ROTOR EQUIPPED WITH AXIAL STOP AND AIRCRAFT TURBOMACHINE
By integrating a downstream retaining wall into the blade root and incorporating ventilation channels, the design addresses the challenges of retaining ring installation and stress-related cracking, improving assembly efficiency and safety in turbomachines.
Patent Information
- Application Number
- FR2022006561
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2022-06-29
- Publication Date
- 2024-12-20
- Estimated Expiration
- 2042-06-29
AI Technical Summary
Turbomachine blades' retaining rings, particularly the downstream ring, are difficult to mount and prone to mechanical and thermal stress, leading to potential cracking and release of parts into the air stream, necessitating complex and costly engine removal for replacement.
The blades are designed with a downstream retaining wall integrated into the blade root, eliminating the need for a downstream retaining ring, and featuring ventilation channels for cooling and axial blocking, simplifying assembly and reducing weight.
This design simplifies assembly, reduces weight, and prevents cracking by eliminating the need for downstream retaining rings, enhancing operational safety and reducing maintenance complexity.
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Abstract
Description
Title of the invention: ROTOR EQUIPPED WITH BLADES WITH AXIAL STOP AND AIRCRAFT TURBOMACHINE Technical field
[0001] The present invention relates in particular to a rotor for an aircraft turbomachine, in particular a low-pressure turbine rotor. Prior art
[0002] Turbomachines generally comprise moving blades which equip fan rotors, compressor rotors or even turbine rotors.
[0003] [Fig. 1] illustrates in particular such a rotor or mobile wheel 10 of a turbine of a turbomachine equipped with mobile blades. Typically, each blade 20 of a turbomachine rotor, and in particular of a turbine or compressor rotor of a turbomachine, comprises an aerodynamic blade 22 connected by a platform 23 to a root 24.
[0004] The roots 24 of the moving blades are inserted into an annular disc 30 of the wheel 10. In particular, the roots 24 of the moving blades are then received in grooves 32 extending in a direction substantially parallel to the axis of rotation of the wheel, also called cells, formed at the outer periphery of the disc. The cells 32 are distributed regularly around the axis of rotation of the wheel of the turbomachine. The disc 30 further comprises teeth 34 also formed at the outer periphery of the disc. There is an alternation at the periphery of the disc between the teeth and the cells. In other words, two adjacent cells are separated by a tooth 34 of the disc 30, and two consecutive teeth are separated by a cell. [Fig.2] illustrates an enlarged view of the periphery of the moving wheel.
[0005] The cells are through-holes. As a result, the blades are generally axially blocked on their upstream and / or downstream faces by retaining rings. The terms "upstream" and "downstream" refer to a general direction of gas flow in the turbomachine.
[0006] In particular, in a low-pressure turbine of a turbomachine, the axial retaining rings of the blades are generally located upstream and / or downstream of the blade roots. As a result, they are subject to stresses that can cause gas leaks. In particular, the downstream retaining ring 40 is subject to more stresses than the upstream retaining ring, because it is subject to mechanical and thermal stresses that are greater, in particular because of the aerodynamic axial force that tends to push the blade downstream.
[0007] The downstream retaining ring 40 bears against a downstream face of the teeth of the disc 30 so as to extend radially and circumferentially through the cells of blade housing of this disc and form a downstream stop for the roots 24 of the blades 20. In this example, the retaining ring 40 comprises a radially external end housed in a hook 25 of the blades or a groove formed in the blades 24. In addition, a radially internal end of the retaining ring 40 is held in axial position by a movable ring 50, in particular by an upstream radial arm 52 of the movable ring. The movable ring 50 is fixed to two consecutive discs so as to be integral in rotation with them.
[0008] Furthermore, a downstream radial arm 54 of another movable ring 50 arranged upstream of the disc is held directly in abutment against an upstream face of the teeth of the disc to form an upstream stop for the roots 24 of the blades 20. In particular, the downstream radial arm 54 comprises a radially external end housed in a hook 25 of the blades or a groove formed in the blades 24.
