WO2018015647A1

WO2018015647A1 - Blade intended to be mounted on a wind turbine comprising a wing structure rotating about a beam slid inside

Info

Publication number: WO2018015647A1
Application number: PCT/FR2017/051945
Authority: WO
Inventors: Bertrand RICHER
Original assignee: DE BRISOULT, Dominique
Priority date: 2016-07-21
Filing date: 2017-07-17
Publication date: 2018-01-25
Also published as: FR3054268A1

Abstract

Proposed here is a blade intended to be fitted to the variable-pitch rotors of a wind turbine, the blade comprising a wing structure forming a rigid elongate exterior surface affording maximum lift in a given direction. This blade also comprises a beam extending inside the wing structure in a substantially longitudinal direction. The ring structure being coupled to the said beam by at least two bearing points, a first bearing point being situated near the blade root, and a second bearing point being situated at the end of the beam and comprising a means of rotation coupling the internal structure of the wing structure in terms of rotation to the end of the beam opposite the blade root end. This blade arrangement is capable of adapting more quickly to the variations in load caused by the wind and may better withstand the stresses applied by turbulence. The structure of the blade is supported by two bearers that are far enough apart that they are able effectively to absorb bending moments.

Description

Pale intended to be mounted on a wind turbine having a wing rotating around a beam slid inside.

1. DOMAIN OF THE INVENTION

The field of the invention is that of wind turbines equipped with a hub supporting a plurality of blades arranged radially, the wing of each of these blades being able to turn on itself once mounted on the hub so as to vary its pitch. The invention relates more particularly to the fact that the rotation of the wing is performed around a beam slid inside and fixed to the hub.

2. TECHNOLOGICAL BACKGROUND

In recent decades, wind turbines, also known as "wind turbines" are increasingly used and provide a growing share of electric power. Over the years, wind turbines have grown in size to be more efficient and their power is currently more than 3 megawatts per unit. In addition to increasing the size of wind turbines for power generation, wind turbine rotor blades have also increased in length to 40 meters, and an 8 megawatt prototype is being explored. a blade 88 meters long.

The blade is generally formed of a wing consisting of a skin connected to the hub by connecting elements such as screws and nuts, the skin constitutes the outer casing of a volume possibly comprising ribs to strengthen the structure. For blades of very large size, the thickness of the wing is increased to better withstand the aerodynamic forces. This thickness causes a very significant increase in weight. As the size of the wind turbines increases, it also becomes a technical and economic imperative to be able to control and minimize the asymmetric aerodynamic loads acting on the propeller so as to reduce the fatigue phenomena of the materials.

Nowadays, almost all wind turbines are equipped with a power control system. This control system generally consists of an anemometer for measuring wind speed and a device acting on the power motor, allowing them to adapt to different wind configurations. This regulation and protection function has been provided by devices acting on various components of the wind turbine. Of all the solutions, the one that consists of pivoting the blades along their longitudinal axis is the one that has imposed itself technically and is used on the vast majority of large wind turbines. In very strong or gusting winds, this control function effectively protects the unit because the blades are swiveled very fast. By offering less resistance to wind, the stresses are reduced, which requires blades less reinforced and whose lighter, and consequently, manufacturing costs are thus reduced.

The individual control of the pitch of each blade assumes the mastery of two main technical constraints:

- Free rotation of the blade around its longitudinal axis. On known wind turbines, this function is provided by an orientation ring which must be strongly prestressed in order to eliminate the mechanical games under heavy load. This preload causes a high torque and if the speed of variation of the setting is high, a large power will be required to the actuator;

a precise measurement of the aerodynamic force applied to the blade in order to be able to correct its value by adjusting the angle of rigging. This measurement is performed by strain gauges placed on the blade root. A disadvantage of this solution is the lack of reliability over time and the need to perform regular calibrations. As an alternative to this solution, it is possible to measure the pivoting torque at the foot of the blade, this torque being correlated more or less closely to the bending force that is to be controlled. But this measure of torque can be useful only if certain parasitic effects are eliminated or significantly reduced, these parasitic effects are:

- the torque caused by the prestressing of the orientation ring,

- Bending deformation of the blade under the aerodynamic force causing a strong shift of the application points of the aerodynamic forces relative to the pivot axis especially at the end of the blade. Patent NL 1 007 538 Cl published May 17, 1999 describes a blade having a frustoconical beam inserted inside the wing, the connection between the wing and the beam being provided by a roller bearing or ball bearing at the end. of the beam, and by two groups of rollers, one to half-length of the beam and the other near the hub. This means of rotation can not take into account the bending movements of the wing relative to the beam.

