Turbomachine blade having a reinforced leading edge

Abstract

The invention relates to a turbomachine blade comprising a blade root portion (4) and a blade body portion (5), the blade body portion comprising a core (10) made of ceramic matrix composite material covered with an environmental barrier (11), the blade being characterized in that the thickness (e) of the environmental barrier on the blade body portion is greater than or equal to 1.0 mm on the leading edge (3) of the blade.

Description

Description Title of the invention: Turbomachine blade with reinforced leading edge Technical Field

[0001] This presentation concerns an aeronautical turbomachine blade made of ceramic matrix composite material and a manufacturing process for such a blade. Previous technique

[0002] Ceramic matrix composite (CMC) materials can withstand temperatures ranging from 600°C to 1400°C.

[0003] Due to their superior resistance to high temperatures, CMC materials require less cooling. Since this cooling is traditionally drawn from the compressor, impacting turbomachine efficiency, CMC materials improve engine efficiency, thereby reducing fuel consumption.

[0004] Furthermore, their use helps to optimize the performance of turbomachines, particularly by reducing the overall mass of the turbomachine, which further contributes to a decrease in fuel consumption and therefore to a significant reduction in polluting emissions.

[0005] These advantages explain the industrial interest in developing such ceramic matrix composite materials.

[0006] However, CMCs present other challenges before industrial use in an aeronautical turbomachine and in particular in turbomachine blades.

[0007] In particular, compared to the metallic alloys they replace, ceramic matrix composite materials are less impact resistant.

[0008] Furthermore, CMC blades have less resistance to the physico-chemical environment of a turbomachine compared to metallic alloys.

[0009] And finally, blades made of CMC materials are difficult to machine.

[0010] It should be noted, however, that there are solutions to each of the problems taken independently.

[0011] For example, it has been proposed to add a metallic flashing to the leading edge of a blade made of composite material to protect it from a possible impact.

[0012] Similarly, it has been proposed to coat CMC blades with an environmental barrier that chemically protects the blade against corrosion and / or very high temperatures.

[0013] Finally, manufacturing methods for CMC blades known as "near net shape" are proposed, meaning that after preparation, the blades have a shape as close as possible to the desired shape for their intended use. The machining requirements for these blades are then strictly reduced to a minimum, significantly accelerating the manufacturing process.

[0014] However, it remains complicated and costly to overcome the three problems outlined above using specific methods for each of said problems. Description of the invention

[0015] The present invention specifically aims at a blade made of ceramic matrix composite material which would solve the three problems mentioned above in a unique way.

[0016] For this purpose, it relates, according to a first of its aspects, to a turbomachine blade comprising a part of the blade root and a part of the blade body, the part of the blade body comprising a core of ceramic matrix composite material covered with an environmental barrier, the blade being characterized in that the thickness of the environmental barrier on the part of the blade body is greater than or equal to 1.0 mm on the leading edge of the blade.

[0017] It will be appreciated if, in the application, the "thickness" of a layer is understood in its usual sense, as the smallest dimension of extension. Generally, this dimension is obtained in the direction perpendicular to the surface of the composite core material.

[0018] In one aspect of the invention, the environmental barrier layer provides excellent protection of the underlying CMC against oxidation and corrosion, similar to environmental barriers in the prior art.

[0019] Furthermore, the environmental barrier thickness provides excellent protection for the blade's leading edge against foreign body impacts. Indeed, the inventors observed that for an environmental barrier thickness of 1.0 mm or greater, only the environmental barrier itself is damaged upon impact, and that it also dissipates all of the impact energy within the environmental barrier layer. The fragile nature of the environmental barrier is thus used to dissipate all of the impact energy, ensuring that The environmental barrier layer protects the underlying substrate and ensures that the ceramic matrix composite portion of the blade is not damaged by impact.

[0020] Furthermore, if an environmental barrier layer is damaged upon impact, it is relatively easy to remove, especially at such thick environmental barrier layers. It is also significantly less expensive to apply a new environmental barrier to the surface of a turbine blade than to repair or replace the composite core of such a blade.

