Sealing sector for turbomachine

Abstract

A sealing sector (38) for a turbomachine is proposed, intended to be arranged around an annular row of moving blades, comprising a support sector (40) supporting on a first face a block of abradable material (44) and having on a second face opposite the first face a circumferential groove (46) delimited longitudinally by a first circumferential surface (48) and a second circumferential surface (50) extending between a first circumferential end and a second circumferential end of the support sector (40), in which at least one shim (60, 62, 64, 68, 72, 74) is mounted in the circumferential groove (46) and has at least one tab (60b, 62b, 64b, 68b, 72b, 74b) projecting radially outwards and applied against the first circumferential surface (50) of the circumferential groove (46) of the support sector (40). Figure from the abstract: Figure 3

Description

Title of the invention: Sealing sector for turbomachinery technical field

[0001] The present disclosure falls within the field of blade tip sealing devices, in particular in a turbomachine turbine. Previous technique

[0002] Figure 1 illustrates a portion of a turbomachine turbine 10, and more particularly of a low-pressure turbine of a turbomachine extending along a longitudinal axis. As is known, a turbine such as a low-pressure turbine comprises alternating annular rows of moving blades arranged alternately with annular rows of stator blades and surrounded externally by a turbine housing. Figure 1 illustrates more particularly the sealing interaction between a radially external end of an annular row of moving blades and an abradable ring 28.

[0003] An annular row of movable blades comprises a plurality of movable blades 30 each having blades 32 carrying at their radially external ends annular scrapers 34 cooperating to seal by friction with the abradable ring 28 carried by a support ring 22 carried by the housing 12. The assembly formed by the abradable ring 28 and the support ring 22 constitutes a sealing element 20 (which can in particular be what is typically called a sealing ring).

[0004] The turbine housing 12 10 comprises an outer casing 13 carrying a plurality of annular lugs 14, 16, of which only two lugs, one upstream 14 and the other downstream 16, are illustrated in [Fig. 1]. The upstream annular lug 14 comprises a radial annular wall 14a connected in its mid-portion to the upstream end of a hooked portion formed by a cylindrical wall 14b, the downstream end of which is connected to a radial annular wall 14c extending radially inwards.

[0005] The downstream annular leg 16 comprises a cylindrical wall 16b connected at an upstream end to a radial wall 16a, the radially external end of which is connected to the casing 13 of the housing 12. The support ring 22 comprises a C-shaped member 21 at its upstream end engaged on the upstream leg 14 of the housing 12 and on a retaining ring 17 of the annular platform 18 of the upstream annular row of stator blades, the retaining ring 17 allowing the annular row of stator blades to be held in a longitudinal position within the housing. The support ring 22 comprises a downstream annular groove 24 formed on its radially external face, the downstream annular leg 16 of the housing 12 being engaged in the annular groove 24. The annular groove 24 comprises a wall upstream annular wall 24a and a downstream annular wall 24b connected to each other by a bottom cylindrical wall 24c.

[0006] The upstream end of the external annular platform of the downstream annular row of stator blades includes a C 36 member engaged longitudinally and retained radially on the downstream annular lug 16 of the housing 12.

[0007] As can be seen in [Fig. 2], the downstream annular wall 24b of the groove 24 extends into two radial tabs 26. These radial tabs 26 provide longitudinal locking downstream of the downstream annular tab 16 of the housing 12.

[0008] During operation, the tabs 26 are subjected to friction with the downstream annular tab 16, which can lead to wear of the tabs 26. As a result, longitudinal play can form between the downstream annular tab 16 and the tab 26, leading to a loose fit of the sealing element 20 on the downstream annular tab 16 of the housing 12. This play can also lead to breakage of the tab 26 in the long term.

[0009] Repairing the sealing element 20 proves complicated and it may be necessary to replace the entire sealing part 20 (the sealing element) or at least one of the sectors 22 that make up the sealing element 20. Summary

[0010] A sealing sector for a turbomachine is thus proposed, intended to be arranged around an annular row of moving blades, comprising a support sector supporting on a first face a block of abradable material and having on a second face opposite to the first face a circumferential groove delimited longitudinally by a first circumferential surface and a second circumferential surface extending between a first circumferential end and a second circumferential end of the support sector, in which at least one shim is mounted in the circumferential groove and has at least one tab projecting radially outwards and applied against the first circumferential surface of the circumferential groove of the support sector.

