Sealing assembly for turbomachine

Abstract

Sealing Assembly for Turbomachinery The invention relates to a sealing assembly for a turbomachine (1) comprising a sealing gasket (300) configured to provide a predefined clearance (j) between said sealing gasket and an external surface (52) of a rotor mounted to rotate about an axis A, the axis A defining an axial direction (DA), the sealing gasket extending circumferentially around the axis A and the external surface (51, 52) being disposed opposite the sealing gasket, the sealing assembly being characterized in that it further comprises an air straightening element (200) comprising at least one row of blades extending radially, the air straightening element being located upstream of the sealing gasket, the air straightening element being configured to straighten the air intended to pass through the sealing gasket. Figure for the abstract: Fig. 4

Description

Title of the invention: Sealing assembly for turbomachine Technical field

[0001] The present disclosure relates to sealing assemblies for aeronautical turbomachines. 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 constituting it then require greater cooling. Cooling is generally achieved by taking part of the air from the cold air stream, which is detrimental to overall performance.

[0004] Furthermore, the cooling circuit requires the implementation of a complex architecture to allow the cooling air to reach the blades to be cooled from the location where it is taken.

[0005] In order 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 provided at the air sampling locations.

[0006] Such seals provide controlled air passage at the locations where they are arranged. The conventional architecture of labyrinth seals comprises lips arranged opposite abradable elements which have a honeycomb-type alveolar structure.

[0007] This type of seal nevertheless 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 proposed.

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

[0010] Such seals propose forming a seal by arranging a main surface of the seal which comprises patterns facing another surface, rotating relative to the main surface and separated from it 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 seal, but a relative sealing, the purpose of the seal sealing being to let through a defined quantity of air, 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 surface of the seal 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 however be noted 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] The proper functioning of these seals is closely linked to the pressure conditions upstream and downstream of the seal which generate a force under the self-adapting seal.

[0015] In the conventional architecture of turbomachines, these pressure conditions are imposed by the operating conditions of the turbomachine and cannot in any case be adapted to promote the operation of the seals.

[0016] There therefore remains a need to improve the operation of the seals without having to modify the operating conditions of the turbomachine. Statement of the invention

[0017] The invention aims precisely to meet this need.

[0018] The invention thus relates, according to a first of its aspects, to a sealing assembly for a turbomachine comprising a seal configured to ensure a predefined clearance between said seal and an external surface of a rotor rotatably mounted about an axis A, the axis A defining an axial direction, the seal extending circumferentially about the axis A and the external surface being arranged opposite the seal, the sealing assembly being characterized in that it further comprises an air straightening member comprising at least one row of blades which extend radially, the air straightening member being located upstream of the seal, the air straightening member being configured to straighten the air intended to pass through the seal.

[0019] In other words, the rectifying member makes it possible to cancel the tangential component of the air reaching the seal.

[0020] It is indeed to the credit of the inventors to have understood and documented that the tangential speed of the air reaching the seal plays an important role in the operation of the seal.

[0021] The tangential velocity of the air reaching the seal is explained by the fact that the seal is in contact with rotating moving parts in the turbomachine. It is usually considered beneficial for seals, because it allows the clearance at equilibrium to be reduced.

[0022] However, the inventors have found that at the cost of a slight increase in the clearance at equilibrium, straightening the incident air, that is to say depriving it of its tangential velocity component, makes it possible to reduce by at least 20% the pressure ratio between the upstream and downstream of the seal necessary for the seal to start moving and return to equilibrium.

[0023] The loss due to the increase in the equilibrium clearance is thus largely compensated by the assurance that the seal returns more quickly to its equilibrium clearance in all engine speeds of the turbomachine.

[0024] In one embodiment, axis A may be the main axis of a turbomachine.

[0025] Such an assembly makes it possible in particular to benefit from the advantages described above and in particular to have a seal whose pressure ratio between the upstream and downstream of the seal necessary to return the seal to its equilibrium position is greatly reduced, compared to a seal not comprising an air straightening member.

[0026] It is understood that the sealing involved here is not a strict sealing in the sense that air could not pass through the sealing assembly, but a relative sealing, the purpose of the sealing joint being to allow a defined quantity of air to pass through.

[0027] The air that can pass through the sealing assembly makes it possible, for example, to prevent the occurrence of pumping phenomena, or to take a portion of the air necessary for cooling, for example for cooling hot parts.

[0028] As described, the vanes of the air straightening member extend radially, i.e., their leading edges and trailing edges extend in the radial direction.

[0029] As described, these blades, and more generally the air straightening member, are configured to straighten the air intended to pass through the seal. It is understood by this that the profile of the blades, i.e. their extent in the other two dimensions of space, are chosen so that incident air having a non-zero tangential velocity component passing through the air straightening member emerges therefrom with a reduced tangential velocity component.

