Title of Invention	ROTOR BLADE FOR A WIND POWER PLANT
Abstract	Disclosed is a rotor blade for a wind power station, comprising a profiled member that is provided with a relative thickness which decreases towards the outside from a root to a tip of the blade. Said profiled member has a leading edge and a trailing edge as well as a suction side and a pressure side while generating a negative pressure relative to the pressure side on the suction side when being flown against by moved air, said negative pressure resulting in buoyancy. The suction side of the rotor blade encompasses a device for optimizing the flow around the profiled member. The inventive rotor blade is characterized by the fact that said device is provided with at least one planar element that extends substantially in the direction of flow, protrudes from the suction side, and is arranged in the zone of a transversal flow which runs from the root to the tip of the blade on the suction side of the profiled member. The height and length of the planar element are selected such that the element causes said transversal flow to be effectively reduced.

Title of Invention

ROTOR BLADE FOR A WIND POWER PLANT

Abstract

Disclosed is a rotor blade for a wind power station, comprising a profiled member that is provided with a relative thickness which decreases towards the outside from a root to a tip of the blade. Said profiled member has a leading edge and a trailing edge as well as a suction side and a pressure side while generating a negative pressure relative to the pressure side on the suction side when being flown against by moved air, said negative pressure resulting in buoyancy. The suction side of the rotor blade encompasses a device for optimizing the flow around the profiled member. The inventive rotor blade is characterized by the fact that said device is provided with at least one planar element that extends substantially in the direction of flow, protrudes from the suction side, and is arranged in the zone of a transversal flow which runs from the root to the tip of the blade on the suction side of the profiled member. The height and length of the planar element are selected such that the element causes said transversal flow to be effectively reduced.

