Turbomachine gasket

Abstract

The invention relates to a gasket (100) comprising a plurality of gasket sectors, each comprising an inner ring sector (13) connected to an outer ring sector (11) by a return member (12), the return member comprising at least one return arm (200) comprising: - a radially extending outer attachment portion (201) connected to the outer ring sector; - a first circumferentially extending branch (203) connected to the outer attachment portion by an outer bend (202); - a second circumferentially extending branch (205) connected to the first branch by an intermediate bend (204); - a radially extending inner attachment portion (207) connected to the inner ring sector and connected to the second branch by an inner bend (206), and wherein the inner bend is preferentially arranged circumferentially between the outer bend and the intermediate bend.

Description

Description Title of the invention: Turbomachine seal Technical Field

[0001] This presentation concerns sealing devices for aeronautical turbomachines and more specifically sealing gaskets. Prior art

[0002] The design of the ventilation circuits of an aeronautical turbomachine is delicate and represents a potential loss of performance.

[0003] Indeed, the turbomachine is all the more efficient when it operates at high temperatures. However, the materials it is made of then require more significant cooling. Cooling is generally achieved by taking part of the air from the cold air stream, which is detrimental to overall performance.

[0004] In addition, the cooling circuit requires a complex architecture to allow the cooling air to reach the blades to be cooled from the point where it is taken.

[0005] To ensure that the air circuit is not supplied with more cooling air than necessary, and therefore does not unduly impair the performance of the turbomachine, labyrinth seals are generally fitted at the air intake points.

[0006] Such seals ensure controlled airflow at the locations where they are installed. The classic architecture of labyrinth seals includes lips arranged opposite abradable elements that have a honeycomb-type alveolar structure.

[0007] This type of seal, however, has the disadvantage that the wear of the wipers by friction against the abradable elements increases the clearance of the seal over the life of the seal, and thus allows a greater passage of air, which ultimately leads to too much air being drawn in and therefore to a loss of performance of the turbomachine.

[0008] Alternatives to such labyrinth seals are sometimes offered.

[0009] For example, self-adaptive seals, sometimes called hydrostatic, are proposed in the literature.

[0010] Such seals propose to form a seal by arranging a main surface of the seal which includes patterns facing another surface, rotating relative to the main surface and separated therefrom by a predefined clearance.

[0011] It is understood that the sealing involved here is not a strict sealing in the sense that air could not pass through the sealing gasket, but a relative sealing, the purpose of the sealing gasket being to allow a defined quantity of air to pass through, quantified by the predefined clearance.

[0012] The seal is said to be self-adaptive because the surface comprising the patterns interacts with the incident air flow in such a way that: - if the clearance decreases, the air pressure between the seal surface and the facing surface increases, so as to push the seal back and thus bring it back to the predefined clearance; and - if the clearance increases, the air pressure between the seal surface and the facing surface decreases, so that a return element connected to the seal allows the seal to be returned to the predefined clearance.

[0013] It should be noted, however, that the use of such seals is currently limited by the fact that contact between the main surface of the seal and the facing surface must be avoided under all circumstances, and in particular even in unusual, borderline or accidental behavior.

[0014] Current operation therefore does not allow for the production of self-adapting seals that allow a clearance smaller than half a millimeter, while self-adapting seals are an enviable alternative to labyrinth seals, and this is why there remains a need for such seals that could be used with a clearance smaller than current self-adapting seals. Statement of the invention

[0015] The invention aims precisely to meet this need. To this end, it proposes to improve the behavior of the return element of existing self-adaptive sealing joints.

[0016] The invention relates, according to a first of its aspects, to a seal configured to ensure a predefined clearance between said seal and an external surface of a rotor rotatably mounted around an axis A arranged opposite the seal, the seal extending circumferentially around the axis A, the axis A defining an axial direction, and comprising a plurality of seal sectors distributed circumferentially around the axis A, each seal sector comprising an internal ring sector forming the seal connected to an external ring sector by a return member, the seal being characterized in that the return member comprises at least one return arm comprising: - an external attachment portion which extends radially and which is connected to the external ring sector; - a first branch extending circumferentially and connected to the portion by an external elbow; - a second branch extending circumferentially, the second branch being connected to the first branch by an intermediate elbow; - an internal attachment portion which extends radially and which is connected to the internal ring sector and connected to the second branch by an internal elbow, and in which the internal elbow is preferentially arranged circumferentially between the external elbow and the intermediate elbow.

[0017] Such a seal has a return member different from those proposed in the prior art.

[0018] The inventors have developed a return member architecture that allows for excellent responsiveness of the seal sector it supports. This makes it possible to reduce the seal clearance without the risk of the seal coming into contact with the external surface, even in unusual, accidental or complex situations.

[0019] Indeed, the return member described allows better control of the seal and in particular increased responsiveness. Thus, a variation in the position of the internal surface of the seal when it moves relative to the external surface of the rotor is obtained much more quickly than with return members of the prior art.

[0020] This increased responsiveness of the seal sector ensures that the predefined seal clearance can be reduced, compared to prior art seals, without the risk of the external surface of the rotor coming into contact with the seal.

[0021] It is understood that the preset clearance is a "target" clearance, and that it is possible for the clearance to vary slightly around the preset clearance value under operating conditions of the seal. When the seal is in its equilibrium position, the preset clearance ensures that the airflow through the seal is the desired airflow. However, if the clearance increases or decreases, the entire seal will be brought back to the predefined clearance by the spring behavior of the internal ring sectors ensured by the return organs or by the overpressure which then appears under the internal surface of the seal.

