FR2964426A1 - Movable fin for turbo machine e.g. turbojet engine, of aircraft, has blade formed of wires or filaments connected together by binder, and vibration damping device arranged at interior of winglet and including viscoelastic material element - Google Patents

Abstract

The fin has a blade (116) formed of wires or filaments connected together by a binder. The blade defines a leading edge (116c) and a trailing edge (116d) between an extrados wall and an intrados wall. The blade includes a top (116b) provided at a blade end opposed to a bottom part. The blade top is provided with a winglet (116a) or vane, where the winglet includes a vibration damping device (20). The vibration damping device is arranged at an interior of the winglet, and includes a viscoelastic material element.

Description

The invention relates to blades made of composite material, comprising a foot and a blade formed of threads or filaments, bonded together by a binder, said blade defining a leading edge and a trailing edge between which extend a extrados wall and an intrados wall, and at its end opposite said foot, a vertex. In such composite materials: - the son or filaments (such filaments may be made of fibers or the like), are made of different possible materials, including fiberglass, carbon fiber, but also metal or ceramic fibers or a mixture of these materials, and - the binder is preferably resin, and in particular thermosetting resin but it is also envisaged to use other types of binder or matrix such as ceramic matrices, and to form CMCs for ceramic matrix composite.

On turboprop engines with propellers or with counter-rotating propellers (also called "open-rotor" propellers), the end of the blades or blades of the propeller is the seat of non-stationary aerodynamic phenomena, in particular the presence of a vortex which has the disadvantage of dissipating energy (and therefore deteriorate the efficiency of the propeller), and cause noise pollution, especially if it is placed upstream of a second propeller forming a second stage as in the open-rotor motors. Indeed, in the presence of a second stage, the aerodynamic performance of this second stage is degraded at the location of the vortex released by the first stage because the incident flux is non-stationary and swirling. To guard against the influence of this vortex on the second stage of propellers, it reduces its height so that the vortex passes above the top of the second helix. However, because of this reduction in height, it is necessary to increase the aerodynamic load on the remaining portion of the blade, but then we are often limited by the aerodynamic design criteria related to this load (detachments, floating, tolerance to calibration gaps ...). For counter-rotating propeller-driven engines, another existing solution to the presence of the vortex (which degrades performance and acoustics on the downstream stage) is to increase the distance between the two.

propeller stages, which is also a problem because it increases the length of the engine (and its mass) and it also increases the cantilever of the propeller module vis-à-vis the suspension. Currently designs of propellers without "winglets" are not optimal in terms of aerodynamic performance because the presence of the vortex induces constraints on the aerodynamic profile. We understand that if we can reduce the size of this vortex, we can achieve a more optimal aerodynamic design. It has already been proposed to reduce the vortex which forms at the top of the blade by the addition, at the top of the blade, of devices called "winglets" (by analogy with the winglets positioned at the ends of the wings of planes to reduce the vortices that develop there). US 5,190,441 proposes such an arrangement. The mechanical design of these winglets is however difficult because of their position at the end of the rotational vane they are subjected to high centrifugal loads. Moreover, because of the presence of the vortex they must mitigate, the winglets are also subject to high vibratory loadings. These difficulties explain that these vortex reduction devices at the top of the blade have not yet found industrial application in series. It should be noted that for turboprop engines with a single propeller stage, the nuisance caused by the vortex is low because the structures that it impacts downstream are the wings of the aircraft, which are far enough apart that the vortex has time to dissipate before reaching the wing. The present invention aims to provide a blade to overcome the disadvantages of the prior art and in particular offering the possibility of minimizing the vortex rotating blade tip without significantly increasing the mechanical stresses, particularly vibratory, which are subject to dawn. For this purpose, according to the present invention, the blade is characterized in that said crown is equipped with a winglet or fin and that said winglet comprises a vibration damping device. Such a winglet forms a vortex reduction device at the top of the blade to allow prevention of the vortex formed naturally by the top of the blade of the blade. Such a vibration damping device forms a vibration damping system which will help minimize the vibrations appearing on the winglet, and generally on the blade of the blade. In this way, it is understood that by the simultaneous presence and action of the winglet and the damping device on the blade which are added at the top of the blade, the vortex is reduced while permitting to improve the resistance under vibratory loading. , in particular the winglet. This solution also has the additional advantage of allowing, in addition, by virtue of the properties of the vibration damping device, a phase shift of the deformation of the winglet with respect to the deformation of the blade, as well as a reduction of the risks of aeroelastic coupling between the vortex and the assembly consisting of the blade and the winglet. In addition, the present invention is applicable whatever the type of dynamic loading (crossing with motor harmonics, asynchronous excitation, acoustic, or aeroelastic instability), and the fact of adding damping in the structure of the dawn is beneficial for holding the blade-bearing part, even in areas other than the blade tip, since the damping produced by the damping device reduces overall the deformation amplitudes of the assembly consisting of the blade and the winglet. Overall, it is possible, thanks to the solution according to the present invention, for a given mechanical strength objective, for example an acceleration value at the top of the blade, to reduce the thickness of the crown of the blade, and thus, by reducing the mass of the blade, also reduce the mass of the engine. Thus, we understand that in general the top of the dawn consists of the winglet. Preferably, said vibration damping device is disposed inside said winglet.