Full Text	Rotor Blade for a Wind Power Plant The invention relates to a rotor blade for a wind power plant with a mechanism for optimising the circulation according to the introductory part of claim 1. Wind power plants have a rotor with one or more rotor blades. Each of the rotor blades has a profile having a relative thickness that largely reduces from the blade root outwards to the blade peak. The profile is shaped in such a way that a suction side and a compression side gets formed, so that during circulation with moved air an underpressure occurs on the suction side as compared to the compression side. The pressure difference between compression side and suction side leads to uplift that causes rotation of the rotor, which is again used for driving a generator generating electrical current. Three-requirement for a high degree of effectiveness of the rotor and hence a high yield of the wind power plant is an almost undisturbed circulation of the profile vertical to the axis of the rotor blade over the entire range of the rotor blades. It can however be observed in know in rotor blades that the air flow acting on the suction side breaks away creating a dead water zone that reduces the uplift of the rotor blade and retards the rotor blade by increasing its resistance. Dead water zone generally refers to the zone of separated flow. Both factors reduce the yield of the wind power plant. Generally the stalling of the flow takes place, seen in the direction of flow, beyond the greatest relative thickness of the profile. Usually at least the regions close to the blade root are affected by it. A known agent to reduce the flow-stalling and thus to optimise the circulation are vortex generators. These generally consist of plates, rods or profiles connected on the suction side of the rotor blade and generate locally limited turbulences that reduce a large-surface-stalling of the circulation. Such vortex generators are known, e.g. from WO 001 5061. The disadvantage of the known vortex generators is that they only slightly 2 improve the yield of the wind power plant, because they themselves generate resistance and additionally also loud noises. It is the task of this invention to create a rotor blade for wind power plants that would exhibit clearly improved circulation properties as compared to the state-of-the-art technology. This task is fulfilled by means of the distinctive features mentioned in claim 1. The solution of this task is described in details below is based on the knowledge that, especially in the region of the rotor root on the suction side of the profile, disturbing currents are generated that run in transverse direction of the rotor blade to the blade peak. These cross-currents that occur mainly in the region of the separated flow are due to the pressure difference occurring in different blade radii on account of the different flow velocities, and are induced particularly strongly in the region of the blade root. Apart from these factors, also the centrifugal forces acting on the rotor blade contribute to formation of these cross-currents. Due to the cross-current the separation from the circulation present in the region of the blade root of the rotor blade of the acrodynamically unfavourable profile present here gets carried in the direction of the blade peak. i.e. into the region of the aerodynamically effective profile. Besides, the cross-current also disturbs the effective flow acting on the rotor blade by generating turbulences that lead to a premature stalling of these currents. Therefore, according to the invention, a rotor blade for a wind power plant is provided with a mechanism for optimising the circulation profile that has at least one flat element largely aligned in flow direction and standing away from the suction side, which is arranged in the region of the mentioned cross-current flowing outwards from the blade root on the suction side of the profile, whereby the height and length of the mechanism is selected in such a way that the mechanism effects an effective reduction of these crosscurrents. 3 Through reduction of the cross-current by this flat element a premature flow-stalling on the suction side of the rotor blade is prevented. Such an improved circulation leads to a significant increase in the yield of a correspondingly equipped wind power plant without any danger in increase of operational noise. The required height and length of the respective flat element and its optimum position on the suction side of the rotor blade naturally varies with the distance to the rotation axis of the rotor, the profile thickness, the width of the rotor, the mainly expected flow velocity etc. The optimum configuration can be determined empirically in the simplest possible way, e.g. by attaching on the rotor blade in different radius positions series of woollen threads with one of their ends fixed to the blade, and in open air experiments on the basis of the alignment of the free ends of the woollen threads that makes the prevailing How conditions visible. In this way, one can relatively easily test the effect of the elements according to the invention on the flow conditions in different radius positions and thus determine the optimum number and position and, if required, even the dimensioning of the Hat elements according to the invention. For determining the required height of the fiat elements, the woollen threads can, if required, be additionally attached to distance holders of different lengths, in the form of bars, in order to define the height of the dead water /one caused by the cross-currents and hence the height of the cross-current to be maintained. By proceeding in this manner, one can empirically determine the optimum height and length of the fiat elements and/or their optimum positions on a given rotor blade as envisaged by the invention. In a corresponding series of tests, one can thus find the optimum dimensions and positions of the fiat element as per the invention for any type of rotor blade. 