FR2863319A1 - Wind generator`s blade for producing electricity, has ribs coupled to mast using sticking lip, and layer coupled to ribs by sticking lip, where sticking lip is constituted of bi-component polyurethane adhesive - Google Patents

Abstract

The blade includes ribs (2) coupled to a mast (1) using a sticking lip (4). A layer (3) is coupled to the ribs by the sticking lip. The sticking lip is constituted of a bi-component polyurethane adhesive. The sticking lip has a shearing resistance of 10 Mega Pascal and an elasticity modulus of 1200 Mega Pascal. The lip has a thickness of 0.75 millimeter. An independent claim is also included for an aerogenerator comprising blades.

Description

Aerogenerator blade with semi-rigid links and aerogenerator

corresponding.

  The invention relates to the field of wind turbines. More specifically, the invention relates to a wind turbine generator that can be grouped with other wind turbines of the same type to form a power plant.

  In the field of wind turbines, the principle of wind turbines is widely known and applied.

  These wind turbines can be used by individuals for their own use. Domestic wind turbines of this type are therefore generally insulated and relatively small in size.

  Another category of wind turbines is intended for larger-scale electricity production: these wind turbines are large in size and are generally grouped into power plants.

  World electricity generation by wind turbines is currently undergoing significant development, in particular because they represent a means of producing ecological energy.

  However, on a technical level, large wind turbines still pose many problems.

  It is recalled that a wind turbine, or more generally an aerogenerator, consists of a mast at the top of which is placed a generator driven by a hub carrying the blades (generally three in number). The operating principle then consists in transforming the kinetic energy of the wind acting on the blades into mechanical energy due to the rotational movement of the rotor, and then transforming this mechanical energy into electrical energy.

  As already mentioned, wind turbines intended for larger-scale electricity production are becoming larger and larger: the blades of these wind turbines each measure, for example, 23 m (for a power of 750 KW) or more, for powers of up to several megawatts. The current trend is to seek to increase the power of wind turbines. This has the effect of increasing the length of the blades.

  The blades represent a significant part of the budget of a wind turbine. Their lifespan has therefore become an essential concern for manufacturers (for example, the lifespan programmed 5 years ago on blades with a dimension close to 25 m has been divided by 2, or reduced to 10 years, while significant deterioration appear after 3 to 4 years or less).

  The main sources of fatigue observed on the blades are due to the following aerodynamic forces: vibrations; - permanent fluctuation of the wind speed; gusts.

  Another source of significant fatigue comes from the action of the wind turbine on the blade (for example during braking to regulate the speed of rotation of the wind turbine or during emergency braking).

  Therefore, the blades require a lot of rigidity to: maintain the geometry of the profile and therefore maintain the aerodynamic efficiency; avoid coming into contact with the mature, burst.

  But the blades must also be flexible in their structure to absorb the aerodynamic constraints mentioned above, and thus improve the fatigue behavior of materials.

  This desired structure both rigid and having a good damping power, must also be as light as possible to also contribute to improve the fatigue behavior (alternating force during rotation as the blade goes up or down) and therefore contribute to increase the life of the blade.

  A solution of the prior art is to manufacture a blade using two half-shells representing the lower surface and the upper surface of the wing, these half-shells being made of sandwich from foam core or in balsa with on both sides a fiber / resin skin.

  According to this technique, it is expected, for large blade dimensions, stiffeners forming a central beam, also made in sandwich, and connecting the intrados and extrados.

  The disadvantages of such a structure are multiple: behavior of the souls to fatigue due to the compression of the extrados skin and may lead to risk of ruin gluing the soul; behavior of the stiffeners when the blade is bent (risk of buckling of the skins and consequently detachment of the skins of the soul); transmission of vibrations directly to the hub, (the root of the blade and the skin being made in one and the same piece); high weight.

