FR3072122A1 - TURBOMACHINE WHEEL - Google Patents

Abstract

The invention relates to a wheel comprising a disc (12) having at its periphery a plurality of substantially axial cells, a plurality of blades (32) whose feet (21) are axially engaged and retained radially in said cells and which have stilts (19) for connecting the feet (2) to plates (16) designed to delimit radially outwardly, an annular vein of a gaseous flow, sealing devices (36) mounted in internal cavities scaffolds delimited circumferentially between two stilts (19) adjacent. According to the invention, the sealing devices (36) each comprise at least one sealing wall (34) whose circumferential edges (34a, 34b) are arranged end to end with adjacent second ends of stilts (19). , said second ends of the stilts (19) being opposite the first ends of the stilts (19).

Description

TURBOMACHINE WHEEL

FIELD [001] The present invention relates to the field of leakage zones under the platforms of the blades of a bladed wheel in a turbomachine.

BACKGROUND [002] Typically, each blade of a turbine wheel comprises a blade connected at its radially internal end to a platform connected to a foot by a stilt. The grooves of the disc are regularly distributed around the axis of the disc and define between them teeth. In the mounting position, the platforms of the blades are arranged circumferentially one next to the other and surround the teeth of the disc. The longitudinal edges of the platforms of the blades are separated from each other in the circumferential direction by small clearances. It is known to mount sealing devices between the stilts of the blades which, in operation, are urged radially outwards by centrifugal forces and come to bear radially on the radially internal faces of the platforms to limit the leakage of gas between the longitudinal edges of the platforms. These sealing devices can also dampen the vibrations to which the blades are subjected in operation.

In the current technique, these sealing devices or members, sometimes called "candies", are engaged in lateral cavities of the blades, which are formed radially inside the platforms and which open in the circumferential direction. . Each sealing member includes a circumferential end portion engaged in the side cavity of a blade and an opposite circumferential end portion engaged in the side cavity of an adjacent blade.

To limit the reintroduction of air into the inter-blade or inter-stilt cavities, each stilt includes a transverse wall at each of its upstream and downstream ends. These transverse walls extend transversely to the axis of rotation of the turbomachine but are not necessarily radial. The upstream transverse walls are thus arranged end to end and the same is true of the downstream transverse walls. It is understood that the shape of each device is imposed by the shape of the blade, more specifically by the geometry of the cavity.

To install the wheel, the operator proceeds as follows. First of all, the operator engages a foot of dawn, from a downstream end for example, in a cavity of the disc. The operator then simultaneously mounts a vane / seal device pair and repeats this operation until the penultimate vane is assembled. The assembly of the last blade must be carried out at the same time as the two sealing devices on either side of the Pechasse of the blade. For this, know-how and technical training is necessary and it is common that the positioning of this latter blade requires as much time as the positioning of all the previously positioned blades.

SUMMARY OF THE INVENTION The present invention firstly relates to a wheel, in particular of a turbine for a turbomachine, comprising a disc having at its periphery a plurality of substantially axial cells, a plurality of blades whose feet are engaged axially. and retained radially in said cells and which have stilts connecting the feet to platforms intended to delimit radially outwards, an annular vein of a gas flow, sealing devices mounted in delimited inter-stilt cavities circumferentially between two stilts of two adjacent blades, and axially by transverse walls externally connected to the platforms and all formed at the same first end upstream or downstream of the stilts and cooperating together end to end to axially close said inter-stilt cavities, characterized in that said sealing devices include each at least one sealing wall, the circumferential edges of which are arranged end to end with second adjacent ends of stilts, said second ends of stilts being axially opposite the first ends of stilts.

According to the invention, at a first end of the stilts the sealing is carried out in a conventional manner by placing transverse walls end to end while at a second end of the stilts the sealing is carried out by a circumferential abutment of a sealing wall belonging to a sealing device with two adjacent second ends of adjacent stilts. This particular seal allows simpler mounting of the blades and sealing devices on the disc. Indeed, it is thus possible in a first step to mount all the blades on the disc by an axial engagement of the feet in the cells of the disc. In a second step, the operator assembles each of the sealing devices from the second ends of the stilts of the blades, this second step being made possible by the circumferential space left free between two second ends of stilts.

