Fan blade of an aircraft turbine engine including a thermally conductive Anti-icing coating

Abstract

The invention relates to a fan blade (10) of an aircraft turbine engine, including: - a metal body (11) comprising at least one wall (12) defining a cavity (13), the wall (12) including an internal face (14) located facing the cavity (13), and an external face (15) opposite the internal face (14) and exposed to an aerodynamic air flow (F); - a device (16) for thermal protection of the fan blade (10), the thermal protection device (16) being a device (16) for protection against icing and being in contact with the wall (12), characterised in that the fan blade (10) further includes, on the wall (12), a thermally conductive coating (20) having a thermal conductivity λ2 greater than a thermal conductivity λ1 of the metal body (11).

Description

[0001] DESCRIPTION

[0002] TITLE: AIRCRAFT TURBOMACHINE FAN BLADE FEATURING A THERMALLY CONDUCTIVE COATING THAT IMPROVES THE THERMAL CONDUCTIVITY OF A METALLIC BODY

[0003] Technical field of the invention

[0004] The invention relates to the technical field of aircraft turbomachine fan blades having a metallic body. The invention specifically concerns any fan blade designed to exchange heat with its environment through its metallic walls.

[0005] Technical background

[0006] A turbomachine, particularly an aircraft turbomachine, comprises at least one annular duct, along a longitudinal axis, in which an aerodynamic airflow, called ventilation air, circulates. This ventilation air passes successively from upstream to downstream through a gas generator comprising a compressor assembly, a combustion chamber, and a turbine assembly of the turbomachine.

[0007] The terms "upstream" and "downstream" are defined in relation to the direction of gas flow in the turbomachine.

[0008] The turbomachine includes a fan located upstream of the gas generator. The fan comprises a rotor driven in rotation about its longitudinal axis by a fan shaft. The fan further comprises blades extending radially from a disk.

[0009] Among the types of fans, there are enclosed fans and unenclosed fans, also known by the English term "open rotor". Unlike enclosed fans, the blades of unenclosed fans are not surrounded by a fan housing, making them particularly exposed to external conditions.

[0010] The compressor assembly comprises one or more compressor stages, and the turbine assembly comprises one or more turbine stages. A primary flow is compressed within the compressor stages, and the compressed air from the primary flow is then mixed with fuel and burned in the combustion chamber. The gases formed in the combustion chamber pass through the turbine assembly and finally exit through a nozzle whose cross-section allows these gases to be accelerated to generate propulsion. Each compressor and turbine stage comprises several annular rows of fixed and rotating blades. The fixed blades, known as distributors in a turbine or rectifiers in a compressor, direct the flow to the rotating blades. These rotating blades transmit the energy of the flow to a rotating shaft coaxial with the longitudinal axis.

[0011] As illustrated in Figure 1, which shows a prior art fixed-blade type component, each blade 10' extends radially between a tip end and a foot end and includes an upstream leading edge 102' and a downstream trailing edge 103'. Between the leading and trailing edges extend opposing intrados 101' and extrados 100' surfaces. The fixed blades 10' extend between two annular walls of the distributor, one inner and one outer, respectively. Such a turbine distributor is sectorized and comprises several distributor sectors arranged circumferentially end-to-end around the longitudinal axis. A sector generally contains several fixed blades.

[0012] In a high-pressure turbine, the fixed blades 10' are subjected to extreme temperatures, typically exceeding 600°C. They comprise a body 11', generally metallic, with a wall 12' enclosing a cavity 13' that can house a cooling system designed to circulate ventilation air within each blade. Each high-pressure turbine blade 10' thus includes an internal cavity and through holes 16' for ventilation air to pass from the internal cavity to the outside of the blade. These air passages form a thermal protection device 16' for the high-pressure turbine blades, designed to lower their temperature.However, although the high-pressure turbine blade wall protection system is fully operational, it does not allow for temperature homogenization on the wall 12' of the blade 10', and heat exchange may not be sufficient between the inner 14' and outer 15' faces of said wall 12'. Indeed, its function is conventionally limited to ensuring that the temperature does not exceed a certain threshold.

[0013] Like the fixed blades of high-pressure turbines, fan blades (not shown) incorporate thermal protection devices. However, fan blades are subject to the risk of frost or ice formation. The protection device for rotating blades is therefore designed to protect them from frost or ice buildup. There are anti-icing devices that prevent frost or ice from forming on the blade's surface, and de-icing devices that cyclically remove ice or frost from the surface. The de-icing device does not prevent frost or ice from forming but removes it after it has already formed. These thermal protection devices thus operate preventively on the fan blade to which they are attached, preventing its temperature from exceeding a certain threshold.However, these protective devices are not configured to homogenize the surface temperature of the blade walls or to promote heat exchange between the external environment and the blade.