[0022] In one embodiment, the axis A of the seal may be the main axis of a turbomachine.

[0023] By "arranged circumferentially between" is meant that, in a projection in a plane perpendicular to the axis A, the internal elbow is projected between the external elbow and the intermediate elbow.

[0024] In one embodiment, the inner elbow is arranged circumferentially between the outer elbow and the intermediate elbow.

[0025] In one embodiment, the thickness of the arm is at any point greater than or equal to 0.5 mm, or even greater than or equal to 0.7 mm, for example between 0.7 mm and 3 mm.

[0026] The thickness of the arm can also be understood as its smallest dimension at any point on it, in a plane perpendicular to the axis A.

[0027] The choice of thickness makes it possible to modify the stiffness of the return member, and the inventors have found that such a thickness of the arm makes it possible to ensure excellent stiffness for the return member.

[0028] In one embodiment, the thickness of the arm is constant.

[0029] In one embodiment, the width of the arm is greater than or equal to 15 mm.

[0030] The width of the arm is understood as the minimum extent of the latter in the axial direction.

[0031] Preferably, the width of the arm is between 50% and 90% of the width of the seal sector.

[0032] This embodiment ensures that the return member constrains the seal sector over a majority of its width and thus prevents one axial end of the seal from being closer to the external surface than the other.

[0033] In the case where the return organ comprises more than one arm, the width of the arm is then defined as the sum of the widths of the different arms.

[0034] In one embodiment, the width of the arm is constant.

[0035] As described, the return member comprises a first and a second circumferentially extending branch.

[0036] By "extending circumferentially" is meant that the length of a branch in the cylindrical frame formed by the axial, circumferential and radial directions includes a projection in the circumferential direction that is greater than in the axial or radial directions.

[0037] The same will be understood for the expressions "extending axially" or "extending radially".

[0038] For example, at any point on a branch, the angle formed by the branch with the circumferential direction may be less than or equal to 30°, or even less than or equal to 20°, or better still less than or equal to 10°.

[0039] The branch is however not necessarily aligned with the circumferential direction due to its weight, its retention by the internal or external attachment portion, and this is why it is defined as "extending circumferentially".

[0040] By similarity, the same is meant for attachment portions extending in a so-called "radially extending" direction.

[0041] For example, at any point of an attachment portion, the angle formed by an attachment portion with the radial direction may be less than or equal to 30°, or even less than or equal to 20°, or better still less than or equal to 10°.

[0042] In one embodiment, the length of the first branch is greater than or equal to 20.0 mm.

[0043] In one embodiment, the second branch has a length less than the length of the first branch.

[0044] This embodiment ensures by geometric construction that the internal elbow is arranged circumferentially between the external elbow and the intermediate elbow.

[0045] In one embodiment, the length of the second branch is between 50% and 90% of the length of the first branch.

[0046] In one embodiment, the connection radius of the internal elbow may be greater than or equal to 1.0 mm, or greater than or equal to 1.5 mm, or greater than or equal to 1.65 mm.

[0047] The "connection radius" of an elbow is understood as the largest radius of the smallest circle in which the entire elbow is inscribed.

[0048] The values ​​proposed for the preferred embodiments represent optimums of the different dimensions identified by the inventors to achieve an even more satisfactory return member.

[0049] More precisely, the stiffness of the return organ is jointly controlled by several parameters, including the thickness of the arm, its width, the length of the first or second branch.

[0050] The values ​​indicated make it possible to achieve a satisfactory stiffness of the return member in order to be able to reduce the predefined play while also taking into account the weight or size issues to be considered for an aeronautical application.

[0051] A return organ of the invention in fact allows a weight saving of up to 15% compared to the return organs of the prior art.

[0052] In one embodiment, the predefined clearance of the seal may be between 0.1 and 1.0 mm or even between 0.5 mm and 1.0 mm.

[0053] This clearance is much smaller than that accessible for the self-adaptive sealing joints of the prior art, but which is accessible thanks to the return members described.

[0054] In one embodiment, the angle formed between the radial extension direction of the external attachment portion and the radial extension direction of the internal attachment portion is greater than or equal to 5°.

[0055] As described above, in one embodiment, the inner elbow is arranged circumferentially between the outer elbow and the intermediate elbow, thereby ensuring that there is no contact between the inner elbow and the outer elbow.

[0056] The values ​​given for the angle make such contact even more unlikely, in all modes of stress on the return organ.

[0057] In one embodiment, the distance measured in the radial direction between the first branch and the outer ring sector may be greater than or equal to 1.0 mm.

[0058] In one embodiment, the distance measured in the radial direction between the first branch and the second branch may be greater than or equal to 1.0 mm.

[0059] In one embodiment, the distance measured in the radial direction between the second branch and the inner ring sector may be greater than or equal to 1.0 mm.

[0060] These embodiments make it possible to avoid any contact during operation between two constituent elements of the return member which could reduce its lifespan.

[0061] In one embodiment, the angle formed by the external elbow may be greater than or equal to 80°.

[0062] This embodiment ensures by construction that the first branch extends circumferentially. In addition, the set of bends ensures that the return member behaves like a spring and the angle formed by the bends allows its mechanical properties to be adjusted.

[0063] In one embodiment, the angle formed by the intermediate elbow is between 170° and 190° or even between 175° and 185°.

[0064] This embodiment ensures a certain parallelism between the first and second branches, which improves the predictability of the mechanical behavior of the return member. In addition, this allows the return member to have behavior close to that of a spring.

[0065] In one embodiment, the angle formed by the intermediate elbow is 180°, which ensures by construction the parallelism between the first and second branches.

