MECHANICAL PART FOR AN AIRCRAFT TURBOMACHINE AND CORRESPONDING TURBOMACHINE.

Abstract

The invention relates to a mechanical part (30) for an aircraft turbomachine, the mechanical part being made of metal and comprising at least one profiled surface (34) configured to ensure oil flow during operation. According to the invention, said surface (34) comprises a coating (40) that is more hydrophobic and / or lipophobic than the surface, or a surface texture (39) that renders said surface more hydrophobic and / or lipophobic. (Shorthand figure: Figure 4)

Description

Title of the invention: MECHANICAL PART FOR AN AIRCRAFT TURBOMACHINE AND CORRESPONDING TURBOMACHINE PONDANTE. Scope of the invention

[0001] The present invention relates to the general field of turbomachinery and, in particular, aircraft turbomachinery. It specifically relates to a turbomachine component designed to ensure oil flow during operation. Technical background

[0002] An aircraft turbomachine consumes oil to operate. This oil is necessary, for example, to lubricate mechanical parts, such as bearings or gears, and can also be used to cool these parts.

[0003] Certain mechanical parts of an aircraft turbomachine have profiled surfaces to ensure oil flow during operation. This is the case, for example, with the oil recovery channels for the lubrication of a mechanical gearbox, particularly a gear train.

[0004] A mechanical reducer is designed to modify the speed and torque ratio between an input shaft and an output shaft of a mechanical system. Generally, the mechanical reducer comprises a sun gear, a ring gear, and planet gears that mesh between the sun gear and the ring gear. The planet gears are held by a frame called a planet carrier.

[0005] Several gearbox architectures exist. In the state of the art for turbofan engines, gearboxes are of the planetary or epicyclic type. In other similar applications, there are so-called differential or compound architectures. In a planetary gearbox, the planet carrier is fixed, and the rotating ring gear forms the output shaft of the device, which rotates in the opposite direction to the sun gear. In an epicyclic gearbox, the ring gear is fixed, and the planet carrier forms the output shaft of the device, which rotates in the same direction as the sun gear. In a differential gearbox, no element is fixed for rotation. The ring gear rotates in the opposite direction to both the sun gear and the planet carrier.

[0006] Since these gearboxes are composed of several wheels and / or gears that mesh with each other, their lubrication is a crucial aspect for the proper functioning of the gearbox and the turbomachine. Indeed, when the gearbox is not sufficiently lubricated, friction between the teeth of the wheels and / or gears or at the bearings leads to premature wear and thus a decrease in Gearbox efficiency. Furthermore, the gear train of gearboxes generates significant heat, which causes the oil to heat up during operation; the oil absorbs heat energy generated by the gearbox. The oil temperature impacts its viscosity and lubrication efficiency. Therefore, it is important to remove the hot oil after the gearbox has been lubricated in order to recycle it. Recycling involves cooling, filtering, and deaerating the oil before it is reintroduced into the lubrication system. Recycling also helps prevent increased losses due to gearbox ventilation, rising temperatures of the gearbox's internal components, excessive air content in the oil, and other issues.

[0007] To recover the oil, an annular gutter formed around the outer ring of the gearbox has been proposed. The gutter typically has a U-shaped cross-section. The bottom and side walls of the gutter have a surface oriented towards the periphery of the ring, designed to receive the oil spray by centrifugal force. The oil flows along this surface to an outlet located at the bottom of the gutter. Examples of gutters are described in patent application FR-A1-3081513.

[0008] However, since the reducer requires a high oil flow for its operation, it is important that this oil flow be channeled and evacuated as quickly as possible in order to be cooled and then reinjected into the lubrication system of the reducer.

[0009] The invention aims to avoid the aforementioned drawbacks. Summary of the invention

[0010] The objective of the invention is to provide a simple, effective and economical solution to facilitate the flow of a fluid such as oil over an aircraft turbomachine part.

[0011] We achieve this objective by means of a mechanical part for an aircraft turbomachine, the mechanical part being made of metal and comprising at least one profiled surface configured to ensure oil flow in operation, said surface comprising a coating more hydrophobic and / or lipophobic than said surface or a surface texturization making said surface more hydrophobic and / or lipophobic.

