Rotor blade for a wind power installation

ES 2 397 263 T3

DESCRIPTION

Rotor blade for a wind power installation

The present invention relates to a rotor blade for a wind energy installation, as well as a wind energy installation with at least one rotor blade according to the invention.

Rotor blades for wind energy installations are generally known and can also be seen in every wind energy installation. These rotor blades have an outer shape that takes special aerodynamic requirements into account. In order to save material and weight, these rotor blades are generally composed of a first internal supporting structure and a surface that surrounds this first supporting structure, favorably aerodynamically configured. Documents FR 2290 585, FR 2587675 disclose rotor blades with a deformable surface.

In the case of large wind power plants, the rotor blades acquire considerable dimensions for reasons of aerodynamics. This affects, on the one hand, manufacturing and transport, and, on the other hand, the loads acting on the wind power installation during operation. These are produced in particular by the blade surface that automatically grows with increasing size, as well as the enlarged surface swept by the rotor blades.

Wind power installations must be designed according to predetermined directives for specific load cases. These are, on the one hand, the loads that occur during operation (so-called operating loads) and, on the other hand, the so-called extreme load cases. These cases of extreme loads are derived from certain situations or breakdowns, such as a fall of the network, a failure of the blade adjustment, an extraordinarily intense wind gust (50-year gust, etc.).

In this case it is understood that the loads transferred by the rotor blades to the installation depend essentially on the surface of the rotor blade exposed to the wind. For the extreme load calculation it is assumed that the entire rotor surface is exposed to a maximum wind. All the following components, such as drive branch, machine support, tower, foundation, etc. they must be designed accordingly.

As a result, the smaller the wind attack surface, and in particular the surface of the rotor blade, the lower the load level for which the installation must be designed. This also means less material waste and consequently lower costs.

Against this, there is also a minimum surface size necessary for aerodynamic reasons to be able to apply the forces necessary for the operation of the wind power installation, the rotation of the generator. In this case, it is disadvantageous in the case of known rotor blades that in particular in the region close to the blade base a rotor blade depth is required which also increases with increasing rotor blade dimension. This depth becomes so great that road transport of such a rotor blade is no longer possible or only at a disproportionately high expense.

The aim of the present invention is therefore to specify a rotor blade with which the described disadvantages are avoided and which presents the aerodynamically necessary surface area.

The object is solved according to the invention with a rotor blade having the characteristics according to claim 1. Advantageous variants are described in the other claims.

The invention is based on the knowledge that during normal operation of the wind power installation a certain rotor blade surface (nominal surface) is necessary, while this is too large in extreme wind and, for example , under certain circumstances in a transportation situation.

According to the invention, it is therefore proposed to improve a rotor blade of the type mentioned at the beginning so that a part of the surface can be actively deformed or can be moved.

In a preferred embodiment of the invention a part of the surface is formed of a deformable material that is part of a closed container. This closed container can be filled, for example, with a gaseous medium, applying a predetermined pressure to this gaseous medium. In this way a partially inflatable surface of the rotor blade is produced which can deflate during transport or when extreme wind occurs and therefore requires less space or yields under wind pressure. In this way the effective surface of the rotor blade and consequently the attack surface for the wind becomes smaller. At the same time the load on the following components including the tower falls.

In a particularly preferred embodiment, the rotor blade has a second supporting structure movable in itself and / or within itself.

ES 2 397 263 T3

In this case, the deformable material can be fixed at predetermined points of this second supporting structure. Furthermore, the deformable material can be fixed with one side on a rotating spool core.

During normal operation of the wind power installation, the second supporting structure can now be deployed, ie the folding arms can be fully extended or the telescopic arms can be fully deployed. The deformable material can be fixed with one side on a rotating spool core. If the surface area of ​​the rotor blade is to be reduced, the reel core is rotated, analogous to an awning, so that it rolls up the deformable material. At the same time, the folding arms are folded and reduce the second supporting structure in the area of ​​the reducible surface so that the surface area of ​​the rotor blade is correspondingly reduced.

