FR3085405A1 - PRESSURIZATION OF THE INTER-LECHETTES CAVITY BY BYPASSING THE BYPASS FLOW - Google Patents

Abstract

The invention relates to a sealing structure (20) of a seal (9) of a turbomachine, the sealing structure (9) extending circumferentially around an axis (X) and being configured. to cooperate in friction with at least one wiper (12) carried by a rotor of the turbomachine, the sealing structure comprising an abradable element (20) and having an upstream face (25) intended to be disposed opposite a flow passing from upstream to downstream of the turbomachine and a radially internal face (26) configured to extend opposite the at least one wiper (12), and at least one pipe (30), formed in the abradable element (20), said at least one pipe (30) opening on the one hand into the upstream face (25) and on the other hand into the radially internal face (26) with a circumferential orientation relative to the axis ( X).

Description

FIELD OF THE INVENTION

The invention relates to the field of turbomachinery and more particularly the general field of sealing elements, in particular labyrinth seals, intended to seal between a rotor and a stator in a turbomachine.

TECHNOLOGICAL BACKGROUND

A double-flow turbomachine generally comprises, from upstream to downstream in the direction of gas flow in the turbomachine, a fan, an annular space for primary flow and an annular space for secondary flow. The mass of air sucked in by the fan is therefore divided into a primary flow and a secondary flow which is concentric with the primary flow.

The primary flow passes through a primary body comprising one or more stages of compressors, for example a low pressure compressor and a high pressure compressor, a combustion chamber, one or more stages of turbines, for example a high pressure turbine and a low pressure turbine , and a gas exhaust nozzle.

A high pressure or low pressure turbine conventionally comprises one or more stages, each consisting of a row of fixed vanes, also called a distributor, followed by a row of movable vanes spaced circumferentially around the disc of the turbine. The distributor deflects and accelerates the flow of gas from the combustion chamber to the moving blades of the turbine.

It is the same for the compressor, low pressure or high pressure, which comprises one or more stages each comprising a row of stationary blades, or rectifier, and a row of movable blades.

The movable stages of the same rotating part (whether a high pressure or low pressure turbine or a high pressure or low pressure compressor) are connected to each other by a common rotor shaft.

Sealing must be ensured between each movable stage and the fixed opposite parts in order to limit air leaks as much as possible at the level of the primary flow flowing in the rotating part and thus improve the efficiency of the turbomachine. As can be observed in document FR 2 926 612, this seal is ensured, for each rotating part, by a seal such as a labyrinth seal or a seal with an abradable coating. Such a seal comprises a first rotating part and a second fixed part which together define one or more annular cavities.

The performance of a rotating part of a turbomachine, whether it is a turbine or a compressor, is related to the flow of bypass air (or "bypass", passing in the seal ring annular cavities. The greater the pressure losses at the seal, the more effective the seal and the higher the efficiency of the rotating part.

In order to improve the performance of the turbomachine, it has been proposed to provide gases at the wipers to improve the seal. However, these designs need to be improved to increase the pressure drops at the wipers and thus improve the sealing of the labyrinth seal.

It has also been proposed to use a seal comprising a ring of abradable, fixed material and movable wipers, to divide the ring into two portions and to form a groove in which the end is placed free from one of the wipers. This solution makes it possible to increase the pressure losses at the level of the seal, even in the event of play at the level of the seal. However, it does not limit the rise in temperature at the seal.

SUMMARY OF THE INVENTION

An objective of the invention is therefore to propose a solution which makes it possible both to increase the pressure drops within a seal for a rotating part, in particular of a seal of the labyrinth type.

For this, the invention provides a sealing structure for a gasket of a turbomachine, the sealing structure extending circumferentially around an axis and being configured to cooperate in friction with at least one wiper. carried by a rotor of the turbomachine, the sealing structure comprising an abradable element and having an upstream face intended to be disposed opposite a flow passing from upstream to downstream of the turbomachine and a radially internal face configured for lie next to the at least one wiper. The sealing structure further comprises at least one pipe, formed in the abradable element, said at least one pipe opening on the one hand into the upstream face and on the other hand into the radially internal face with a circumferential orientation relative to to the axis.

