FR3058917A1 - COMPOUND CORE OF FOUNDRY FOR A MULTI-CAVITY BLADE - Google Patents

Abstract

The invention relates to a foundry core (1) comprising: - a central core element (30), and - an intrados (40) or extrados core element (50), the upper part (32) of the core the intrados or extrados core element (40, 50) being thicker than the remainder of said core element (40, 50) so that at its upper portion (42, 52) it has a bead (44, 54).

Description

® FRENCH REPUBLIC

NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY © Publication number:

(to be used only for reproduction orders)

©) National registration number

058 917

61223

COURBEVOIE © IntCI ⁸

B 22 C 9/10 (2017.01), F 01 D 5/14

A1 PATENT APPLICATION

©) Date of filing: 18.11.16. © Applicant (s): SAFRAN AIRCRAFT ENGINES (© Priority: Simplified joint stock company - FR. @ Inventor (s): GUERARD CORALIE CINTHIA, BENI- CHOU SAMI KELIM and HUCHIN PATRICK EMILIEN (43) Date of public availability of the PAUL EMILE. request: 25.05.18 Bulletin 18/21. ©) List of documents cited in the report preliminary research: Refer to end of present booklet (© References to other national documents ® Holder (s): SAFRAN AIRCRAFT ENGINES Company related: by simplified actions. ©) Extension request (s): (© Agent (s): REGIMBEAU.

(□ 4) COMPLEX FOUNDRY CORE FOR A MULTI-CAVITY VANE.

FR 3,058,917 - A1 (£ y) The invention relates to a foundry core (1) comprising:

- a central core element (30), and

- a lower surface core element (40) or upper surface core element (50), the upper part (32) of the lower surface or upper surface core element (40, 50) being thicker than the rest of said core element (40, 50) so that it has, at its upper part (42, 52), a bead (44, 54).

FIELD OF THE INVENTION

The invention relates generally to the field of turbomachinery, and more particularly that of the turbine blades of these turbomachinery and their manufacture.

TECHNOLOGICAL BACKGROUND

The turbine blades are subjected to high thermal stresses due to the heat of the gases in which they are immersed at the outlet of the combustion chamber and need to be cooled in order to withstand these temperatures. They are for this hollow and crossed by internal cavities in which a cooling gas circulates, taken at the outlet of a stage of one of the compressors.

More specifically, a turbine blade of a turbomachine comprises an aerodynamic surface (or blade) extending between a blade root and a blade head. The blade has a leading edge configured to be placed facing the flow of hot gases from the combustion chamber of the turbomachine, a trailing edge opposite the leading edge and lower side walls (overpressure side) and upper surfaces (vacuum side) which connect the leading edge to the trailing edge.

The internal cavities extend over the height of the blade, between its leading edge and its trailing edge. They are supplied with cooling gas by pipes connecting them to the foot of dawn.

The evolution of turbine technologies, in particular high pressure, imposes an improvement in the cooling of the blade, in particular at the level of their lower and upper surfaces. It has therefore been proposed to produce multi-cavity blades comprising a central cavity, extending generally between the leading edge and the trailing edge of the blade, a lower cavity and an upper cavity, extending from one side and other of the central cavity near the lower and upper surfaces, respectively.

To produce these different internal cavities, which have complex shapes and whose geometry must be respected with great precision, the blades are conventionally produced by a technique known as the lost wax foundry. This technique consists schematically of making a wax dawn blank in which are embedded ceramic cores which reproduce the cavities to come. The wax dawn is then embedded in a shell, for example in refractory material, then the nuclei are eliminated by chemical means, leaving in their place the internal cavities and bathtub sought. Implementations of this method are in particular described in the documents FR 2 875 425, FR 2 874 186, or also FR 2 957 828 in the name of the Applicant.

îo The air flow allowing the internal cooling of the multicavity vane can be upward (from dawn to dawn) or downward (from dawn to dawn). The internal cavities cooled by a rising air flow must integrate dusting holes to allow the extraction of particles present in the cooling circuit.

However, given the manufacturing constraints of the blade, it turns out to be difficult to produce these dusting holes. More precisely, the geometry of the central cavity does not allow repeatability of the unblocking of the dusting hole during manufacture due to the accumulation of tolerances (thickness of the central cavity in the unblocking zone less than the total of the geometry (nominal size) of the dusting holes, of the shape tolerance of the dusting holes, of the location and orientation of the dusting holes and of the central cavity in the finished blade as well as of the manufacturing margin (thickness minimum for manufacturing internal cavities)).

