AIRCRAFT TURBOMACHINE PART FEATURING A THERMALLY CONDUCTIVE COATING THAT IMPROVES THE THERMAL CONDUCTIVITY OF A METALLIC BODY

Abstract

The invention relates to an aircraft turbomachine component (10) comprising: - a metallic body (11) including at least one wall (12) delimiting a cavity (13), the wall (12) having an inner face (14) located opposite the cavity (13), and an outer face (15) opposite the inner face (14) and exposed to an aerodynamic airflow (F), - a thermal protection device (16) for the component (10), the thermal protection device (16) being in contact with the wall (12), characterized in that the component (10) further comprises, at the level of the wall (12), a thermally conductive coating (20) having a thermal conductivity λ2 greater than a thermal conductivity λ1 of the metallic body (11). Figure for the abstract: Fig. 5

Description

Title of the invention: AIRCRAFT TURBOMACHINE PART COMPRISING A THERMALLY CONDUCTIVE COATING IMPROVING THE THERMAL CONDUCTIVITY OF A METALLIC BODY Technical field of the invention

[0001] The invention relates to the technical field of aircraft turbomachinery parts having a metallic body. The invention relates in particular to any part designed to exchange heat with its environment through its metallic walls. Technical background

[0002] A turbomachine, in particular 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.

[0003] The terms "upstream" and "downstream" are defined with respect to the direction of gas flow in the turbomachine.

[0004] The turbomachine includes a fan located upstream of the gas generator. The fan includes a rotor driven in rotation about its longitudinal axis by a fan shaft. The fan further includes blades extending radially from a disk.

[0005] Among blowers, there are enclosed blowers and unenclosed blowers, also known by the English expression "open rotor". Unlike enclosed blowers, the blades of unenclosed blowers are not surrounded by a blower housing, so they are particularly exposed to external conditions.

[0006] 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 a fuel and burned within the combustion chamber. The gases formed in the combustion chamber pass through the turbine assembly and finally escape through a nozzle whose cross-section allows these gases to be accelerated to generate propulsion.

[0007] The compressor and turbine stages each comprise several annular rows of fixed and rotating blades. The fixed blades 10' known as Distributors in a turbine or rectifiers in a compressor direct the flow towards the rotating blades. These blades transmit the energy of the flow to a rotating shaft coaxial with the longitudinal axis.

[0008] As illustrated in [Fig. 1] showing a prior art part of the fixed-blade type, each blade 10' extends radially between a tip end and a foot end and comprises upstream a leading edge 102' and downstream a 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, respectively internal and external. Such a turbine distributor is sectorized and comprises several distributor sectors arranged circumferentially end-to-end around the longitudinal axis. A sector generally comprises several fixed blades.

[0009] 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, including a wall 12' delimiting a cavity 13' which can house a cooling system adapted to circulate ventilation air inside each blade. Each high-pressure turbine blade 10' thus comprises an internal cavity and through holes 16' for ventilation air passage from the internal cavity to the outside of the blade. In this way, the air passage holes form a thermal protection device 16' for the high-pressure turbine blades, designed to lower the temperature of said blades.However, although the high-pressure turbine blade wall protection system is fully operational, it does not allow for temperature homogenization on the 12' wall of the 10' blade, 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.

[0010] Like the fixed blades of high-pressure turbines, fan blades (not shown) or vanes 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 formation. There are anti-icing devices designed to prevent frost or ice from forming on the part's surface, and de-icing devices whose function is to cyclically detach the ice or frost from the part's surface. The de-icing device does not prevent the formation of frost or ice but allows for the removal of frost or ice after it has formed.

[0011] These thermal protection devices therefore operate preventively on the blower blade to which they are associated to prevent its temperature from exceeding a certain threshold. However, these protection devices are not not configured to homogenize the surface temperature of the turbine blade walls nor to promote heat exchange between the external environment and the turbine blade.

[0012] However, for both fixed high-pressure turbine blades and fan blades, a lack of temperature homogenization on the surface of the walls can lead to a decrease in the performance of the protection systems themselves because the regulation required is too heterogeneous across the entire surface. Blades with a metallic body are particularly affected by the problem of temperature homogenization 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 brought about by these environments and ensure that the temperature is homogeneous throughout the entire part.

[0013] The invention aims to overcome at least some of the aforementioned problems and, in this regard, proposes a part having improved heat exchange with its internal and / or external environment, as the case may be. Summary of the invention

[0014] The invention proposes for this purpose an aircraft turbomachine part comprising: - a metallic body comprising at least one wall delimiting a cavity, the wall comprising an inner face located opposite the cavity and an outer face opposite the inner face and exposed to an aerodynamic airflow, - a thermal protection device for the part, the thermal protection device being in contact with the wall, characterized in that the part also comprises, at the level of the wall, a coating having a thermal conductivity greater than a thermal conductivity of the metallic body.

[0015] The part according to the invention thus makes it possible to overcome 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 to make better use of its environment. This is advantageous in several respects.