[0030] In one embodiment, the air straightening member comprises from 10 to 40 fixed blades (including terminals) whose profile is defined in such a way that it allows the cancellation of the tangential component of the air reaching the seal.

[0031] This embodiment makes it possible to ensure a straightening of the air which reduces by at least 20% the ratio between the pressure upstream and downstream of the seal necessary to return the seal to its equilibrium clearance, compared to a sealing seal alone.

[0032] In one embodiment, the distance between the inlet of the air straightening member and the upstream edge of the seal may be between 10 mm and 20 mm.

[0033] This embodiment allows on the one hand for the straightening of the air to be done while ensuring a laminar flow, and on the other hand by reducing as much as possible the dimensions of the straightening member to minimize its weight.

[0034] The inlet of the air straightening member considered here is the first element of the air straightening member reached by the incident air. In one embodiment, the inlet of the air straightening member may be the leading edge of the blades of the air straightening member.

[0035] In one embodiment, the distance between the outlet of the air straightening member and the upstream edge of the seal may be between 2.0 mm and 5.0 mm.

[0036] This embodiment makes it possible to obtain a limited axial size of the entire invention.

[0037] The outlet of the rectifier member considered here is the last element of the rectifier member crossed by the incident air. In one embodiment, the outlet of the rectifier member may be the trailing edge of the blades of the air rectifier member.

[0038] In one embodiment, the air straightening member may comprise a distancing member which makes it possible to calibrate the gap between the air straightening member and the seal.

[0039] In one embodiment, the distancing member is a calibrated protrusion arranged in the axial direction.

[0040] In one embodiment, the air straightening member comprises a distancing member secured to the air straightening member.

[0041] In one embodiment, the sealing assembly described above is arranged radially between the external surface of a rotor mounted to rotate around the axis A and a fixed part of a turbomachine casing.

[0042] In one embodiment, the fixed portion of a turbomachine casing comprises a radial recess.

[0043] Such a radial recess allows for easier arrangement of the seal, the latter being able to be arranged simply in abutment against the radial recess of the casing.

[0044] In one embodiment, the sealing assembly may be arranged radially between a fixed part of a turbomachine casing and the external surface of the rotor mounted to rotate around the axis A, and in which the seal is arranged axially between a radial recess of the fixed part of the turbomachine casing and the distancing member of the air straightening member.

[0045] This embodiment ensures simplified installation of the sealing assembly.

[0046] In one embodiment, the air straightening device may include a distancing member that provides axial separation between the outlet of the air straightening device and the seal.

[0047] In such an embodiment, the distancing member preferably has an axial length equal to the desired length between the downstream of the air straightening member and the inlet of the seal.

[0048] This allows for easier arrangement of the air straightening member, as the latter can then be arranged with the distancing member abutting against the seal.

[0049] In one embodiment, the seal may be arranged axially between a distancing member of an air straightening member described above, and a radial recess provided in the fixed part of the casing.

[0050] In an identical or different embodiment, the air straightening device may comprise a radially external fixing flange which is mounted against an external radial flange of the fixed portion of the turbomachine casing.

[0051] Such an embodiment allows easy arrangement of the air straightening member in a turbomachine, its arrangement relative to the fixed portion of the casing being achieved by abutting the radially external fixing flange of the air straightening device against the radially external fixing flange of the fixed portion of the casing.

[0052] In one embodiment, the sealing assembly may be arranged radially between a fixed portion of a turbomachine casing and an external surface of the rotor rotatably mounted about the axis A and in which the air straightening member comprises a radially external fixing flange which is mounted against an external radial flange of the fixed portion of the turbomachine casing.

[0053] This embodiment ensures simplified installation of the sealing assembly.

[0054] In one embodiment, the distance between the radially inner end of the air straightening member and the outer surface of the rotor rotatably mounted around the axis A may be greater than or equal to 2.0 mm.

[0055] For example, the distance between the radially inner end of the blades of the sealing member and the outer surface of the rotor rotatably mounted around the axis A is greater to the predefined clearance of the sealing gasket.

[0056] This embodiment ensures that the thermo-mechanical expansions of the external surface of the rotor or its non-axisymmetric local displacements are insufficient for the external surface of the rotor to come into contact with the air straightening member.

[0057] In one embodiment, the predefined clearance of the seal may be between 0.5 mm and 1.0 mm.

[0058] This clearance is small enough to limit the efficiency losses of the turbomachine while nevertheless ensuring that the function of the cooling circuit is ensured. This clearance is also large enough to ensure that the external surface of the rotor does not come into contact with the seal in any of the flight regimes.

[0059] In one embodiment, the vanes of an air straightening member may have a mean line of between 15 mm and 25 mm.

[0060] The mean line is understood here, and in the rest of the present description, as the curvilinear length of the blade at mid-thickness in a projection perpendicular to the height of the blade, that is to say the extension of the latter in the radial direction.

