METHOD FOR MANUFACTURING A TURBINE BLADE FOR A TURBOMACHINE

Abstract

TITLE: METHOD FOR MANUFACTURING A TURBOMACHINE TURBINE BLADE One aspect of the invention relates to a method for manufacturing a turbomachine turbine blade comprising the following steps: forming a blank blade (10A) by casting, the blank blade having an external surface (18) and an internal surface (20) which defines a cooling cavity (22), and machining the blank blade by drilling holes (28) in the blank blade from its external surface to the cavity, in predefined drilling zones (24). During the forming step, protruding elements (26) are formed on the external surface of the blank blade, each protruding element being located in a drilling zone. Figure to be published with the abstract: Figure 5

Description

Title of the invention: METHOD FOR MANUFACTURED A TURBINE BLADE FOR A TURBOMACHINE. 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 for manufacturing a turbine blade for a turbomachine. TECHNOLOGICAL BACKGROUND OF THE INVENTION

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

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

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

[0006] Generally, the process for manufacturing the turbine blade comprises: - a first step of forming a rough 10A blade, by casting, and - a second stage, as shown in [Fig.1], of machining the rough blade 10A by drilling the orifices 28 through the wall 12 of the rough 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 rough blade 10A comprises the following steps: - determination of the theoretical position of each drilling zone 24 by a thermal study of the turbine blade to achieve optimal blade cooling, and - reporting of the theoretical position of each drilling zone 24 on the external surface 18 of the rough blade 10A, relative to a reference of six points of the rough blade 10A.

[0008] However, the position of the reference points may be modified depending on the manufacturing tolerances of the blank blade wall or in the case of a rework performed on the external surface of the blank blade. Consequently, modifying the position of at least one of the reference points results in a discrepancy between the actual and theoretical positions of each drilling zone on the external surface of the blank blade, and therefore an inaccurate position of the holes on the external surface of the blade. An inaccurate position of the holes can impair the cooling of the blade by the cooling circuit. Furthermore, drilling holes in inaccurate drilling zones can cause impacts on the internal surface of the blank blade wall and consequently damage the wall. Summary of the invention

[0009] The invention offers 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 for manufacturing a turbomachine turbine blade comprising the following steps: - Forming of a rough blade by casting, the rough blade comprising an external surface and an internal surface which delimits a cooling cavity, and - Machining of the rough blade by drilling holes in the rough blade from its external surface to the cavity, in predefined drilling areas.

[0011] During the forming step, protruding elements are formed on the external surface of the raw blade, each protruding element being located in a drilling area.

[0012] The manufacturing process according to the first aspect of the invention makes it possible, through the formation of protruding elements on the external surface of the blank blade, to materialize the drilling areas. During the machining step, the protruding elements are then detected by the machining center and completely removed. Such a manufacturing process for the blank blade eliminates any discrepancy between the actual and theoretical positions of each drilling area to ensure the correct positioning 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 holes in the machining step is carried out by electro-erosion.

[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 process includes an additional step of applying at least one coating to the external surface of the blank blade, the step of applying at least one coating being carried out after the machining step of the blank blade. This 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 process, 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 rough turbine blade for a turbomachine comprising an external surface and an internal surface that defines a cooling cavity. The rough blade comprises projecting elements distributed on its external surface, each projecting element forming a drilling zone of the rough blade.

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

[0019] According to a first embodiment of the rough blade, each protruding element has a hemisphere shape.

[0020] According to a second embodiment of the rough blade, each protruding element has a cylindrical rod shape. This geometry of the protruding element allows the drilling means to be guided by indicating the drilling direction during the machining step of the manufacturing process in which the protruding element is completely removed.

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

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

[0023] Other advantages and features of the invention will become apparent from the following description, illustrated by the figures in which:

[0024] Fig. 1, already described, is a partial schematic cross-sectional view of a rough turbine blade according to the prior art, during a machining step of the process for manufacturing a turbine blade;

[0025] The [Fig.2] is a schematic cross-sectional view of a rough turbine blade according to a first embodiment of the rough blade;

[0026] The [Fig.3] is a partial schematic perspective view of a rough turbine blade of the [Fig.2];

[0027] The [Fig.4] is a schematic cross-sectional view of a rough turbine blade according to a second embodiment of the rough blade;

[0028] Fig. 5 is a partial schematic cross-sectional view of a rough turbine blade according to the first embodiment of the rough blade, during the machining stage of the turbine blade manufacturing process;

[0029] The [Fig.6] is a partial schematic cross-sectional view of a rough turbine blade according to the second embodiment of the rough blade, during the machining stage of the turbine blade manufacturing process;

[0030] Fig. 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 example of an embodiment of the method for manufacturing a turbine blade according to the invention is described in detail below, with reference to the accompanying drawings. This example illustrates the features and advantages of the invention.

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

[0033] For the purposes of understanding the invention, an orthogonal XYZ coordinate system, as shown in the figures, will be adopted, in which the X and Y axes extend in a horizontal plane and the Z axis extends in a vertical plane, with the orientation shown in the figures. A foot pointing towards a crest of a turbine blade is oriented along the Z axis of the XYZ coordinate system.

[0034] The method for manufacturing a turbine blade 10B comprises: - a first step of forming a rough 10A blade, by casting, and - a second machining stage of the raw blade 10A, by drilling.

[0035] Figures 2, 3 and 4 illustrate a rough blade 10A obtained by the forming step of the manufacturing process. The rough blade 10A corresponds to the as-cast part and comprises: - an aerodynamic wall 12 extending between a foot 14 and a top 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 - protruding elements 26 distributed over the external surface 18 and each forming a drilling zone 24 of the rough blade 10A.

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

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

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

[0039] Each protruding 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 rough blade 10A, as shown in figures 2 and 3, each protruding element 26 has a hemisphere shape.

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

[0042] Furthermore, according to an unrepresented variant 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, with respect to the external surface 18 of the rough blade 10A. For example, the angle a2 is approximately equal to 45°.

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

[0044] The drilling means 30 is, for example, a laser machining tool or an electrical discharge machining (EDM) tool. The machining step includes a substep of calibrating the drilling means 30 with respect to the protruding elements 26 of the blank blade 10A, before drilling the holes 28.

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

[0046] During the machining step of the rough blade 10A according to its second embodiment, as shown in [Fig.6], when the drilling means 30 is placed on the protruding element 26 in the form of a cylindrical rod 262, it is directed at the angles a1, a2 and a3 with respect to the external surface 18. Such a geometry of the protruding element 26 allows the drilling means 30 to be guided by indicating the direction of drilling the wall 12 of the rough blade 10A.

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

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

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

[0050]

[0051] The manufacturing process according to the invention, by forming protruding elements 26 in the forming step on the external surface 18 of the blank blade 10A, ensures the correct positioning of the holes 28 in the machining step. Consequently, the position of each hole 28 in the blade 10B obtained by the manufacturing process corresponds to the actual position of the drilled areas 24, that is, the position allowing optimal cooling of the blade 10B.

Claims

Demands

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

2. A manufacturing method according to claim 1, characterized in that the drilling of holes (28) in the machining step is carried out by electro-erosion.

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

4. A manufacturing method of 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 rough blade (10A), - and in that the step of applying at least one coating is carried out after the machining step of the rough blade (10A).

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

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