EP3797224A1 - Improved turbmachine fan disc - Google Patents

Abstract

The invention relates to a disc (40) that is able to support platforms (30) and blades (20) of a fan (2) and has an external surface (40a) having a series of grooves (42) for receiving the fan blades and teeth (44) interposed between the grooves (42) for supporting the fan platforms (30), an upstream face (40b) of the disc, and a plurality of axial protrusions (46) that are disposed radially about the axis (A) of the disc on the upstream face (40b) of the disc (40) and are able to be fastened to a fan platform retaining flange, the protrusions (46) being offset radially towards the inside of the disc (40) compared with the grooves (42) of the disc (40) and being disposed circumferentially between two teeth (44) of the disc (40).

Description

 Improved turbomachine blower disc

FIELD OF THE INVENTION

 The present invention relates to the general field of aviation turbomachines, and more specifically the field of blower discs of an aerospace turbomachine, an assembly comprising the blower platforms and the disc, and a blower comprising this assembly.

 STATE OF THE PRIOR ART

 In a turbomachine, the blade platforms of the fan must perform several functions. From an aerodynamic point of view, these platforms have the primary function of defining the flow vein of the air. In addition, they must also be able to withstand significant effort by deforming as little as possible and remaining attached to the disc that carries them.

 In order to meet these different requirements, some configurations have been proposed in which the platforms have a first part to define the flow of air flow and ensure the retention of the platform when the engine is rotating and a second part to limit the deformations of the first part under the effects of centrifugal forces and to maintain the platform in position when the engine is stopped.

 In existing solutions, the platform may take the form of a box with a two-dimensional vein wall retained downstream by a drum and upstream by a ferrule, the upstream retention by the ferrule being carried out at above the tooth of the fan disk (a flange of the ferrule coming axially and radially block the platform upstream).

Such upstream retention performed above the disc tooth with a ferrule has the disadvantage of imposing a high hub ratio, the hub ratio being the ratio of the radius between the axis of rotation and the point of the leading edge of the dawn flush on the surface of the platform, on the radius between the axis of rotation and the point of the outermost leading edge. Moreover, this upstream retention is likely to generate over-constraints on the tooth and in the alveolus of the disk, at the level of the connection between the ferrule and the disk.

 To optimize the performance of the blower, and more generally of the turbomachine, it is desirable to have an assembly of a reported blower blade platform on a fan disk which has a hub ratio. the lowest possible, while limiting the stresses at the level of the tooth and the cavity of the disc.

 PRESENTATION OF THE INVENTION

 An embodiment relates to a disk adapted to support platforms and blades of a fan, and comprising:

 an outer surface having a succession of grooves for receiving the fan blades and teeth interposed between the grooves to support the fan platforms,

 an upstream face of the disk, and

 a plurality of axial projections disposed radially around the axis of the disk on the upstream face of the disk, and capable of being fixed to a fan platform retention flange, the projections being offset radially towards the inside of the disk relative to to the grooves of the disc, and being circumferentially disposed between two teeth of the disc.

 By "upstream face", it comprises upstream relative to the direction of flow of air, when the disk is disposed in a blower.

 By "axial projections" is understood axial in the direction of flow of air, or along the axis of rotation of the disc, when the disc is disposed in a blower.

 By "radially offset" is understood shifted inwardly of the disk, that is to say towards the axis of rotation of the disk.

The axial projections being offset radially inwardly of the disk relative to the grooves of the disk, and arranged circumferentially between two teeth of the disk, when the projections are fixed on a platform retention flange, the fastening zone lying on the projections is thus shifted radially and circumferentially with respect to the teeth of the disc. This has the advantage of limiting the stresses at the tooth of the disc, when an external element, for example a platform retention flange, is fixed on the disk.