Patent GB 2 479 380 A published October 12, 2011 describes a wind turbine having a hub provided with a plurality of axes penetrating inside the cylindrical structure of blade root, the pivoting being provided by two coaxial bearings. This assembly has a very high rigidity which does not support the movements of flexion of the blade.

There is therefore a real need for a new arrangement of blades capable of adapting more quickly to the variations of forces caused by the wind and more able to withstand the stresses exerted by the turbulence. According to another objective, the new blade arrangement will have to be lighter to allow in particular large lengths.

3. STATEMENT OF THE INVENTION

In a particular embodiment of the invention, there is provided a blade intended to equip variable pitch propellers of an aerogenerator, the blade having a blade forming a rigid elongated outer surface providing maximum lift in a given direction. This blade further comprises a beam extending inside the wing in a substantially longitudinal direction. The wing being coupled to said beam by at least two support points, a first support point being located near the blade root, and a second support point located at the end of the beam and having a rotation means coupling in rotation the internal structure of the wing at the end of the beam located opposite the blade root, the wing rotating around the beam between two given angular positions.

Thus, the solution proposes a new blade arrangement which better distributes the forces in flexion and torsion over the entire length of the blade. The wing of the blade is carried by two supports sufficiently distant from each other to resume effectively bending moments that have the distinction of being very important at the point of attachment of the blade with the hub.

According to a first embodiment, the shape of the beam is frustoconical, the greatest revolution being at the level of the blade root. In this way, the manufacture of the beam is easy and the rotation of the wing is facilitated.

According to another embodiment, the means of rotation at the end of the beam is a rotary bearing, fixed to a rib extending transversely to the inside of the wing. In this way, the coupling between the beam and the wing is ensured.

According to another embodiment, the beam extends inside the canopy over a length ranging from 20 to 75% of the total length of the blade, preferably 60%. In this way, the aerodynamic forces applied on the wing are taken up by the beam.

According to another embodiment, the fulcrum at the level of the blade root consists of two concentric cylindrical pads, the pads in contact with each other being covered with a material promoting sliding. In this way, the rotation of the wing around the beam is facilitated and does not require significant power to control the pitch.

According to another embodiment, the blade is rotated by a servomotor located at the blade root, the servomotor being accessible by at least one access door cut in the trailing edge of the blade. In this way, the maintenance of equipment placed inside the blades is facilitated.

According to another embodiment, the servomotor is controlled by a regulation loop taking into account in particular the pitch force at the blade root, and delivering a signal to the servomotor to position the pitch of the blade. In this way, the bending moment measured on each blade is maintained at the most constant value possible.

According to another embodiment, the blade comprises at least a third bearing point lying between the first and the second, thus taking up the bending forces of the wing. In this way, the deformation of the wing follows more that of the beam In another embodiment of the invention, there is provided a method of assembly on a turbine generator described according to any one of the preceding paragraphs, comprising in particular the following steps:

- transport of wings and beams separately,

radial mounting around the rotary hub of the wind turbine generator of a plurality of beams,

- Engagement of wings around each beam to a specific depth where the elements of the wing and beam constituting each means of rotation are in contact,

- Fixing the elements of the wing and the beam constituting the means of rotation to prohibit the translation of the wing and the beam while allowing rotation.

In another embodiment of the invention, there is provided an aerogenerator having on its rotary hub a plurality of blades according to any one of the preceding paragraphs.

4, LIST OF FIGURES

Other features and advantages of the invention will appear on reading the following description, given by way of indicative and nonlimiting example, and the appended drawings, in which:

FIG. 1 is an overall view of a wind turbine according to the invention,

FIG. 2 shows a perspective view of a blade having a beam inside according to an exemplary embodiment,

FIG. 3 shows a longitudinal section of the blade presenting the points of contact between the beam and the wing according to an exemplary embodiment,

FIG. 4 shows an alternative embodiment in which the point of support at the level of the blade root comprises a connection of the diaphragm type,

FIG. 5 shows a transverse view of the ball joint fixed to the end of the beam, according to an exemplary embodiment; FIG. 6 shows a diagram of the interior of the blade showing the attachment of the ball joint on the wing, according to an exemplary embodiment,

FIG. 7 presents a perspective view of the section of the blade at the location where the ball and the end of the beam are located,

FIG. 8 shows another perspective view of the section showing the reinforcing spars of the blade,

FIG. 9 shows an example of a ball joint placed at the end of the beam allowing the wing to rotate,

FIG. 10 shows an exemplary diagram of the point of support of the wing on the beam near the blade root,

Figure 11 shows a section of the beam near the blade root, Figure 12 illustrates an example of the actuator arrangement rotating the wing around the beam.

