FAN ROTOR ASSEMBLY FOR TURBOMACHINE

Abstract

A fan rotor assembly (10) for a turbomachine, the rotor assembly (10) comprising a fan disc (12) extending around a longitudinal axis (A) of the rotor assembly (10) and at least one blade (50) mounted on said fan disc (12), wherein a radially external surface (18) of the fan disc (12) comprises a plurality of cells distributed around said longitudinal axis (A), the at least one blade (50) comprising a blade root engaged in one of said cells, wherein the blade root comprises an axial stop hook comprising a projecting part mounted axially fitted in a housing of the fan disc (12). Abstract figure: Figure 1

Description

Title of the invention: ROTOR FAN ASSEMBLY FOR TURBOMACHINE Technical field

[0001] The present disclosure relates to the field of fan rotor assemblies for turbomachines. Prior art

[0002] In a known manner, an aircraft turbomachine sucks in a flow of air at its upstream end which is then exhaled at high speed at its downstream end, thus creating the thrust necessary to move the aircraft forward.

[0003] In order to suck in said air flow, the upstream end of the turbomachine comprises an air inlet provided with an inlet cone and a fan.

[0004] The fan comprises a plurality of blades which are distributed circumferentially on a fan disc. The fan disc is mounted on a compressor shaft, in particular a low-pressure compressor (or "LP compressor"), which is rotated about its longitudinal axis by a turbine of the turbomachine. The fan disc and its blades then rotate integrally with the compressor shaft, which promotes the suction of the air flow.

[0005] The inlet cone is installed in the air inlet longitudinally in front of the fan, preferably centered on the longitudinal axis of the compressor shaft. A conical outer surface of the inlet cone forms an airflow flow surface that allows a portion of the airflow entering the turbomachine to be diverted toward the fan blades.

[0006] Certain critical events, such as bird ingestion or blade failure, may cause one or more of the blades to move violently upstream of the turbomachine. It is therefore necessary to provide a system in the turbomachine for retaining each blade.

[0007] In a known manner, the roots of the fan blades are retained in position on the fan disk from a retention system which comprises a front shroud screwed to an upstream face of the fan disk, a rotating spacer screwed onto a drum of the LP compressor, and one or more platforms retained between the front shroud and the rotating spacer. The retention system further comprises a plurality of locks for fixing each blade to the fan disk.

[0008] Such a retention system therefore has a high number of parts, which has many disadvantages. First of all, the high number of parts increases the risk of manufacturing and assembly defects. Then, the higher the number of parts, the greater the risk of manufacturing and assembly defects. The higher the number of interfaces between parts, the greater the need to control more clearances between parts. Clearances constitute aerodynamic steps or air recirculations that cause energy losses. Finally, certain contact areas, such as the one between the blade platform and the rotating spacer, are exposed to significant wear. Summary

[0009] The present disclosure improves the situation.

[0010] For this purpose, a fan rotor assembly for a turbomachine is proposed, the rotor assembly comprising a fan disc extending around a longitudinal axis of the rotor assembly and at least one blade mounted on said fan disc, in which a radially external surface of the fan disc comprises a plurality of cells distributed around said longitudinal axis, the at least one blade comprising a blade root engaged in one of said cells, in which the blade root comprises an axial stop hook comprising a projecting part mounted axially fitted in a housing of the fan disc.

[0011] The projecting part of the axial stop hook being mounted axially adjusted in the housing of the disc, axial displacements of the blade root are avoided. The blade root is thus retained in the rotor assembly from a retention system directly integrated in the blade, without the need to use additional parts, such as locks, which reduces the number of parts to be machined and assembled. The manufacture of the rotor assembly is thus simpler, faster and less expensive. In addition, the risk of manufacturing or assembly errors, such as forgetting to install certain locks, is reduced.

[0012] It is noted that the axial stop hook integrated into the blade makes it possible to retain the blade root in the rotor assembly, in particular in the fan disk, even in the event of critical events endangering the entire blade, such as the ingestion of a bird or the breakage of the blade.

[0013] In the present text, by "longitudinal" or "axial" is meant in a direction substantially parallel to the longitudinal axis of the rotor assembly, while by "radial" or "transverse" is meant in a direction substantially perpendicular to the longitudinal axis of the rotor assembly.

[0014] In this text, the term “adjusted” may be understood as a synonym for the terms “immobilized” or “blocked”, among others.

[0015] By rotor assembly is meant that each of the parts which form this assembly can be driven in rotation around the longitudinal axis of the assembly, whether directly or thanks to connections with other parts.

[0016] The fan disc may have an annular shape comprising a longitudinally extending cavity delimited radially by a radially internal part of the fan disc. The fan disc can thus be mounted around a compressor shaft, particularly a low-pressure compressor.

[0017] Each cell forms, for example, a groove on the radially external surface of the fan disc. Each cell may be rectilinear and may extend substantially axially along the entire length of the fan disc. The cells may be distributed regularly around the longitudinal axis of the rotor assembly. Thus, each cell may define, with the neighboring cell, a tooth which also extends substantially axially along the entire length of the fan disc. Furthermore, each cell may thus be delimited between two successive teeth.

[0018] The blade root is part of a respective blade which may further comprise a stilt and a blade. The stilt may be arranged radially between the blade root and the blade. According to a non-limiting example, the blade root, stilt and the blade are made from a single piece.

[0019] Each blade may be made of metallic or composite material, for example 3D woven composite.

[0020] The shape of each blade root may be complementary to the shape of each cell or adapted to introduce the blade root into the respective cell. For example, each blade root may have a fir tree or dovetail shape.

[0021] The housing is for example included in a side wall of one of the alveoli. The side walls of each alveolus correspond in particular to the wall of each tooth which delimits the groove formed by each alveolus. Each alveolus can therefore comprise two side walls. Preferably, each side wall of each alveolus comprises a respective housing.

