FR3112165A1 - Abradable sealing device - Google Patents

Abstract

The invention relates to an abradable device (16) for sealing between a rotor part and a stator part of a turbomachine extending along an axis, the device (16) comprising at least one first end (21), radially internal or external, and a second end (22) opposite the first end (21) and capable of cooperating with at least one wiper (15) of the rotor part or of the stator part, the device (16) comprising strips (19) assembled to each other by brazing and extending in a longitudinal direction, characterized in that at least one strip (19) comprises a first corrugated zone (23), located on the side of the first end (21 ) of the device (16) and a second flat zone (24) extending over the majority or the entire length of the strip (19), located on the side of the second end (22) of the device (16), the strips (19 ) being brazed to each other at the level of the first corrugated zone (23) only. Figure to be published with abstract: Figure 11

Description

Abradable sealing device

Technical field of the invention

The invention relates to an abradable sealing device between a rotor part and a stator part of a turbomachine, such as a turbojet or a turboprop. The turbomachine is for example intended to equip an aircraft.

State of the prior art

There illustrates a turbomachine 1 of the prior art. This comprises, from upstream to downstream in the direction of gas flow, a fan 2, a low-pressure compressor 3, a high-pressure compressor 4, a combustion chamber 5, a high-pressure turbine 6, a low-pressure turbine pressure 7 and a gas exhaust nozzle 8. The high-pressure compressor 4 and the low-pressure compressor 3 are respectively connected to a high-pressure turbine 6 and a low-pressure turbine 7 by a respective shaft 9 extending in the direction of a longitudinal axis X of the turbomachine 1.

The terms radial, axial and circumferential are defined with respect to the axis X of the turbomachine.

Each compressor stage 3, 4 is formed by an upstream moving wheel comprising an annular row of moving blades 10 inside an outer annular casing 11 and a downstream stator comprising an annular row of stationary blades 12 relative to the outer annular casing 11. Similarly, each turbine stage 6, 7 is formed by an upstream distributor comprising an annular row of fixed blades 12 relative to the outer annular casing 11 and a downstream impeller comprising an annular row of movable blades 10 inside the outer annular casing 11.

Each annular row of moving vanes 10 or stationary vanes 12 comprises an internal platform 13 and, optionally, an external platform 14 delimiting an annular stream of gas flow through the compressor 3, 4 or the turbine 6, 7.

As depicted in , in the case of a low-pressure turbine 7, the radially outer face of the outer platform 14 of each moving blade 10 comprises wipers 15 cooperating in sealing with an annular abradable element 16, mounted in an outer ring 17. In particular, the outer ring 17 of at least one stage of the turbine comprises a groove opening radially inwards, in which the abradable element 16 is mounted. The outer ring 17 is carried by the outer annular casing 11.

As depicted in , in the case of a compressor 4, the radially inner face of the inner platform 13 of each annular row of stationary vanes 12 comprises an annular groove receiving an abradable element 16 annular. The abradable element 16 cooperates in sealing with wipers 15 of the shaft 9 of the turbomachine 1.

Such a structure can also be applicable to the case of the turbine.

The abradable element 16 generally comprises a honeycomb structure, also called a honeycomb structure, into which the wipers 15 penetrate due to differential thermal expansions and mechanical deformations in operation. The cells 18 of the abradable element 16 are generally hexagonal in shape and emerge radially inwards and radially outwards.

As illustrated in Figures 4 to 6, the abradable element 16, or abradable sealing device 16, is conventionally formed from a stack of strips 19 assembled to each other by brazing and extending in a longitudinal direction. Each strip 19 is corrugated and has alternating recessed areas and projecting areas formed by recesses or slots of hemi-hexagonal shape. The strips 19 are assembled to each other by brazing at the flat surfaces 20 formed by said undulations.

The sealing device 16 or each strip 19 has a first end 21, and a second end 22 opposite the first end 21 and capable of cooperating with the wiper(s) 15.

During the assembly by brazing of the strips 19 to each other and to the support 13, 17, the solder is deposited at the level of the first end 21 of the strips 19, in particular at the level of the flat assembly surfaces 20 ( ). The strips 19 then undergo a heat treatment during which they are subjected to a temperature sufficient to allow the solder, then in the liquid state, to diffuse by capillarity between the assembly surfaces 20, from the first end 21 towards the second end 22 of the strips 19 ( ). At the end of such a diffusion process, the solder has reached the second end 22 of said flat areas 20 ( ).

It turns out that the presence of solder at the level of the second end 22 of the strips 19 generates hard spots which give rise to significant wear of the free ends of the lips 15 cooperating with such an abradable device 16. Such wear affects the sealing and, consequently, the performance of the turbomachine.

In order to remedy such a drawback, document FR 3 064 669, in the name of the Applicant, proposes moving the flat assembly surfaces away from the side of the second end, to prevent the solder from progressing by capillarity until the second end of the straps. For this, the corrugations can gradually deviate from one strip to another, and from the first end to the second end.