[0011] Such a sealing sector can be mounted in a turbine, for example a low-pressure turbine of a turbomachine. For example, a plurality of sealing sectors can be arranged circumferentially end to end so that the circumferential grooves together form an annular groove in which an annular lug of a turbine housing is mounted, said annular lug being locked longitudinally between the tab of each of said at least one shim and the second lateral walls of the support sectors.

[0012] Thus, potential wear of the sealing sector is shifted from the support sector to an intermediate piece, comprising said piece at least one shim. A piece of this type can be replaced easily and at a lower cost compared to changing an abradable support.

[0013] Advantageously, the support sector is also easier to produce, having only a simple circumferential groove for receiving said at least one wedge, instead of a complex shape such as is known in the prior art (described previously with reference to [Fig. 1] and 2).

[0014] Furthermore, different thicknesses of the shim are possible, particularly at the tab, which allows for optimal adjustment of a support sector on a turbine housing. Indeed, the use of an intermediate piece to provide support for the annular tab can compensate for manufacturing tolerances between the annular tab and the support sector.

[0015] Thus, an operator who mounts the support sector onto the annular tab of the housing may have at their disposal a set of shims of different nominal thicknesses. The operator can then choose a shim with a tab of sufficient thickness to allow the annular tab of the housing to be perfectly clamped between the second lateral wall and the tab of the shim. The shims may, for example, have a thickness ranging from 1 to several millimeters.

[0016] The wedge may include a bottom wall extending at least partially between the first circumferential surface and the second circumferential surface of the circumferential groove. This bottom wall provides part of the radial bearing of the lug on the support and thus transfers some of the wear to it.

[0017] Furthermore, this bottom wall provides better support for the annular lug of the housing. The support of the downstream annular lug on the bottom wall minimizes movement of the support sector and thus ensures better retention of the sealing sector, as it is blocked radially and axially by the same component formed by the shim.

[0018] In particular, the bottom wall can extend from the first circumferential surface to the second circumferential surface. In this configuration, all the wear is transferred to the bottom wall, the bottom wall of the circumferential groove of the support sector remaining intact.

[0019] In a particular embodiment, the bottom wall of the wedge extends only over part of the distance between the first lateral wall and the second lateral wall of the circumferential groove, which makes it possible to limit the deformation of the wedge and thus increase its lifespan.

[0020] In embodiments, the bottom wall of said at least one wedge is housed in a groove on the bottom surface of the circumferential groove of the support sector. The groove may be dimensioned to allow a tight fit of the wedge within it.

[0021] In embodiments, the sealing sector may comprise a single wedge extending circumferentially from the first circumferential end of the support sector to the second circumferential end of the support sector.

[0022] In other embodiments, said at least one wedge comprises at least two separate wedges, a first of which is arranged in the vicinity of the first circumferential end of the support sector and a second of which is arranged in the vicinity of the second circumferential end of the support sector.

[0023] Furthermore, in a particular configuration, each wedge can be arranged so that a circumferential face is aligned with a circumferential lateral face of the support sector.

[0024] Depending on the materials chosen, for reasons of rigidity or weight saving for example, the use of two separate shims may be preferred.

[0025] According to another feature, at least one cavity can be formed between a circumferential end of said at least one wedge and a circumferential end of the support sector.

[0026] Positioned in this way, the cavity forms a gripping area for a suitable tool, allowing the wedge to be separated from the support sector. For example, a simple flathead screwdriver and a hammer can be used to extract the wedge if the support sector is held securely. The end of the tool can be inserted into the cavity between the wedge and the support sector.

[0027] In this configuration, the cavity may have a radial cross-section that is triangular. Placing the cavity at a circumferential end may allow easier access for an operator.

[0028] Said at least one wedge may include at least one cavity opening to the outside of said sealing sector.

[0029] Said at least one wedge can be fixed in the circumferential groove of the support sector by brazing or shrink fitting or by form cooperation.

[0030] Said at least one shim may have a lower density than that of the support sector, so as to lighten the fixing of the sealing element to the housing.

[0031] According to one aspect, said at least one wedge may be made of metal.

[0032] According to another aspect, a turbine is proposed, such as a low-pressure turbine of a turbomachine extending around an axis, comprising a plurality of sealing sectors according to the aforementioned type, said sealing sectors being arranged circumferentially end to end so that the circumferential grooves form an annular groove in which is mounted an annular lug of a turbine housing, said annular lug being locked longitudinally between the tongue of each of said at least one shim and the second lateral walls of the support sectors.