[0061] In one embodiment, the thickness of the blade may be at any point less than or equal to 5.0 mm.

[0062] The thickness of the blade is understood here as its dimension perpendicular to its height.

[0063] Equivalently, the thickness of the blade is defined at a point on the blade as the shortest path allowing passage from the intrados to the extrados.

[0064] In one embodiment, the thickness of the blade may vary, preferably decrease, when traveling along the blade from upstream to downstream, i.e. from the leading edge to the trailing edge.

[0065] Such a reduction in the thickness of the blades makes it possible to increase the passage section for the air, and consequently to reduce its speed and therefore to increase its static pressure.

[0066] In one embodiment, all of the vanes of the air straightening member are identical.

[0067] In one embodiment, the ratio of the blade extent in the axial dimension to the blade mean line is between 0.6 and 0.9.

[0068] In one embodiment, the air straightening member comprises a plurality of fixed blades whose outlet angle is less than 10°, for example less than 5° or even between 0° and 2°.

[0069] The exit angle of a blade can be defined as the angle formed by the tangent to the mean line taken at the trailing edge and the axis A of the turbomachine.

[0070] Such an exit angle makes it possible to reduce or even cancel out the tangential component of the speed of the incident air reaching the seal.

[0071] In one embodiment, the gap between two circumferentially adjacent blades of the air straightening member may be less than 40°, for example between 9° and 36°.

[0072] The gap between two blades is measured as the angle formed between two circumferentially adjacent blades measured in a plane perpendicular to direction A.

[0073] The smaller the gap between two blades, the better the reduction in the tangential speed of the air passing through the air straightening member.

[0074] In one embodiment, the angle of attack of the blades of the air straightening member may be between 30° and 75°.

[0075] The angle of attack characterizes the angle formed between the tangent to the mean line of the blade taken at the leading edge and the direction of the axis A.

[0076] An angle of attack conforming to that proposed is optimized for the tangential velocity components expected for air leaving a high pressure compressor and thus makes it possible to maximize the conversion of the tangential component of the air flow velocity into an axial component, while minimizing pressure losses.

[0077] In one embodiment, the air straightening member may be secured to the same wall of the engine as the movable part of the seal.

[0078] 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.

[0079] Such a seal architecture differs radically from a labyrinth seal and ensures self-adaptive behavior of the seal.

[0080] The "circumferential distribution" of the seal sectors is intended to mean that each seal sector defines a portion of the circumference of the seal, and that all of the seal sectors together make it possible to obtain the complete seal.

[0081] It is understood that the predefined clearance is a “target” clearance, and that it is possible for the clearance to vary slightly around the predefined clearance value under conditions of use 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 entire seal will be returned to the predefined clearance by the spring behavior of the ring sectors. internal provided by the return organs or by the overpressure which then appears under the internal surface of the seal.

[0082] According to another of its aspects, the invention relates to an aeronautical turbomachine comprising at least one sealing assembly as described above.

[0083] In one embodiment, in such an aeronautical turbomachine, the at least one sealing assembly may be arranged on the cooling air conveying circuit, said cooling air conveying circuit comprising an inlet taking air downstream of the last disk of the high-pressure compressor and an inlet taking air radially under the combustion chamber in the form of an air mouth opening into an air intake housing in communication with the internal cooling circuit and chosen from: - the first sealing assembly downstream of the high-pressure compressor crossed by the air taken downstream of the last disc of the high-pressure compressor; - the upstream internal sealing assembly defining the inlet of said air intake housing and arranged radially below the air intake mouth; - the upstream external sealing assembly defining the outlet of said air intake housing and arranged radially under the high pressure distributor.

[0084] Indeed, such sealing assemblies are usually labyrinth seals and their replacement by a sealing assembly according to the invention makes it possible to obtain sealing assemblies whose service life is increased, without compromising their performance. Brief description of the drawings

[0085] [Fig.l] [Fig.l] schematically represents a double-flow turbojet.

[0086] [Fig.2] [Fig.2] schematically represents a cooling path in a turbomachine.

[0087] [Fig.3] [Fig.3] schematically represents a sealing assembly of a particular embodiment seen in a plane perpendicular to the circumferential direction.

[0088] [Fig.4] [Fig.4] schematically represents a sealing assembly of a particular embodiment in a different view from that of [Fig.3].

[0089] [Fig.5] [Fig.5] schematically represents a sealing assembly of a particular embodiment seen in a plane perpendicular to the radial direction. Description of the embodiments

[0090] 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.

[0091] [Fig. 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.

[0092] 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.

[0093] Thus, a so-called “upstream” element will be crossed before a so-called “downstream” element and a so-called “internal” element will be closer to axis A than an “external” element.

