Patent Application
20250083221
This disclosure relates to the field of turbomachine blades, in particular blades obtained by casting a molten alloy in a mold using a casting technique where material is removed, such as the lost wax casting technique for example.
Conventionally, the lost wax casting technique firstly consists of making a model out of wax or any other material that can subsequently be easily removed, of the part to be produced; this model comprises an internal part forming a ceramic core which represents the cavities that we wish to see created inside the blade. The wax model is then dipped several times in slurries composed of a suspension of ceramic particles in order to make a shell mold, through operations called stuccoing and drying.
The shell mold is then dewaxed, which is an operation through which the wax or material constituting the original model is removed from the shell. After this removal, a ceramic mold is obtained in which the cavity reproduces all the shapes of the blade and which still contains the ceramic core intended to generate the internal cavities. The mold then undergoes heat treatment at high temperature, or “firing”, which gives it the necessary mechanical properties.
The shell mold is then ready for manufacturing the metal part by casting. After verifying the internal and external integrity of the shell mold, the next step consists of pouring a molten metal into it, which fills the voids between the interior wall of the shell mold and the core, then solidifying the metal. In the field of lost wax casting, there are currently several solidification techniques and several casting techniques, depending on the nature of the alloy and the expected properties of the part that results from the casting. These may be directional solidification with columnar structure (DS), directional solidification with single crystal structure (SX), or equiaxed solidification (EX).
After the alloy is cast, the shell is broken off by a shaking operation. During another step, the ceramic core which remains enclosed in the obtained blade is removed chemically. The obtained metal blade then undergoes finishing operations which allow obtaining the finished part.
Examples of producing turbine blades using the lost wax casting technique are given in patent applications FR2875425 and FR2874186 of the applicant.
To form the wax model of the blade a wax injection mold or similar equipment is used, into which the core is placed, and then the liquid wax is injected through a channel provided for this purpose.
The search for increased engine performance implies a more efficient cooling of the turbine blades located immediately downstream of the combustion chamber. This requirement necessitates the formation of more elaborate internal cavities for the circulation of cooling fluid inside these blades. These blades have the distinctive characteristic of having several metal walls and therefore require the manufacture of increasingly complex ceramic cores.
Due to the complexity of the cooling cavities to be formed with their separating walls, and of their arrangement, one solution consists of producing the core in several parts which are assembled and glued together. The core parts are generally connected together at the foot and at the top. This is in fact about controlling the thickness of the walls and partitions formed at the time of casting, without affecting the geometry of the future cavities. The assembly must allow the core to withstand the stresses undergone during the steps of wax injection, dewaxing, and then casting.
It is therefore necessary to position the different core parts very precisely relative to each other in the wax injection mold and to ensure that the relative positions of the different core parts are maintained. Maintaining the different core parts as proposed in the current technique consists of fixedly connecting these core parts or elements to the ceramic shell.
In a context of designing a new blade having complex cavities, the retained solution consists of producing the core in two parts, in particular because of the complexity of the cavities forming the cooling circuit and the difficulties encountered in demolding the core from its injection mold. However, due to the too-small dimensions of the core parts and their complex geometry, it is impossible to connect these core parts together, for example by gluing, so that the core with its assembled parts can then be positioned in a wax injection mold system comprising a conventional isostatic positioning system with six support points.
The difficulty encountered is twofold, because on the one hand it requires very precisely positioning the different core parts in the wax injection mold and on the other hand positioning the different core parts relative to each other. Indeed, the two parts cannot each comprise their own conventional isostatic positioning system with six support points relative to the mold, because this would double the number of supports to be integrated into the wax injection mold, which is not possible in terms of the mold dimensions. In addition, as the two core parts are intertwined at some locations, certain points of isostatism cannot be placed within the wax injection mold. Therefore, simple positioning of the cores relative to the mold cannot enable a complete positioning of the cores relative to each other.
It is therefore understood that it is desirable to implement a different attachment of the cores to each other in the wax injection mold.
The disclosure aims in particular to provide a simple, effective and economical solution to the problems of the prior art described above.
For this purpose, the present disclosure proposes an assembly for producing a molding, made of removable material, of a turbomachine blade, comprising an injection mold for the removable material in which a first core element and a second core element are able to be mounted in a predetermined molding position, the first and second core elements extending in a first direction, the mold comprising:
Additionally or alternatively, the assembly may comprise the following features, taken alone or in combination:
According to another aspect, a method is proposed for producing a molding, made of removable material, of a turbomachine blade, the method comprising:
The method may further comprise the step of: positioning the first core element and the second core element on the first molding face such that the second retaining member comprises a first support point at which it bears against the first core element and a second support point at which it bears against the second core element, the mold further comprising a second retaining member extending from the first molding face in the second direction.