[0014] However, for both fixed high-pressure turbine blades and fan blades, a lack of temperature uniformity across the surface can lead to a decrease in the performance of the protection systems themselves, because the required temperature regulation is too uneven across the entire surface. Blades with a metallic body are particularly affected by the problem of temperature uniformity, since they are generally made of a material that is thermally conductive enough to withstand variations in the engine environment (e.g., fixed high-pressure turbine blades) or the external environment (e.g., fan blades), but not thermally conductive enough to both take advantage of the temperature conditions provided by these environments and ensure a uniform temperature across the entire component.

[0015] US documents 8 915 058 B2, WO 2024 / 1 10140 A1, FR 3 130 754 A1, aircraft turbomachine parts with thermally conductive coatings.

[0016] The invention aims to overcome at least some of the aforementioned problems and proposes in this regard a blower blade having improved heat exchanges with its internal and / or external environment, as appropriate.

[0017] Summary of the invention

[0018] The invention proposes for this purpose a fan blade for an aircraft turbomachine comprising:

[0019] - a metallic body comprising at least one wall delimiting a cavity, the wall comprising an inner face situated opposite the cavity and an outer face opposite the inner face and exposed to an aerodynamic airflow,

[0020] - a thermal protection device for the blower blade, the thermal protection device being a frost protection device and being in contact with the wall, characterized in that the blower blade further comprises, at the level of the wall, a coating having a thermal conductivity greater than a thermal conductivity of the metallic body.

[0021] The blower blade according to the invention thus overcomes at least some of the aforementioned problems of the prior art. Indeed, in addition to the thermal protection device, it includes a coating having a thermal conductivity higher than that of the metallic body, which allows it to improve heat exchange and make better use of its environment. This is advantageous in several respects.

[0022] In some fan blades, the metal or metal alloy used for the body is chosen to meet specific mechanical strength requirements, which automatically limits the range of possible metals. However, the choice of metal or metal alloy dictates a certain thermal conductivity, as each metal or metal alloy has its own unique thermal conductivity.

[0023] The invention eliminates the need to modify the metal from which the metallic body is made to improve heat exchange. This function is entirely performed by the coating, thus maintaining the metallic body's good mechanical strength while simultaneously improving its thermal properties through the coating. The coating therefore functionalizes the wall, and consequently, the metallic body itself.

[0024] Improved heat exchange not only homogenizes the wall temperature but also allows the thermal protection device's performance to be linked to the surface temperatures regulated by the coating. Since the thermal protection device is in contact with the wall of the metallic body, it does not need to be adapted to the expected temperature gradient within the wall but can be identical across its entire surface.

[0025] Depending on various characteristics of the invention, which may be considered together or separately:

[0026] - the thermally conductive coating has a thickness of less than 500 pm;

[0027] - the thermally conductive coating has a thickness between 50 pm and 500 pm;

[0028] - the thermally conductive coating covers at least partially the outer face;

[0029] - the wall includes the thermal protection device, the thermally conductive coating covers the thermal protection device;

[0030] - the thermally conductive coating covers at least partially the outer face;

[0031] - the thermally conductive coating is made of a material chosen from graphene, aluminium, copper, nanotubes and a thermally conductive paint; - the metallic body is made of titanium or steel;

[0032] - the thermally conductive coating has a different color or tint than the color of the metallic body;

[0033] - the thermal protection device covers the entire external face, the thermally conductive coating covering the entire thermal protection device.

[0034] Brief description of the figures

[0035] Other objects, features and advantages of the invention will become clearer in the following description, made with reference to the accompanying figures, in which:

[0036] - Figure 1 is a schematic cross-sectional view illustrating a part (stator blade) according to the prior art;

[0037] - Figure 2 is a schematic view of a metallic body for a turbomachine part according to one embodiment of the invention;

[0038] - Figure 3 is a schematic cross-sectional view illustrating a thermally conductive coating covering an external face of a wall of a part (stator blade) according to an embodiment of the invention;

[0039] - Figure 4 is a schematic cross-sectional view illustrating a thermally conductive coating covering the thermal protection device of the part (stator blade) according to an embodiment of the invention;

[0040] - Figure 5 is a schematic cross-sectional view illustrating the part (stator blade) with a thermally conductive coating covering the outer face of the wall and the thermal protection device;

[0041] - Figure 6 is a schematic cross-sectional view illustrating a wall and a thermally conductive coating covering the inner face of the wall;

[0042] - Figure 7 is a schematic cross-sectional view illustrating a wall and a thermally conductive coating covering the inner and outer faces of the wall.