According to the invention, the vibration damping device is incorporated in the winglet.

Advantageously, said vibration damping device comprises at least one element of viscoelastic material. Thus, according to the invention is added in the mechanical structure of the winglet at least one element of viscoelastic material.

This element of viscoelastic material is for example glued into the structure, or inserted during the manufacturing process, or vulcanized on the piece consisting of the blade and the winglet. In a preferred arrangement, said blade forms a turbomachine blade, preferably a turbojet fan blade, a turboprop propeller or a contra-rotating propeller motor. Thus, thanks to the invention, it makes applicable to a blade winglet technology that has been proven to reduce vortices of wing tips on aircraft.

Other advantages and characteristics of the invention will emerge on reading the following description given by way of example and with reference to the appended drawings, in which: FIG. 1 is a perspective view of a contra-rotating propeller motor; -rotatives of the prior art, - Figures 2A, 2B and 2C show a blade according to the prior art used in the motor according to Figure 1, respectively in perspective, from the front and according to the vertical projection of different sections distributed along. of the blade, - Figures 3A and 3B are partial views, respectively of side and front, of a blade according to the invention; FIG. 3C is an enlarged view of the apex of the blade according to zone IIIC of FIG. 3B; FIGS. 4A to 4F are partial diagrammatic views of the top of the blade according to a first embodiment, in which an element made of viscoelastic material is visible by transparency; FIGS. 5A to 5C are partial diagrammatic views of the apex of FIG. dawn according to a second embodiment, - Figures 6A and 6B show steps of manufacturing a blade according to a third embodiment, and - Figures 7A to 7F show steps of manufacturing a blade according to a third embodiment.

