Blade profile for turbine disk of turbine, assembly for rotor of turbine, rotor of turbine, turbine and method for installing assembly of rotor of turbine

Abstract

The invention relates to a blade profile (400) for a turbine disc (40) of a turbine, comprising a metal sheet forming a housing at least partially surrounding teeth (42) of the turbine disc separating first and second chambers (41) of the disc, each chamber being adapted to receive a root (20) of a movable blade (10) of the turbine. The housing is adapted to at least partially cover:-each of the side walls (44) of the tooth, and-a downstream edge (46) of the tooth (42). The invention also relates to an assembly for a turbine rotor, a turbine rotor and a method for installing a turbine rotor assembly.

Description

Technical Field

[0001] The invention relates to a clinquant for a turbine disk of a turbomachine. The invention also relates to an assembly for a rotor, the assembly comprising such a clinquant mounted around the teeth of the disk. The invention also relates to a method for mounting such an assembly.

[0002] The invention can be applied in the field of aviation, in particular in the field of turbine rotors, to protect both the blade roots and the edges of the disks and to increase the service life of the rotors. Background Art

[0003] In aeronautics, it is known that a rotor blade 10 (an example of a rotor blade is shown in Figure 1 ) comprises a sheet 12, in the lower part of which is mounted a platform 11, from which radially extends a root 20 to be inserted into a cavity formed in the periphery of the disk of the rotor. The root 20 of the rotor blade 10 (also called movable blade) is radially retained in a cavity of the disk by a form fit between said root, which is generally dovetail-shaped, and the cavity, which is generally honeycomb-shaped. In the upper part, the sheet 12 is mounted a cover 13, which is arranged edge to edge with the cover of the adjacent movable blade to form a rotating circumferential ring delimiting a rotating surface around the axis of rotation X of the disk.

[0004] During operation of the rotor, contact between the roots of the movable blades, more simply called blade roots, for example made of titanium aluminide, and the disk, for example made of a nickel-based alloy, leads to premature wear of the blade roots and / or the cavities of the disk.

[0005] In order to limit the wear of the blade root and the cavity of the disk, it is known to place a contact element 30 (called an airfoil) at the contact interface (usually called a seat or support) between the blade root and the cavity of the disk. Typically, the airfoil is a profile of a movable blade mounted around the root 20 of said movable blade. This airfoil (referenced 30) is in contact with the disk and absorbs most of the energy dissipated by the contact friction between the movable blade root and the disk, thus limiting the wear of said blade root.

[0006] Figure 2 Shows Figure 1 FIG. 1 is an enlarged view of the root 20 of the movable blade 10, around which a conventional airfoil 30 is mounted. The airfoil 30 comprises two side branches 32 or side surfaces ( Figure 2 The airfoil 30 is formed with an overall U-shaped cross section (only one of which is visible) to cover the flanks 22 of the root 20 of the movable blade 10 and to hold the airfoil 30 on the blade root 20. The airfoil 30 also includes a base 31 (also called a lower surface) that connects the flank surfaces 32 together and covers the lower surface 21 of the blade root 20.

[0007] The airfoil 30 thus has the function of protecting the blade root and the cavity of the disk by preventing wear of these parts. It thus guarantees the mechanical integrity of the parts with which it is in contact (blade root and disk).

[0008] In order to prevent the airfoil 30 from detaching from the blade root 20, the lower surface 31 of the airfoil generally comprises radial lugs 33 which bear on the upstream surface 23 and the downstream surface 24 of the root 20. The radial lugs 33 (at Figure 2 The radial lugs 33 (only one of which is visible here) are strips cut out at the end of the lower surface 31 and folded radially downward along the upstream surface 23 and downstream surface 24 of the blade root 20. These radial lugs 33 extend to a greater or lesser width between the lateral branches 32 of the airfoil and form stops that make it possible to prevent relative axial movements between the blade root 20 and the airfoil 30.

[0009] However, despite the presence of the radial lugs 33, turbine maintenance operators have noticed that the airfoil tends to move axially, thus damaging or even shearing off the radial lugs 33. In fact, the radial lugs are weakened by being radially folded during the manufacturing phase and / or unfolded during the installation phase, and the friction generated by the repeated axial movement of the airfoil has the effect of shearing off or breaking off the radial lugs. Figure 3 As shown, once the radial lugs are broken off, the airfoil 30 may be partially or even completely detached from the blade root 20 .