4 From the aircraft building industry we know since a long time about flat elements attached to the suction side of a lifting surface that prevent a cross-current. These elements are especially used in aircrafts whose lifting surfaces have a swept-back arrangement. Here one has the problem that, on account of the inclined arrangement of the lifting surface in the front edge, a pressure gradient occurs that deflects the air circulating the lifting surface in the direction of the lifting surface peak. This not-separated cross-current again disturbs the circulation of the lifting surface and hence reduces the uplift, as the flow along the wing however no longer flows over it. In order to reduce the cross-current, one therefore uses vertically arranged barriers on such lifting surfaces that are referred to as boundary layer fences. These boundary layer fences differ in significant features from the elements for rotor blades of wind power plants presented here according to the invention. As the not-separated cross-currents on swept-back lifting surfaces are mainly induced in the region of the lifting surface front edge, the limiting boundary fences are arranged precisely in this region. They often stretch even around the lifting surface front edge up to the compression side of the lifting surface. The flat elements of rotor blades of wind power plants as per the invention, on the other hand, reduce an already separated cross-current caused due to other phenomena mainly in the region of the greatest profile thickness of the rotor blade, and induce a current-stalling in the region of the profile thickness away from the current. An arrangement only in the region of the front edge of the rotor blade does not make any sense in these elements. In a preferred extension of the invention it is foreseen, that the flat element is arranged at least in the region of a cross-current flowing on the suction side of the profile between a region of a greatest relative thickness of the profile and the rear edge of the profile. This cross-current is a kind of current already described above, that is obtained from the difference of the initial flow velocities between regions near the blade root and regions near the blade peak, and the pressure gradients resulting from it on the suction side of the rotor blade, as well as due to the centrifugal forces prevailing on the rotor blade. 5 In a particularly preferred extension of the invention, the flat element stretches over the entire width of the suction side of the rotor profile. In this way it is ensured that an overlapping of the cross-current on areas with healthy flow can be prevented, even without considering the exact flow of the cross-current on the suction side of the rotor blade. In another preferred extension of the invention, the flat element is designed in such a way, that its stretches in its longitudinal extension in a straight direction. In this way, the resistance forces coming into play due to the flat element can be kept low and the noise generation can be minimized. In a particularly preferred extension, the alignment of the flat element takes place in such a way, that it does not deviate more than 10° from the path of the tangent to the circle with a radius of the rotor blade corresponding to the position of the rotor blade. In yet another preferred extension, the flat element is designed in such a way, that its stretches in the direction of its longitudinal extension following the rotation path of the radius that conforms to the distance of the front end of the flat element from the rotation axis of the rotor. This extension depicts a further possibility of keeping the resistance forces occurring on account of the flat element low. and minimi/ing the noise generation. In yet another preferred extension of the invention it is foreseen, that the rotor blade has several flat elements on the suction side of its profile. This is meaningful in cases where behind a first element as per the invention a relevant cross-current is generated afresh. The optimum positioning and dimensioning of these several flat elements on the rotor blade can be undertaken as described above. In another preferred extension of the invention it is foreseen, that the flat elements on the suction side of the rotor blades are arranged in the region that stretches from the blade root up to half the length of the rotor blade. Particularly preferred here is a region that stretches from the blade root up to one-third of the length of the rotor blade. 6 In a particularly preferred extension it is foreseen, that at least one flat element is arranged in a region that lies - seen from the blade root - beyond a transition region in which the profile of the blade root passes over into a profile generating an uplift. An element arranged in such a manner is suitable for interrupting an already existing crosscurrent carried over in the region of the blade root and thus avoiding a disturbance of the laminar flows acting in this region. In yet another preferred extension it is foreseen, that at least one flat element is arranged in a region that lies within a transition region as seen from the blade root, in which the profile of the blade root goes over into a profile generating an uplift. On account of the special conditions in rotor blades the significant portion of disturbing cross-current occurs in this region near the blade root, as the rotor blade generally does not have a flow-favourable profile here on account of the large profile thickness. Provision of an element as per the invention in this region therefore very effectively prevents generation of the cross-current - in contrast to the elements already described above, that are arranged in such a way that they prevent a propagation of an already existing crosscurrent in the power-yielding region of the rotor blade. In another preferred extension of the invention it is foreseen, that the flat clement is designed at least section-wise as air-permeable, e.g. in the form of a grid screen or with holes arranged in the element. A flat element with such a design with suitable dimensioning can sometimes reduce occurring cross-currents better than a non-interrupting element. Besides, with the help of such a design, the weight of the flat elements can be reduced. In a further preferred design of the invention it is foreseen, that the flat element is made of metal, e.g. precious steel or aluminium, of plastic, of compound materials like GFK. or (TK, or a combination of these materials. Such a structure ensures that the element can withstand weather conditions as well as the mechanical load under its usage conditions. Of course other materials which are equivalent can be used, that meet the requirements of weather resistance and stability. 