[0021] This allows us to manufacture blades that are much less expensive than those of the previous art, and which also do not need to be replaced if they suffer an impact.

[0022] The causes of such an impact on a turbomachine in operation can be, for example, the ingestion of a volatile by said turbomachine.

[0023] In a blade of the invention, the ceramic matrix composite material forms the core of the blade, that is to say it ensures the mechanical properties and excellent grip of the environmental barrier, but it does not play an aerodynamic role.

[0024] In a blade according to the invention, it is indeed the environmental barrier that ensures the aerodynamic role of the blade.

[0025] This results in a greatly simplified production of the blade because the machining to obtain the desired aerodynamic profile is carried out in the environmental barrier, and not in the CMC material.

[0026] In particular, all the efforts usually required to obtain a surface finish of the CMC material smooth enough for the aerodynamic requirements of a turbomachine blade can be saved here because the CMC material is present only as the core of the blade and it is at the environmental barrier, for which machining is simpler to meet this need.

[0027] Machining the environmental barrier is much simpler than machining a ceramic matrix composite material because it is much less hard than a CMC material.

[0028] Thus, the invention makes it possible to protect the leading edge of a composite material blade against impacts with a simpler solution than those proposed in the prior art which required attaching a metallic shim to a composite material blade.

[0029] In one embodiment, the turbomachine blade according to the invention comprises a blade root portion and a blade body portion, the blade body portion comprising a core of ceramic matrix composite material covered with an environmental barrier, the blade being characterized in that the thickness of the environmental barrier on the blade body portion is greater than or equal to 1.0 mm on the leading edge of the blade, in that the thickness of the environmental barrier decreases continuously between the leading edge and the trailing edge and in that the thickness of the environmental barrier is less than or equal to 40 pm for the trailing edge.

[0030] The expression "decreases continuously" should be understood in its mathematical sense. The function representing the thickness of the environmental barrier as a function of distance from the leading edge is continuous and decreasing.

[0031] In one embodiment, the thickness of the environmental barrier can decrease strictly and continuously between the leading edge and the trailing edge.

[0032] One advantage of such a blade is that the trailing edge of the blade remains as thin as those of earlier blades, because the thickness of the environmental barrier is very small, which is very advantageous for aerodynamic reasons.

[0033] Such a blade thus combines excellent protection of the blade core thanks to the very large thickness of the environmental barrier covering the leading edge and also presents excellent aerodynamic characteristics since the environmental barrier is very thin for the trailing edge.

[0034] In one embodiment, the thickness of the environmental barrier for the trailing edge can be between 20 pm and 40 pm.

[0035] In one embodiment, the thickness of the environmental barrier in the blade foot portion is less than or equal to 100 pm.

[0036] Indeed, since the blade foot part is not subject to impacts nor does it require special machining for aerodynamic reasons, there is no need for the environmental barrier to be thicker than for blades of the previous art.

[0037] In one embodiment, the environmental barrier comprises silicon, for example, a rare-earth silicate or mullite. For example, the environmental barrier may comprise yttrium disilicate Y2Si2O7, ytterbium disilicate Yb2Si2O7, mullite (3Al2O3.2SiO2), or a mixture of two or more of these compounds.

[0038] In one embodiment, the blade further comprises a bonding layer disposed between the ceramic matrix composite material core and the environmental barrier.

[0039] In one embodiment, the bonding layer may comprise silicon and / or silica SiO2, or may even be made of silica SiO2.

[0040] Such a bonding layer ensures excellent chemical continuity between the thermal barrier and the CMC material. Furthermore, this bonding layer provides excellent compatibility in terms of thermal expansion between the CMC material and the thermal barrier, thus reducing the risk of delamination of the environmental barrier during operation.

[0041] In one embodiment, the blade is chosen from a fixed blade, for example a blade of a high-pressure distributor or a blade of a low-pressure distributor, or a moving blade, for example a high-pressure turbine blade or a low-pressure turbine blade.

