Method for manufacturing a hollow turbine blade for a turbine engine

Abstract

The invention relates to a method for manufacturing a hollow turbine blade (10) for a turbine engine, this hollow blade (10) comprising pressure-side (16) and suction-side walls (18) that are passed through by internal cooling channels (28), the method comprising at least one first moulding phase (PH1, PH'1) employing the lost-wax casting technique using a molten metal, the first moulding phase (PH1, PH'1) comprising at least one step b) of manufacturing a mould (34) made of refractory material, the internal walls (36) of which match the external shape of the blade (10) to be manufactured, characterised in that, in this step b), a plurality of projections (52) defining outlet opening counterforms (30) of the internal cooling channels (28) are formed on the internal walls (36) of the mould (34) made of refractory material.

Description

[0001] DESCRIPTION

[0002] TITLE: METHOD FOR MANUFACTURING A HOLLOW TURBINE BLADE FOR A TURBOMACHINE

[0003] Technical field of the invention

[0004] The invention relates to the general field of turbomachine turbine blades, and more particularly to that of hollow turbine blades equipped with integrated cooling circuits produced using the lost wax casting technique.

[0005] Technical background

[0006] As is known, a turbomachine comprises a combustion chamber in which air and fuel are mixed before being burned. The gases resulting from this combustion flow downstream of the combustion chamber and then feed a high-pressure turbine and a low-pressure turbine. Each turbine comprises one or more rows of fixed blades (called nozzles) alternating with one or more rows of moving blades (called runners), mounted and spaced circumferentially around the turbine rotor. These turbine blades are subjected to the very high temperatures of the combustion gases, which reach values ​​well above those that these blades can withstand without damage, being in direct contact with these gases, which has the consequence of limiting their service life.

[0007] In order to solve this problem, it is known to equip these blades with internal cooling circuits having high levels of thermal efficiency and aimed at reducing the temperature of the latter. To do this, the blades are hollow and an air circulation is organized inside their internal cavities, air which is generally supplied by a pressurization circuit of internal enclosures of the turbines, this circuit itself being supplied by one or more compressors of the turbomachine.

[0008] Blades are known to have intrados and extrados walls. In addition to their internal cavities, blades also have internal perforations that pass through these walls and open onto the external surfaces of these walls. The air ejected through the internal channels generates a layer of air protecting the surface of the blade. To optimize this layer of air, the internal channels do not open directly onto the surface of the intrados and extrados walls, but through outlets extending each internal channel. These outlets, known by the English acronym "shaped holes" or "caps" in French, have the function of tilting and directing the air flow from each channel in order to cause it to flow in a laminar flow on the surface of the blade, which allows for better insulation of the latter.

[0009] The manufacture of blades in a foundry is a complex process that requires the use of a ceramic core that will allow these internal cavities to be created during the casting of the wax and then the molten metal. Application WO2016 / 151234 in the name of the applicant shows a ceramic core that makes it possible to create all the internal cavities of a blade in a single element and thus ensure particularly efficient internal cooling without significantly increasing the cooling air flow and therefore without penalizing engine performance.

[0010] The internal channels, as also described in application FRAI -2 961 552, are generally conventionally produced by laser drilling or EDM (sinking electroerosion). The outlets, or caps or "shaped holes" are conventionally produced using the same processes.

[0011] Also known from the prior art are documents US-2013-0139990-A1, US-2007-0175009-A1, US-2013-0333855-A1 and US-8066052-B2.

[0012] Conventionally, to manufacture the blade, it is first cast using a lost wax casting process.

[0013] Then the internal channels of the blade are made in one step, by laser drilling or EDM. Finally, in a next step the outlet vents are made by EDM on the existing internal channels.

[0014] During these two steps, the coordinates of the positioning of the laser or EDM drilling tool are expressed in a three-dimensional frame of reference taking as reference points points located on a root of the blade, which are consequently quite far from the channels and caps to be produced. This distance induces dispersions in the positioning of the channels and outlet openings and problems of reproducibility of the position of internal channels and outlet openings. Consequently, it may occur on finished parts that a certain number of internal channels do not open into the outlet openings but directly into the external surfaces of the intrados extrados walls, and that, conversely, outlet openings are found to be blind. A blade with such defects must then be scrapped. In addition, this lack of reproducibility leads to a deviation from the nominal position of the outlet openings as calculated according to a nominal model.As a result, cooling performance is reduced by deviating from this nominal model.