7 The invention not only relates to rotor blades but also to flat elements that can be attached on a profile rotor blade of a wind power plant, aligned mainly in flow direction and standing away from the suction side; their height and length arc selected in such a way that they bring about an effective reduction of a cross-current flowing outwards from the blade root. Such elements can be used for post-equipping already erected wind power plants. In a preferred extension it is foreseen, that a flat element is designed in the position of its attachment tightly connected to the contour run of the rotor profile. However, the element can also be clastically or plastically shaped, so that it can be adapted in the position of its attachment to the contour run of the rotor profile only at the time of assembly. The invention is shown in the drawings, schematically and as example in a preferred design form. The following are shown: Fig. I Top view on the suction side of a rotor blade of a wind power plant as per the invention; Fig.2a a section along the line A-A in fig. 1: and Fig.2b a further section along the line A-A in fig. 1 in another design extension. Fig. 1 shows rotor blade 10 with a front edge 11. a rear edge 12, a blade root 13, a blade peak 14. a suction side 15 and a compression side 16. The rotor blade has in the course of its run a relative thickness that reduces from the blade root 13 outwards to the blade peak 14. The front edge 11 points in the rotation direction of the rotor blade. On the suction side 15 flat elements 17 and 18 are attached, arranged in flow direction, which eliminate a cross-current on the suction side 15 and thus prevent a premature a flow-stalling. A transition region 19 has the special feature, that here the cylindrical profile of the blade root 1 3 passes over into a globule-shaped profile that generates uplift. The cross-current is indicated by an arrow. 8 Fig. 2a shows a section through the rotor blade along the line A-A in fig. I with a front edge 21, a rear edge 22. a suction side 25 and a compression side 26. On the suction side 25 the flat element 28 is arranged, which stretches from the front edge 21 up to the rear edge 22 and hence over the entire width of the blade and eliminates a cross-current on the suction side 25. Fig. 2b shows a further section through the rotor along the line A-A in fig. 1 in another design extension with a front edge 21, a rear edge 22, a suction side 25 and a compression side 26. On the suction side 25 the flat element 28 is arranged, which stretches from the front edge 21 up to the rear edge 22 and has chamfered edges. The flat element 28 has holes 29, which if properly dimensioned, contribute towards effective prevention of a cross-current on the suction side 25. 9 Patent Claims 1. Rotor blade for a wind power plant with a profile that has in its run a relative thickness that largely reduces from a blade root outwards to a blade peak, in which a profile has a front edge and a rear edge as well as a suction side and a compression side and in case of the initial flow with moved air on the suction side generates an under-pressure with respect to the compression side, which leads to an uplift, and in which the rotor blade has a mechanism on the suction side for optimising the circulation of the profile, having the distinctive feature that the mechanism has a fiat element (17. 18) aligned mainly in flow direction and standing away from the suction side (15): this element is arranged in the region of a cross-current flowing on the suction side (15) of the profile from the blade root (13) to the blade peak (14). where the height and length of the fiat element (17, 18) are selected in such a way, that the element (17, 18) brings about an effective reduction in this cross-current. 2. Rotor blade as per claim 1, having the distinctive feature that the fiat element is arranged at least in a region of a cross-current flowing on the suction side of the profile between a region having the maximum relative thickness of the profile and the rear edge of the profile. 3. Rotor blade as per one of the previous claims, having the distinctive feature that the length of the fiat element stretches over the entire width of the suction side of the rotor profile. 4. The rotor blade as per one of the previous claims, having the distinctive feature that the fiat element is designed straight in its longitudinal extension. 10 5. Rotor blade as per claim 4. having the distinctive feature that the alignment of the flat element does not deviate by more than 10c from the path of the tangent of the circle with the radius of the rotor blade corresponding the position of the element. 6. Rotor blade as per one of the claims 1 - 3, having the distinctive feature that the flat element is designed in such a way. that it stretches in the direction of its longitudinal extension following the rotation path of the radius that conforms to the distance of the front end of the Hat element to the rotation axis of the rotor. 7. Rotor blade as per one of the previous claims, having the distinctive feature that the rotor blade has several flat elements on the suction side of its profile. 8. Rotor blade as per claim 7. having the distinctive feature that the flat elements on the suction side of the rotor blade are arranged in a region that stretches from the blade root up to half the length of the rotor blade. 9. Rotor blade as per claim 7. having the distinctive feature that the flat elements on the suction side of the rotor blade are arranged in a region that stretches from the blade root up to one-third of the length of the rotor blade. 10. Rotor blade as per claim 8 or 9. having the distinctive feature that at least one flat element is arranged in a region that, seen from the blade root, lies beyond a transition /.one in which the profile of the blade root passes over into a profile generating an uplift. 11 11. Rotor blade as per one of the claims 8 - 10, having the distinctive feature that at least one tlat element is arranged in a region that, seen from the blade root, lies within the side of a transition zone in which the profile of the blade root goes over into a profile generating an uplift. 12. Rotor blade as per one of the previous claims, having the distinctive feature that the flat element is at least section-wise designed to be air-permeable, e.g. in the form of a grid screen or with holes. I 3. Rotor blade as per one of the previous claims, having the distinctive feature that the flat element is made of metal, e.g. precious steel or aluminium, of plastic, of compound materials like GFK or CFK, or a combination of these materials. 14. Flat element according to one of the previous claims, having the distinctive feature that the Hat element can be arranged aligned on a profiled rotor blade of a wind power plant largely in How direction and standing away from the suction side: its height and length can be selected in such a way, that the flat element brings about an effective reduction in a cross-current flowing from the blade root outwards. 15. Flat element as per claim 14. having the distinctive feature that the side of the flat element towards the rotor blade is adapted to the contour run of the rotor profile at the position of its attachment. 16. Flat element as per claim 14. having the distinctive feature that the flat element can be shaped elastically or plastically and adapted at the position of its attachment to the contour run of the rotor profile.