[0022] Each housing may have a portion having an axial dimension substantially equal to an axial dimension of the projecting portion of the axial stop hook. Thus, axially adjusted mounting of the projecting portion of the hook is possible.

[0023] Each housing forms in particular a groove which is open, preferably over its entire extension, in the respective cell.

[0024] The axial stop hook extends for example in a plane substantially perpendicular to the axial direction.

[0025] The projecting portion of the axial stop hook projects, for example, in a direction substantially perpendicular to a plane comprising the axial direction and the radial direction.

[0026] According to one aspect, a radial clearance may be formed between a radially inner end of said blade root and a bottom wall of the respective cell, wherein a shim is installed in each cell so as to fill said radial clearance.

[0027] The shim therefore makes it possible to avoid uncontrolled movements of the blade in the radial direction. The shim can in particular be shaped to control the movements of the blade root during a critical event mentioned above. In such circumstances, the blade in question pivots under the impact, the blade root consequently pivoting in the disc cell. The blade, in addition to the rotational movement, can undergo a forward and then backward diving movement in reaction. The blade can undergo torsional and axial diving movements of different amplitudes. Thanks to the shim, the impact between the blade and the cell in these situations is limited, as some energy from this impact is absorbed by the shim. The risks of damage to the blade are thus reduced.

[0028] The shim may be made, at least partially, of an elastically deformable material. For example, the shim may comprise metal portions and semi-rigid elastomer portions. According to one example, the shim may be made of the same material as the blade.

[0029] The wedge may have a parallelepiped shape. In some cases, the wedge has a shape and dimension similar or identical to the bottom wall of the respective cell. In other cases, the wedge has a dimension smaller than the bottom wall of the respective cell.

[0030] According to one aspect, a radial dimension of said protruding portion of said hook may be less than a radial dimension of said radial clearance.

[0031] Also, when the radial clearance is formed, the projecting part of the axial stop hook is fully engaged in the second part of the housing. The retention of the blade in the rotor assembly is thus improved.

[0032] According to one aspect, a radial dimension of said projecting portion of said hook may be less than a radial dimension of said wedge.

[0033] Also, when the shim fills the radial clearance between the blade root and the bottom wall of the cell, it is ensured that the projecting part of the axial stop hook is fully engaged in the second part of the housing. The retention of the blade in the rotor assembly is thus improved.

[0034] According to one aspect, the assembly may further comprise at least one blade platform comprising a first end portion and a second end portion axially opposed, the first end portion comprising at least one radial retention hole or at least one radial retention notch, the second end portion comprising at least one pin projecting substantially axially and shaped to be received in a fitted or tight manner in a bore included in a compressor drum.

[0035] The at least one radial retention hole or the at least one radial retention notch may in particular be shaped to receive a means for fixing the platform to the fan disc. Advantageously, the member for connecting the fan disc to the inlet cone may also be used as a means for fixing the platform to the fan disc. This reduces the number of parts to be used in the rotor assembly. The hole and / or notch of each platform is therefore, for example, arranged so as to be opposite the cavity formed by the fixing hole and the complementary fixing hole. Each platform can thus be fixed to the fan disc using the same connecting member that connects the front cone and the fan disc. Each platform is therefore held radially in position on the fan disc, whether the turbomachine is rotating or stationary. In addition, this fixing of the platform can help to retain each blade in the fan disc in the event of a critical event. In particular, the connecting member connecting the platform to the fan disc and the inlet cone can be configured to work in shear in the event of a critical event.The forces due to this shear can be absorbed by the two adjacent connecting members, as well as by the rest of the connecting members of the rotor assembly. The forces exerted on the blade in the event of a critical event are thus distributed in the inlet cone, which limits the risk of loss or breakage of the blades.

[0036] From an aerodynamic point of view, each platform has the function of defining the flow path of the air flow. In addition, the platform is advantageously capable of resisting significant forces without deforming and while remaining integral with the fan disc which carries them.

[0037] Each platform can be an attached piece or, as will be detailed, be formed in one piece with each blade.

[0038] Each platform is mounted in the vicinity of the foot of the respective blade.

[0039] Each platform can be mounted in the gap between two neighboring blades. In this case, a first platform is adjacent to the intrados side of the blade, and a second platform distinct from the first is adjacent to the extrados side of the blade. Alternatively, each platform is arranged around the intrados and the extrados of the respective blade. For this purpose, each platform comprises a groove capable of introducing each blade into the respective platform. Thus, the interval between two neighboring blades is occupied by half of two neighboring platforms. Such a configuration is referred to herein as a "sock configuration".

[0040] According to a variant, the second end portion of each platform may be in contact with a rotating spacer of the rotor assembly, instead of being connected directly to the compressor drum. In particular, the contact between the rotating spacer and the second end portion of the platform may be a contact making it possible to maintain the platform in position axially and radially.

[0041] As indicated, each hole or notch may be shaped to receive a means for attaching the platform to the fan disc. The attachment means is, for example, a screw or a bolt. Each radial retention hole or radial notch retention thus makes it possible to block the axial and radial movements of the first end part of the platform, which allows the platform to withstand significant forces without deforming and while remaining attached to the fan disc which carries it.

[0042] The compressor is for example a low pressure compressor.

[0043] The bore included in the compressor drum is for example a through hole. Alternatively, the bore may be a blind hole.

[0044] According to one aspect, said at least one pin may comprise an annular notch cooperating with a wall of the compressor drum delimiting said bore.

[0045] The annular notch forms, for example, a recessed portion into which the wall of the compressor drum can engage. This makes it possible to maintain the pin in position relative to the compressor drum, which also locks the platform in position relative to the compressor drum. Locking the platform in position relative to the compressor drum also contributes to retaining each blade axially in position, even in the event of a critical event.

[0046] According to one aspect, the at least one platform may be formed integrally with one of the blades.

