Turbine wheel for turbomachine and set of wheel assemblies

Abstract

Movable wheel for turbomachine turbine and set of movable wheels The invention relates to a movable wheel (10a, 10b) for a turbomachine turbine, comprising: movable blades (110), a downstream part (200b) of a first turbine disc (200) comprising, at an external periphery, an axial retaining hook (210), an upstream part (300a) of a second turbine disc (300), positioned partially along the downstream part of the first disc and comprising, at an external periphery, an axial retaining fork (310), the root of each movable blade being arranged in a housing (180) delimited by the fork and the hook so as to axially block said blade root, and bolted connections (130) passing through the downstream part of the first disc and the upstream part of the second disc to clamp said downstream and upstream parts against each other. The invention also relates to a set of movable wheels and a method of mounting this set.Figure to be published with the abstract: Figure 3A.

Description

Title of the invention: Movable wheel for turbomachine turbine and set of movable wheels TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a turbine wheel of a turbomachine without a retaining ring and a movable ring. The invention also relates to a set of several of these movable wheels as well as a method of mounting such a set of movable wheels.

[0002] The invention finds applications in the field of aircraft turbomachines and, in particular, in the field of low pressure turbines of turbomachines. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] A turbomachine generally comprises several stages crossed by a primary air flow and a secondary air flow. These stages are generally a fan, a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine, a low-pressure turbine and a nozzle. The low-pressure turbine, also called a LP turbine, extends around an axis of rotation AA of the turbomachine and comprises a distributor formed of several fixed blades and several moving blades, mounted by their roots in disk cells centered on the axis AA.

[0004] An example of a moving wheel 100 of a conventional LP turbine is shown in [Fig.l]. An example of a set of several conventional moving wheels is shown schematically in [Fig.2]. A mobile wheel 100 generally comprises a disc 120 at the periphery of which several blades 110 are mounted. Each blade 110 comprises a blade 111 connected by a platform 112 to a central wall, or stilt 113, extended radially by a root 114. The LP turbine disc 120 is provided with grooves, called cells, positioned regularly on the periphery of the disc and intended to each receive the root 114 of a blade 110. The main functions of the disc 120 are to transmit the torque of the blades 110 to the shaft of the LP turbine (not shown in the figure), to position the blades in the secondary vein of the LP turbine and to provide support for sealing parts such as the mobile rings 150.

[0005] In a conventional architecture, such as that of figures 1 and 2, the blades 110 are axially blocked in the cells of a disk, upstream, by a retaining ring 140 and downstream by a movable ring 150. The retaining ring 140 is mounted along the stilts 113 of the movable blades 110 and held on the movable wheel by means of a locking hook 115. The locking hook 115 of the moving blade 110 extends axially from Péchasse 113 of said blade and covers an external end of the retaining ring 140.

[0006] Each LP turbine disc 120 comprises an upstream shroud 122 and a downstream shroud 123 both connected to a leek 121 extending radially between the shrouds 122 and 123. The downstream shroud 123 of a disc 120 is fixed to the upstream shroud 122 of a consecutive disc (i.e. the following disc in the direction of air flow) by means of a bolted connection 130. The movable ring 150 is arranged between the flanges 124 of the upstream shroud 122 and the flanges 125 of the downstream shroud 123 and extends to the Péchasse 113 of the blade 110. This movable ring 150, held on the movable wheel 10 by a flange 154 housed in the bolted connection 130 between the flanges 124 and 125 of the downstream and upstream ferrules, extends to Retaining Panel 140.Its function is, on the one hand, to axially block a retaining ring 140 and, on the other hand, to ensure sealing between the discs 120 thanks in particular to wipers 152 interfacing with an abradable 162 fixed on the fixed vanes 160 of the distributors opposite.

