EP3615774A1

EP3615774A1 - Device for sealing between a rotor and a stator of a turbine engine

Info

Publication number: EP3615774A1
Application number: EP18725281.2A
Authority: EP
Inventors: Baptiste Marie Aubin Pierre JOUY; Josselin Luc Florent SICARD; Mathieu Charles Jean VERDIERE; Loïc Fabien François VILLARD
Original assignee: Safran Aircraft Engines SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2017-04-24
Filing date: 2018-04-24
Publication date: 2020-03-04
Anticipated expiration: 2038-04-24
Also published as: CN110546349A; JP2020517860A; FR3065483A1; RU2019133382A3; JP7175963B2; WO2018197800A1; RU2762016C2; US11441442B2; US20200095882A1; EP3615774B1; BR112019022128A2; FR3065483B1; CA3060182A1; CN110546349B; RU2019133382A

Abstract

The invention relates to a sealing device for use between a rotor part and a stator part, comprising at least one abradable coating (46) interacting with at least two upstream and downstream rubbing strips. Axially upstream of the rubbing strips, the sealing device comprises a circumferential wall (54) which extends radially beyond the free axial sealing surface upstream (48a) of the coating (46), in order to release the circulating gas at the free end of the upstream rubbing strip.

Description

Sealing device between rotor and turbomachine stator

The present invention relates to a sealing device between a rotor part and a stator part of an aircraft gas turbine engine in which gas must circulate.

In this application:

radial direction (substantially) perpendicular to the axis X mentioned below,

- circumferential has a direction extending around the axis X; Y direction in Figure 8,

- Outside and inside (or external and internal) respectively for radially outer and radially inner direction,

- licking is often translated into English: "rubbing st p (seal)" or "knife" or "labyrinth seal lip",

- Axial has for direction parallel to the axis of rotation including blades of the turbomachine; this is the X axis already mentioned, and

upstream and downstream are axial positions, with reference to the direction of global displacement of the gases in the turbomachine.

In a conventional manner, the stator part comprises an outer casing inside which, as elements of the sealing device, blocks of abradable material defining radially internal coatings adapted to cooperate with wipers are fixed circumferentially. rotor vanes rotatable about an axis (X), inside the outer casing. Such turbomachine outer walls provided with abradable inner linings may in particular be defined by a casing, or ring, of a compressor or turbine.

Furthermore, a stator portion also typically comprises blocks of abradable material which can define radially inner coatings stator blade vanes (or distributors) adapted to cooperate with wipers. However, relative movements between the blades and the casings occur, consequences of thermal and aerodynamic stresses.

In order to ensure that the turbomachine has the best possible efficiency, it is then imperative to limit the gas leaks that occur between the rotor blades of a rotor part, or the vanes of a stator part, typically at the end of the rotor. place of the aforesaid licks, and the abradable material coating opposite. Seals or sealing devices, typically labyrinth, formed by the wipers and blocks or coatings of abradable material, are intended to prevent or limit these leaks, opposing the passage of gas axially upstream in downstream, especially since the gases that bypass the blades do not participate in the work of the turbine.

In fact, control of the rotor / stator seal is an essential element of the efficiency of a turbine, low or high pressure (BP / HP), of a turbomachine as mentioned above and is typically provided on the one hand by the LPTACC or HPTACC system (Low Pressure, or Turbine Active Clearance Control Valve), which reduces the rotor / stator radial clearances, and on the other hand by the labyrinths thus provided at the top of blades and on intermediate rings, vis-à-vis distributors that create the seal for a given radial clearance.

However, the effectiveness of these wipers is not optimal and depends on several parameters such as their number, their thickness, their staging. Moreover, a potentially excessive radial clearance persists due to, among other things, manufacturing tolerances of the parts.

As a result, the flow rate of gas passing through the rotor / stator sealing zones remains high, even though various imperfect technological proposals have so far been developed, in particular on the basis of a configuration called "stepped inclinations".

An object of the invention is to improve this situation.

