METHOD FOR MANUFACTURING A HOLLOW BLADE

Abstract

The invention relates to a method for manufacturing a blade (8) comprising the following steps: (d) drilling the outer wall of the blade (8) by electrical discharge machining (EDM) to form cooling channels (17), characterized in that: - in step (a), the blade (8') comprises cooling slots (16) extending from the inner wall (13) to the outer wall, each slot having a first end (16a) opening into the inner cavity (14) and a second end (16b) located between the inner wall (13) and the outer wall, and - in step (d), each drilling is carried out from the outer wall to the second end (16b) of each cooling slot (16) such that each cooling channel (17) opens respectively into a cooling slot (16). Abstract figure: Figure 15

Description

Title of the invention: METHOD FOR MANUFACTURED A HOLLOW BLADE Technical field of the invention

[0001] The invention relates to the field of manufacturing processes for hollow blades for turbomachinery, particularly aircraft.

[0002] The invention relates particularly to the field of manufacturing processes for hollow blades, comprising a drilling step by machining by electro-erosion, also known by the English acronym EDM (for "electrical discharge machining"). Technical background

[0003] An aircraft turbomachine, such as a turbojet, typically comprises, from upstream to downstream in the direction of gas flow, a movable fan rotating about a longitudinal axis, a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine, a low-pressure turbine and a gas exhaust nozzle.

[0004] The blower allows the intake of an airflow that splits into a primary flow and a secondary flow. The primary flow passes through a primary channel of the turbomachine while the secondary flow is directed towards a secondary channel surrounding the primary channel.

[0005] The primary flow is compressed within the compressors. The compressed air is then mixed with a fuel and burned within the combustion chamber. The gases from the combustion pass through the turbines and then escape through the nozzle, the cross-section of which allows these gases to be accelerated to generate propulsion.

[0006] Turbines are typically equipped with blades regularly spaced around a rotating wheel about its longitudinal axis. A blade extends radially between a root and a tip. A blade also includes a blade connected to the root by a platform, for example. The blade has an aerodynamic shape and typically comprises an outer face including an intrados and an extrados connected by a leading edge and a trailing edge.

[0007] Since high-pressure turbine blades are located downstream of the combustion chamber, they are subjected to high temperatures. Therefore, these blades are typically made of metallic or composite materials, particularly ceramic matrix composites (CMCs). These materials have the advantage of withstanding high temperatures. However, such blades may be subjected to temperatures exceeding those that metallic or ceramic matrix composite materials can withstand.

[0008] In this context, it has been proposed to equip the blades with a cooling system. The cooling system comprises a cooling circuit arranged inside the blades, allowing air from the compressors to pass through them. The cooling circuit includes internal cavities delimited by an inner wall of the blade, which provide internal cooling of the blades. Furthermore, it has been proposed to drill through the outer wall of the blades to create cooling passages opening into the internal cavities, thereby creating an air film around the blade and optimizing blade cooling.

[0009] The passages are typically made by electrical discharge machining (EDM) drilling after the blade has been manufactured using an EDM device. Indeed, EDM processes are the only ones compatible with the complex geometries of the blades and guarantee material integrity during drilling.

[0010] The electrical discharge machining (EDM) device typically includes at least one electrode that is either moved a predetermined distance or moved to a given condition. Once this distance or condition is reached, the drilling depth is considered to be achieved. Controlling this distance or condition is particularly important. Indeed, if these parameters are incorrect, there is a risk that the surface of the internal cavity opposite the drilled surface will be impacted by the electrodes or even perforated. Such an impact can generate mechanical defects on the blade, or even its rupture, and aerothermal defects due to disruption of the airflow within the blade.

[0011] In order to further improve blade cooling, it is now proposed to significantly reduce the thickness of the internal cavities to maximize internal heat exchange. However, current electrical discharge machining (EDM) drilling processes cannot guarantee impact-free drilling due to the very thin cavity thickness. Furthermore, again with the aim of improving blade cooling, the cooling passages have a complex geometry that is difficult to achieve using EDM drilling processes.