Full Text

Rotor Blade for a Wind Power Plant
The invention relates to a rotor blade for a wind power plant with a mechanism for optimising the circulation according to the introductory part of claim 1.
Wind power plants have a rotor with one or more rotor blades. Each of the rotor blades has a profile having a relative thickness that largely reduces from the blade root outwards to the blade peak. The profile is shaped in such a way that a suction side and a compression side gets formed, so that during circulation with moved air an underpressure occurs on the suction side as compared to the compression side. The pressure difference between compression side and suction side leads to uplift that causes rotation of the rotor, which is again used for driving a generator generating electrical current.
Three-requirement for a high degree of effectiveness of the rotor and hence a high yield of the wind power plant is an almost undisturbed circulation of the profile vertical to the axis of the rotor blade over the entire range of the rotor blades. It can however be observed in know in rotor blades that the air flow acting on the suction side breaks away creating a dead water zone that reduces the uplift of the rotor blade and retards the rotor blade by increasing its resistance. Dead water zone generally refers to the zone of separated flow. Both factors reduce the yield of the wind power plant.
Generally the stalling of the flow takes place, seen in the direction of flow, beyond the greatest relative thickness of the profile. Usually at least the regions close to the blade root are affected by it.
A known agent to reduce the flow-stalling and thus to optimise the circulation are vortex generators. These generally consist of plates, rods or profiles connected on the suction side of the rotor blade and generate locally limited turbulences that reduce a large-surface-stalling of the circulation. Such vortex generators are known, e.g. from WO 001 5061. The disadvantage of the known vortex generators is that they only slightly

2
improve the yield of the wind power plant, because they themselves generate resistance and additionally also loud noises.
It is the task of this invention to create a rotor blade for wind power plants that would exhibit clearly improved circulation properties as compared to the state-of-the-art technology. This task is fulfilled by means of the distinctive features mentioned in claim 1.
The solution of this task is described in details below is based on the knowledge that, especially in the region of the rotor root on the suction side of the profile, disturbing currents are generated that run in transverse direction of the rotor blade to the blade peak. These cross-currents that occur mainly in the region of the separated flow are due to the pressure difference occurring in different blade radii on account of the different flow velocities, and are induced particularly strongly in the region of the blade root. Apart from these factors, also the centrifugal forces acting on the rotor blade contribute to formation of these cross-currents.
Due to the cross-current the separation from the circulation present in the region of the blade root of the rotor blade of the acrodynamically unfavourable profile present here gets carried in the direction of the blade peak. i.e. into the region of the aerodynamically effective profile. Besides, the cross-current also disturbs the effective flow acting on the rotor blade by generating turbulences that lead to a premature stalling of these currents.
Therefore, according to the invention, a rotor blade for a wind power plant is provided with a mechanism for optimising the circulation profile that has at least one flat element largely aligned in flow direction and standing away from the suction side, which is arranged in the region of the mentioned cross-current flowing outwards from the blade root on the suction side of the profile, whereby the height and length of the mechanism is selected in such a way that the mechanism effects an effective reduction of these crosscurrents.

3
Through reduction of the cross-current by this flat element a premature flow-stalling on the suction side of the rotor blade is prevented. Such an improved circulation leads to a significant increase in the yield of a correspondingly equipped wind power plant without any danger in increase of operational noise.
The required height and length of the respective flat element and its optimum position on the suction side of the rotor blade naturally varies with the distance to the rotation axis of the rotor, the profile thickness, the width of the rotor, the mainly expected flow velocity etc.
The optimum configuration can be determined empirically in the simplest possible way, e.g. by attaching on the rotor blade in different radius positions series of woollen threads with one of their ends fixed to the blade, and in open air experiments on the basis of the alignment of the free ends of the woollen threads that makes the prevailing How conditions visible. In this way, one can relatively easily test the effect of the elements according to the invention on the flow conditions in different radius positions and thus determine the optimum number and position and, if required, even the dimensioning of the Hat elements according to the invention.
For determining the required height of the fiat elements, the woollen threads can, if required, be additionally attached to distance holders of different lengths, in the form of bars, in order to define the height of the dead water /one caused by the cross-currents and hence the height of the cross-current to be maintained.
By proceeding in this manner, one can empirically determine the optimum height and length of the fiat elements and/or their optimum positions on a given rotor blade as envisaged by the invention. In a corresponding series of tests, one can thus find the optimum dimensions and positions of the fiat element as per the invention for any type of rotor blade.