Therefore, a sealing device is proposed between a rotor part and a stator part of an aircraft gas turbine engine in which gas must flow from upstream to downstream, the rotor part being adapted to rotate relative to the stator part about an axis (X), the sealing device comprising at least one coating of abradable material: - fixed with the stator part,

and adapted to cooperate with at least two wipers, respectively axially upstream and downstream, projecting radially on an end portion of the rotor part,

the coating and said at least two wipers having radially, respectively, at least two axial free sealing surfaces, respectively axially upstream and downstream, and respective free ends, the free end of the downstream wiper and the free axial surface of downstream sealing being located at radial (radially facing) positions which are each further from the axis (X) than the free end of the upstream wiper and that the axial free upstream sealing surface (which are radially face), the device being characterized in that axially upstream of said at least two wipers with respect to the gas flow direction in this region of the turbomachine, the sealing device comprises a wall, or wall, circumferential which s' extends radially, beyond the axial free surface upstream sealing said coating, penetrating radially into the gas stream, thereby forming an obstacl e substantially transverse to the flow of gas from upstream, to create, at the free end of the upstream wiper, a detachment of the gas in circulation.

Compared to a configuration without this combination of characteristics, so in particular with respect to a solution with axial surfaces free sealing of the coating all located on the same radius (so-called "straight"), a substantial gain in sealing is obtained by the aforementioned steps and said circumferential wall which, forming a wall, penetrates radially into the gas flow. This indeed makes it possible to create a favorable detachment of the flow, thus including towards the end of the upstream wiper. This results in a smaller leakage section than with another in the form of wiping pairs / sealing surfaces of the coating, and a gain on the bypassed gas flow.

However, it turned out that there could be practical problems implementing the above solution, related to the thermal and aerodynamic conditions encountered, given the multiple situations that may exist on the ground and in flight.

It is therefore proposed, in particular to promote optimized positioning:

that, radially, said wall, or wall, still extends axially to a portion of the upstream wiper located radially at a distance from the free end of said upstream wiper, and / or

said circumferential wall is, axially, located at or towards an axially upstream end of the upstream free axial sealing surface of the coating, and / or,

that from the free axial surface of upstream sealing of the coating, this circumferential wall extends over a radial distance greater than or equal to 1.5 mm, and / or

that, from this same upstream free axial sealing surface of said coating, said circumferential wall extends radially over a radial distance of between 1 .25 mm and 5 mm, preferably

- and / or that certain reports are respected; see below: 1 <D1 / D2 <1, 5, 1 <L2 / L1 <4, 1 <L3 / L1 <3.

Tests have shown an increase in pressure drop (and therefore sealing) of about 10% compared to a solution as mentioned above, with axial free surfaces of the coating all located on the same radius (called " straight lines "), and without a circumferential wall forming a wall.

For considerations equally comparable to the foregoing, and even if most of the dissipation of energy that is sought to be born by the delamination at the end of the upstream lure occurs under the (the) lette (s), it is also proposed, for an application at the top of rotating blades, therefore of rotor:

that the end portion of the rotor part on which radially projecting said at least two wipers comprises a blade platform provided at the upstream end with a spoiler oriented upstream, and

- That, radially, said circumferential wall extends in front, but at a distance from the spoiler.

Thus, said circumferential wall will be sufficiently far upstream of the upstream wiper, thereby preventing the risks of contact during movements due to the aforementioned thermal and aerodynamic conditions, which are radially interposed between two guiding surfaces of the gaseous flow formed:

by the spoiler (which will typically extend upstream beyond said circumferential wall),

and by the upstream free axial sealing surface of the coating which extends downstream from this circumferential wall.

Another consideration taken into account relates to the ease of mass production, mounting and maintenance (replacement) of this circumferential wall.

It is also proposed:

said circumferential wall is defined by a slope formed on said coating projecting radially from the free upstream axial surface of said coating, and / or

- That wall is integral with said coating.

For comparable reasons, it is further proposed that:

the coating has a honeycomb structure comprising radial cells individually having an axial dimension, and

- The circumferential wall has axially greater than said axial dimension of the cells located on the same circumference, transverse to said axis (X).

Thus, we will combine mechanical strength and reliability with ease of assembly and maintenance. Yet another consideration taken into account concerns the optimization of the creation of the detachments of the flow at the end of the upstream wipers.