  Another solution of the prior art consists in forming these blades of an assembly comprising: a structural mast (that is to say, participating exclusively in the rigidity of the assembly) in several pieces; - a series of transverse ribs attached to the mast, giving the geometry of the profile; a skin in several pieces in its rope and in its length, dressing the ribs According to this solution, which takes again the architecture of a wing of windmill, the rigidity is given by the mat, the ribs defining the geometry of the profile, and the skin having a role of wind sensor. In this case, the skin participates only very little in the mechanical strength of the blade (especially when this blade is made in assembled sections, so the skin divided along its length can not participate effectively in the rigidity of the whole) .

  The mat, the main element of the structure, made of carbon for a better weight / stiffness-resistance ratio, alone takes up all the mechanical stresses and in particular the vibrations that it transmits directly to the hub. Such a solution has two major drawbacks.

  On the one hand, the inertia of the skin being higher than that of the mast, the increase of the mechanical characteristics by the mat is less advantageous in mass.

  On the other hand, the mast, the main element of the structure of the blade, retransmits all efforts, and particularly the vibrations, integrally and directly to the hub.

  The invention particularly aims to overcome the disadvantages of the prior art.

  More specifically, the invention aims to provide an aerogenerator blade whose structure has a high mechanical strength, while generating damping, to meet the aerodynamic constraints experienced by the blade.

  The invention also aims to provide such a wind turbine blade whose structure provides better durability compared to the blades of the prior art.

  The invention also aims to provide such a blade which is simple in design and easy to implement.

  These objectives, as well as others which will appear later, are achieved thanks to the invention which has for object, an airfoil blade of the type comprising at least one mast, a plurality of ribs coupled to said mast, at least one skin reported at least on said ribs, characterized in that said ribs are coupled to said mast by semi-rigid links and in that said skin is coupled to said ribs by also semi-rigid links.

  Such semi-rigid links, on the one hand between the mast and the ribs and, on the other hand, between the ribs and the skin, allow small relative displacements between the various elements constituting the blade and allow the vibrations to be attenuated. or shocks that the blade undergoes, whether because of the wind or because of the wind turbine itself.

  Indeed, in the absence of rigid connection between each of the elements constituting the blade due to the relative flexibility of semirigid links, the propagation of vibration between these elements is reduced, the semi-rigid links having a damping effect.

  Thus, the outer skin has a greater inertia and takes up most of the forces applied to the aerodynamic profile, which it retransmits progressively through the semi-rigid links to the ribs and the mast. The mast becomes, only in its most important section, an element of essential structure, that is to say, assuming by itself, or almost, the rigidity of the whole. By this design, the mat and skin structure elements are decoupled, which limits the transmission of vibrations In addition this concept provides a better weight / rigidity ratio than in the blades of the prior art.

  Furthermore, it is noted that the technique according to the invention also has the advantage that, in case of rupture of the outer skin (for example a carbon skin), the blade retains its structural integrity thanks to its mast which then resumes all efforts. This avoids, as is frequently seen with conventional solutions, a disintegration of the blade can cause damage to the other blades or the nacelle.

  This type of construction therefore limits the risk of propagation of damage and allows repair of the blade.

  According to a first embodiment, said adhesive has a shear strength of between about 8 MPa and about 15 MPa and a modulus of elasticity of between about 700 MPa and about 1500 MPa, for an adhesive seal thickness of between about 0.2 mm and 1 mm.

  Preferably, in the case of this first embodiment, said adhesive has a shear strength of about 10 MPa and a modulus of elasticity of about 1200 MPa, for a glue joint thickness of about 0.75 mm .

  According to a second embodiment, said adhesive has a shear strength of between about 15 MPa and about 35 MPa and a modulus of elasticity of between about 2000 MPa and about 5000 MPa, for an adhesive seal thickness of between about 0 , 5 mm and about 4 mm.

  Preferably, in the case of this second embodiment, said adhesive has a shear strength of about 20 MPa and a modulus of elasticity of about 3000 MPa, for an adhesive seal thickness of about 2 mm.

  The choice of one of these embodiments will be made according to the compromise between the shear strength and the thickness of the seal and also depending on the size of the blades.

  It is noted that the glue characteristics mentioned above are provided for an ambient temperature.

  The semi-rigid links are thus obtained using an adhesive having an ability to hold the elements securely together, while retaining a certain flexibility.