DETAILED DESCRIPTION

In all the figures of this document, identical elements are designated by the same reference numeral.

5 J_General principle

The invention relates to a blade for equipping variable pitch propellers of an aerogenerator. The blade comprises a blade forming a rigid elongated outer surface providing maximum lift in a given direction, and a beam extending inside the wing in a substantially longitudinal direction. The wing is coupled to said beam by at least two support points, a first support point being located near the blade root, a second support point located at the end of the beam and having a means rotationally coupling the internal structure of the wing at the end of the beam located opposite the blade root. The means of rotation at the end of the beam is a ball joint, which is attached to at least one rib extending transversely to the inside of the wing. 5 • First mpdes _. of realization

Now, with reference to FIG. 1, a wind turbine according to the invention comprising:

- a mast 1 anchored to the ground by foundations,

a nacelle 2 housing an electric generator 3, and a control unit 4,

a hub 5 located at the end of the propeller shaft which is coupled to the generator with possibly a reduction system,

- A plurality of blades 6 rotatably mounted on the hub, the blade having an outer wing.

The rotation of each blade between two given angular positions makes it possible to vary its pitch and therefore its lift to the wind.

Fig. 2 shows a perspective view of a blade having a beam inside according to an exemplary embodiment of the invention. The beam 10 is inserted inside the wing 11 from the blade root 12 to a determined depth and allows the rotation of the wing around it. The length of the beam varies from 20% to 75% of the total length of the wing, that is to say the blade since the beam is completely covered by the wing.

The length of the beam is defined experimentally and is a compromise between different often conflicting constraints, one of the constraints imposes to minimize the deformation of the wing so as not to have any problem of contact between the inside of the wing and the outside. of the beam, this first constraint imposes a coupling in rotation as close as possible to the blade root, the second important constraint requires placing the coupling in rotation sufficiently far from the blade root so that the pivot axis of the The blade closely follows the sections of the canopy subjected to the most important aerodynamic forces. The largest aerodynamic forces are in the 70-85% range of the total blade span, resulting in a preferred 60% position. Thus for a blade of 66 meters, the beam inserted inside has a length of 39.60 meters (+/- 2 meters). If the compromise is not satisfactory, there remains the possibility of adding one or more intermediate bearings mid length of the beam so as to guide the deformation of the wing according to that of the beam. For example, if only one intermediate bearing is laid, its position is 35% of the length of the blade, which offers the possibility of placing the coupling in rotation at 70% of the length of the blade. The calculation is an optimization work where each step is validated by simulation calculations.

The section of the beam is preferably conical, which does not exclude more complex sections for example cross-welded sheets. The beam is preferably made of composite materials, mainly for reasons of weight, but it is possible, given the simple form of this element, to make it out of steel or any other economically interesting material.

Fig. 3 shows a longitudinal section of the blade highlighting the points of contact between the beam and the wing according to an exemplary embodiment. The beam is in contact with the wing by at least two points of support. In this way, the outer structure of the blade constituting the wing is supported by a support at the cylinder constituting the blade root 12 and at least one other support at the end of the beam.

According to a preferred embodiment, the fulcrum at the end of the beam consists of a ball joint 14 composed of two concentric rings.

The inner ring is mechanically connected to the end of the beam, and the outer ring is mechanically attached to a transverse rib 13 of the wing. This ball joint allows the rotations along the three axes, the longitudinal axis of the blade and thus allows adjustment of the setting of the blade. According to a variant, a ball bearing is added to the ball joint to ensure the rotation function along the longitudinal axis, this equipment reduces as much as possible the rotational friction torque.