[0007] Such an architecture has many disadvantages both in operation and during assembly. Indeed, during assembly, the installation of the Retaining Panel 140 in the moving wheel 100 is often difficult because the environment is restricted and the parts are often integrated under constraints. In operation, due to these constraints and the alternating cycles of expansion and compression of the Retaining Panel 140, the latter tends to crack. However, in the event of a crack in the Retaining Panel, there are risks of pieces of the Retaining Panel being released into the air stream, which can damage the blades located downstream of the LP turbine, in particular the moving blades of stage 7 which are particularly sensitive to impacts. In the event of a very significant crack in the Retaining Panel, there is also a risk of the blades being released into the stream, since the Retaining Panel no longer guarantees the axial stopping of the moving blades.A crack in a retaining ring therefore results in the replacement of said retaining ring, which requires removal of the engine, which is costly in terms of labor time and downtime of the aircraft on which the turbomachine is mounted.

[0008] This architecture also has a drawback relating to the movable panel 150. Indeed, the movable panel 150 has the function of clamping the retaining panel 140 along the movable blades 110 to ensure the axial stopping of said blades. To put the movable panel in place, an operator applies a clamping force to the movable panel 150 which, under the effect of the clamping, deforms. However, this deformation under stress is not controlled with certainty, which can lead to losses of tension in the associated bolted connections.

[0009] This architecture presents yet another disadvantage when mounting the blades. mobile on the discs. Indeed, the installation of the mobile blades on the discs (called finning the discs) is a complex operation, long to implement since once the blades are positioned in the cells, it is necessary to ensure their blocking by installing both the retaining ring and the mobile ring and fixing the bolted connections through the two shell flanges and the flange of the mobile ring.

[0010] There is therefore a real need for a mobile wheel architecture allowing simpler and faster assembly of the mobile wheels and avoiding the risks associated with cracks. Summary of the invention

[0011] To address the above-mentioned problems of cracks in the retaining ring and complexity of mounting the moving wheels, the applicant proposes a moving wheel architecture in which the moving wheel is devoid of both retaining rings and moving rings. The moving wheel proposed by the applicant comprises an axial retaining hook at the periphery of one disc and an axial retaining fork at the periphery of another disc, the axial retaining hook cooperating with the axial retaining fork to hold both radially and axially the roots of the moving blades.

[0012] In the description, the term "exterior" designates the surfaces or parts of parts located furthest from the axis of rotation AA of the turbomachine, as opposed to the term "interior" which designates the surfaces and parts of parts closest to said axis AA.

[0013] Furthermore, the terms “upstream” and “downstream” are understood according to the direction of air flow, from the fan of the turbomachine towards the nozzle.

[0014] According to a first aspect, the invention relates to a mobile wheel for a turbomachine turbine, comprising: • moving blades each comprising a blade connected to a foot by a stilt, • a downstream part of a first turbine disc comprising, at an external periphery, an axial retaining hook, • an upstream portion of a second turbine disk, positioned partially along the downstream portion of the first disk and comprising, at an external periphery, an axial retaining fork, the root of each moving blade being arranged in a housing delimited by the fork of the upstream disk and the hook of the downstream disk so as to axially block said blade root, and • bolted connections passing through the downstream part of the first disc and the upstream part of the second disc to clamp said downstream and upstream parts against each other.

[0015]

[0016] This sprocket has the advantage of having neither a retaining ring nor a moving ring, which avoids the risk of circus in these parts. The absence of a retaining ring and a moving ring also reduces the mass of the sprocket and makes it easier to assemble. In addition to the characteristics which have just been mentioned in the preceding paragraph, the mobile wheel according to the first aspect of the invention may have one or more additional characteristics among the following, considered individually or according to all technically possible combinations: • on the one hand, the axial retaining fork of the upstream part comprises teeth arranged one after the other in a circular manner, two consecutive teeth forming between them a groove in which the Péchasse of one of the moving blades is arranged, and on the other hand, the axial retaining hook of the downstream part comprises a C-shaped section fitting a free end of the teeth of the fork of the upstream disc. • the housing in which the blade root is arranged extends radially between a surface of the C-section of the axial retaining hook and an underside of the teeth of the axial retaining fork and circularly between two grooves of said axial retaining fork. • each bolted connection is aligned with a moving blade in a substantially radial direction

[0017] A second aspect of the invention relates to a set of moving wheels for a turbomachine turbine, characterized in that it comprises several moving wheels according to the first aspect, positioned axially one after the other.

