Method for manufacturing a turbine blade for a turbine engine

Abstract

The invention relates to a method for manufacturing a turbine blade for a turbine engine, comprising the following steps: • - forming a raw blade (10A) by casting, the raw blade having an external surface (18) and an internal surface (20) bounding a cooling cavity (22), and • - machining the raw blade by drilling orifices (28) in the raw blade from its external surface to the cavity, in predefined drilling zones (24). In the forming step, protruding members (26) are formed on the external surface of the raw blade, each protruding member being located in one drilling zone. In the machining step, drilling the orifices (28) completely removes the protruding members (26).

Description

TITLE: METHOD FOR MANUFACTURING A TURBOMACHINE TURBINE BLADE TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of turbomachine turbine blades and particularly to the manufacture of blades.

[0002] The present invention relates more particularly to a method of manufacturing a turbomachine turbine blade. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Conventionally, a turbomachine turbine blade is equipped with an internal cooling circuit allowing the blade to withstand the very high temperatures to which it is subjected during the operation of the turbomachine. The blade has an aerodynamic wall which extends between a root and a tip of the blade.

[0004] The cooling circuit includes: - a cooling cavity delimited by an internal surface of the blade wall, and - orifices passing through the wall and connecting the blade cavity to an air stream in which hot air from the combustion chamber of the turbomachine turbine circulates.

[0005] The blade is cooled by introducing cooled air into the blade cavity through its root, and then exhausting the air from the cavity through the holes in the wall into the air stream. The holes both supply the cavity with cooled air and cool the blade wall as the cooled air passes through it.

[0006] Generally, the manufacturing process of turbine blade includes: - a first stage of forming a raw 10A blade, by foundry, and - a second step, as shown in Figure 1, of machining the raw blade 10A by drilling orifices 28 passing through the wall 12 of the raw blade 10A to its cavity 22, by a drilling means 30, in predefined drilling zones 24.

[0007] Determining the actual position of each drilling zone 24 on the external surface 18 of the raw blade 10A comprises the following steps: - determination of the theoretical position of each drilling zone 24 by a thermal study of the blade to obtain optimal cooling of the blade, and - transfer of the theoretical position of each drilling zone 24 onto the external surface 18 of the raw blade 10A, relative to a reference frame of six points on the raw blade 10A.

[0008] However, the position of the reference points may be modified depending on the manufacturing tolerances of the raw blade wall or in the case of a retouch carried out on the external surface of the raw blade. Consequently, the modification of the position of at least one of the reference points results in a difference between the actual position and the theoretical position of each drilling zone on the external surface of the raw blade and therefore an inaccurate position of the orifices on the external surface of the blade. An inaccurate position of the orifices can alter the cooling of the blade by the cooling circuit. In addition, drilling the orifices in inaccurate drilling zones can cause impacts on the internal surface of the raw blade wall and consequently damage the wall. SUMMARY OF THE INVENTION

[0009] The invention provides a solution to the problems mentioned above, by proposing a method for manufacturing a turbine blade comprising a new step of forming the blade by casting.

[0010] A first aspect of the invention relates to a method of manufacturing a turbomachine turbine blade comprising the following steps: - forming a raw blade by casting, the raw blade comprising an external surface and an internal surface which delimits a cooling cavity, and - machining of the raw blade by drilling holes in the raw blade from its external surface to the cavity, in predefined drilling zones.

[0011] In the forming step, protruding features are formed on the outer surface of the raw blade, each protruding feature being located in a drilling area.

[0012] The manufacturing method according to the first aspect of the invention makes it possible, thanks to the formation of projecting elements on the external surface of the raw blade, to materialize the drilling zones. During the machining step, the projecting elements are then detected by the machining machine and then completely eliminated. Such a manufacturing method of the raw blade makes it possible to eliminate any difference between the actual position and the theoretical position of each drilling zone to ensure the correct positioning of the drillings of the blade orifices, and therefore the cooling of the turbine blade.

[0013] According to a first variant of the machining step, the drilling of orifices in the machining step is carried out by electroerosion.

[0014] According to a second variant of the machining step, the drilling of holes in the machining step is carried out by laser.

[0015] Advantageously, the manufacturing method comprises an additional step of applying at least one coating to the external surface of the raw blade, the step of applying at least one coating being carried out after the step of machining the raw blade. Such a feature makes it possible to avoid any damage to the coating during the machining step.

[0016] Advantageously, according to the second embodiment of the manufacturing method, the first coating is an anti-corrosion coating and the second coating is a thermal coating.