To this link ball joint is attached a fastening system at the end of beam that can be manipulated remotely from the blade root. The end of the threaded axis of the ball is engaged in a metal part pierced at the end of the beam, in the inner part of the beam a pivoting and threaded element is screwed onto the ball axis. Screwing this element is controlled from the blade root by an axis guided along the inside of the beam and actuates through a gear reduction gear rotation of the element screwed onto the axis of the ball joint. This connecting element must be sized to withstand the centrifugal forces acting on the mass of the wing and this whatever the speed of rotation of the rotor. A variant of this connection system would be to use a hydraulic control to ensure that remote screwing or any other locking system of an axis in a bore such as hooping.

At the level of the blade root, the support between the wing and the beam is made by two coaxial and sliding circular cylinders, whose surfaces facing each other are placed inside the wing and outside the wing. central beam. This support is free in rotation by the sliding of the bearing surfaces, a slight longitudinal movement is also permitted by the sliding of the bearing surfaces. The contacting surfaces advantageously consist of pads 15 covered with a low friction material and wear resistant, polytetrafluoroethylene (or PTFE abbreviated) for example.

The thrust force exerted by the wind on the blade is mainly taken up by the ball offset to the middle of the blade, and the residual thrust force at the blade root is easily taken up by the pads.

Such an assembly deviates significantly from the known provisions of using an orientation ring whose diameter is limited to that of the blade root and for which the dominant force is a bending force. The large distance of the bearing points characterizing the invention allows the use of bearings which will be subject mainly to radial forces, easier to control and to friction forces much lower than those of a slewing ring. .

On a wind turbine blade, the bending moment is very weak at the end of the blade and increases rapidly to become maximum at the foot of the blade. The presence of the beam inside and the points of support coupling it with the wing makes it possible to transfer this bending moment from the wing of the blade towards the inner beam. In this way, from the swivel support and towards the blade root, the bending force supported by the outer blade blade decreases to completely cancel itself level of the blade root due to the free connection in rotation along the 3 axes. The bending moment continues to increase on the inner beam going towards the blade root. This load transfer effect has the advantage of transferring the mass of the structure from the wing 11 to the beam 10 and thus not to substantially increase the total mass of the blade.

Fixing the beam on the hub 5 is performed according to a technique known per se, for example by screws and nuts. This method of attachment is much simpler than those of incorporating a rotation mechanism of the blade. According to the present invention, the servomotor controlling the rotation of the wing around the beam is located at the blade root, preferably in the trailing edge of the wing. Indeed, at this place is a volume large enough and protected to place bulky devices. Access hatches are made in the wing to access the servomotor. The present invention authorizes the cutting of the blade at the blade root, because of the transfer of bending forces of the wing to the central beam as and when we approach the blade root. These access hatches from the outside to the inside of the wing do not compromise the overall strength of the wing which will be much less solicited at this location. From the top of the nacelle of the wind turbine, easily accessible place for known wind turbines, operators can easily access the interior of the wing.

The servomotor is controlled by a control loop comprising a control unit receiving sensor information and actuating the servomotor controlling the rotation of the wing around the beam. The sensor makes it possible to measure the pitching force at the foot of the blade (also called "pitch moment"). The present invention makes it possible to position the center of aerodynamic thrust relative to the axis of pivoting of the blade, so as to render said aerodynamic thrust on the whole blade proportional to the pitching moment measured at the foot of the blade. The regulation comprises a so-called "primary" loop which acts collectively on the pitch of all the blades to maintain the power of the wind turbine below a nominal value. The regulation comprises a so-called "secondary" loop which acts individually on each blade. This secondary loop takes into account the value of pitching effort measured at the foot of each blade, ie the bending moment and acts on the pitch of this blade to keep it as constant as possible. The response time of the secondary loop is faster than that of the primary loop.

According to an exemplary embodiment, the sensor measures the pressure in a cylinder integrated in the servomotor or an electrical quantity (voltage, current) if the actuator is completely electrified. In this way, the command / measurement assembly is perfectly compact and it is useless to place sensors at other locations on the blade. The response to the pitch force is a pitching movement, which is why the sensor and the actuator are affected by the same degree of freedom of the blade. According to another embodiment, the actuator is a spring with a controlled stiffness, such a mechanism is sometimes present on hydropneumatic suspensions or competition car suspensions.

According to an improvement described in FIG. 4, the fulcrum at the level of the blade root has a freedom of rotational movement obtained by a diaphragm-type connection 16 between the wing and one of the sliding tubes 15 around the blade root. This diaphragm connection ensures a good waterproofness in particular, and increased mobility. According to one variant, this connection can be made by a simple ball joint, consisting of a circumferentially rounded ring.