[0018] This set of mobile wheels has the advantage of improved mountability of the bolted connections and greater robustness of the LP turbine and therefore of the engine.

[0019] The set of moving wheels according to the second aspect of the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations: • it comprises at least a first and a second disc, each of the first and second discs comprising a downstream part and an upstream part connected to each other by means of a ferrule, the downstream part of the first disc and the upstream part of the second disc being secured to each other by a first series of bolted connections and together supporting a first series of moving blades. • the downstream part of the second disc and the upstream part of a third disc are secured to each other by a second series of bolted connections and together support a second series of moving blades. • the downstream part of the first disc comprises an upstream face provided with a bore and a substantially flat downstream face and the upstream part of the second disc comprises a substantially flat upstream face and a downstream face provided with a bore. • the bolted connections of the first series of bolted connections pass through the upstream part and the downstream part at right angles to the bores of said upstream and downstream parts, the substantially flat face of the downstream part being in contact with the substantially flat face of the upstream part. • the ferrule securing the downstream part of the first disc and the upstream part of the second disc has sealing lips adapted to be in contact with fixed blades of the turbine.

[0020] A third aspect of the invention relates to a turbomachine for aircraft, characterized in that it comprises a low pressure turbine equipped with a set of mobile wheels according to the second aspect.

[0021] A fourth aspect of the invention relates to a method of mounting a set of mobile wheels according to the second aspect, comprising the following operations: • installation, on a mounting support, of an upstream part of the second disc, • installation of moving blades in the axial retaining fork of the upstream part of the second disc, • installation, on the mounting support, of the downstream part of the first disc, the axial retaining hook of said downstream part fitting one end of the axial retaining fork of the upstream part so as to block the moving blades between the fork of the upstream part and the hook of the downstream part, • joining the downstream part of the first disc and the upstream part of the second disc by bolted connections, and • repeating operations a) to d) for each moving wheel of the set of moving wheels. BRIEF DESCRIPTION OF THE FIGURES

[0022] Other advantages and characteristics of the invention will appear on reading the following description, illustrated by the figures in which:

[0023] [Fig. 1], already described, represents a radial sectional view of a moving wheel according to the prior art;

[0024] [Fig. 2], already described, represents a radial sectional view of a set of moving wheels according to the prior art;

[0025] [Fig.3A] and [Fig.3B] each represent a schematic radial sectional view of a portion of a set of moving wheels according to the invention;

[0026] [Fig.4A], [Fig.4B] and [Fig.4C] represent different schematic views, in perspective, of the ends of the upstream and downstream parts of the first and second discs, between which is housed a blade of a mobile wheel according to the invention; and

[0027] [Fig. 5] represents, in the form of a functional diagram, the method of mounting a set of mobile wheels of the type of that of figures 3A and 3B.

[0028] In the figures, identical elements are identified by identical references. For reasons of readability of the figures, the size scales between elements represented are not respected. DETAILED DESCRIPTION

[0029] An exemplary embodiment of a set of mobile wheels according to a new architecture is described in detail below, with reference to the attached drawings. This example illustrates the characteristics and advantages of the invention. It is however recalled that the invention is not limited to this example.

[0030] An example of a set 10 of movable wheels according to the invention is shown in [Fig. 3A] in radial section, that is to say in the xy plane of the xyz reference frame where the x axis is the axis of rotation of the turbomachine, the y axis is the radial axis and the z axis is the tangential axis. In the example of [Fig. 3A], the set of movable wheels 10 comprises two movable wheels 10a, 10b; it is understood that the set of movable wheels 10 may comprise three, four or more movable wheels, the number of movable wheels depending in particular on the power desired for the LP turbine. Each moving wheel 10a, 10b comprises moving blades 110 arranged at the external ends of a downstream part 200b of a first disc 200 and of an upstream part 300a of a second disc 300. Each moving blade 110 comprises a blade 111, a root 114 and a stilt 113 connecting the blade 111 to the root 114.The moving blades 110 of the moving wheel 10a, 10b are substantially identical to the moving blades of the LP turbines of the prior art described previously, except that they are devoid of the locking hooks of the retaining ring and / or the moving ring.