It is also proposed:

- at least the upstream wiper is, in the direction of the upstream free axial sealing surface, inclined upstream with respect to the axis (X) and at a radial to the axis, this on a part at less than its length or

- That the free end of the upstream wiper is located radially opposite an axially upstream portion of the upstream free axial sealing surface.

The second consideration makes it possible to benefit, over a long axial length at the end of the coating, from the radial effect of the detachment on the gas flow.

It is furthermore proposed that said at least two axial free sealing surfaces, respectively axially upstream and downstream, have between them a radial connecting wall (hence perpendicular to the X axis).

It has indeed been found that in terms of ease of manufacture and mechanical strength, such a radial connecting wall is here preferable to a bias configuration, as in US2009067997 (walls 1 12).

The invention also relates to an aircraft gas turbine engine, as such, characterized in that it is equipped with the sealing device with all or part of its aforementioned characteristics.

The invention will, if necessary, be better understood and other details, characteristics and advantages of the invention will become apparent on reading the following description given by way of nonlimiting example with reference to the appended drawings in which:

FIG. 1 schematizes, in axial partial section, an aeronautical turbine engine part to be mounted on an aircraft,

FIG. 2 schematizes, according to the same vertical section along a median plane containing the X axis, a low-pressure turbine part that can equip the turbine engine of FIG. 1, FIG. 3 schematizes, in perspective, a rotating blade (of rotor) which can equip the turbine of FIG. 2,

FIG. 4 is a vertical section along the line IV-IV of FIG. 5, at the level of moving blades of a turbine stage to be disposed in the outer casing which receives them;

FIG. 5 schematizes in axial partial section a cooperation between an abradable coating and an end of said moving blade;

FIG. 6 schematizes a total pressure field under an upstream wiper, in a test thus mounted (the detachment generated is clearly visible), FIG. 7 showing a more realistic assembly, with also such energy fields,

FIGS. 8, 9 schematize, in perspective and side view, an abradable block that can be used,

FIG. 10 illustrates the performance gain related to the implementation of the circumferential wall proposed by the invention, namely a 10% reduction of the maximum leakage rates, and

- Figures 1 1 and 12 illustrate two variants, according to the invention, of the sealing device.

As schematized in FIG. 1, a double-stream turbomachine 1 for an aircraft comprises at least one annular casing, or circumferential casing, 2, external fan, inside which are arranged different components of the turbomachine.

At the inlet of the external annular casing 2, considering the direction of movement of the air (opposite to the direction of travel of the aircraft, see arrow in FIGS. 1, 2), there are blades of a fan 3 coupled to each other. to a rotary shaft 4. Then, connected to the shaft 4 which extends around the axis X of rotation of the turbomachine, are different axial compression stages, typically a low pressure compressor 5a followed by a high compressor pressure 5b. Then are arranged various other elements of the engine including turbine stages (s) axial (s), typically a high pressure turbine 6 followed by a low pressure turbine 16. The air enters the external annular fan casing 2 where it is driven by the blades of the fan 3. To ensure propulsion, the major part flows into the secondary duct 1 1 delimited radially between a portion of the annular casing 2 external and a motor housing 7 more interior. Another part of the air is sucked into a primary stream 13 (stream 71 from upstream to downstream, FIGS. 5 and 11) by the low-pressure compressor 5a and directed towards the stages of the turbine 6 via other components of the engine. The stiffening arms 10 also connect the external annular casing 2 and the motor casing 7.

Each compressor, such as the low-pressure compressor 5a in FIG. 1, comprises a rotating or rotating part and a fixed part secured to a housing of the engine 7. More particularly, the compressor comprises an alternation of blades 8 belonging to wheels rotor, coupled to the shaft 4, and thus rotating, and rectifiers 9 (or stators) coupled to the fixed part of the compressor to straighten the air.

The aforementioned "circumferential wall" may in particular be provided on a low-pressure turbine, FIG. 2 shows an example of such a turbine which comprises axially several rows of blades 18, 20, 22 (blades 8) and vanes 24, 26 (rectifiers 9), alternatively.