[0094] [Fig.2] represents a portion of the turbomachine visible in [Fig.l], and illustrates that the latter can be provided with sealing joints conforming to those described above.

[0095] In the embodiment shown, the turbomachine portion has three sealing assemblies: an upstream inner sealing assembly 62 (“FIS”), an upstream outer sealing assembly 63 (“FOS”) and a sealing assembly downstream of the high-pressure compressor 61 (“CDP”).

[0096] Such sealing assemblies are now described in connection with [Fig. 2] which is only one example of a configuration for an air cooling path in a turbomachine. A person skilled in the art will be able to identify an upstream external sealing assembly 63 (“FOS”), an upstream internal sealing assembly 62 (“FIS”) and a sealing assembly downstream of a high pressure compressor 61 (“CDP”) in other geometries of the cooling circuit.

[0097] In the embodiment shown in [Fig.2], air is taken downstream of the last compressor disc 401 as well as radially below the combustion chamber 5.

[0098] The air taken downstream of the last compressor disc 401 first passes through the sealing assembly 61, which is located radially below the inlet of the combustion chamber 5.

[0099] The sealing assembly comprises a straightening member 61a and a sealing gasket 61b, in accordance with what has been described above.

[0100] The seal 61b defines the quantity of air for the cooling circuit 401 taken downstream of the last disc of the high-pressure compressor 4 and also makes it possible to avoid the occurrence of pumping phenomena.

[0101] The air 83 taken radially below the combustion chamber 5 can for example be taken by an air opening 50, opening into a housing between the upstream external sealing assembly 63 and the upstream internal sealing assembly. 62.

[0102] In [Fig.2], these two sealing assemblies respectively delimit the inlet and the outlet of such a housing.

[0103] The sealing assembly 62 is crossed by the air taken downstream of the last compressor disc 401 wishing to enter this housing, regardless of whether it is then used for the cooling circuit 82 or whether it is intended for the purge circuit 81.

[0104] The sealing assembly 63 delimits the outlet of the air intake housing, and limits the flow of air reaching the purge circuit 81.

[0105] For example, the sealing assembly 62 may be located radially below the air intake mouth, while the sealing assembly 63 may be located radially below the first distributor of the high pressure turbine 701.

[0106] In [Fig.2], the purge circuit 81 opens between the high pressure distributor 701 and the first high pressure rotor blade 702.

[0107] In the embodiment shown, it will be noted that the surface facing the seals 62b and 63b is an external surface of a stage of the rotor of the high pressure turbine.

[0108] [Fig. 2] shows a turbomachine for which the three particular sealing assemblies 61, 62, 63 are as described above, but it does not go beyond the scope of the invention if only one of these sealing assemblies conforms to what is described above.

[0109] In the following, the sealing assembly 61 will be described, but it should be noted that what is described for this assembly can also be applied to the other sealing assemblies.

[0110] Figures 3 and 4 show in two different views a sealing assembly as described.

[0111] [Fig.3] shows a view in a plane perpendicular to the circumferential direction, while [Fig.4] presents a point from another perspective point.

[0112] In the present application, it is understood that the axial direction DA is understood as the direction of the main axis A of the turbomachine; the circumferential direction Dc is that forming a circle around the axial direction DA; and the radial direction DR defines a radius of the circle formed by the circumferential direction Dc and having the axial direction DA as its center.

[0113] These directions are shown in Figures 3 and 4.

[0114] [Fig. 3] shows the arrangement between them of the straightening member 200 and the sealing joint 300 of a sealing member 61, 62, 63.

[0115] The straightening member 200 comprises, in the embodiment shown, a plurality of blades 210 having a particular profile.

[0116] The profile of these blades, in the embodiment shown, will also be described below. after in connection with [Fig.5].

[0117] [Fig. 3] illustrates that the sealing assembly is comprised between a fixed part 54 of the casing of the turbomachine, for example integral with the combustion chamber 5, and a movable part 52.

[0118] For example, the moving part 52 may be a turbomachine rotor shroud.

[0119] Alternatively and as shown in [Fig.2], the moving part may be a surface 51 of a ferrule directly connected to a weight 58.

[0120] Alternatively, for example if the sealing assembly occupies a different position in the cooling circuit, the fixed part may be a part 55 integral with the combustion chamber 5 and arranged radially under the latter.

[0121] The seal 300 of FIGS. 3 and 4 is shown schematically. However, it can be seen that the latter defines an opening clearance j between the internal portion of the seal and the movable surface 52 opposite the latter.

[0122] In the embodiment shown, the assembly also comprises a distancing member 203. The latter is integral with the straightening member 200.

[0123] This embodiment ensures simplified assembly of the sealing assembly because it is sufficient to bring the seal 300 into contact with the distancing member 203 to ensure that the straightening member 200, integral with the distancing member 203, is then at the desired distance from the seal 300.