[0031] Each moving blade 110 of a moving wheel 10a, 10b is mounted at the outer end of the upstream part 300a of the second disc 300, itself assembled with the downstream part 200b of the first disc 200. As shown in FIGS. 4A, 4B and 4C, the upstream part 300a of the second disc 300, more simply called the upstream part 300a, comprises a web 320 extended at its periphery 320a (also called the outer end) by an axial retaining fork 310 ensuring the positioning and partial holding of the moving blades within the moving wheel 10a, 10b. According to certain embodiments, the axial retaining fork 310 of the upstream part 300a (more simply called fork) comprises several teeth 311 arranged circularly one after the other and separated from each other by grooves 312. A tooth 311 is a projection made in one piece with the web 320 of the upstream part 300a and which extends axially at the external end of said web 320, in an upstream direction (i.e. in the -x direction). Each tooth 311 delimits two grooves 312 of the fork 310. Thus, in each set of two successive teeth, the two teeth 311 are separated by a groove 312. Each groove 312 is adapted to receive Péchasse 113 of a moving blade 110.

[0032] The downstream part 200b of the first disc 200, more simply called the downstream part 200b, comprises a web 210 extended at its periphery 210a (also called the external end) by an axial retaining hook 210 ensuring the maintenance of the moving blade 110 in the fork 310. According to certain embodiments, the axial retaining hook 210 (more simply called the hook) is a part manufactured in one piece at the external end of the web 220 and having a substantially C-shaped section, adapted to embed the end of the fork 310 and axially block the root 114 and Péchasse 113 of each moving blade 110 inside the fork 310. The hook 210 may comprise, for example: • a first axial wall 211 extending from the web 220 in an axial direction, parallel to the fork 310 of the upstream part 300a, • a radial wall 212 extending radially at the end of the first axial wall 211, and • a second axial wall 213 extending axially at the end of the radial wall 212, that is to say parallel to the first axial wall 211.

[0033] The first axial wall 211 extends over a length (along the x axis) at least equal to the length of the root 114 of a moving blade 110, the root 114 resting on this first axial wall. The second axial wall 213 extends over a length less than that of the first axial wall 211 and partially covers the teeth 311 of the fork 310 of the upstream part 300a; in other words, the second axial wall 213 extends axially from the radial wall until it covers the free end 311a of the teeth 311 of the fork 310. The second axial wall 213 extends at most up to the stilt 113 of the moving blade so as to axially block said stilt 113 in the groove 312 of the fork 310. The hook 210 of the downstream part 200b thus forms, with the fork 310 of the upstream part 300a, several housings 180 adapted to each receive a blade root 114.More precisely, the underside 313 of each pair of teeth 311 of the fork 310 and the surface 214 of the first axial wall 211 of the hook 210 delimit a housing 180, between the radial wall 212 of the hook 210 and the web 220 of the downstream disc 200. In other words, the housing 180 extends circularly between two grooves 312 of the fork 310 and radially between the surface 214 of the C-section of the hook 210 and the underside of two consecutive teeth 311 of said fork 310. This housing 180 is of dimensions adapted to receive the foot 114. of a moving blade 110, Péchasse 113 of this moving blade passing through the groove 312 located between two teeth 311 of the fork 310. Thus, the root 114 of each moving blade 110 is arranged in one of the housings 180 and Péchasse 113 of this moving blade extends through the groove 312 of the fork 310, the teeth 311 on either side of the groove 312 blocking the root 114 radially. Thus, the fork 310 and hook 210 assembly allows both the axial blocking of the moving blades and the radial blocking (or non-tilting) of said moving blades, which makes it possible to avoid the presence of the retaining rings of the state of the art and consequently offers a weight saving to the LP turbine.