[0066] In one embodiment, the angle formed by the internal elbow may be greater than or equal to 80°.

[0067] This embodiment ensures by construction that the second branch extends circumferentially.

[0068] In one embodiment, the connection radius of the intermediate elbow may be greater than or equal to 1.0 mm.

[0069] In one embodiment, the connection radius of the external elbow may be greater than or equal to 1.0 mm.

[0070] The particular choice of the connection radius allows the stiffness of the return member to be precisely adjusted. In fact, the larger the connection radius, the more flexible the elbow.

[0071] As described above, the return member comprises at least one arm as just described.

[0072] The inventors have, however, found that it could be even more advantageous for the return member to comprise two return arms.

[0073] Thus, in one embodiment, the return member may further comprise a second return arm comprising: - an external attachment portion which extends radially and which is connected to the external ring sector; - a first branch which extends circumferentially and which is connected to the external attachment portion by an external elbow; - a second branch which extends circumferentially, the second branch being connected to the first branch by an intermediate elbow; - an internal attachment portion which extends radially and which is connected to the internal ring sector and which is connected to the second branch by an internal elbow, and in which the internal elbow is preferentially arranged circumferentially between the external elbow and the intermediate elbow, the first and second return arms being offset from each other in the axial direction.

[0074] This embodiment allows the arm of the return member to be divided into two identical or different arms. Thus, the mechanical properties of the return member can be improved even more finely.

[0075] In one embodiment, the second leg of the second return arm has a length less than the length of the first leg of the second return arm.

[0076] In an embodiment where the return member comprises at least two arms, the external attachment portion of the first arm and the external attachment portion of the second arm may be aligned in the axial direction, i.e. be positioned at the same circumferential position.

[0077] This embodiment ensures that the force applied to the external ring sector is concentrated at a specific point, which can then be reinforced, for example.

[0078] Alternatively, the outer attachment portion of the first arm and the outer attachment portion of the second arm may be offset in the circumferential direction, i.e. not aligned in the axial direction.

[0079] This embodiment ensures that the force applied to the outer ring sector is distributed within the circumferential dimension of the ring sector.

[0080] In one embodiment, the inner elbow of the second arm is arranged circumferentially between the outer elbow of the second arm and the intermediate elbow of the second arm.

[0081] In an embodiment where the return member comprises at least two arms, the internal attachment portion of the first arm and the internal attachment portion of the second arm may be aligned in the axial direction, i.e. be positioned at the same circumferential position.

[0082] In an embodiment where the return member comprises at least two arms, the internal attachment portion of the first arm and the internal attachment portion of the second arm may be offset in the circumferential direction, for example the angle formed by the radial extension directions at the attachment points of the internal attachment portion of the first arm and the internal attachment portion of the second arm may be greater than or equal to 5°.

[0083] The inventors have found that such an offset of the internal attachment portions of the two arms makes it possible to limit the phenomenon of tilting of the internal ring sector, that is to say that this configuration makes it possible to avoid misalignment of the internal ring sector in the axial direction.

[0084] In other embodiments, the dimensions of the two arms may be different, allowing the mechanical properties of each arm to be specifically adapted to its radial and axial positioning.

[0085] For example, the upstream arm may be longer than the downstream arm, so that the latter exhibits more elastic behavior than the upstream arm.

[0086] Alternatively, the downstream arm may be longer than the upstream arm, so that the latter exhibits more elastic behavior than the downstream arm.

[0087] In one embodiment, the thicknesses and / or widths of one arm may be different from those of the other arm of a return member.

[0088] Introducing geometric differences between the two arms of a return member makes it possible to best define the mechanical and / or elastic properties of each of the two arms at its particular position in the seal.

[0089] In an embodiment where the return member comprises at least two arms, the angle formed by the internal elbow of the second arm is the opposite of the angle formed by the internal elbow of the first arm and in which the angle formed by the external elbow of the second arm is the opposite of the angle formed by the external elbow of the first arm.

[0090] This embodiment allows for two arms which, if traversed from the external attachment to the internal attachment, are arranged in opposite directions to each other along the circumferential direction.

[0091] In fact, one must move in the opposite direction along the circumferential direction to travel the first branch of the two arms coming from their respective attachment portions.

[0092] This embodiment makes it possible to symmetrize the return forces exerted in the circumferential direction and prevents one circumferential end of the internal sector from being more mobile than the other.

[0093] It is also possible, within the limits of technical feasibility, to combine the embodiments which have just been described to accumulate their advantages.

[0094] For example, having arms whose internal attachment portions are offset from each other by an angle greater than or equal to 5° in the axial direction, and whose angle formed by the internal elbow of the second arm is the opposite of the angle formed by the internal elbow of the first arm.

[0095] This embodiment ensures good symmetry of the forces in the circumferential direction while limiting the phenomenon of tilting of the internal ring sector in the axial direction. Brief description of the drawings

[0096] [Fig. 1] Figure 1 schematically represents a turbomachine seen in section.

[0097] [Fig. 2] Figure 2 schematically represents a return member in a first embodiment.

[0098] [Fig. 3] Figure 3 shows a different view of the return member in the first embodiment.

[0099] [Fig. 4] Figure 4 schematically represents a return member in a second embodiment different from the first.

[0100] [Fig. 5] Figure 5 shows a different view of the return member in the second embodiment.

[0101] [Fig. 6] Figure 6 schematically represents a return member in a third embodiment different from the first and second embodiments.