[0043] Detailed description of the invention With reference to Figures 2 to 7, the invention relates to a component 10 of an aircraft turbomachine. The component 10 can be any part of the turbomachine that is intended to exchange heat with its environment through its walls.

[0044] Generally, these types of parts are found in areas of the turbomachine that are exposed to extreme temperatures.

[0045] This can be the case, for example, with fixed high-pressure turbine blades (Figure 1). Under normal operating conditions, these blades are exposed to extreme temperatures exceeding approximately 600°C. Although equipped with an internal cooling system, fixed high-pressure turbine blades can benefit from heat exchange with their external environment to enhance cooling efficiency.

[0046] This can also be the case for components exposed to frost or ice formation, such as fan blades. Although dedicated protection systems are installed on fan blades, their effectiveness may be limited under extreme temperature conditions. Allowing fan blades to interact thermally with their external environment can improve frost protection effectiveness.

[0047] Other parts of the turbomachine can be prime candidates for exchanging heat with their local environment. This is the case, for example, with heat exchangers, nozzles, etc.

[0048] In both cases, the part 10 comprises a metallic body 10 including at least one wall 12 delimiting a cavity 13. As is better illustrated in Figure 2, the wall 12 includes an inner face 14, located opposite the cavity 13, and an outer face 15 opposite the inner face 14. The outer face 15 is intended to be exposed to an aerodynamic airflow F.

[0049] The metallic body 11 is advantageously made of a metal selected from titanium and steel. Indeed, titanium and steel have excellent mechanical strength, which is particularly suitable for turbomachine parts 10 that are subject to impacts or abrasion, such as those covered by the present invention. Impacts can result from collisions with birds or hail. Fan blades are typically exposed to this type of impact. The metallic body 11 can also be made of a metal alloy. For example, it can be made of an Inconel alloy (registered trademark), or of titanium and steel. The part 10 further includes a thermal protection device 16. This device is designed to protect the part 10 from excessive temperature variations. In this respect, the thermal protection device 16 is in contact with the wall 12.

[0050] In an embodiment not shown, part 10 is a blower blade, and the thermal protection device 16 is a frost protection device. The thermal protection device 16 may advantageously cover the entire external face 15 of the wall 12. However, it may also cover only part of the external face 15. By way of non-limiting example, the thermal protection device 16 may consist of a heating element capable of generating heat by resisting the flow of an electric current.

[0051] In another embodiment illustrated in Figures 3, 4, and 5, part 10 is a stator blade comprising an upper surface 100 and an lower surface 101 which are connected together at a leading edge 102 and a trailing edge 103 of the stator blade. The thermal protection device 16 may consist of a cooling system as illustrated in the figures.

[0052] At this point, it should be noted that in Figures 3, 4, and 5, part 10 is a solid stator blade. Cavity 13 contains thermal protection device 16 and is delimited by the inner face 14 of wall 12. Thus, in the aforementioned figures, the boundaries of cavity 13 and the inner face 14 of wall 12 appear to coincide. However, this is not the case, since the inner face 14 of wall 12 and the boundaries of cavity 13 do not overlap; rather, the inner face 14 surrounds cavity 13.

[0053] Alternatively, but not shown, the thermal protection device 16 may consist of air passage holes (not shown) extending from the inside of the stator blade to the outside. In this case, the air passage holes pass through the metal body 11 from the inner face 14 to the outer face 15 of the wall 12 of the stator blade. Preferably, the air passage holes extend over a portion of the metal body 11, preferably at least 20% of the metal body 11, which improves heat transfer from the inside to the outside of the stator blade when the turbomachine is operating.

[0054] The aforementioned thermal protection devices 16 are by no means limiting and other variants not mentioned are covered by the present invention.

[0055] According to the invention, the part 10 further comprises, at the level of the wall 12, a thermally conductive coating 20 having a thermal conductivity Δ2 greater than the thermal conductivity Δi of the metallic body 11. In other words, the thermally conductive coating 20 exhibits a better ability than the metallic body 11 to diffuse heat without displacing the material, thus improving heat exchange and making better use of its immediate environment. This is advantageous in several respects.