[0015] There is therefore a real need for a blade manufacturing process that can guarantee reproducible positioning of the outlet vents.

[0016] Summary of the invention

[0017] The present invention therefore aims to overcome the drawbacks linked to these non-conformities in the positioning of the outlet vents by proposing a method for manufacturing the blade which makes it possible to produce the outlet vents directly during the molding of the blade.

[0018] For this purpose, the invention proposes a method for manufacturing a hollow turbine blade for a turbomachine, this hollow blade comprising intrados and extrados walls, at least one of which is crossed by internal cooling channels, said method comprising at least a first molding phase according to the lost wax casting technique using a molten metal, said first molding phase 1) comprising the following steps: a) manufacturing at least one ceramic core defining at least one counterform of at least one internal cavity of the blade to be manufactured, b) manufacturing a mold made of refractory material, the internal walls of which match the external shape of the blade to be manufactured, c) placing said core in said mold made of refractory material, d) casting a lost wax in said mold made of refractory material between the core and its internal walls, e) once the wax has solidified,opening the mold and removing the assembly formed from the core trapped in the solidified lost wax, f) forming on said assembly a ceramic shell conforming to an external shape of said assembly, g) removing the lost wax from the ceramic shell, h) pouring molten metal into a space left free between said core and said shell by removing the lost wax, i) opening or destroying the ceramic shell, j) removing the ceramic core in order to obtain a foundry blank of the hollow turbine blade, characterized in that, during step b), a plurality of protuberances are formed on the internal walls of the mold made of refractory material, defining counterforms of outlet openings of said internal cooling channels.,

[0019] This process advantageously ensures a reproducible position of the outlet vents. They can therefore constitute reference points for the positioning of the internal cooling channels.

[0020] According to other characteristics of the process:

[0021] - each protuberance defines the counterform of an outlet mouth in the form of a flared bowl,

[0022] - each protuberance extends along a main elongation axis and has at least:

[0023] • a first substantially trapezoidal face having a large base contiguous with the internal wall of the mold and a height oriented parallel to the main elongation axis, this first face being inclined at an angle of less than 30 degrees with the internal wall of the mold,

[0024] • a second substantially rectangular face, aligned with the first face along the main elongation axis and contiguous with a small base of the first face, this second face being inclined at an angle greater than 80 degrees and less than 90 degrees with the internal wall of the mold, and

[0025] • two third and fourth substantially triangular lateral faces bordering the first and second faces, the first to fourth faces delimiting the counterform of the flared bowl, According to a first embodiment of the method, during step a), the core is manufactured with a plurality of pins defining counterforms of said internal cooling channels, said pins being of a determined length configured so that, during step c), said pins come into contact with said protuberances, so that in step j) the foundry blank of the hollow turbine blade directly integrates these channels communicating with the outlet vents.

[0026] This first embodiment of the process allows the internal channels to be produced at the same time as the outlet vents and the rest of the blade.

[0027] According to this first embodiment of the method, the pins are oriented to touch the protrusions at the junction of the first and second faces of the protrusions.

[0028] According to a second embodiment of the method, the latter comprises, after the first molding phase, a second machining phase, which comprises a step k) during which a bottom of the outlet openings of the raw casting of the blade is pierced to form said internal cooling channels therein.

[0029] This second embodiment of the method makes it possible to use the outlet vents to define a reference point allowing the positioning of the tool used to create the internal cooling channels.

[0030] According to this second embodiment of the method, step k) is carried out by electroerosion using an EDM sinking tool or by a drilling tool.

[0031] Advantageously, during step k), position and movement coordinates of the tool are expressed in a reference frame comprising 3 reference points, these points all belonging to at least one outlet mouth. The invention also relates to a mold made of refractory material for implementing a manufacturing method of the type described above, characterized in that the protuberances are formed in one piece with the internal walls of the mold made of refractory material.