SUMMARY OF THE INVENTION

An objective of the invention is therefore to propose a foundry core for the manufacture of a multi-cavity blade of a turbomachine, in particular of a movable blade of a turbine, making it possible to obtain a multi-cavity blade comprising cavities internal in which it is possible to form dusting holes by reducing the risk of defect in the quality of the blade and by respecting the criteria of the dimension chain and aerothermal problems while guaranteeing the mechanical strength of the blade.

For this, the invention provides a foundry core for the manufacture of a multi-cavity blade of a turbomachine having a leading edge and a trailing edge, in particular of a movable blade of a turbine, said core s' extending longitudinally along a foundry axis comprising:

îo - a first core element, configured to form a central cavity of the blade and configured to extend between the leading edge and the trailing edge of said blade, and

- a second core element configured to form a lower surface cavity of the blade or an upper surface cavity of the blade, the second core element having an upper part and extending at least partially along the first core element,

According to one aspect, the upper part of the second core element is thicker than the rest of the second core element, so that the second core element has, at said upper part, a bead.

Such a core is also advantageously supplemented by the following different characteristics taken alone or in combination:

the second core element is configured to form the lower surface cavity of the blade, the foundry core further comprising a third core element configured to form the upper surface cavity of the blade, said third core element having an upper part and extending at least partially along the first core element, opposite the second core element, the upper part of the third core element being thicker than the rest of the third core element so that the third element core has, at said upper part, a bead.

- a cumulative thickness of the assembly formed by the first core element and the second core element is constant over a height of said assembly.

- an increase in the thickness of the second central core element is progressive at the junction between the bead and the rest of the second core element.

- the external surface of the bead has a concave, elliptical, parabolic shape or the shape of a parametric surface.

the first core element has an upper part extending opposite the upper part of the second core element, and in which a thickness of the upper part of the first core element is less than a thickness of the rest of the first kernel element.

- the thickening at the level of a bead of a lower surface core element and / or of an upper surface core element is between and 75%.

the core further comprises a leading edge core element configured to form a leading edge cavity of the blade and a trailing edge core element configured to form a trailing edge cavity of the blade the blade, the first core member extending between the leading edge core member and the trailing edge core member.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics, objects and advantages of the present invention will appear better on reading the detailed description which follows, and with regard to the appended drawings given by way of nonlimiting examples and in which:

FIG. 1 is a perspective view of an exemplary embodiment of an assembly comprising a foundry core according to the invention and an additional core,

FIG. 2 is a detailed view of an upper part of the central core of the foundry core of FIG. 1,

FIG. 3 is a detailed view of an upper part of the lower surface core and of the upper surface core of the foundry core of FIG. 1, seen from a first side of the foundry core, and

FIG. 4 is a detailed view of the upper part of the lower surface core and of the upper surface core of FIG. 3, seen from the second side of the foundry core.

DETAILED DESCRIPTION OF AN EMBODIMENT

A foundry core 1 for the manufacture of a multi-cavity blade of a turbomachine will now be described with reference to the appended figures.

The blade obtained with such a foundry core 1 may in particular comprise a moving blade of a turbomachine, in particular a high pressure or low pressure turbine blade, more particularly a high pressure turbine blade.

As indicated above, the blade has a leading edge configured to be arranged facing the flow of hot gases from the combustion chamber of the turbomachine, a trailing edge opposite the leading edge and side walls lower surface (overpressure side) and upper surface (negative side) which connect the leading edge to the trailing edge. The blade further has a blade root, configured to be fixed on the rim of a disc of the turbomachine, typically of a turbine disc, and a blade head extending at the end opposite to the dawn foot.

In what follows, we understand by "height" the dimension of the blade extending between its foot and its head and by "thickness" the dimension of the blade which extends in a plane perpendicular to its height, c that is to say between its lower surface and its upper wall.

The blade is multi-cavity, that is to say that it includes several internal cavities including:

- a leading edge cavity and a trailing edge cavity, extending near the leading edge and the trailing edge of the blade, respectively,

- a central cavity, extending between the leading edge cavity and the 5 trailing edge cavity, and

- a lower surface cavity and a lower surface cavity, extending along the lower surface wall and the upper surface wall of the blade, respectively, on either side of the central cavity.

In one embodiment, the lower surface cavity and the upper surface cavity further extend between the leading edge cavity and the trailing edge cavity.

Optionally, the blade also includes, at the level of its head, a hollow form or bathtub which extends in the extension of its lower and upper walls. A bottom wall then extends between the bathtub and the rest of the dawn cavities in order to close said cavities.