In an alternative embodiment, a part of the surface of the rotor blade is made up of slat-like strips which are respectively arranged on a supporting rail that can be pivoted around the proper longitudinal axis. In this case these blades are directed during normal operation in such a way as to increase the aerodynamically effective surface area of ​​the rotor blade. For transport and / or in the event of extreme loads, the carrier rails can be pivoted so that these slats reach, for example, downwind of the remaining rotor blade and thus the rotor blade surface area is reduced.

In a particularly preferred variant, a movable part of the aerodynamically effective surface of the rotor blade consists of a single surface element that can be displaced in the direction of the depth of the rotor blade. During normal operation this surface element extends the surface of the rotor blade, preferably on the suction side, to create a large aerodynamically effective surface.

To reduce the surface area, this surface element can be displaced, comparable to the flap system of an aircraft bearing surface, so that it moves inside the rotor blade and is therefore covered by the remaining surface of the blade. rotor, or travels over the surface of the rotor blade and coats the surface of the rotor blade by its side. In each case there is thus a decrease in the surface area of ​​the rotor blade.

In an alternative embodiment this surface element can be pivotally hinged to one side on the first supporting structure or the rear edge of the rotor blade. To change the size of the rotor blade surface, this element can be pivoted around this pivot axis towards the suction side or towards the pressure side of the rotor blade.

A pivoting of this surface element by approximately 90 ° causes in this case that this element is essentially perpendicular to the direction of the air flow in the rotor blade and a corresponding braking effect develops since an obstacle is formed for the rotor blade. air flowing along the surface of the rotor blade.

Various embodiments according to the invention are explained in more detail below by means of the accompanying drawings. In this case they show:

Figure 1 a plan view of a complete rotor blade according to the invention;

Figure 2 a plan view of the front part of a rotor blade according to the invention;

Figure 3 a simplified cross-sectional representation of an embodiment of a rotor blade according to the invention;

Figure 4 a simplified cross-sectional representation of a second embodiment of a rotor blade;

Figure 5a, 5b a simplified cross-sectional representation of a third embodiment of a rotor blade;

Figure 6 a simplified cross-sectional representation of a fourth embodiment of a rotor blade;

Figure 7 a simplified cross-sectional representation of a fifth embodiment of a rotor blade;

Figure 8a, 8b a simplified cross-sectional representation of a sixth embodiment of a rotor blade;

Figure 9 plan view of a construction variant of a rotor blade.

Figure 1 shows a simplified plan view of a complete rotor blade according to the invention. The rotor blade 10 is divided into two zones. In this case the rotor blade 10 is constructed in a conventional way in essential parts. However, in an area adjacent to the base 12 of the rotor blade, ie the area with the greatest blade depth, a division of the rotor blade can be recognized. This division marks the area of ​​the rotor blade 14

ES 2 397 263 T3 whose surface can be reduced if necessary and consequently the effect of the wind can be avoided.

Figure 2 shows the fixed part of the rotor blade 10 whose surface remains unchanged. As can be clearly recognized in this figure, the aerodynamically effective surface of the rotor blade 10 is clearly reduced, and thus, in particular in extreme wind situations, also the load is clearly less than in a rotor blade constructed of conventional way.

Figure 3 shows a simplified cross-sectional representation of an embodiment according to the invention. In this case the rotor blade 10 is divided into a front area 11 and a rear box 14. This rear box 14 is made of two ways of deformable material 18 that form a closed container 16 together with the rear wall of the front area 11. . If now this closed container 16 is filled under pressure with a gaseous medium, the deformable material 18 forms part (identified in Figure 1 with reference 14) of the aerodynamically effective surface during normal operation of the rotor blade 10 according to the invention .

A suitable choice of the filling pressure produces such a stability of this part of the rotor blade 10 that it develops its normal action in the case of normal wind conditions. However, in an extreme wind situation the wind pressure on this part of the rotor blade 10 is higher so that then the external pressure is higher than the internal pressure, and consequently a deformation of the rotor blade occurs. in the area of ​​the back box 14 and the rotor blade yields to the pressure of the outside wind. In this way the attack surface becomes smaller for this extreme wind and consequently the loads on the subsequent construction become less. Complementarily, it is stated that this part of the rear box (in which the filling medium is housed) can be actively emptied when exceeding a predetermined wind speed in order to reduce the surface of the rotor blade. This active emptying has the advantage that the shape of the rotor blade is defined at all times, while unsafe situations could arise in the event of a backbox sag due to external pressure.