The assembly sequence of the blades and of the sealing devices on the disc is greatly simplified since it suffices to successively mount all the blades and then successively all the sealing devices without having to simultaneously manipulate a blade and a sealing device. sealing.

The term "transverse" denotes in this document a direction arranged across the axis of rotation of the moving wheel. Thus, a transverse wall is a wall whose definition plane intercepts the axis of rotation of the moving wheel, this wall not necessarily being purely radial but being able to be it.

Obviously, each of the second ends of the stilts could be connected to a transverse wall as in the prior art. However, this must then be sufficiently small circumferentially to allow the mounting of the sealing devices as described in the previous paragraph.

In a particular configuration of the invention, the second end of each stilt or at least some of the stilts has no radial wall.

According to another characteristic of the invention, the sealing wall of each sealing device comprises a radially external edge capable of coming, in operation, bearing radially outward on a spoiler extending the platform , to achieve a sealing in operation of the sealing device on a spoiler of the blade. Thus, in operation, the radially outer edge bears radially outward on a radially inner face of the spoiler.

According to yet another characteristic of the invention, the sealing devices include notches or notches opening out radially inwards and in which is engaged radially outwards an annular ring locked axially on one face of the disc.

This annular ring can be engaged in hooks carried by the second ends of the stilts of the blades.

In this assembly, the rod simultaneously ensures the axial locking of the blades and of the sealing devices.

[016] Each sealing device can be produced by stamping a sheet.

[017] The invention also relates to a turbomachine, such as a turbojet or an airplane turboprop, comprising a bladed wheel as described above.

It also relates to a method of mounting the wheel according to the invention, the method comprising the following steps:

- Axial engagement of each of the feet of the blades in the cells of the disc, from the first end of the stilts of the blades; and

- Engagement of each sealing device from the second end of the stilts.

In a subsequent step, the annular ring is mounted in the hooks of the stilts and the notches of the sealing devices.

The invention will be better understood and other details, characteristics and advantages of the invention will appear on reading the following description given by way of nonlimiting example with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a partial schematic half-view in axial section of a low-pressure turbine of a turbomachine according to the known technique;

Figure 2 is a schematic perspective view of the radially inner part of a blade of the turbine shown in Figure 1;

Figure 3 is a schematic side view of the blade of Figure 2 with a sealing device mounted in a cavity or inter-stilt housing;

Figures 4 and 5 are schematic views of a blade intended for use in a turbine of a turbomachine according to the invention;

Figure 6 is a schematic side view of the blade of Figure 4 with a sealing device integrated in an inter-stilt cavity;

Figure 7 is a schematic perspective view of two adjacent turbine blades of a bladed wheel according to the invention, a sealing device being mounted in an inter-stilt cavity;

FIG. 8 is a schematic view showing the mounting of a sealing device in an inter-stilt cavity of a bladed wheel according to the invention.

DETAILED DESCRIPTION [021] Reference is first made to FIG. 1 which is a schematic half-view in section of a low-pressure turbine of a turbomachine, along a plane passing through the axis of rotation X of the turbine rotor in Figures 2 and 3 which illustrate in isolation a turbine blade. The invention is obviously applicable to other parts of the turbomachine where sealing devices as described below can be used for an inter-blade sealing function.