[0032] The invention also relates to a mold made of refractory material as an alternative for implementing a manufacturing method of the type described above, characterized in that the protuberances are added and fixed to the internal walls of the mold made of refractory material.

[0033] The invention finally relates to a turbomachine blade manufactured according to a method as described previously.

[0034] Brief description of the figures

[0035] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

[0036] [Fig. 1] Figure 1 is a perspective view of a turbomachine blade according to the invention;

[0037] [Fig. 2] Figure 2 is a perspective detail view of an outlet mouth and internal channel formed in a wall of the blade of Figure 1;

[0038] [Fig. 3] Figure 3 is a top view of a protrusion forming the counterform of an outlet mouth of Figure 1;

[0039] [Fig. 3a] Figure 3a is a partial schematic perspective view of a part of a mold intended to be located on the side of an extrados of the blade to be formed;

[0040] [Fig. 3b] Figure 3b is a partial schematic perspective view of a part of a mold intended to be located on the side of an intrados of the blade to be formed;

[0041] [Fig. 4] Figure 4 is a schematic view illustrating a first step of manufacturing a ceramic core defining at least one counterform of an internal cavity of the blade of Figure 1 in the context of a method according to a first embodiment of the invention, [Fig. 5] Figure 5 is a schematic view illustrating a second step of placing the core in a mold of refractory material whose internal walls match the external shape of the blade of Figure 1 in the context of the method according to the first embodiment of the invention,

[0042] [Fig. 6] Figure 6 is a schematic view illustrating a third step of casting a lost wax into said mold made of refractory material between the core and its internal walls in the context of the method according to the first embodiment of the invention,

[0043] [Fig. 7] Figure 7 is a schematic view illustrating a fourth step of removing the assembly formed from the core trapped in the solidified lost wax in the context of the method according to the first embodiment of the invention,

[0044] [Fig. 8] Figure 8 is a schematic view illustrating a fifth step of forming on this assembly a ceramic shell matching an external shape of said assembly within the framework of the method according to the first embodiment of the invention,

[0045] [Fig. 9] Figure 9 is a schematic view illustrating a sixth step of removing the lost wax from the ceramic shell in the context of the method according to the first embodiment of the invention,

[0046] [Fig. 10] Figure 10 is a schematic view illustrating a seventh step of pouring molten metal into a space left free between the core and the shell in the context of the method according to the first embodiment of the invention,

[0047] [Fig. 11] Figure 11 is a schematic view illustrating an eighth step of destruction of the shell in the context of the method according to the first embodiment of the invention,

[0048] [Fig. 12] Figure 12 is a schematic view illustrating a ninth step of removing the ceramic core in order to obtain a casting blank of the hollow turbine blade in the context of the method according to the first embodiment of the invention,

[0049] [Fig. 13] Figure 13 is a block diagram illustrating the steps of the method according to the first embodiment of the invention, [Fig. 14] Figure 14 is a schematic view illustrating a first step of manufacturing a ceramic core defining at least one counterform of an internal cavity of the blade of Figure 1 in the context of a method according to a second embodiment of the invention,

[0050] [Fig. 15] Figure 15 is a schematic view illustrating a second step of placing the core in a mold made of refractory material, the internal walls of which match the external shape of the blade of Figure 1 in the context of the method according to the second embodiment of the invention,

[0051] [Fig. 16] Figure 16 is a schematic view illustrating a third step of casting a lost wax into said mold made of refractory material between the core and its internal walls in the context of the method according to the second embodiment of the invention,

[0052] [Fig. 17] Figure 17 is a schematic view illustrating a fourth step of removing the assembly formed from the core trapped in the solidified lost wax in the context of the method according to the second embodiment of the invention,

[0053] [Fig. 18] Figure 18 is a schematic view illustrating a fifth step of forming on this assembly a ceramic shell matching an external shape of said assembly within the framework of the method according to the second embodiment of the invention,

[0054] [Fig. 19] Figure 19 is a schematic view illustrating a sixth step of removing the lost wax from the ceramic shell in the context of the method according to the second embodiment of the invention,

[0055] [Fig. 20] Figure 20 is a schematic view illustrating a seventh step of pouring molten metal into a space left free between the core and the shell in the context of the method according to the second embodiment of the invention,

[0056] [Fig. 21] Figure 21 is a schematic view illustrating an eighth step of destruction of the shell in the context of the method according to the second embodiment of the invention,

[0057] [Fig. 22] Figure 22 is a schematic view illustrating a ninth step of removing the ceramic core in order to obtain a casting blank of the hollow turbine blade and drilling the internal pipes in the method according to the second embodiment of the invention, and

[0058] [Fig. 23] Figure 13 is a block diagram illustrating the steps of the method according to the second embodiment of the invention.

