FR3079013A1 - ANNULAR SEALING DEVICE - Google Patents

Abstract

The invention relates to an annular sealing device extending around a longitudinal axis and intended to be mounted around a shaft of a turbomachine, the device comprising an annular body (46) inside which is mounted a ring formed of a plurality of carbon segments held together by first resilient means (62) surrounding said segments, second resilient means (64) being interposed longitudinally between a radial annular wall (57) of the annular body (42) and the carbon segments. According to the invention, the first elastic means (62) comprise an elastically-deformable annular annular ring surrounding said segments and / or in that the second elastic means comprise an elastic washer (64) coaxial with the longitudinal axis and elastically deformable in the direction longitudinal.

Description

ANNULAR SEALING DEVICE

FIELD [001] The present invention relates to an annular sealing device intended for example to be used in a turbomachine and more particularly for sealing between an air enclosure and an oil enclosure.

BACKGROUND [002] In known manner, a turbomachine rolling bearing supporting a rotating shaft inside a fixed casing comprises a bearing disposed in an enclosure where its lubrication is ensured by oil. However, any migration of oil to the outside of this enclosure must be avoided, which is ensured by pressurizing this enclosure with air taken from the vein.

[003] Thus, to minimize the air flow at the terminals of the oil chamber, segmented radial seals are installed. These radial seals comprise a plurality of carbon segments arranged circumferentially end to end and mounted inside an annular body. These carbon segments are held by a helical spring surrounding the segments. The segments are also held in abutment on a radial annular wall of the annular body by a plurality of axial helical springs regularly distributed circumferentially.

These seals are very efficient because of their flexible and elastic design and retain their effectiveness in all operating ranges (idle, transient, cruise, ...). However, to maintain its performance, this type of seal must evolve in an environment suitable for temperature and avoid an environment that is too hot which would be detrimental to the maintenance of its mechanical properties over time.

During transient or idling phases, it may happen that too small a difference in air pressure leads to the oil from the enclosure housing the bearing being introduced into the structure of the seal, c 'is to say through the constituent elements of the seal, and that it cokes due to the high surrounding temperatures. In this case, the carbon segments no longer fulfill their sealing function and the seal leaks. As a result, oil consumption increases and oil can diffuse into the air chamber, leading to pollution of the engine with coked oil.

Note that there are two possibilities to avoid heating in the segmented radial seal. Either we increase the ventilation flow around the joint which leads to an increase in the air intake and is therefore not desirable, or we take a colder air flow but it is difficult to guarantee that the pressure is sufficient to have sufficient flow at the joint.

The invention proposes to modify the structure of the seal so that it is capable of fulfilling its sealing functions while avoiding modifying the air intake means integrated in the turbomachine.

SUMMARY OF THE INVENTION The present invention firstly relates to an annular sealing device extending around a longitudinal axis and intended to be mounted around a shaft of a turbomachine, the device comprising a annular body inside which is mounted a ring formed of a plurality of carbon segments held together by first elastic means surrounding said segments, second elastic means being inserted longitudinally between a radial annular wall of the annular body and the carbon segments, characterized in that the first elastic means comprise an elastically deformable split annular ring surrounding said segments and / or in that the second elastic means comprise an elastic washer coaxial with the longitudinal axis and elastically deformable in the longitudinal direction.

According to the invention, the elastic elements of the prior art are replaced by specific elastic elements. The elastically deformable split annular ring as well as the elastic washer prove to be less sensitive in operation to the introduction of oil into the structure of the sealing device or joint. Therefore, the life of the seal can be improved compared to the prior art. It is therefore possible to maintain the sealing performance of a segmented radial seal evolving in a warmer environment, without degrading the quality of the oil, without having to modify the air flow around the seal.

It will be noted that the advantage of the sealing device is to have elastic elements, that is to say the rod and the washer, which now only comprise a turn, that is to say say a single winding. This avoids the introduction and stagnation of oil between the turns which coke and forms a shell preventing the normal functioning of the seal. The absence of coke formation in operation also results from the replacement of the axial springs of the prior art by an elastic washer.

To achieve axial elasticity, that is to say in the longitudinal direction, the elastic washer is preferably a wavy washer comprising successive circumferential and axial undulations. The washer may also include a slot delimited between its free circumferential ends.

Advantageously, the washer comprises at least 3N corrugations regularly distributed around the longitudinal axis where N represents the number of segments. In this embodiment, there are thus three undulations per carbon segment so as to have good longitudinal support on each segment. Preferably, the washer comprises 3N + 1 corrugations, which makes it possible to guarantee that when a bump is arranged at the junction between two consecutive segments, the other bumps provide longitudinal support on the radial annular wall of the annular body and the carbon segments.