Some preferred but non-limiting characteristics of the sealing structure described above are the following, taken individually or in combination:

- The abradable element is preferably annular in a material having a honeycomb structure.

- The at least one pipe comprises a first portion and a second portion, the first portion opening into the upstream face while the second portion opens into the internal radial face, the second portion being cylindrical and having a circumferential orientation relative to the 'axis.

- The second portion of at least one pipe is also inclined upstream so that a flow of air passing through the pipe is injected through its outlet with an axial orientation.

- The sealing structure comprises a series of pipes formed in the abradable element and each opening on the one hand in the upstream face and on the other hand in the internal radial face.

- The at least one pipe comprises a first portion extending from the upstream face of the fixed part and a second portion opening into its internal radial face, the second portion dividing so as to form at least two channels having a circumferential orientation opposite and each opening into the internal radial face.

- the second portion is divided so as to form three injection channels.

each pipe comprising a first portion extending from the upstream face and a second portion opening into the internal radial face, the second portion of each pipe dividing so as to form at least two injection channels each opening into the radial face internal and being configured so that a flow which is injected through the injection channels of a given pipeline crosses a flow which is injected through the injection channels of an adjacent pipeline before said flows reach the at least one léchette.

According to a second aspect, the invention also proposes a seal comprising a sealing structure as described above.

In one embodiment, the seal comprises at least two wipers carried by the rotor of the turbomachine, said at least two wipers delimiting with the abradable element at least one cavity, the pipe opening into said cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics, objects and advantages of the present invention will appear better on reading the detailed description which follows, and with regard to the appended drawings given by way of nonlimiting examples and in which:

Figure 1 is a schematic view of a first example of a seal according to the invention.

Figure 2 is a schematic view of a second example of a seal according to the invention, in which the direction of rotation of the rotating part has been shown.

Figure 3 is a perspective view of the first example of a seal illustrated in Figure 2 attached to a distributor and an upstream flange of a rotating part.

Figure 4 is a schematic view of a third example of a seal according to the invention.

Figure 5 is a perspective view of a fourth example of a seal according to the invention attached to a distributor and an upstream flange of a rotating part.

DETAILED DESCRIPTION OF AN EMBODIMENT

In the present application, the upstream and downstream are defined with respect to the direction of flow of the gas in the turbomachine, and therefore in the rotating part 1. Furthermore, the axis of revolution X of the rotating part 1 is called, the axis X of revolution of the seal. This axis of revolution X coincides with the axis of rotation of the rotating part 1 of the turbomachine. The axial direction corresponds to the direction of the axis X of the seal, and a radial direction is a direction perpendicular to this axis and passing through it. The tangential direction is a direction perpendicular to the X axis and not passing through it. A circumferential direction is a direction that extends around the X axis. Unless otherwise specified, internal (or interior) and external (or exterior), respectively, are used with reference to a radial direction so that the part or the internal face (ie radially internal) of an element is closer to the X axis than the part or the external face (ie radially external) of the same element.

The invention can find application in any rotating part 1 of a turbomachine comprising a rotor 2 and a fixed part, for example in a compressor section or a turbine section 1. In the following, for convenience, the invention will be more particularly described in the case where the rotating part 1 is a turbine 1.

The turbine 1 comprises one or more stages housed in a turbine casing 2. Each turbine stage 1 comprises a rotor 3 and a stator 5.

The rotor 3, or moving wheel, comprises an annular disc comprising a radially external platform on which are fixed a plurality of blades 4. The blades 4 can for example be attached and fixed in impressions formed in the platform or formed integrally and in one piece with the platform and the disc (one-piece bladed disc). The rotor 3 is movable in rotation around the axis of rotation of the turbomachine.

The stator 5, or distributor, comprises a plurality of vanes 6 arranged radially with respect to the axis of rotation of the turbine connecting a radially external annular element (or external crown) and a radially internal annular element 7 (or internal crown 7 ) which reconstitute the air stream and are fixed on the turbine casing 2.