[0102] [Fig. 7] Figure 7 shows a different view of the return member in the first embodiment different from the first and second embodiments. Description of the embodiments

[0103] The invention is now described by means of figures, present for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0104] Figure 1 represents, in section along a vertical plane passing through its main axis A, a double-flow turbojet 1. It comprises from upstream to downstream according to the circulation of the air flow, a fan 2, a low-pressure compressor 3, a high-pressure compressor 4, a combustion chamber 5, a high-pressure turbine 6, and a low-pressure turbine 7.

[0105] In the present application, the relative terms of positioning, for example “upstream”, “downstream”, “internal” and “external”, will be understood in relation to the horizontal axis A of the casing defining the axial direction, traveled in the direction of flow of the main and secondary air flows of the turbomachine.

[0106] Thus, an element called "upstream" will be crossed before an element called "downstream" and an element called "internal" will be closer to axis A than an "external" element.

[0107] First, Figure 2, and more generally Figures 2 to 7, present the directions used in the application.

[0108] The axial direction D A which is understood as the direction aligned with the main axis A of the turbomachine. The circumferential direction D c in which the seal extends and forms a circle around the axial direction D A . The radial direction D R defines a radius of the circle formed by the circumferential direction D c and having as its center the axial direction D A .

[0109] Figure 2 schematically represents a return member in one embodiment.

[0110] More specifically, Figure 2 represents a seal 100 comprising a plurality of seal sectors distributed circumferentially around the axis A, each seal sector comprising an internal ring sector 13 forming the seal connected to an external ring sector 11 by a return member 12, the seal being characterized in that the return member comprises at least one return arm 200 comprising: - an external attachment portion 201 extending radially and connected to the external ring sector; - a first branch 203 extending circumferentially and connected to the portion by an external elbow 202; - a second branch 205 extending circumferentially, the second branch being connected to the first branch by an intermediate elbow 204; - an internal attachment portion 207 extending radially connected to the internal ring sector and connected to the second branch by an internal elbow 206, the internal elbow 206 being arranged circumferentially between the external elbow 202 and the intermediate elbow 204.

[0111] It can be noted that in the embodiment shown, the second branch 205 has a length less than the first branch 203.

[0112] Figure 2 further describes the width E of the arm 200 understood in the axial direction D A .

[0113] As described, the width E of the arm 200 is between 50% and 90% of the width of the seal sector.

[0114] In one embodiment, which is also that shown in FIG. 2, when the width E of the arm is less than 90%, the internal attachment portion 207 can be positioned so that the internal attachment portion 207 is in contact with the downstream of the internal ring sector 13.

[0115] Alternatively, the internal attachment portion 207 could be in contact with the upstream of the internal ring sector 13 or else in such a way that it is not in contact with either the upstream or the downstream of the internal ring sector 13, for example centered on the internal ring sector 13.

[0116] The same applies to the external attachment portion 201.

[0117] In one embodiment, which is also that shown in FIG. 2, when the width E of the arm is less than 90% of the width of the external ring sector 201, the external attachment portion 201 can be positioned so that the external attachment portion 201 is in contact with the upstream of the external ring sector 201.

[0118] Alternatively, the external attachment portion 207 could be in contact with the downstream of the external ring sector 11 or else in such a way that it is not in contact with either the upstream or the downstream of the external ring sector 11, for example centered on the external ring sector 11.

[0119] In one embodiment, it is not necessary for the inner attachment portion 207 and the outer attachment portion 201 to be positioned axially at the same location on the inner ring sector 13 and the outer ring sector 11 respectively.

[0120] In one embodiment, the width of the arm may vary from one end of the arm to the other, and the minimum width of the arm will then be called the width E of the arm.

[0121] Figure 2 further illustrates a secondary sealing member 14 as described above. The secondary sealing member may comprise a plurality of circumferentially distributed elements.

[0122] Although the representation of the secondary sealing member 14 is truncated in FIG. 1 to make the elements 11, 12 and 13 visible, the secondary sealing member 14 covers in one embodiment the entire circumference of a seal as described above.

[0123] For example, there may be as many, more, as many or fewer secondary sealing member portions as there are seal sectors.

[0124] Figure 2 further illustrates the circumferential space 21 between two sealing gasket sectors 13.

[0125] In one embodiment, the circumferential ends of the inner ring sectors have an angle of inclination relative to the axial direction D A between 30° and 90°.

[0126] This inclination of the circumferential ends of the inner ring sectors of the seal sectors allows for movement of the inner ring sectors of the seal sectors relative to each other.

[0127] Indeed, during use, the radial displacement of the inner ring sectors is not uniform. An inclination of the ends of the inner ring sectors makes it possible to reduce the clearance existing between two inner ring sectors, thus improving the effectiveness of the seal.

[0128] Figure 3 shows an arm of a return member of the same embodiment as that of Figure 2, but in a different view, here in a plane perpendicular to the axial direction D A .

[0129] Figure 3 illustrates other dimensions of the elements of a return member as described.

[0130] First of all, Figure 3 shows here schematically the external surface 500 opposite the internal surface of the internal ring sector.

[0131] The surface is separated from the seal by the clearance j, measured in the radial direction.

[0132] Figure 3 further illustrates the length Lt of the first branch 203, and the length L2 of the second branch 205.

[0133] As described the length Lt of the first branch 203 may be greater than or equal to 20.0 mm.

[0134] The maximum length of the first branch 203 is limited by the curvature of the outer ring sector. For example, the length Lt of the first branch 203 may be between 20.0 mm and 70 mm.

[0135] Figure 3 further illustrates the angle P of the outer bend 201 and the angle 5 of the inner bend 206.

[0136] The angle of an elbow is understood as the angle formed by the two ends of the elbow.

[0137] Preferably, the angles and 5 are greater than or equal to 80°, for example between 80° and 90°.