Other features, details and advantages will become apparent upon reading the detailed description below, and upon analyzing the attached drawings, in which:
The terms “upstream” and “downstream” used below are defined in relation to the direction of flow of gases through a turbomachine, indicated by arrow F in
Paired core elements 21, 22 extend in three perpendicular directions, a first direction Z, hereinafter designated longitudinal direction Z corresponding in the final blade to the longitudinal direction connecting the root to the tip of the blade, a second direction Y, hereinafter designated transverse direction Y, passing through the pressure-side and suction-side faces of the blade, and a third direction X, hereinafter axial direction X, corresponding in the final blade to the upstream/downstream direction (arrow F). In
Trailing core element 21 further comprises a notch 32 in its downstream edge 30. Notch 32 is arranged in the area of head 25f. Notch 32 is substantially U-shaped, oriented so that the opening of the U-shaped concavity is oriented along axial direction X.
In particular, retaining members P1a, P1f, P2a, P2f, P3a and P3f allow leading core 22 element or trailing core element 21 of both core elements 21, 22 to be held in position along transverse direction Y. Retaining members P1a, P2a, and P3a are provided for holding leading core element 22 in position along transverse direction Y. Retaining members P1f, P2f, and P3f are provided for holding trailing core element 21 in position along transverse direction Y. Each of retaining members P1a, P1f, P2a, P2f, P3a and P3f extends from first molding face 20, in transverse direction Y. Each of these members bears against one of the two cores, which prevents movement of the cores along transverse direction Y.
In particular, retaining members P1a, P2a, P2f and P1f are arranged in the area of foot 26a, 26f of the cores. Retaining members P1a, P2a, P2f and P1f are aligned along axial direction X. Retaining members P1a, P2a, P2f and P1f are arranged near the free end 31a, 31f of the cores. In other words, retaining members P1a, P2a, P2f and P1f are arranged outside the free end of the cores, but in the area of foot 26a, 26f of the cores. Retaining members P1a, P2a, P2f and P1f end in a support surface for the respective core, each of these support surfaces being substantially flat. In addition, each of these support surfaces is substantially perpendicular to transverse direction Y. These surfaces are located outside the functional area.
Retaining members P3a and P3f are arranged in the area of head 26a, 26f of the cores. Retaining member P3a and retaining member P3f are offset along longitudinal direction Z. In other words, retaining members P3a and P3f are not aligned along axial direction X. Retaining members P3a and P3f end in a support surface for the respective core, each of these support surfaces following the shape of the area of contact with the core. In other words, for optimal support, the support surfaces of retaining members P3a and P3f follow the shape of the surface of the core area with which they are in contact.
Additionally and alternatively, the second molding face may comprise retaining members similar to the retaining members described above, so as to lock the cores in position along transverse direction Y.
First molding face 20 may further comprise retaining members P6a and P6f. Retaining members P6a and P6f allow leading core element 22 or trailing core element 21 to be held in position along longitudinal direction Z, for example. Each of these members respectively bears against leading core element 22 and trailing core element 21, which prevents movement of the cores along longitudinal direction Z. Retaining member P6a is provided for example to retain leading core element 22 in position along longitudinal direction Z. Retaining member P6a extends from the first molding face, in transverse direction Y. Retaining member P6a bears against lower cutout wall 272a of leading core element 22. Retaining member P6f is provided, for example, for holding trailing core element 21 in position along longitudinal direction Z. Retaining member P6f extends from the first molding face, in axial direction X, in the downstream to upstream directional orientation. Retaining member P6f comes to rest in notch 32 of downstream edge 30 of trailing core element 21.
Alternatively, a retaining member P6′f may be provided instead of retaining member P6f. Retaining member P6′f is provided for holding trailing core element 21 in position along longitudinal direction Z. Retaining member P6′f extends from first molding face 20, in transverse direction Y. Retaining member P6′f bears against lower cutout wall 272f of trailing core element 21. In addition, retaining members P6a and P6′f are arranged so that the cutouts of the two cores are substantially aligned along axial direction X.
Only one of the two retaining members P6f and P6′f is used for the production of the wax molding, to position trailing core element 21 in longitudinal direction Z. Depending on the retaining member used, P6f or P6′f, the retaining member not in use is removed from the molding surface so as not to create a hyperstatic system. The choice of which point to use depends on the distribution of the desired expansion of the two cores during casting of the alloy.