[0059] Detailed description of the invention

[0060] Figure 1 shows a hollow turbine blade 10 of a turbomachine. In a known manner, such a blade 10 comprises a root 12 which is intended to be received in a turbine rotor disk (not shown) and a blade 14 which extends from this root. The blade 14 comprises two intrados 16 and extrados 18 walls which meet at one end of the blade 14 at a leading edge 20 and at an opposite downstream end of the blade at a trailing edge 22.

[0061] Inside the blade 10 there is at least one internal cavity 24, shown schematically in FIG. 12, which is intended to allow the circulation of a flow of cooling air intended to cool the turbine blade in order to preserve its integrity, because the blade is bathed in a flow of hot gases coming from the combustion chamber of the turbomachine and must be cooled.

[0062] The cooling air flow comes from an internal pressurization circuit of the turbomachine enclosures, this internal pressurization circuit being supplied with pressurized air coming from at least one tapping made on a compressor of the turbomachine.

[0063] As illustrated in Figures 2, 12 and 22, the cavity 24 communicates with an external surface 26 of the intrados wall 16 or extrados wall 18 via a plurality of internal cooling channels 28. The presence of these channels makes it possible to bathe the external surface of the blade 10 in a flow of cooling air making it possible to limit the action of the hot gases on the external surfaces 26 of the blade 10.

[0064] In order for this flow of cooling gas to be as efficient as possible, it is important, on the one hand, to multiply the internal channels 28 and on the other hand that these do not open directly into the surfaces 26, but via outlet vents 30. These outlet vents 30, also called caps, and visible in figures 1 and 2, make it possible to direct the air flow according to a laminar flow substantially at the exit of the surface 26. For this purpose, as illustrated in figure 2, each outlet vent 30 has a flared shape.

[0065] Conventionally, to manufacture such a blade 10, the blade 10 provided with its internal cavity 24 is first manufactured during a first molding phase by a lost wax molding process. Then the internal channels 28 are produced by laser drilling or by electroerosion (EDM). Finally, the outlet mouths 30 are produced by EDM on the already existing internal channels 28.

[0066] During these two steps of manufacturing the channels 28 and the mouths 30, the coordinates of the positioning of the laser or EDM drilling tools are expressed in a three-dimensional reference system taking as reference points points located on the root 12 of the blade 10, which are consequently quite far from the channels 28 and outlet mouths 30 to be produced. This distance induces dispersions as to the relative positioning of the channels 28 and the outlet mouths and problems of reproducibility of the position of internal channels 28 and outlet mouths 30. Consequently, it may occur on the finished blades that a certain number of internal channels 28 do not open into the outlet mouths 30 but directly into the external surfaces 26 and that conversely the outlet mouths 30 are found to be blind. A blade 10 having such defects must then be scrapped because the cooling of its surface 26 could not be carried out correctly.

[0067] There is therefore a real need for a manufacturing method for the blade 10 making it possible to guarantee reproducible positioning of the outlet vents 30 relative to the internal channels 28.

[0068] The invention makes it possible to achieve this goal by proposing a manufacturing method in which the outlet vents 30 are produced simultaneously with the molding of the blade 10.

[0069] The steps of a method for manufacturing a blade 10 according to this method have been represented according to a first embodiment in Figures 4 to 13 and according to a second embodiment in Figures 14 to 23. The two embodiments of the manufacturing method have common characteristics.

[0070] According to the invention, the method comprises at least a first molding phase PH1, shown in Figures 4 to 23, according to the lost wax casting technique using molten metal.

