel comprising a disc including cavities, and blades each comprising a blade and a foot, the foot of each blade being mounted in a cavity of the disc, said foot being supported on the disc by means of surfaces of the foot and the disc forming bearing surfaces, characterized in that at least one shim is mounted removably between the foot of at least one blade and the disc, at the level of the corresponding bearing surfaces.
[0041] The bladed wheel is preferably a rotor bladed wheel.
[0042] The shim is formed by a thin sheet of metal.
[0043] The invention also relates to a turbomachine, characterized in that it comprises a bladed wheel of the aforementioned type.
[0044] The turbomachine can be a turbojet or an aircraft turboprop. The aircraft can be an airplane. Brief description of the figures
[0045] [Fig-1] is a schematic cross-sectional view of a prior art turbomachine;
[0046] [Fig.2] is a schematic view of part of a high-pressure turbine of the art previous;
[0047] [Fig.3] is a view illustrating the mounting of a blade foot in a cavity of a disc of a bladed wheel according to one embodiment of the present document;
[0048] [Fig.4] is a perspective view of a cell equipped with a shim, according to the embodiment of [Fig.3];
[0049] [Fig.5] is a perspective view of a paddle foot equipped with two lateral clappers, according to another embodiment;
[0050] [Fig.6] is a perspective view of a vane foot equipped with a single clapper, according to another embodiment;
[0051] [Fig.7] is a view corresponding to [Fig.3], in which the tinsel has been removed following a maintenance operation. Detailed description of the invention
[0052] Figures 3 and 4 illustrate a bladed wheel of a high-pressure turbine rotor 6 according to one embodiment.
[0053] This embodiment differs from that illustrated in [Fig. 2] in that a shim 21 is removably mounted in each cavity 15 and completely covers or almost entirely the internal surface of each of the cavities 15 of the bladed wheel. The shim 21 thus has a general U-shaped form and includes recesses adapted to house the lobes 18 of the foot 14 of the corresponding blade 12. The shim 21 therefore has surfaces 22 intended to come into contact with the bearing surfaces of the foot 14 of the blade 12. These surfaces are called the bearing surfaces 22 of the shim 21.
[0054] The shim 21 is formed by a sheet of thickness between 0.1 and 0.9 mm, and made of a cobalt-based alloy.
[0055] The foot 14 of the vane 12 rests on the supports 22 of the shim 21 after mounting in the alveolus 15.
[0056] It will be noted that the radial position of the apex 16 of the blade 12 takes into account the thickness of the shim 21 in its specifications in order to obtain the desired clearance j.
[0057] It is also possible to use two shims 21, located on either side of the median plane P and arranged symmetrically, said shims 21 covering the spans 19 of the cavity 15. Each shim 21 covers only half, or less, of the cavity 15.
[0058] Figures 4 and 5 illustrate two embodiments in which the tinplates 21 are mounted removably, not in the alveoli 15, but on the feet 14 of the blades 12.
[0059] The assembly formed by the paddle foot 14 and the shim(s) 21 is then mounted in the corresponding cavity 15 of the disc 11.
[0060] Fig. 5 illustrates in particular an embodiment in which two lateral shims 21 are mounted on either side of the foot 14, symmetrically with respect to the median radial plane P. Each shim 21 has a shape complementary to the lateral side of the foot 14, each shim 21 thus covers the two relevant lateral bearing surfaces 19 of the foot 14 of the blade 12.
[0061] Fig. 6 illustrates one embodiment in which a single shim 21 covers both lateral sides of the foot 14 of the awl 12, i.e. covers all the spans 19 of the foot 14.
[0062] The shim 21 has a shape complementary to that of the foot 14 and includes a radial wall 23 suitable for forming an axial stop bearing against a radial end surface 24 of the foot 14, which can be an upstream or a downstream surface of the foot 14.
[0063] Note that the shim 21 does not cover the radially internal end surface 25 of the foot 14. Indeed, cooling air circulation channels for the blade 12 open at this end surface 25, and it is necessary not to obstruct said channels. Alternatively, the shim 21 may cover said radially internal end surface 25 of the foot 14 but then has openings or ports opposite the openings of said channels, so as to allow the passage of air cooling.
[0064] As previously stated, this document proposes a method for maintaining such a high-pressure turbine bladed wheel 6, said method comprising a step in which the radial clearance j between the tip 16 of the blade 12 and the casing 20 is measured and, if this radial clearance j is greater than a predetermined value, the shim(s) 21 are removed, as illustrated in [Fig. 7]. This has the effect of bringing the blade tip 16 closer to the casing 20, and thus reducing the clearance j by the value of the thickness of the shim 21.
[0065] It is thus possible to reduce the play j in a simple, quick and inexpensive way, in order to improve the performance of the turbomachine and compensate for the aforementioned wear or corrosion phenomena.
Claims
Demands
1. A method for maintaining a high-pressure turbine wheel (6) of a turbomachine, extending about an axis, comprising a disk (11) having recesses (15), and radially extending blades (12) each having a blade (13) and a radially internal foot (14), the foot (14) of each blade (12) being mounted in a recess (15) of the disk (11), said foot (14) bearing on the disk (11) via surfaces of the foot (14) and the disk (11) forming bearing surfaces (19), characterized in that at least one shim (21) is removably mounted between the foot (14) of at least one blade (12) and the disk (11), at the corresponding bearing surfaces (19), said method comprising the following steps: - measuring a radial clearance (j) between the apex (16) of at least one blade (12), that is to say the radially external end of the blade (12), and a housing (20) of the turbomachine located opposite the bladed wheel,- if the radial clearance (j) is greater than a specified value, remove the said shim (21).
2. Method according to the preceding claim, wherein at least one shim (21) is mounted between the foot (14) of each blade (12) and the disc (11), at the level of the corresponding bearing surfaces (19), all of the shims (21) being removed if the radial clearance (j) is greater than said determined value.
3. A method according to any one of the preceding claims, wherein the shim (21) is removably mounted on the paddle foot (14).
4. A method according to any one of claims 1 or 2, wherein the shim (21) is removably mounted on the disc (11), for example in the cavity (15) or on a tooth of the disc (11) delimited between two adjacent cavities (15).
5. A method according to any one of the preceding claims, wherein the shim (21) comprises a radial stop surface (23), bearing against a complementary stop surface (24) of the foot (14) of the blade (12) or of the disc (11).
6. A method according to any one of the preceding claims, wherein the shim (21) has a thickness of between 0.1 and 0.9 mm.
7. A method according to any one of the preceding claims, wherein the shim (21) is made in a cobalt-based alloy.
8. A method according to any one of the preceding claims, wherein several shims are removably mounted between the foot (14) of at least one vane (12) and the disc (11).