[0056] It should be emphasized that the thermally conductive coating 20 should not be confused with the thermal protection device 16. Indeed, the thermally conductive coating 20 and the thermal protection device 16 are distinct.

[0057] In certain parts 10, the metal or metal alloy from which the metal body 11 is made is chosen to meet constraints in terms of mechanical strength, which automatically limits the choice of possible metals. For example, as mentioned previously, the metal body 11 could be made of steel or titanium, which de facto dictates the thermal conductivity of the metal body 11.

[0058] Thanks to the thermally conductive coating 20, it is not necessary to modify the metal from which the metallic body 11 is made to improve heat exchange. Indeed, the improvement in heat exchange is entirely achieved by the thermally conductive coating 20, which allows the metallic body 11 to maintain good mechanical strength while improving the thermal properties of the part 10, particularly its metallic body 11. The coating 20 thus functionalizes the metallic body 11 via the wall 12 of said metallic body 11.

[0059] The improved heat exchange not only homogenizes the temperature of wall 12 but also allows the performance of the thermal protection device 16 to be linked to the surface temperatures regulated by the coating 20. Indeed, the thermal protection device 16 is in contact with at least one of the walls of the metallic body 11. The thermal protection device 16 does not need to be adapted according to the expected temperature gradient in wall 12 but can be identical regardless of its location on wall 12.

[0060] Furthermore, when part 10 is a fan blade, the use of a thermally conductive coating 20 such as the one described above reduces the overall mass of part 10 compared to a part 10 whose heat exchange enhancement function is performed by the metallic body 11. Indeed, the fan blade can be made more streamlined since the presence of the thermally conductive coating 20 reduces the required heat exchange surface area on the metallic body 11, without compromising the aerodynamic properties inherent to a fan blade. When part 10 is a heat exchanger, the use of the thermally conductive coating 20 reduces the overall size of part 10. In fact, in the case of a heat exchanger, the larger the effective surface area—that is, the surface area used for heat exchange—the greater the heat exchange.Heat exchangers are therefore very often bulky. Since the coating 20 facilitates heat exchange, the effective surface area of ​​the part 10 can be reduced. In this case, the effective surface area corresponds to the external face 15 of the wall 12 of the part 10.

[0061] When part 10 is a nozzle, the use of the thermally conductive coating 20 reduces the nozzle's maximum operating temperature, thereby limiting stresses due to thermal expansion. Because the walls are thinner, fewer rivets are required, improving durability. This also reduces the mass of part 10 compared to a part 10 without the coating 20.

[0062] Advantageously, the thermally conductive coating 20 has a thickness of less than 500 µm.

[0063] Thus, when the thermally conductive coating 20 is used on the external face 15 of the wall 12 of a turbomachine component 10 (e.g., Figure 3), it provides a thickness that allows it to have little or no impact on the aerodynamic profile of the external face 15, while maintaining optimized mechanical strength to resist abrasion and impacts from the external environment. This configuration is advantageous, for example, when the thermally conductive coating 20 is used on the external face 15 of a fan blade.

[0064] The same advantages are obtained when the thermally conductive coating 20 is directly applied to the thermal protection device 16, and the latter is directly applied to the external face 15 and exposed to the aerodynamic flow (not shown). In other words, in this configuration, the wall 12, the thermal protection device 16, and the thermally conductive coating 20 are stacked in that order.

[0065] As mentioned previously, the thermally conductive coating 20 can be used internally. This is the case, for example, when it coats the inner face 14 (Figure 6) or when it is applied around the thermal protection device 16 (Figures 4 and 5), i.e., when it covers the thermal protection device 16, and the latter is located inside the metallic body 11, particularly in the cavity 13. Such a configuration makes it possible both to limit the size of the thermally conductive coating 20 and to maintain sufficient mechanical strength.

[0066] The thermally conductive coating 20 can be used both internally, as previously mentioned, and externally on the outer face 15 of the wall 12 (Figure 7). This dual internal and external use of the thermally conductive coating 20 is particularly advantageous. Indeed, it allows for better temperature homogenization and / or improved heat exchange between the internal environment of the part 10 and its external environment. Such a coating 20 is particularly well-suited to parts 10 that are exposed to significant temperature variations from both their internal and external environments. This is the case, for example, with the first stators positioned behind the blower blade.