[0138] Such angles allow effective recall of the first and second branches 203, 205.

[0139] Figure 3 further illustrates the angle a formed by the arm of the return member.

[0140] More precisely, angle a is defined as the angle formed by the radial direction D Rat the attachment point of the internal attachment portion to the internal ring sector and the radial direction D R at the point of attachment of the outer attachment portion to the outer ring sector.

[0141] The angle a may be greater than or equal to 5°. Preferably, a is between 5° and 20°.

[0142] Figure 3 further illustrates the connecting radii Ri of the external elbow 202, R2 of the intermediate elbow 204 and R3 of the internal elbow 206.

[0143] Figure 3 illustrates the distance J1 between the first branch and the outer ring sector 11 and the distance J2 between the second branch 205 and the inner ring sector 13.

[0144] These two distances are understood as the smallest distance, in the radial direction D R , between the first branch 203 and the outer ring sector 11 for J1 and as the smallest distance, in the radial direction D R, between the second branch 205 and the internal ring sector 13 for J2.

[0145] Indeed, not all the points of the first branch 203 are equidistant from the external ring sector 11 and not all the points of the second branch 205 are equidistant from the internal ring sector 13.

[0146] Figure 3 also illustrates the distance J3 between the first branch 203 and the second branch 205, or more precisely as the smallest distance, in the radial direction D R , between the first branch 203 and the second branch 205.

[0147] Preferably, J1 is greater than or equal to 1.0 mm, for example, between 1.0 and 5.0 mm.

[0148] This ensures a small footprint of the return member while ensuring that there cannot be any contact between the first branch 203 and the external ring sector 11, even in abnormal or accidental behavior.

[0149] Preferably, J2 is greater than or equal to 1.0 mm, for example, between 1.0 and 5.0 mm.

[0150] This ensures a small footprint of the return member while ensuring that there can be no contact between the second branch 205 and the internal ring sector 13, even in abnormal or accidental behavior.

[0151] Preferably, J3 is greater than or equal to 1.0 mm, for example, between 1.0 and 5.0 mm.

[0152] This ensures a small footprint of the return member while ensuring that there can be no contact between the first branch 203 and the second branch 205, even in abnormal or accidental behavior.

[0153] In one embodiment, the position of the inner attachment portion 207 with respect to the inner ring sector 13 in the circumferential direction D c can vary between 10% and 90% of the length of the inner ring sector in this direction.

[0154] In other words, the distance between the first circumferential end of an inner ring sector 11, and the inner attachment portion 207 may be between 10% and 90% of the length of the inner ring sector in the circumferential direction.

[0155] This embodiment makes it possible to best adapt the behavior of the seal and in particular to more precisely control the radial displacement of the internal surface of the internal ring sector.

[0156] For example, this allows to control the behavior of the seal in the circumferential direction D c depending on whether, for example, we want the front or rear end of the seal to be the first to return to the equilibrium position.

[0157] Figure 3 also shows the thickness e of the arm of the return member.

[0158] The thickness e is understood as the smallest dimension of the arm, and makes it possible to define the mechanical behavior of the arm, in particular its stiffness.

[0159] Figures 4 and 5 show two views of the same embodiment, which is different from the embodiment shown in Figures 2 and 3.

[0160] In particular, the return member of the embodiments of figures 4 and 5 have two arms 200, 300.

[0161] The return member thus has an upstream arm 200 and a downstream arm 300.

[0162] The two arms 200, 300 each include: - an external attachment portion 201, 301 extending radially connected to the external ring sector 11; - a first branch 203, 303 extending circumferentially and connected to the portion by an external elbow 202, 302; - a second branch 205, 305 extending circumferentially, the second branch being connected to the first branch by an intermediate elbow 204, 304; and - an internal attachment portion 207, 307 extending radially and which is connected to the internal ring sector 13 and connected to the second branch 205, 305 by an internal elbow 206, 306.

[0163] Items numbered with 2 for hundreds digit refer to the first arm 200, and those with 3 for hundreds digit refer to the second arm 300.

[0164] In one embodiment, the second branch 305 of the second return arm 300 has a length less than the length of the first branch 302 of the second return arm 300.

[0165] The first arm 200 has a width Ea and the second arm 300 has a width Eb

[0166] In one embodiment, the width of each arm may be identical, which ensures symmetrical behavior of the seal in its axial direction, i.e. between the upstream and downstream of the seal.

[0167] This is not necessary, however, and it is possible to obtain a more finely defined behavior, for example precisely adapted to the behavior of the air flow by varying the respective width of one arm 200, 300 relative to the other 300, 200.

[0168] As shown in Figures 4 and 5, the internal attachment portions 207, 307 of the first arm 200 and the second arm 300 may be aligned in the axial direction D A .

[0169] In the embodiment precisely illustrated in FIG. 5, the two arms 200, 300 may have identical dimensions except that the angles a And b internal elbows 202 and 302 and angles 5a and 5 b are opposed.

[0170] To obtain the signed measure of an angle, it is necessary to project it in the circumferential direction D c The positive direction is then defined according to the usual mathematical rule called the “right hand thumb rule” or “Maxwell’s corkscrew rule”.

[0171] In such an embodiment, by construction, it then appears that the angles a a and has b are also identical but of opposite signs.

[0172] This embodiment ensures, through construction symmetry, better symmetry of the behavior of the seal in the circumferential direction D. c .

[0173] Figures 6 and 7 illustrate an embodiment still different from those described above.

[0174] Figure 6 shows a return member 12 comprising two arms 200 and 300.