The foundry core 1 is configured to obtain, for example according to a lost wax casting technique, such a multi-cavity vane. The foundry core 1 can be made of any material conventionally used in the lost wax foundry technique, and in particular ceramic.

For this purpose, the foundry core 1 extends longitudinally along a foundry axis X and comprises at least two elements of internal cores 10, 40, typically:

a first core element 30, configured to form a central cavity of the blade and configured to extend between the leading edge and the trailing edge of said blade, and

a second core element 40, 50 configured to form a lower cavity of the blade or an upper cavity of said blade, the second core element 40, 50 having an upper part 42, 52 and extending at least partially along the first core member 30.

Throughout the present text, the terms "upper" or "lower" are understood with respect to the orientation given in the figures.

The upper part 42, 52 of the second core element 42, 52 is thicker than the rest of the second core element 40, 50, so that the second core element 40, 50 has, at the level of said upper part 42, 52, a bead 44, 54.

In the following, the invention will be more particularly described in the case where the foundry core 1 comprises five internal core elements

10, 20, 30, 40, 50 of which:

a leading edge core element 10 configured to form the leading edge cavity of the blade and a trailing edge core element 20 configured to form the leading edge cavity of the blade,

a central core element 30, corresponding to the first core element 15 described above, extending between the leading edge core element 10 and the trailing edge core element 20 and configured to form the central cavity of dawn,

- a lower surface core element 40 configured to form the lower surface cavity of the blade and an upper surface core element 50, configured to form the upper surface cavity of the blade, the lower and upper surface core elements extending from both sides other of the central core element 30 and, where appropriate, between the leading edge core element 10 and the trailing edge core element 20.

The lower surface core element 40 or the upper surface core element 50 then corresponds to the second core element described above.

It will be noted that the spaces extending between the various internal core elements 10, 20, 30, 40, 50 are intended to form the walls of the dawn cavities following the lost wax process.

Furthermore, the invention will be more particularly described in the case where the leading edge core element 10, the trailing edge core element 20, the central core element 30, the core element lower surface 40 and upper surface core element 50 are separate and distinct core elements. This is not, however, limiting, the central core element 30 being able to be formed integrally and in one piece with the leading edge core element 10 and / or the trailing edge core element 20 ( in which case these core elements 10 and / or 20 are not distinct from the central core element 30) and / or formed integrally and in one piece with the lower surface core element 40 or the upper surface core element 50 (in which case these core elements 40 and / or 50 are not distinct from the central core element 30).

The central core element 30 can moreover be in a single part or comprise several distinct parts.

The foundry core 1 has an upper part 2 intended to form a part of the blade extending close to the head of the blade, and a lower part 3 opposite the upper part intended to form a part of the dawn extending near the foot of dawn. Thus, in what follows, the part of each internal core element 10, 20, 30, 40, 50 extending near the upper part 2 of the foundry core 1 will be designated by upper part 12, 22, 32, 42, 52 of this internal core element 10, 20, 30, 40, 50 while the part of each internal core element which extends close to the lower part 3 of the foundry core 1 will be designated by lower part 13 , 23, 43, 53, of this inner core element 10, 20, 30, 40, 50.

Similarly to dawn, we will designate by "height" of an inner core element 10, 20, 30, 40, 50 given the dimension of this inner core element 10, 20, 30, 40, 50 s' extending between its lower part 13, 23, 43, 53 and its upper part 12, 22, 32, 42, 52 and by “thickness” the dimension which extends perpendicular to the height of this internel core element O, 20, 30 , 40, 50. The height and the thickness of each internal core element 10, 20, 30, 40, 50 are therefore dimensions substantially parallel to the height and the thickness of the blade obtained using the foundry core 1.

In the case where the blade further comprises a bathtub, an additional core element 4 intended to form the bathtub is fixed to one of the internal core elements 10, 20, 30, 40, 50 of the foundry core 1, either directly (the additional core element 4 can for example be formed integrally with the foundry core 1), or by means of fixing rods. The space between the upper part 12, 22, 32, 42, 52 of the internal core elements 10, 20, 30, 40, 50 and the additional core element 4 is then intended to form the bottom wall of the dawn.

In order to allow dusting holes to be made, the upper part 42, 52 of the second central core element 40, 50 (which is configured, if necessary, to partially form the bottom wall of the bathtub) is locally thicker than the rest of the second core element 40, 50. The upper part 42, 52 of the second core element 40, 50 therefore has, at this region of greater thickness, a bead 44, 54. This thus makes it possible to '' widen the wall of the associated vane which delimits the corresponding intrados or extrados cavity in the zone adjacent to the head of the vane and allow the realization of the dusting holes, despite the thinness of the second core element 40, 50 on the rest of its height.