[0009] As a result, during assembly, the retaining rings, particularly the downstream retaining ring, are often difficult to fit. Since there is very limited space to easily fit them between the blade hooks and the disc, they are often forced into place.
[0010] Furthermore, during operation, the retaining rings, and in particular the downstream retaining ring, are subjected to mainly radial and thermal mechanical stresses. As a result, the retaining rings may crack.
[0011] However, in the event of a crack in the retaining ring(s), the risks are multiple. Pieces of retaining ring may be released into the air stream, risking damage to the blades located downstream of the disk and in particular of the low-pressure turbine, in particular the moving blades of the seventh stage which are very sensitive to impacts.
[0012] Furthermore, in the event of a crack that is too large, there is a risk of the blades being released into the vein, since the ring no longer guarantees axial stopping.
[0013] In all cases, the retaining ring must be changed, which requires removing the engine, i.e. a very complex and costly operation, particularly in terms of time.
[0014] The invention aims to remedy at least in part these drawbacks. Summary of the invention
[0015] To this end, the invention relates to a rotor for an aircraft turbomachine, in particular a turbine rotor, comprising a plurality of blades and an annular disc extending circumferentially around an axis and carrying the blades, each blade comprising a root and a blade extending from the root, the disc comprising a plurality of cells arranged at the periphery of the disc, each configured to receive a bulb of a root of a blade.
[0016] According to the invention, each blade root comprises a retaining wall attached to a surface of the bulb of the blade root and extending radially from the platform beyond the bulb of the blade root, each retaining wall of a blade root comprises a first surface in contact with a face of the disc and a ventilation channel comprising an inlet orifice which opens into the cell and an outlet orifice which opens onto a second surface of the retaining wall opposite the first surface.
[0017] The invention thus makes it possible to achieve the aforementioned objective.
[0018] Indeed, each blade comprising a downstream retaining wall, it is possible to axially block the blade in the cell and to avoid the use of a downstream retaining ring. It is understood that the downstream radial wall can be made in one piece with the blade root.
[0019] In addition, due to the absence of the downstream retaining ring, it is also possible to remove the hook holding the downstream retaining ring of the blade. Thus, the blade, in particular the blade root and the internal platform, can have a simpler geometric shape. The manufacture of the blade is therefore less complex.
[0020] The assembly of the turbine stages, and in particular of the blades on the discs of the different turbine stages, is less complex and involves the use of a reduced number of elements. This results in a reduction in the weight of the moving wheel and consequently of the turbine.
[0021] The rotor according to the invention may comprise one or more of the following characteristics, taken in isolation from one another or in combination with one another in all technically possible combinations: - the downstream surface of the disk comprises open cavities, each configured to receive at least one retaining wall of a blade root; - each open cavity comprises a bottom, two side walls and a circumferential wall connecting the two side walls, the side walls and the circumferential wall transversely delimiting the open cavity and extending from the bottom, the shape of the open cavity being substantially complementary to the shape of the retaining wall of a blade root, at least one cell opening onto the bottom of the open cavity; - the disc comprises a plurality of teeth arranged on the periphery of the disc and extending radially outwards, each tooth being arranged between two consecutive cells of the disc, and each tooth comprising a shoulder extending along the axis of the rotor in the same direction as the side walls and the circumferential wall of the open cavity and forming at least one side wall of an open cavity; - the depth of each open cavity is substantially equal to the thickness of the retaining wall of a blade root housed in the open cavity, the depth and the thickness being the respective dimensions of the open cavity and the wall of retained along the rotor axis; - the downstream retaining wall has a thickness greater than or equal to 0.5 mm and less than or equal to 10 mm, preferably less than or equal to 5 mm; - the inlet ports have an inlet diameter and the outlet ports have an outlet diameter, the inlet diameter being less than or equal to the outlet diameter - the inlet ports and / or the outlet ports have a diameter greater than or equal to 0.5 mm and less than or equal to 10 mm, preferably less than or equal to 5 mm; - each inlet port is axially aligned with an outlet port; - for each blade, the retaining wall is formed in continuity of material with the blade root; - for each blade, the retaining wall is brazed or welded to the base of the blade.