The blades 24, 26 are, at their radially external ends, mounted by means not shown on a housing of the motor 7 and the rotating vanes 18, 20, 22 are mounted, for example by dovetail means or the like at their radially inner ends on discs 28, 30, 32 of the rotor. Each disk comprises an upstream annular flange 36a and a downstream annular flange 36b for fixing the disks together and on a drive cone 34 connected to the shaft 4 of the turbomachine, to rotate with it, and to the fixing annular flanges retaining blade roots on the discs. The blade roots are shaped to cooperate with axial grooves provided in the rotor discs. Each rotating blade extends along an axis perpendicular to the axis X of the rotor on which the blade is mounted. Two discs, such as 28,30, axially successive rotor are interconnected, via the aforementioned annular upstream and downstream flanges, by bolts 33 which also maintain an intermediate sealing ring 35 carrying an inter-stage seal 37 and located in outer periphery of the corresponding upstream flange 36a. This joint known per se may include radial annular extensions or wipers 41 cooperating with an abradable coating 46, so as to define a rotor / stator seal.

The rotor blades are arranged and rotatable about the X axis between an outer annular boundary 44 and an inner annular boundary 45 which may be substantially defined by inner platforms 47 provided with rotary vanes and stationary rectifiers. 2, each coating 46 is fixed to the radially inner shell 43 of the corresponding inner platform 47.

Figure 3 shows an example of a rotor blade, such as that 18, which may belong to the first low pressure turbine wheel.

Each vane has a blade root 38a at its inner end and the outer platform 38b towards its outer peripheral end. The blade extends along a blade axis Z perpendicular to the axis X of the rotor on which said blade is mounted.

Like the wipers 41 of FIG. 2, wipers, respectively axially upstream and downstream, 40a, 40b, are provided here.

All wipers 40a, 40b, 41 are disposed in planes substantially perpendicular to the axis of rotation X of the rotor, and extend substantially annular.

As for the wipers 41, there is thus here, by bringing together FIGS. 2 and 3, at least two wipers 40a, 40b carried by an end portion, here 38b, of a rotor part, and of which the wipers are radially here. protruding externally. These wipers are adapted to cooperate with a coating of abradable material 46 fixed, a priori indirectly, with the inner wall of a fixed outer casing 441 belonging to the outer annular limit 44 above, to form a labyrinth seal, and thus to define a Sealing device 50. Typically, this attachment is via ring sectors 442 hung circumferentially on the outer casing 441.

The blocks 46 of abradable material typically extend in angular sectors, circumferentially around the X axis.

Although the following refers in particular to FIG. 5, all the rotor / stator sealing zones involving abaradables, in particular between the wipers 41 and the coatings 46 of the ferrules 43, are concerned, since:

- that the coating 46 will radially present at least two axial free sealing surfaces, 48a, 48b, respectively axially upstream and downstream, - that said at least two wipers, such as 40a, 40b here, radially present respective free ends, 50a, 50b, and

the free end 50b of the downstream wiper 40b and the free axial surface 48b of downstream sealing:

- will be located at radial positions being radially opposite and - each will be (respective radii Rav2, Rav1, see Figure 5) farther from the axis X than the free end 50a of the upstream wiper 40a and that the surface axial free upstream sealing 48a, which will be radially face (respective radii and Ram2, Ram1).

Indeed, this contributes to a significant reduction (5 to 15% a priori) of the by-passed gas flow which will not then cross the sealing zone concerned, all the more so if, as shown schematically in FIGS. 5 and 7, there is associated at least one upstream wiper 40a which, in the direction of said upstream free axial sealing surface, is inclined upstream (AM) with respect to the axis (X) and at a radial to the axis, on at least part of its protruding length. In Figure 7, the two wipers 40a, 40b are inclined upstream. And it can be seen that the free end 50a of the upstream wiper 40a is located radially facing an axially upstream portion 52a of the upstream free axial sealing surface 48a of the abradable coating 46. This should make it possible to benefit, on a long axial length at the end of the coating, the radial effect of the detachment of the gas flow created by the circumferential wall 54 provided axially upstream of the wipers and which extends radially beyond the free upstream axial sealing surface 48a of the coating 46 considered. Since circumferential, the wall 54 can extend in angular sectors around the axis X.