[0047] In particular, each platform may be formed as a single piece with a respective blade. Thus, each platform may be integrated with a respective blade, instead of forming a unitary part attached to the rotor assembly. The manufacture of the rotor assembly is thus simplified.

[0048] According to one aspect, said housing may comprise a first portion extending substantially parallel to said longitudinal axis and a second portion extending substantially transversely to said first portion.

[0049] The housing may thus have an L-shape. Advantageously, the first part of the housing extends from an upstream end of the fan disc. The projecting part of the axial retaining hook may in particular be mounted axially adjusted in the second part of the housing. For this purpose, the blade root may be introduced into the respective cell, with the blade being oriented from its root to its blade in the direction of the gravity force. In such a case, the projecting part of the axial retaining hook is initially engaged in the first part of the housing. The blade root may then be axially moved in the cell, which causes the axial displacement of the projecting part of the axial retaining hook in the first part of the housing. Once the projecting part of the axial retaining hook is radially opposite the second part, the gravity force would cause the radial displacement of the blade root in the respective cell.The blade root would therefore move radially away from the bottom wall of the cell, and the projecting part of the axial stop hook would be engaged in the second part of the housing, where it can be retained axially in a snug manner.

[0050] It is noted that the axial dimension of the projecting part of the axial stop hook and of the second part of the housing may be chosen so as to ensure that the projecting part of the axial stop hook is fitted snugly in the second part of the housing.

[0051] According to one aspect, the assembly may further comprise an inlet cone disposed about the longitudinal axis of the rotor assembly, wherein at least a first end portion of the inlet cone is clamped in a complementary first end portion of the fan disc.

[0052] Thus, the inlet cone and the fan disk are directly connected to each other, which eliminates the need to use the front shroud. Manufacturing the rotor assembly is thus faster, less expensive and simpler. Similarly, by eliminating the front shroud, the rotor assembly proposed here presents less risk of obtaining unusable parts, defective assembly, or failure in service. For example, eliminating the front shroud avoids having to machine holes for fixing the front shroud on the inlet cone or on the fan disk.

[0053] Furthermore, by eliminating the front ferrule, the weight of the rotor assembly is also reduced.

[0054] In addition, since the inlet cone and the fan disc are mounted tightly together, the additional aerodynamic step constituted by the front shroud of the prior art is eliminated, thus reducing the pressure losses in the rotor assembly. More precisely, thanks to the tight mounting of the inlet cone in the fan disc, a centering of the inlet cone in the fan disc is obtained, making it possible to reduce the aerodynamic steps.

[0055] The tight fitting of the first end portion and the first complementary end portion makes it possible to maintain the inlet cone radially in position relative to the fan disc. The tight fitting of the first end portion and the first complementary end portion also contributes to maintaining the inlet cone axially in position relative to the fan disc.

[0056] The tight fit between the first end portion and the first complementary end portion can be achieved by shrink fitting, which makes it possible to achieve centering between the fan disc and the nose cone with reduced radial clearance, thereby reducing the aerodynamic steps of the rotor assembly.

[0057] To enable the inlet cone to be tightly fitted into the fan disc, a cross-section of the first end portion may be substantially equal in shape and dimension to a cross-section of the complementary first end portion. In this text, "cross-section" means a section included in a plane extending transversely.

[0058] When the tight fitting of the inlet cone in the fan disc is obtained by shrink fitting, this can be achieved by heating the complementary first end portion, which expands, and then introducing the first end portion into the expanded first complementary end portion. Then, the first complementary end portion can be allowed to cool, causing it to contract so as to squeeze the first end portion. Alternatively, shrinking can be achieved by cooling the first end portion, which shrinks, and then inserting it into the first complementary end portion. In this case, as the temperature of the first end portion increases, it expands and squeezes into the first complementary end portion.

[0059] The first end portion and the first complementary end portion may have a substantially annular shape. In the present text, “annular” means any shape comprising a closed perimeter which delimits a cavity, whatever its section.

[0060] The inlet cone may further comprise a second end portion having a substantially conical shape that flares from upstream to downstream. In this text, the terms "upstream" and "downstream" are to be interpreted in relation to the direction of flow of an air flow drawn into the turbomachine and passing longitudinally through the turbomachine between its two ends.

[0061] The downstream end of the second end portion of the inlet cone may have a cross-section greater than the cross-section of the first end portion of the cone. An annular wall extending substantially radially may connect the first end portion of the inlet cone, in particular an upstream end of this first end portion, to the downstream end of the second end portion of the inlet cone. The cross-section of the downstream end of the second end portion of the inlet cone may also be greater than the cross-section of the complementary first end portion of the fan disk. The annular wall connecting the first end portion and the second end portion of the inlet cone may thus form a wall delimiting an upstream longitudinal end of each cell.

[0062] When the cross-section of the downstream end of the second end portion of the inlet cone is greater than the cross-section of the complementary first end portion of the fan disc, the annular wall connecting the first end portion and the second end portion of the inlet cone may form a wall delimiting an upstream longitudinal end of each cell.

[0063] In some cases, the first end portion of the inlet cone may comprise at least one fixing hole, and the first complementary end portion of the fan disc may comprise at least one complementary fixing hole. Each fixing hole may thus be arranged radially opposite one of the complementary fixing holes. A member for connecting the fan disc to the inlet cone may thus be installed in each first hole and each first hole com- additional.

[0064] The at least one fixing hole being radially opposite the complementary fixing hole, the connecting member extends for example substantially radially in a radial cavity formed by each fixing hole and each complementary fixing hole which are radially opposite each other. Also, thanks to the connecting member, the axial retention of the inlet cone relative to the fan disc is improved.

[0065] The connecting member may be a screw or a bolt, among others.

[0066] According to one example, the first hole and the first complementary hole are through holes having a substantially cylindrical shape.