  It is noted that other embodiments can be envisaged to obtain the semi-rigid links, for example by inserting a damping material between the different elements and connecting the latter by mechanical means, possibly with a slight clearance, so as to allow the relative displacement of the different elements between them.

  However, the glue-like material is a preferred solution in that it exerts on its own a dual role: that of the holding of the elements together and that of damping.

  According to an advantageous solution, said glue material is applied in a given thickness by a calibration technique.

  Such a technique, known to those skilled in the art, ensures a uniform bonding thickness, which is essential for the characteristics of the blade are uniform in all respects, its length or almost.

  According to an advantageous solution, said mast is made of at least one material belonging to the following group: glass fibers; carbon fibers.

  Preferably, said mast is made by filament winding. According to a preferred solution, said ribs are made of glass fibers.

  Note that in the case of large blades, it is possible to use carbon.

  The sampling of the ribs gives them a certain flexibility. Thus, the transfer of the bending moment from the skin / mast assembly to the single mast is achieved by absorption of traction / compression forces in the skin. Only the residual forces (a large part having been absorbed by the ribs) are then retransmitted to the mast.

  This results in small deformations of the ribs, resulting in a relative displacement of the ribs relative to the mast which brings part, by dissipation of energy, a damping effect.

  Such a characteristic combined with the presence of the semirigid links contributes to further increase the relaxation of the blade structure, which further increases the ability of the blade to absorb vibration and shock generated by the wind and / or the wind turbine itself.

  According to a first embodiment, said ribs are prepreged with the hot press.

  According to a second embodiment, said ribs are made by injection.

  According to one or other of these embodiments, said ribs are made in at least a portion intended to be bonded to said mast.

  This characteristic contributes to confer a relative flexibility to the ribs and thus to increase their capacity to dampen certain shocks or vibrations.

  According to a preferred solution, said skin is made monolithically in at least one material belonging to the following group: glass fibers; carbon fibers.

  It is noted that the term "monolithic" is used here as opposed to the multi-material structure composed of a core with on both sides a composite fiber / resin, referred to as a sandwich, mentioned above.

  It is therefore necessary to understand this term in the broad sense: such a monolithic skin is made of a material (possibly composite) homogeneous with respect to its thickness.

  However, it is noted that this skin may consist of several parts assembled together and / or on the ribs, as is also the case in the context of the presentation will be made thereafter.

  Thus, according to an advantageous solution, said skin comprises at least two sections connected together, one said stretch extending on the face of said blade intended to be essentially exposed to the wind (called the intrados), the other said compressed (called the extrados) opposite to said stretched face.

  In this case, said compressed section and said stretched section are preferably connected by a junction section extending on the leading edge of said blade.

  Advantageously, said mast is made of at least two sections.

  This circumvents the difficulties inherent in the manufacture of large mast and assembled by gluing. Of course, the number of sections may vary as much as necessary depending on the length of the blade.

  According to another characteristic, the blade comprises stiffening means intended to limit the buckling phenomena of said blade.

  In this way, it limits local buckling of the face in compression of the skin, these buckling phenomena being likely to occur during the bending of the blade under the force of its rotation combined with the aerodynamic force it undergoes.

  Indeed, from the design of the blade, the outer skin formed by the leading edge, the so-called extrados skin (not subject to the wind) and the so-called intrados skin (subject to the wind) takes up a significant part of the efforts. Thus, during a significant deflection, the skin is caused to deform on its compressed face. These deformities occur between the veins on which the skin is stuck.

  The stiffening means provided according to the invention thus make it possible to remedy this drawback.

  Advantageously, said stiffening means comprise longitudinal stiffeners which preferably extend along the compressed face of the blade.

  According to a particular embodiment, said stiffening means also extend along the face opposite to said compressed face.

  According to a first embodiment of the stiffeners, these are discontinuous and extend between said ribs.

  According to a second embodiment of the stiffeners, these are inserted in at least one reservation formed in at least one rib. According to a first approach of the stiffening means, these are secured by gluing to said skin.

  According to a second approach of the stiffening means, these are embedded in said skin.