The discs of the rotors 2 of the turbine 1 are connected axially in cascade to one another. For this, with the exception of the end discs which comprise only a single flange, each disc comprises an upstream flange 8 and a downstream flange extending axially from the disc, the downstream flange of a given disc being configured to be connected to the upstream flange 8 of the adjacent disc located immediately downstream.

In operation, the gas flow enters the primary body through the blower. Part of this gas flow, commonly called bypass flow F1, bypasses the rotor 3 (between the head of the blades 4 of the rotor 3 and the turbine casing 2) and the distributor 5 (between the inner ring 7 and the upstream flange 8 ).

In order to limit the flow rate of this bypass flow F1, the turbine 1 further comprises a seal 9 comprising a movable part 10 configured to be carried by the rotor 3 of the turbine 1 so as to be integral in movement with said rotor 3 and a fixed part 20 configured to be carried by a fixed element of the turbine 1, which can be the distributor 5 or the turbine casing 2. The seal 9 has a geometry of revolution around its axis of revolution X , which coincides with the axis of rotation of the turbine.

For example, in the case of a seal 9 of the labyrinth type, the movable part 10 comprises at least two wipers 12 (or sealing ribs), for example between two and three wipers 12, which extend Radially projecting from the rotor 3 in the direction of the fixed part 20. The fixed part 20 can comprise an annular support 22 or "abradable carrier 22" on which is fixed an annular element of abradable material called hereinafter " abradable element 24 ". Where appropriate, the abradable element 24 and the abradable carrier 22 may each be formed of an annular row of sectors mounted circumferentially end-to-end. The abradable element 24 may for example comprise a material having a honeycomb structure.

The wipers 12 delimit two or two with the abradable element 24 one or more cavities 14. A given cavity 14 therefore extends between two adjacent wipers 12.

In a first embodiment illustrated in FIG. 4, for each stage of the turbine 1, the mobile part 10 (in particular the wipers

12) of the seal 9 is fixed on the head 4a of the blades 4 of the rotor 3, that is to say on the radially outer face of the blades 4.

The fixed part 20 (in particular the abradable carrier 22 and the abradable element 24) is then fixed on the turbine casing 2, facing the head 4a of the blades 4 and more particularly of the movable part 10 of the seal. 9 carried by the head 4a of the blades 4.

In a second embodiment illustrated in FIGS. 1, 2 and 5, for each stage of the turbine 1, the movable part 10 (in particular the wipers 12) of the seal 9 is fixed to the upstream flange 8 of the disc of the rotor 3.

The fixed part 20 (in particular the abradable carrier 22 and the abradable element 24) is then fixed on the internal crown 7 at the foot of the dispenser 5, the internal crown 7 being disposed opposite the movable part 10 of the seal d sealing 9.

The fixed part 20 has an upstream face 25 and an internal radial face 26 extending opposite the movable part 10.

The upstream face 25 corresponds to the face of the seal 9 which extends most upstream relative to the direction of flow of the gases in the turbomachine, but also relative to the direction of flow of the bypass flow F1 in the turbine 1. The upstream face 25 therefore corresponds to the face which is configured to extend opposite the bypass flow F1 when it enters the seal 9.

In the first embodiment, the upstream face 25 is located opposite the outer ring of the turbine stage 1 extending immediately upstream.

In the second embodiment, the upstream face 25 is located opposite the inner ring 7 of the turbine stage 1 extending immediately upstream.

In order to increase the pressure losses within the seal 9, the seal 9 also comprises at least one pipe 30 formed in the fixed part 20. The pipe 30 opens firstly into the upstream face 25 and on the other hand in the internal radial face 26. This pipe 30 thus makes it possible to derive a part F2 of the bypass flow F1, which bypasses the rotor 3 and one of the rings of the distributor 5 to pass between the mobile part 10 and the fixed part 20 of the seal 9, in order to inject it on the movable part 10. This derived flow F2, which is injected via the pipe 30, therefore opposes the bypass flow F1 which passes through the seal 9, thus increasing the pressure losses, which improves the sealing of the labyrinth and contributes to the performance of the turbine 1.