[022] The rotor of the low-pressure turbine comprises wheels 10 assembled axially to each other by annular flanges and each comprising a disc 12 carrying individual blades 14. These blades each comprise a blade 15 connected by a platform 16 and a stilt 19 to a foot 21 which is for example of dovetail or the like, and which is engaged in a longitudinal cell formed at the outer periphery of a disc 12 (figure 1). The cells or housing groove of the blade roots define therebetween teeth which are arranged opposite the platforms of the blades. The rotor is connected to the turbine shaft by means of a drive cone 17. Between the wheels 10 are annular rows of fixed vanes 18 which are mounted by suitable means at their radially external ends on a casing 21 of the low-pressure turbine. The fixed vanes 18 of each row are joined together at their radially internal ends by annular sectors 20 placed circumferentially end to end. Upstream and downstream circumferential sheets or flanges 22 are formed in axial projection on the annular sectors 20, and constitute baffles with other spoilers or circumferential flanges 24 upstream and downstream of the platforms of the blades 14, to limit the passage of combustion gases , coming from the combustion chamber upstream of the turbine, radially from the outside to the inside. The term "radially" in relation to the terms "internal" and "external" are to be interpreted with regard to the axis of the moving wheel or axis of rotation of the turbomachine. The terms "upstream" and "downstream" are to be interpreted in relation to the direction of flow of air through the wheel when the latter is integrated into a turbomachine.

[023] Each blade 14 also includes a first downstream transverse wall 26 formed at the downstream end or first end of Péchasse 19 and a second upstream transverse wall 28 formed at the upstream end or second end of Péchasse 19. As can be seen in FIGS. 2 and 3, these upstream 28 and downstream 26 transverse walls are connected radially outwards to the upstream and downstream edges, respectively, of the platform

16. The circumferential edges of the upstream transverse walls 28 are arranged end to end, that is to say juxtaposed circumferentially, and the same is true of the circumferential edges of the downstream transverse walls 26, in order to limit the reintroductions of hot gases into the inter-stilt cavities delimited by two stilts 19 consecutive or circumferentially adjacent.

As can be seen in FIG. 3, these inter-stilt cavities each house a sealing device 30 mounted for a part in a half-cavity of a blade 14 and for the other part in a half-cavity of a adjacent blade 14. These sealing members 30 make it possible by radial support on the internal faces of the platforms 16 to limit the reintroductions of hot gases between the interstices at the junction between two consecutive platforms 16.

[025] As mentioned above, the mounting of the sealing devices 30 and the blades 14 can prove to be difficult to carry out, making the assembly operation of a long and expensive wheel.

[026] Thus, according to the invention shown in Figure 4, it is proposed to remove the second transverse wall (Figure 5) of the blade 32, that is to say the upstream transverse wall 28 and keep the first transverse wall 26 and to carry out the circumferential sealing by a transverse wall 34 of each sealing device 36 (FIGS. 6 and 7).

[027] To this end, each sealing device 36 comprises a first end, here the downstream end, similar to that described in relation to the prior art and coming in axial opposite of two downstream transverse walls 26 abutted , placed end to end by their circumferential ends, of two adjacent vanes 32 and a second end, here the upstream end, which comprises a transverse sealing wall 34 whose circumferential edges 34a, 34b are arranged end to end with the seconds ends, here the upstream ends, of two adjacent stilts 19. Each sealing device 36 or “candy” can be produced by stamping a sheet whose sealing wall 34 upstream is thicker than the rest of the sheet and in particular the side walls 38 intended to cooperate with the side faces. stilts 19, the downstream veil 40 for abutment on the downstream transverse walls 26 and the upper veil 42 for connecting the lateral veils 38, the downstream veil 40 and the upstream sealing wall 34. As can be seen in FIG. 6, the sealing wall 34 of each sealing device 36 bears radially outward, in operation, on two adjacent spoilers 24 so as to provide a seal at this location between the two parts which was produced in the prior art by the transverse wall 28 which is omitted.

[028] Each sealing device 36 comprises a recess 44 at its second end intended to cooperate with the downstream end of two adjacent spoilers 24 to ensure that the sealing device 36 is held in the stilt cavity. Each sealing device 36 can be hollow internally so that the radially internal edges 38a of the side webs 38 and the downstream web 40 are free.