 Furthermore, this fixing zone being radially offset relative to the teeth of the disk, this has the advantage of freeing space at the upstream axial end of the disk tooth, allowing for example to machining the tooth of the disc. Such a machining can make it possible to modify the shape of the upstream axial end of a platform supported by said tooth, with respect to the known platforms, and thus to modify the air flow vein when the platform is arranged in a blower . It is thus possible to reduce the hub ratio in order to improve the performance of the fan, and therefore of the turbomachine in which the fan is mounted.

 In some embodiments, the axial projections are tabs machined on the upstream face of the disc and folded towards the center of the disc.

 The tongues may have a main face perpendicular to the axis of the disc, and a thickness, along the axis of the disc, low compared to the dimensions of the main face. The shape of these radial projections has the advantage of being simple to achieve.

 In some embodiments, a face of the axial projections has an axis of aperture parallel to the axis of the disk.

 The orifice may be formed on the main face of the tongue. It makes it possible to fix an element external to the disk, for example a retention flange or a ferrule, by means of a screw or a bolt, for example.

 In some embodiments, in a view of the upstream face of the disk along the axis of the disk, the center of the orifice of each axial projection is disposed on a straight line passing through the center of the disk and the bottom of the disk. a groove of the disc, the bottom of a groove being the point of the groove, according to this view, located equidistant from the two teeth between which it is located.

In other words, the center of the orifice of each axial projection is aligned radially with the bottom of a groove. The end of the disc teeth is the seat of significant mechanical stress when the disc is disposed in a blower. This provision allows thus to optimize the circumferential distance, in a view of the upstream face of the disk along the axis of the disk, of the center of the orifice of each projection relative to the two teeth, where the mechanical stresses are important, between which it is located. Fixing a ferrule on the axial projections can therefore be performed in an area less mechanically constrained than if the projections were aligned with the teeth. The distribution of the stresses within the disk, when it is arranged in a fan, is thus optimized, and the existence of local over-constraints can thus be limited or avoided.

 In some embodiments, a radius of the disk being a segment between the center of the disk and the bottom of a groove, a distance between the center of the disk and the center of the axial projection orifice is less than 95% of the radius of the disc, preferably less than 90%, more preferably less than 80%.

 Bringing the center of the orifice of the axial projection of the center of the disc makes it possible to move away from more mechanically stressed areas the point of attachment between a ferrule and the disc, when the disc is disposed in a blower. .

 In some embodiments, the axial projections are disposed on the upstream face of the disk at regular intervals along the circumference of the disk. This allows a uniform distribution of mechanical stresses on the upstream face of the disk, when a ferrule is fixed on it.

 In some embodiments, the number of axial projections is equal to half the number of grooves of the disk.

 Preferably, the axial projections are distributed at regular intervals so as to be radially aligned with the bottom of one groove out of two. Therefore, two times less bonding is required between the disc and a ferrule, when a ferrule is attached to the disc, than if an axial projection was provided for each groove. This makes it possible to reduce the number of assembly steps and the number of connection pieces required. The time and cost of assembly can be limited.

The present disclosure also relates to an assembly comprising a disc according to any one of the preceding embodiments, at least one platform, and at least one retention flange. upstream to ensure the axial and radial retention of the upstream axial end of the platform, wherein the upstream retention flange is fixed on the axial projections of the upstream face of the disc.

 When the retention flange is fixed on the disc, the interface between the flange and the disc, corresponding to the fastening area of the flange on an axial projection of the disc, is offset radially towards the inside of the disc, relative to a groove of the disk, and is interspersed circumferentially between two teeth of the disk, unlike known systems in which this interface is located at the tooth of the disk. This offset makes it possible to limit the stresses at the upstream axial end of the teeth. In addition, the offset of this interface makes it possible to free up space at the upstream axial end of the tooth of the disc, offering more possibility of machining the tooth and thus of modifying the shape of the platform and thus, the reduction of the hub ratio.

 In some embodiments, the upstream retention flange is a ferrule.

 The present disclosure also relates to a turbomachine fan comprising an assembly according to any one of the embodiments described herein, and a plurality of vanes mounted in the grooves of the disc.