[0175] Figure 7 illustrates other values ​​relevant to behavior optimization, including the angles £ ex t and £ int .

[0176] The angle £ ex test defined as the angle formed between the external attachment portions extended in the radial direction D R of both arms 200, 300.

[0177] Preferably, the angle £ ex test between 0° and 25°.

[0178] The angle £ in test defined as the angle formed between the external attachment portions extended in the radial direction D R of both arms 200, 300.

[0179] Preferably, the angle £ ex test between 0° and 15°.

[0180] By geometric construction, and as described in Figure 7, we can deduce the geometric relationship £ ex t = £int + a a + a b .

[0181] The proposed angles s ensure a seal behavior that is adapted to the target behavior in the circumferential direction.

[0182] Embodiments with more than two arms for the return member 12 are also conceivable.

[0183] The advantages of having a greater number of arms in the return member is to be able to define and control the behavior of the internal ring sector 13 even more finely than when the return member 12 comprises a single arm 12.

[0184] A compatible seal of a return member as described is now described.

[0185] In one embodiment, the seal may comprise a plurality of seal sectors distributed circumferentially around the axis A, each seal sector comprising an inner ring sector connected to an outer ring sector by a return member, the seal being characterized in that the inner surface of each inner ring sector comprises at least one row of patterns hollowed out from the inner surface of the inner ring sectors, each of the patterns having an elongated shape extending in a direction oblique to the axial direction and being separated from another pattern by a non-hollowed portion of the inner surface.

[0186] Such a seal architecture differs radically from a labyrinth seal.

[0187] However, the internal surface of the internal ring sector does ensure aerodynamic sealing by ensuring a predefined clearance with the facing surface.

[0188] It is understood that the sealing involved here is not a strict sealing in the sense that air could not pass through the seal, but a relative sealing, the purpose of the seal being to allow a defined quantity of air to pass through.

[0189] The "circumferential distribution" of the joint sectors is intended to mean that each joint sector defines a portion of the circumference of the joint, and that the set of joint sectors makes it possible to obtain the complete joint.

[0190] In one embodiment, the circumferential distribution is regular, and each seal sector then represents an equal portion of the circumference of the seal.

[0191] It is understood that the predefined clearance is a "target" clearance, and that it is possible that the clearance may vary slightly around the predefined clearance value under operating conditions of the seal. When the seal is in its equilibrium position, the predefined clearance ensures that the airflow through the seal is the desired airflow. However, if the clearance increases or decreases, the seal will be returned to the predefined clearance in relation to a spring behavior of the internal ring sectors ensured in particular by the return members.

[0192] More specifically, if the seal clearance becomes smaller than the predefined clearance, the pressure radially under the inner surface of the ring sectors increases and the inner ring sector then moves so as to increase the clearance, whereas if the seal clearance becomes larger than the predefined clearance, the return member exerts a force greater than the pressure exerted radially under the inner surface of the inner ring sectors, the latter then returning to their equilibrium positions, i.e. to the predefined clearance.

[0193] This aerodynamic balance prevents the internal surface of the internal ring sector from coming into contact with the opposite surface at any time, and the seal differs in this from labyrinth seals. This avoids the wear problem that can be encountered with conventional labyrinth seals.

[0194] Generally, the patterns present in the thickness of the internal surface of the internal ring sector make it possible to improve the aerodynamic behavior of the seal.

[0195] In one embodiment, the clearance between the internal surface of the internal ring sector and the radially facing surface may be between 0.1 and 1.0 mm or even between 0.5 mm and 1.0 mm.

[0196] The patterns carved from the inner surface of the inner ring sector allow the behavior of the seal to be modified, in particular by further increasing the pressure exerted by the air on the inner surface of the inner ring sector when the latter approaches the facing surface.

[0197] This makes contact between the inner surface of the inner ring sector and the radially facing surface even more unlikely, thus reducing the risk of seal wear.

[0198] The patterns are said to be "carved from the inner surface of the inner ring sector" because it must be understood that the patterns form a relief in the radial direction of the ring sector, i.e. the direction perpendicular to the axis A, and from the inner surface of the inner ring sector.

[0199] The patterns have elongated shapes, for example parallelepiped. It is thus understood that the depth profile of the internal surface of the internal ring sector defining a pattern is identical in the circumferential direction over a given distance which will be arbitrarily called the pattern width.

[0200] The second dimension of the pattern, in the plane of the inner surface of the inner ring sector will be arbitrarily called length.

[0201] It is not outside the scope of the invention if the width is greater than the length but, for the sake of simplicity, we will only describe cases in which a pattern is longer than it is wide.

[0202] The dimensions are characterized by width and length for simplicity, but the invention is not limited to the case where the patterns are rectangular and it concerns long, and more precisely parallelepiped, patterns.

[0203] Thus, and as described, the length of a pattern is in an oblique direction relative to the axial direction.

[0204] The inclination quantifying the "oblique" characteristic of the patterns is understood as the angle defined between the direction in which the length of a pattern extends and the axial direction.

[0205] In one embodiment, the patterns have an angle of inclination relative to the axial direction, this angle of inclination being greater than or equal to 30°.

[0206] The angle of inclination of the patterns allows on the one hand to inscribe more patterns or patterns of greater length on the surface of an internal ring sector of given dimensions.

[0207] In one embodiment, the angle of inclination of the patterns is between 30° and 60°, or even between 30° and 45°.

[0208] In fact, this also ensures that the air flow, which may have a tangential speed due to the rotation of several elements with which it may be in contact, enters the pattern without seeing too great a discontinuity.