With reference to FIG. 1, a contra-rotating fast-propeller motor 10 of the prior art can be seen equipped with two stages of propellers 12, 14 with the upstream propeller 12 whose blades 16 are provided with their top 16b of a winglet 16a (see Figure 2A representing in perspective a blade 16 equipped with a winglet 16a). In this case, as it appears in FIG. 2B (front view of the blade) and in FIG. 2C (vertical projection view of different sections A to L indicated in FIG. 2B, distributed along the blade 16), the winglet 16a has geometrical characteristics differentiating it from the rest of the blade 16. Thus, as it appears in FIG. 2A, it can be seen in particular that the winglet 16a deviates from the main axis 15 or the longitudinal axis of the blade 16 (15 'being the vertical projection of said main axis 15). Furthermore, it also appears (see FIG. 2C) that the median line 17 of the winglet 16a forms, in vertical projection, a projected median line 17 'presenting a point of inflection M (see FIG. 2C) which marks the boundary between the winglet 16a and the rest of the blade. This median line 17 is defined as grouping all the points of the blade, each forming the center of the closed curve delimiting a cross section of the blade (the sections AA,..., LL of FIG. 2C constituting a part of the cross-sections of the blade). the blade 16), these cross sections being orthogonal to the main axis 15. In the case of Figures 2A to 2C, the limit between the winglet 16a and the remainder of the blade is between 50 and 70% of the height of the the blade (starting from the foot located at section LL in FIG. 2C), but in many cases, including for the implementation of the present invention, a winglet which starts beyond 70 is preferably used. % and advantageously between 80 and 90% of the height of the blade. In a more general manner, and in the context of the present invention, the term "winglet" means any fin or "fin" forming an appendix placed at the top of blade, attached or integrated to the blade, whose profile, shape and shape. orientation are in discontinuity from those of the rest of the blade. More specifically, the winglet has an axial (longitudinal) curvature which is different from that of the remainder of the blade and / or a curvature in the transverse direction which is different from that of the remainder of the blade. For example, the curvature of the winglet is accentuated relative to the rest of the blade, which gives a curved look to this winglet. For example, the winglet has a substantially helical shape. A winglet may also consist of an appendage protruding from the top of the dawn. Thus, the winglet may consist of an appendix directed perpendicularly to the main axis of the blade. Different alternative configurations may correspond to this situation: - such a protrusion may be rectilinear, - such protrusion may be curved while remaining in a plane orthogonal to the main axis of the blade, - such protrusion may have two parts, among which one first portion connected to the remainder of the blade and a second portion forming the free end of the winglet with either only the first portion, or only the second portion which is directed perpendicular to the main axis of the blade. According to the present invention, a damping device is located at the location of the winglet, preferably partially inside the winglet. Referring to Figures 3A-3C to illustrate the principle of the present invention by an example of blade according to the invention. FIGS. 3A and 3B are partial views of the blade 116 and more specifically of a portion carrying the top 116b, respectively from the side (axial trace) and from the front: at the end of the blade, the winglet 116a is found. In this winglet 116a is embedded a damping device in the form of an element of viscoelastic material 20. In FIG. 3C, this element of viscoelastic material 20 opens on one of the lateral faces of the winglet 116a forming the trailing edge 116d (see Figure 3A) and a portion of the end face of the blade tip 116b, being covered elsewhere by the winglet material 116a. Alternatively (case not shown), the element of viscoelastic material 20 is completely embedded in the winglet 116a and does not open on any of its faces (or the top 116b, or the leading edge 116c, nor the trailing edge 116d, neither the intrados wall 116e, nor the extrados wall 116f). It is recalled that the invention relates to the blades made of composite material and that the blade is made of a composite material, as is preferably the winglet 116b which, in this way, is actually an integral part of the blade 116. Thus, in the following and unless otherwise indicated, the entire blade 116, including the winglet 116b, is formed of son or filaments, bonded together by a binder.

The present invention is applicable in numerous configurations, and to allow to integrate said damping device in different composite structures used in the case of propeller blades. The main difficulty with a viscoelastic material used in said damping device, is that it provides damping optimally when it is stressed in shear between two layers of rigid material deforming differently. According to the present invention, it is preferred to integrate the damping device within the composite structure of the blade.

According to a first embodiment of the blade according to the invention, visible in Figures 4A to 4F, at least at the location of the winglet 116a, said son or filaments of the blade form a woven structure and said damping device vibration (including the viscoelastic material member 20) is disposed within the woven structure. This woven structure consists in particular of woven strips assembled together or a single three-dimensional woven structure. The injection of the thermosetting resin forming the binder is advantageously carried out according to the RTM technique "Resin Transfer Molding". Preferably, the woven structure is thus obtained by three-dimensional weaving of the son or filaments. In the context of this first embodiment, during weaving, there is defined a free space, formed between woven zones, also called release zone or untied zone, which receives the element of viscoelastic material 20 before injection of resin and subsequent manufacturing steps. The untied zone, which corresponds to the location of the viscoelastic material element 20, can lead to the leading edge 116c, to the trailing edge 116d or to the top 116b of the winglet 116a of the blade 116, to one or at many of these places simultaneously. The choice of the location or locations where the untied area opens is to be determined according to the manufacturability constraints (insertion of the viscoelastic element 20) and the stiffness required at this part of the part (the stiffness is increased when the woven three-dimensional composite is untied, it is said to be interlocked). In FIGS. 4A and 4E, the untied zone of the woven preform and the viscoelastic member 20 open at both the apex 116b and the trailing edge 116d of the winglet 116a of the blade 116.

In FIG. 4B, the untied zone of the woven preform and the viscoelastic element 20 open only at the apex 116b of the winglet 116a of the blade 116. In FIG. 4C, the untied zone of the woven preform and the viscoelastic element 20 open out. only at the trailing edge 116d of the winglet 116a of the blade 116. In FIG. 4D, the untied zone of the woven preform and the viscoelastic element 20 of the winglet 116a of the blade 116 open only to the leading edge 116c of the winglet 116a. of the blade 116. In FIG. 4F, the untied zone of the woven preform and the viscoelastic element 20 open at the same time to the apex 116b and to the leading edge 116c of the winglet 116a of the blade 116. The filaments or fibers of the woven preform are carbon or other material such as glass, silica, silicon carbide, alumina, aramid or an aromatic polyamide.