[0017] A second aspect of the invention relates to a raw turbine blade of a turbomachine comprising an outer surface and an inner surface which defines a cooling cavity. The raw blade comprises projecting elements distributed on its outer surface, each projecting element forming a piercing zone of the raw blade.

[0018] The raw blade according to the second aspect of the invention, thanks to the presence of projecting elements on its external surface, makes it possible to materialize the drilling zones of the raw blade.

[0019] According to a first embodiment of the raw blade, each projecting element has a half-sphere shape.

[0020] According to a second embodiment of the raw blade, each projecting element has a cylindrical rod shape. Such a geometry of the element in protrusion helps guide the drilling means by indicating the drilling direction during the machining stage of the manufacturing process in which the protruding element is completely eliminated.

[0021] A third aspect of the invention relates to a high pressure turbomachine turbine comprising a blade obtained by the manufacturing method according to the first aspect of the invention.

[0022] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0023] Other advantages and characteristics of the invention will appear on reading the following description, illustrated by the figures in which:

[0024] Figure 1, already described, is a partial schematic sectional view of a raw turbine blade according to the state of the art, during a machining step of the manufacturing process of a turbine blade;

[0025] Figure 2 is a schematic sectional view of a raw turbine blade according to a first embodiment of the raw blade;

[0026] Figure 3 is a partial schematic perspective view of a raw turbine blade of Figure 2;

[0027] Figure 4 is a schematic sectional view of a raw turbine blade according to a second embodiment of the raw blade;

[0028] Figure 5 is a partial schematic sectional view of a raw turbine blade according to the first embodiment of the raw blade, during the machining step of the manufacturing method of a turbine blade;

[0029] Figure 6 is a partial schematic sectional view of a raw turbine blade according to the second embodiment of the raw blade, during the machining step of the manufacturing method of the turbine blade;

[0030] Figure 7 is a partial schematic perspective view of a turbine blade, after the machining step of the turbine blade manufacturing process. DETAILED DESCRIPTION

[0031] An exemplary embodiment of the method for manufacturing a turbine blade according to the invention is described in detail below, with reference to the attached drawings. This example illustrates the characteristics and advantages of the invention.

[0032] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0033] For the understanding of the invention, an orthogonal reference frame XYZ indicated in the figures will be adopted, according to which the X and Y axes extend in a horizontal plane and the Z axis extends in a vertical plane, following the orientation in the figures. A foot towards a tip of a turbine blade is oriented according to the Z axis of the XYZ reference frame.

[0034] The manufacturing process of a 10B turbine blade includes: - a first stage of forming a raw 10A blade, by foundry, and - a second stage of machining the raw blade 10A, by drilling.

[0035] Figures 2, 3 and 4 illustrate a raw blade 10A obtained by the forming step of the manufacturing process. The raw blade 10A corresponds to the raw casting part and comprises: - an aerodynamic wall 12 which extends between a root 14 and a tip 16 of the raw blade 10A, the wall 12 being delimited by an external surface 18 and an internal surface 20, - a cooling cavity 22 delimited by the internal surface 20, and - projecting elements 26 distributed over the external surface 18 and each forming a drilling zone 24 of the raw blade 10A.

[0036] The wall 12 and the projecting elements 26 are formed simultaneously during the single step of forming the raw blade 10A.

[0037] The positioning of each of the drilling zones 24 on the external surface 18 of the raw blade 10A requires the determination of the theoretical position of the drilling zones 24 by a thermal study of the blade 10B to obtain optimal cooling of the blade 10B.

[0038] The step of forming the raw blade 10A by casting includes the following sub-steps: - manufacturing a wax model reproducing the raw blade 10A, i.e. the wall 12 with the projecting elements 26, - making a mold, for example ceramic, around the wax model, and - pouring the metal inside the mold.

[0039] Each projecting element 26 is formed by a local excess thickness of material, at the level of one of the drilling zones 24, so as to materialize the actual position of the drilling zones 24.

[0040] According to a first embodiment of the raw blade 10A, as shown in FIGS. 2 and 3, each projecting element 26 has a half-sphere shape.

[0041] According to a second embodiment of the raw blade 10A, as shown in FIG. 4, each projecting element 26 has the shape of a cylindrical rod 262. Each cylindrical rod 262 forms an angle a1 in the YZ plane relative to the external surface 18 of the raw blade 10A. The value of the angle a1 varies depending on the location of the row of projecting elements 26 on the raw blade 10A. For example, the angle a1 is approximately equal to 90° for the rows located in an upper portion of the raw blade 10A, and between 0° and 45° for other rows.