Overall, such a double obstacle, with an abaradable step and wipers radially offset and inclined at least for the upstream wiper, takes anyway its meaning.

Figures 6 and 7 show the separation, referenced 420, of this gas flow created by the circumferential wall 54 at the end 50a of the upstream wiper.

By this addition upstream of the sealing zone of a solid wall a priori full 54 which creates a substantially transverse obstacle to the flow of gas upstream of this zone, we will be able to obtain an important phenomenon of energy dissipation, referenced 430,440 just downstream of the ends of the different rows of wipers.

And it is the circulation caused between the two wipers 40a, 40b by the wall 54 which will create the conditions favorable to the separation 410 at the end of the downstream wiper. The example of Figure 7 makes it possible to note it.

Figures 2 and 5, we will notice the projection defined by the wall or wall 54 relative to the free surfaces (substantially) axial, here 47a and 48a, which radially limit the interspace 70 of circulation of the gas stream. The wall or wall 54 is thus formed in the interspace 70 gas adjacent the primary vein 13 and located radially between the abradable 46 and the top of the blade 18 concerned, As will be noted, the free surfaces 47a and 48a belong to the outer annular limit 44, the free surfaces 47a, 48a are located axially respectively on either side of said wall 54.

It may also be noted that, in addition to the free (substantially) upstream axial free surface 47a, that of the ring sectors 442 which is located axially (X axis) just upstream of the wall 54 considered has a free (substantially) axial downstream surface 47b. The free surfaces 47a and 47b respectively extend adjacently upstream and downstream of the wall 54; and this wall 54 (at least its surface (substantially) free axial 541) is radially (Z axis) protruding vis-à-vis the free surface (substantially) axial upstream 47a and the free surface (substantially) downstream axial 47b ring sector 442 considered.

As schematized in addition to Figure 4, each wall 54 may, in the image of the portion of the stator that comprises it, extend in a plane perpendicular to the axis of rotation X and this annularly, in angular portions.

Including to preserve the integrity of the / each wall 54 taking into account the movements of parts due to the aforementioned thermal and aerodynamic conditions, it is recommended that this wall 54 be axially located at or towards an axially upstream end 520a of the surface. axial free upstream sealing of the coating 46, upstream of the zone 52a above.

As can be seen in the figures, vis-à-vis the two upstream and downstream 48a and 48b free sealing surfaces, the wall or wall 54 will be a priori unique, in the sense that it is located just upstream, or at the end upstream of the upstream free sealing surface 48a, no other such radially projecting wall no longer exists downstream on the sealing device 50, in particular on the abradable 46, and in particular on the downstream free sealing surface 48b.

The detachment 420 and the schematic representations of turbulent kinetic energy at 430 and 440 (see FIG. 6 or 7) make it possible to clearly note that the wall 54 defines, or forms, a disturbance of the flux in the inter-space 70 and that the upstream face 540a of this wall is arranged to be opposite this flow, substantially along the Z axis, therefore. In the preferred example illustrated, the upstream face 540a and the axially upstream end 520a are the radial extension of one another.

To promote the phenomenon of energy dissipation that is sought to be born by the detachment at the end of the wipers upstream, it is furthermore proposed that, radially, the wall 54 still extends axially part 400 of the (each) upstream wiper 40a located radially at a distance from the free end 500a of this wiper; see in particular figure 5. Without a circumferential wall 54, the direction of the jet would remain (more) axial and pass the end of the upstream wiper 40a without pronounced detachment phenomenon. In a certain way in the manner of a wall, the wall 54 modifies the topology of the flow. The gaseous jet has a more radial direction which induces a much greater detachment at the passage of this upstream wiper. The leakage section being closed by the detachment, the energy dissipation is increased, which is favorable to the desired sealing. It could thus be seen (as in Figure 7) that the turbulent kinetic energy is maximum in the vicinity of a downstream wiper, therefore greater than at the location of an upstream wiper.