Preferably, the seal 9 comprises several pipes 30, distributed radially around the axis of revolution X, in order to reduce the pressure losses within the seal 9 over its entire circumference.

In the case where the seal 9 comprises wipers 12 and an abradable 22, 24, the or each pipe 30 is formed in the abradable element 24 and opens into one of the cavities 14 of the seal 9. The derived flow F2 is therefore injected into the cavity 14 and bathes the sides of the wipers 12 which delimit it.

Each pipe 30 comprises a first portion 32 and a second portion 34, the first portion 32 opening into the upstream face 25 of the fixed part 20 while the second portion 34 opens into its internal radial face 26.

The first portion 32 and the second portion 34 of the pipe 30 are preferably of cylindrical shape in order to maximize the pressure drops.

In a first embodiment illustrated in FIG. 1, the second portion 34 of each pipe 30 is inclined relative to a plane P1 which is normal to the axis of revolution X of the seal 9. An angle a has formed between the second portion 34 and the plane P1 is not zero and less than 75 °. It turns out that beyond 75 °, the inclination is likely to pose difficulties in terms of integration. The second portion 34 therefore has an axial orientation relative to the axis of revolution X. A speed of the derivative flow F2 which is injected on the mobile part 10 therefore has a non-zero axial component at the outlet 35 of the pipe 30 (that is to say in an area adjacent to the internal radial face 26 of the fixed part 20). Thus, the second portion 34 of each pipe 30 is bent upstream (that is to say that the projection of the outlet 35 of the pipe 30 on the axis of revolution X is more upstream than the projection of the junction between the first portion 32 and the second portion 34 of the pipe 30) so that the flow is injected in the opposite direction to that of the bypass flow F1 passing through the seal 9. The injected flow forms a curtain of air. This configuration thus makes it possible to increase the pressure losses in the seal 9.

In a second embodiment illustrated in FIG. 2, which can be combined with the first embodiment, the second portion 34 of each pipe 30 is inclined relative to a plane P2 which extends radially and includes the axis of revolution X of the seal 9. An angle β formed between the second portion 34 and the plane P2 is not zero and less than 75 °. Here again, the second portion 24 therefore has a circumferential orientation relative to the axis of revolution X. The speed of the derived flow F2 which is injected then has a non-zero tangential component at the outlet 35 so as to rotate in a opposite direction with respect to the bypass flow F1 which bypasses the fixed part 20. In fact, when the bypass flow F1 passes between the fixed part 20 and the movable part 10 of the seal 9, it is driven by the rotor 3 so that its speed has a non-zero tangential component. The inclination of the second portion 34 of the pipes 30 thus makes it possible to inject the derivative flow F2 in the direction opposite to the direction of rotation of the rotor 3 (and therefore of the bypass flow F1), which significantly increases the pressure losses in the gasket 9.

Where appropriate, whatever the embodiment, the second portion 34 of the seal 9 can be divided into several injection channels 36 each opening into the internal radial face 26. The derived flow F2 is then injected onto the movable part 10 in several different directions, which further increases the pressure losses within the seal 9.

For example, the second portion 34 of the seal 9 can be divided into three injection channels 36, the three injection channels 36 can be included in the same plane (which can be normal to the axis of revolution X or inclined with respect thereto) or in different planes (for example, an injection channel 36 extending in the plane P1 normal to the axis of revolution X and two injection channels 36 inclined with respect to this plan, or vice versa). The recirculation formed by the derived flows F2 during their injection against the movable part 10 improves the disturbance of the flow of the bypass flow F1 in the seal 9 and increases its efficiency.

The size of the injection channels 36 is chosen so that, for a given pipe 30, the sum of the minimum sections of the injection channels 36 is at most equal to the minimum section of the first associated portion 32. It will be noted that, the first portion 32 and the injection channels 36 being preferably cylindrical in order to maximize the pressure drops, their section is substantially constant.

Furthermore, the maximum number of injection channels 36 that can be produced in the fixed part 20 depends on the shape and mechanical strength of the fixed part 20 as well as on the size of the injection channels 36.