[0071] As illustrated in Figures 13 and 23, this molding phase firstly comprises a first step a) shown in Figures 4 and 14 during which at least one ceramic core 32 is manufactured defining at least one counterform of the at least one internal cavity 24 of the blade 10 to be manufactured.

[0072] Then, during a step b) shown in figures 13 and 23, a mold 34 is made of refractory material, the internal walls 36 of which match the external shape of the blade 10 to be manufactured. As illustrated in figures 5 and 15, the core 32 is placed in this mold 34 of refractory material during a step c).

[0073] Then, as illustrated in figures 6 and 16, during a step d) shown in figures 13 and 23, a lost wax 38 is poured into the mold 34 made of refractory material, between the core 32 and the internal walls 36 of the mold 34.

[0074] Then, as illustrated in Figures 7 and 17, once the wax has solidified, during a step e), the mold is opened and the assembly 32 formed from the core trapped in the solidified lost wax 44 is removed.

[0075] As illustrated in Figures 8 and 18, during a step f) shown in Figures 13 and 23, a ceramic shell 46 is formed on this assembly which matches an external shape of this assembly 32, 44.

[0076] Then, as illustrated in Figures 9 and 19, during a step g) shown in Figures 13 and 23, the lost wax is removed from the ceramic shell 46. There therefore only remains a free space 45 between the core 32 and the shell 46. This removal is generally carried out by melting the lost wax by placing the assembly in a furnace.

[0077] Then during a step h) shown in Figures 10 and 20, a casting of molten metal 50 is carried out in the space 48 left free between the 32 core and said shell 46 by the removal of the lost wax. Then during a step i) shown in Figures 11 and 21, the shell 46 is opened or destroyed. There therefore remains only the core 32 trapped in the solidified metal 50.

[0078] Finally, during a step j) shown in Figures 12 and 22, the ceramic core 32 is removed in order to obtain a casting blank 10' of the hollow turbine blade. The removal is generally carried out by chemical dissolution in an autoclave, sometimes combined with immersion of the part in an ultrasonic bath.

[0079] These steps a) to j) known per se from the state of the art correspond to the classic steps of manufacturing a 10' foundry blank of a blade.

[0080] The invention proposes to take advantage of these steps to produce the outlet mouths 30 directly during the molding phase.

[0081] To this end, as illustrated in Figures 5, 6 and 15, 16, during step b) which has been shown in Figures 13 and 23, a plurality of protrusions 52 are formed on the internal walls 36 of the mold 34 made of refractory material, defining counterforms of the outlet mouths 30 of said internal cooling channels.

[0082] As can be seen in Figures 7 and 17, these protrusions 52 define cavities 54 on the surface of the assembly comprising the core 32 trapped in the wax 44, cavities 54 which define new protrusions 56 inside the shell 46 as shown in Figures 8 to 10 and 18 to 20. These protrusions 56 in turn define the outlet mouths 30 on the foundry blank 10', as shown in Figures 11, 12 and 21, 22.

[0083] Thus, by the play of shapes and counter-shapes, it is possible to easily obtain the outlet vents 30.

[0084] The two embodiments of the method differ with respect to the manufacture of the internal channels 28.

[0085] Indeed, according to the first embodiment of the invention which has been shown in figures 4 to 13, the internal channels 28 are also produced during the first molding phase PH1. Indeed, according to this first embodiment, during step a), the core 32 is manufactured with a central part 31 and a plurality of pins 33 defining counterforms of the internal cooling channels 28.

[0086] The pins 33 are of determined dimensions, advantageously made up of alumina rods or quartz tubes, positioned on the central part 31 of the core (the different columns) intended to form the assembly of the internal channels 28 passing through the intrados 16 and extrados 18 external walls of the blade.

[0087] The ceramic core 32 bristling with spikes 33 is therefore called a “hedgehog core”.

[0088] The 33 pins are of a determined length configured so that, during step c) of figure 5, said pins 33 come into contact with the protuberances 52, so that in step j) of figure 12, the raw casting 10' of the hollow turbine blade directly integrates the channels 28 communicating with the outlet mouths 30.

[0089] For this purpose, the pins 33 are oriented to touch the protrusions 52. This allows on the rough 10' to have continuity between the channels 28 and the outlet openings 30.