[0124] In the embodiment shown, the vanes of the straightening member have a leading edge 214 which has a particular orientation with respect to the incoming air flow.

[0125] Preferably, the angle of attack α, that is to say the orientation formed by the leading edge of the blade, is chosen as a function of the expected tangential speed of the incident air flow so that the straightening member works best to eliminate the tangential component.

[0126] In the embodiment of [Fig. 3], the clearance J can also be observed between the radially internal end of the blades 210 of the straightening member 200 and the surface of the rotor mounted to rotate around the axis A.

[0127] Preferably the clearance J is greater, for example at least twice greater than the clearance j of the sealing joint 300.

[0128] In one embodiment, the clearance j of the sealing gasket may be between 0.1 and 1.0 mm, or even between 0.5 mm and 1.0 mm.

[0129] In one embodiment, moreover shown in [Fig. 3], the fixed part 54 of the casing to which the sealing assembly is attached comprises a stop 502 against which the sealing gasket 300 rests. This embodiment ensures a simplified arrangement of the gasket, which can then be positioned precisely on the fixed part 54 of the casing.

[0130] In one embodiment, moreover shown in [Fig. 3], the straightening member 200 has a radially external fixing flange 202, which is arranged in abutment against a suitable part of the fixed part 54 of the casing, for example a radially external flange 501.

[0131] This embodiment makes it possible to ensure easy positioning of the air straightening member 200, insofar as its positioning is then constrained by the radially external fixing flange 202.

[0132] In one embodiment, which is that shown in [Fig. 3], the seal 300 can be arranged axially between a distancing member 203 of an air straightening member 200 described above, and a radial recess 502 formed in the fixed part 54 of the casing.

[0133] In one embodiment, which is that shown in [Fig. 3], the sealing assembly may be arranged radially between a fixed portion of a turbomachine casing 54 and an external surface 52 of the rotor rotatably mounted around the axis A. Furthermore, the air straightening member 200 may comprise a radially external fixing flange 202 which is arranged against an external radial flange 501 of the fixed portion of the turbomachine casing

[0134] This embodiment ensures that the desired distances for the proper functioning of the sealing assembly are respected by a simplified mechanical assembly, particularly with regard to the positioning of the different elements.

[0135] Indeed, the sealing assembly can then be formed by placing the sealing gasket 300 in abutment against the radial recess 502, then by placing the air straightening member 200 so that the distancing member 203 is in abutment against the sealing gasket 300.

[0136] Furthermore, the radially external fixing flange 202 of the air straightening member 200 is also in abutment against the external radial flange 501 of the fixed part 54 of the casing, which ensures redundancy of the position control of the air straightening member 200.

[0137] In such an embodiment, no measurement of the positioning of an element of the assembly must be carried out so that the elements 200, 300 of the sealing assembly are arranged in a functional manner.

[0138] Furthermore, it is specified that [Fig.4] is a schematic section in which the straightening member is not shown in its entirety.

[0139] In one embodiment, the straightening member comprises a plurality of straightening member sectors, and possibly suitable connecting means between two successive straightening members, so that all of the straightening member sectors make it possible to form a circumferential straightening member.

[0140] This embodiment makes it possible to simplify the assembly and the proper maintenance of the straightening member by breaking it down into a plurality of sectors, each of smaller dimensions.

[0141] [Fig.5] illustrates the different dimensions of the blades forming the straightening member in one embodiment.

[0142] In one embodiment, the vanes of an air straightening member may have a mean line Ç of between 15 mm and 25 mm.

[0143] In one embodiment, the thickness e of the blade may be at any point less than or equal to 5.0 mm.

[0144] The thickness of the blade is understood here as its dimension perpendicular to its height.

[0145] Equivalently, the thickness of the blade is defined at a point of the blade 210 as the shortest path allowing passage from the intrados 210a to the extrados 210b.

[0146] In one embodiment, which is not the one shown, the blades 210 of the air straightening member may have a thickness which varies between the leading edge and the trailing edge.

[0147] For example, the thickness e of the blade can decrease strictly between the leading edge and the trailing edge of the blade.

[0148] In one embodiment, the thickness at the leading edge ei and the thickness at the trailing edge e2 may be such that the thickness at the trailing edge e2 is between 50% and 100% of the value of the thickness at the leading edge ep

[0149] Such a variation in the thickness of the blade e makes it possible to give a profile which ensures an increase in the static pressure of the air in the air straightening member 200.

[0150] In one embodiment, all of the vanes 210 of the air straightening member 200 are identical.

[0151] In one embodiment, the ratio between the extent L of the blades 210 in the axial dimension and the mean line Ç of the blades is between 0.6 and 0.9.

[0152] In one embodiment, the gap between two blades 210 of the air straightening member 200 may be between 9° and 36°.