[0012] In this context, there is a need to provide a manufacturing process for a hollow blade having thin internal cavities, allowing the creation of cooling passages with complex geometries. Summary of the invention

[0013] To this end, the invention proposes a method for manufacturing a hollow blade for a turbomachine, the method comprising the following steps:

[0014] (a) manufacture a blade comprising:

[0015] an external wall comprising a leading edge, a trailing edge, an intrados face and an extrados face which connect the leading edge to the trailing edge, and

[0016] an internal wall delimiting an internal cavity,

[0017] (d) drilling the outer wall of the blade by electro-erosion to form channels of cooling.

[0018] The process is remarkable in that:

[0019] - in step (a), the blade includes cooling slots extending from the inner wall towards the outer wall, each having a first end opening into the internal cavity and a second end located between the inner and outer walls, and

[0020] - in step (d), each hole is drilled from the outer wall to the second end of each cooling slot so that each cooling channel opens respectively into a cooling slot.

[0021] According to the manufacturing process of the invention, two main steps are implemented.

[0022] According to the first manufacturing step of the blade, a blade having cooling slots is proposed.

[0023] According to the second manufacturing step of the blade according to the invention, cooling channels are formed by drilling the blade using electrical discharge machining (EDM). According to this step, the drilling of these cooling channels opens into the second end of the cooling slots.

[0024] Thus, at the end of these steps, the blade is provided with cooling passages which extend from the outer wall to the inner cavity of the blade in order to create an air film around the blade and improve its cooling.

[0025] Such a manufacturing process, which is structured around two manufacturing steps—the fabrication of a blade equipped with slots and the drilling of channels—allows the creation of air passages, formed by the combination of these slots and channels, of any geometry and without impact, despite internal cavity thicknesses of 1 mm or less. Indeed, the presence of cooling slots prior to drilling by electrical discharge machining (EDM) guarantees a maximum drilling depth significantly less than the thickness of the internal cavity. Furthermore, the presence of such cooling slots makes it possible to initiate complex geometries for the creation of cooling air passages, for example, angled or frustoconical shapes.

[0026] The process of the invention therefore makes it possible to provide blades whose aerothermal and mechanical properties are improved.

[0027] The invention may comprise one or more of the following features, taken individually or in combination with each other:

[0028] - step (a) comprises the following substep (aO):

[0029] (aO) fabricate a core intended to form the internal cavity, the core comprising a body and appendages intended to form the cooling slots, each appendage extending from the body and comprising a first end connected to the body and a second end opposite the body,

[0030] - step (a) comprises the following sub-steps carried out after step (aO):

[0031] (al) fabricate a model of the dawn around the core,

[0032] (a2) manufacture a mold of the dawn's shell around the model,

[0033] (a3) ​​remove the model,

[0034] (a4) optionally, heat treat the shell mold,

[0035] (a5) pouring a metal into the shell mold, and

[0036] (a6) remove the core,

[0037] - between steps (a) and (d), the process comprises the following steps:

[0038] (b) provide a virtual reconstruction of the dawn obtained in step (a) and determine spatial coordinates of the cooling slots,

[0039] (c) provide an electrical discharge machining device comprising at least one electrode configured to bore through the blade by electro-erosion to form the cooling channels, the position of the electrode vis-à-vis the blade being determined according to the spatial coordinates obtained in step (b),

[0040] - in step (b), the virtual reconstruction is performed by imaging, in particular by tomography,

[0041] - at step (aO), at least one of the appendages extends along an axis perpendicular to an axis of nucleus elongation,

[0042] - at step (aO), at least one of the appendages extends along an axis inclined with respect to an axis of nucleus elongation,

[0043] - at step (aO), at least one of the appendages has a frustoconical shape, the the first end having a diameter greater than the diameter of the second end,

[0044] - at step (aO), the core is produced by additive manufacturing,

[0045] - at step (aO), the core is produced by injection molding. Brief description of the figures

[0046] Other features and advantages will become apparent from the following description of a non-limiting embodiment of the invention with reference to the accompanying drawings in which:

[0047] [Fig. 1] is a schematic longitudinal cross-sectional representation of half an aircraft turbomachine according to the invention,

[0048] [Fig.2] is a schematic representation of a blade pierced by the process according to the invention,

[0049] [Fig. 3] is a schematic cross-sectional representation of the blade of the [Fig.2],