[0033] According to another aspect, a turbomachine, such as a turbojet or a turboprop, is proposed, comprising a turbine as described above. Brief description of the drawings

[0034] Other features, details and advantages will become apparent from reading the detailed description below and from analyzing the accompanying drawings, in which: Fig. 1

[0035] [Fig.l], described previously, is a longitudinal cross-sectional view of part of a low-pressure turbine of a turbomachine according to the prior art; Fig. 2

[0036] [Fig.2], described above, is a schematic perspective representation of a sealing element used in the turbine illustrated in [Fig.1]; Fig. 3

[0037] [Fig.3] is a schematic perspective representation of a sealing element according to this document; Fig. 4

[0038] [Fig.4] illustrates in part A the sealing element of [Fig.3], and on which is mounted a wear shim and in part B a longitudinal cross-sectional view of figure 4A at the level of one end of the shim; Fig. 5

[0039] [Fig.5] illustrates a variant embodiment of the wear shim of [Fig.4]; Fig. 6

[0040] [Fig.6] is a schematic perspective representation of a sealing element featuring two wear shims at its circumferential ends; Fig. 7

[0041] [Fig.7] is a schematic perspective representation of one end circumferential of a wedge, with an edge without a cavity in part A and with a cavity in part B; Fig. 8

[0042] [Fig.8] is a schematic perspective representation of the form cooperation between a wedge and a support sector; Fig. 9

[0043] [Fig.9] comprises a part A representing a wedge having a tongue of a first longitudinal dimension dl and a part B representing a wedge having a tongue of a second longitudinal dimension d2 greater than dl. Description of the implementation methods

[0044] Reference is now made to figures 3 to 9 illustrating a sealing sector.

[0045] [Fig.3] represents a sealing element 38 intended for use in a turbine as described with reference to [Fig.1]. The sealing element 38 comprises a support sector 40 including a C-shaped member 42 at its upstream end and carrying on its radially internal face a block of abradable material 44 intended to cooperate with annular blades of an annular row of moving blades.

[0046] The support sector 40 includes a circumferential groove 46 extending between the two circumferential ends of the support sector 40. The circumferential groove 46 includes a first circumferential face 48 and a second circumferential face 50 substantially radial and extending from a first circumferential end of the support sector 40 to a second circumferential end of the support sector 40. In other words, the circumferential groove 46 opens at its circumferential ends. A bottom surface 52 connects the first circumferential surface 48 and the second circumferential surface 50. When a plurality of support sectors 40 are arranged circumferentially end to end, the circumferential grooves 46 of the sectors together form an annular groove for receiving an annular tab of the housing as illustrated with reference to [Fig.5] representing two variant embodiments of the invention.

[0047] According to the present document, at least one shim 60 is mounted in the circumferential groove 46 of the support sector 40. In the embodiment of [Fig. 4], a single shim 60 is mounted in the circumferential groove 46 and extends circumferentially from the first circumferential end of the support sector 40 to the second circumferential end of the support sector 40. In other words, the shim 60 opens at the circumferential ends of the circumferential groove 46.

[0048] As can be seen in [Fig.4], the wedge 60 is advantageously housed in a groove 54 of the support sector 40. The groove 54 is formed in the circumferential groove 46 and more particularly in the bottom surface 52. The groove 54 has a first circumferentially radial surface coinciding with the first circumferential surface 48 of the circumferential groove 46 and a second circumferentially radial surface 54a which is formed longitudinally between the first circumferential surface 48 and the second circumferential surface 50 of the circumferential groove 46.

[0049] The wedge 60 comprises a cylindrical wall or bottom wall 60a which is connected at its downstream end to at least one tab 60b projecting radially outwards. In the example shown in [Fig. 4], the wedge 60 comprises two tabs 60b arranged near its circumferential ends. Said at least one tab 60b is dimensioned so as to extend radially outwards from the radially external end of the first circumferential surface 48 of the circumferential groove 46. Thus, the support sector 40 used in combination with the wedge 60 no longer requires the presence of tabs. Each tab 60b has a first circumferential downstream face substantially radial bearing on the first circumferential surface of the circumferential groove and a second circumferential upstream face substantially radial opposite to the first circumferential downstream face.