[0010] The detachment of one (or more) airfoils 30 may cause the airfoils to be released into the airflow of the turbine and damage the blades located downstream of the low-pressure turbine, in particular titanium aluminide (TiAl) based blades which are particularly sensitive to shocks. The detachment of airfoils 30 may also lead to greater wear between the blade root 20 and the disk 40, since the protective parts are no longer present and the mechanical strength of these parts in this area is therefore reduced.

[0011] This leaf-type detachment is caused and maintained by a combination of two factors:

[0012] - the mechanical strength of the airfoil is insufficient and cannot withstand the stresses that occur between the blade root and the disk during operation, and

[0013] -Thermal loads generated by the series of thermal expansions / contractions experienced by the blade root and the disk during the operating cycle. In fact, with the successive rise and fall of the temperature of the blade root, the airfoil also expands and contracts, causing damage and partial and then total degradation.

[0014] During maintenance, the detachment of one or more airfoils results in the removal of the rotor for repair. However, removal and repair of the rotor involves considerable parts and labor costs, as well as downtime of the turbine.

[0015] Furthermore, it has been noted that there is an unfortunate wear of the edges of the disks on the downstream surface of the teeth of the disks. In practice, the downstream axial stop of the blade root 20 is usually achieved by inserting a retaining ring into a hook on the blade. A cross-sectional view of a blade root 20 mounted in a cavity 41 of a disk 40 is shown in Figure 4 Shown in. Figure 4 This view of shows a disk 40 in which the roots 20 of the movable blades 10 are housed. This figure also shows the hooks 15 of the movable blades 10 protruding on the downstream surface and into which a retaining part called a retaining ring 50 slides. The retaining ring 50 extends annularly along the downstream surface of the disk 40 so as to retain all the blade roots 20 in the cavity of the disk and prevent any axial downstream movement of said blade roots.

[0016] Thus, the retaining ring 50 is in contact not only with the downstream surface of the blade root 20, but also with the downstream edge 46 of the disk 40 at the teeth of the disk. Figure 5 As shown, this contact between the retaining ring 50 and the downstream edge of the teeth of the disk creates a fretting wear zone 48. Each fretting wear zone 48 leads to the risk of crack initiation and propagation, which has a real impact on the service life of the disk. In maintenance, cracks caused by fretting lead to premature removal of the disk and subsequent repair or replacement of the disk. However, removal and repair or replacement of the disk involves considerable parts and labor costs, as well as downtime of the turbine. Summary of the invention

[0017] In response to the problems of detachment of movable blade airfoils and fretting of the edges of the disk discussed above, the applicant provides an airfoil for a turbine disk, the airfoil being positioned at least partially around the teeth of the disk and extending, on the one hand, along the edge of the disk and, on the other hand, between the sidewall of the cavity of the disk and the root of the movable blades.

[0018] According to a first aspect, the invention relates to an airfoil for a turbine disk of a turbine, the airfoil comprising a casing at least partially surrounding a tooth of the turbine disk, the tooth separating a first chamber and a second chamber of the disk, the first chamber and the second chamber each being suitable for receiving a root of a movable blade of the turbine, characterised in that the casing is suitable for at least partially covering: a side wall of the tooth, and a downstream edge of the tooth.

[0019] The airfoil according to the invention has the advantage of protecting not only the contact area between the blade root and the cavity of the disk, but also the contact area between the retaining ring and the edge of the disk. The airfoil also avoids the risk of the airfoil detaching.

[0020] The use of the blade profile according to the invention in a turbomachine makes it possible to limit the number of engine disassemblies, to reduce the number of parts to be replaced during engine disassembly, and thus to reduce the maintenance costs of the turbomachine. The blade profile also makes it possible to extend the service life of the turbine and improve flight safety.