[0209] Preferably, the angle of inclination is oriented in the same direction as the tangential velocity of the air flow, or in the direction of rotation of the facing surface relative to the internal ring sector.

[0210] The surface facing the seal is a surface of a rotor mounted to rotate around the axis A, for example the rotor of a high-pressure turbine of an aeronautical turbomachine. In one embodiment, the patterns may be tilted in the same direction as the direction of rotation of the rotor.

[0211] This ensures that the orientation of the patterns is in the direction of the tangential velocity of the air passing through said patterns, which improves the overall performance of the seal.

[0212] The depth of a pattern is understood as the distance between the inner surface of the undug inner ring sector and the surface of the pattern, measured perpendicular to the surface of the inner ring sector, i.e. in the radial direction.

[0213] In one embodiment, each inner surface of the inner ring sectors comprises a plurality of rows of patterns in the radial direction, each formed from a plurality of patterns in the circumferential direction.

[0214] For example, each inner surface of the inner ring sectors comprises a first and a second row of patterns, each of the rows comprising a plurality of patterns distributed in the circumferential direction.

[0215] In an embodiment where the joint comprises two rows of patterns, the patterns of the first row of patterns and the patterns of the second row of patterns have a flat portion over which the depth does not vary, and the depth of this flat portion will be considered to be the depth of the pattern. If the patterns do not have such a flat portion or if they have more than one flat portion, the depth of the pattern will be called the average depth of the pattern.

[0216] The embodiments described now make it possible to ensure a faster return of the seal to its predefined clearance, and therefore to its equilibrium position.

[0217] Furthermore, they ensure that the inner surface of the inner ring sector does not come into contact with the facing surface in intended or even accidental operating modes.

[0218] In an embodiment where the seal comprises at least two rows of patterns, the patterns of the first row of patterns have a depth greater than or equal to the patterns of the second row of patterns.

[0219] It is understood that the first row of patterns is the first row encountered by the airflow passing the seal. In the case where there is only one row of patterns, the first row is the row of patterns.

[0220] If there are two rows of patterns, the first row of patterns can also be characterized as the "upstream row", and the second row of patterns as the "downstream row".

[0221] In one embodiment, each pattern of the first row of patterns has a planar downstream pattern area of ​​constant, non-zero depth and an upstream pattern area in which the depth varies in a decreasing manner while remaining greater than the constant depth of the downstream pattern area.

[0222] The downstream zone performs the general role of the pattern which is to increase the pressure on the internal surface of the inner ring sector when the clearance is lower than the predefined clearance.

[0223] In one embodiment, the upstream area of ​​each pattern of the first row of patterns may have a rounded, i.e. convex, shape.

[0224] In this embodiment, the upstream zone ensures low pressure loss at the inlet of the seal. This improves the efficiency of the seal as a whole.

[0225] Furthermore, in an embodiment where the seal comprises at least two rows of patterns, since two patterns are separated by an unhollowed portion of the inner surface of the inner ring sector and the depth of the downstream portion of the pattern of the first row is non-zero, this embodiment ensures that air flowing through the first pattern encounters a wall directed in the radial direction at the end of the first pattern.

[0226] These walls ensure that the force exerted by the air radially under the internal surface of the internal ring sector is directed in the radial direction, and this independently of its tangential speed, which increases the performance of the seal.

[0227] In one embodiment, the depth of the downstream portion of the first row pattern may be between 1.5 times and 2.5 times the predefined clearance for the seal.

[0228] The inventors have in fact noted that these depth values ​​ensure excellent pressure distribution in the seal, which improves the seal's effectiveness.

[0229] In an embodiment where the inner surface of each inner sector comprises at least two rows of patterns, each pattern of the second row of patterns has a planar downstream pattern zone of constant, non-zero depth and an upstream pattern zone in which the depth of the pattern varies increasingly from the inner surface of the inner ring sector while remaining less than the constant depth of the downstream pattern zone.

[0230] This embodiment allows for a new compression of the air entering the pattern, ensuring an additional force under the seal, and therefore better control of the latter in its return to the equilibrium position.

[0231] In one embodiment, each inner surface of the inner ring sectors includes a first and a second row of patterns, the first row of patterns being offset in the circumferential direction from the second row of patterns.

[0232] For example, the patterns in the second row are offset in the circumferential direction relative to the patterns in the first row by a distance between 0.25 times the width of a pattern and 0.75 times the width of a pattern, or even between 0.45 times the width of a pattern and 0.55 times the width of a pattern.

[0233] This embodiment ensures that the air flow passing through the seal and having a tangential speed encounters patterns from both rows of patterns during its passage through the sealing joint.

[0234] In one embodiment, the inner surface of the inner ring sector may also comprise more than two rows of patterns, for example between two and five rows of patterns.

[0235] In one embodiment, the inner surface of each of the first and second rows of patterns comprises a plurality of patterns distributed in the circumferential direction.

[0236] In one embodiment, a row of patterns may comprise more than five patterns, for example between 5 and 20 patterns, preferably between 7 and 15 patterns, or even between 9 and 11 patterns.

[0237] In one embodiment, the inner surface of the inner ring sector may also comprise after the last pattern an unhollowed surface of the inner surface of the inner ring sector and then a portion of increase in thickness between the unhollowed surface and the downstream end of the inner ring sector.

[0238] Such a profile helps reduce pressure heterogeneity at the seal outlet, which reduces the risk of vibrational instability of the seal due to the wake of the air passing through it.

[0239] In one embodiment, the outer ring sectors form an outer shell and the inner ring sectors have ends arranged end-to-end in the circumferential direction around the axis A.