[029] For the purpose of axial locking of the sealing devices in the inter-stilt cavities, each of them comprises a notch 46 or a notch formed in the radially internal edge 38a of the side walls 38 (FIG. 6). As can be seen in FIG. 7, each second end, here the upstream end, of a stilt 19 comprises a hook 48 oriented radially inwards. An annular ring 50 is thus engaged radially outward in the notches 46 or notches of the sealing devices 36 and in the hooks 48 of the blades 32, the ring 50 coming to bear on the upstream or second face of the disc 12 ( similar to that shown in FIG. 1) for axially locking the sealing devices 36 and the blades 32.

The assembly of the blades and the sealing devices 36 on a disc 12 is carried out as follows. In a first step, all the blades 32 are successively mounted on the disc 12 by an axial translational movement of the feet 21 in the cells of the disc 12 from the first end or downstream end of the disc 12 to the second end or upstream end of the disc 12. In a second step illustrated in FIG. 8, the sealing devices 36 are successively mounted from the second end of the disc 12 by an axial movement oriented towards the first end and followed by a pivoting movement, the edges 34a, 34b walls 34 of the sealing devices 36 coming into circumferential relation to the second ends or upstream ends of two stilts 19 consecutive. The annular ring 50 then being mounted in the notches 46 of the sealing devices and the hooks 48 of the blades 19 as indicated with reference to FIG. 7.

If the invention has been described with reference to the figures, with the first end of the blade 32 formed at the downstream end of the blade 32 and the second end of the blade 32 formed at the upstream end of the blade 32, it is understood that the invention is applicable to reverse arrangements where the first end is formed at the upstream end of the blade 32 and the second end is formed at the downstream end of the blade 32 It is easily understood that the upstream / downstream placement of the first and second ends is a function of the axial mounting direction of the blades in the cells of the disc 12.

Claims (8)

1. Wheel, in particular turbine wheel, for a turbomachine extending longitudinally along an axis X comprising a disc (12) having at its periphery a plurality of substantially axial cells, a plurality of blades (32), the feet ( 21) are engaged axially and retained radially in said cells and which have stilts (19) connecting the feet (2) to platforms (16) intended to delimit radially outward an annular stream of a gas flow , sealing devices (36) mounted in inter-stilt cavities delimited circumferentially between two stilts (19) of two adjacent blades and axially by transverse walls (26) connected externally to the platforms (16) and all formed to the same first end upstream or downstream of the stilts, characterized in that said sealing devices (36) each comprise at least one transverse sealing wall é (34) whose circumferential edges (34a, 34b) are arranged end to end with second adjacent ends of stilts (19), said second ends of stilts (19) being axially opposite the first ends of stilts (19) . 2. Wheel according to claim 1, characterized in that the sealing wall (34) of each sealing device (36) comprises a radially external edge capable of coming, in operation, to bear radially outward on a spoiler (24) extending the platform (16). 3. Wheel according to claim 1 or 2, characterized in that the sealing devices (36) include notches (46) or notches opening radially inward and in which is engaged radially outward an annular ring ( 50) locked axially on one face of the disc (12). 4. Wheel according to claim 3, characterized in that the annular ring (50) is engaged in hooks (48) carried by the second ends of the stilts (19) of the blades (32). 5. Wheel according to one of claims 1 to 4, characterized in that each sealing device (36) is produced by stamping a sheet. 6. A turbomachine, such as a turbojet or a turboprop 5 of an airplane, characterized in that it comprises a wheel according to one of claims 1 to 5. 7. A method of mounting the wheel according to one of claims 1 to 5, comprising the following steps: Axial engagement of each of the feet (21) of the blades (32) in the 10 cells of the disc (12), from the first end of the stilts (19) of the blades (32); and Engagement of each of the sealing devices (36) from the second end of the stilts (19). 8. The method of claim 7 when it depends on the 15 claim 4, comprising a step of mounting an annular rod (50) in the hooks (48) of the stilts (19) and the notches (46) of the sealing devices (36).