[0021] In the present application, the terms "lower", "upper", "inner" and "outer" are to be interpreted with reference to the position of a part or surface relative to the axis of rotation of the turbine, the lower surface or inner surface being closer to the axis of rotation than the outer surface or outer surface. The term "side" is to be interpreted as "the side of the part located along an axis extending radially along an axis substantially perpendicular to the axis of rotation X". The term "axial" is to be interpreted as "in the direction of the axis of rotation", while the term "radial" is to be interpreted as "in a direction perpendicular to the axis of rotation" or "in the radius direction of the blade ring". The terms "upstream" and "downstream" are to be interpreted with reference to the flow direction of the gas flow in the turbine.

[0022] In addition to the features discussed immediately in the previous paragraph, the airfoil for a turbine disk according to one aspect of the invention may have one or more complementary features of the following features, considered alone or in any technically possible combination:

[0023] According to one example, the profile completely covers circumferentially a portion of the downstream edge of the tooth radially defined between the apex of the tooth and a tangent passing through a plane parallel to the axis x through the end of the seat of the tooth opposite the apex.

[0024] According to one example, the profile comprises two lateral longitudinal edges each extending into the zone covered by the main surface adapted to cover the outer surface of the tooth of the disk. According to one example, the two lateral longitudinal edges are parallel and at a distance from each other that is less than the circumferential width of the main surface. The two lateral longitudinal edges connect the outer surface of the profile and the inner surface of the profile adapted to face the tooth.

[0025] The airfoil comprises: a main surface adapted to cover the outer surface of the tooth of the disk; a first side surface and a second side surface extending from the main surface to cover the side wall of the tooth of the disk; and a downstream surface extending between the main surface and the side surface to at least partially cover the downstream edge of the tooth of the disk.

[0026] The airfoil comprises at least one lug extending radially along the upstream edge of the tooth of the disk.

[0027] The airfoil comprises two lugs extending radially along the upstream edge of the tooth of the disk and distributed along this upstream edge.

[0028] One or more lugs are formed as extensions of the main surface and are folded along the upstream edge.

[0029] The airfoil comprises a substantially C-shaped cross section, wherein the body of the C covers the outer surface of the tooth of the disc and the two arms of the C cover the side walls of the tooth of the disc.

[0030] - The housing is formed from sheet metal.

[0031] A second aspect of the invention relates to an assembly for a turbine rotor, the assembly comprising:

[0032] at least a first movable blade and a second movable blade, the first movable blade and the second movable blade being configured to be rotatably movable about the rotation axis of the rotor and the first movable blade and the second movable blade each comprising a blade root provided with a lower surface and two side wings extending on both sides of the lower surface,

[0033] - a disk comprising at least

[0034] - a first cavity and a second cavity, the first cavity and the second cavity each being adapted to receive a blade root, and

[0035] - a tooth separating the first chamber and the second chamber, and

[0036] - A blade profile according to an aspect of the invention.

[0037] Advantageously, the first side surface of the airfoil is accommodated between one of the side walls of the tooth of the disk and the flank of the blade root of the first movable blade, and the second side surface of the airfoil is accommodated between the other of the side walls of the tooth of the disk and the flank of the blade root of the second movable blade.

[0038] A third aspect of the invention relates to a method for installing an assembly for a turbine rotor according to the second aspect. The method is characterized in that the method comprises the following steps:

[0039] - positioning a profile according to the first aspect of the invention around a tooth of the disk such that the profile covers at least the side walls and the downstream edge of the tooth of the disk,

[0040] - folding at least one lug so as to position it along the upstream edge of the tooth of the disc, and

[0041] - installing a first blade root into the first cavity of the disk and a second blade root into the second cavity so that a portion of the airfoil is positioned between the first blade root and one of the side walls of the tooth of the disk and another portion of the airfoil is positioned between the second blade root and the other of the side walls of the tooth of the disk.

[0042] A fourth aspect of the present invention relates to a turbine rotor, characterized in that the turbine rotor comprises a plurality of assemblies as defined above, the plurality of assemblies being annularly juxtaposed to one another.