[0090] On the other hand, according to the second embodiment of the invention which has been shown in figures 14 to 23, the internal channels 28 are produced during a second machining phase PH'2 after a first molding phase PH'1. The steps of the molding phase PH'1 of figures 14 to 21 are substantially identical to those of the phase PH1 of the first embodiment of the invention, with the difference that the core 32 does not include pins.

[0091] As illustrated in Figures 22 and 23, this second embodiment of the method comprises, after the first molding phase PH'1, a second machining phase PH'2, which comprises a step k) during which a bottom of the outlet openings 30 of the casting blank 10' of the blade is pierced with a tool 58 to form said internal cooling channels 28 therein. This tool 58 is for example an EDM electro-erosion tool or a drilling tool such as a drill. In the second embodiment of the invention, the prior manufacture by molding of the outlet openings 30 advantageously allows them to be used as a reference.Indeed, whereas in the state of the art, positioning and movement coordinates of an EDM or drilling electro-erosion tool were expressed in a frame of reference comprising 3 reference points belonging to the root 12 of the blade, here during step k), these position and movement coordinates of the tool are expressed in a frame of reference comprising 3 reference points, all belonging to at least one outlet mouth 30. This guarantees more precise positioning of the tool 58, which makes it possible to avoid position offsets between the channels 28 and the outlet mouths 30.

[0092] As illustrated in Figures 2 and 3, each protrusion defines the counterform of an outlet mouth 30 in the form of a flared bowl. Indeed, it is desirable for the outlet mouth 30 to have a flared shape to guide the flow of pressurized air according to a substantially laminar flow, as represented by the arrows in Figure 2.

[0093] As illustrated in Figures 3, 3a and 3b, each protuberance 52 extends from the surface 36 of the mold 34 made of refractory material along a main elongation axis X and it has at least one first substantially trapezoidal face 60 having a large base 62 contiguous with the internal wall of the mold and a height oriented parallel to the main elongation axis X, this first face 60 being inclined at an angle of less than 30 degrees with the internal wall of the mold, which corresponds to an angle oc reproduced on the outlet mouth 30, as seen in Figure 2.

[0094] In Figures 3a and 3b, the reference 61 designates holes for injecting the wax into the mold. These holes 61 are located on the surface 36 and / or at the ends of the protuberances 52.

[0095] Each protuberance 52 comprises a second substantially rectangular face 64, aligned with the first face 60 along the main elongation axis X, and adjoining a small base 66 of the first face 60, this second face 64 being inclined at an angle greater than 80 degrees and less than 90 degrees with the internal wall of the mold, which corresponds to an angle P reproduced on the outlet mouth 30, as seen in FIG. 2. Each protuberance 52 finally comprises two third and fourth substantially triangular lateral faces 68, 70 bordering the first and second faces 60, 64.

[0096] In this way the first to fourth faces 60, 64, 68, 70 delimit the counterform of the flared bowl.

[0097] Preferably, to give the compressed air flow the desired orientation, in the first embodiment of the invention, the pins 33 will be arranged in contact with the protuberances 52 at the junction of the first and second faces 60 64. This makes it possible to obtain channels 28 opening at the bottom of the outlet vents 30, as shown in FIG. 2.

[0098] A similar positioning will be given to the internal channels 28 within the framework of the machining phase PH'2 of the method according to the second embodiment of the invention.

[0099] In both cases, it will be understood that subsequent deburring or polishing will always be required to obtain the desired surface finish for the final blade 10 from the rough casting 10'.

[0100] Regardless of the embodiment of the method of the invention, the protrusions 52 can be formed in two different ways.

[0101] The protrusions 52 may be formed in one piece with the internal walls of the mold 34 made of refractory material, for example by molding the latter.

[0102] Alternatively, the protrusions 52 can be attached and fixed to the internal walls 36 of the mold 34 made of refractory material.

[0103] The invention therefore makes it possible to obtain a hollow turbomachine blade 10 provided with internal channels 28 and outlet openings 30 corresponding to these channels 28.