Possibly in combination with the above feature, it is also recommended, in particular to promote optimized positioning:

that from the free upstream axial sealing surface 48a of the coating 46, the circumferential wall 54 extends over a radial distance D1 greater than or equal to 1 .5mm, or

- That, from this same upstream free axial sealing surface 48a of said coating, said circumferential wall 54 extends radially over a radial distance D1 of between 1 .25 mm and 5 mm, preferably.

FIG. 10, moreover, it can be seen that on an embodiment such as that of FIG. 5 tested with a radial wall 62 for connection between two axial free sealing surfaces, respectively axially upstream 48 a and downstream 48 b, 5 mm high (staggering 1). , the curve of evolution of the ratio in% of the airflow delta flowing in the inter-space, in zone 70, between the abradable 46 and the vertex of the blade 18 concerned, as a function of the height D1 marks a bearing at 1 .5mm. The efficiency is more marked beyond this value. Beyond 5mm, no additional gain is demonstrated, and problems of integration of the rotor in the turbine arise. Note that a little less than 4% difference, a value D1 = 1 .25mm is acceptable, the efficiency is already sensitive. It should also be noted that the following reports contribute to such performances, preferably in combination (see FIGS. 5 and 12 for identification of the distances concerned):

1 <D1 / D2 <1, 5, and / or

1 <L2 / L1 <4, and / or

1 <L3 / L1 <3.

These ratios favor the disturbance of the flow, as seen with the presence of the two main high energy zones 430,440.

For confirmation :

D1 which is the projection of the wall 54, or the radial distance between the upstream free axial sealing surface 48a of the abradable coating 46 and the free end of the wall 54,

- D2 which is the radial distance between the free end of the wall 54 and a radially outer face 560a of the spoiler 56 situated in its radial continuity, - L1 which is the axial thickness of the (each) upstream wiper 40a, end radial free of it,

L 2 which is the axial distance between a downstream face 540b of the wall 54 and, situated in its axial continuity, an upstream face 401a of the upstream wiper 40a, at the free radial end thereof, and

- L3 which is the axial distance between the radial connecting wall 62 and, located in its axial continuity, a downstream face 403a of the upstream wiper 40a, radially free end thereof.

These reports were confirmed as contributing to the aforementioned additional energy dissipation, a little over 10%.

For considerations comparable to the above, it is also proposed, for an application at the top of rotating blades, and therefore of rotor:

the platform 38b is provided at the upstream end with a spoiler 56 facing upstream, and

- That, radially, said circumferential wall 54 extends opposite, but at a distance, the spoiler.

Such a distance D2 of more than 20mm is recommended. In addition, to facilitate mass production, assembly and maintenance of the circumferential wall 54, it is furthermore advisable to:

this wall 54 is defined by a slope 58 formed on the coating 46 considered, projecting radially from the upstream free upstream axial sealing surface 48a, and

that this wall 54 is integral with said coating 46, as illustrated.

In particular, each abradable sealing coating may be formed of honeycomb, with cavities 60 individually with a closed contour; see Figure 8 where are identified the X axis and the Y axis, transverse to the X and Z axes. The cells, typically polygonal, will be interconnected to form a block, a portion of which is illustrated in Figure 8, in one embodiment. . The cavities 60, radially open, individually have an axial dimension L4 (length), and the circumferential wall 54 axially has a thickness E1 greater than said axial dimension L4 of the cells (of each mesh) located on the same circumference C1, transversely to said axis. X; see Figures 8.9.

If this is the case, we can combine mechanical strength and reliability with ease of assembly and maintenance.

The inclined connecting walls, obliquely (as in US2009067997 / walls 1 12), imposing particular machining constraints, it is furthermore proposed that said at least two axial free sealing surfaces, respectively axially upstream 48a and downstream 48b , have between them a radial connecting wall 62 (substantially perpendicular to the X axis in the example). The example of FIG. 7 makes it possible to note that the turbulent kinetic energy field (or pressure field) at the passage of a rotor / stator sealing zone designed with the aforementioned characteristics has two main high energy zones. 430,440, immediately downstream of the wipers 40a, 40b, and are almost in contact with the respective surfaces 48a, 48b. On the other hand, this energy / pressure field is weaker in the immediate environment of the right-hand walk 62 (zone 450). The level of turbulent kinetic energy is representative of the losses of charges, and therefore characterizes the effectiveness of the seal. The turbulent kinetic energy, already high at 430, is here maximum at 440, in the vicinity of the second wiper.