[0012] Thus, this solution makes it possible to achieve the aforementioned objective. In particular, the surface coating or texturizing makes the oil flow surface hydrophobic and / or lipophobic. This reduces the oil's spreading coefficient on the surface and therefore promotes the formation of droplets, for example, rather than the oil spreading across the surface, which would then form a film. This facilitates the flow of the oil over the surface, which does not "stick" to it. Therefore, this accelerates the flow. Accelerating the oil on the surface limits the impact of the ventilation air on the oil. It can also accelerate oil removal and recycling, thus reducing the amount of oil consumed during turbomachine operation.

[0013] The mechanical part comprises one or more features, taken alone or in combination:

[0014] - the part is an annular lubricating oil recovery gutter, made of par particular for a mechanical reducer.

[0015] - the surface is opposite oil ejection means.

[0016] - coating or said texturing extends over only a part of said surface streamlined.

[0017] - said coating or said texturing extends over the entirety of said surface.

[0018] - the mechanical part extends circumferentially around an axis and presents in cuts a U shape, the U shape comprising two opposing side walls and a bottom wall, the surface being at least a surface of the bottom wall and these walls being configured to ensure oil flow in operation, at least a part of the surface comprising a hydrophobic and / or lipophobic coating or surface texturing rendering said surface hydrophobic and / or lipophobic.

[0019] - the hydrophobic coating is made of polymer, and in particular a fluoropolymer such as than a polytetrafluoroethylene.

[0020] - surface texturization includes a surface repetition of recessed or bumps of micrometric or nanometric dimensions, created for example by laser.

[0021] The invention also relates to a mechanical reducer for an aircraft turbomachine, the mechanical reducer having a planetary gear train and comprising a sun gear, a ring extending around the sun gear, satellites meshed with the sun gear and the ring, and at least one mechanical part, having any one of the preceding characteristics, arranged radially around the ring so that the surface extends around the ring.

[0022] The invention also relates to a turbomachine comprising at least one mechanical part of a turbomachine as above or a mechanical reducer as above.

[0023] The invention further relates to an aircraft comprising at least one turbomachine as mentioned above. Brief description of the figures

[0024] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent upon reading the ex description detailed explanation that follows, of embodiments of the invention given by way of purely illustrative and non-limiting examples, with reference to the attached schematic drawings in which:

[0025] [Fig.1] Fig.1 represents an axial section of a turbomachine using the invention;

[0026] [Fig.2] [Fig.2] is a partial schematic axial cross-sectional view of a reducer mechanical system installed in a turbomachine according to the invention;

[0027] [Fig.3] The [Fig.3] is a schematic and cross-sectional view of an example of a mechanical reducer;

[0028] [Fig.4] Fig.4 is a schematic and partial view of a mechanical part of a tower bomachine such as a gutter according to the invention;

[0029] [Fig.5] The [Fig.5] is a schematic, perspective and partial view of an example of the realization of a mechanical part of a turbomachine with a hydrophobic and / or lipophobic surface according to the invention;

[0030] [Fig.6] The [Fig.6] is a schematic, perspective and partial view of another example of the realization of a mechanical part of a turbomachine with a hydrophobic and / or lipophobic surface according to the invention;

[0031] [Fig.7] Fig.7 is a very schematic view of examples of surface texturing for a mechanical part according to the invention, and

[0032] [Fig.8] Fig.8 is a very schematic and cross-sectional view of a mechanical part of a turbomachine, the surfaces of which have hydrophobic and / or lipophobic coatings according to the invention. Detailed description of the invention

[0033] Figure 1 shows a turbomachine intended for mounting on an aircraft. The turbomachine illustrated is a turbofan, but the invention is not limited to this type of turbomachine. The turbomachine may be a turboprop and comprise a single propeller or a pair of counter-rotating propellers rotating about a longitudinal axis and designated by the English term "open rotor" for unfaired propeller(s). The turbomachine may also be a turboshaft engine.