It turns out, however, that such a structure may, depending on the applications, not make it possible to completely resolve the phenomenon of migration of the solder by capillarity at the level of the second end.

Presentation of the invention

The invention aims to remedy such a drawback in a simple, reliable and inexpensive manner.

To this end, the invention relates to an abradable sealing device between a rotor part and a stator part of a turbomachine extending along an axis, the sealing device comprising at least one first end, radially internal or external, and a second end opposite the first end and capable of cooperating with at least one wiper of the rotor part or of the stator part, the sealing device comprising strips assembled to each other by brazing and extending in a longitudinal direction, characterized in that at least one strip comprises a first corrugated zone, located on the side of the first end of the device and a second flat zone extending over the majority or all of the length of the strip, located from the side of the second end of the device, the strips being brazed to each other at the level of the first corrugated zone only.

The length of the strip is its dimension in the longitudinal direction of said strip.

The term "majority of the length" means that at least 50% of the length of the second zone of the strip is flat.

In this way, the second flat zones of the strips are widely separated from each other, which makes it possible to guarantee that the solder deposited at the level of the first end does not diffuse by capillarity as far as the second end. This avoids the hard point phenomenon at the second end of the strips and of the device, so as to limit the wear of the corresponding wiper(s).

Each strip may comprise a first corrugated zone, located on the side of the first end of the device, and a second flat zone extending over the majority or all of the length of the strip, located on the side of the second end of the device, the strips being brazed to each other at the first corrugated area only.

In other words, all the strips of the device have a similar structure.

The or each strip may include a transition zone connecting the first corrugated zone and the second flat zone.

The transition zone can comprise flat surfaces and/or curved surfaces, for example concave or convex fillets.

The undulations of the first zone can be of hemi-hexagonal shape, said undulations each comprising flat surfaces for assembly by brazing, parallel to the plane of the second zone.

A hemi-hexagon shape is a shape of half a hexagon. Such a shape is known from the prior art, as well as assembly by brazing at the flat assembly surfaces.

The first zone can extend over a distance of between 20 and 50% of the height of the strip.

The height is defined as the radial dimension between the first end and the second end of the strip.

The second zone can extend over a distance between 20 and 50% of the height of the strip.

The transition zone can extend over a distance between 20 and 50% of the height of the strip.

Each strip can be metallic. Each strip can for example be made of a nickel-based alloy, such as an alloy of Ha214 ^® type.

Each strip can be obtained by deformation of a flat strip, in particular at the level of the first zone and of the transition zone of said strip.

The distance between the second flat areas of two adjacent strips may be greater than 0.4 mm. This distance is for example between 0.5 and 2 mm, for example of the order of 0.8 mm or 1.6 mm, depending on the needs. In the case of a hemi-hexagonal corrugation, this distance is equal to the dimension of a hexagonal cell formed by the assembly of two strips.

The invention also relates to a turbomachine comprising at least one rotor part and one stator part, dynamic sealing means between said rotor part and said stator part, said dynamic sealing means comprising at least one wiper extending from the rotor or stator part and cooperating with at least one abradable sealing device of the aforementioned type, said device being mounted on the stator or rotor part.

The rotor part and the stator part can belong to a compressor or to a turbine of the turbomachine.

Brief description of figures

is a half view in axial section of a turbomachine of the prior art,

is an axial sectional view of part of a prior art turbine,

is an axial sectional view of part of a prior art compressor,

is a perspective view illustrating several strips of an abradable sealing device of the prior art,

is a perspective view illustrating said assembled strips,

is a top view of the prior art sealing device,

,

And

are views illustrating several successive steps of the process for brazing strips in accordance with the prior art,

is a schematic perspective view of part of a strip of a device according to one embodiment of the invention,

is a top view illustrating part of the device according to the invention,

is a schematic view of a strip according to a first embodiment,

is a schematic view of a strip according to a second embodiment,

is a schematic view of a strip according to a third embodiment.

Detailed description of the invention

There illustrates a strip 19 intended for the production of an abradable sealing device 16 according to one embodiment of the invention. This is metallic, for example made of a nickel-based alloy, such as for example an alloy of Ha214® type.

The strip 19 comprises a first corrugated zone 23, located on the side of a first end 21, a second flat zone 24, located on the side of a second end 22, opposite the first end 21, and a transition zone 25 connecting the first zone 23 to the second zone 24. The second zone 24 is entirely planar, that is to say extending along a single plane over the entire longitudinal dimension of the strip 19. The longitudinal direction A2 of the strip 19 is here perpendicular to the radial direction A1.

The undulations of the first zone 23 are of hemi-hexagonal shape. The transition zone 25 is formed of flat surfaces and/or curved surfaces, for example concave or convex, connecting the different flat surfaces of the first zone 23 to the second zone 24.