[0240] In such an embodiment, the circumferential ends of the inner ring sectors may have an angle of inclination relative to the circumferential direction of between 30° and 90°.

[0241] This inclination of the circumferential ends of the inner ring sectors of the joint sectors allows for movement of the inner ring sectors of the joint sectors relative to each other.

[0242] Indeed, during use, the radial displacement of the inner ring sectors is not uniform. An inclination of the ends of the inner ring sectors makes it possible to reduce the clearance existing between two inner ring sectors, thus improving the efficiency of the seal.

[0243] In one embodiment, the seal comprises between 8 and 12 seal sectors.

[0244] For reasons of mechanical strength, space requirements, and to ensure the flatness of the seal surface, it is preferable to have as many sectors as possible. However, for aerodynamic reasons, it is necessary to avoid leaks and therefore minimize the number of seal sectors. The inventors found that such a number of seal sectors was an optimal compromise between these two opposing effects.

[0245] In one embodiment, the outer ring sectors of a seal may be a single piece, for example a ferrule. In other words, there is no physical separation between two circumferentially successive outer ring sectors.

[0246] In one embodiment, such a ferrule may be monolithic, i.e. made in a single piece without connection. In such a case, it will be considered that an angular portion of the ferrule can be considered as an external ring sector.

[0247] In one embodiment, the seal further comprises a secondary sealing member disposed radially above the inner ring sector so as to prevent air from axially passing through the seal above the ring sector.

[0248] Such a secondary sealing member makes it possible to ensure the sealing of the elements of the seal located radially above the internal ring sector. In other words, such a secondary sealing member ensures that the only path allowing air upstream of the seal to pass through it passes radially between the internal surface of the internal ring sector and the external surface opposite the seal.

[0249] Such a secondary member is known as such to those skilled in the art and may, for example, be chosen from a brush seal, a set of tabs, or a tile.

[0250] The embodiments of the joint described below are compatible with the embodiments of the return member, so that the particular technical effects of certain embodiments can be obtained jointly if desired.

Claims

Claims

1. Seal (100) configured to ensure a predefined clearance (j) between said seal and an external surface (500) of a rotor rotatably mounted around an axis A arranged opposite the seal, the seal extending circumferentially around the axis A, the axis A defining an axial direction (D A ) and comprising a plurality of seal sectors distributed circumferentially around the axis A, each seal sector comprising an inner ring sector (13) connected to an outer ring sector (11) by a return member (12), the seal being characterized in that the return member (12) comprises at least one return arm (200) comprising: - an external attachment portion (201) which extends radially and which is connected to the external ring sector (11); - a first branch (203) extending circumferentially and connected to the external attachment portion (201) by an external elbow (202); - a second branch (205) extending circumferentially, the second branch (205) being connected to the first branch (203) by an intermediate elbow (204); - an internal attachment portion (207) which extends radially and which is connected to the internal ring sector (11) and connected to the second branch (205) by an internal elbow (206), and in which the internal elbow (206) is preferentially arranged circumferentially between the external elbow (202) and the intermediate elbow (204).

2. A seal according to claim 1, wherein the thickness (e) of the arm is at any point greater than or equal to 0.5 mm.

3. A seal according to claim 1 or 2, wherein the length (L) of the first leg (203) is greater than or equal to 20.0 mm.

4. A seal according to any one of claims 1 to 3, wherein the second branch (205) has a length (L2) less than the length (L of the first branch (203).

5. A seal according to claim 4, wherein the length (L2) of the second branch (205) is between 50% and 90% of the length (LJ) of the first branch (203).

6. A seal according to any one of claims 1 to 5, wherein the angle formed between the radial extension direction of the attachment portion External Tl (201) and the radial extension direction of the internal attachment portion (206) is greater than or equal to 5°.

7. A seal according to any one of claims 1 to 6, wherein the internal bend (206) has a connection radius greater than or equal to 1.0 mm.

8. A seal according to any one of claims 1 to 7, which further comprises a second return arm (300) comprising: - an external attachment portion (301) which extends radially and which is connected to the external ring sector (11); - a first branch (303) which extends circumferentially and which is connected to the external attachment portion (301) by an external elbow (302); - a second branch (305) which extends circumferentially, the second branch (305) being connected to the first branch (303) by an intermediate elbow (304); - an internal attachment portion (307) which extends radially and which is connected to the internal ring sector (11) and which is connected to the second branch (305) by an internal elbow (306), and in which the internal elbow (306) is preferentially arranged circumferentially between the external elbow (302) and the intermediate elbow (304), the first and second return arms (200, 300) being offset from each other in the axial direction.

9. A seal according to claim 8, wherein the second branch (305) of the second return arm (300) has a length less than the length of the first branch (303) of the second return arm (300).

10. A seal according to claim 8 or 9, wherein the outer attachment portion (201) of the first arm (200) and the outer attachment portion (301) of the second arm (300) are aligned in the axial direction.

11. A seal according to any one of claims 8 to 10, wherein the inner attachment portion (207) of the first arm (200) and the inner attachment portion (307) of the second arm (300) are aligned in the axial direction.

12. A seal according to one of claims 8 to 11, wherein the angle formed by the internal elbow (306) of the second return arm (300) is the opposite of the angle formed by the internal elbow (206) of the first return arm (200) and wherein the angle formed by the external elbow (302) of the second return arm (300) is the opposite of the angle formed by the external elbow (202) of the first return arm (200).

13. Seal according to one of claims 8 to 12, wherein the angle formed between the radial extension direction of the internal attachment portion (207) of the first return arm (200) and the radial extension direction of the internal attachment portion (207) of the second return arm (206) is greater than or equal to 5°.

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