[0034] The example of [Fig.3A] represents two movable wheels 10a, 10b of a set of movable wheels 10. The movable wheels 10a, 10b of the set of movable wheels 10 are mounted one after the other and each fixed to the preceding movable wheel. All the discs 200, 300 of a set of movable wheels 10 are identical and each comprise a downstream part 200b, also called a downstream leek, and an upstream part 200a, 300a, also called an upstream leek. The upstream part 200a of a first disc 200 is connected to the downstream part 200b of this same disc 200 by a ferrule 225. The ferrule 225 can, for example, be fixed, on the one hand, on the web 221 of the upstream part 200a of a disc, radially between the fork and the bore of this upstream part, and, on the other hand, on the first axial wall 211 of the downstream part 200b of the same disc.The ferrule 225 of each disc can be equipped with sealing lips 228 ensuring the interface with the abradables 162 of the fixed blades 160 of the distributors of the LP turbine, opposite the moving blades 110 of said turbine.

[0035] The downstream part 200b of the first disc 200 is secured to the upstream part 300a of the second disc 300, consecutive to the first disc 200, said downstream part 200b and the upstream part 300a secured together forming the support for the moving blades 110 of the moving wheel 10b. Indeed, as explained previously, the hook 210 of the downstream part 200b and the fork 310 of the upstream part 300a together ensure the axial and radial support of the moving blades 110 of a moving wheel. For this, the downstream part 200b and the upstream part 300a are secured to each other by means of a bolted connection 130 comprising, for example, a screw 131 and a nut 132. The tightening of the moving blades 110 is therefore carried out directly by the disks of the LP turbine, which avoids the presence of the moving rings of the state of the art (and consequently the hooks for holding the moving rings) and allows a reduction in the overall mass of the LP turbine.

[0036] [Fig. 3B] shows the movable wheel 10b of the movable wheel assembly 10 of [Fig. 3A]. In the examples of FIGS. 3 and 4, the bolted connection 130 is positioned in the internal part of the downstream part 200b and the upstream part 300a. In particular, each downstream and upstream part of a disc 200 or 300 comprises a web 220, 320 and a bore 230, 330. The web 220, the bore 230 and the hook 210 of the downstream part 200b can be manufactured in one piece. Similarly, the web 320, the bore 330 and the fork 310 of the upstream part 300a can be manufactured in one piece. The web 220 of the downstream part 200 has an upstream face 220a provided with a bore 230 and a substantially planar downstream face 220b. The web 320 of the upstream part 300a comprises, on the contrary, a substantially flat upstream face 320a and a downstream face 320b provided with a bore 330. The downstream face 220b of the web of the downstream part 200b is attached to the upstream face 320a of the web of the upstream part 300a, the bores 230 and 330 being arranged back to back. The bolted connection 130 passes through the webs 220 and 320, preferably at the location of the bores 230, 330.Thus, the bolted connections 130 of each movable wheel 10a, 10b are aligned in a substantially radial direction (y axis of the xyz reference) with a movable blade 110 (unlike the movable wheels of the prior art where the bolted connections are aligned radially with the fixed blades of the distributors). The securing of the sails 220 and 230 of the downstream 200b and upstream 300a parts makes it possible to move the bolted connections 130 away from the central axis AA of the engine and to bring them closer to the blade roots 114, which improves the clamping and the plating of the downstream 200b and upstream 300a parts and, consequently, of the first and second discs 200, 300.