Claims

CLAIMS 1. Method for manufacturing a hollow turbine blade (10) of a turbomachine, this hollow blade (10) comprising intrados (16) and extrados (18) walls, at least one of which is crossed by internal cooling channels (28), said method comprising at least a first molding phase (PH1, PH'1) according to the lost wax casting technique using a molten metal, said first molding phase (PH1, PH'1) comprising the following steps: a) manufacturing at least one ceramic core (32) defining at least one counterform of at least one internal cavity (24) of the blade (10) to be manufactured, b) manufacturing a mold (34) of refractory material, the internal walls (36) of which match the external shape of the blade (10) to be manufactured, c) placing said core (32) in said mold (34) of refractory material, d) casting a lost wax (38) into said mold (34) of refractory material between the core (32) and its internal walls (36),e) once the wax (38) has solidified, opening the mold (34) and removing the assembly formed by the core (32) trapped in the solidified lost wax (38), f) forming on said assembly (32, 38) a ceramic shell (46) matching an external shape of said assembly (32, 38), g) removing the lost wax (38) from the ceramic shell (46), h) pouring molten metal (50) into a space (48) left free between said core (32) and said shell (46) by removing the lost wax (38), i) opening or destroying the ceramic shell (46), j) removing the ceramic core (32) in order to obtain a foundry blank (10') of the hollow turbine blade (10), characterized in that, during step b), a ceramic shell (46) is formed on the internal walls (36) of the mold (34) in refractory material a plurality of protrusions (52) defining counterforms of outlet mouths (30) of said internal cooling channels (28), and in that, during step a),the core (32) is manufactured with a plurality of pins (33) defining counterforms of said internal channels, (28) for cooling, said pins (33) being of a determined length configured so that, during step c), said pins (33) come into contact with said protuberances (52), so that in step j) the casting blank (10') of the hollow turbine blade (10) directly integrates these channels (28) communicating with the outlet vents (30).

2. Manufacturing method according to the preceding claim, characterized in that each protuberance (52) defines the counterform of an outlet mouth (30) in the form of a flared bowl.

3. Manufacturing method according to the preceding claim, characterized in that each protuberance (52) extends along a main elongation axis (X) and has at least: - a first substantially trapezoidal face (60) having a large base (62) contiguous with the internal wall (36) of the mold (34) and a height oriented parallel to the main elongation axis (X), this first face (60) being inclined at an angle (oc) less than 30 degrees with the internal wall of the mold (34), - a second face (64) substantially rectangular, aligned with the first face (60) along the main elongation axis (X) and contiguous with a small base (66) of the first face (60), this second face being inclined at an angle (P) greater than 80 degrees and less than 90 degrees with the internal wall (36) of the mold (34), and - two third (68) and fourth (34) lateral faces which are substantially triangular bordering the first (60) and second faces (64), the first to fourth faces delimiting the counterform of the flared bowl.

4. Manufacturing method according to claim 3, characterized in that the pins (33) are oriented to touch the protrusions (52) at the junction of the first (60) and second faces (64) of the protrusions (52).

5. Manufacturing method according to one of claims 1 to 3, characterized in that it comprises, after the first molding phase (PH'1), a second machining phase (PH'2), which comprises a step k) during which a bottom of the outlet openings (30) of the casting rough (10') of the blade (10) is pierced to form said internal cooling channels (28).

6. Manufacturing method according to the preceding claim, characterized in that step k) is carried out by electroerosion using an EDM sinking tool (58) or by a drilling tool (58).

7. Manufacturing method according to the preceding claim, characterized in that, during step k), position and movement coordinates of the tool (58) are expressed in a reference frame comprising 3 reference points, these points all belonging to at least one outlet mouth (30).

8. Mold (34) made of refractory material for implementing a manufacturing method according to one of claims 1 to 7, characterized in that the protuberances (52) are formed in one piece with the internal walls (36) of the mold (34) made of refractory material.

9. Mold (34) made of refractory material for implementing a manufacturing method according to one of claims 1 to 7, characterized in that the protuberances (52) are attached and fixed to the internal walls (36) of the mold (34) made of refractory material.

10. Turbomachine blade (10) manufactured according to a method according to one of claims 1 to 7.

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