In fact, retaining member P6 allows distributing the expansion of trailing core element 21 along longitudinal direction Z, towards head 25f and towards foot 26f, while avoiding too much of a difference in length compared to leading core element 22, particularly in the event of very different expansions between the two cores. On the other hand, retaining member P6′f is advantageously used to control the dimensions of a so-called “bottom” wall of a squealer tip present in the final blade. The bottom wall of the squealer tip is physically realized by cutouts 27a, 27f of the cores, which form a portion filled with material in the final blade. The bottom of the squealer tip is substantially planar, and extends in transverse direction Y and axial direction X. Due to the fact that the cores do not touch one another, meaning that they are not in contact, a portion of material referred to as a residual wall of the squealer tip bottom, separates the squealer tip bottom into two parts arranged at different levels along longitudinal direction Z. Residual wall 26 extends in longitudinal direction Z, from the bottom of squealer tip. The height of the residual wall, in longitudinal direction Z, is a characteristic which must be controlled in order to meet the aerodynamic performance of the blade. Indeed, it is desirable that the height of the residual wall be as low as possible, so as to avoid, to the extent possible, too significant of a difference in level between the portions of the squealer tip bottom. Consequently, retaining member P6′f, associated with retaining member P6a, places cutouts 27a and 27f in the same plane in the cores, which makes it possible to obtain two parts of the squealer tip bottom which are substantially in the same plane perpendicular to longitudinal direction Z.
The first molding face further comprises retaining members P4 and P5. Retaining members P4 and P5 allow leading core element 22 or trailing core element 21 or both core elements 21,22 to be held in position along axial direction X. Retaining members P4 and P5 are retaining members common to the two cores, leading core element 22 and trailing core element 21. To this end, retaining members P4 and P5 each comprise a first support point at which it bears against the leading core and a second support point at which it bears against the trailing core. Retaining members P4 and P5 together prevent rotation of the cores around transverse axis Y. Each of retaining members P4 and P5 extends from the first molding face, in transverse direction Y.
Retaining member P4 (or first retaining member) may be arranged in the area of head 25a, 25f. Retaining member P5 (or second retaining member) may be arranged in the area of foot 26a, 26f at the connection to free end 31a, 31f. Retaining members P4 and P5 may further be aligned in longitudinal direction Z. Retaining members P4 and P5 are arranged in a non-functional zone, meaning external to the part.
Retaining member P4 can be seen in
Retaining member P5 can be seen in
In addition, retaining member P4 and/or retaining member P5 may be movable between a retaining position and a retracted position. In the retaining position, visible in
Alternatively, retaining member P4 and/or retaining member P5 may further comprise a spacing means D4, D5 between their first and second support points. The spacing means ensures a separation (or spacing) of a constant distance between the first and second support points, the separation distance being measured for example in axial direction X. More precisely, spacing means D4, D5 keeps the two cores spaced apart from each other without them being in contact, meaning without the cores touching each other. Given that the cores extend in the three spatial directions, the separation distance may be measured in longitudinal direction Z or in transverse direction Y. A spacing means is for example physically realized by the diameter of the retaining member. The retaining member may for example have a constant diameter along its entire length. According to another example, the retaining member may have a smaller diameter towards its free end, and a larger diameter towards its base (meaning towards the first molding face).
Alternatively, retaining member P4 and/or retaining member P5 may further comprise adjustment means for adjusting the position of the cores in the first molding face. For example, the adjustment means is an eccentric, which may be rotated around transverse direction Y in order to shift the two cores in the plane formed by the transverse and axial directions.
In another alternative, first molding face 20 may further comprise counter-braces, as illustrated in
Alternatively, although not illustrated, the elements described above for retaining member P4 may be applied to retaining member P5, and conversely the elements described above for retaining member P5 may be applied to retaining member P4. For this purpose, the first retaining member may be retaining member P5 and the second retaining member may be retaining member P4. Thus, the first support point and the second support point of first retaining member P5 may respectively be points P5a and P5f, and the first support point and the second support point of second retaining member P4 may respectively be points P4a and P4f.
We now describe a method for producing a molding, made of removable material, of a turbomachine blade, the method comprising:
Alternatively, the method may comprise: closing the mold while positioning on the core elements the second molding face, with at least one complementary retaining member.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2200251 | Jan 2022 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2023/050048 | 1/13/2023 | WO |
