Hydraulic compensation device

Abstract

The invention relates to a hydraulic compensation device (2) arranged in a cavity (32) of a bladed propeller rotor (100) in a turbomachine for the circulation of a lubricant, the rotor having an axis (X), said compensation device comprising an annular body (21) having a groove (210) forming a track, and a piston (22) arranged in the annular body (21), the piston (22) is slidable in the track at least between an initial position and a retracted position.

Description

Technical Field

[0001] The present invention relates to the field of turbines, and more particularly to the field of non-streamlined turbines.

[0002] More specifically, the present invention relates to a hydraulic compensation device intended to be arranged in a cavity for lubricant of a bladed propeller rotor of a turbine having an axis.

[0003] The present invention relates to all types of aircraft turbines, in particular turbojets and turboprop engines having a bladed propeller. Background Art

[0004] For each blade, a bladed propeller rotor of a turbine generally includes a blade trunnion capable of rotating about an axis perpendicular to the axis of the turbine, and a hub arranged around the blade trunnion.

[0005] The propeller blade trunnions are guided in rotation by bearings which need to be constantly lubricated at the contact surfaces between the rolling elements and the raceways so that the operation of the bearings is not impaired. Thus, a lubricant is generally implemented in a cavity defined by the hub and the blade trunnion and leading to the bearings. In order to constantly lubricate the bearings so as to ensure a thin layer of lubricant between the rolling elements and the bearing rings, the cavity must be almost completely or completely filled with this lubricant so that the bearings are always lubricated during all rotations of the blades.

[0006] However, during the flight phase, especially during takeoff, the temperature in the cavity can reach 100 degrees, thus causing an increase in pressure related to the expansion of the lubricant (such as oil), and this pressure increase is approximately 11.25 bar per degree Celsius. If the expansion of the lubricant is not inhibited during the flight phase, the internal pressure in the cavity can reach a pressure of several hundred bar, which can cause damage to the seals and to the surrounding components (such as the hub of the propeller).

[0007] Therefore, in order to limit the increase in the internal pressure of the system, it is known to implement a hydraulic compensation device, in particular in the form of an expansion tank. Various expansion tank systems are generally used, where the expansion tank implements a deformable elastomeric membrane, or the expansion tank implements a piston, as described for example in document FR2498278.

[0008] In the case of an elastomeric membrane, the disadvantages are that it is particularly necessary to have an elastomer compatible with the operating temperature and the nature of the lubricant, and it is necessary to ensure a certain static seal at the location of the membrane. In addition, this solution adds additional elements which can have an impact on the ease of implementation and the ability to integrate into aerospace applications, but can also have an impact on the quality, especially at the propeller rotor.

[0009] Another problem with the current solution is that the current hydraulic compensation device is implemented in the form of an external expansion tank, so additional components need to be added. In addition, it is relatively difficult to integrate such an external solution into an aviation application (especially at the propeller rotor, where the performance of the propeller rotor also depends on the balance during the correction of unbalance) without disturbing the correct operation of such a complex aviation system.

[0010] Therefore, a solution is needed that enables the lubrication of the propeller rotor to be ensured while compensating for the increase in pressure due to the increase in temperature during the operation of the turbine. Summary of the Invention

[0011] The object of the present invention is to overcome at least in part the above-mentioned disadvantages related to the technology of the prior art.

[0012] To this end, the present invention relates to a hydraulic compensation device intended to be arranged in a cavity of a bladed propeller rotor of a turbine having an axis X, the cavity being for the circulation of a lubricant. According to the invention, the device comprises an annular body and a piston, the annular body having a groove forming a track in which the piston is able to slide at least between an initial position and a retracted position.

[0013] Therefore, the present invention proposes a novel and innovative solution that can at least partly solve some of the disadvantages of the prior art.

[0014] In particular, the present invention can ensure the lubrication of the propeller rotor while compensating for the increase in pressure due to the increase in temperature during the operation of the turbine. In fact, the space occupied by the hydraulic compensation device enables a smaller amount of lubricant to be placed while continuing to fill the cavity completely with oil, thereby limiting the expansion of the lubricant while ensuring a lasting contact between the lubricant and the bearings.

[0015] In addition, the integration of such a solution is relatively simple without disrupting the normal operation of such a complex aviation system.

[0016] According to a particular aspect of at least one embodiment of the invention, the hydraulic compensation device comprises at least one return spring arranged between the annular body and the piston and configured to exert a return force on the piston to return the piston towards the initial position.

[0017] Preferably, a return force can be exerted on the piston during the engine stop phase to return the piston towards the initial position.

[0018] According to a particular aspect of at least one embodiment of the invention, the hydraulic compensation device further comprises a bearing washer arranged between the at least one return spring and the piston.

[0019] Thus, such a bearing washer enables the presence of a bearing between at least one bearing spring and the piston while limiting the deformation of the piston, particularly in the area of contact with one or more return springs.