[0050] [Fig.4] is a schematic representation of a blade according to a first embodiment,

[0051] [Fig. 5] is a schematic representation of a blade according to a second embodiment,

[0052] [Fig. 6] is a schematic representation of a blade according to a third embodiment,

[0053] [Fig.7] is a synoptic diagram of the process of the invention

[0054] [Fig. 8] is a schematic representation of a kernel according to a first example of realization,

[0055] Figure 9 is a schematic representation of a kernel according to a second embodiment,

[0056] Figure 10 is a schematic representation of a kernel according to a third embodiment,

[0057] [Fig. 1 1] is a schematic representation of a blade before the drilling stage and in which the core of [Fig. 8] has been implemented,

[0058] [Fig.12] is a schematic representation of a blade before the drilling stage and in which the core of [Fig.9] has been implemented,

[0059] [Fig. 13] is a schematic representation of a blade before the drilling stage and in which the core of [Fig. 10] has been implemented,

[0060] [Fig.14] is a schematic representation of an electro-erosion device implemented in the process of the invention,

[0061] [Fig.15] is a schematic representation of a blade during the drilling stage and in which the core of [Fig.8] has been implemented,

[0062] [Fig.16] is a schematic representation of a blade during the drilling stage and in which the core of [Fig.9] has been implemented,

[0063] [Fig. 17] is a schematic representation of a blade during the drilling stage and in which the core of [Fig. 10] has been implemented. Detailed description of the invention

[0064] Fig. 1 illustrates an example of a turbomachine 1, in particular an aircraft turbomachine. The turbomachine 1 extends around and along a longitudinal axis X.

[0065] In the present application, the terms "upstream", "downstream", are defined with respect to the direction of gas flow in the turbomachine 1 along the longitudinal axis X.

[0066] The terms "axial", "axially", "radial", "radially", are defined with respect to the longitudinal axis X of the turbomachine 1.

[0067] The terms "internal", "interior", "external", "outside", "externally" are defined relative to the distance from the longitudinal axis X along a radial axis perpendicular to the longitudinal axis X.

[0068] The turbomachine 1 comprises, from upstream to downstream, a blower 2, at least one compressor such as a low-pressure compressor 3 and a high-pressure compressor 4, a combustion chamber 5, at least one turbine such as a high-pressure turbine 6 and a low-pressure turbine 7, and a nozzle (not shown).

[0069] The blower 2 allows the intake of an airflow F which divides into a primary flow Fl and a secondary flow F2. The primary flow Fl passes through the engine of the turbomachine 1 while the secondary flow F2 is directed towards a secondary duct.

[0070] The primary flow Fl is compressed within the low pressure compressor 3 and then the high pressure compressor 4. The compressed air is then mixed with a fuel and burned within the combustion chamber 5. The gases formed by the combustion pass through the high pressure turbine 6 and low pressure turbine 7. The gases finally escape through the nozzle whose cross-section allows the acceleration of these gases to generate propulsion.

[0071] The fan 2 is, for example, shrouded. It is surrounded by an annular housing 2b centered on the longitudinal axis X. The housing 2b is, for example, surrounded by a nacelle (not shown) of the turbomachine 1.

[0072] With reference to [Fig. 2], the turbomachine 1, in particular the high-pressure turbine 6, comprises blades 8 extending radially from a disk (not shown) that is movable or fixed and rotates about the longitudinal axis X. Each blade 8 extends along an axis of length Y perpendicular to the longitudinal axis X. Each blade 8 extends along this axis of length Y between a head 10 and a foot 12 and comprises a blade 9. The foot 12 is, for example, connected to the blade 9 by a platform 11. The foot 12 of each blade 8 is respectively mounted in a disk to retain the blade 8 on the disk.

[0073] The blade 9 has an aerodynamic shape and includes an external wall comprising an intrados face 9i and an extrados face 9e connected by a leading edge 9a and a trailing edge 9b.

[0074] With reference to [Fig. 3], the blade 8 further comprises at least one internal wall 13. The internal wall 13 is located inside the external wall. The internal wall 13 extends, for example, along the elongation axis Y between the head 10 and the foot 12 of the blade 8. The internal wall 13 has an extrados surface 13e located on the side of the extrados face 9e and an intrados surface 13i located on the side of the intrados face 9i.

