TURBINE SEAL

Abstract

An assembly for a multistage turbine of a turbomachine has a static sealing device and a nozzle with a radially outer end and an outer casing surrounding the nozzle. The static sealing device is arranged radially between a radially outer end of the nozzle and the outer casing. The static sealing device includes an annular seal borne by the nozzle and an annular structure that defines a plurality of radial annular walls. The walls are axially spaced apart from one another, and at least one first wall is in annular contact radially inwardly with the annular seal. A longitudinal dimension of the annular contact is less than a longitudinal dimension of the seal.

Claims

1. An assembly for a multistage turbine of a turbomachine, the assembly comprising a static sealing device, a nozzle comprising a radially outer end and an outer casing surrounding the nozzle, the static sealing device being arranged radially between a radially outer end of the nozzle and the outer casing, and comprising an annular seal borne by the nozzle and an annular structure defining a plurality of radial annular walls axially spaced apart from one another, at least one first wall of said radial annular walls being in annular contact radially inwardly with the annular seal and having a longitudinal dimension that is less than a longitudinal dimension of the seal.

2. The assembly according to claim 1, wherein the annular seal is in annular linear contact with said at least one first radial annular wall of the annular structure.

3. The assembly according to claim 1, wherein the annular structure has a hollow shape comprising at least two radial annular walls, wherein spacing of the at least two radial annular walls in a longitudinal direction is less than the longitudinal dimension of the seal.

4. The assembly according to claim 1, wherein the nozzle comprises a radial annular portion having an annular groove opening radially outwards and receiving said annular seal.

5. The assembly according to claim 1, wherein the annular seal comprises at least two rings.

6. The assembly according to claim 5, wherein each of the at least two rings is in annular linear contact with at least one radial annular wall of the annual structure.

7. The assembly according to claim 1, wherein the annular structure has a plurality of cavities opening radially inwards formed at least in part by the radial annular walls of the annular structure.

8. The assembly according to claim 7, wherein each of the cavities has a hexagonal shape.

9. The assembly according to claim 7, wherein the longitudinal dimension of the seal is greater than or equal to half the longitudinal dimension of one of the plurality of cavities.

10. The assembly according to claim 7, wherein the longitudinal dimension of the seal is greater than or equal to the longitudinal dimension of one of the plurality of cavities.

11. The assembly according to claim 1, wherein the annular structure is formed of several structurally independent sectors arranged circumferentially end to end.

12. The assembly according to claim 1, wherein the annular seal comprises two rings arranged longitudinally in abutment against each other.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0055] FIG. 1 shows a partial sectional view of a turbomachine turbine according to the prior art;

[0056] FIG. 2 shows a sectional view of a turbomachine turbine according to the invention;

[0057] FIG. 3A is a sectional view of the contact area between the seal and the annular structure;

[0058] FIG. 3B is a sectional view of two radial annular walls intended to be brazed together.

[0059] FIG. 4A is a sectional view of the contact area between the seal and the annular structure;

[0060] FIG. 4B is a sectional view at the contact area between the rings forming the seal and the annular structure.

DETAILED DESCRIPTION

[0061] FIG. 1, showing a sealing device according to the prior art arranged inside a turbomachine turbine 10, was described earlier.

[0062] FIG. 2 shows a turbine comprising a sealing device according to the invention.

[0063] The nozzle 22 has a radially outer platform 20 at its radially outer end. From the radially outer platform 20, an annular projection 50 extends radially outwards. The annular projection 50 has a connecting area 52 from which radial upstream and downstream annular walls 54, 56 extend parallel to each other radially outwards.

[0064] The upstream and downstream radial annular walls 54, 56 and the connecting area 52 of the projection 50 form an annular groove 58. The upstream and downstream radial annular walls 54, 56 define flanks of the annular groove while the connecting area 50 defines a bottom of the groove 58. The annular groove 58 receives the annular seal 44. The annular seal 44 is arranged in the groove so that a portion of it protrudes radially from the radially outer ends of the upstream and downstream radial annular walls 54, 56 defining the groove 58.

[0065] The annular seal 44 has an upstream longitudinal surface abutting the upstream radial annular wall 54 of the groove 58 and a downstream longitudinal surface abutting the downstream radial annular wall 56 of the groove 58. These longitudinal stops of the seal 44 allow the annular seal 44 to be held in position without having to be radially in abutment with the bottom of the groove 58.

[0066] The radially outer end of the projecting annular seal 44 radially abuts a radially inner surface of an annular structure 60 attached to the outer casing 16 of the turbine 10.

[0067] The outer casing 16 has an annular groove 62 with a bottom 64 and two flanks opening radially. The groove 62 opens radially inwards opposite to the groove 58 of the nozzle 22. The groove 62 of the outer casing 16 receives the annular structure 60 which is attached to the bottom wall 64 of the groove 62 by means of an annular cylinder 66.

[0068] The attachment of the annular structure 60 to the bottom wall 64 of the groove 62 formed on the outer casing 16 can be carried out by brazing.

[0069] The annular structure 60 thus has an annular cylindrical wall 66, from which a plurality of radial annular walls 68 extend. The radial annular walls 68 of the annular structure 60 are longitudinally spaced from each other.