[0022] The invention also relates to an assembly for an aircraft turbomachine, comprising a rotor according to the invention and as described previously and an upstream retaining ring.
[0023] The invention also relates to a turbine for an aircraft turbomachine comprising at least one rotor according to the invention and as described above or such an assembly. Preferably, the turbine is a low pressure turbine.
[0024] The invention also relates to a turbomachine, in particular for an aircraft, comprising at least one rotor according to the invention and as described above or at least one such assembly according to the invention and as described above or one such turbine according to the invention and as described above. Brief description of the drawings
[0025] The present invention will be better understood and other details, characteristics and advantages of the present invention will appear more clearly on reading the description of a non-limiting example which follows, with reference to the appended drawings in which: - [Fig.l], already described, is a half schematic view in longitudinal section of a part of a turbine of a turbomachine according to the prior art; - [Fig.2] is an enlarged view of the periphery of a rotor, in particular of the turbine of [Fig.l]; - [Fig.3] is a half axial (or longitudinal) sectional view of a turbomachine to which the invention can be applied; - [Fig.4] is a half schematic view in longitudinal section of a part of a turbine of a turbomachine according to a first embodiment of the invention; - [Fig.5] is an enlarged three-dimensional view of the root of a moving turbine blade according to the invention; - [Fig.6] is an enlarged three-dimensional view of the periphery of the rotor of [Fig.4]; - [Fig.7] is an enlarged three-dimensional view of the periphery of a rotor according to a second embodiment; - [Fig.8] is an enlarged three-dimensional view of the periphery of the rotor disc of [Fig.7]; - [Fig.9] is a half schematic view in longitudinal section of a part of a turbine of a turbomachine according to the second embodiment of the invention.
[0026] Elements having the same functions in different implementations have the same references in the figures. Description of the embodiments
[0027] The figures include a reference system A, R and C respectively defining axial (or longitudinal), radial and circumferential directions, orthogonal to each other.
[0028] [Fig.2] represents a half view in axial and partial section of a turbomachine of longitudinal axis A, in particular a double-flow turbomachine 60 to which the invention applies. Of course, the invention is not limited to this type of turbomachine.
[0029] Such a double-flow turbomachine 60 comprises, from upstream to downstream according to the direction of circulation of the air flow F, a fan 62, several modules such as a low-pressure (LP) compressor 64 followed by a high-pressure (HP) compressor 66, a combustion chamber 68, a high-pressure turbine 70 followed by a low-pressure turbine 72, which drive the corresponding LP or HP compressor, and a gas ejection system 74.
[0030] In the present invention, and generally, the terms “upstream” and “downstream” are defined in relation to the direction of circulation of the fluids in the turbomachine, and here along the longitudinal axis A.
[0031] The compressors 64, 66, the combustion chamber 68 and the turbines 70, 72 form a gas generator.
[0032] The turbomachine 60 comprises a primary vein 75 in which a primary aerodynamic flow “P” or hot flow circulates and a secondary vein 76 in which a secondary aerodynamic flow “S” or cold flow circulates around the primary vein 75. The primary and secondary veins 75, 76 are coaxial.
[0033] The terms "internal", "external", "radial" and "radially" are defined with respect to a radial axis R perpendicular to the longitudinal axis A around which the turbomachine extends. Thus, by "lower", "internal" or "internal", we will designate any positioning close to the longitudinal axis A in the radial direction while by “upper”, “outer” or “external”, we will designate any positioning further from the longitudinal axis A in the radial direction than the lower, inner or internal positioning.
[0034] The longitudinal axis A is the axis of rotation of the turbomachine 60 and of the low pressure turbine 72.