As indicated above, a corrugation includes a bump and a hollow when the washer is seen from one side. Obviously, seen from the other side of the washer, a hollow corresponds to a bump and a bump corresponds to a hollow. In practice, therefore, a ripple is needed, that is to say a bump and a hollow, in order to thus provide support on the radial annular wall of the annular body and on a carbon segment.

The invention also relates to a turbomachine section comprising a rotating shaft guided in rotation in a rolling bearing and carrying an annular sealing device as described above as well as a labyrinth seal interposed axially between said annular device d and the bearing housing.

The invention will be better understood and other details, characteristics and advantages of the invention will appear on reading the following description given by way of non-limiting example with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a schematic sectional view of a turbomachine comprising a sealing device according to the invention;

Figure 2 is a schematic view on a larger scale of the area delimited by dotted lines in Figure 1;

Figure 3 is a schematic view on a larger scale of the area delimited by dotted lines in Figure 2 and more specifically showing a sealing device according to the prior art mounted around a shaft;

Figure 4 is a schematic perspective view of a sealing device according to the prior art;

Figures 5 and 6 are schematic perspective views of a sealing device according to the invention;

FIGS. 7 is a schematic illustration of an embodiment of a first elastic element intended to be integrated into a sealing device according to the invention;

FIGS. 8A and 8B are schematic illustrations of two embodiments of a second elastic element intended to be integrated into a sealing device according to the invention.

DETAILED DESCRIPTION [016] Reference is first made to FIG. 1 which represents a half-view in section of a turbomachine 10 of longitudinal axis A comprising from upstream to downstream, that is to say in the direction of air flow through the turbomachine 10, a blower 12, a low pressure compressor 14, a high pressure compressor 16, a combustion chamber 18, a high pressure turbine 20 and a low pressure turbine 22.

In known manner, the fan 12 and the rotor of the low pressure compressor 14 are rotated by the rotor of the low pressure turbine 22, the high pressure turbine rotor 20 driving the rotor of the high pressure compressor 16 in rotation.

More particularly, the rotor of the low-pressure turbine 22 comprises a central shaft 24 which is guided in rotation in at least one bearing 26 for rolling, here only one (FIG. 2). The rolling bearing 26 is housed in an annular enclosure 28, the axial or longitudinal ends of which comprise a twist 30 similar to a thread whose orientation makes it possible to discharge the oil towards the interior of the annular enclosure 28 and a seal at labyrinth 32 protected by a spin 33 similar to a thread, the orientation of which makes it possible to discharge the oil towards the interior of the annular enclosure 28. Air flows (arrows A) are provided and oriented from the outside of the oil enclosure 28 towards the tendrils 30, 33 to prevent an oil leak towards the outside of the annular enclosure 28.

To further improve sealing, an annular sealing device 34 or segmented radial seal is used which is arranged at one end of the oil enclosure 28 and outside of it (FIG. 3) . The sealing device 34 is housed in an annular recess of an annular stator arm 36, the end of which carries the twist 30. The segmented radial seal 34 is locked axially downstream by an annular shoulder 38 of the stator arm 36 and by a stop ring 40.

Referring now to Figure 4 which shows a segmented radial seal 34 according to the prior art and which comprises an annular body 42 comprising an outer ring 44 and an annular flange 46 assembled to each other by pins or pins engaged in radial holes in the crown 44 and the annular flange 46.

[021] The annular sealing device 34 also includes a plurality of segments 50 made of carbon which are arranged successively and circumferentially end to end to form a ring. Each segment 50 comprises two radial tabs 52 at its circumferential ends, a tab 52 of a segment 50 being applied circumferentially on a tab 52 of a circumferentially adjacent segment 50. As is well represented in FIG. 4 but also in the figure 5 in relation to the invention which will be described below, each tab 52 comprises a mounting groove for first elastic annular means 53, which element surrounds all the carbon segments 50 in order to hold them in the annular body 42.

It is observed that the ring 44 comprises an annular rim 54 radial extending by the annular flange 46 and also radial fingers 56 regularly spaced circumferentially and which are opposite to the annular radial rim. These fingers 56 provide, with the radial annular rim 54 of the crown 44 and the annular flange 46, axial locking of the segments 50. It is noted that the annular flange 46 and the radial annular flange 54 form an annular wall 57 of the annular body 42.