  Advantageously, said stiffening means consist of at least one carbon fiber profile or, according to one conceivable variant, at least one fiberglass profile.

  According to yet another characteristic, the blade comprises means for consolidating the trailing edge.

  In this case, said consolidation means are preferably provided such that said blade no longer has longitudinal fiber breakage. Indeed, with conventional blades, the connection between the aerodynamic profile at its maximum rope and the cylindrical root is found. of the blade generates at the trailing edge a discontinuity of longitudinal unidirectional fibers of the material of the skin of the profile in the direction of the root of the mast. This discontinuity generally causes term cracks, on the trailing edge and, consequently, openings of the profile at the junction of the intrados and extrados skins.

  The consolidation means provided according to the invention make it possible to remedy this drawback.

  According to a preferred solution, said consolidation means comprise at least one fairing.

  Thus, the trailing edge end of the skin of a conventional blade is replaced by this fairing which ensures the geometry of the trailing edge of the transition zone of the mast (zone of evolution of the cylinder of the root of the pale to the aerodynamic profile of the skin) to the profile beyond its maximum rope.

  The intrados and extrados skins are thus gathered under the fairing, thus allowing a continuity of the unidirectional fibers of the skin towards the mast.

  According to another conceivable embodiment, said consolidation means comprise at least one consolidation insert providing inside said blade, the connection between the face of the blade intended to be essentially exposed to the wind and the face opposite to said face. of the blade intended to be essentially exposed to the wind.

  Advantageously, said consolidation means are secured to said skin by gluing.

  The invention also relates to an aerogenerator carrying at least one blade as described above.

  Other characteristics and advantages of the invention will emerge more clearly on reading the following description of a preferred embodiment of the invention, given by way of illustrative and nonlimiting example, and the appended drawings among which: Figure 1 is a perspective view of the mast and ribs of a wind turbine blade according to the invention; FIG. 2 is a perspective view of the skin of an aerogenerator blade, according to a particular embodiment of the invention; FIG. 3 is a partial longitudinal sectional view of an aerogenerator blade according to the invention; FIG. 4 is a schematic cross-sectional view of an aerogenerator blade according to the invention; FIG. 5 is a detailed cross-sectional view of an aerogenerator blade according to the invention; Figures 6 to 8 are enlarged detail views taken from Figure 5; Figure 9 is a perspective view of a blade according to the invention, illustrating the presence of a fairing on the trailing edge of the blade; Figures 10 and 11 respectively illustrate the fairing element intended to be attached to the trailing edge of the blade and the housing formed in the blade to receive such a fairing; Figure 12 is a schematic sectional view of the blade equipped with the fairing illustrated in Figures 10 and 11; Figure 13 is a sectional view of a consolidation insert of the trailing edge.

  With reference to FIGS. 1 and 2, an aerogenerator blade according to the invention comprises a mast 1 made for example by filament winding of glass fibers (or of carbon according to another conceivable embodiment), on which a plurality of ribs 2 on which a skin is reported.

  It is noted that a possible variant is, for large blades, to achieve the mast in several sections assembled together.

  According to the present embodiment of the invention, the connection between the ribs 2 and the mast on the one hand, and the connection between the ribs 2 and the skin 3, on the other hand, consist of a bonding lip 4, consisting of a two-component polyurethane adhesive (in this case polyol and isocyanate) having, at ambient temperature, a shear strength of 10 MPa and a modulus of elasticity of 1200 MPa, this adhesive being applied with a thickness of 0.75 mm by means of a calibration technique (using calibration ribs on the parts to be glued or calibrated shims on the parts to be glued).

  It should be noted that other glues can be envisaged in other embodiments, and in particular epoxy glues having, for example, a shear strength of 20 MPa and a modulus of elasticity of 3000 MPa for a thickness of 2. mm.

  The ribs are made of glass fibers (or carbon), hot-press pre-impregnated (or injection-molded according to another conceivable embodiment) and consist, according to the present embodiment of two half-ribs glued between they and on the mast as will be explained in more detail later.