The first zone 23 comprises planar assembly surfaces, to have surfaces 20a and surfaces 20b parallel and offset from each other. The surfaces 20b extend in the plane of the second zone 24. The surfaces 20a are thus offset in the direction A3, with respect to the plane of the second zone 24 of the corresponding strip 19. The surfaces 20a of a strip 19 are brazed to the surfaces 20b of an adjacent strip 19, so as to form together hexagonal cells 18 in the first zone 23, as illustrated in .

The first zone 23 and the second zone 24 are formed by deformation of a flat strip.

The first zone 23 can extend along the direction A1 over a distance of between 20 and 50% of the height H of the strip 19, for example over a third of the height H of the strip 19.

The second zone 24 can extend along the direction A1 over a distance of between 20 and 50% of the height H of the strip 19, for example over a third of the height H of the strip 19.

The transition zone 25 can extend along the direction A1 over a distance of between 20 and 50% of the height H of the strip 19, for example over a third of the height H of the strip 19.

The distance d along the direction A3 between the second flat areas 24 of two adjacent strips 19 may be greater than 0.4 mm. This distance d is for example between 0.5 and 2 mm, for example of the order of 0.8 mm or 1.6 mm. This distance d is equal to the dimension of each hexagonal cell 18 formed by the assembly of two strips 19. The cells 18 of the device 16 are of the same dimensions.

The second flat zones 24 of the strips 19 are widely separated from each other, which makes it possible to guarantee that the solder deposited at the level of the first end 21 does not diffuse by capillarity as far as the second end 22. The phenomenon of hard point at the second end 22 of the strips 19 and of the device 16, so as to limit the wear of the corresponding wiper(s) 15.

The embodiment of each strip 19 may vary depending on the applications. There schematically illustrates a strip 19 in which the undulations or recesses of the zone 23 are oriented towards a first direction D1 with respect to the flat zone 24. In other words, the surfaces 20a are offset with respect to the surfaces 20b, 24 in said first direction D1.

There schematically illustrates another embodiment in which the strip 19 comprises undulations or recesses of the zone 23 oriented towards a second direction D2 with respect to the flat zone 24, opposite to the first direction D1. In other words, surfaces 20a are offset from surfaces 20b, 24 in said second direction D2.

There schematically illustrates another embodiment in which the strip 19 comprises undulations or recesses of the zone 23 centered with respect to the plane of the zone 24. In other words, the surfaces 20a are offset with respect to the plane of the middle zone 24 in the first direction D1, the surfaces 20b being offset with respect to the plane of the zone 24 in the second direction D2.

Claims (9)

Abradable device (16) for sealing between a rotor part and a stator part of a turbine engine extending along an axis, the device (16) comprising at least a first end (21) and a second end (22) opposite the first end (21) and able to cooperate with at least one wiper (15) of the rotor part or of the stator part, the device (16) comprising strips (19) assembled to each other by brazing and extending in a longitudinal direction, characterized in that at least one strip (19) comprises a first corrugated zone (23), located on the side of the first end (21) of the device (16) and a second zone ( 24) flat extending over the majority or the entire length of the strip (19), located on the side of the second end (22) of the device (16), the strips (19) being brazed to each other at the level of the first zone (23) corrugated only. Device (16) according to Claim 1, in which each strip (19) comprises a first corrugated zone (23), located on the side of the first end (21) of the device (16), and a second zone (24) flat extending over the majority or the entire length of the strip (19), located on the side of the second end (22) of the device (16), the strips (19) being brazed to each other at the level of the first zone (23 ) wavy only. Device (16) according to Claim 1 or 2, characterized in that the or each strip (19) comprises a transition zone (25) connecting the first corrugated zone (23) and the second flat zone (24). Device (16) according to one of Claims 1 to 3, characterized in that the undulations of the first zone (23) are of hemi-hexagonal shape, the said undulations each comprising flat surfaces (20a, 20b) for assembly by brazing, parallel to the plane of the second zone (24). Device (16) according to one of Claims 1 to 4, characterized in that the first zone (23) extends over a distance of between 20 and 50% of the height (H) of the strip (19). Device (16) according to one of Claims 1 to 5, characterized in that the second zone (24) extends over a distance of between 20 and 50% of the height (H) of the strip (19). Device (16) according to one of Claims 1 to 5, characterized in that the transition zone (25) extends over a distance of between 20 and 50% of the height (H) of the strip (19). Device (16) according to one of Claims 1 to 7, characterized in that the distance (d) between the second plane zones (24) of two adjacent strips (19) is greater than 0.4 mm. Turbomachine comprising at least one rotor part and one stator part, dynamic sealing means between said rotor part and said stator part, said dynamic sealing means comprising at least one wiper (15) extending from the rotor or stator part and cooperating with at least one abradable sealing device (16) according to one of claims 1 to 8, said device (16) being mounted on the stator or rotor part.