[0035] Each turbine, and in particular the low-pressure turbine 72, comprises one or more rotors or bladed wheels, each rotor corresponding to a stage of the turbine. Between each pair of adjacent rotors, the turbine comprises stator blades forming distributors.
[0036] [Fig. 4] represents a detailed view of a part of the low pressure turbine, in particular of a stage 100 of the low pressure turbine 72 according to a first embodiment and according to a plane passing through the longitudinal axis A which constitutes the axis of rotation of the rotor of this turbine 72. The invention is however not limited to the low pressure turbine 72 and can in particular be implemented in the high pressure turbine 70.
[0037] [Fig.4] shows a part of a rotor 110 corresponding to stage 100 of the turbine, a part of a distributor 112 and a part of a rotor 110a and a part of a rotor 110b respectively arranged upstream and downstream of the rotor 110 of stage 100. The rotor 110 and the rotor 110b are separated by the distributor 112.
[0038] The rotor 110 is formed of an annular disc 130 extending circumferentially around an axis (merged with the longitudinal axis of the turbomachine) on the periphery of which blades 120 are assembled. The blades 120 are distributed circumferentially around the disc 130.
[0039] A blade 120 of a turbomachine rotor, and in particular of a turbine rotor, generally comprises an aerodynamic blade connected by a platform to a root 124. The blade extends radially outward from the root 124.
[0040] More precisely, a foot 124 of a blade 120 comprises a bulb 126 and a stilt 127 extending radially from the bulb 126. The bulb 126 is connected to the stilt 27 by a neck 128. The latter corresponds to a portion of the bulb 126 which comprises a small section or a reduced thickness compared to the rest of the bulb 126. The bulbs of the blade feet may have a dovetail shape as in [Fig.5] or a fir tree shape.
[0041] The disc 130 comprises an upstream connecting ferrule 131 and a downstream connecting ferrule 132.
[0042] The disc 130 of the stage 100 is assembled to the disc of the upstream rotor 110a by means of a plurality of bolts 133 arranged in a circumferential direction C in orifices carried by a downstream connecting shell 132a of the disc of the upstream rotor 110a and by the upstream connecting shell 131 of the disc 130 of the stage 100.
[0043] Similarly, the disk 130 of the stage 100 is assembled to the disk of the downstream rotor 110b by means of a plurality of bolts 133 arranged in a circumferential direction C in orifices carried by an upstream connecting ferrule 131b of the disk of the downstream rotor 110b and by the downstream connecting ferrule 132 of the disk 130 of the stage 100. The bolts 133 also make it possible, on the one hand, to assemble an upstream movable ring 150a to the upstream rotor 110a and to the rotor 110 of the stage 100 and, on the other hand, to assemble a downstream movable ring 150b to the rotor 110 of the stage 100 and to the downstream rotor 110b.
[0044] In a known manner, each movable ring 150a, 150b comprises an upstream radial arm 151, an annular upstream portion 152, a radial fixing arm 153, a frustoconical downstream portion 154 and a downstream radial arm 155.
[0045] The upstream portion 152 of the movable ring 150a, 150b extends axially between the upstream radial arm 151 and the radial fixing arm 153.
[0046] The radial fixing arm 153 extends radially inward relative to the upstream portion 152 and the downstream portion 154 of the movable ring 150a, 150b. It extends axially between a radial arm 134, 134a of a downstream connecting shell 132, 132a of a disk of a rotor 110, 110a and a radial arm 135, 135b of the upstream connecting shell 131, 131b of a disk of an adjacent rotor 110b, 110 so as to be rotationally integral with the two adjacent rotors.
[0047] The downstream portion 154 of the movable ring 150a, 150b extends between the radial fixing arm 153 and the downstream radial arm 155. The downstream portion 154 carries sealing lips 156 which cooperate in sealing with a ring of abradable material 157 carried by the distributor 112.