Preferably, both the lower surface core element 40 and the upper surface core element 50 have such a bead 44, 54.

In such a case, that is to say if the two cores have beads, these can be offset so as not to reduce the thickness of the first core too much.

In another variant, it is possible to provide that the second core element carries a bead and that the third core element carries a hollow, while the first core element carries respectively a hollow and a bead facing the two other elements.

In one embodiment, the thickness of the top 32 of the central core member 30 (i.e., the first core member) is less than that of the rest of the central core member 30, in the zone 32 of the central core element 30 which extends opposite the bead or beads 44, 54. The central core element 30 therefore has at least one recess 34 at its upper part 32. The hollow 34 extends opposite the bead or beads 44, 54. This thus makes it possible to compensate for the increase in thickness of the central core element 30 without appreciably impacting the cooling flow of the blade obtained with such a foundry core 1 and to respect a minimum thickness for the walls defining the central, intrados and extrados cavities of the blade obtained with the foundry core 1 of the invention (the thickness of these walls corresponding to the space extending between the element of central core 30 and the intrados 40 and extrados 50 core element or elements). Typically, for a multi-cavity vane of a high pressure turbine of a turbomachine, the minimum thickness of the wall defining the intrados and extrados cavities is between 0.6 mm and 1.0 mm.

An overall thickness of the assembly formed by the first core element 30 and the second core element 40, 50 is therefore generally constant over the height of said core elements 30, 40, 50, even at their upper part 32, 42, 52.

Preferably, when both the lower surface core element 40 and the upper surface core element 50 have a bead 44, 54, a hollow 34 is formed on either side of the central core element 30, that is to say in front of the bead 44 of the lower surface core element 40 and in front of the bead 54 of the upper surface core element 50: the central core element 30 then has a thickness that is partially reduced upper 32 which defines the two recesses 34 than at the rest of its height. This configuration makes it possible to improve the resistance of the blade obtained with the foundry core 1 and to meet the feasibility constraints of the blade.

In an embodiment illustrated in the figures, the elements of the leading edge 10, trailing edge 20, lower surface 40 and upper surface 50 elements can be connected to a common base 5 configured to form the foot of the blade. This base 5 is out of part in the sense that it does not correspond to any part of the final vane obtained with the core elements. These internal core elements 10, 20, 30, 40, 50 therefore have a generally similar height.

The central core element 30 can have a lower height than these internal core elements 10, 20, 30, 40, 50. In particular, the upper part 32 of the central core element 30 can 'extend generally at the same level as the central part of the other core elements 20, 30, 40, 50, thus allowing if necessary to participate in the formation of the bottom wall. However, the central core element 30 then has a lower part (not visible in the figures) which extends away from the lower part 13, 23, 43, 53 from the other internal core elements 10, 20, 30, 40, 50. For example, the height of the central core element 30 can be globally equal to two thirds of the height of the other internal core elements 10, 20, 30, 40, 50.

To do this, the central core element 30 can be connected, at its upper part 32 and / or its lower part, to the leading edge core element 10 and / or to the trailing edge core 20. For example, the central core element 30 can be connected to both the leading edge core element 10 and the trailing edge core element 20 at its lower part.

In an alternative embodiment (not illustrated in the figures), the central core element 30 can have a height similar to that of the other internal core elements 10, 20, 30, 40, 50 and be connected, like the other elements of internal cores 10, 20, 30, 40, 50, to the common base 5. Its lower part then extends near the lower parts 13, 23, 43, 53 of the other internal core elements 10, 20, 30, 40. 50.

The second core element 40, 50 has a generally constant thickness over its entire height outside of its bead 44, 54 and, where appropriate, of the part of the second core element 40, 50 which is fixed to the base.

In one embodiment, the general thickness (i.e. outside the recess (s) 34) of the central core member 30 is approximately 0.5 mm (to within 5%).

As indicated above, the recesses 34 can be distributed generally on either side of the central core element 30 so that the recesses 34 are centered with respect to the lower surface 40 and upper 50 core elements. In this case, the thickness of the intrados core elements 40 and 50 is greater at their upper part 42, 52 (at the beads 44, 54) than at the rest of their height. For example, a lower surface core element 40 typically has a thickness of the order of 0.7 mm over most of its height and a thickness of 1.2 mm at the level of a bead.