 BRIEF DESCRIPTION OF THE DRAWINGS

 The invention and its advantages will be better understood on reading the detailed description given below of various embodiments of the invention given by way of non-limiting examples. This description refers to the pages of annexed figures, in which:

 FIG. 1 is a schematic sectional view of a turbomachine according to the invention,

 FIG. 2 is a schematic view along direction II of the fan of FIG. 1,

 FIG. 3 is a perspective view of a disk according to the invention,

 Figure 4 is a longitudinal sectional view of an assembly comprising a retention flange, a platform and a disc according to the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS In this presentation, the term "longitudinal" and its derivatives are defined relative to the main direction of the platform in question; the terms "radial", "inside", "outside" and their derivatives are themselves defined with respect to the axis of the disk, corresponding to the main axis of the turbomachine; finally, the terms "upstream" and "downstream" are defined with respect to the flow direction of the fluid passing through the turbomachine. Also, unless otherwise indicated, the same reference characters in different figures denote the same characteristics.

 Figure 1 shows a schematic longitudinal sectional view of a turbofan engine 1 centered on the axis A according to the invention. It comprises, from upstream to downstream: a fan 2, a low-pressure compressor 3, a high-pressure compressor 4, a combustion chamber 5, a high-pressure turbine 6, and a low-pressure turbine 7.

 Figure 2 shows a schematic view of the fan 2 of Figure 1 along the direction II. The fan 2 comprises a fan disk 40 in which a plurality of grooves 42 are made at its outer periphery. These grooves 42 are rectilinear and extend axially from upstream to downstream all along the disc 40. They are also regularly distributed around the axis A of the disc 40. In this way, each groove 42 defines with its neighbor a tooth 44 which also extends axially from upstream to downstream along the disc 40. Equivalently, a groove 42 is delimited between two adjacent teeth 44.

 The blower 2 further comprises a plurality of vanes 20 of curvilinear profile (only four blades 20 have been shown in Figure 2). Each blade 20 has a foot 20a which is mounted in a respective groove 42 of the fan disk 40. For this purpose, the root 20a of a blade 20 may have a fir or dovetail shape adapted to the geometry of the blades. grooves 42.

Finally, the fan 2 comprises a plurality of reported platforms 30, each platform 30 being mounted in the gap between two adjacent fan blades 20, in the vicinity of the feet 20a thereof, in order to delimit, on the inner side , a vein annular air inlet into the blower 2, the vein being delimited on the outer side by a fan casing.

 Figures 1 and 2 also show an inner radius RI and an outer radius RE. The internal radius R1 corresponds to the radius between the axis of rotation A and the point of the leading edge of a blade 20 flush with the surface of a platform 30. The outer radius RE corresponds to the radius taken between the rotation axis A and the point of the leading edge of an outermost blade 20. These two radii RI, RE are those used in the calculation of the hub ratio RI / RE. Reducing the internal radius RI makes it possible to reduce this hub ratio. In other words, the reduction of the hub ratio, in particular by acting on the internal radius RI, amounts to bringing the aerodynamic stream of air intake closer to the fan disk.

 Figure 3 shows a perspective view of a fan disk having an outer surface 40a and an upstream face 40b. The outer surface 40a has a succession of grooves 42 in which can be housed a foot 20a blade 20 blower, and teeth 44 interposed between the grooves 42, capable of supporting the platforms 30 of blower. Each tooth 44 may have a main tooth surface 44a, and a bevelled surface 44b at its upstream axial end.

 Furthermore, the disk 40 comprises, on its upstream face 40b, a plurality of axial projections 46, having a tongue shape and being arranged circumferentially, at regular intervals, about the axis A. These protrusions can for example, by machining on the upstream face 40b of the disk, for example on the pin of the disk. The number of axial projections 46 may be equal to half the number of grooves 42, each projection 46 being aligned radially with the corresponding groove 42. In other words, each projection 46 is interspaced circumferentially between two teeth 44 of the disc 40. In addition, each axial projection 46 is offset radially towards the inside of the disc, that is to say towards the axis A, relative to the corresponding groove 42.