[0042] In one embodiment, the blade is a movable blade. Indeed, it is for these blades that the risk of fracture in case of impact is most pronounced, and it is therefore for these blades that it is particularly desirable to obtain the advantages described above.

[0043] In one embodiment, the blade includes a lower connecting portion between the blade foot portion and the blade body portion in which the thickness of the environmental barrier is strictly increasing.

[0044] This connecting portion ensures excellent mechanical continuity between the ceramic matrix composite material parts of the blade body and the blade foot.

[0045] In particular, this avoids sudden variations in the thickness of the composite material parts, which avoids areas of stress accumulation, and therefore reduces the overall fragility of the blade.

[0046] Preferably, such a connecting portion has an extension dimension less than or equal to 10 mm in the longitudinal direction of the blade, for example between 3.0 mm and 10 mm.

[0047] Limiting the longitudinal dimension of the lower connection portion, where the environmental barrier thickness is less than that of the blade body, ensures the preserving the aforementioned advantages obtained precisely through the thickness of the environmental barrier, while avoiding areas of stress accumulation.

[0048] The longitudinal direction of the blade is understood as the direction of greatest extension of the blade, and generally the direction which extends from the blade foot towards the blade body.

[0049] In an embodiment where the blade is a fixed blade, the blade may further include a portion of blade head having an environmental barrier thickness less than or equal to 100 pm.

[0050] Indeed, for the same reasons as those described for the blade foot part, it is not necessary for the environmental barrier thickness to be thicker than for conventional blades.

[0051] In an embodiment where the blade is a fixed blade, the blade may include a portion of blade head and further include an upper connecting portion between the part of blade head and the part of blade body in which the thickness of the environmental barrier is strictly increasing.

[0052] This upper connection section allows the same advantages to be obtained at the blade head as those described above for the lower connection section.

[0053] Preferably, such an upper connecting portion has an extension dimension less than or equal to 10 mm in the vertical direction of the blade, for example between 3.0 mm and 10 mm.

[0054] Limiting the longitudinal dimension of the upper connecting portion allows us to obtain at the blade head the same advantages as those described above for the lower connecting portion.

[0055] In one embodiment, the ceramic matrix composite material is a SiC / SiC material.

[0056] According to another aspect, the invention relates to a method for manufacturing a blade as described above, the method comprising a step of depositing an environmental barrier layer on a ceramic matrix composite material core, followed by a step of machining the environmental barrier layer.

[0057] In one embodiment, the process includes, before the step of depositing an environmental barrier layer, a step of depositing an adhesion layer on the core of ceramic matrix composite material.

[0058] In one embodiment, the bonding layer comprises silicon and / or silica SiO2, and the bonding layer deposition step can be carried out by physical vapor deposition (PVD), chemical vapor deposition (CVD), vacuum plasma spraying (VPS), or atmospheric plasma spraying (APS).

[0059] In one embodiment, the environmental barrier can be deposited by thermal projection, for example by plasma projection.

[0060] It should be noted that these methods differ from the liquid-based depositions usually envisaged in the prior art for the deposition of an environmental barrier.

[0061] Indeed, these liquid-based methods are not suitable for depositing thicknesses that conform to those of a described blade.

[0062] This is why a plasma projection application of the environmental barrier is preferred, as it is compatible with the thicknesses involved.

[0063] While thermal spray deposition techniques are less precise than prior art methods, they allow for the deposition of significant thicknesses of environmental barrier, and the barrier can be machined. The subsequent machining step corrects any inaccuracies from the deposition stage, which is why these less expensive deposition techniques, capable of depositing greater thicknesses of the environmental barrier layer, can be chosen.

[0064] In one embodiment, the machining step can be carried out by single-layer or multi-layer grinding.

[0065] According to another aspect, the invention relates to a turbomachine comprising a blade as described above.