[0048] The disc 130 of the rotor 110 of the stage 100 comprises at its periphery teeth extending radially outwards and grooves or cells for receiving the roots of the blades 120. The teeth circumferentially delimit between them grooves for housing blades. Each blade 120 is assembled on the disc 130 by inserting a blade root 124 into a blade root receiving cell. More precisely, the cells are each intended to receive a bulb 126 of the blade root and have a shape complementary to that of the bulb of the blade root.
[0049] [Fig.5] represents an enlarged three-dimensional view of the root of a moving turbine blade. According to the invention, each blade root 124 comprises a downstream retaining wall 170 attached to a downstream surface 128b of the bulb 126 of the blade root. Each downstream retaining wall 170 extends radially inward from the platform and beyond the bulb 126 of the blade root. Thus, each downstream retaining wall 170 has a radially internal end 172 which protrudes from the bulb 126, that is to say it extends radially inward from the bulb 126. In other words, this end 172 is a free end.
[0050] Preferably, the downstream retaining wall 170 is integral with the blade root.
[0051] Alternatively, the downstream retaining wall 170 may be brazed or welded to the bulb of the foot of dawn.
[0052] Advantageously, the downstream retaining wall 170 has a thickness, that is to say a dimension in the direction of the axis A of the rotor, greater than or equal to 0.5 mm and less than or equal to 10 mm, preferably less than or equal to 5 mm.
[0053] Each downstream retaining wall 170 is configured to axially block the blade root 124 in the cell as illustrated in [Fig. 6]. In particular, the axial blocking is achieved by abutting a downstream face 136b of the disk 130 against an upstream surface 174a of the downstream retaining wall 170.
[0054] Furthermore, the free end 172 of each downstream retaining wall 170 advantageously comprises a ventilation channel 175 adapted for ventilating the cell. The ventilation channel 175 comprises an inlet orifice 176 provided on the upstream surface 174a of the downstream retaining wall 170 and an outlet orifice 177 provided on the downstream surface 174b of the downstream retaining wall 170. The ventilation channel 175 opens into the cell via the inlet orifice 176.
[0055] The ventilation channel 175, the inlet orifice of which opens into each cell, makes it possible to ventilate each cell and thus to ensure efficient and uniform cooling of all the cells of the disc. In addition, the cooling of the disc is controlled by the dimensions of the outlet orifice of the ventilation channel.
[0056] Preferably, each inlet orifice 176 is axially aligned with the outlet orifice 177, that is to say that they are aligned in a direction parallel to the axis of rotation of the rotor 110. Alternatively, the inlet orifice may not be axially aligned with the outlet orifice.
[0057] In addition, the inlet orifices 176 and the outlet orifices 177 are circular in shape, the inlet orifices 176 have an inlet diameter and the outlet orifices 177 have an outlet diameter. Advantageously, the inlet diameter of the inlet orifices 176 is less than or equal to the outlet diameter of the outlet orifices 177. The ventilation channel 175 therefore has the shape of a right cylinder with a circular base whose axis is parallel to the axis A of the rotor when the inlet and outlet diameters are equal. When the inlet diameter of the inlet orifices 176 is less than the outlet diameter of the outlet orifices 177, the ventilation channel 175 therefore has a frustoconical shape whose axis is parallel to the axis A of the rotor. Preferably, the inlet orifices 176 and / or the outlet orifices 177 have a diameter greater than or equal to 0.5 mm and less than or equal to 10 mm, preferably less than or equal to 5 mm.
[0058] With reference to [Fig.5], the upstream radial arm 151 extends radially towards the outside relative to the upstream portion 152 of the movable ring 150. The upstream radial arm 151 comprises, at its radially outward end, a bearing portion. The latter bears on the radially inward end 174 of the downstream retaining walls 170 of the set of blades 120 of the rotor. More precisely, this bearing portion bears on the downstream face 174b of each downstream retaining wall 170 in order to keep the downstream face 136b of the disc 130 in abutment against the upstream surface 174a of the downstream retaining wall 170.
[0059] Thus, according to the invention, the rotor 110 no longer has a downstream retention ring and the blades 120 no longer require a downstream hook.