[0067] In some cases, the first end portion may comprise an annular row of fixing holes distributed around the longitudinal axis of the rotor assembly, and the first complementary end portion may comprise an annular row of complementary fixing holes distributed around the longitudinal axis of the rotor assembly. Each fixing hole is then radially opposite a respective complementary fixing hole. A respective connecting member may therefore be installed substantially radially in the radial cavity formed by each fixing hole and each complementary fixing hole which are radially opposite each other. The axial retention of the inlet cone relative to the fan disk is thus improved.

[0068] The fixing holes and the complementary fixing holes may be distributed regularly around the longitudinal axis of the rotor assembly. Alternatively, the fixing holes and the complementary fixing holes may be distributed irregularly around the longitudinal axis of the rotor assembly.

[0069] In some cases, a nut is crimped into each fixing hole and / or into each complementary fixing hole. The nut allows the connecting member to be held in position inside the fixing hole and the complementary fixing hole. The nut may be an independent part connected to a wall of each fixing hole and / or each complementary fixing hole.

[0070] The nut may alternatively be made integrally with the wall of each fixing hole and / or each complementary fixing hole.

[0071] In some cases, a first nut may be crimped into each mounting hole and a second nut may be crimped into each complementary mounting hole.

[0072] According to another aspect, a turbomachine such as a turbojet or a turboprop is provided, comprising a rotor assembly as described above. The turbomachine thus has all the advantages of the rotor assembly presented above.

[0073] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which: Fig. 1

[0074] [Fig-1] shows a schematic longitudinal sectional view of a rotor assembly of a fan for a turbomachine according to a first embodiment. Fig. 2

[0075] [Fig.2] shows a partial perspective view of a fan disc of the rotor assembly of [Fig.l]. Fig. 3

[0076] [Fig.3] shows a partial perspective view of a detail of the fan disc of [Fig.2] in which blade roots, shown partially in dotted lines, are installed. Fig. 4

[0077] [Fig.4] shows a partial perspective view of an example blade for the rotor assembly of [Fig.l]. Fig. 5

[0078] [Fig.5] shows a schematic top view of a portion of the rotor assembly of [Fig.l] comprising an inlet cone, a fan disc and a blade installed in the fan disc. Fig. 6

[0079] [Fig.6] shows a schematic top view of a first example arrangement of a plurality of blades and a plurality of blade platforms for the rotor assembly of [Fig.l]. Fig. 7

[0080] [Fig.7] shows a schematic top view of a second example arrangement of a plurality of blades and a plurality of blade platforms for the rotor assembly of [Fig.l]. Fig. 8

[0081] [Fig.8] shows a schematic view in longitudinal section of a fan rotor assembly for a turbomachine according to a second embodiment. Fig. 9

[0082] [Fig.9] shows a schematic perspective view of an upper face of a platform for the rotor assembly of [Fig.l] or [Fig.8]. Fig. 10

[0083] [Fig. 10] shows a schematic perspective view of a lower face of the platform of [Fig.9]. Description of the embodiments

[0084] Reference is now made to [Fig. 1] partially showing a rotor assembly 10 of a fan for a turbomachine according to a first embodiment. As illustrated, the rotor assembly 10 extends along a longitudinal axis A.

[0085] The rotor assembly 10 may comprise a fan disc 12 and an inlet cone 14.

[0086] The fan disk 12 has a substantially annular shape comprising a radially inner surface 16 and a radially outer surface 18. As seen in [Fig. 2], the radially inner surface 16 and the radially outer surface 18 are connected to each other. For example, a substantially annular intermediate wall 20 connects the radially outer 16 and inner 18 surfaces. In a longitudinal section of the rotor assembly 10, the intermediate wall 20 forms a tab 22 extending for example substantially radially, as shown in [Fig. 1].

[0087] The radially inner surface 16 of the fan disk 12 delimits a cavity 24 shaped to receive a compressor shaft, for example a low-pressure compressor, not shown in the figures. The compressor shaft is configured to rotate about the longitudinal axis A. The fan disk 12 and the compressor shaft are connected to each other in rotation. Thus, the rotation of the compressor shaft makes it possible to drive the fan disk 12 integrally in rotation about the longitudinal axis A. All the other parts forming the rotor assembly 10 which are directly or indirectly connected to the fan disk 12 can also be driven in rotation about the longitudinal axis A integrally with the compressor shaft.

[0088] The fan disk comprises a substantially annular first upstream end portion 25. As will be detailed, the first upstream end portion 25 is shaped to tightly receive a first end portion 27 of the inlet cone 14. In the following, the first upstream end portion 25 of the fan disk 12 will be called the “complementary first end portion”, while the first end portion 27 of the cone 14 will be called the “first end portion”.

[0089] Advantageously, at least one hole 23 passes radially through the first complementary end portion 25 of the fan disc 12. In the following, the hole 23 will also be called a “complementary fixing hole”.

[0090] The radially outer surface 18 comprises a plurality of cells 26. Each cell 26 comprises a groove formed recessed on the radially outer surface 18 of the fan disc 12. The groove formed by each cell 26 may be rectilinear and may extend substantially axially along the entire length of the fan disc 12.

[0091] The cells 26 can be distributed regularly around the longitudinal axis A. Thus, each cell 26 can define with the neighboring cell 26 a tooth 28 which also extends substantially axially along the entire length of the fan disc. Furthermore, each cell 26 can thus be delimited between two successive teeth 28.

[0092] Each alveolus 26 comprises a first side wall 30, a second side wall 32 and a bottom wall 34. The first and second side walls 30, 32 correspond to the side wall of the two successive teeth 28 between which the alveolus 26 is formed.

[0093] The bottom wall 34 of each cell 26 is for example included in a plane substantially perpendicular to the radial direction. The first and second side walls 30, 32 are transverse to the bottom wall 34. In particular, the first and second side walls 30, 32 may be inclined relative to the radial direction. Alternatively, the first and second side walls 30, 32 may be parallel to the radial direction.