[0075] The blade 8 is made of an electrically conductive material. The material is, for example, a metallic material or a composite material. Advantageously, the composite material is a ceramic matrix composite (CMC). Such materials have the advantage of being able to withstand high temperatures and therefore allow the implementation of these blades 8 close to the combustion chamber 5, in an environment subjected to high temperatures.

[0076] In order to further improve the temperature resistance of the blades 8, each blade 8 includes at least one internal cavity 14 for the circulation of air, for example taken from the low-pressure compressor 4, inside the blade 8. The internal cavity 14 is delimited by the internal wall 13 and extends preferentially along the elongation axis Y of the blade 8. It extends, for example, from the head 10 to the foot 12 of the blade 8.

[0077] The thickness e of the internal cavity 14, as measured along a Z-axis perpendicular to the elongation axis Y, is, for example, between 0.5 mm and 2 mm, preferably equal to 1 mm. Such a thickness e of the internal cavity 14 maximizes heat exchange within the blade 8 to improve its cooling.

[0078] In order to further improve the temperature resistance of the blades 8, each blade 8 further comprises, according to the invention, cooling air passages 15 provided in the outer wall and which open into the inner cavity 14. The air passages 15 thus allow the passage of air from the inner cavity 14 to the outer wall of the blade 8 in order to create an air film around the blade 8 to cool it.

[0079] The air passages 15, for example, have a circular cross-section. They advantageously have a diameter on the order of a micrometer. The air passages 15 are advantageously aligned and / or staggered.

[0080] According to an example of an embodiment shown in [Fig.4], at least one air passage 15, and preferably each air passage 15, extends along the Z axis perpendicular to the elongation axis Y of the internal cavity 14.

[0081] According to another embodiment shown in [Fig. 5], at least one air passage 15, and preferably each air passage 15, is angled. Such a configuration allows the circulation of the cooling airflow in the blade 8 to be adapted. Indeed, the cooling air can circulate in a first zone of the blade 8 and be ejected in a second zone of the blade 8.

[0082] According to an exemplary embodiment shown in [Fig. 6], at least one air passage 15, and preferably each air passage 15, is frustoconical. The air passage 15 flares, for example, towards the internal cavity 14. Such a configuration improves the flow of cooling air to the internal cavity 14, particularly when the distance between the external and internal walls 13 is significant.

[0083] A method for manufacturing such a hollow blade 8 according to the invention will now be described.

[0084] With reference to [Fig.7], the manufacturing process comprises the following steps:

[0085] (a) manufacture a blade 8' comprising the outer wall and the inner wall 13 delimiting the internal cavity 14. In step (a), the blade 8' further comprises cooling slots 16 extending from the internal wall 13 to the external wall, each having a first end 16a opening into the internal cavity 14 and a second end 16b situated between the internal 13 and external walls, then

[0086] (b) preferably, provide a virtual reconstruction of dawn 8' obtained at step (a) and determine the spatial coordinates of the cooling slots 16, then

[0087] (c) preferably, provide an electro-erosion device 100 comprising at less one electrode 102 configured to bore by electro-erosion the blade 8' of step (a) to form cooling channels 17, the position of the electrode 102 vis-à-vis the blade 8' being determined according to the spatial coordinates obtained in step (b), and

[0088] (d) drill the outer wall of the blade 8' by electro-erosion to form the channels of cooling 17, each drilling being made from the outer wall to the second end 16b of each cooling slot 16 so that each cooling channel 17 opens respectively into a cooling slot 16.

[0089] According to a particularly advantageous embodiment of the invention, step (a) comprises the following chronological substeps:

[0090] (aO) fabricate a core 18 intended to form the internal cavity 14, the core 18 comprising a body 19 and appendages 20 intended to form the cooling slots 16, each appendage 20 extending from the body 19 and comprising a first end 20a connected to the body 19 and a second end 20b opposite the body 19,

[0091] (al) fabricate a model of the dawn around the core 18,

[0092] (a2) fabricate a shell mold of the dawn around the model,

[0093] (a3) ​​remove the model,

[0094] (a4) optionally, heat treat the shell mold,

[0095] (a5) pouring a metal into the shell mold,

[0096] (a5') solidify the metal and remove the shell mold, and

[0097] (a6) remove the kernel 18.