The blade arrangement thus described overcomes certain limitations specific to the designs of large wind turbines developed at the time of filing of the present application and thus facilitate the individual control of each blade, while providing simplification and increased reliability for small and medium sized wind turbines.

In certain configurations of extreme forces, the wing deforms, which can put its internal surface in contact with the outer surface of the beam. To avoid this situation and according to an improvement, one or more intermediate bearings are placed between the two ends of the beam. These intermediate bearings comprise a connection in rotation, either by rolling or slip rings, mounted on one or deformable structures connected to the outer wing. Spacers, used in conventional wind turbine blade structures and intended for resumption of shear forces and ensure adequate buckling resistance, are used in particular to achieve the bearing structure of the intermediate bearing or bearings.

Large wind turbines raise transportation and handling problems because of the large dimensions of certain elements such as blades. The blade arrangement thus described, because of the recovery of the bending forces by a monobloc central element, is more easily subdivided into sub-elements of smaller size. The length of the blades as described in the present application can be greatly reduced to a division by two of the length of the larger element relative to the length of the complete blade.

By using the provision object of the application, it is possible to place an actuator and a translational guide at the connection between beam end and wing, and thus allow movements in the direction leading edge / trailing edge. Proper management of these movements can dampen the resonance phenomena of the blade in this direction. This freedom of movement is also used to adjust the coupling between the aerodynamic lift force and the longitudinal rotation torque (pitching moment).

The mounting of this type of blade on a wind turbine is facilitated because of the arrangement in two parts: the wing and the beam. An example of a procedure for installing a wind turbine equipped with blades described in the present application is now described. At first, the wings and beams are transported separately to the place of installation. The mat and the basket are mounted. Then the beams are radially fixed around the rotating wind turbine hub. The wings are then engaged around each beam to a specific depth where the elements of the wing and the beam constituting each rotation means are in contact. The bearing points are coupled and secured so as to ensure a frictionless rotation of the blade around the blade and a translation attachment of the blade so that it does not disengage from its beam during the rotation of the blade. the propeller.

The blade arrangement described in the present application provides numerous advantages including: - Economy of the slewing ring between the blade root and the hub, replaced by a bearing and a ball or a single bearing of a few kilograms at the end of the beam and a coaxial sliding guide device at the bottom of the blade;

- virtually eliminating the rotational friction forces providing a means for precise evaluation of the forces acting on the blade and a low power required to the calibration control actuator;

- On the area covered by the beam the forces on the outer wing of the blade are greatly reduced, which gives more freedom to the designer to optimize the outer shape of the blade compared to the aerodynamic aspects, while on the conventional solution the shape of the blade, as one approaches the foot, is optimized for the mechanical constraints which goes against the aerodynamic performances;

the central beam is of conical shape, which makes its production feasible with processes for manufacturing composite structures that can be automated, such as filament winding;

- The beam that supports the majority of efforts can be manufactured in one piece without the use of gluing joints that remain a tricky points to deal with the conventional design;

- In existing equipment, the deflection of the blade induces the offset of the point of application of the aerodynamic forces relative to the pivot axis of the blade. The arrangement described in the present application can significantly reduce this disadvantage because the support at the end of the beam accompanies the deflection of the wing and thus the pivot axis tilts with the blade;

- The slewing ring providing the rotational connection with the hub of the propeller subjected to very large bending moments deforms producing a leverage effect that significantly increases the traction on the fastening studs. The absence of slewing ring simplifies the design of the connection between the foot of the beam and the hub of the propeller; the arrangement described in the present application provides a very important gain in terms of safety, because it allows a feathering of the blade if the calibration control effort is to disappear for an accidental cause. In existing equipment, the calibration control system must provide a backup power supply or a compressed air tank to ensure this function in case of a fault. The arrangement described herein allows the wind force itself to provide pivoting in the safety position.