Similarly, an upper surface core element 50 typically has a thickness of 0.9 mm over most of its height and a thickness of 1.4 mm at the level of a bead.

The thickening at the level of a bead is therefore typically between 60 and 75%.

(apart from their upper part) and equal to 0.7 mm and 0.6 mm (to within 5%), respectively, the cumulative thickness of these core elements 40, 50 is equal to their height and can be between and ( to within 5%) at their upper part 42, 52.

The height of the bead or beads 44, 54 is preferably as low as possible to limit their impact on the cooling of the blade obtained with the foundry core 1 in comparison with a blade made with a conventional foundry core 1. However, it must be large enough to allow the production of dusting holes in the blade obtained, whatever the angle and the position of said dusting holes. For example, the height of the bead or beads 44, 54 can be of the order of 2% to 3% of the height of the corresponding core element 40, 50.

In order not to disturb the cooling flow in the cavities of the blade obtained using the foundry core 1, the transition between the bead 44, 54 and the rest of the central core element 40, 50 is progressive , that is to say smooth and without projection, so as not to generate a break in slope over the height of the core element 40, 50. The bead 44, 54 may for example have a concave, elliptical shape, îo parabolic or the shape of a parametrized surface, or any other shape without a slope break.

Similarly, when the upper part 32 of the central core element 30 is thinned, the transition between the recess (s) 34 defined by this thinned part and the rest of the central core element 30 is also progressive. Preferably, the shape of the recess (s) 34 is generally complementary to the shape of the part of the bead 44, 54 which extends opposite. The space extending between the bead 44, 54 and the opposite recess (s) 34 (as well as over the rest of the height of the core elements) is therefore generally of constant thickness.

The recesses 34 may have a convex, elliptical, parabolic shape or the shape of a parameterized surface. They can be produced by any machining technique capable of obtaining the desired dimensions.

Claims (8)

1. Foundry core (1) for the manufacture of a multi-cavity vane 5 of a turbomachine having a leading edge and a trailing edge, in particular of a movable blade of a turbine, said core extending longitudinally along an axis (X) of foundry (1) comprising: a first core element (30), configured to form a central cavity of the blade and configured to extend between the leading edge and the trailing edge of said blade, and a second core element (40, 50) configured to form a lower surface cavity of the blade or an upper surface cavity of the blade, the second core element (40, 50) having an upper part (42, 52) and extending at least partially along the first core member 15 (30), the foundry core (1) being characterized in that the upper part (42, 52) of the second core element (42, 52) is thicker than the rest of the second core element (40, 50 ), so that the second core element (40, 50) has, at said upper part (42, 52), a 20 bead (44, 54). 2. Foundry core (1) according to claim 1, wherein the second core element (40) is configured to form the lower surface cavity of the blade, the foundry core (1) further comprising a 25 third core element (50) configured to form the upper surface cavity of the blade, said third core element (50) having an upper part (42, 52) and extending at least partially along the first core element (30), opposite the second core element, the upper part (52) of the third core element (52) being thicker than The rest of the third core element (50) so that the third core element (50) has, at said upper part (52), a bead (54). 3. Foundry core (1) according to claim 1, in which a cumulative thickness of the assembly formed by the first core element (30) and the second core element (40, 50) is constant over a 5 height of said assembly. 4. Foundry core (1) according to one of claims 1 to 3, wherein an increase in the thickness of the second central core element (40, 50) is progressive at the junction between the bead îo (44 , 55) and the remainder of the second core member (40, 50). 5. Foundry core (1) according to one of claims 1 to 4, wherein the outer surface of the bead (44, 54) has a concave, elliptical, parabolic shape or the shape of a parameterized surface. 6. Foundry core (1) according to one of claims 1 to 5, wherein the first core element (30) has an upper part (32) extending opposite the upper part (42, 52) of the second core member (40, 50), and wherein a thickness of the top (32) 20 of the first core member (30) is less than a thickness of the remainder of the first core member (30). 7. Foundry core (1) according to claim 2, wherein the thickening at the level of a bead of a lower surface core element (40) 25 and / or an upper core element (50) is between 60 and 75%. 8. Foundry core (1) according to one of the preceding claims, further comprising a leading edge core element (10) configured to form a leading edge cavity of the blade and an element of a 30 trailing edge core (20) configured to form a trailing edge cavity of the blade, the first core element (30) extending between the leading edge core element (10) and the 'trailing edge core element (20). 305 893 ⁷ FtG.l 2/3