[0034] Generally, a twin-flow turbomachine 1, with longitudinal axis X, comprises, from upstream to downstream and in the direction of gas flow, a compressor section, a combustion chamber 1, and a turbine section. The compressor section may include a low-pressure compressor 1a and a high-pressure compressor 1b. The turbine section may include a low-pressure turbine 1e and a high-pressure turbine Id. The compressors, the combustion chamber, and the turbines form a gas generator. The high-pressure compressor 1b and the high-pressure turbine Id are connected by a high-pressure shaft 2 and together form a body high pressure (HP). The low pressure compressor and the low pressure turbine are connected by a low pressure shaft 3 and together form a low pressure (LP) unit.

[0035] Downstream of the low-pressure turbine, an exhaust nozzle Ih is arranged allowing the evacuation of gases from the combustion chamber to the outside.

[0036] Upstream of the low-pressure compressor, a blower 4 is mounted. The blower 4 is driven by a blower shaft 5, which is driven by the LP shaft 3 by means of a mechanical reduction gear 6. The blower 4 comprises a plurality of blower blades 7 extending radially outwards from a blower disc. The blower blades 7 are radially delimited by a blower housing 8. The latter carries a nacelle attached to the aircraft.

[0037] The reduction gear 6 is formed by a gear train and is known by the English acronym RGB for "Reduction Gear Box". The reduction gear 6 is generally of the planetary or epicyclic type. The reduction gear comprises, as schematically illustrated in [Fig. 2], a sun gear 10 (or inner planet gear), planet gears 11, a planet carrier 12, and a ring gear 13 (or outer planet gear). The sun gear 10, the ring gear 13, and the planet carrier 12 are planet gears because their axes of revolution coincide with the longitudinal axis X of the turbomachine. The planet gears each have a different axis of revolution and are equally spaced on the same operating diameter around the axis of the planet gears. These axes are parallel to the longitudinal axis X.

[0038] In the present example, the reducer 6 is a planetary gear train. The input of the reducer is coupled to the shaft BP 3, while the output of the reducer is coupled to the blower shaft. In particular, the ring gear 13 is rotatable and the planet carrier 12 is fixed against rotation.

[0039] Although the following description relates to a planetary type gear train reducer, it also applies to an epicyclic gear train or a mechanical differential gear train in which the three components, namely the planet carrier, the ring gear and the sun gear, are mobile in rotation, the rotational speed of one of these components depending in particular on the difference in speeds of the other two components.

[0040] The gearbox 6 is positioned in the upstream part of the turbomachine. A fixed structure 14 schematically comprises, here, an upstream part 14a and a downstream part 14b, which together form the motor or stator housing. The fixed structure is arranged to form an enclosure E surrounding the gearbox 6. This enclosure E is closed upstream by seals at an upstream bearing that allows the fan shaft 5 to pass through, and downstream by seals at the point where the BP shaft 3 passes through. The upstream bearing supports and guides the rotation of the fan shaft 5 to bear the radial and axial loads to which it is subjected. This upstream bearing is mounted in enclosure E. Two upstream bearings can be provided to guide the fan shaft 5 in rotation as illustrated in [Fig.2].

[0041] Figures 2 and 3 show the reducer 6, which can take on different configurations depending on whether certain parts are fixed or rotating. At the input, the reducer 6 is connected to the shaft BP 3, for example, via internal splines 15. Thus, the shaft BP 3 drives the solar element. Typically, the solar element 10, whose axis of rotation coincides with that of the turbomachine X, drives the satellite elements 11, which are evenly spaced around the same diameter around the axis of rotation X. This diameter is equal to twice the operating center distance between the solar element 10 and the satellite elements 11. The number of satellite elements 11 is generally defined as between three and seven for this type of application.

[0042] The set of satellites 11 is held by a frame which is the satellite carrier 12. Each satellite 11, in the form of a pinion, rotates about its own Y-axis and meshes with the ring gear 13. At the output, the set of satellites 11 is held by the satellite carrier 10, which is fixed to the motor or stator housing 14. Each satellite drives the ring gear 13, which is connected to the blower shaft 4. A ring carrier 16 is provided to connect the blower shaft 10 to the ring gear 13. The satellites 11 are mounted to rotate freely using bearings, for example, roller bearings or hydrostatic bearings. Each bearing is mounted on one of the axes of the satellite carrier, and all the axes are positioned relative to each other using one or more structural frames of the satellite carrier.