[0098] With reference to Figures 8 to 10, preferably, substep (aO) of manufacturing the core 18 is carried out by additive manufacturing or by molding. The core 18 may be made of ceramic, refractory metallic material, or a mixture thereof. The appendages 20 and the body 19 of the core 18 may be monolithic or form two separate parts then joined together by bonding, welding, or any other fastening method. The appendages 20 and the body 19 may comprise the same material or different materials.

[0099] The body 19 of the core 18 extends along an elongation axis Y' parallel to the elongation axis Y of the blade 8.

[0100] Each appendage 20 has an external diameter between 0.1 mm and 0.5 mm, preferably 0.35 mm and a length L between 0.5 mm and 2 mm, preferably 1 mm.

[0101] According to a first embodiment illustrated in [Fig.8], at least one of the appendages 20 extends along an axis Z' perpendicular to the elongation axis Y' of the core 18.

[0102] According to a second embodiment illustrated in [Fig.9], the Z' axis of at least one of the appendages 20 is inclined at an angle other than 90° with respect to the elongation axis Y' of the core 18.

[0103] According to a third embodiment illustrated in [Fig.10], at least one of the appendages 20 has a truncated conical shape, the first end 20a having a diameter greater than the diameter of the second end 20b.

[0104] The substep (al) of manufacturing the model of the blade 8 is preferably carried out by wax injection molding around the core 18.

[0105] Substep (a2) of manufacturing the shell mold can be carried out, for example, by successive immersions of the model in slips. The slips include, for example, a ceramic material. The immersion can be followed by a drying step of the shell mold.

[0106] Substep (a3) ​​can be carried out by pre-cooking the shell mold at a first temperature allowing the shell mold to be dewaxed.

[0107] Substep (a4) can be carried out by heating the shell mold at a second temperature higher than the first temperature. Such a substep makes it possible to increase the strength of the shell mold.

[0108] Substep (a5) can be carried out under vacuum. The metal is molten during this substep. The metal is, for example, a metal alloy.

[0109] Substep (a5) can be followed by a substep a5' of metal solidification and removal of the shell mold. The shell mold is, for example, broken.

[0110] Substep (a6) can be carried out by mechanical or chemical treatment. For example, the blade 8' can be placed in a chemical bath to dissolve the core 18. At the end of substep (a6), the blade 8' is obtained according to step (a) as illustrated in Figures 11 to 13.

[0111] According to a particularly advantageous embodiment of the invention, step (b) of virtual reconstruction of the blade 8 is carried out by imaging, in particular by tomography, especially by X-ray tomography. Such a step makes it possible to determine precisely the position of the cooling slots 16.

[0112] In step (c), and with reference to [Fig. 14], the electrical discharge machining (EDM) device 100 comprises a drilling guide 101 and at least one electrode 102 carried by the guide 101. Preferably, the device 100 is of the multi-drilling type. Such a device 100 has the advantage of allowing the drilling of a plurality of cooling channels 17 simultaneously. This results in an economic gain of at least 30% compared to a single-drilling EDM device with which only one cooling channel 17 can be created at a time. Thus, the device 100 comprises, for example, between four and thirty electrodes 102.

[0113] The electrodes 102 are arranged parallel to each other and each allows a cooling channel 17 to be formed by electrical discharge machining (EDM). Each electrode 102 has an elongated shape. Each electrode 102 is configured to bore a cooling channel 17 by EDM from the outer wall of the blade 8 to the second end 20b of the cooling slot 16.

[0114] According to step (c) of the invention, each electrode 102 is positioned in the guide 101 according to the spatial coordinates of the cooling slots 20 obtained in step (b). Such adaptive drilling ensures the position of the cooling channels 17 according to the position of the cooling slots 16 and thus provides conforming cooling passages 15.