5. A particular RMQ

Fig. 5 shows a transverse view of the ball fixed to the end of the beam, according to a particular embodiment. The end of the beam 10 passes right through a ball 20 constituting the inner part of the ball joint. This ball is securely attached to the end of the beam on one side by a hemispherical stop 21, and on the other by a nut 22 separated from the ball by a washer 23, the nut clamping on the threaded end of the beam. The convex surface of the ball 20 of the ball joint cooperating with the concave surface of an outer ring 24 so as to maintain it inside and allow rotational movements between the axis of the wing and the axis of the beam. This arrangement has the advantage of allowing angular deviations caused by the bending movements of the wing under the effect of a strong wind. The presence of the ball 20 and the outer ring 24 is sufficient to allow the rotation of the wing around the beam. To reduce friction and in an improvement, the ball is provided with two needle bearings 25 placed between the outer ring 24 and the portion of the support 26 secured to the wing. If the bearings 25 and / or 26 are seized, the joints 20 and 21 are able to ensure the pivoting of the blade with a little more friction, to operate the blade until the intervention of maintenance teams.

Advantageously, the ball has a ball bearing or oblique roller 27 for which the contact between the rollers and the raceways is performed along an axis inclined relative to the plane normal to the axis of rotation of the shaft . The centrifugal force generated by the mass of the wing in rotation is directed according to a longitudinal direction to the blade. This force is effectively taken up by this oblique bearing which makes it possible to take up the axial loads, in other words this bearing serves in particular to stop the forces exerted on the ball in a longitudinal direction to the blade.

The ball 14 is firmly held in a support having at least two flanges 27 which is themselves secured to the wing.

Fig. 6 shows a sectional diagram of the inside of the blade showing the attachment of the ball 14 inside the wing, according to an exemplary embodiment. Remember that the wing 11 consists of two faces called extrados and intrados, each face being connected to the front by the leading edge and rearward by the trailing edge. The flanges 27 of the patella are immobilized in a rigid structure having straight ribs 28 attached to both sides of the wing extending transversely and forming an "X" whose directions converge towards the center of the ball joint. In this way, all centralized efforts on the ball joint are taken up by a rigid structure secured to the wing.

Fig. 7 shows a perspective view of the section of the blade at the location where the ball and the end of the beam. The ribs of the structure forming an "X" extend in two directions forming planes to increase the strength of the assembly. The ribs are connected in pairs by a flank 30 whose surface is perpendicular to the axis of the beam, this flank is pierced by a round hole to give access to the fastening nut 22. In addition to the faces of the wing 11, the ribs are also attached to longitudinal members 31 extending longitudinally inside the wing.

Fig. 8 shows another perspective view of the section showing the reinforcing beams of the blade. The ball 14 is securely fixed in the structure formed by the ribs 28 forming an "X". In the exemplary embodiment, the wing comprises two longitudinal longitudinal members 31 plane. By placing the blade vertically, one of the spars becomes a floor allowing an operator to move in the blade and to intervene on the ball joint. The intervention is facilitated by the presence of a hatch 32 visible in FIGS. 6 and 7, which allows in particular the mounting of the ball and the tightening of the nut.

Fig. 9 shows an example of a ball joint placed at the end of the beam allowing the rotation of the wing. The beam 10 passes through the ball 20 which is in the middle of the ball. The needle or roller bearings are located in a cage forming a ring which is closed by two lids 35 pierced with orifices 36 for their attachment. Such a ball has a diameter of 30 centimeters for a blade approximately 60 meters long.

Fig. 10 shows a diagram of the point of support of the wing on the beam near the foot 12 of blade according to a particular embodiment. The fulcrum 15 between the wing 11 and the beam 10 at the level of the blade root 12 is also a ball formed of an outer ring 37 secured to the inner wall of the wing, and an inner ring 38 on the beam side . The surfaces in contact with these two coaxial rings are curved. The mobility of the two rings allows itself to rotate the wing around the beam. To reduce friction and according to an improvement, the fulcrum 15 comprises a needle bearing 39 placed between the inner ring 38 and the surface of the end of the beam 10. It can be seen in this figure that the end 40 the beam has an extra thickness to stiffen its connection with the hub.

According to an alternative embodiment, the ball formed by the rings 37 and 38 is fixed to the wing 11, and the needle bearing 39 is secured to the beam.