[0037] A set of wheels 10 as shown in [Fig.3A] is mounted movable wheel by movable wheel, from the most downstream movable wheel (10b) of the set towards the most upstream movable wheel (10a). An example of a method 500 for mounting such a set of movable wheels 10 is shown in [Fig.5]. In this example, the method 500 comprises a first step 510 of installing an upstream part 300a of the second disk 300 on a mounting support. Indeed, if the movable wheels 10a, 10b are positioned radially around the central axis AA (i.e. in a yz plane) when they are in operation, their assembly is carried out horizontally (in an xz plane), outside the turbomachine, in an assembly workshop. Thus, the upstream portion 300a of the second disc 300 is arranged on a mounting support adapted to hold the second disc as well as all the other discs of the set of moving wheels.The moving blades 110 are then mounted one after the other in the fork 310 of the upstream part 300a (step 520). For this, Péchasse 113 each moving blade 110 is slid into one of the grooves 312 of the fork 310, the foot 114 of the moving blade then being positioned on one side of the teeth 311 of the fork while the blade 111 of said blade is positioned on the other side of said teeth.

[0038] The method 500 then comprises a step 530 of installing the downstream portion 200b of the first disk 200 on the mounting support, above the upstream portion 300a of the second disk. The positioning of the downstream portion 200b of the first disk is then adjusted (step 540) relative to the upstream part 300a of the second disc so that its hook 210 engages the end of the teeth 311 of the fork 310. The foot 114 of each of the moving blades 110 is then positioned in a housing 180 delimited, on the one hand, by the web 320 and two consecutive teeth 311 of the upstream part 300a and, on the other hand, by the first axial wall 211 and the radial wall 212 of the downstream part 200b, while the Péchasse 113 of each of the moving blades 110 extends through the groove 312 separating the two consecutive teeth 311 of the fork 310.

[0039] When the hook 210 is correctly positioned relative to the fork 310, the sails 320 and 220 respectively of the upstream 300a and downstream 200b parts can be secured by means of bolted connections 130, during a step 550 of mounting the bolted connections 130. The sails 320 and 220 are thus tightened against each other by means of several bolted connections 130, for example a bolted connection for a pair of mobile blades 110.

[0040] When all the bolted connections 130 are mounted, the downstream 200b and upstream 300a parts are clamped against each other so that the movable blades 110 positioned between the hook 210 and the fork 310 are locked in alignment with said secured upstream and downstream parts. A movable wheel, for example the wheel 10b of [Fig.3B], is then obtained (step 560). A fixed wheel 160 is then mounted (step 570), after each stage of movable wheels. The method 500 continues by repeating steps 510 to 570 until all the movable wheels 10a, 10b and fixed wheels 160 are assembled; in fact, steps 510 to 570 are repeated as long as the response to test 580 “are all the movable wheels mounted?” is negative. When the response to test 580 is positive, then the assembly of the wheel set is complete (step 590).

[0041] The method for mounting a set of mobile wheels 10 according to the architecture described above has many advantages. In particular, it makes it possible to improve the mountability of the bolted connections 130 by facilitating access to the areas where the bolted connections are positioned; in fact, as mentioned above, the bolted connections 130 of a mobile wheel 10a or 10b are distant from the central axis AA, compared to the mobile wheel architectures of the prior art, which facilitates their access and therefore their mounting. The mounting method 500 is, moreover, faster than that of the prior art because it requires the mounting of a reduced number of parts compared to the prior art (no more retaining ring or mobile ring) with simplified access to certain parts (such as the bolted connections).In addition to the assembly advantages, the movable wheel assembly described above avoids the use of crack-prone parts, such as the retaining ring, which could lead to disassembly and reassembly of the LP turbine; it thus improves the robustness of the LP turbine and, consequently, minimizes the . engine maintenance time.

[0042] Although described through a certain number of examples, variants and embodiments, the assembly of mobile wheels according to the invention, and its assembly method, include various variants, modifications and improvements which will be obvious to those skilled in the art, it being understood that these variants, modifications and improvements are part of the scope of the invention.