[0043] In [Fig. 4], the ring gear 13 is provided with internal teeth that mesh with the teeth of the planet gears. In the present embodiment, the ring gear 13 is formed in two parts (i.e., two half-rings). A downstream half-ring gear 17 consists of a rim 17a and a mounting half-flange 17b. The flange 17b extends radially outwards. An upstream half-ring gear 18 consists of a rim 18a and a mounting half-flange 18b. The flange 18b extends radially outwards. The rim 17a includes a portion of upstream teeth in the form of an upstream helix of the gear teeth. This upstream helix meshes with that of satellite 11, which meshes with that of solar 10. The rim 18a, for its part, includes a portion of downstream teeth, also in the form of a downstream helix of the reduction gear's teeth. This downstream helix meshes with that of satellite 11, which meshes with that of solar 10.This configuration makes manufacturing the crown even easier and facilitates oil recovery. While the helix widths vary between the solar element 10, the satellite elements 11, and the crown element 13 due to tooth overlaps, they are all centered on a median plane for the upstream helices and on another median plane for the downstream helices.

[0044] The 17b fixing half-clamp of the downstream half-crown and the fixing half-clamp 18b of the upstream half-crown form the crown mounting flange 19. The crown 13 is fixed to the crown carrier by assembling the crown mounting flange 19 and a crown carrier mounting flange. This fixing is achieved using fasteners 20 such as screws, bolts and / or nuts.

[0045] In operation, oil enters the gearbox 6 from the stator section 14 via a distributor (not shown) by various means specific to one or more types of architecture. The distributor is divided into two parts, each generally repeated with the same number of planet gears. The distributor includes injectors 21a (see [Fig. 3]) which lubricate the gear teeth of the gearbox wheels and / or pinions, and arms which lubricate the gearbox bearings. Oil is supplied to the injectors 21a and exits at their ends to lubricate, with so-called cold oil (HF), the gear teeth of the planet gears 11, the sun gear 10, and also the ring gear 13. Oil is also supplied to the arm and circulates through the bearing's oil inlet. The oil then flows through the shaft into one or more buffer zones and then exits through the orifices to lubricate the satellite bearings.

[0046] With reference to [Fig. 3] and due to centrifugal forces, hot oil HC for lubricating the gear teeth is projected radially outwards relative to the Y axes of the planet gears. The hot oil is also projected and ejected by centrifugal force from the ring gear 13. In particular, the oil is ejected radially outwards at the mounting flange 19 via oil ejection means. The ejection means here comprise one or more channels that are regularly formed between the two half-rings and around the entire circumference of the ring gear 13.

[0047] Advantageously, but not exclusively, first channels 22 extend substantially along the radial axis Z. Each first channel 22 extends radially between an inlet orifice 23 defined in an internal surface of the ring (which includes the teeth) and an outlet orifice 24 defined on the periphery of the mounting flange 19. Preferably, but not exclusively, there are several outlet orifices 24 distributed circumferentially around the periphery of the flange 19. The oil flows from the inside of the ring 13 to the outside of the latter via the channel(s) 22. Second channels may also allow the oil flowing around the external periphery of the ring to be discharged back into the first channels 22.

[0048] With reference to [Fig. 4], the turbomachine is also equipped with an oil recovery device designed to quickly recover and remove the oil ejected by centrifugal force from the gearbox 6 and also from the enclosure E. The recovery device comprises an annular oil recovery trough 30, which is intended to collect the oil ejected from the gearbox 6. The trough 30, centered on the longitudinal axis X, is arranged around the ring 13. The trough 30 is fixed to a fixed structure of the turbomachine (stator). Advantageously, the gutter 30 is fixed to the enclosure E surrounding the gearbox. The gutter 30 has a generally U-shaped axial cross-section. More precisely, the gutter 30 comprises a bottom wall 31 from which extend a first side wall 32 and a second side wall 33. The bottom wall 31 and the side walls 32, 33 are annular and centered on the longitudinal axis X. The side walls 32, 33 extend substantially radially (perpendicular to the longitudinal axis X).