[0070] In another embodiment, the radial annular walls 68 of the annular structure 60 could be directly formed by laser fusion on the bottom wall 64 of the groove 62.

[0071] The radially outer end of the seal 44 is radially in abutment with a radially inner end of at least one of the radial annular walls 68 of the annular structure 60. The contact between the seal 44 and a radial annular wall 68 of annular structure 60 is annular and continuous.

[0072] In one embodiment, illustrated in FIGS. 3A, 4A and 4B, the radial annular walls 68 have common wall sections 70. The common wall sections 70 are circumferentially spaced from each other.

[0073] The radial annular walls 68 with common sections 58 form cavities 72. The annular structure 60 thus has a honeycomb structure 74 formed by the plurality of radial annular walls 68.

[0074] The plurality of cavities 72 has a hexagonal structure.

[0075] In a different design, the 72 cavities could be triangular, square, rectangular or octagonal in shape.

[0076] FIG. 3B shows two longitudinally adjacent radial annular walls 68a, 68b of the annular structure 60 obtained by stamping a sheet metal. These longitudinally adjacent radial annular walls 68a, 68b have wall portions intended to be welded or brazed together at the common sections 70.

[0077] In an alternative embodiment, the radial annular walls 68 of the annular structure 60 are obtained by additive manufacturing.

[0078] As shown in FIG. 3A, the annular seal 44 is arranged annularly in contact with the radially inner end of a radial annular wall 68. The longitudinal dimension of the annular seal 44 shall be sufficient to come into radial contact at the upstream and downstream ends of the radial annular wall 68 with which it is in contact.

[0079] In an alternative embodiment, the spacing in a longitudinal direction between two longitudinally adjacent radial annular walls 68a, 68b is less than the longitudinal dimension of the annular seal 44. In this way, the annular seal 44 makes annular contact with the radially inner ends of the two longitudinally adjacent walls 68a, 68b.

[0080] If the annular structure 60 has a honeycomb structure 74, the longitudinal dimension of the ring joint 44 shall be at least half the longitudinal dimension of a cavity 72. In this way, by precise positioning of the radial annular walls 68 of the annular structure 60 and of the groove 58 receiving the annular seal 44, annular contact of the seal with at least one of said radial annular walls 68 is ensured.

[0081] If the longitudinal dimension of the annular seal 44 is greater than the longitudinal dimension of a recess 72, then precise positioning of the radial annular walls 68 of the annular structure 60 and of the groove 58 receiving the annular seal 44 is not necessary to ensure annular contact between the annular seal and at least one of the radially inner ends of the radial annular walls 68 of the annular structure 60.

[0082] In particular, as shown in FIG. 4A, if the longitudinal dimension of the annular seal 44 is greater than the longitudinal dimension of the cavities 72, then the annular seal 44 can make annular radial contact with the radially inner ends of two adjacent radial annular walls 68a, 68b.

[0083] In one embodiment, illustrated in FIGS. 2 and 4B, the annular seal 44 has two rings 76a, 76b longitudinally abutting each other. These rings are preferentially split. The first ring 76a has an upstream end in longitudinal abutment with the upstream annular wall 54 of the annular groove 58 of nozzle 22 and a downstream end in longitudinal abutment with the upstream end of the second ring 76b. The downstream end of the second ring 76b is in longitudinal abutment with the downstream radial annular wall 56 of groove 58 of nozzle 22.

[0084] Where the annular seal 44 has two rings 76a, 76b arranged longitudinally in abutment, it is advantageous that each of them has annular radial contact with one of the radial annular walls 68 of the annular structure 60.

[0085] The radial annular walls 68a, 68c in contact with the rings 76a, 76b forming the annular seal 44 are not necessarily longitudinally adjacent, as shown in FIG. 4B.

[0086] As described above, a ring 76a, 76b can have a longitudinal dimension greater than the longitudinal spacing between two longitudinally adjacent radial annular walls 68a, 68b.

[0087] In particular, a ring 76a, 76b can have a longitudinal dimension greater than or equal to half the longitudinal dimension of a cavity 72 or the longitudinal dimension of a cavity 72.

[0088] Preferably, the annular seal 44 or each ring 76a, 76b is annularly in contact with the radially inner end of a radial annular wall 68 of annular structure 60.

[0089] Advantageously, the contact between the annular seal 44 or one of the rings 76a, 76b forming part of an annular seal 44 and a radial annular wall 68 is linear, so as to allow the contact area between them to be reduced.

[0090] The reduced contact surface makes it easier to check the contact surface of the annular seal 44 and to limit the presence of leakage paths. Thus, the sealing between the nozzle 22 and the outer casing 16 of the turbine 10 is ensured.

[0091] In addition, the reduced contact surface reduces the heat conduction between the nozzle 22 and the outer casing 16 efficiently.

[0092] Finally, the absence of discontinuity in the contact between the annular seal 44 and at least one of the radial annular walls 68 of the annular structure 60 prevents the reduction in the performance of turbine 10 and reduces the heating of the outer casing 16 and the surrounding parts.

[0093] The said annular structure 60 is preferably composed of a plurality of structurally independent sectors arranged circumferentially in abutment. This sectorization of the annular structure 60 allows it to be arranged in the annular groove 62 of the outer casing 16 and to be fixed to the outer casing 16.