To prevent damage in particular to the container 16, for example, an overpressure valve (not shown) can be provided by means of which an overpressure which builds up in the container 16 can be reduced.

By using a compressor 17 the pressure necessary for normal operation can be generated again. If, in addition, controllable pressure sensors and / or valves (also not shown) are provided, the filling pressure in the container 16 can also be monitored in the event of variations in wind pressure in order to always maintain optimal operating conditions. .

Figure 4 shows a second embodiment in which instead of a complete back box 14 the surface of the suction side of the rotor blade 10 is extended. This extension is a surface element 24 that connects to the surface of the frontal zone 11.

To reduce the aerodynamically effective surface area, this surface element 24 can be displaced in the direction of the arrow. This displacement can be carried out, for example, hydraulically, that is to say with corresponding hydraulic cylinders, pneumatically, with pneumatic cylinders, by electric drive or in another appropriate way. Corresponding pumps, compressors or drives (actuators) must of course be provided for this (however, not shown for reasons of visibility in the figure).

In this case, this displacement can be carried out within the front zone so that the surface of the front zone 11 covers the surface element 24. Alternatively, the displacement can also be carried out on the surface of the front zone 11 so that the element surface 24 covers on its side the corresponding part of the surface of the front zone 11. In both cases there is a reduction in the aerodynamically effective surface of the rotor blade 10.

A third embodiment is shown in Figures 5a and 5b. Figure 5a shows a spool 20 of a deformable material and reference 30 designates folding arms that are in the folded state. The mechanics can be compared here with that of an awning.

This embodiment is shown in figure 5b in the normal operating state. The folding arms 30 are extended and since the deformable material 18 is attached here it unwinds as the folding arms 30 of the spool 20 are deployed so that the spool core 21 no longer carries the entire spool of material.

In this unwound situation the deformable material 18 is fixed on the one hand on the reel core 21 and on the other hand on the ends of the folding arms 30 which point to the right in the figure. These ends of the folding arms 30 can be joined again by means of a rib (not shown) in order to achieve greater rigidity of the construction on the other hand and, on the other hand, to fix the deformable material.

To prevent a transfer of the deformable material 18 between the reel core 21 and the outer ends of the folding arms 30, a device of the non-extensible grid type can be provided below the deformable material 18.

ES 2 397 263 T3 shown which is actuated synchronously with the folding arms 30 and supports the deformable material 18 in the deployed state.

An effective area reduction develops inversely; the deployable arms 30 and the extensible grid (not shown) are retracted (folded) and at the same time the deformable material 18 is wound on the reel core 21, so that finally the reel 20 shown in figure 5a is produced again and the effective area of ​​the rotor blade 10 is reduced.

In a fourth embodiment shown in FIG. 6, the surface element 24 is pivotally articulated on the rear side of the front area 11 and consequently extends the suction side of this front area 11. In this case, the surface element 24 is supported by a pressure spring 28 which is arranged between the surface element 24 and the supporting structure of the front area 11.

During normal operation this pressure spring 28 supports the surface element 24 so that it maintains the desired position. If a wind pressure now occurs on the upper side of the rotor blade 10 beyond normal operating conditions, the pressure on the surface of the surface element 24 increases and overcomes the force of the spring 28 so that the element Surface 24 is pressed downward in FIG. 6, then yields to wind pressure and consequently reduces the aerodynamically effective surface area accordingly.

As an alternative to the spring 28, corresponding telescopic elements such as hydraulic or pneumatic devices or mechanical devices for active adjustment of the surface element can of course be formed, for example, threaded rods and worm-adjusting mechanisms among others can be used to hold the clamping element. surface 24 in a first predetermined position or move it to a second predetermined position. For the actuation of the adjusting member, corresponding pumps, compressors or drives must of course be provided which are not represented in this figure again for the improvement of visibility.

Likewise, the wind load acting on the surface element 24 can be detected again and depending on this detected wind load, the surface element 24 can be pivoted around the pivot axis to make an optimal adjustment of the operating conditions. momentary.

Figure 7 shows a fifth embodiment. In this fifth embodiment the surface element 24 is arranged instead of a pivotable joint on the rear side of the front zone 11 about a pivot axis 22 rotatable about its own longitudinal axis. In the position shown in FIG. 7 the surface element 24 again extends the aerodynamically effective surface of the rotor blade 10.