[0043] A fifth aspect of the invention relates to a turbomachine, characterised in that it comprises a plurality of assemblies as defined above, which are mounted so as to form a rotor. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Further advantages and features of the present invention will become apparent from reading the following description illustrated in the accompanying drawings, in which:

[0045] Figure 1 (already described) shows a schematic perspective view of a movable blade of a turbine according to the prior art;

[0046] Figure 2 (already described) shows a schematic perspective view of a movable blade root equipped with a blade profile according to the prior art;

[0047] Figure 3 (already described) schematically shows a perspective view of a broken blade profile in the process of being separated from the blade root;

[0048] Figure 4 (already described) schematically shows a radial cross-sectional view of a blade root mounted into a disc chamber and held in place by a retaining ring;

[0049] Figure 5 (already described) schematically illustrates a perspective view of a portion of a disc edge prematurely worn by contact with a retaining ring;

[0050] Figure 6 schematically shows a perspective view of a disc tooth equipped with an airfoil according to one embodiment of the invention when the blade root is installed in a cavity adjacent to the tooth;

[0051] Figure 7 A perspective view schematically shows an airfoil for a turbine disk according to a preferred embodiment of the present invention;

[0052] Figure 8 schematically shows a view from upstream of an airfoil mounted to a tooth of a turbine disk according to one embodiment of the present invention; and

[0053] Fig. 9 A view from downstream of an airfoil mounted to a tooth of a turbine disk according to an embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0054] An exemplary embodiment of an airfoil for a turbine disk, which is configured to protect both the edge of the disk and the blade root without the risk of detachment, will be described in detail below with reference to the accompanying drawings. This example illustrates the features and advantages of the present invention. However, it should be noted that the present invention is not limited to this example.

[0055] In the figures, identical elements are identified by identical reference numerals. For reasons of legibility, the size ratios between the various elements represented are not adhered to.

[0056] The turbine rotor comprises a disk and a plurality of movable blades, each movable blade being held by its root in a cavity in the disk. The root of each blade is housed in a cavity in the disk. Figure 6 An example of a disc chamber is shown in a three-dimensional view. Each honeycomb-shaped chamber 41 of the disc 40 (in Figure 6 The dovetail roots 20 of the movable blades 10 of the rotor (not shown, but visible) are usually arranged in the outer periphery of the disk 40. Each chamber 41 is separated from the adjacent chamber by teeth 42 of the disk. Figure 6 The toothed member (represented only partially by the surface facing the tooth so that the tooth can be seen in three dimensions) is engaged in each cavity 41 and is radially held therein by a form fit between the root and the cavity.

[0057] The cavity 41 of the disk 40 comprises a bottom surface 43 and two side surfaces, each of which is formed by the side walls 44 of adjacent teeth 42. Thus, the teeth 42 of the disk 40 comprise two side walls 44 and an outer surface 45, a downstream edge 46 and an upstream edge 47 (in Figure 6 The downstream edge 46 and the upstream edge 47 are also referred to as the downstream radial surface or the upstream radial surface of the tooth, respectively.

[0058] Each blade root 20 comprises a lower surface 21 facing the bottom surface 43 of the cavity 41 , and two side wings 22 forming a contact interface between the blade root 20 and the disk cavity 41 .

[0059] When the rotor rotates, the movable blades are subjected to centrifugal forces; under the action of these centrifugal forces, the flanks 22 of the blade roots 20 come into a stop position against the side walls 44 of the teeth 42 of the disk 41 (or the side surfaces of the chambers 41). According to the invention, an airfoil 400 made of sheet metal (metal or alloy) is positioned around each tooth 42 of the disk 40 so as to surround at least the area to be protected. Thus, each airfoil 400 preferably covers at least the side wall 44 of the tooth 42 to which it is associated, as well as the downstream edge 46 of said tooth 42.

[0060] Figure 7 An example of an airfoil 400 according to a preferred embodiment is shown. Figure 8 An example of this airfoil 400 mounted on the teeth 42 of the disk 40 is shown in a perspective view from downstream. The airfoil 400 according to this preferred embodiment comprises:

[0061] a main surface 450 adapted to cover the outer surface 45 of the tooth 42,

[0062] a first and a second side surface 440 which covers the side wall 44 of the tooth 42 , and

[0063] A downstream surface 460 at least partially covering the downstream edge 46 of the tooth 42 of the disc.

[0064] The main surface 450 and the side surface 440 extend as extensions of each other, with the first side surface 440a extending from one side of the main surface 450 and the second side surface 440b extending from the other side of the main surface opposite to the first side surface. The main surface 450 and the side surface 440 have a C-shaped cross section, with the main body of the C formed by the main surface 450 and the two arms of the C formed by the two side surfaces 440a, 440b.