[0153] An angle corresponding to this gap, marked e, is described in [Fig.4] which allows a better understanding. The gap e is measured between two blades 210 circumferentially adjacent to each other.

[0154] In one embodiment, the angle of attack α of the blades 210 of the air straightening member 200 may be between 30° and 75°.

[0155] The orientation, profile and dimensions of the blades 210 of the air straightening member 200 ensure suppression of the tangential velocity component of the incident air.

[0156] Although equal to 0° in the embodiment shown, the exit angle is marked there on [Fig.5].

[0157] As described above, the exit angle y is formed between the tangent to the mean line Ç and the axial direction DA.

[0158] In [Fig.5], the exit angle y is equal to 0° which is optimal for completely eliminating the tangential component of the speed of the incident air flow.

[0159] These characteristics thus make it possible to obtain excellent control of the sealing joint 300, even with pressures upstream and downstream of the joint that are not very different.

[0160] The gain in terms of pressure difference required to set the seal in motion compared to seals taken in isolation, i.e. without the air straightening member, is at least 20%.

[0161] This ensures safer behavior of the seal, and further prevents the seal from coming into contact with the moving part opposite which it is arranged.

[0162] These safety performances largely make it possible to compensate for the loss caused by the increase in the equilibrium clearance j of the sealing assembly.

[0163] The seal 300, provided that it has self-adaptive behavior as described above, is not particularly limiting in obtaining the technical effect of the invention.

[0164] Indeed, it is the elimination of the tangential component of the incident air which makes it easier for the seal 300 to return to its equilibrium position.

[0165] More specifically, the pressure difference between the pressure upstream of the seal 300 and that downstream of the seal 300 no longer needs to be as large as for seals of the prior art in order for the seal to start moving.

[0166] However, a seal 300 particularly suitable for the invention is described below.

[0167] In one embodiment, the seal may be a sealing gasket configured to provide a predefined clearance between said seal and an external surface of a rotor rotatably mounted around the axis A arranged opposite the seal, the axis A defining an axial direction, the seal extending circumferentially around the axis A and comprising 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 sealing gasket 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 an unhollowed portion of the inner surface.

[0168] Such an architecture of the seal 300 differs radically from a labyrinth seal.

[0169] However, the internal surface of the internal ring sector does ensure aerodynamic sealing by ensuring a predefined clearance with the facing surface.

[0170] 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 sealing joint being to allow a defined quantity of air to pass through.

[0171] The "circumferential distribution" of the seal sectors is intended to mean that each seal sector defines a portion of the circumference of the seal, and that all of the seal sectors together make it possible to obtain the complete seal.

[0172] In one embodiment, the circumferential distribution is regular, and each seal sector then represents an equal portion of the circumference of the seal.

[0173]

[0174] If the clearance of the seal becomes smaller than the predefined clearance, the pressure radially under the inner surface of the inner ring sectors increases and the inner ring sector then moves so as to increase the clearance, whereas if the clearance of the seal 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.

[0175] This aerodynamic balance makes it possible to prevent the internal surface of the internal ring sector from coming into contact with the facing surface at any time and the seal differs in this from labyrinth seals. This avoids the problem of wear which can be encountered with conventional labyrinth seals.

[0176] Generally speaking, 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.

[0177] The patterns hollowed out from the internal surface of the internal ring sector also make it possible to modify the behavior of the seal, in particular by further increasing the pressure exerted by the air on the internal surface of the internal ring sector when the latter approaches the facing surface.

[0178] 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.

[0179] 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 direction radial of the ring sector, i.e. the direction perpendicular to the axis A, and from the internal surface of the internal ring sector.

[0180] 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 width of the pattern.

[0181] The second dimension of the pattern, in the plane of the internal surface of the internal ring sector will be arbitrarily called length.

[0182] It does not go beyond the scope of the invention if the width is greater than the length but, for the sake of simplicity, we will only describe below cases in which a pattern is longer than it is wide.

[0183] 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.

[0184] Thus, and as described, the length of a pattern is in a direction oblique to the axial direction.

[0185] 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.

[0186] A compatible seal of an air straightening member as described is now described.

[0187] 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.

[0188] Such a seal architecture differs radically from a labyrinth seal.

[0189] However, the internal surface of the internal ring sector does ensure aerodynamic sealing by ensuring a predefined clearance with the facing surface.

[0190] 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.

[0191] 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 all of the joint sectors allows to obtain the complete joint.

[0192] In one embodiment, the circumferential distribution is regular, and each seal sector then represents an equal portion of the circumference of the seal.

[0193] It is understood that the predefined clearance is a “target” clearance, and that it is possible for the clearance to vary slightly around the predefined clearance value under conditions of use of the seal. When the seal is in its equilibrium position, the predefined clearance ensures that the airflow passing through the seal is the desired airflow. However, if the clearance increases or decreases, the seal will be returned to the predefined clearance with respect to a spring behavior of the internal ring sectors ensured in particular by the return members.

