Hydraulic compensation device

Abstract

The invention relates to a hydraulic compensation device (2) for placement in a cavity (32) for circulating a lubricant of a bladed propeller rotor (100) in a turbomachine, the rotor having an axis (X), characterized in that said compensation device comprises an annular part (21) and a piston (22), the annular part (21) having a groove (210) that forms a track in which the piston (22) can slide between at least a starting position and a retracted position.

Description

[0001] DESCRIPTION

[0002] TITLE: HYDRAULIC COMPENSATION DEVICE

[0003] Field of invention

[0004] The present invention relates to the field of turbomachines and more particularly concerns unducted type turbomachines.

[0005] More particularly, the invention relates to a hydraulic compensation device intended to be arranged in a cell for a lubricant of a propeller rotor with blades of a turbomachine.

[0006] The invention relates to all types of aircraft turbomachine, in particular turbojets and turboprops having a bladed propeller.

[0007] State of the prior art

[0008] Turbomachine propeller rotors conventionally comprise, for each blade, a blade journal that can rotate around an axis perpendicular to the axis of the turbomachine, and a hub arranged around the blade journal.

[0009] Propeller blade journals are guided in rotation by means of bearings which need to be permanently lubricated at the contact surface between the rolling element and the raceway so that their operation is not impaired. Therefore, a lubricant is generally used in the cavity delimited by the hub and the blade journal and leading to the bearings. So that the bearings are permanently lubricated and therefore so as to ensure a thin layer of lubricant between the rolling element and the bearing rings, it is necessary that the cavity is almost entirely or even completely filled with this lubricant so that on all rotations of the blade, the bearing is always lubricated.

[0010] However, during flight phases, and particularly during takeoff, temperatures in the cell can reach hundreds of degrees, and therefore result in an increase in pressure linked to the expansion of the lubricant, for example oil, of approximately 11.25 bars per degree Celsius. If the expansion of the lubricant is not contained during flight phases, then the internal pressure in the cells can reach several hundred bars of pressure, which can cause damage to the seals as well as surrounding parts such as the propeller hub.

[0011] In order to limit the increase in the internal pressure of the system, it is thus known to implement hydraulic compensation devices, notably taking the form of an expansion tank. Several expansion tank systems are generally used, with an expansion tank implementing a deformable elastomer membrane, or an expansion tank implementing a piston as for example described in document FR2498278. In the case of an elastomer membrane, the disadvantage is that this requires in particular having an elastomer compatible with the operating temperatures and the nature of the lubricant, and requires ensuring a certain static seal at the level of the membrane maintenance. In addition, this solution adds an additional element which can have an impact on the ease of implementation and on the capacity of integration on aeronautical applications, but also a mass impact, notably at the level of a propeller rotor.

[0012] Another problem with current solutions is that current hydraulic compensation devices are implemented in the form of external expansion tanks and therefore require the addition of additional means. In addition, it is relatively difficult to integrate such external solutions into aeronautical applications, particularly at the level of propeller rotors, whose performance also depends on balancing by correcting unbalances, without disturbing the proper functioning of such complex aeronautical systems.

[0013] There is therefore a need to provide a solution to ensure the lubrication of the propeller rotor while compensating for pressure increases due to the increase in temperature during the operation of turbomachines.

[0014] Statement of the invention

[0015] The invention aims to remedy at least in part the drawbacks mentioned above relating to the techniques of the prior art.

[0016] To this end, the invention relates to a hydraulic compensation device intended to be arranged in a lubricant circulation cell of a propeller rotor with X-axis turbomachine blades. According to the invention, the device comprises an annular body and a piston, said annular body having a groove forming a track in which said piston is capable of sliding between at least one initial position and a retracted position.

[0017] Thus, the invention provides a novel and inventive approach to at least partially resolving some of the drawbacks of the prior art.

[0018] In particular, such an invention makes it possible to ensure the lubrication of the propeller rotor while compensating for pressure increases due to the increase in temperature during the operation of the turbomachines. Indeed, the space occupied by the hydraulic compensation device makes it possible to put a smaller quantity of lubricant, while continuing to completely fill the cavity with oil, and therefore to limit its expansion, while ensuring permanent contact between the lubricant and the bearings.

[0019] Furthermore, the integration of such a solution proves to be relatively simple, without disrupting the proper functioning of such complex aeronautical systems. 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 said annular body and said piston and configured to exert a return force on said piston so as to return it to said initial position.

[0020] Preferably, the return force on said piston so as to bring it back to said initial position can be exerted during engine shutdown phases.

[0021] According to a particular aspect of at least one embodiment of the invention, the hydraulic compensation device further comprises a support washer provided between the at least one return spring and said piston.