All this is favorable to a limitation of the bypassed gas flow.

In connection with the circumferential wall 54, the additional energy dissipation has been estimated - by calculation - to be slightly greater than 10% with respect to a solution without a circumferential wall and without staggering or free surfaces of the coating or upstream wipers. and downstream, knowing that this gain can be obtained on each rotor / stator cooperation stage considered, as here turbine.

Technologically, several solutions can be envisaged to constitute the wall 54 upstream of the sealing zone considered.

A relevant solution that is simple to implement and effective is to provision crude platelets of abradable 46 that are quite high; direction Z figure 9 where the X / Z scales are not respected. Several machining is then used to create the wall / wall 54 and the two stepped surfaces 48a, 48b, here with the step 62, intermediate between them, radial. Axially at least as thick (E1) as a cell 60 (L4) in particular to ensure the continuity of said wall (and the sealing of this wall 54), the circumferential wall 54 is itself perpendicular to the surfaces 48a , 48b.

In Figure 1 1 shows a mounting, which may be more operational, abradable coating. In this solution, each of the circumferential blocks of abradable coating 46 is fixed (for example welded or brazed) radially outwardly on one of the ring sectors 442. Each of these ring sectors is hung circumferentially on the outer casing 441. Each ring sector 442 can be fixed for this purpose (for example welded to it) and radially outer:

- To the downstream end, at least one downstream hook holding member 66 (or C), open (s) upstream and (each) engaged circumferentially with a downstream circumferential rail 68, protruding towards the downstream of the outer casing 441 (or attached to it), and towards the upstream end, at least one upstream hook (or C) holding member 72, open (s) upstream and (each) engaged circumferentially with an upstream circumferential rail 74, projecting towards the downstream of the outer casing 441 (or attached to it).

In this case, it is the (substantially) free axial surface 72a of the (each) upstream holding member 72 which will define said free axial upstream surface of the ring sector (referenced 47a in the embodiment of the figures 2 and 5).

As before, this upstream free axial surface 72a of the ring sector 442 is axially (X axis) immediately adjacent to the wall 54 which projects radially from it. Thus, the downstream gas flow flowing in the inter-space 70 licks the (substantially) free axial surface 72a and then abuts against the transverse wall 54 which is (substantially) along the X axis contiguous to the surface 72a.

In another alternative, as illustrated in Figure 12, the free axial surfaces on either side of the wall. In this case, the upstream and downstream free (substantially) axial surfaces contiguous to the wall 54 are each formed by the abradable element of the relevant mobile wheel ring sector 442. Thus, the (each) abradable element 46 integrates, besides the wall 54 and the upstream free axial surface 48a, another (substantially) free axial surface 48c located upstream of the wall 54. To ensure its effect, the wall 54 is radially projecting inward with respect to said (substantially) free axial surfaces 48c and 48a which are contiguous thereto, respectively upstream and downstream.

From the foregoing and the support of the illustrations, it will be understood that, to create, at the free end of the upstream wiper 40a, a separation of the circulating gas, the wall 54, defined by a difference in level with said coating 46, will therefore form:

a radial projection with respect to an upstream free axial surface (47a, 48a, 48c, 72a above) of the sealing device 50 which is contiguous or adjacent thereto, axially, - In particular a radial projection relative to an upstream free axial surface (47a, 48c, 72a above) of the sealing device 50 which is contiguous or adjacent to it, axially upstream of it; see distance D3 Figures 5.1 1, 12.