[0066] According to another aspect, the invention relates to an aircraft comprising a turbomachine as described above. Brief description of the drawings

[0067] [Fig. 1] Figure 1 is a schematic representation of a turbomachine.

[0068] [Fig. 2] Figure 2 is a schematic representation of an earlier art dawn.

[0069] [Fig. 3] Figure 3 schematically represents a blade in one embodiment of the invention.

[0070] [Fig. 4] Figure 4 schematically represents a portion of a connection in one embodiment of the invention.

[0071] [Fig. 5] Figure 5 schematically represents a stacking for obtaining a blade according to the invention. Description of the implementation methods

[0072] The invention is now described by means of figures, which are provided for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0073] Figure 1 represents, in cross-section along a vertical plane passing through its main axis A, a turbofan engine 21. It comprises, from upstream to downstream along the airflow circulation, a fan 22, a low-pressure compressor 23, a high-pressure compressor 24, a combustion chamber 25, a high-pressure turbine 26, and a low-pressure turbine 27.

[0074] As is known, the low pressure compressor 23, the high pressure compressor 24, the high pressure turbine 26, and the low pressure turbine TJ comprise fixed blades and moving blades, one or more of which may be as described above.

[0075] Figure 2 illustrates a blade 1 made of ceramic matrix composite material according to the prior art.

[0076] Such a blade 1 comprises a blade body part 5 and a blade foot part 4.

[0077] This blade comprises a leading edge 3 and a trailing edge 7. As shown, the leading edge 3 is reinforced by a metallic shim 8 arranged on it.

[0078] The metal flashing 8 provides mechanical protection to the leading edge of the blade. In the event of an object being ingested by the engine, it is the metal flashing that will come into contact with said object and not the body of the blade 5.

[0079] Thus, the blade 1 is protected by the flashing 8. However, such blades have disadvantages, particularly related to the arrangement of the flashing 8 on the blade 1.

[0080] In particular, the difference in coefficients of thermal expansion between blade 1 and shim 8 makes it difficult to hold shim 8 on blade 5.

[0081] A blade according to the invention offers an alternative way of protecting the leading edge, which also ensures protection of the CMC material against the corrosive and oxidizing environment of the turbomachine.

[0082] Figure 2 further illustrates the transverse direction T and longitudinal direction L of a blade.

[0083] In addition, figure 2 illustrates in dotted line III the cross-section of the view of figure 3, and in dotted line IV, the position of the view of figure 4.

[0084] However, it should be noted that these indications are only for reference purposes, since figures 3 and 4 relate to blades according to the invention, while figure 2 is a prior art blade outside the invention.

[0085] Figure 3 illustrates a particular cross-section of a blade according to the invention.

[0086] As described above, the dawn in Figure 3 comprises a ceramic matrix composite material core 10 and an environmental barrier 11.

[0087] Figure 3 further illustrates what is meant by the thickness of the environmental barrier.

[0088] For this purpose, the thickness ei, e2, e3, e4 is indicated at several points more or less close to the leading edge 3, ei being the closest to the leading edge 3 and e4 the furthest away.

[0089] In the embodiment shown in Figure 3, the thickness of the environmental barrier 11 in a blade of the invention decreases between the leading edge 3 and the trailing edge 4.

[0090] As mentioned above, the thickness e4 of the environmental barrier 11 at the leading edge 3 is greater than or equal to 1.0 mm.

[0091] Finally, Figure 3 illustrates that the thickness variation is continuous. This ensures excellent aerodynamic properties for the entire blade assembly.

[0092] Furthermore, it is important to understand that the variation in thickness is assessed independently on the intrados and extrados. Indeed, as is also shown in Figure 3, the thickness of the environmental barrier 11 can be different for the intrados and extrados.

[0093] However, whether we look at the thickness of the environmental barrier 11 on the intrados or that on the extrados, this thickness decreases between the leading edge 3 and the trailing edge 4.

[0094] In an embodiment not shown, the environmental barrier thickness can be constant and greater than or equal to 1.0 mm over the entire blade body portion.