[0050] According to this document, a shim 60 is therefore mounted in the circumferential groove 46 and more particularly in a groove 54 of the bottom surface 52 of the support sector 40. The annular tab 16 is mounted in the circumferential groove 46 of the support sector 40 such that its upstream end is blocked upstream by the second circumferential surface 50 of the circumferential groove 46 and its downstream end is blocked by at least one tab 60b of the shim. The bottom wall 60a of the shim is radially interposed between the cylindrical wall 16b of the annular tab 16 of the housing and the bottom surface 52 of the groove 46.

[0051] In this embodiment, it is observed that the bottom wall 60a of the wedge extends over only a portion of the distance between the first circumferential surface 48 and the second circumferential surface 50 of the circumferential groove 46. Furthermore, the radial dimension of the bottom wall 60a is less than the radial dimension of the groove 54, so that the annular tab 16 of the housing bears directly on the support sector 40. In another configuration, the radial dimension of the bottom wall 60a is substantially equal to the radial dimension of the groove, so as to achieve simultaneous bearing on the bottom wall of the wedge and the bottom surface of the support sector.

[0052] The bottom wall 52 of the wedge 60 extends from the first circumferential surface 48 of the groove 52 to the second circumferential surface 54a of the groove 54. The bottom wall 60a can be tightly mounted between said two circumferential walls of the groove 54 in order to ensure the locking of the wedge 60 on the support sector 40.

[0053] We now refer to [Fig. 5], which represents a variant embodiment of the wedge of [Fig. 4] and which is identical to it in every respect except for the bottom wall 62a of the wedge 62, which has a longitudinal dimension equal to the longitudinal dimension of the groove 46. Here again, the bottom wall 62a is dimensioned so as to be clamped in the groove 46 between the first and second circumferential surfaces 48, 50. In this configuration, the entire radially internal surface of the cylindrical wall 16b of the annular tab 16 of the housing is in contact with the bottom wall 62a of the wedge 62, which makes it possible to further limit the wear of the support sector 40 compared to the embodiment of [Fig. 4].

[0054] Figure 6 illustrates an embodiment in which the sealing element 38 comprises two separate shims 64, the first of which is arranged near the first circumferential end of the support sector and the second of which is arranged near the second circumferential end of the support sector. In this example, the two shims 64 are of the same dimensions. It would also be possible to have more than two shims with different dimensions. For example, it would be possible to have three shims evenly distributed circumferentially around the support sector 40.

[0055] As can be seen in [Fig. 6], the radial dimension of the bottom wall 64a is smaller than the radial dimension of the groove 55, so that the bearing of the annular housing tab is made directly on the support sector 40 to ensure maximum bearing surface. Thus, when this sealing element 38 is mounted in a turbomachine turbine as described with reference to [Fig. 5], the bearing of the radially inner end of the annular housing tab is made on the bottom surface 52 of the circumferential groove 46 rather than on the bottom wall 64a of the shims 64.

[0056] The wedges 64 of [Fig.6] could further extend longitudinally over the entire longitudinal dimension of the groove 46 in a manner similar to that illustrated in [Fig.5].

[0057] Figure 7 represents two possible conformations of a circumferential edge of the wedge in Figures 7A and 7B. In the first conformation, the circumferential edge of the wedge has an end face 63 which is radially aligned with an end face 65 of the support sector 40.

[0058] In the second conformation illustrated in Figure 7B, a cavity can be formed between a circumferential end of said at least one wedge 64 and a circumferential end of the support sector 40.

[0059] More particularly, the cavity is delimited by a circumferential end portion of the groove 55 opposite an inclined face 67 of a circumferential end of the bottom wall 64a of the wedge 64. As illustrated in Figure 7B, a radial section 66 of the cavity is triangular, delimited by a first edge 66a contained in the bottom surface of the groove 55, a second edge 66b contained in the inclined face 67 of the circumferential end of the bottom wall 64a of the wedge 64, and a third edge connecting the ends of the first and second edges opening onto the circumferential end 66c of the circumferential groove 46. The angle formed by the first and second edges 66a, 66b can be between 30 and 55°, for example, on the order of 45°. This cavity allows the insertion of a tool between the bottom surface of the groove 55 and the bottom wall 64a of the wedge 64 in order to facilitate the extraction of the wedge 64 from the support sector 40, in particular due to a tight fit of the wedge 64 in the support sector 40.

[0060] In another embodiment, not shown, said at least one wedge could include a cavity or recess, formed directly in the bottom wall, in order to perform the same function as described above, i.e. to withdraw the wedge from the support sector.