[0016] In certain parts, the metal or metal alloy from which the metal body is made is chosen to meet constraints in terms of mechanical strength, which automatically limits the choice of possible metals. However, the choice of the metal or alloy Metallic imposes a certain thermal conductivity since each metal or metal alloy has its own specific thermal conductivity.

[0017] The invention makes it possible to avoid modifying the metal from which the metallic body is made in order to improve heat exchange. This function is entirely performed by the coating, which allows the metallic body to maintain good mechanical strength while improving its thermal properties through the coating. The coating thus functionalizes the wall, and thereby the metallic body.

[0018] Improved heat exchange not only homogenizes the wall temperature but also allows the performance of the thermal protection device to be linked to the surface temperatures regulated by the coating. Indeed, the thermal protection device is in contact with the wall of the metallic body. The thermal protection device does not need to be adapted according to the expected temperature gradient in the wall but can be identical across the entire wall.

[0019] According to various features of the invention which may be taken together or separately: • the thermally conductive coating has a thickness of less than 500 pm; • the thermally conductive coating has a thickness between 50 pm and 500 pm; • the thermally conductive coating covers at least partially the outer face; • the wall includes the thermal protection device, the thermally conductive coating covers the thermal protection device; • the thermally conductive coating covers at least partially the outer face; • the thermally conductive coating is made of a material chosen from graphene, aluminium, copper, nanotubes and a thermally conductive paint; • the metal body is made of titanium or steel; • the thermally conductive coating has a different color or tint than the color of the metallic body; • the part is a blower blade, the thermal protection device is a thermal protection device against frost covering the entire external face, the thermal conductive coating covering the entire thermal protection device; • the part is a stator blade, the stator blade having an upper surface and an lower surface which are connected together at a leading edge and a trailing edge of the stator blade, the thermal protection device being air passage holes from the inside of the stator blade to the outside, the thermally conductive coating covering the lower surface and the trailing edge; • the thermally conductive coating covers between 60% and 70% of the stator blade; • the thermally conductive coating covers at least partially the inner face. Brief description of the figures

[0020] Other objects, features and advantages of the invention will become more apparent in the following description, made with reference to the accompanying figures, in which:

[0021] - [Fig.1] is a schematic cross-sectional view illustrating a part (stator blade) according to the prior art;

[0022] - [Fig. 2] is a schematic view of a metallic body for a part of turbomachine according to an embodiment of the invention;

[0023] - [Fig. 3] is a schematic cross-sectional view illustrating a conductive coating thermal covering an external face of a wall of a part (stator blade) according to an embodiment of the invention;

[0024] - [Fig. 4] is a schematic cross-sectional view illustrating a conductive coating thermal covering the thermal protection device of the part (stator blade) according to an embodiment of the invention;

[0025] - [Fig.5] is a schematic cross-sectional view illustrating the part (stator blade) with a thermally conductive coating covering the external face of the wall and the thermal protection device;

[0026] - [Fig. 6] is a schematic cross-sectional view illustrating a wall and a coating thermal conductor covering the inner face of the wall;

[0027] - [Fig. 7] is a schematic cross-sectional view illustrating a wall and a coating thermal conductor covering the inner and outer faces of the wall. Detailed description of the invention

[0028] With reference to Figures 2 to 7, the invention relates to a part 10 of an aircraft turbomachine. The part 10 can be any part of the turbomachine that is intended to exchange heat with its environment through its walls.

[0029] Generally, this type of part is found in areas of the turbomachine that are exposed to extreme temperatures.

[0030] This can be the case, for example, with fixed high-pressure turbine blades ([Fig. 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 may benefit from heat exchange with their external environment to enhance cooling efficiency.

[0031] This can also be the case for parts that are exposed to frost or ice formation, such as fan blades. Although dedicated protection systems are installed on fan blades, the protection effectiveness may be limited under extreme temperature conditions. It may be useful to allow fan blades to interact thermally with their external environment to improve the effectiveness of frost protection.

[0032] Other parts of the turbomachine may be prime candidates for exchanging with their local environment. This is the case, for example, with heat exchangers, nozzles, etc.

[0033] In one case as in the others, the part 10 comprises a metallic body 10 including at least one wall 12 delimiting a cavity 13. As is better illustrated in [Fig.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.

[0034] The metal 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 likely to receive impacts or be exposed to abrasion, such as those covered by the present invention. Impacts can result from collisions of the part with birds or hail. Fan blades are typically exposed to this type of impact. The metal 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.

[0035] Part 10 further includes a thermal protection device 16. This device is intended to protect part 10 from excessive temperature variations. In this respect, the thermal protection device 16 is in contact with the wall 12.

[0036] 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 only partially cover the external face 15. By way of non-limiting example, the protection device 16 thermal can consist of a heating element capable of generating heat by resisting the flow of an electric current.

[0037] In another embodiment illustrated in Figures 3, 4 and 5, the 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.

[0038] At this stage, 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 limits 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 limits of cavity 13 do not overlap, but rather the inner face 14 surrounds cavity 13.

[0039] 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 over 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 in operation.

[0040] The aforementioned thermal protection devices 16 are by no means limiting and other variants not mentioned are covered by the present invention.