[0095] Figure 4 illustrates what is meant by connecting portion 6. Such a connecting portion is located between the blade root zone 4 and the blade body zone 5.

[0096] As shown in Figure 4, the connecting portion 6 includes a thickness e of environmental barrier 11 which gradually increases in the connecting portion 6.

[0097] Figure 4 further illustrates what is meant by the H extension R of the connecting portion 6 in the longitudinal direction.

[0098] In one embodiment, the H extension R of the connecting portion 6 is less than or equal to 10 mm, for example between 3.0 mm and 10 mm.

[0099] The connecting portion ensures excellent compatibility between the CMC portions of the blade body 5 and the blade foot portion 4, while allowing the desired thickness to be achieved quickly.

[0100] Figure 5 finally illustrates a stack of a ceramic matrix composite material core 10, a bonding layer 110 and an environmental barrier 11.

[0101] In one embodiment it is possible to place an adhesion layer 110 between the substrate 10 and the environmental barrier 11.

[0102] This embodiment allows the stack to exhibit better resistance to delamination, notably by improving continuity in terms of coefficients of thermal expansion.

[0103] In addition, the 110 bonding layer can play a role in protecting the 10 composite material substrate against corrosion.

[0104] In one embodiment, the blade does not include any layers other than the ceramic matrix composite material core 10, the tack layer 110 and the environmental barrier 11.

[0105] In other words, the bonding layer 110 is disposed directly in contact with the ceramic matrix composite core 10, and the environmental barrier layer 11 is disposed directly in contact with the bonding layer 110.

Claims

Claims

1. A turbomachine blade comprising a blade root portion (4) and a blade body portion (5), the blade body portion comprising a core (10) of ceramic matrix composite material covered with an environmental barrier (11), the blade being characterized in that the thickness (e) of the environmental barrier on the blade body portion is greater than or equal to 1.0 mm on the leading edge (3) of the blade.

2. A turbomachine blade according to claim 1, wherein the thickness of the environmental barrier decreases continuously between the leading edge and the trailing edge and wherein the environmental barrier thickness is less than or equal to 40 μm for the trailing edge (8).

3. A turbomachine blade according to claim 1 or 2, wherein the thickness of the environmental barrier (11) in the blade root portion (4) is less than or equal to 100 μm.

4. A turbomachine blade according to any one of claims 1 to 3, wherein the environmental barrier (11) comprises yttrium disilicate Y2Si2O7, ytterbium disilicate Yb2Si2O7, mullite, (3AI2O3.2SiO2) or a mixture of two or more of these compounds.

5. Turbomachine blade according to one of claims 1 to 4, in which a bonding layer (110) is arranged between the core (10) made of ceramic matrix composite material and the environmental barrier (11).

6. Turbomachine blade according to claim 5, in which the adhesion layer (110) comprises silicon and / or silica SiO2.

7. A turbomachine blade according to one of claims 1 to 6, which is chosen from a high-pressure nozzle blade, a low-pressure nozzle blade, a high-pressure turbine blade or a low-pressure turbine blade.

8. A turbomachine blade according to one of claims 1 to 7, further comprising a lower connecting portion (6) between the blade root portion (4) and the blade body portion (5) in which the thickness (e) of the environmental barrier (11) is strictly increasing.

9. Method of manufacturing a blade according to one of claims 1 to 8 comprising a step of depositing an environmental barrier layer (11) on a core made of ceramic matrix composite material (10), followed by a step of machining the environmental barrier layer.

10. Manufacturing method according to claim 9, wherein the step of depositing the environmental barrier (11) is carried out by plasma spraying.

11. Manufacturing method according to claim 9 or 10, which comprises, before the step of depositing an environmental barrier layer (11), a step of depositing a bonding layer (110) on the core of ceramic matrix composite material (10).

12. Aeronautical turbomachine comprising a blade according to one of claims 1 to 8.

13. Aircraft comprising an aeronautical turbomachine according to claim 12.

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