Claims

Claims

1. A movable wheel (10a, 10b) for a turbomachine turbine, comprising: - movable blades (110) each comprising a blade (111) connected to a root (114) by a stilt (113), - a downstream portion (200b) of a first turbine disk (200) comprising, at an outer periphery, an axial retaining hook (210), - an upstream portion (300a) of a second turbine disk (300), positioned partially along the downstream portion (200b) of the first disk and comprising, at an outer periphery, an axial retaining fork (310), the root (114) of each movable blade (110) being arranged in a housing (180) delimited by the fork of the upstream portion (300a) and the hook of the downstream portion (200b) so as to axially block said blade root, and - connections bolted (130) passing through the downstream part (200b) of the first disc and the upstream part (300a) of the second disc to clamp said downstream and upstream parts against each other.

2. A movable wheel according to claim 1, characterized in that: - on the one hand, the axial retaining fork (310) of the upstream part (300a) comprises teeth (311) arranged one after the other circularly, two consecutive teeth forming between them a groove (312) in which the Péchasse (113) of one of the movable blades is arranged, and - on the other hand, the axial retaining hook (210) of the downstream part (200b) comprises a C-shaped section encasing a free end of the teeth (311) of the fork (310) of the upstream part (300a).

3. A movable wheel according to claim 2, characterized in that the housing (180) in which the blade root (114) is arranged extends radially between a surface of the C-section of the axial retaining hook (210) and an underside of the teeth of the axial retaining fork (310) and circularly between two grooves (312) of said axial retaining fork.

4. A movable wheel according to any one of the preceding claims, characterized in that each bolted connection (130) is aligned with a movable blade (110) in a substantially radial direction.

5. Set of moving wheels (10) for a turbomachine turbine, characterized in that it comprises several moving wheels (10a, 10b) according to any one of the preceding claims, positioned axially one after the other.

6. A set of moving wheels according to claim 5, characterized in that it comprises at least a first and a second disc (200, 300), each of the first and second discs comprising a downstream part (200b) and an upstream part (200a, 300a) connected to each other by means of a ferrule (225), the downstream part (200b) of the first disc and the upstream part (300a) of the second disc being secured to each other by a first series of bolted connections (130) and together supporting a first series of moving blades (110).

7. A set of moving wheels according to claim 6, characterized in that the downstream part of the second disc and the upstream part of a third disc are secured to each other by a second series of bolted connections and together support a second series of moving blades.

8. A set of moving wheels according to claim 6 or 7, characterized in that: - the downstream part (200b) of the first disc comprises an upstream face (220a) provided with a bore (230) and a substantially flat downstream face (220b), and - the upstream part (300a) of the second disc comprises a substantially flat upstream face (320a) and a downstream face (320b) provided with a bore (330).

9. A set of moving wheels according to claim 8, characterized in that the bolted connections (130) of the first series of bolted connections pass through the upstream part (300a) of the second disc and the downstream part (200b) of the first disc at the bores (230, 330) of said upstream and downstream parts, the substantially flat face of the downstream part (200b) being in contact with the substantially flat face of the upstream part (300a).

10. A movable wheel assembly according to any one of claims 6 to 9, characterized in that the ferrule (225) securing the downstream part (200b) of the first disc and the upstream part (300a) of the second disc comprises sealing lips (228) adapted to be in contact with fixed blades (160) of the turbine.

11. Turbomachine for aircraft, characterized in that it comprises a low pressure turbine equipped with a set of moving wheels according to any one of claims 5 to 10.

12. A method of mounting a set of moving wheels according to any one of claims 5 to 10, comprising the following operations: a. installation (510), on a mounting support, of a part upstream (300a) of the second disc (300), b. installation (520) of mobile blades (110) in the axial retaining fork (310) of the upstream part (300a) of the second disc, c. installation (530, 540), on the mounting support, of the downstream part (200b) of the first disc (200), the axial retaining hook (210) of said downstream part encasing one end of the axial retaining fork (310) of the upstream part (300a) so as to block the moving blades (110) between the fork (310) of the upstream part and the hook (210) of the downstream part, d. securing (550) the downstream part (200b) of the first disc and the upstream part (300a) of the second disc by bolted connections (130), and e. repetition (570) of operations a) to d) for each moving wheel of the set of moving wheels.

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