[0041] 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 X2 greater than the thermal conductivity Xi of the metallic body 11. In other words, the thermally conductive coating 20 has a better ability than the metallic body 11 to diffuse heat without displacing the material, which allows it to improve heat exchange and make better use of its immediate environment. This is advantageous in several respects.

[0042] 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.

[0043] 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.

[0044] 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 makes it possible to maintain the metallic body 11's 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 through the wall 12 of said metallic body 11.

[0045] The improved heat exchange not only homogenizes the temperature of the wall 12 but also allows the performance of the thermal protection device 16 to be controlled by 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 the wall 12 but can be identical regardless of its location on the wall 12.

[0046] Furthermore, when the part 10 is a fan blade, the use of a thermally conductive coating 20 such as that described above makes it possible to reduce the overall mass of the part 10 compared to a part 10 whose heat exchange enhancement function would be performed by the metallic body 11. Indeed, the fan blade can be made more streamlined since the presence of the thermally conductive coating 20 makes it possible to reduce the required heat exchange surface area on the metallic body 11, without compromising the aerodynamic properties inherent to a fan blade.

[0047] When part 10 is a heat exchanger, the use of the thermally conductive coating 20 reduces the overall size of part 10. Indeed, in the case of a heat exchanger, the larger the effective surface area—that is, the surface area intended for heat exchange—the greater the number of heat exchanges. Heat exchangers are therefore often quite bulky. Since the coating 20 facilitates heat exchange, the effective surface area of ​​part 10 can be reduced. In this case, the effective surface area corresponds to the external face 15 of the wall 12 of part 10.

[0048] When part 10 is a nozzle, the use of the thermally conductive coating 20 reduces the maximum operating temperature of the nozzle, thereby limiting stresses due to thermal expansion. Since the walls are thinner, there are fewer rivets, which improves durability. This also reduces the mass of part 10 compared to a part 10 without the coating 20.

[0049] Advantageously, the thermally conductive coating 20 has a thickness of less than 500 pm.

[0050] 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., [Fig. 3]), it provides a thickness that allows it to have little or no alteration to 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.

[0051] The same advantages are obtained when the thermally conductive coating 20 is directly affixed to the thermal protection device 16, and the latter is directly affixed 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 form a stack in that order.

[0052] 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 ([Fig. 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.

[0053] The thermally conductive coating 20 can be used both internally, as previously mentioned, and externally on the outer face 15 of the wall 12 ([Fig. 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 suitable for parts 10 that are exposed to significant temperature variations from both their internal and external environments. This is, for example, the case for the first stators positioned behind the blower blade.

[0054] In practice, a thickness of less than 500 µm can be used when the thermally conductive coating 20 is made of aluminum or copper. That being said, the thermally conductive coating 20 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 20 is made of graphene, carbon nanotubes, or copper. The coating 20 can also be made of a thermally conductive paint.

[0055] In this regard, the thermally conductive coating 20 can be applied using the Cold Spray technique when it is made of metal or metal alloys. It It can be applied by inkjet printing when it is 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.

[0056] As indicated above, the thermally conductive coating 20 can cover the external face 15 of the wall 12 completely or partially. The final choice rests with the manufacturer, depending on the intended use of the part 10, the configuration of the part 10, in particular its geometric characteristics such as its shape and dimensions, the cost of the material(s) used for the thermally conductive coating 20, etc. 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 on the part 10.

[0057] When the 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 makes it possible to homogenize the temperature and / or improve heat exchange over the entire surface of the thermal protection device 16.

[0058] When the 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.

[0059] 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 inspecting parts 10 in an automated manner. Such a thermally conductive coating 20 is applicable to both blower blades and heating elements.

[0060] 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.

[0061] The configurations shown in the cited figures are only possible examples, by no means limiting, of the invention which on the contrary encompasses variants of forms and designs within the reach of a person skilled in the art.

Claims

Demands

1. Aircraft turbomachine part (10) comprising: - a metallic body (11) including at least one wall (12) delimiting a cavity (13), the wall (12) having an inner face (14) located opposite the cavity (13), and an outer face (15) opposite the inner face (14) and exposed to an aerodynamic airflow (F), - a thermal protection device (16) for the part (10), the thermal protection device (16) being in contact with the wall (12), characterized in that the part (10) further comprises, at the level of the wall (12), a thermally conductive coating (20) having a thermal conductivity X2 greater than a thermal conductivity Xi of the metallic body (11).

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

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

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

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

8. Part (10) according to any one of claims 3, 5 to 7, part (10) being a blower blade, the thermal protection device (16) being a frost protection device covering the entire external face (15), the coating (20) covering the entire thermal protection device (16).

9. Part (10) according to any one of claims 3 to 7, part (10) being a stator blade, the stator blade having 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) being air passage holes from the inside of the stator blade to the outside, the coating (20) covering the lower surface (101) and the trailing edge (103), preferably between 60% and 70% of the stator blade.

10. Part (10) according to any one of claims 1 or 2, wherein the thermally conductive coating (20) covers at least partially the inner face (14).

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