[0049] The bottom wall 31 is arranged radially outside the ring 13 and is oriented towards the oil ejection means. The side walls 32, 33 (referred to as the first and second walls) are arranged on either side of the mounting flange 19 along the longitudinal axis. As we can see in [Fig. 4], the gutter 30 includes a profiled surface 34, here internal, which is opposite the reducer 6 and the ring 13. Each side wall 32, 33 includes a peripheral edge 35 delimiting an internal diameter of the gutter that is smaller than the external diameter of the ring 13 defined by the periphery of the fixing flange 19. Similarly, the axis of the fixing elements 20 of the fixing flange 19 delimits a diameter that is larger than the internal diameter of the peripheral edges 35. Such a configuration prevents the phenomenon of external air being drawn into the gutter.To enhance this advantage, the bottom wall 31 and the side walls 32, 33 are arranged at a predetermined distance from the mounting flange 19, in particular its periphery and the fastening elements 19. These predetermined distances take into account the axial displacements of the ring during the operation of the reducer, manufacturing tolerances and the thermal expansion of the parts.

[0050] In the example shown, the gutter 30 is formed of two parts to facilitate its assembly and disassembly in the turbomachine. Of course, the gutter could be formed from a single piece of material. The gutter 30 comprises a first part 30a and a second part 30b. The first part 30a comprises a first tab 36, the first side wall 32, and a portion of the bottom wall connecting the first tab 36 and the first side wall 32. The second part 30b comprises a second tab 37, the second side wall 33, and a portion of the bottom wall connecting the second tab 37 and the second side wall 33. The first and second tabs 36, 37 extend radially outwards. In particular, the first and second tabs 36, 37 each comprise a bearing surface defined in a plane, and these planes are parallel.The first and second parts are fixed together at the first and second legs. Fasteners 38 allow the legs 36, 37 to be fixed together. The fasteners 38 include screws, nuts, bolts, or any other suitable fastener. In this embodiment, the first leg 35 includes a . An annular recess 36a is designed to receive part of the second leg 37. The internal surfaces of the bottom and side wall portions are continuous and flush. The first leg 36, which is longer than the second leg 37, allows the gutter 30 to be attached to the fixed structure of the turbomachine.

[0051] According to another alternative, the gutter 30 includes a single radial tab allowing attachment to the fixed structure of the turbomachine.

[0052] The gutter 30 is made of a metallic material. The metallic material can be steel or titanium. Advantageously, but not exclusively, the gutter 30 is made from sheet metal to reduce its weight. The walls 31, 32, 33 are obtained by bending or welding. Bending and welding are quick and easy to perform and require very little tooling to manufacture the gutter.

[0053] Figure 5 shows a first embodiment of a gutter 30 in which the internal, profiled surface 34 comprises a hydrophobic and / or lipophobic coating or a surface texture that renders said surface hydrophobic and / or lipophobic. In this description, the terms "hydrophobic" and "lipophobic" (and even "oleophobic") refer to the ability of a surface to repel water and / or oil from said surface in order to reduce the contact area between the surface and the resulting droplet. Such properties thus make it possible to reduce the coefficient of friction. The coating or textured surface allows for a lower coefficient of friction between the surface of the water and / or oil and the metallic surface with the coating.More specifically, the lipophobic and / or hydrophobic nature of a surface allows the fluid (water / oil / grease) to bead (form beads) when it comes into contact with the mechanical part, thus contributing to efficient fluid drainage. Similarly, "more lipophobic / hydrophobic" also means that the surface is less lipophilic / hydrophilic, in other words, the fluid will be less likely to spread or remain on the surface.

[0054] The coating or texturing extends over the entire internal surface of the side walls and the bottom wall.

[0055] Figure 6 shows a second embodiment of the gutter 30 in which only the surface of the side walls 32, 33 includes a coating or surface texture. In other words, the surface of the bottom wall is devoid of coating or texture.

[0056] According to an alternative not shown, the surface coating or texture extends over predetermined areas of the side walls 32, 33 and / or the bottom wall 31. The predetermined areas may correspond to annular bands opposite the fastening elements 38 and / or the fastening flange 09. In the case of annular areas provided on the side walls, these would be located away from the perimeter edges 34 spheres of side walls 32, 33. In the case of the bottom wall area, this would be away from the side walls.