Each axial projection 46 may comprise a fixing orifice 46a on its upstream face 46b, for inserting a fixing means 49, for example a screw or a bolt. Fixing a flange upstream retention 50, for example a ferrule, can thus be performed at an axial projection 46, for example by inserting the fixing means 49 through a flange orifice 52 and the fixing orifice 46a of the projection, the fixing means 49 being then fixed, for example by a bolt, to the axial projection 46. The retention flange 50 being fixed to the disc 40, an upper surface 54 of the flange 50 then makes it possible to ensure the radial retention of a retention surface 32 located at the upstream axial end of the platform 30.

 The attachment zone between the disk 40 and the retention flange 50 being located at the axial projections 46, therefore closer to the center of the disk, this limits the stresses exerted during operation of the fan at the level of sensitive surfaces such as the upstream axial end of the teeth 44. Furthermore, this interface between the disc 40 and the retention flange 50 being offset radially with respect to the grooves of the disc, in comparison with the known structures, the cantilevers 44c, usually allowing the attachment of the ferrule to the upstream end of the teeth of the disc, can be removed. This frees up space at the upstream axial end of the teeth 44 of the disc. It is also possible to modify more freely the upstream axial end of the teeth 44, and therefore the upstream axial end of the platform 30, for example by providing an inclined wall 34 on the upstream end of the platform 30, the wall inclined 34 coming into contact with the bevelled surface 44b of the tooth 44. It is thus possible to reduce the hub ratio in order to optimize the performance of the blower, and therefore of the turbomachine in which the blower is mounted.

 Although the present invention has been described with reference to specific embodiments, it is obvious that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the revendications. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

Disc (40) adapted to support platforms (30) and vanes (20) of a blower (2), and comprising:  an outer surface (40a) having a succession of grooves (42) for receiving the fan blades (20) and teeth (44) interposed between the grooves (42) for supporting the fan platforms (30),  an upstream face (40b) of the disk, and  a plurality of axial projections (46) arranged radially about the axis (A) of the disk on the upstream face (40b) of the disk (40), and adapted to be attached to a fan platform retaining flange (50) , the projections (46) being radially inwardly displaced from the disc (40) relative to the grooves (42) of the disc (40), and being circumferentially disposed between two teeth (44) of the disc (40). 2. Disc (40) according to claim 1 wherein the axial projections (46) are tabs machined on the upstream face (40b) of the disc and folded towards the center of the disc. 3. Disc according to claim 1 or 2, wherein a face of the axial projections comprises an axis of aperture parallel to the axis (A) of the disc. 4. Disc according to claim 3, wherein, in a view of the upstream face of the disc along the axis (A) of the disc, the center of the orifice of each axial projection is disposed on a straight line passing through the center of the disk and the bottom of a groove of the disc, the bottom of a groove being the point of the groove, according to this view, located equidistant from the two teeth between which it is located. A disk according to claim 4, wherein, a disk radius being a segment between the center of the disk and the bottom of a groove, a distance between the center of the disk and the center of the orifice of the axial projection is less than 95% of the radius of the disk, preferably less than 90%, more preferably less than 80%. Disk according to any one of claims 1 to 5, wherein the axial projections (42) are arranged on the upstream face (40b) of the disk at regular intervals along the circumference of the disk (40). Disk according to any one of claims 1 to 6, wherein the number of axial projections is equal to half the number of grooves (42) of the disc (40). 8. An assembly comprising a disc (40) according to any one of claims 1 to 7, at least one platform (30), and at least one upstream retention flange (50) for axial and radial retention of the end axial upstream of the platform (30), wherein the upstream retention flange (50) is fixed on the axial projections (46) of the upstream face (40b) of the disc (40). The assembly of claim 8, wherein the upstream retention flange (50) is a ferrule attached to each axial projection (42) via a bolt. 10. A turbomachine blower (2) comprising an assembly according to claim 8 or 9, and a plurality of vanes (20) mounted in the grooves (42) of the disk (40).