[0065] The downstream surface 460 extends radially along the downstream edge 46 of the tooth 42 between the two side surfaces 440a, 440b and the main surface 450, so that the assembly (main surfaces, side surfaces and upstream surface) has an overall shroud shape.

[0066] Therefore, in the case of such a shape of the airfoil 400, each winglet 22 of the blade root 20 is separated from the side wall 44 of the adjacent tooth 42 (or the side surface of the cavity 41) by the side surface 440 of the airfoil 400. In other words, the first side surface 440a of the airfoil 400 is positioned between the winglet 22 of one blade root 20 and one of the side walls 44 of the tooth 42, and the second side surface 440b of the airfoil 400 is positioned between the winglet 22 of another blade root 20 and the other of the side walls 44 of the tooth 42 of the disk 40, so that the two side walls of the tooth 42 and the winglet 22 of each adjacent blade root are protected from friction by contacting each other.

[0067] With the shape of the airfoil 400 described previously, the downstream edge 46 of the tooth 42 of the disk is covered by the downstream surface 460 of the airfoil 400. The downstream edge 46 is therefore not in direct contact with the retaining ring 50, allowing the blade root 20 to be axially stopped in the downstream direction, thereby protecting said downstream edge 46 from the risk of friction resulting from contact with said ring.

[0068] In one embodiment of the invention, the airfoil 400 comprises at least one lug 480 extending radially along the upstream edge 47 of the tooth 42 of the disk, in order to lock the positioning of said airfoil around the tooth 42. An example of this embodiment is shown in Fig. 9 4 is shown in a perspective view from upstream. The lug 480 is formed from the same metal sheet as all the airfoils 400 by cutting the sheet. The lug 480 extends from the end of one surface of the airfoil 400 (for example, from the main surface 450 or from the side surface 440) and is folded back along the edge 47 of the tooth 42. Fig. 9 In the example of FIG. 4 , the lug 480 extends as an extension of the main surface 450 . When the lug 480 is folded back, the lug 480 extends in a radial plane relative to the upstream edge 47 , ensuring that the airfoil 400 is axially retained around the tooth 42 .

[0069] According to some embodiments, airfoil 400 includes a plurality of lugs 480 (eg, Fig. 9 ), which are all folded back along the upstream edge 47. When there are several lugs 480, these are preferably distributed around the contour of the upstream edge 47 so as to keep the airfoil profile optimally around the tooth 42.

[0070] For example, the airfoil 400 as described above is manufactured by folding or drawing a metal sheet. One or more lugs are made by cutting the metal sheet. These lugs are folded only when the airfoil has been correctly positioned on the teeth 42 of the disk.

[0071] In practice, once the airfoil 400 has been manufactured, it is mounted to the tooth 42 of the disk by sliding along the outer surface 45 and the side wall 44 of said tooth from downstream to upstream. In other words, the airfoil 400 slides axially around the tooth 42 of the disk. The airfoil is in place when its downstream surface 460 comes into contact with the downstream surface 46 of the tooth 42. The airfoil 400 then covers the side wall 44, the outer surface 45 and the downstream surface 46 of the tooth 42 of the disk. When present, the lug 480 is then folded radially downwards along the upstream surface 47 of the tooth 42 so as to block the airfoil around the tooth 42. The two blade roots 20 can then each be mounted in one of the chambers 41 adjacent to the tooth 42. The side surfaces 480a, 480b of the airfoil 400 are then each positioned in the chamber 41 between one of the blade roots of the tooth 42 and one of the side walls 44.

[0072] As can be understood from the above, unlike the prior art airfoils, the airfoil 400 according to the invention is mounted to the disk around the disk teeth and not around the blade roots. This mounting makes it possible to increase the mechanical strength of the airfoil without deforming or weakening it. It also protects the downstream edge of the disk, except for the contact area between the blade roots and the wall of the cavity 41 of the disk.

[0073] More generally, airfoil 400 can reduce costs by increasing the durability of rotor parts, avoiding potential engine removals due to premature fretting wear, reducing the number of parts replaced during engine removal, and reducing maintenance costs and the number of repair operations. Thus, the airfoil improves customer satisfaction and eliminates recurring problems.