Finally, the inclination of the injection channels 34 can be chosen so that the derived flow F2 which is injected into a given cavity 14 from a given line 30 crosses the derived flow F2 which is injected into this cavity 14 from a line 30 adjacent before reaching the bottom of the cavity 14. This crossing of the injected F2 derivative flows thus generates turbulence in the cavity, further improving the pressure drops. In the case where the second portion 34 of the pipes 30 is divided into three injection channels 36, the derived flow F2 leaving the three injection channels 36 of a given pipe 30 can, depending on the inclination chosen for these channels d injection 36, generate turbulence with the adjacent pipes 30 which are situated on either side of their outlet 35, if they cross their flow derived F2 before reaching the bottom of the cavity 14.

The pipe (s) 30 can be made by drilling the fixed part 20. When the fixed part 20 comprises an abradable element 24 in honeycomb, the pipes 30 can be made by drilling the abradable element 24, then a tube of cylindrical shape corresponding to the shape of the bore can be introduced into the bore in order to confine the derived flow in the pipe 30.

As a variant, in particular when the fixed part 20 comprises an abradable element 24 of the honeycomb type, the pipe or pipes 30 can be obtained at the time of manufacture of the abradable element 24 by manufacture by selective melting on a bed of powder. by high energy beam, such as a laser.

Claims (10)

1. Sealing structure (20) of a seal (9) of a turbomachine, the sealing structure (9) extending circumferentially around an axis (X) and being configured to cooperate with friction with at least one wiper (12) carried by a rotor of the turbomachine, the sealing structure comprising an abradable element (24) and having an upstream face (25) intended to be disposed opposite a flow passing through the upstream downstream of the turbomachine and a radially internal face (26) configured to extend opposite the at least one wiper (12), the sealing structure (20) being characterized in that it comprises furthermore at least one pipe (30) formed in the abradable element (24), said at least one pipe (30) opening on the one hand into the upstream face (25) and on the other hand into the radially internal face (26) with a circumferential orientation relative to the axis (X). 2. Sealing structure (20) according to claim 1, wherein the abradable element (24) is preferably annular in a material having a honeycomb structure. 3. Sealing structure (20) according to one of claims 1 or 2, wherein the at least one pipe (30) comprises a first portion (32) and a second portion (34), the first portion (32 ) opening into the upstream face (25) while the second portion (34) opens into the internal radial face (26), the second portion (34) being cylindrical and having a circumferential orientation relative to the axis (X). 4. A sealing structure (20) according to claim 3, in which the second portion (34) of at least one pipe (30) is further inclined upstream so that an air flow (F2 ) passing through the pipe (30) is injected through its outlet (35) with an axial orientation. 5. sealing structure (20) according to one of claims 1 to 4, comprising a series of pipes (30) formed in the abradable element (20) and each opening on the one hand in the upstream face (25) and on the other hand in the internal radial face (26). 6. sealing structure (20) according to one of claims 1 to 5, wherein the at least one pipe (30) comprises a first portion (32) extending from the upstream face (25) of the part fixed (20) and a second portion (34) opening into its internal radial face (26), the second portion (34) dividing so as to form at least two channels (36) having an opposite circumferential orientation and each opening into the internal radial face (26). 7. Sealing structure (20) according to claim 6, in which the second portion (34) divides so as to form three injection channels (36). 8. Sealing structure (20) according to claim 5, each pipe (30) comprising a first portion (32) extending from the upstream face (25) and a second portion (34) opening into the internal radial face ( 26), the second portion (34) of each pipe (30) dividing so as to form at least two injection channels (36) each opening into the internal radial face (26) and being configured so that a flow (F2) which is injected through the injection channels (36) of a given pipe (30) crosses a flow (F2) which is injected through the injection channels of an adjacent pipe (30) before said flows (F2) do not reach at least one wiper (12). 9. A seal (9) comprising a seal structure (20) according to one of claims 1 to 8. 10. A seal (9) according to claim 9, comprising at least two wipers (12) carried by the rotor of the turbomachine, said at least two wipers (12) delimiting with the abradable element (20) at least 5 a cavity (14), the pipe (30) opening into said cavity (14).