[0094] As can be seen from Figures 2 and 3, a housing 36 is formed in each of the side walls 30, 32 of the respective cell 26. The housing 36 forms in particular a groove which is open, preferably over its entire extension, in the cell 26. According to a non-limiting example, each housing 36 comprises a first part 36-1 substantially parallel to the axial direction and a second part 36-2 substantially transverse to the first part 36-1. As seen in Figures 2 and 3, the first portion 36-1 extends from an upstream end 37 of the fan disc 12. More specifically, the upstream end 37 is an upstream end of each tooth 28 of the disc 12. The housing 36 is therefore open at the upstream end 37 of the fan disc 12. In the figures, the second portion 36-2 extends from a downstream end of the first portion 36-1, without this being limiting. Also, in the figures, each housing 36 has an L shape.

[0095] Advantageously, the complementary fixing hole 23 is formed through one of the teeth 28. Preferably, a complementary fixing hole 23 is formed through each tooth 28. Thus, the fan disc 12 comprises an annular row of complementary fixing holes 23.

[0096] A downstream end portion of the fan disc 12 may comprise a plurality of portions 38 projecting radially from the radially outer surface 18 of the fan disc 12. Each portion 38 comprises a hole 39 for attaching the fan disc 12 to a compressor 40. The compressor 40 is for example a low-pressure compressor.

[0097] The hole 39 is in particular arranged axially opposite another hole (not shown) arranged in the compressor 40. Thus, a fixing means, preferably removable, such as a screw, can be installed in the hole 39 and the hole of the compressor 40 to fix the fan disc 12 to the compressor 40.

[0098] The inlet cone 14 comprises a first end portion 27 and a second end portion 29. The first end portion 27 is placed downstream of the second end portion 29.

[0099] The first end portion 27 advantageously has a substantially annular shape comprising a radially internal surface 42 and a radially external surface 44. The radially external surface 44 of the first end portion 27 has a shape and a dimension substantially equal to the first complementary end portion 25 of the fan disk 12. Thus, the first end portion 27 of the cone 14 can be tightly mounted in the first complementary end portion 25. As indicated previously, this tight mounting can be obtained by shrink fitting.

[0100] As already explained, the fact of tightly mounting the first end portion 27 of the inlet cone 14 in the fan disc 12 makes it possible to maintain the inlet cone 14 in position radially and axially in the fan disc 12 from a simpler, less expensive assembly using a smaller number of parts. The manufacture of the rotor assembly 10 is therefore simplified.

[0101] Furthermore, as also indicated above, this tight mounting makes it possible to eliminate aerodynamic steps in the rotor assembly 10, which makes it possible to reduce pressure losses. In addition, the tight mounting guarantees the centering of the inlet cone 14 in the fan disc 12, which also reduces the aerodynamic steps.

[0102] At least one fixing hole 45 passes substantially axially through the first end portion 27 of the cone 14. Preferably, the fixing hole 45 passes through the cone 14 from its radially external surface 44 to its radially internal surface 42. Advantageously, when the first end portion 27 of the cone 14 is tightly mounted in the fan disc 12, the fixing hole 45 is radially opposite the complementary fixing hole 23. Thus, the fixing hole 45 and the complementary fixing hole 23 form a radial cavity shaped to receive a connecting member 48. The connecting member 48 makes it possible to connect the fan disc 12 and the inlet cone 14 so as to improve the retention in axial position of the cone 14 relative to the disc 12. The connecting member 48 is preferably a removable connecting member, for example a screw or a bolt.

[0103] As indicated previously, the fan disc 12 may comprise an annular row of complementary fixing holes 23. In this case, the first end portion 27 is preferably traversed radially by a plurality of fixing holes 45 forming an annular row of fixing holes 45. Advantageously, the plurality of fixing holes 45 are arranged in the annular row so that, when the first end portion 27 of the cone 14 is tightly mounted in the fan disc 12, each fixing hole 45 is radially opposite one of the holes additional fixings 23.

[0104] In some cases, a nut 49 may be crimped into each fixing hole 45. The nut 49 may be an independent part connected to a wall of each fixing hole 49. The nut 49 may alternatively be made integral with the wall of the respective fixing hole 49.

[0105] The nut 49 makes it possible to hold the connecting member 48 in position inside the fixing hole 45 and the complementary fixing hole 23.

[0106] The second end portion 29, the longitudinal section of which is only partly illustrated in [Fig. 1], advantageously has a substantially conical shape, flared from upstream to downstream.

[0107] The downstream end of the second end portion 29 of the inlet cone 14 preferably has a cross-section greater than the cross-section of the first end portion 27 of the cone 14. An annular wall 46 extending substantially radially connects the upstream end of the first end portion 27 of the inlet cone 14 to the downstream part of its second end portion 29. As can be seen from [Fig.l], the annular wall 46 of the inlet cone 14 makes it possible to close an upstream end of each cell 26.

[0108] The rotor assembly 10 further comprises at least one blade 50. Preferably, the rotor assembly 10 comprises the same number of blades 50 as cells 26 included in the fan disk 12. As will be detailed, each blade 50 is partially installed in a respective cell 26.

[0109] [Fig.4] shows an example of a blade 50. Each blade 50 may be made of a metallic or composite material, for example a 3D woven composite.

[0110] The blade 50 comprises a blade root 52, a stilt 54 and a blade 56. The blade 50 further comprises a first face 58, called the intrados, and a second face 60, called the extrados. The intrados 58 and the extrados 60 are substantially parallel to a plane comprising the axial and radial directions when the blade 50 is installed in the corresponding cell 26.