It is recalled that the viscoelasticity is a property of a solid or a liquid which, when deformed, shows a viscous and elastic behavior by a simultaneous dissipation and storage of mechanical energy. The material of the viscoelastic element 20 is of rubber, silicone, elastomeric polymer, epoxy resin ...

According to a second embodiment of the blade according to the invention, visible in FIGS. 5A to 5C, the blade 116 comprises, at least at the location of the winglet 116a, a laminate composite formed of superposed composite layers 118 and said vibration damping device (the element of viscoelastic material 20) is disposed between two of said superimposed layers 118. Thus, in the case of a laminated composite blade 116, the viscoelastic element 20 can be integrated very easily during the stack of layers 118 of unidirectional composites which extend from the extrados wall 116f to the intrados wall 116e. In FIG. 5A, the viscoelastic material element 20 is visible by transparency and FIGS. 5B and 5C correspond to sectional views of the winglet 116a. FIG. 5B shows the case of a viscoelastic element 20 of constant thickness and in FIG. 5C the case of a viscoelastic element 20 of variable thickness is shown. According to a third embodiment of the blade according to the invention, at least at the location of the winglet 116a, said son or filaments of the blade 116 are braided so as to form several superimposed braided layers and said damping device vibration (the viscoelastic material member 20) is disposed between two of said braided layers. According to this other and third embodiment of the invention which applies to a braided composite blade, the viscoelastic member 25 can be integrated very easily during braiding, between two braiding passes. FIGS. 6A and 6B illustrate this principle: during a first or an nth braiding pass, the wires 32 are braided around a mandrel 30 in order to cover it gradually in the main direction of the mandrel 30 (first direction represented by the arrow 34), then during the n + lth braiding pass, the son 32 are braided in the other direction (second direction, opposite direction to the first direction and represented by the arrow 36) while an element The viscoelastic 20 was previously placed on the weave made during the previous pass, so that during the n + 1th braiding pass, the son 32 eventually cover and enclose the viscoelastic element 20 between two braids.

This braiding technique therefore makes it very easy to integrate the vibration damping device into the winglet 116a. According to a fourth embodiment of the blade according to the invention, the blade 116 is formed of several substructures and said vibration damping device is disposed between two of said substructures. In this way, in the case of a blade structure 16 (including the winglet 116a) incorporating several substructures initially made independently of each other and in particular according to different techniques including those described above, the viscoelastic element 20 can be integrated in an interface during the assembly of different substructures Thus, FIGS. 7A to 7F illustrate an example according to this fourth embodiment of the blade according to the invention, in which a viscoelastic element 20 is inserted between the spar and the composite shell: FIG. 7A: during the first manufacturing step, a steel "tulip" type foot 40 is provided, FIG. 7B: then, the core 42 of the blade is formed by a foam, especially polyurethane, - Figure 7C: over the core 42 of the blade which then constitutes a mandrel, is woven a carbon fiber frame structure 44, and a viscoelastic element e 20 is mounted at the top of the blade, at the location of the winglet, - FIG. 7D: the assembly formed of the spar 44 and the viscoelastic member 20 is covered by a composite shell 46, - FIG. 7E: the shell composite 46 is covered with a second shell 48 based on braided "kevlar" (trademark) fibers, itself partly surmounted by a nickel foil 50 covering the leading edge, and - FIG. 7F: one overcomes the base of the leading edge of a deicing plate 52, then the injection of the resin (arrow 54) is carried out before the heat-hardening.

In this way, a blade 119 is obtained in accordance with the present invention.

Alternatively, the viscoelastic element 20 or a second viscoelastic element 20 may be integrated with another interface and in particular between the composite shell 46 and the second shell 48 based on braided kevlar fibers.

According to a fifth embodiment (not shown) of the blade according to the invention, said element of viscoelastic material 20 is a layer of a viscoelastic material and said vibration damping device further comprises a rigid counter-layer forming a blade integral with the winglet 116a of the blade 116.