[0067] In practice, a thickness of less than 500 µm can be used when the thermally conductive coating is made of aluminum or copper. That said, the thermally conductive coating can more precisely have a thickness between 50 µm and 500 µm, preferably between 80 µm and 500 µm. Such a thickness range can be achieved when the thermally conductive coating is made of graphene, carbon nanotubes, or copper. The coating can also be made of a thermally conductive paint.

[0068] In this regard, the thermally conductive coating 20 can be applied using the cold spray technique when made of metal or metal alloys. It can be applied by inkjet printing when made of graphene or nanotubes. These techniques allow for a coating 20 that is both opaque and thin. However, other deposition techniques can be used to fully or partially coat the external face 15 of the wall 12 or the protective device 16.

[0069] As mentioned above, the thermally conductive coating 20 can cover the external face 15 of the wall 12 either completely or partially. The final choice rests with the manufacturer, depending on the intended use of the part 10, its configuration (part 10), particularly its geometric characteristics such as its shape and dimensions, the cost of the material(s) used for the thermally conductive coating 20, and so on. Naturally, the choice of location for the thermally conductive coating 20 on the part 10 also depends on the need to homogenize the temperature at that location.

[0070] When part 10 is a blower blade and the protective device 16 covers the entire external face 15, it is advantageous for the coating 20 to cover the entire thermal protection device 16, which allows for homogenization of the temperature and / or improved heat exchange over the entire surface of the thermal protection device 16.

[0071] When part 10 is a stator blade and the thermal protection device 16 consists of a plurality of through holes, as mentioned previously, it is advantageous for the coating 20 to cover the intrados 101 and the trailing edge 103, preferably between 60% and 70% of the stator blade.

[0072] Advantageously, the thermally conductive coating 20 has a different color or shade than the metallic body 11. Thus, areas no longer covered by the thermally conductive coating 20 appear a different color or shade than those covered by the coating 20. This difference in color or shade between the thermally conductive coating 20 and the metallic body 11 makes it possible to identify potential degradation or wear of the coating 20, and therefore that intervention is necessary to restore or replace said coating 20. It can be observed by an operator or by any detection tool known to those skilled in the art for the automated inspection of parts 10. Such a thermally conductive coating 20 is applicable to both blower blades and heating elements.

[0073] The thermally conductive coating 20 can be made of a material with improved abrasion resistance. For example, the thermally conductive coating 20 can be made of an abrasion-resistant steel such as Chemglaz (registered trademark) from the supplier Socomore. The thermally conductive coating 20 can also be made of polyurethane. It can also be made of elastomers.

[0074] The configurations shown in the cited figures are only possible examples, by no means limiting, of the invention which on the contrary encompasses the variants of forms and designs within the reach of the person skilled in the art.

Claims

DEMANDS 1. Fan blade (10) of an aircraft turbomachine comprising: - a metallic body (11) comprising at least one wall (12) delimiting a cavity (13), the wall (12) having an inner face (14) situated opposite the cavity (13), and an outer face (15) opposite the inner face (14) and exposed to an aerodynamic airflow (F), - a device (16) for thermal protection of the blower blade (10), the device (16) for thermal protection being a device (16) for protection against frost and being in contact with the wall (12), characterized in that the blower blade (10) further comprises, at the level of the wall (12), a thermally conductive coating (20) having a thermal conductivity A2 greater than a thermal conductivity Ai of the metallic body (11).

2. Blower blade (10) according to claim 1, wherein the coating (20) has a thickness of less than 500 µm.

3. Blower blade (10) according to any one of claims 1 or 2, wherein the thermally conductive coating (20) covers at least partially the outer face (15).

4. Blower blade (10) according to any one of claims 1 or 2, wherein the wall (12) includes the thermal protection device (16), the thermally conductive coating (20) covers the thermal protection device (16) and optionally covers at least partially the external face (15).

5. Blower blade (10) according to any one of claims 1 to 4, wherein the thermally conductive coating (20) is made of a material selected from graphene, aluminum, copper, nanotubes and a thermally conductive paint.

6. Blower blade (10) according to any one of claims 1 to 5, wherein the metallic body (11) is made of titanium (Ti), steel or titanium or steel alloy.

7. Blower blade (10) according to any one of claims 1 to 6, wherein the thermally conductive coating (20) has a color or tint different from the color of the metallic body (11).

8. Blower blade (10) according to any one of claims 3, 5 to 7, wherein the thermal protection device (16) covers the entire external face (15), the coating (20) covering the entire thermal protection device (16).

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