[0060] However, the blades 120 of the rotor 110 comprise an upstream holding hook 129 of an upstream retaining ring for axially locking the blades 120 in the cells. It will be noted that in the embodiment of [Fig.4], the downstream radial arm 155 of the movable ring 150 acts as an upstream retaining ring for the blades 120. Indeed, the downstream radial arm 155 comprises, at its radially outward end, a bearing portion. This bearing portion bears on the upstream face 128a of the bulbs of the blade roots and the upstream face 136a of the disc 130 in order to hold the roots of the blades 120 in the cells.
[0061] Figures 7 to 9 represent a second embodiment. [Fig. 7] is an enlarged three-dimensional view of the periphery of a rotor 210, in particular the periphery of a disk 230 of this rotor carrying the blades 120. The blades 120 are shown in [Fig. 5] and are identical to those of the rotor according to the first embodiment. In this second embodiment, only the disk 230 of the rotor 210 differs. Also, the elements common to the different embodiments are identified by the same reference numerals. An enlarged three-dimensional perspective view of the periphery of this disk 230 is shown in [Fig. 8]. [Fig. 9] is a half schematic view in longitudinal section of a part of a turbine of a turbomachine, in particular of [Fig. 7].
[0062] In this embodiment, the disk 230 has a downstream surface 136b comprising open cavities 280. Each open cavity 280 is configured to receive at least one downstream retaining wall 170 of a blade root and preferably a single downstream retaining wall 170 of a blade root. Each open cavity 280 has a bottom 281, two side walls 282, 283 and a circumferential wall 284 connecting the two side walls 282, 283. The bottom 281 extends in a plane transverse to the axis A of the rotor 210. In addition, at least one cell opens onto the bottom 281 of the open cavity 280. The side walls 282, 283 and the circumferential wall 284 transversely define the open cavity 280. The side walls 282, 283 extend radially outwardly from the circumferential wall 284. Furthermore, the side walls 282, 283 and the circumferential wall 284 extend from the bottom 281 downstream.
[0063] Thus, by open, it is meant that the cavity is open radially outward and downstream.
[0064] The shape of the open cavity 280 is substantially complementary to the shape of the downstream retaining wall 170 of a blade root.
[0065] Advantageously, each tooth 34 of the disc 230 comprises a shoulder 290 extending along the axis A of the disc downstream. This shoulder 290 forms at least one side wall 281, 282 of an open cavity 280. Thus, one of the side walls 281 of an open cavity 280 is formed by a shoulder 290 of one of the teeth 34 which delimit the cell for receiving the corresponding blade root and the other of the side walls 282 is formed by a shoulder 290 of the adjacent tooth 34 which also delimit the same cell. Thus, a shoulder 290 of a tooth 34 delimits both a side wall 281 of a first open cavity 280 and a side wall 282 of a second open cavity 280, the shoulder being arranged between the first and second open cavities.
[0066] Preferably, for each open cavity 280, the depth of the open cavity is substantially equal to the thickness of the downstream retaining wall 170 of a blade root housed in said open cavity, the depth being the dimension of the open cavity along the axis A of the rotor 230. The depth of the open cavity also corresponds to the thickness of the shoulders 290 which surround and delimit it.
[0067] With reference to [Fig. 9], the upstream radial arm 151 of the movable ring 150 comprises, at its radially outward end, a bearing portion. The latter bears on the radially inward end 174 of the downstream retaining walls 170 of the set of blades 120 of the rotor. More precisely, this support portion bears on the downstream face 174b of each downstream retaining wall 170 in order to keep the downstream face 136b of the disk 230 in abutment against the upstream surface 174a of the downstream retaining wall 170. As the thickness of the shoulders 290 is equal to the thickness of the downstream retaining wall 170 of a blade root housed in said open cavity, the support portion of the upstream radial arm 151 also bears on a downstream face 290b of the shoulders 290 of the disk 230 of the rotor.
[0068] Thus, according to the invention, the rotor 110 no longer has a downstream retention ring and the blades 120 no longer require a downstream hook.