To decrease this surface, the pivot axis 22 is now rotated with the surface element 24 fixed thereon about its longitudinal axis, so that the outer end of the surface element 24 moves in one of the two directions shown by the double arrow. This again leads to a decrease in the aerodynamically effective surface area of ​​the rotor blade 10 and consequently accompanying a change in the wind load on the rotor blade 10 and all subsequent components of the wind power plant.

A variant of the embodiment shown in figure 7 is represented in figures 8a and 8b. In this case the surface element drawn in figure 7 with 24 is divided into three slat-like elements 26 in figure 8a. These are deliberately depicted in figure 8a at a distance to clarify this division. In a real embodiment, these three elements are naturally arranged in such a way as to form a surface that is, if possible, closed, which again is adjacent, if possible, evenly, to the front zone 11 of the rotor blade 10.

Each of the slats 26 is arranged on its own pivot axis. Each of these pivot axes 28 can be rotated about its own longitudinal axis and thus allows, by rotating the pivot axis 28 about the longitudinal axis, a pivoting of the slats 26.

Figure 8b shows the device in the situation in which these blades are pivoted so as to decrease the aerodynamically effective surface of the rotor blade 10. In this case the blades 26 are pivoted downwind of the front zone 11. So that on the one hand they no longer act as a surface of the rotor blade, but on the other hand they are also withdrawn from the attack of the wind and therefore not exposed to high loads.

Such an arrangement is achieved insofar as, together with a rotation of the pivot axes 28 around their longitudinal axes, the distance between the left pivot axis 28 in the figure and the front zone 11 of the rotor blade 10 is further decreased by one side and between the pivot axes 28 with respect to each other on the other side.

As long as only one extension of the suction side of the surface is shown in the figures, the surface of the pressure side can of course be altered accordingly alternatively or additionally.

If a wind power installation is equipped with the rotor blades previously described then it is possible that at

ES 2 397 263 T3 an extreme wind situation not only determines the great intensity of the wind, which can be done by means of wind speed measurement devices, but also clearly reduces the size of the blade surface rotor by means of a corresponding control. As can be seen in Figures 1 and 2, for example, the surface of the rotor blade according to Figure 1 is more than 10% larger than the surface of the rotor blade according to Figure 2. While the normal size of the rotor blade conforms to the nominal operation of the wind power installation, that is, at a wind speed in the range of 2-20 m / s wind speed, the size of the surface it decreases in the case of a wind speed above 20 m / s, so that the size of the surface clearly decreases, as represented in figure 2.

The control is preferably computer-assisted and if necessary provides the respectively optimally adjusted surface size of the rotor blade.

Figure 14 shows another construction variant of a rotor blade according to the invention. In this case the structure is built by pivotable supports 32 that can be tensioned with a again deformable sheet and are pivotably mounted at bearing points 34. By moving in the direction of the rotor blade tip (arrow) these pivot supports can now be pivoted, for example, around the bearing points 34 and consequently the profile of the rear case can be modified.

The other figures 9a to 14b show other alternative or complementary embodiments to the previous figures 3 to 8b.

In FIG. 11b (FIG. 11a corresponds essentially to FIG. 6) an element 25 is represented on the pressure side as a complement to FIG. 6. Since the point of attack for the spring 28 has not been modified with respect to the representation in figure 6 or 11a, the elements 24 and 25 are related to the rear edge of the blade so that they can pivot around a point of articulation 26 . Eventually in this solution it is offered to configure an overlap of the rotor blade housing 11 on the element 25 along the length of the rotor blade.

In FIG. 12b (an extension of what is represented in FIG. 7 or FIG. 12a) an element 25 is also represented on the pressure side, which in the case shown is fixed through a mechanical connection even like element 24 in the case. suction side on a common 12 shaft.

Figures 13a and 13b show a variant that is already represented in Figures 8a and 8b. In this case, for corresponding elements on the pressure side, some of their own shafts 28 are shown. FIG. 13a shows analogously to FIG. 8a a rotor blade in normal operation, FIG. 13b shows a situation in which the back box is not operational by corresponding rotation or by displacement of the shafts 28.