[0020] According to a particular aspect of at least one embodiment of the invention, the bearing washer is at least partially made of metal or metal alloy, or preferably of composite plastic.

[0021] According to a particular aspect of at least one embodiment of the invention, the annular body is at least partially made of metal, metal alloy or plastic.

[0022] According to a particular aspect of at least one embodiment of the invention, the piston is at least partially made of virgin PTFE, filled PTFE or elastomer.

[0023] It should be noted that the piston may also include a metal actuating spring.

[0024] An advantage of this material is that the piston itself can also be used as a sealing joint.

[0025] The invention also relates to a bladed propeller rotor of a turbine having an axis X, the propeller rotor including blade trunnions capable of rotational movement about an axis Y perpendicular to the axis X of the turbine, and a hub arranged around the trunnions, the hub and the blade trunnions defining a cavity for the circulation of a lubricant. According to the invention, the rotor further includes a hydraulic compensation device according to one of the foregoing embodiments, the hydraulic compensation device being mounted in the cavity.

[0026] According to a particular aspect of at least one embodiment of the invention, the piston is capable of sliding along the axis Y in the annular body.

[0027] According to a particular aspect of at least one embodiment of the invention, the hydraulic compensation device is fastened to the propeller rotor via the annular body, the annular body being fastened against the inner wall of the hub.

[0028] The invention also relates to a bladed propeller including a rotor according to one of the foregoing embodiments.

[0029] The invention also relates to an aircraft turbine including at least one bladed propeller.

[0030] According to a particular aspect of at least one embodiment, the turbine is a turbojet engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention and its various advantages will be more readily understood from the following description of illustrative and non - limiting embodiments of the invention and the accompanying drawings, in which:

[0032] Figure 1 is a schematic cross - sectional view of a turbine;

[0033] Figure 2 is a simplified schematic cross - sectional view of a bladed propeller rotor without a hydraulic compensation device according to an embodiment of the present invention;

[0034] Figure 3 is of a bladed propeller rotor having a hydraulic compensation device Figure 2 simplified schematic cross - sectional view;

[0035] Figure 4 is Figure 3 schematic cross - sectional view of the hydraulic compensation device;

[0036] Figure 5 is Figure 3 exploded perspective view of the hydraulic compensation device; and

[0037] Figure 6 is Figure 3 perspective view of the hydraulic compensation device. DETAILED DESCRIPTION

[0038] It should be noted that the present invention is particularly applicable to aircraft turbines and, in particular, to turbines comprising at least one propeller with blades such as Figure 1 shown. Preferably, the propeller is non - streamlined.

[0039] The aircraft engine propeller rotor 100 rotates about a rotation axis X. The propeller includes a circle of blades 200 distributed about the rotation axis X, and each of the blades 200 includes a root 300. The propeller rotor extends in front of the body 400 of the engine, which may include a wheel 5 of variable pitch blades for rectifying the air flow, a combustion chamber, and a turbine for expanding the gas.

[0040] The blades 200 are fastened to trunnions 30 which are movably mounted to rotate about a central axis Y which is substantially perpendicular to the rotation axis X of the aircraft engine. The blades 200 are guided to rotate about the axis Y by bearings arranged on both sides of the trunnions 30.

[0041] The propeller rotor further includes a hub 31 arranged around the trunnions, and the hub 31 and the blade trunnions 30 define a cavity 32 for the circulation of lubricant. It should be noted that this cavity also leads to the bearings.

[0042] ​​​​​​For the normal operation of the bearing, the bearing must be in continuous contact with the lubricant. However, during the operation of the turbine, the expansion of the lubricant due to the increase in temperature requires a limited amount of lubricant to be implemented in the cavity to avoid the risk of damaging the components of the propeller rotor. By limiting the amount of lubricant, the expansion and pressure exerted on the components of the propeller rotor are thus limited. However, if the volume of the lubricant is less than the volume of the cavity, the lubricant no longer has to be in continuous contact with the bearing.

[0043] Therefore, the rotor 100 also includes the hydraulic compensation device 2 according to the present invention mounted in the cavity 32.

[0044] In fact, the smaller amount of lubricant implemented is compensated by the volume occupied by the hydraulic compensation device in the cavity. Thus, the lubricant remains in continuous contact with the bearing.

[0045] Now in combination with Figures 3 to 6 An embodiment of a hydraulic compensation device intended to be arranged in a cavity 32 for the circulation of lubricant is presented.

[0046] As shown in the figure, the compensation device includes an annular body 21 and a piston 22, which is also annular. The annular body and the piston are arranged around a central axis Y.

[0047] The hydraulic compensation device 2 is fastened to the propeller rotor 100 via the annular body 21, which is fastened against the inner wall of the hub 31. The annular body can be tightly mounted, for example, by shrinkage.