[0194] 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.

[0195] This aerodynamic balance makes it possible to prevent the internal surface of the internal ring sector from coming into contact with the facing surface at any time and the seal differs in this from labyrinth seals. This avoids the problem of wear which can be encountered with conventional labyrinth seals.

[0196] Generally speaking, 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.

[0197] 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.

[0198] The patterns hollowed out from the internal surface of the internal ring sector make it possible to modify the behavior of the seal, in particular by further increasing the pressure exerted by the air on the internal surface of the internal ring sector when the latter approaches the facing surface.

[0199] 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.

[0200] 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.

[0201] 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 width of the pattern.

[0202] The second dimension of the pattern, in the plane of the internal surface of the internal ring sector will be arbitrarily called length.

[0203] It does not go beyond the scope of the invention if the width is greater than the length but, for the sake of simplicity, we will only describe below cases in which a pattern is longer than it is wide.

[0204] 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.

[0205] Thus, and as described, the length of a pattern is in a direction oblique to the axial direction.

[0206] 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.

[0207] 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°.

[0208] The angle of inclination of the patterns makes it possible on the one hand to inscribe more patterns or patterns of greater length on the surface of an internal ring sector of given dimensions.

[0209] In one embodiment, the angle of inclination of the patterns is between 30° and 60°, or even between 30° and 45°.

[0210] Indeed, this also ensures that the air flow, which possibly has a tangential speed due to the rotation of several elements with which it is possibly in contact, enters the pattern without seeing too great a discontinuity.

[0211] Preferably, the angle of inclination is oriented in the same direction as the tangential speed of the air flow, or in the direction of rotation of the facing surface relative to the internal ring sector.

[0212] The surface facing the seal is a surface of a rotor mounted to rotate about the axis A, for example the rotor of a high-pressure turbine of an aeronautical turbomachine. In one embodiment, the patterns may be inclined in the same direction as the direction of rotation of the rotor.

[0213] 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. sealing.

[0214] The depth of a pattern is understood as the distance between the inner surface of the unhollowed 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.

[0215] 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.

[0216] 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.

[0217] 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.

[0218] 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.

[0219] Furthermore, they ensure that the inner surface of the inner ring sector does not come into contact with the facing surface in the intended or even accidental operating modes.

[0220] 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.

[0221] It is understood that the first row of patterns is the first row encountered by the air flow passing the seal. In the case where there is only one row of patterns, the first row is the row of patterns.

[0222] If there are two rows of patterns, the first row of patterns may also be characterized as the “upstream row”, and the second row of patterns as the “downstream row”.

[0223] In one embodiment, each pattern of the first row of patterns has a planar downstream pattern zone of constant and non-zero depth and an upstream pattern zone in which the depth varies in a decreasing manner while remaining greater than the constant depth of the downstream pattern zone.

[0224] The downstream zone performs the general role of the pattern which is to increase the pressure on the internal surface of the internal ring sector when the clearance is lower than the predefined clearance.

[0225] In one embodiment, the upstream area of ​​each pattern of the first row of patterns can have a rounded, i.e. convex, shape.

[0226] In this embodiment, the upstream zone ensures a low pressure loss at the inlet of the seal. This thus improves the efficiency of the seal as a whole.

[0227] 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 the air traveling through the first pattern encounters a wall directed in the radial direction at the end of the first pattern.

[0228] 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.

[0229] In one embodiment, the depth of the downstream portion of the pattern of the first row may be between 1.5 times and 2.5 times the predefined clearance for the seal.

[0230] The inventors have in fact noted that these depth values ​​ensure excellent distribution of pressures in the seal, which improves the effectiveness of the seal.

[0231] In an embodiment where the internal surface of each internal sector comprises at least two rows of patterns, each pattern of the second row of patterns has a planar downstream pattern zone of constant and non-zero depth and an upstream pattern zone in which the depth of the pattern varies increasingly from the internal surface of the internal ring sector while remaining less than the constant depth of the downstream pattern zone.

[0232] This embodiment makes it possible to ensure 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.

[0233] In one embodiment, each inner surface of the inner ring sectors comprises 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.

[0234] For example, the patterns of the second row are offset in the circumferential direction relative to the patterns of the first row by a distance of 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.

[0235] This embodiment makes it possible to ensure that the air flow passing through the seal and having a tangential speed encounters patterns of the two rows of patterns during of its passage through the seal.

[0236] 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.

[0237] 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.

[0238] 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.

[0239] In one embodiment, the inner surface of the inner ring sector may also comprise after the last pattern a non-hollowed surface of the inner surface of the inner ring sector then a portion of increase in thickness between the non-hollowed surface and the downstream end of the inner ring sector.