In this case, instead of integrating the vibration damping device inside the structure, a counter-layer is used to connect said vibration damping device to the winglet 116a on the surface of the latter. Thus, by way of non-illustrated example of this fifth embodiment, the present invention makes it possible conventionally to use, on the leading edge 116a, a metal protection means such as a titanium foil glued to the material composite extending along the leading edge. In this case, typically this foil (not shown) is a blade forming a wing on each side: a first wing covering the intrados wall downstream of the leading edge and a second wing covering the extrados wall downstream of the leading edge. The two wings are joined along the leading edge by a thicker part. Such a blade is manufactured for example according to the technique described in patent EP 1,777,063 in the name of the present applicant. According to this technique, a preform is made by three-dimensional weaving of filaments. The one-piece woven preform is then cut out by cutting the outline from a three-dimensional abacus. The piece is placed in a conformation mold. Then after appropriate deformation the piece is placed in a compaction mold which stiffens the deformed preform. Overcompaction of the leading edge is performed so as to allow the placement of the protection element along the leading edge. It is a longitudinal half-sleeve element with two wings intended to cover a portion of the extrados and intrados walls downstream of the leading edge. As explained in the patent cited above, the protective element is arranged in a mounting device capable of spreading the wings. The protective element is placed by its leading edge previously coated with glue between the two wings and then released.

The assembly is placed in an injection mold in which a binder comprising a thermosetting resin is injected so as to impregnate the entire preform. Finally, the mold is heated. In such a configuration, one can also implement the present invention, with a blade tip formed of a winglet, also partially covered with the foil forming the metal protection element, is incorporated between the blade and the element a viscoelastic material member 20 formed of at least one layer of a viscoelastic material. In this case, the metal protection element forms a rigid counter-layer for the vibration damping device that it constitutes with the element of viscoelastic material 20. According to other variants not described in detail, it is understood that the The proposed damping technology can be provided with vibration damping devices formed by a multi-layer formed of layers of thickness and variable viscoelastic characteristics to maximize the damping function. It should be noted that the invention is also applicable to a winglet 116a formed from an independent part and then mechanically connected to the blade 116 (for example by riveting, bolting, by means of inserts, etc.). another variant, the winglet 116a is not made of composite material but of metal material, mechanically connected to the rest of the blade structure (for example by riveting, bolting, or gluing).

Claims (11)

REVENDICATIONS1. A movable blade (119) made of composite material, comprising a foot (40) and a blade (116) formed of threads or filaments (32) bound together by a binder, said blade (116) defining a leading edge ( 116c) and a trailing edge (116d) between which an extrados wall (116f) and an intrados wall (116e) extend, and at its end opposite said foot, an apex (116b), characterized in that said top (116b) is equipped with a winglet (116a) or wing and that said winglet (116a) has a vibration damping device (20). 2. blade (119) according to claim 1, characterized in that said vibration damping device (20) is disposed within said winglet (116a). 3. blade (119) according to any one of the preceding claims, characterized in that at least at the location of the winglet (116a), the blade (116) comprises a laminate composite formed of superimposed composite layers (118) and in that said vibration damping device (20) is disposed between two of said superposed layers (118). 4. blade (119) according to any one of claims 1 and 2, characterized in that at least at the location of the winglet (116a), said son or filaments of the blade (116) form a woven structure and said vibration damping device (20) is disposed within the woven structure. 5. Dawn (119) according to the preceding claim, characterized in that the woven structure is obtained by three-dimensional weaving son or filaments (32). 6. blade (119) according to any one of claims 1 and 2, characterized in that at least at the location of the winglet (116a), said son or filaments (32) of the blade (116) are braided from for forming a plurality of superimposed braided layers and that said vibration damping device (20) is disposed between two of said braided layers. 7. blade (119) according to any one of claims 1 to 3 and 6, characterized in that the blade (116) is formed of several substructures and in that said vibration damping device (20) is disposed between two of said substructures. 8. blade (119) according to any one of the preceding claims, characterized in that said vibration damping device (20) comprises at least one element of viscoelastic material. 9. blade (119) according to the preceding claim, characterized in that said element of viscoelastic material is a layer of a viscoelastic material and in that said vibration damping device (20) further comprises a counter-layer 10 rigid forming a blade integral with the winglet (116a) of the blade (116). 10. blade (119) according to any one of the preceding claims, characterized in that it forms a turbine engine blade. 11. Aube (119) according to the preceding claim, characterized in that it forms a turbine engine fan blade, turboprop propeller 15 or a contra-rotating propeller motor.