[0111] The blade root 52 of each blade 50 is shaped to be installed in the corresponding cell 26. For this purpose, each blade root 52 may have a shape adapted to be installed in the respective cell 26. According to a non-limiting example, each blade root 52 may have a shape complementary to the shape of the cell 26 in which the blade 50 is installed.

[0112] In [Fig.4], the blade root 52 comprises a body 62 extending along an axis B. When the blade root 52 is installed in the respective cell 26, the axis B is substantially parallel to the longitudinal axis A of the rotor assembly 10. The body 62 has a section along a plane perpendicular to the axis B which is substantially frustoconical.

[0113] The blade root 52 further comprises an axial stop hook 64. The hook 64 is for example arranged on an upstream end portion of the body 62 of the blade root 52. More precisely, when the blade root 52 is installed in the respective cell 26, the hook 64 projects radially from the body 62. In other words, the hook 64 is included in a plane substantially perpendicular to the axis B.

[0114] The hook 64 includes a projecting portion 66. In this case, the projecting portion 66 includes a first protrusion 68 and a second protrusion 69. The first and second protrusions 68, 69 project from opposite sides of the hook 64. When the blade 50 is installed in the respective cell 26, the first and second protrusions 68, 69 project in a direction substantially perpendicular to the plane comprising the substantially axial and radial directions.

[0115] The first protrusion 68 is shaped to be engaged in the housing 36 of the first side wall 30 of the respective cell 26. The second protrusion 69 is shaped to be engaged in the housing 36 of the second side wall 32 of the respective cell 26. In particular, the first protrusion 68 and the second protrusion 69 have a shape allowing them to be inserted into the first part 36-1 and the second part 36-2 of the respective housing 36. Advantageously, when the first protrusion 68 or the second protrusion 69 are engaged in the first part 36-1, a clearance exists between the first protrusion 68 and the corresponding first part 36-1, and between the second protrusion 69 and the corresponding first part 36-1. Thus, the hook 64 can be moved axially in the housing 36, in particular in its first part 36-1.Preferably, in the second portion 36-2 of the respective housing 36, the first protrusion 68 and the second protrusion 69 are mounted axially adjusted. In other words, the axial dimension of the first and second protrusions 68, 69 is substantially equal to the axial dimension of the second portion 36-2 of the respective housing 36. The axial movement of the hook 64 in the housing 36 is then blocked, as will be detailed.

[0116] The stilt 54 is arranged between the blade root 52 and the blade 56, in particular in the radial direction when the blade 50 is installed in the corresponding cell 26. The stilt 54 provides the mechanical connection between the blade 56 and the blade root 52. The stilt 54 may, for example, have a rectilinear or curvilinear shape.

[0117] The blade 56 extends from the stilt 54, substantially radially when the vane 50 is installed in the corresponding cell 26. The blade 56 may have a curvilinear shape.

[0118] According to a non-limiting example, when mounting the blade 50 in the respective cell 26, the blade 50 is oriented from its root 52 to its blade 56 in the direction of the force of gravity. That is to say, when installing the blade 50 in the cell 26, the blade root 52 is in a higher position relative to the ground than the blade 56.

[0119] The blade root 52 is gradually introduced into the cell 52 from a axial movement of the blade 50. The blade root 52 can be dimensioned so that during the axial movement of the blade 50 in the cell 26, a radially internal end 52-1 of the blade root 52 is radially in contact with the bottom wall 34 of the cell 26.

[0120] As indicated previously, the first portion 36-1 of each housing is open at the upstream end 37 of the fan disc 12. The blade root 52 is therefore also dimensioned so as to ensure that during axial movement of the blade 50 in the cell 26, the projecting portion 66 is engaged in each housing 36 of the cell 26. In particular, during axial movement of the blade 50 in the cell 26, the protrusion 68 and the protrusion 69 each engage the first portion 36-1 of the respective housing 36 of the cell 26 in which each of them is received. As indicated previously, a clearance exists between each protrusion 68, 69 and the first portion 36-1 of the respective housing 36. This clearance allows the axial sliding of each protrusion 68, 69 in the first part 36-1 of the respective housing 36.

[0121] Once each protrusion 68, 69 of the projecting portion 66 of the hook 64 is radially opposite the second portion 36-2 of the respective housing 36, the force of gravity causes the radial displacement of the blade root 52 in the corresponding cell 26. Each protrusion 68, 69 is then engaged in the second portion 36-2 of the corresponding housing 36.

[0122] As indicated, each protrusion 68, 69 is mounted axially adjusted in the second part 36-2 of the corresponding housing 36. Axial displacements of the blade root 52 are thus avoided. The blade root 52 is thus retained, even in the event of critical events such as those indicated previously, in the rotor assembly 10 from a retention system directly integrated in the blade 50, without the need to use additional parts, such as locks, which reduces the number of parts to be machined and assembled.

[0123] Of course, according to an alternative embodiment, the projecting part 66 of the hook could comprise only one of the protrusions 68, 69. The installation of the blade 50 in the respective cell 26 could then be done in the manner explained above but with only one protrusion 68, 69 which is engaged in a housing 36.

[0124] The radial displacement of the blade root 52 leading to the introduction of the projecting part 66 into the second part 36-2 of each housing 36 causes the radially internal end 52-1 of the blade root 52 to move away from the bottom wall 34 of the cell 26. A radial clearance 67 is therefore formed between the radially internal end 52-1 of the root 52 and the bottom wall 34 of the cell 26. Advantageously, a radial dimension RI of the projecting part 66 of the hook 54 is less than a radial dimension R2 of the radial clearance 67. Also, when the radial clearance 67 is formed, the projecting part 66 of the hook 64 is fully engaged in the second part 36-2 of the corresponding housing 36. The retention of the blade 50 in the rotor assembly 10 is thus improved.

[0125] As visible in [Fig.l], a shim 70 is arranged radially between the radially internal end 52-1 of the foot 52 and the bottom wall 34 of the cell 26.