Referring to Figure 4, the first elastic annular means 53 comprise a helical annular spring. The sealing device 34 also comprises a plurality of second elastic means 58 which are helical springs arranged axially. These springs 58 are mounted in axial housings of the segments 50 and are elastically prestressed between the radial wall 57 of the annular body 42 and the bottom of the housings of the segments 50. As indicated at the beginning of this document, the use of these two elastic elements 53, 58 does not guarantee optimal operation of the sealing device 34 due to the introduction of oil therein and the coking thereof which strongly impacts the elastic elements 53, 58.

[024] Figure 5 shows an annular sealing device 60 according to the invention which comprises segments 50 of carbon material, a ring 44 with a radial annular flange 54 and radial fingers 56, an annular flange 46 and pins. The parts indicated above are arranged in the same way as has been described with reference to FIG. 4.

According to the invention, the first elastic means 62 are here formed by a split annular ring elastically deformable in the radial direction, this ring thus having a single turn, that is to say a single winding. In a practical embodiment of the invention, the rod will have a constant circular section over its entire angular extent. In another variant, it may also have a non-constant section over the entire angular extent of the rod. The rod can also have a section different from that of a circle, for example elliptical. The second elastic means are here an elastic washer having an axial elasticity, that is to say a washer which is shaped so as to be able to deform elastically along its axis, that is to say the longitudinal axis.

[026] The elastic annular ring is arranged radially between the segments 50 and the crown 44, that is to say radially outside the segments 50 and radially inside the crown 44. The elastic annular ring 62a has a slot 63 and is made of steel having for example the reference Z12CN18 (FIG. 7A).

[027] The elastic washer 64 is mounted axially between the segments 50 and the radial annular wall 57 formed by the annular rim 54 and the flange 46. The washer 64 preferably comprises circumferential and axial corrugations 65 which make it possible to have elasticity of the washer along the axis B thereof which is in coaxial operation with the longitudinal axis A. The corrugations are substantially curved and regular over the entire circumference of the washer. In a first embodiment shown in Figure 8A, the washer 64a has a slot 66. In a second embodiment shown in Figure 8B, the washer 64b has no slot and thus has a closed contour.

[028] Preferably, the elastic washer comprises at least 3N undulations regularly distributed around the longitudinal axis where N represents the number of segments, preferably at least 3N + 1 undulations. A corrugation 65 includes a bump 68 and a recess 70 when the washer 64a is viewed from a given side. Obviously, seen from the other side of the washer 64a, a hollow corresponds to a bump and a bump corresponds to a hollow. In practice, therefore, a ripple is needed, that is to say a bump 68 and a recess 70 in order to thus produce a support on the radial annular wall 57 of the annular body 42 and on a carbon segment 50.

The choice of 3N + 1 corrugations regularly distributed around the axis of the washer 64a, is guided by the desire to guarantee that when a bump 68 is arranged at the junction between two consecutive segments 50, the other bumps 68 provide axial support on the radial annular wall 57 of the annular body 42 and the carbon segments 50. Thus, the washer provides three axial supports per carbon segment 50.

[030] Similarly to what has been described with reference to FIG. 8A, the washer in FIG. 8B also includes corrugations formed by bumps 68 and recesses 70.

Claims (5)

1. Annular sealing device extending around a longitudinal axis and intended to be mounted around a shaft (24) of a turbomachine, the device comprising an annular body (46) inside which is mounted a ring formed of a plurality of carbon segments (50) held together by first elastic means (62) surrounding said segments, second elastic means (64) being inserted longitudinally between a radial annular wall (57) of the annular body (46 ) and the carbon segments (50), characterized in that the first elastic means (62) comprise an elastically deformable split annular ring surrounding said segments (50) and / or in that the second elastic means comprise an elastic washer (64) coaxial with the longitudinal axis and elastically deformable in the longitudinal direction. 2. Device according to claim 1, wherein the washer (64) is a wavy washer each comprising successive circumferential and axial corrugations, each corrugation comprising a bump and hollow. 3. Device according to claim 2, wherein the washer (64) comprises at least 3N corrugations regularly distributed around the longitudinal axis where N represents the number of segments, preferably at least 3N + 1 corrugations. 4. Device according to claim 2 or 3, wherein at least one washer (64) comprises a slot defined between the free circumferential ends of the washer. 5. Turbomachine section comprising a rotating shaft guided in rotation in a bearing (26) of bearings and carrying an annular sealing device according to one of claims 1 to 4 as well as a labyrinth seal (30) interposed axially between said annular sealing device (60) and the rolling bearing (26).