  As illustrated in Figure 2, the skin 3 is composed of several sections made monolithically into a mixture of glass fibers and carbon fibers and interconnected. According to the present embodiment, the skin is composed of the following sections: a section of skin intrados 31 (stretched), essentially subjected to the action of the wind; an extrados skin section 32 (compressed), facing the intrados skin 31; a joining section 33, extending over the leading edge of the blade and connecting the intrados skin section 31 and the extrados skin section 32.

  Referring to Figures 9 to 12, the skin 3 further comprises a fairing 34, forming consolidation means of the trailing edge of the blade, this fairing being assembled by gluing to the section of skin intrados 31 and to the section of skin extrados 32, they forming between them a housing (as shown in Figure 11) for receiving the fairing.

  FIG. 13 illustrates another embodiment of the means for consolidating the trailing edge of the blade.

  As it appears, the intrados skin 31 and the extrados skin 32 both extend to the trailing edge at which they meet, the connection between the intrados 31 and extrados skin 32 being consolidated by an insert 38 (in composite material) on which the skins 31 and 32 are glued.

  The assembly between them of the different sections of skin is illustrated by FIGS. 5 to 8.

  With reference to FIG. 5, an aerogenerator blade according to the present embodiment is constituted in particular by the assembly of: a mast 1; two half-ribs 21, 22 bonded together by an adhesive joint 23 in the manner illustrated in FIG. 8, these two half-ribs being bonded to the mast 1 as already mentioned previously using an adhesive two-component polyurethane; a section of intrados skin 31 and an extrados skin section 32 joining at the trailing edge in the manner illustrated in Figure 7; of a joining section 33, assembled to the intrados and extrados skin sections in the manner illustrated in FIG. 6.

  As it appears in FIG. 6, the intrados skin 31 (as well as the extrados skin 32) and the ribs 2 are shaped so as to sandwich the ends of the junction section 33 (leading edge of the blade.

  Note that the section 33 has protrusions 331 constituting calibration ribs to obtain a uniform thickness of adhesive.

  Referring to Figure 7, the trailing edge of the blade is partly (apart from the fairing described above) consisting of the assembly: sections of skin intrados 31 and extrados 32; a trailing edge profile 35; a connecting element 36 of the trailing edge profile.

  It is noted that the sections of skin intrados 31 and extrados 32 have a thickness which gradually decreases towards the trailing edge, to form together, at the trailing edge, a thickness of the order of 2 mm.

  According to another characteristic of the invention, stiffening means are provided for limiting buckling phenomena of the blade; With reference to FIG. 4, these means limiting the buckling of the blade consist of longitudinal stiffeners 37 constituted by fiberglass profiles (or carbon profiles according to a conceivable variant), glued to the sections of intrados and extrados skins. the skin 3, and extending along them by inserting in reservations 23 formed in the ribs 2.

  It is noted that other embodiments of the stiffeners 37 are conceivable, in particular by providing them so that they extend discontinuously between the ribs, or by embedding them in the skin 3.

Claims (29)