[0057] Fig. 7 shows various examples of surface texturing 39 for the whole surface or certain areas of the surface.

[0058] The surface texture 39 preferably comprises a surface repetition of recessed or raised patterns of micrometer dimensions. The dimensions may also be on the order of nanometers. The patterns may be linear or point-like. The texture 38 is advantageously, but not exclusively, achieved using a micromachining process by material removal. An example of a micromachining process is laser micromachining.

[0059] The recessed or raised patterns reduce the surface area in contact with the fluid containing water and / or oil, thereby reducing friction between the water and / or oil and the surface. In this way, the patterns have the effect of repelling the fluid, which then flows or moves more rapidly over the coating or textured surface.

[0060] Fig. 8 shows an example of a hydrophobic and / or lipophobic coating 40 intended to coat the internal surface of the side walls and / or bottom wall or certain predetermined areas thereof.

[0061] The hydrophobic and / or lipophobic coating 40 is preferably made of a polymer, and in particular a fluoropolymer such as polytetrafluoroethylene (PTFE). It has, for example, a thickness of between 1 and 100 µm. It can be obtained by spraying a solution onto the internal surface of each surface and heating it to polymerize and harden the coating.

[0062] Thus, the mechanical part, here the oil recovery gutter 30, equipped with such a coating 40 or such a texture 39, facilitates the recovery and drainage of the oil. The flow is facilitated because by decreasing the oil's spreading coefficient, we increase the speed and thus the drainage rate of the gutter. This drainage is particularly important during the aircraft's operating or flight phases when the gearbox requires a significant oil flow rate, such as during takeoff.

[0063] Hydrophobic and / or lipophobic coatings and texturing offer the same advantages mentioned above. The advantage of texturing over coatings is that it does not introduce potential pollutants, as coatings are susceptible to degradation during operation and the release of unwanted elements into the engine.

Claims

Demands

1. Mechanical part (30) for an aircraft turbomachine, the mechanical part being made of metal and comprising at least one profiled surface (34) configured to ensure oil flow in operation, characterized in that said surface (34) comprises a coating (40) more hydrophobic and / or lipophobic than said surface (34) or a surface texturing (39) making said surface more hydrophobic and / or lipophobic, the part being an annular lubricating oil recovery gutter (30), in particular for a mechanical reducer (6).

2. Mechanical part (30) according to claim 1, characterized in that the surface (34) is opposite oil ejection means.

3. Mechanical part (30) according to any one of claims 1 to 2, characterized in that said coating (40) or said texturing (38) extends over only a part of said surface (34).

4. Mechanical part (30) according to any one of claims 1 to 2, characterized in that said coating (40) or said texturing (39) extends over the entire surface (34).

5. Mechanical part according to any one of claims 1 to 4, characterized in that it extends circumferentially around an axis and has in cross-section a U shape, the U shape comprising two opposing lateral walls (32, 33) and a bottom wall (31), the surface (34) being at least a surface of the bottom wall (31) and these walls being configured to ensure oil flow in operation, at least a part of the surface (34) comprising a hydrophobic and / or lipophobic coating (40) or a surface texturization (39) rendering said surface hydrophobic and / or lipophobic.

6. Mechanical part (30) according to any one of claims 1 to 5, wherein the hydrophobic coating (40) is made of polymer, and in particular a fluoropolymer such as a polytetrafluoroethylene.

7. Mechanical part (30) according to any one of claims 1 to 5, characterized in that the surface texturing (39) comprises a surface repetition of hollow patterns or bumps of micrometric or nanometric dimensions, produced for example by laser.

8. Mechanical reducer (6) for an aircraft turbomachine, the mechanical reducer having a planetary gear train and comprising a sun gear (10), a ring gear (13) extending around the sun gear, satellites (11) meshed with the solar (10) and the crown (13), and a mechanical part (30) according to any one of the preceding claims forming a gutter by being arranged radially around the crown (13) so that the surface (20a) extends around the crown (13).

9. Turbomachine (1), in particular aircraft, comprising at least one mechanical part (30) according to any one of claims 1 to 7 or a mechanical reducer (6) according to claim 8.

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