Fig. 11 has the end of the beam near the blade root. Fixing the foot of the beam 10 is done directly on the means which avoids using an orientation ring. The end 40 of the beam has an extra thickness allowing the introduction of inserts in the edge of the beam. These inserts whose inner hole is threaded are directly embedded in the composite of the beam to allow screwing of the fastening nut with the hub 5 of the propeller. A short distance from its end 40, the beam is covered with a tread 41 on which is stretched a strap to rotate the wing 11 around the beam 10. Fig. 12 illustrates an example of an arrangement of a servomotor rotating the wing around the beam. The servomotor 42 is fixed by a rigid structure inside the blade near the blade root and at a place where the available volume is sufficient. The servomotor exerts a force tangential to the circular surface of the beam 10 to generate a moment of force so as to rotate the blade around the beam. According to an exemplary embodiment, the axis of the servomotor has a pulley which exerts traction on a belt 43 in a loop, said belt surrounding the beam 10. According to a non preferred but possible embodiment variant, the surface 41 of the beam is notched and cooperates with a toothed pulley with the same pitch, driven in rotation by the servomotor 42. These assemblies make it possible to individually vary the pitch of each blade 6 of the propeller of the wind turbine and thus change the lift of each blade face to the wind.

It should be obvious to those skilled in the art that the present invention allows embodiments in many other specific forms without departing from the scope of the invention as claimed. Therefore, the present embodiments should be considered by way of illustration but may be modified in the field defined by the scope of the appended claims.

Claims

A blade for equipping variable pitch propellers with an aerogenerator, the blade having a blade (11) forming a rigid elongate outer surface providing maximum lift in a given direction, said blade having a beam (10) extending to the interior of the wing in a substantially longitudinal direction, the wing being coupled to said beam by at least two support points, a first support point (15) located near the blade root, a second fulcrum located at the end of the beam and having a rotation means (14) coupling in rotation the internal structure of the wing at the end of the beam located opposite the blade root, the blade being characterized in that that the means of rotation (14) at the end of the beam is a ball joint, fixed to at least one rib (13, 28) extending transversely to the inside of the wing.

Blade according to claim 1 characterized in that the shape of the beam (10) is frustoconical, the largest revolution being at the level of the blade root.

Blade according to any one of the preceding claims, characterized in that the beam (10) extends inside the canopy over a length varying from 20 to 75% of the total length of the blade, preferably 60%.

Blade according to any one of the preceding claims, characterized in that the fulcrum (15) at the level of the blade root consists of two concentric cylindrical pads, the pads in contact with each other being covered with a material promoting sliding.

5. blade according to any one of claims 1 to 3, characterized in that the fulcrum (15) at the blade root is formed by a single ball joint having two coaxial rings whose contact surfaces are curved. Blade according to claim 5, characterized in that the inner coaxial ring comprises a needle bearing allowing its rotation with a minimum of friction around the beam.

Blade according to any one of the preceding claims, characterized in that the blade (11) is rotated by a servomotor fixed to the blade and located at the level of the blade root, said servomotor exerting traction on a loop strap surrounding the beam.

Blade according to claim 7, characterized in that the servomotor is controlled by a control loop taking into account the pitch force at the blade root, and delivering a signal to the servomotor to position the pitch of the blade so that effort does not exceed a certain threshold.

Blade according to any one of the preceding claims, characterized in that it comprises at least one third bearing point lying between the first and the second, the at least one third bearing point taking up the bending forces of the wing.

Blade according to any one of the preceding claims, characterized in that the ball (14) located at the end of the beam comprises two coaxial rings whose contacting surfaces are curved.

Blade according to any one of the preceding claims, characterized in that the ball (14) located at the end of the beam comprises at least one needle bearing.

12. Blade according to any one of the preceding claims, characterized in that the ball (14) at the end of the beam comprises at least one oblique roller bearing fixed to the wing. Blade according to any one of the preceding claims, characterized in that the ball (14) is fixed to both sides of the wing by a rigid structure comprising straight ribs attached to both sides of the wing and forming an "X" whose directions converge towards the center of the patella.

Blade according to claim 13, characterized in that it comprises at least two longitudinal members extending longitudinally inside the wing and attached to the rigid structure forming an "X", one of said longitudinal members forming a horizontal floor allowing a operator to intervene on the patella.

A method of mounting on a turbine generator described as described in any one of the preceding claims, characterized in that it comprises the following steps:

transporting the wings (11) and the beams (10) separately,

radial mounting around the rotary hub of the wind turbine generator of a plurality of beams (10),

- engagement of wings (11) around each beam to a given depth where the elements of the wing and the beam constituting each means of rotation (14) are in contact, said rotation means placed at the end of the beam being a ball joint attached to a rib (13) extending transversely to the inside of the wing,

16. A turbofan characterized in that it comprises on its rotary hub a plurality of blades according to any one of claims 1 to 14.