[0022] Such a support washer thus makes it possible to have support between the at least one support spring and the piston while limiting the deformation of the piston, in particular at the level of the contact zones with the return spring(s).

[0023] According to a particular aspect of at least one embodiment of the invention, said support washer is made at least partially from a metal or a metal alloy, or from a plastic, preferably a composite.

[0024] According to a particular aspect of at least one embodiment of the invention, said annular body is made at least partially from a metal, a metal alloy, or a plastic.

[0025] According to a particular aspect of at least one embodiment of the invention, said piston is made at least partially from virgin PTFE, filled PTFE, or an elastomer.

[0026] It should be noted that the piston may also include metal pre-tightening springs.

[0027] The advantage of such a material is that the piston itself can also act as a seal.

[0028] The invention also relates to a propeller rotor with X-axis turbomachine blades, comprising a blade journal rotatable about a Y axis perpendicular to said X axis of the turbomachine, and a hub arranged around said journal, said hub and said blade journal delimiting a cell for circulation of a lubricant. According to the invention, said rotor further comprises a hydraulic compensation device according to one of the aforementioned embodiments, said hydraulic compensation arrangement being mounted in said cell.

[0029] According to a particular aspect of at least one embodiment of the invention, said piston is capable of sliding in said annular body along said axis Y.

[0030] According to a particular aspect of at least one embodiment of the invention, said hydraulic compensation device is fixed to said propeller rotor by means of said annular body fixed against an inner wall of said hub. The invention also relates to a bladed propeller, comprising a rotor according to one of the aforementioned embodiments.

[0031] The invention also relates to a turbomachine for an aircraft, comprising at least one bladed propeller.

[0032] According to a particular aspect of at least one embodiment, the turbine is a turbojet.

[0033] Presentation of figures

[0034] The invention, as well as the various advantages that it presents, will be more easily understood in the light of the following description of an illustrative and non-limiting embodiment thereof, and of the appended drawings among which:

[0035] [Fig. 1] is a schematic sectional view of a turbomachine;

[0036] [Fig. 2] is a simplified schematic sectional view of a bladed propeller rotor according to one embodiment of the invention, without the hydraulic compensation device;

[0037] [Fig. 3] is a simplified schematic sectional view of the bladed propeller rotor of Fig. 2, with the hydraulic compensation device;

[0038] [Fig. 4] is a schematic sectional view of the hydraulic compensation device of Figure 3; [Fig. 5] is an exploded perspective view of the hydraulic compensation device of Figure 3, and

[0039] [Fig. 6] is a perspective view of the hydraulic compensation device of Figure 3.

[0040] Detailed description of an embodiment of the invention

[0041] It should be noted that the invention applies in particular to aircraft turbomachines, and in particular to turbomachines comprising at least one propeller with a blade as shown in Figure 1. Preferably, this propeller is unducted.

[0042] This aircraft engine propeller rotor 100 rotates around an axis of rotation X. The propeller comprises a circle of blades 200 distributed around the axis of rotation X and each of the blades 200 comprises a root 300. The propeller rotor extends in front of a main body 400 of the engine, which may comprise a wheel 5 of variable-pitch blades straightening the air flow, a combustion chamber, and gas expansion turbines.

[0043] The blades 200 are fixed at a journal 30 mounted to rotate about a central axis Y which is substantially perpendicular to the axis of rotation X of the aircraft engine. The blades 200 are guided in rotation about the Y axis by bearings arranged on either side of the journal 30. The propeller rotor also comprises a hub 31, arranged around the journal, the hub 31 and the blade journal 30 delimiting a cell 32 for circulation of a lubricant. It should be noted that this cell also opens onto the bearings.

[0044] For proper operation, bearings must be in permanent contact with lubricant. However, the expansion of the lubricant due to the rise in temperature during turbomachine operation requires the use of a limited quantity of lubricant within the cell, to avoid the risk of damaging the propeller rotor components. By limiting the quantity of lubricant, the expansion and pressure exerted on the propeller rotor components are limited. However, the lubricant is no longer necessarily in continuous contact with the bearings if the volume of lubricant is less than the volume of the cell.

[0045] Therefore, the rotor 100 also comprises a hydraulic compensation device 2 according to the invention which is mounted in the cell 32.

[0046] In fact, the lower quantity of lubricant used is compensated by the volume occupied in the cells by the hydraulic compensation device. As a result, the lubricant remains in permanent contact with the bearings.

[0047] We now present, in relation to figures 3 to 6, an embodiment of a hydraulic compensation device intended to be arranged in the cell 32 for the circulation of a lubricant.

[0048] As illustrated, the compensation device comprises an annular body 21 and a piston 22 which is also annular. The annular body and the piston are arranged around the central axis Y.