[0048] In the illustrated embodiment, the annular body 21 is at least partially made of metal, metal alloy or plastic.

[0049] For example, the annular body 21 can be at least partially made of titanium, stainless steel or a composite material resistant to the temperatures that the turbine may be subjected to.

[0050] The piston 22 is at least partially made of PTFE (raw or filled) or an elastomer resistant to the temperatures that the turbine may be subjected to.

[0051] Therefore, the piston 22 also serves as a seal.

[0052] The annular body 21 is hollow and has a U-shaped profile oriented towards the axis X of the turbine, such that the annular body has a groove 210 forming a track in which the piston 22 can slide at least between an initial position and a retracted position.

[0053] More precisely, here, the piston 22 can slide in the annular body 21 along the central axis Y, that is, perpendicular to the axis of the turbine.

[0054] The piston forms a seal here such that during the sliding of the piston, the same amount of air remains trapped in the groove 210 between the annular body and the piston.

[0055] In this embodiment, the initial position corresponds to the position when the turbine is not operating, so the piston is flush with the end of the annular body and is axially stopped by the element forming the cavity 32 or via a stop ring (not shown). The retracted position corresponds to the position where, when the turbine is operating, the piston is received in the groove and the lubricant exerts a constant pressure on the components forming the cavity 32 on the rotor and stator sides, and this constant pressure corresponds to the pressure of the aircraft turbine at cruise speed.

[0056] This initial position can be adjusted, for example, according to installation requirements or the prestress defined during the design of the turbine.

[0057] In order to reset the piston towards the initial position when the pressure exerted by the lubricant decreases, the device includes at least one return spring 23 arranged between the annular body 21 and the piston 22.

[0058] This return spring 23 exerts a return force on the piston 22 to reset the piston towards the initial position.

[0059] In this embodiment, the hydraulic compensation device includes a plurality of return springs 23 angularly distributed between the annular body 21 and the piston 22.

[0060] According to an alternative (not shown), the hydraulic compensation device can include a single circumferential spring.

[0061] In order to limit the deformation of the piston (especially the deformation in the area in contact with the return spring when the return spring exerts a return force), the hydraulic compensation device further includes a bearing washer 24 arranged between one or more return springs 23 and the piston 22.

[0062] In this embodiment, the bearing washer 24 is at least partially made of metal or metal alloy.

[0063] In particular, the bearing washer can be made of stainless steel or titanium.

[0064] According to an alternative, preferably, the bearing washer can also be at least partially made of composite plastic.

Claims

1. A hydraulic compensation device (2), the hydraulic compensation device being intended to be arranged in a cavity (32) of a bladed propeller rotor (100) of a turbine having an axis (X), the cavity being for the circulation of a lubricant, characterized in that, The hydraulic compensation device includes an annular body (21) and a piston (22). The annular body (21) has a groove (210) forming a track, and the piston (22) can slide in the track at least between an initial position and a retracted position.

2. The hydraulic compensation device according to claim 1, characterized in that The hydraulic compensation device includes at least one return spring (23). The at least one return spring is arranged between the annular body (21) and the piston (22) and is configured to apply a return force to the piston (22) to return the piston towards the initial position.

3. The hydraulic compensation device according to claim 1 or 2, characterized in that The hydraulic compensation device further includes a bearing washer (24) arranged between the at least one return spring (23) and the piston (22).

4. The hydraulic compensation device according to the previous claim, characterized in that, The bearing washer (24) is at least partially made of metal or metal alloy, or preferably made of composite plastic.

5. The hydraulic compensation device according to any one of the preceding claims, characterized in that, The annular body (21) is at least partially made of metal, metal alloy or plastic.

6. The hydraulic compensation device according to any one of the preceding claims, characterized in that, The piston (22) is at least partially made of virgin PTFE, filled PTFE or elastomer.

7. A vane propeller rotor (100) of a turbine having an axis (X), the propeller rotor comprising vane trunnions (30) capable of rotational movement about an axis (Y) perpendicular to the axis (X) of the turbine, and a hub (31) arranged around the trunnions (30), the hub (31) and the vane trunnions (30) defining a cavity (32) for the circulation of a lubricant, characterized in that, The rotor further includes a hydraulic compensation device (2) according to any one of claims 1 to 6. The hydraulic compensation device (2) is installed in the cavity (32).

8. The propeller rotor (100) according to the preceding claim, characterized in that, The piston (22) can slide in the annular body (21) along the axis (Y).

9. The propeller rotor (100) according to claim 7 or 8, characterized in that, The hydraulic compensation device (2) is fastened to the propeller rotor (100) via the annular body (21). The annular body is fastened against the inner wall of the hub portion (31).

10. A propeller with blades, characterized in that, The blade - carrying propeller includes a rotor according to any one of claims 7 to 9.

11. An aircraft turbine, the aircraft turbine including at least one blade - carrying propeller according to claim 10.

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