[0074] Although described through a number of examples, alternatives and embodiments, the blade profile for a turbine disk and the assembly for a rotor according to the present invention include various alternatives, modifications and improvements, which are obvious to those skilled in the art and should be understood to be within the scope of the present invention.

Claims

1. An airfoil (400) for a turbine disk (40) of a turbine, the airfoil comprising a casing at least partially surrounding teeth (42) of the turbine disk (40), the teeth (42) separating a first chamber and a second chamber (41) of the disk, the first chamber and the second chamber each being adapted to receive a root (20) of a movable blade of the turbine, characterized in that The housing is adapted to at least partially cover: - each of the side walls (44) of the tooth (42), - a downstream edge (46) of said tooth (42).

2. The blade profile according to claim 1, characterized in that: The blade profile includes: - a main surface (450) suitable for covering the outer surface (45) of the teeth of the disc, - a first side surface and a second side surface (440a, 440b) extending from the main surface (450) so as to cover the side walls (44) of the teeth of the disc, and A downstream surface (460) extending between the main surface (450) and the side surface (440) so as to at least partially cover the downstream edge (46) of the tooth of the disc.

3. The blade profile according to claim 1 or 2, characterized in that: The airfoil comprises a lug (480) extending radially along the upstream edge (47) of the tooth (42) of the disk.

4. The blade profile according to claim 2 or 3, characterized in that: The airfoil comprises at least two lugs (480) extending radially along the upstream edge (47) of the tooth of the disk and distributed along the upstream edge.

5. The blade profile according to claim 2, 3 or 4, characterized in that: The lug (480) is formed as an extension of the main surface (450) and is folded along the upstream edge (47).

6. The blade profile according to any one of claims 1 to 5, characterized in that: The airfoil comprises a generally C-shaped cross section, wherein the body of the C covers the outer surface (45) of the tooth of the disk and the two arms of the C cover the side walls (44) of the tooth of the disk.

7. The blade profile according to any one of claims 1 to 6, characterized in that: The housing is formed from sheet metal.

8. An assembly for a turbine rotor, the assembly comprising: - at least a first movable blade and a second movable blade (10), the first movable blade and the second movable blade being configured to be rotatably movable about the axis of rotation (X) of the rotor and each comprising a blade root (20) provided with a lower surface (21) and two side wings (22) extending on either side of the lower surface, - a plate (40) comprising at least a first cavity and a second cavity (41), each of which is adapted to receive a blade root (20), and - teeth (42) separating said first chamber from said second chamber (41), and - An airfoil (400) according to any one of claims 1 to 7.

9. The assembly according to claim 8, characterized in that The first side surface (440a) of the airfoil is accommodated between one of the side walls (44) of the tooth (42) of the disk and the side wing (22) of the blade root of the first movable blade, and the second side surface (440b) of the airfoil is accommodated between the other side wall (44) of the side wall (44) of the tooth (42) of the disk and the side wing (22) of the blade root of the second movable blade.

10. A method for installing an assembly for a turbine rotor according to any one of claims 8 to 9, characterized in that The method comprises the following steps: - positioning a profile (400) according to any one of claims 1 to 7 around a tooth (42) of the disk (40) such that the profile covers at least the side wall (44) and the downstream edge (46) of the tooth of the disk, - folding at least one lug (480) so as to position said at least one lug along said upstream edge (47) of said tooth of said disc, and - Mounting the root (20) of the first movable blade in the first cavity (41) of the disk and mounting the root (20) of the second movable blade in the second cavity (41) so that a portion of the airfoil (400) is positioned between the root of the first movable blade and one of the side walls (44) of the tooth of the disk and another portion of the airfoil (400) is positioned between the root of the second movable blade and the other of the side walls (44) of the tooth of the disk.

11. A turbine rotor, characterized in that: The turbine rotor comprises a plurality of assemblies according to any one of claims 8 and 9, the plurality of assemblies being annularly juxtaposed to one another.

12. A turbine, characterized in that: The turbomachine comprises a plurality of assemblies according to any one of claims 8 and 9, which are mounted so as to form a rotor.

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