[0049] This hydraulic compensation device 2 is fixed to the propeller rotor 100 by means of the annular body 21 fixed against an inner wall of the hub 31. The annular body can for example be mounted tight by shrink fitting.

[0050] In the illustrated embodiment, the annular body 21 is made at least partially from a metal, a metal alloy, or a plastic.

[0051] For example, the annular body 21 may be made at least partially from titanium, stainless steel, or composites resistant to the temperatures to which the turbomachine may be subjected.

[0052] As for the piston 22, it is made at least partially from PTFE (virgin or filled) or from an elastomer resistant to the temperatures to which the turbomachine may be subjected.

[0053] Therefore, the piston 22 also acts as a seal.

[0054] The annular body 21 is hollow and has a U-shaped profile oriented towards the axis of the turbomachine X so that this annular body has a groove 210 forming a track in which the piston 22 is able to slide between at least one initial position and a retracted position. More precisely, here, the piston 22 is able to slide in the annular body 21 along the central axis Y, that is to say perpendicular to the axis of the turbomachine.

[0055] This piston here forms a seal so that, when the piston slides, the same quantity of air remains trapped in the groove 210 between the annular body and the piston.

[0056] In this embodiment, the initial position corresponds to a position when the turbomachine is not in operation, the piston then being flush with the end of the annular body in axial stop either by the elements constituting the cell 32, or using a stop ring (not shown). As for the retracted position, it corresponds to a position in which the piston is housed in the groove when the turbomachine is in operation and the lubricant exerts a constant pressure on the components constituting the cell 32, rotor and stator side, corresponding to a pressure for an aircraft turbomachine at cruising speed.

[0057] This initial position can, for example, be adjusted according to an assembly requirement or a pre-constraint defined during the design of the turbomachine.

[0058] So that the piston is returned to the initial position when the pressure exerted by the lubricant decreases, the device comprises at least one return spring 23 arranged between the annular body 21 and the piston 22.

[0059] This return spring 23 exerts a return force on the piston 22 so as to return it to the initial position.

[0060] In this embodiment, the hydraulic compensation device comprises a plurality of return springs 23 angularly distributed between the annular body 21 and the piston 22. According to a variant not illustrated, the hydraulic compensation device may comprise a single circumferential spring.

[0061] In order to limit the deformations of the piston, in particular at the contact zones with the return springs when the latter exert a return force, the hydraulic compensation device further comprises a support washer 24 arranged between the return spring(s) 23 and the piston 22.

[0062] In this embodiment, the support washer 24 is made at least partially from a metal, a metal alloy.

[0063] The support washer can be made from stainless steel or titanium.

[0064] According to a variant, the support washer could also be made at least partially from a plastic, preferably a composite.

Claims

CLAIMS

1. Hydraulic compensation device (2) intended to be arranged in a cell (32) for circulating a lubricant of a propeller rotor (100) with turbomachine blades of axis (X), characterized in that it comprises an annular body (21) and a piston (22), said annular body (21) having a groove (210) forming a track in which said piston (22) is able to slide between at least one initial position and a retracted position.

2. Hydraulic compensation device according to claim 1, characterized in that it comprises at least one return spring (23) arranged between said annular body (21) and said piston (22) and configured to exert a return force on said piston (22) so as to return it to said initial position.

3. Hydraulic compensation device according to claim 1 or 2, characterized in that it further comprises a support washer (24) arranged between said at least one return spring (23) and said piston (22).

4. Hydraulic compensation device according to the preceding claim, characterized in that said support washer (24) is made at least partially from a metal or a metal alloy, or from a plastic, preferably a composite.

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

6. Hydraulic compensation device according to one of the preceding claims, characterized in that said piston (22) is made at least partially from virgin PTFE, loaded PTFE or an elastomer.

7. Propeller rotor (100) with turbomachine blades of axis (X), comprising a blade journal (30) movable in rotation about an axis (Y) perpendicular to said axis (X) of the turbomachine, and a hub (31) arranged around said journal (30), said hub (31) and said blade journal (30) delimiting a cell (32) for circulation of a lubricant, characterized in that said rotor further comprises a hydraulic compensation device (2) according to one of the claims 1 to 6, said hydraulic compensation arrangement (2) being mounted in said cell (32).

8. Propeller rotor (100) according to the preceding claim, characterized in that said piston (22) is capable of sliding in said annular body (21) along said axis (Y).

9. Propeller rotor (100) according to one of claims 7 or 8, characterized in that said hydraulic compensation device (2) is fixed to said propeller rotor (100) by means of said annular body (21) fixed against an inner wall of said hub (31).

10. Propeller with blades, characterized in that it comprises a rotor according to one of claims 7 to 9.

11. Turbomachine for aircraft, comprising at least one bladed propeller according to claim 10.

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