[0126] The shim 70 may be made, at least partially, of an elastically deformable material. For example, the shim 70 may comprise metal portions and semi-rigid elastomer portions. According to one example, the shim 70 may be made of the same material as the blade 50.

[0127] The longitudinal dimension of the wedge 70 is for example substantially equal to the longitudinal dimension of the cell 26 in which it is installed.

[0128] The radial dimension of the shim 70 is chosen so as to be able to fill the radial clearance 67. Advantageously, the shim 70 completely fills the radial clearance 67. The shim 70 therefore makes it possible to avoid uncontrolled movements of the blade 50 in the radial direction. Furthermore, in the event of a critical event suffered by the blade 50, the impact between the blade 50 and the cell 26 is limited, an energy of this impact being absorbed by the shim 70. The risks of damage to the blade 50 are thus reduced.

[0129] Preferably, the radial dimension RI of the projecting portion 66 of the hook 64 is less than the radial dimension of the shim 70. Also, when the shim 70 fills the radial clearance 67, it is guaranteed that the projecting portion 66 of the hook 64 is fully engaged in the second portion 36-2 of the corresponding housing 36. The retention of the blade 50 in the rotor assembly 10 is thus improved. The radial dimension of the shim 70 is for example equal to the radial dimension R2 of the radial clearance 67.

[0130] The rotor assembly 10 further comprises at least one blade platform 72. The rotor assembly 10 comprises, for example, the same number of platforms 72 as blades 50. The platforms are arranged adjacent to each other around the longitudinal axis A. In some cases, each platform 72 is an added part. In other cases, each platform 72 is formed in one piece with a respective blade 50. Each platform 72 may be made of the same material as the blades 50, or of a different material.

[0131] Now one of the platforms 72 will be described. Preferably, all of the platforms 72 of the rotor assembly 10 are similar or identical to that described below.

[0132] The platform 72 comprises an upper face 72-1 and a lower face 72-2. The platform 72 further comprises a first end portion 74 and a second end portion 76. The first end portion 74 comprises an upstream edge 75 of the platform 72, and the second end portion 76 comprises a downstream edge 77 of the platform 72. The upstream 75 and downstream 77 edges are connected to each other by a first lateral edge 79 and a second lateral edge 80. The first lateral edge 79 and the second lateral edge lateral 80 of the platform 72 are preferably substantially parallel to each other.

[0133] The first end portion 74 of the platform 72 extends substantially axially. Also, the first end portion 74 can come into radial support with at least one of the teeth 28 of the fan disc 12.

[0134] As illustrated in [Fig.6], each platform 72 may comprise a radial fixing notch 82 in its first end portion 74. Preferably, each platform 72 comprises two notches 82. In particular, a first notch 82 is arranged on the first lateral edge 79 and a second notch 82 is arranged on the second lateral edge 80 of the platform 72. Each notch 82 passes entirely through the platform 72 between its upper face 72-1 and its lower face 72-2.

[0135] Advantageously, as visible in [Fig. 6], when two platforms are arranged adjacently on the fan disc 12, the first notch 82 of one of the platforms 72 and the second notch 82 of the other platform 72 are radially opposite the cavity formed by the fixing hole 45 and the complementary fixing hole 23. The notches 82 of the two neighboring platforms 72 thus form an orifice shaped to receive the connecting member 48. Also, two adjacent platforms 72 can be connected to the fan disc 12 from the connecting member 48 used to connect the fan disc 12 and the inlet cone 14.

[0136] Alternatively, as seen in [Fig.7], the first end portion 74 of each platform 72 may have a radial fixing hole 84 passing entirely through the platform 72 between its upper face 72-1 and its lower face 72-2. The hole 84 is for example substantially circular. The hole 84 is in particular placed in the platform 72 so as to be radially opposite the cavity formed by the fixing hole 45 and the complementary fixing hole 23 when the platform 72 comes to bear against the fan disc 12. Also, the platform 72 may be connected to the fan disc 12 from the connecting member 48 used to connect the fan disc 12 and the inlet cone 14.

[0137] The connecting member 48 of the fan disk 12 to the inlet cone 14 is also used as a means of fixing the platform 72 to the fan disk 12, the number of parts in the assembly 10 is reduced. In addition, this fixing of the platform 72 can contribute to retaining each blade 50, in particular each blade root 52, in the fan disk 12 in the event of a critical event. In particular, the connecting member 48 is configured to work in shear in the event of a critical event. The forces due to this shear can be taken up by the two adjacent connecting members 48, as well as by the rest of the connecting members 48. The forces exerted on the blade 50 in the event of a critical event are thus distributed in the inlet cone 14, which limits the risk of loss or breakage of the blades 50.

[0138] The second end portion 76 is inclined relative to the axial direction so as to gradually move away in the radial direction from the fan disk 12. As visible in [Fig.l], the second end portion 76 of the platform 72 can be shaped to cooperate directly with a rectifier 88 (or “Inlet Guide Vane”, IGV, according to English terminology) and a drum 90 of the compressor 40.

[0139] To connect the platform 72 to the drum 90, the drum 90 comprises a portion 92 projecting substantially radially from the drum 90. The portion 92 is axially traversed by a bore 96. The second end portion 76 of the platform comprises at least one pin 98 shaped to be introduced and retained axially and radially in the bore of the portion 92 of the drum 90. In particular, the part of the pin 98 which is received in the bore 96 preferably has dimensions allowing adjusted or tight mounting of the pin in the bore 96.

[0140] As is apparent from Figures 1 and 10, the pin 98 may have an L-shape, without this being limiting. In certain cases, the part of the pin 98 which is received in the bore 96 comprises an annular notch 100. The wall of the portion 92 of the compressor drum can thus engage radially in the notch 100. This makes it possible to improve the holding in position of the pin 96 relative to the compressor drum 90, which also locks the platform 72 in position relative to the compressor drum 90. The locking in position of the platform 72 relative to the compressor drum 90 also contributes to axially retaining each blade 50 in position, even in the event of a critical event.