[0240] Such a profile makes it possible to reduce the pressure heterogeneity at the outlet of the seal, which reduces the risk of vibratory instability of the seal due to the wake of the air passing through it.

[0241] 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.

[0242] 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°.

[0243] This inclination of the circumferential ends of the inner ring sectors of the joint sectors makes it possible to ensure a displacement of the inner ring sectors of the joint sectors relative to each other.

[0244] 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.

[0245] In one embodiment, the seal comprises between 8 and 12 seal sectors.

[0246] For reasons of mechanical strength, space requirement and to ensure the flatness of the surface of the sealing joints, it would be preferable to have as many sectors as possible. On the other hand, for aerodynamic reasons, it is necessary to avoid leaks, and therefore to minimize the number of seal sectors. The inventors have found that such a number of seal sectors is an optimal compromise between these two opposing effects.

[0247] In one embodiment, the outer ring sectors of a seal can be a single piece, for example a ferrule. In other words, there is no physical separation between two circumferentially successive external ring sectors.

[0248] 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.

[0249] 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.

[0250] 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.

[0251] 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, a tile.

[0252] The embodiments of the seal described below are compatible with the embodiments of the air straightening member, so that the particular technical effects of certain embodiments can be obtained together if desired.

Claims

Claims

1. Sealing assembly (61, 62, 63) for a turbomachine (1) comprising a seal (300, 61b, 62b, 63b) configured to ensure a predefined clearance (j) between said seal and an external surface (51, 52) of a rotor rotatably mounted about an axis A, the axis A defining an axial direction (DA), the seal extending circumferentially about the axis A and the external surface (51, 52) being arranged opposite the seal, the sealing assembly being characterized in that it further comprises an air straightening member (200) comprising at least one row of blades which extend radially, the air straightening member being located upstream of the seal, the air straightening member (200) being configured to straighten air intended to pass through the seal.

2. A sealing assembly (61, 62, 63) according to claim 1, wherein the air straightening member has fixed vanes (210), the fixed vanes having an outlet angle (y) of less than 10°.

3. Sealing assembly (61, 62, 63) according to claim 2, wherein the vanes of the air straightening member (200) have a mean line (Ç) of between 15 mm and 25 mm.

4. Sealing assembly (61, 62, 63) according to claim 2 or 3, wherein the gap (e) between two circumferentially adjacent blades (210) is less than 40°.

5. Sealing assembly (61, 62, 63) according to any one of claims 2 to 4, wherein the angle of attack (a) of the vanes (210) of the air straightening member (200) is between 30° and 75°.

6. A sealing assembly (61, 62, 63) according to any one of claims 1 to 5, wherein the distance between the inlet of the air straightening member (200) and the upstream edge of the seal is between 10 mm and 20 mm.

7. A sealing assembly (61, 62, 63) according to any one of claims 1 to 6, wherein the distance between the outlet of the air straightening member (200) and the upstream edge of the seal is between 2.0 mm and 5.0 mm.

8. A sealing assembly (61, 62, 63) according to any one of claims 1 to 7, wherein the air straightening member (200) comprises a distancing member (203) integral with the re- air dressing.

9. Sealing assembly (61, 62, 63) according to claim 8, wherein the sealing assembly is arranged radially between a fixed part of a turbomachine casing (54) and the external surface (52) of the rotor rotatably mounted about the axis A, and wherein the seal is arranged axially between a radial recess (502) of the fixed part of the turbomachine casing and the distancing member (203) of the air straightening member (200).

10. A sealing assembly (61, 62, 63) according to any one of claims 1 to 9, wherein the sealing assembly is arranged radially between a fixed portion of a turbomachine casing (54) and an external surface (51, 52) of the rotor rotatably mounted about the axis A and wherein the air straightening member (200) comprises a radially external fixing flange (202) which is mounted against an external radial flange (501) of the fixed portion of the turbomachine casing.

11. Aeronautical turbomachine comprising at least one sealing assembly (61, 62, 63) according to one of claims 1 to 10.

12. Aeronautical turbomachine according to claim 11, in which the at least one sealing assembly (61, 62, 63) according to any one of claims 1 to 10 is arranged on a cooling air routing circuit, said cooling air routing circuit comprising an air sampling inlet (401) downstream of the last disc of a high pressure compressor (4) and an air sampling inlet (83) radially under a combustion chamber (5) which takes the form of an air mouth opening into an air intake housing in communication with the cooling air routing circuit and the sealing assembly being chosen from: - an upstream sealing assembly (61) located downstream of the high pressure compressor crossed by the air (401) sampled downstream of the last disc of the high pressure compressor;- a downstream internal sealing assembly (62) defining the inlet of said air intake housing and arranged radially under the air intake mouth; - a downstream external sealing assembly (63) defining the outlet of said air intake housing and arranged radially under a high pressure distributor (701).;

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