[0115] In step (d), the blades 8' are drilled by electrical discharge machining (EDM), as illustrated for example in Figures 15 to 17, according to the different cores 18 used. For this purpose, the electrodes 102 are moved towards the outer wall of the blade 8'. The blades 8 obtained at the end of step (d) thus have cooling passages 15 as described above.

[0116] Such an electro-erosion process is compatible with the aerodynamic shape of the blades 8 and makes it possible to guarantee the soundness of the material during the drilling of the cooling channels 17.

[0117] Thanks to the two-step manufacturing of the hollow blades 8 according to the invention, by first creating cooling slots 16 and then drilling cooling channels 17, it is possible to create cooling passages 15 without impact even when the internal cavities 14 have a thickness e less than or equal to 1 mm. Also, thanks to such a two-step process, it is possible to create angled, frustoconical, or any other geometric cooling passages 15.

[0118] Adaptive drilling by electro-erosion according to the advantageous steps (b) and (c) makes it possible to simplify such a process into two steps. Indeed, it is possible to correctly target the cooling slots 16 during the electro-erosion drilling Cooling channels 17. The cooling passages 15 thus present the desired configuration.

Claims

Demands

1. A method for manufacturing a hollow blade (8) for a turbomachine (1), the method comprising the following steps: (a) manufacturing a blade (8') comprising: an outer wall including a leading edge (9a), a trailing edge (9b), an intrados face (9i) and an extrados face (9e) connecting the leading edge (9a) to the trailing edge (9b), and an inner wall (13) defining an internal cavity (14), (d) drilling the outer wall of the blade (8) by electrical discharge machining (EDM) to form cooling channels (17), characterized in that: - in step (a), the blade (8') comprises cooling slots (16) extending from the inner wall (13) to the outer wall and each having a first end (16a) opening into the internal cavity (14) and a second end (16b) located between the inner wall (13) and the outer wall, and - at step (d),Each hole is drilled from the outer wall to the second end (16b) of each cooling slot (16) such that each cooling channel (17) opens into a cooling slot (16), and the method further comprises, between steps (a) and (d), the following steps: (b) providing a virtual reconstruction of the blade (8') obtained in step (a) and determining spatial coordinates of the cooling slots (16), (c) providing an electrical discharge machining (EDM) device (100) comprising at least one electrode (102) configured to drill the blade (8') by electrical discharge machining to form the cooling channels (17), the position of the electrode (102) relative to the blade (8') being determined according to the spatial coordinates obtained in step (b).

2. A method according to the preceding claim, characterized in that step (a) comprises the following substep (aO): (aO) manufacturing a core (18) for forming the internal cavity (14), the core (18) comprising a body (19) and appendages (20) for forming the cooling slots (16), each appendage (20) extending from the body (19) and comprising a first end (20a) connected to body (19) and a second end (20b) opposite body (19).

3. A method according to the preceding claim, characterized in that step (a) comprises the following substeps carried out after step (a0): (a1) fabricate a pattern of the blade (8) around the core (18), (a2) fabricate a shell mold of the blade (8) around the pattern, (a3) ​​remove the pattern, (a4) optionally, heat treat the shell mold, (a5) pour metal into the shell mold, and (a6) remove the core (18).

4. A method according to any one of the preceding claims, characterized in that in step (b), the virtual reconstruction is carried out by imaging, in particular by tomography.

5. A method according to any one of claims 2 to 3 or 4 in combination with claim 2, characterized in that at step (aO), at least one of the appendages (20) extends along an axis (Z') perpendicular to an elongation axis (Y') of the core (18).

6. A method according to any one of claims 2 to 3 or 4 in combination with claim 2, characterized in that at step (aO), at least one of the appendages (20) extends along an axis (Z') inclined with respect to an elongation axis (Y') of the core (18).

7. A method according to any one of claims 2 to 3 or 4 in combination with claim 2, characterized in that at step (a0), at least one of the appendages (20) has a frustoconical shape, the first end (20a) having a diameter greater than the diameter of the second end (20b).

8. A method according to any one of claims 2 to 3 or 4 to 7 in combination with claim 2, characterized in that at step (aO), the core (18) is produced by additive manufacturing.

9. A method according to any one of claims 2 to 3 or 4 to 7 in combination with claim 2, characterized in that at step (aO), the core (18) is produced by injection molding.

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