Claims

1. Sealing device between a rotor part (8, 18, 38, 35, 36) and a stator part (9, 43; 440) of an aircraft gas turbine engine in which gas must flow upstream to the downstream portion, the rotor portion being adapted to rotate relative to the stator portion about an axis (X), the sealing device comprising at least one coating (46) of abradable material:

- fixed with the stator part (9,43; 440), and

adapted to cooperate with at least two wipers (40a, 40b), respectively axially upstream and downstream, projecting radially on an end portion of the rotor portion (8, 18, 38b; 35, 36),

the coating (46) and said at least two wipers (40a, 40b) having radially, respectively, at least two axial free sealing surfaces (48a, 48b), respectively axially upstream and downstream, and respective free ends (50a, 50b), the free end (50b) of the downstream wiper (40b) and the free axial downstream sealing surface (48b) being located at radial positions which are each further from the axis (X) than the free end (50a) of the upstream wiper (40a) and that the upstream free upstream axial sealing surface (48a),

characterized in that axially upstream of said at least two wipers (40a, 40b) with respect to the direction of flow of the gas, the sealing device (50) comprises a circumferential wall (54) which extends radially up to beyond the upstream free upstream axial sealing surface (48a) of said coating (46), penetrating radially into the gas stream (70), thus forming a substantially transverse obstacle to the flow of gas from upstream, for create, at the free end of the upstream wiper (40a), a detachment of the circulating gas.

2. Device according to claim 1 wherein, radially, the wall (54) extends further axially to a portion (400) of the upstream wiper (40a) located radially at a distance from the end. free (50a) of said upstream wiper.

3. Device according to any one of the preceding claims, wherein the wall (54) is axially located at or towards an axially upstream end of the upstream free axial sealing surface (48a) of the coating (46).

4. Device according to any one of the preceding claims, wherein the wall (54) is integral with said coating (46).

5. Device according to any one of the preceding claims, wherein the wall (54) is defined by a difference in elevation formed on said coating (46), projecting radially from an upstream free axial surface (47a, 48a, 48c, 72a) of the sealing device.

6. Device according to any one of the preceding claims, wherein at least the upstream wiper (40a) is, in the direction of said upstream free axial sealing surface, inclined upstream with respect to the axis (X) and at a radial to the axis, over at least part of its length.

7. Device according to claim 6, wherein the free end of the upstream wiper (40a) is located radially opposite an axially upstream portion (52a) of the upstream free axial sealing surface.

8. Device according to any one of the preceding claims wherein, from the upstream free axial sealing surface of said coating (46), the wall (54) extends over a distance (D1) radial greater than or equal to 1. 5mm.

9. Device according to any one of the preceding claims wherein, from the upstream free axial sealing surface of said coating (46), the wall i (54) circumferential extends radially over a radial distance (D1) between 1 .25mm and 5mm.

10. Device according to any one of the preceding claims wherein said at least two axial free sealing surfaces, respectively axially upstream and downstream, have between them a wall (62) of radial connection.

1 1. Apparatus according to any one of the preceding claims, wherein:

the coating (46) has a honeycomb structure comprising radial cells (60) individually having an axial dimension (L4), and

- The wall (54) axially has a thickness (E1) greater than said axial dimension (L4) of the cells located on the same circumference (C1), transverse to said axis (X).

12. Device according to any one of the preceding claims, wherein:

the end portion of the rotor portion (8, 18, 38, 35, 36) projecting radially from said at least two wipers (40a, 40b) comprises a blade platform (38b) provided at the upstream end of a spoiler (56) facing upstream, and

- Radially, the wall (54) extends in front, but at a distance, the spoiler (56).

The device of claim 12, wherein, preferably in combination:

1 <D1 / D2 <1, 5,

1 <L2 / L1 <4,

1 <L3 / L1 <3, with:

- D1 which is the radial distance between the upstream free axial sealing surface (48a) of said coating (46) and the free end of the wall (54),

- D2 which is the radial distance between the free end of the wall (54) and a radially outer face (560a) of the spoiler (56),

L1, which is the axial thickness of the (each) upstream wiper 40a, at the free radial end,

L2, which is the axial distance between a downstream face (540b) of the wall (54) and an upstream face (401a), at the free radial end, of the upstream wiper (40a), and

L3, which is the axial distance between a downstream face (403a), at the free radial end, of the upstream wiper (40a) and the radial connecting wall (62).

14. A gas turbine engine (1) for aircraft, characterized in that it is equipped with the sealing device (50) according to any one of the preceding claims.