  1. Wind turbine blade of the type comprising at least one mast (1), a plurality of ribs (2) coupled to said mast (1), at least one skin (3) attached to at least said ribs (2), characterized in that that said ribs (2) are coupled to said mast (1) by semirigid links and in that said skin (3) is coupled to said ribs (2) by also semi-rigid links.   2. Wind turbine blade according to claim 1, characterized in that said semi-rigid links are provided by at least one adhesive material.   3. Wind turbine blade according to claim 2, characterized in that said adhesive has a shear strength of between about 8 MPa and about 15 MPa and a modulus of elasticity of between about 700 MPa and about 1500 MPa for a glue joint thickness of between about 0.2 mm and 1 mm.   4. Wind turbine blade according to claim 3, characterized in that said adhesive has a shear strength of about 10 MPa and a modulus of elasticity of about 1200 MPa, for a glue joint thickness of about 0. , 75 mm.   5. Wind turbine blade according to claim 2, characterized in that said adhesive has a shear strength of between about 15 MPa and about 35 MPa and a modulus of elasticity of between about 2000 MPa and about 5000 MPa, for a thickness adhesive seal between about 0.5 mm and about 4 mm.   6. Wind turbine blade according to claim 5, characterized in that said adhesive has a shear strength of about 20 MPa and a modulus of elasticity of about 3000 MPa, for a glue joint thickness of about 2 mm.   7. Wind turbine blade according to any one of claims 2 to 6, characterized in that said glue material is applied to a given thickness by a calibration technique.   8. Wind turbine blade according to any one of claims 1 to 7, characterized in that said mast (1) is made of at least one material belonging to the following group: glass fibers; carbon fibers.   11. Wind turbine blade according to claim 8, characterized in that said mast (1) is made by filament winding.   12. Wind turbine blade according to any one of claims 1 to 9, characterized in that said ribs (2) are made of glass fibers.   13. Wind turbine blade according to claim 10, characterized in that said ribs (2) are pre-impregnated with the hot press.   12. Wind turbine blade according to claim 10, characterized in that said ribs (2) are made by injection.   13. Wind turbine blade according to any one of claims 1 to 12, characterized in that said ribs (2) are made of at least two parts (21), (22) intended to be bonded to each other and to said mast ( 1).   14. Wind turbine blade according to any one of claims 1 to 13, characterized in that said skin (3) is made monolithically in at least one material belonging to the following group: glass fibers; carbon fibers.   15. Wind turbine blade according to any one of claims 1 to 14, characterized in that said skin (3) comprises at least two sections connected together, one said stretched (31) extending on the face of said blade intended to be essentially exposed to the wind, the other said compressed (32) opposite said stretched face.   16. Wind turbine blade according to claim 15, characterized in that said compressed section (32) and said tensioned section (31) are connected by a connecting section (33) extending on the leading edge of said blade. 17. Wind turbine blade according to any one of claims 1 to 16, characterized in that said mast (1) is formed in at least two sections.   18. Wind turbine blade according to any one of claims 1 to 17, characterized in that it comprises stiffening means for limiting the buckling phenomena of said blade.   19. Wind turbine blade according to claim 18, characterized in that said stiffening means comprise longitudinal stiffeners (37).   20. Wind turbine blade according to one of claims 18 and 19, characterized in that said stiffening means extend along the face of the blade intended to be substantially exposed to the wind.   21. Wind turbine blade according to claim 20, characterized in that said stiffening means also extend along the face opposite to said face intended to be essentially exposed to the wind.   22. Wind turbine blade according to any one of claims 19 to 21, characterized in that said stiffeners (37) are discontinuous and extend between said ribs (2).   23. Wind turbine blade according to any one of claims 19 to 22, characterized in that said stiffeners (37) are inserted into at least one reservation (23) formed in at least one rib (2).   24. Wind turbine blade according to any one of claims 19 to 22, characterized in that said stiffening means are embedded in said skin (3) 25. Wind turbine blade according to any one of claims 19 to 24, characterized in that said stiffening means is constituted by at least one carbon fiber profile.   26. Wind turbine blade according to any one of claims 19 to 24, characterized in that said stiffening means are constituted by at least one fiberglass profile.   27. Wind turbine blade according to any one of claims 1 to 26, characterized in that it comprises means of consolidation of the trailing edge.   28. Wind turbine blade according to claim 27, characterized in that said consolidation means are provided such that said blade has substantially continuous longitudinal fibers.   29. Wind turbine blade according to one of claims 27 and 28, characterized in that said consolidation means comprise at least one fairing (34).   30. Wind turbine blade according to one of claims 28 and 29, characterized in that said consolidation means comprise at least one consolidation insert (38) providing, inside said blade, the connection between the face of the blade intended to be essentially exposed to the wind and the face opposite to said face of the blade intended to be essentially exposed to the wind.   31. Wind turbine blade according to claim 29, characterized in that said consolidation means are secured to said skin by gluing.   32. A turbofan bearing at least one blade of the type comprising at least one mast (1), a plurality of ribs (2) coupled to said mast (1), at least one skin (3) attached to at least said ribs (2), characterized in that said ribs (2) are coupled to said mast (1) by semi-rigid links and in that said skin (3) is coupled to said ribs (2) by also semi-rigid links.