[0061] The shim 60, 62, 64 can be locked in the groove by other means such as brazing or welding. The shim 68 can also be fixed in the circumferential groove 46 of the support sector 40 by form cooperation ([Fig. 8]). Thus, the first and second circumferential surfaces of the groove 46 are no longer strictly radial but are shaped to define circumferential slots 70 allowing circumferential engagement and radial retention of the shim 68 on the support sector 40.

[0062] With reference to [Fig. 9], shims 72, 74 having tabs 72b, 74b of different thicknesses can be mounted in the circumferential groove 46. For example, for identical circumferential grooves 46 shown in Figures 9A and 9B, the tab 72b of the shim 72 shown in Figure 9A has a thickness d1 less than the thickness d2 of the tab 74b of the shim 74 shown in Figure 9B. Thus, it is possible to choose a shim having a tab of such thickness that it allows the annular housing tab to be perfectly tightened between the second side wall and the tab of the shim.

Claims

Demands

1. Sealing sector (38) for a turbomachine intended to be arranged around an annular row of moving blades, comprising a support sector (40) supporting on a first face a block of abradable material (44) and having on a second face opposite to the first face a circumferential groove (46) delimited longitudinally by a first circumferential surface (48) and a second circumferential surface (50) extending between a first circumferential end and a second circumferential end of the support sector (40), in which at least one shim (60, 62, 64, 68, 72, 74) is mounted in the circumferential groove (46) and has at least one tab (60b, 62b, 64b, 68b, 72b, 74b) projecting radially outwards and applied against the first circumferential surface (50) of the circumferential groove (46) of the support sector (40).

2. Sealing sector (38) according to claim 1, wherein the wedge (60, 62, 64, 68, 72, 74) comprises a bottom wall (60a, 62a, 64a, 68a, 72a, 74a) extending at least in part between the first circumferential surface (48) and the second circumferential surface (50) of the circumferential groove (46).

3. Sealing sector (38) according to claim 2, in which said bottom wall (60a, 62a, 64a, 68a, 72a, 74a) extends from the first circumferential surface (48) to the second circumferential surface (50).

4. Sealing sector (38) according to claim 2 or 3, wherein the bottom wall (60a, 62a, 64a, 68a, 72a, 74a) of said at least one wedge (60, 62, 64, 68, 72, 74) is housed in a groove (54, 55) of a bottom surface (52) of the circumferential groove (46) of the support sector (40).

5. Sealing sector (38) according to any one of claims 1 to 4, comprising a single wedge (60, 62) extending circumferentially from the first circumferential end (48) of the support sector (40) to the second circumferential end (50) of the support sector (40).

6. Sealing sector (38) according to any one of claims 1 to 4, wherein said at least one wedge (60, 62, 64, 68, 72, 74) comprises at least two separate wedges (64), the first of which is arranged in the vicinity of the first circumferential end of the support sector (40) and of which a second is arranged in the vicinity of the second circumferential end of the support sector (40).

7. Sealing sector (38) according to any one of claims 1 to 6, wherein at least one cavity is formed between a circumferential end of said at least one wedge (60, 62, 64, 68, 72, 74) and a circumferential end of the support sector (40).

8. Sealing sector (38) according to any one of claims 1 to 6, wherein said at least one wedge (60, 62, 64, 68, 72, 74) comprises at least one cavity opening outwards from said sealing sector (38).

9. Sealing sector (38) according to any one of claims 1 to 8, wherein said at least one shim (60, 62, 64, 68, 72, 74) is fixed in the circumferential groove (46) of the support sector (40) by brazing or shrink fitting or by form cooperation.

10. Sealing sector (38) according to any one of claims 1 to 9, said at least one wedge (60, 62, 64, 68, 72, 74) has a lower density than that of the support sector (40).

11. Turbine, such as a low-pressure turbine of a turbomachine extending about an axis (X), comprising a plurality of sealing sectors (38) according to any one of the preceding claims, said sealing sectors (38) being arranged circumferentially end to end so that the circumferential grooves (46) form an annular groove in which an annular tab (16) of a turbine housing is mounted, said annular tab (16) being locked longitudinally between the tongue (60b, 62b, 64b, 68b, 72b, 74b) of each of said at least one shim (60, 62, 64, 68, 72, 74) and the second side walls (50) of the support sectors (40).

12. Turbomachine, such as a turbojet or turboprop, comprising a turbine according to claim 11.

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