[0141] In the example of [Fig.8], the second end portion of the platform 76 also comprises a shoulder 94 in the upper surface 72-1 of the platform 72. The shoulder 94 cooperates axially with an upstream end of the rectifier 88. This, together with the fixing of the first end portion 74 on the disc 12 from the connecting member 48, makes it possible to maintain the platform 72 axially in position. Downstream of the shoulder 94, the platform 72 is radially opposite a radially internal surface of the rectifier 88. This makes it possible to contribute to the retention of the platform 72 radially in position.

[0142] The configuration of [Fig.8] makes it possible not to use a rotating spacer in the assembly 10. This simplifies the assembly and machining of the assembly 10. Furthermore, the weight of the assembly 10 can thus be reduced.

[0143] Of course, it is also possible to provide a rotating spacer 86 in the assembly 10, as illustrated in the variant of [Fig.8].

[0144] In this case, the second end portion 76 is shaped to cooperate with the rotating spacer 86 of the assembly 10. As visible in [Fig.l], the rotating spacer 86 is connected on the one hand to the rectifier 88, and on the other hand to the drum 90 of com- presser.

[0145] To connect the rotating spacer 86 to the drum, an axial bore of the rotating spacer 86 may be arranged radially opposite the bore 96 of the drum 90. A connecting member, for example a screw, may then be introduced into the bores of the rotating spacer 86 and of the drum 90 to fix the rotating spacer 86 to the drum 90.

[0146] In this configuration, the platform 72 also comprises the shoulder 94 described above. However, in this case, downstream of the shoulder 94, the platform 72 is in contact with a radially internal surface of the rotating spacer 86. This makes it possible to hold the platform 72 radially in position. The shoulder 94 comes into contact with the upstream end of the rotating spacer 86. This, combined with the fixing of the first end portion 74 on the disc 12 from the connecting member 48, makes it possible to hold the platform 72 axially in position.

[0147] Thus, the retention of the platform 72 in the assembly 10 is guaranteed, which also improves the retention of the blade 50 in the assembly 10.

[0148] Figures 6 and 7 show two different arrangements of the blades 50 and the platforms 72.

[0149] In a first arrangement, illustrated in [Fig. 6], each platform 72 is arranged around the intrados 56 and the extrados 58 of one of the blades 50. For this purpose, each platform 72 comprises a groove 102, visible in FIGS. 9 and 10. The groove 102 is capable of introducing each blade 50 into the respective platform 72. Alternatively, in this configuration the platform 72 can be made in one piece with the corresponding blade 50. Such a configuration is called here a “sock configuration”.

[0150] As can be seen from [Fig.6], in the sock configuration, the gap between two neighboring blades 50 is occupied by half of two neighboring platforms.

[0151] In the arrangement illustrated by [Fig.7], each platform 72 can be mounted in the interval between two neighboring blades 50. In this case, a first platform is adjacent to the intrados 56 of the blade 50, and a second platform distinct from the first is adjacent to the extrados 58 of the blade 50.

[0152] The present disclosure is not limited to the embodiments described above, only as an example, but it encompasses all the variants that a person skilled in the art may envisage within the framework of the protection sought.

Claims

Claims

1. A fan rotor assembly (10) for a turbomachine, the rotor assembly (10) comprising a fan disc (12) extending around a longitudinal axis (A) of the rotor assembly (10) and at least one blade (50) mounted on said fan disc (12), wherein a radially outer surface (18) of the fan disc (12) comprises a plurality of cells (26) distributed around said longitudinal axis (A), the at least one blade (50) comprising a blade root (52) engaged in one of said cells (26), wherein the blade root (52) comprises an axial stop hook (64) comprising a projecting portion (66) mounted axially fitted in a housing (36) of the fan disc (12),wherein said housing (36) comprises a first portion (36-1) extending substantially parallel to said longitudinal axis (A) and a second portion (36-2) extending substantially transversely to said first portion (36-1) so that the housing (36) has an L-shape.,

2. Rotor assembly (10) according to claim 1, wherein a radial clearance (67) is formed between a radially inner end (52-1) of said blade root (52) and a bottom wall (34) of the respective cell (26), wherein a shim (70) is installed in each cell (26) so as to fill said radial clearance (67).

3. Rotor assembly (10) according to the preceding claim, wherein a radial dimension (RI) of said projecting portion (66) of said hook (64) is less than a radial dimension (R2) of said radial clearance (67).

4. A rotor assembly (10) according to claim 3, wherein the radial dimension (RI) of said projecting portion (66) of said hook (64) is less than a radial dimension of said shim (70).

5. Rotor assembly (10) according to one of the preceding claims, further comprising at least one blade platform (72) having a first end portion (74) and a second end portion (76) axially opposed, the first end portion (74) comprising at least one radial retention hole (84) or at least one radial retention notch (82), the second end portion comprising at least one pin (98) projecting substantially axially and shaped to be received in a fitted or tight manner in a bore (96) included in a drum (90) of a compressor (40).

6. Rotor assembly (10) according to the preceding claim, wherein said at least one pin (98) comprises an annular notch (100) cooperating with a wall of the drum (90) of the compressor (40) delimiting said bore (96).

7. Rotor assembly (10) according to the preceding claim, in which the at least one platform (72) is formed in one piece with one of the blades (50).

8. A rotor assembly (10) according to one of the preceding claims, the assembly further comprising an inlet cone (14) disposed around the longitudinal axis (A) of the rotor assembly (10), wherein at least a first end portion (27) of the inlet cone (14) is mounted tightly in a complementary first end portion (25) of the fan disc (12).

9. Turbomachine such as a turbojet or a turboprop, comprising a rotor assembly (10) according to any one of claims 1 to 8.

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