[0069] In the embodiments described above, the retaining wall of each blade root is a downstream retaining wall attached to a downstream surface of the bulb of the blade root and this retaining wall comprises an upstream surface in contact with a downstream face of the disk. Of course, the retaining wall of each blade root may be an upstream retaining wall attached to an upstream surface of the bulb of the blade root and this retaining wall would comprise a downstream surface in contact with an upstream face of the disk.
Claims
Claims
1. A turbomachine assembly (60) comprising an upstream retaining ring (155) and a rotor (110; 210) comprising a plurality of blades (120) and an annular disc (130; 230) extending circumferentially around an axis (A) and carrying the blades, each blade (120) comprising a root (124) and a blade extending from the root and connected to the root by a platform, the disc (130; 230) comprising a plurality of cells (32) arranged on the periphery of the disc, each configured to receive a bulb (126) of a root of a blade (120), characterized in that each blade root (124) comprises a retaining wall (170) attached to a surface (128b) of the bulb of the blade root and extending radially from the platform beyond the bulb of the blade root, each retaining wall (170) of a blade root comprises a first surface (174a) in contact with a face (136b) of the disc (130;230) and a ventilation channel (175) comprising an inlet orifice (176) which opens into the cell (32) and an outlet orifice (177) which opens onto a second surface (174b) of the retaining wall (170) opposite the first surface.;
2. An assembly according to claim 1, wherein the face of the disc (230) comprises open cavities (280), each configured to receive at least one retaining wall (170) of a blade root.
3. An assembly according to claim 2, wherein each open cavity (280) comprises a bottom (281), two side walls (282, 283) and a circumferential wall (284) connecting the two side walls, the side walls and the circumferential wall transversely delimiting the open cavity (280) and extending from the bottom, the shape of the open cavity (280) being substantially complementary to the shape of the retaining wall (170) of a blade root, at least one cell (32) opening onto the bottom of the open cavity (280).
4. An assembly according to claim 3, wherein the disc (230) comprises a plurality of teeth (34) arranged on the periphery of the disc and extending radially outwards, each tooth being arranged between two consecutive cells (32) of the disc, and each tooth (34) comprising a shoulder (290) extending along the axis (A) of the rotor in the same direction as the side walls and the circumferential wall of the open cavity and forming at least one side wall (282, 283) of an open cavity.
5. Assembly according to one of claims 2 to 4, in which the depth of each open cavity is substantially equal to the thickness of the retaining wall of a blade root housed in the open cavity, the depth and the thickness being the respective dimensions of the open cavity and of the retaining wall along the axis (A) of the rotor.
6. An assembly according to claim 5, wherein the downstream retaining wall (170) has a thickness greater than or equal to 0.5 mm and less than or equal to 10 mm, preferably less than or equal to 5 mm.
7. An assembly according to any one of claims 1 to 6, wherein the inlet ports (176) have an inlet diameter and the outlet ports (177) have an outlet diameter, the inlet diameter being less than or equal to the outlet diameter.
8. An assembly according to any one of claims 1 to 7, wherein the inlet orifices (176) and / or the outlet orifices (177) have a diameter greater than or equal to 0.5 mm and less than or equal to 10 mm, preferably less than or equal to 5 mm.
9. An assembly according to any preceding claim, wherein each inlet port (176) is axially aligned with an outlet port (177).
10. Assembly according to any one of the preceding claims, in which for each blade, the retaining wall (170) is formed in continuity of material with the blade root (124).
11. An assembly according to any preceding claim, wherein for each blade, the retaining wall (170) is brazed or welded to the root (124) of the blade.
12. A turbine for a turbomachine comprising a turbomachine assembly according to any one of claims 1 to 11.
13. A turbine according to claim 12, wherein the turbine is a low pressure turbine (72).
14. Turbomachine (60) comprising an assembly according to any one of claims 1 to 11 or a turbine according to any one of claims 12 or 13.