[0042] Furthermore, according to a variant not shown of the second embodiment, each cylindrical rod 262 can form an angle a2 in the XY plane and / or an angle a3 in the XZ plane, relative to the external surface 18 of the raw blade 10A. For example, the angle a2 is approximately equal to 45°.

[0043] Figures 5 and 6 illustrate the step of machining the raw blade 10A, by drilling orifices 28 in the raw blade 10A by a drilling means 30, in the projecting elements 26 forming the drilling zones 24 and up to the cavity 22 of the raw blade 10A. During the machining step, the drilling means 30 is placed directly on one of the projecting elements 26 to completely eliminate the projecting element 26 and form an orifice 28 at the drilling zone 24.

[0044] The drilling means 30 is for example a laser machining tool or an electro-erosion machining tool called electrical discharge machining (EDM). in English terminology. The machining step comprises a sub-step of calibrating the drilling means 30 relative to the projecting elements 26 of the raw blade 10A, before drilling the orifices 28.

[0045] During the step of machining the raw blade 10A according to its first embodiment, as shown in FIG. 5, when the drilling means 30 is placed on the protruding element 26 in the shape of a half-sphere 260, it can be directed at different angles relative to the external surface 18 (represented by the drilling means 30 in solid and dotted lines).

[0046] During the step of machining the raw blade 10A according to its second embodiment, as shown in FIG. 6, when the drilling means 30 is placed on the projecting element 26 in the form of a cylindrical rod 262, it is directed according to the angles a1, a2 and a3 relative to the external surface 18. Such a geometry of the projecting element 26 makes it possible to guide the drilling means 30 by indicating the direction of drilling of the wall 12 of the raw blade 10A.

[0047] Figure 7 illustrates a turbomachine turbine blade 10B, after the machining step of the manufacturing method, comprising several orifices 28 each arranged on one of the drilling zones 24, in place of one of the projecting elements 26 of the raw blade 10A.

[0048] The turbomachine turbine blade 10B comprises at least one coating applied to its outer surface 18. According to a particular example of the blade 10B, the blade 10B comprises a first coating applied directly to its outer surface 18 and a second coating applied to the first coating. Advantageously, the first coating is an anti-corrosion coating and the second coating is a thermal coating. The method for manufacturing the blade 10B therefore comprises an additional step of applying the coatings.

[0049] The coating application step is carried out after the raw blade machining step 10A.

[0050] The manufacturing method according to the invention makes it possible, thanks to the formation of projecting elements 26 of the forming step on the external surface 18 of the raw blade 10A, to guarantee the correct positioning of the drillings of the orifices 28 of the machining step. Consequently, the position of each orifice 28 of the blade 10B obtained by the manufacturing process corresponds to the actual position of the drilling zones 24, that is to say to the position allowing optimal cooling of the blade 10B.

Claims

CLAIMS

1. Method of manufacturing a turbomachine turbine blade (10B) comprising the following steps: - forming a raw blade (10A) by casting, the raw blade (10A) comprising an external surface (18) and an internal surface (20) which delimits a cooling cavity (22), and - machining the raw blade (10A) using a drilling means by drilling orifices (28) in the raw blade (10A) from its external surface (18) to the cavity (22), in predefined drilling zones (24), characterized in that the drilling of the orifice (28) completely eliminates the protruding element (26) during the forming step, protruding elements (26) are formed on the external surface (18) of the raw blade (10A), each protruding element (26) being located in a drilling zone (24).

2. Manufacturing method according to claim 1, characterized in that the drilling of orifices (28) of the machining step is carried out by electroerosion.

3. Manufacturing method according to claim 1, characterized in that the drilling of orifices (28) of the machining step is carried out by laser.

4. A method of manufacturing any one of the preceding claims, characterized: - in that it comprises an additional step of applying at least one coating to the external surface (18) of the raw blade (10A), - and in that the step of applying at least one coating is carried out after the step of machining the raw blade (10A).

5. Raw blade (10A) of a turbomachine turbine comprising an external surface (18) and an internal surface (20) which delimits a cooling cavity (22), characterized in that it comprises projecting elements (26) distributed over its external surface (18), each projecting element (26) forming a drilling zone (24) of the raw blade (10A). [Claim s] Raw turbine blade (10A) of a turbomachine according to claim 5, characterized in that each projecting element (26) has the shape of a half-sphere (260).

7. Raw turbine blade (10A) of a turbomachine according to claim 5, characterized in that each projecting element (26) has the shape of a cylindrical rod (262).

8. High pressure turbine of a turbomachine comprising a blade (10B) obtained by the manufacturing method according to claims 1 to 4.

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