4
From the aircraft building industry we know since a long time about flat elements attached to the suction side of a lifting surface that prevent a cross-current. These elements are especially used in aircrafts whose lifting surfaces have a swept-back arrangement. Here one has the problem that, on account of the inclined arrangement of the lifting surface in the front edge, a pressure gradient occurs that deflects the air circulating the lifting surface in the direction of the lifting surface peak. This not-separated cross-current again disturbs the circulation of the lifting surface and hence reduces the uplift, as the flow along the wing however no longer flows over it. In order to reduce the cross-current, one therefore uses vertically arranged barriers on such lifting surfaces that are referred to as boundary layer fences.
These boundary layer fences differ in significant features from the elements for rotor blades of wind power plants presented here according to the invention. As the not-separated cross-currents on swept-back lifting surfaces are mainly induced in the region of the lifting surface front edge, the limiting boundary fences are arranged precisely in this region. They often stretch even around the lifting surface front edge up to the compression side of the lifting surface.
The flat elements of rotor blades of wind power plants as per the invention, on the other hand, reduce an already separated cross-current caused due to other phenomena mainly in the region of the greatest profile thickness of the rotor blade, and induce a current-stalling in the region of the profile thickness away from the current. An arrangement only in the region of the front edge of the rotor blade does not make any sense in these elements.
In a preferred extension of the invention it is foreseen, that the flat element is arranged at least in the region of a cross-current flowing on the suction side of the profile between a region of a greatest relative thickness of the profile and the rear edge of the profile. This cross-current is a kind of current already described above, that is obtained from the difference of the initial flow velocities between regions near the blade root and regions near the blade peak, and the pressure gradients resulting from it on the suction side of the rotor blade, as well as due to the centrifugal forces prevailing on the rotor blade.

5
In a particularly preferred extension of the invention, the flat element stretches over the entire width of the suction side of the rotor profile. In this way it is ensured that an overlapping of the cross-current on areas with healthy flow can be prevented, even without considering the exact flow of the cross-current on the suction side of the rotor blade.
In another preferred extension of the invention, the flat element is designed in such a way, that its stretches in its longitudinal extension in a straight direction. In this way, the resistance forces coming into play due to the flat element can be kept low and the noise generation can be minimized. In a particularly preferred extension, the alignment of the flat element takes place in such a way, that it does not deviate more than 10° from the path of the tangent to the circle with a radius of the rotor blade corresponding to the position of the rotor blade.
In yet another preferred extension, the flat element is designed in such a way, that its stretches in the direction of its longitudinal extension following the rotation path of the radius that conforms to the distance of the front end of the flat element from the rotation axis of the rotor. This extension depicts a further possibility of keeping the resistance forces occurring on account of the flat element low. and minimi/ing the noise generation.
In yet another preferred extension of the invention it is foreseen, that the rotor blade has several flat elements on the suction side of its profile. This is meaningful in cases where behind a first element as per the invention a relevant cross-current is generated afresh. The optimum positioning and dimensioning of these several flat elements on the rotor blade can be undertaken as described above.
In another preferred extension of the invention it is foreseen, that the flat elements on the suction side of the rotor blades are arranged in the region that stretches from the blade root up to half the length of the rotor blade. Particularly preferred here is a region that stretches from the blade root up to one-third of the length of the rotor blade.

6
In a particularly preferred extension it is foreseen, that at least one flat element is arranged in a region that lies - seen from the blade root - beyond a transition region in which the profile of the blade root passes over into a profile generating an uplift. An element arranged in such a manner is suitable for interrupting an already existing crosscurrent carried over in the region of the blade root and thus avoiding a disturbance of the laminar flows acting in this region.
In yet another preferred extension it is foreseen, that at least one flat element is arranged in a region that lies within a transition region as seen from the blade root, in which the profile of the blade root goes over into a profile generating an uplift. On account of the special conditions in rotor blades the significant portion of disturbing cross-current occurs in this region near the blade root, as the rotor blade generally does not have a flow-favourable profile here on account of the large profile thickness. Provision of an element as per the invention in this region therefore very effectively prevents generation of the cross-current - in contrast to the elements already described above, that are arranged in such a way that they prevent a propagation of an already existing crosscurrent in the power-yielding region of the rotor blade.
In another preferred extension of the invention it is foreseen, that the flat clement is designed at least section-wise as air-permeable, e.g. in the form of a grid screen or with holes arranged in the element. A flat element with such a design with suitable dimensioning can sometimes reduce occurring cross-currents better than a non-interrupting element. Besides, with the help of such a design, the weight of the flat elements can be reduced.
In a further preferred design of the invention it is foreseen, that the flat element is made of metal, e.g. precious steel or aluminium, of plastic, of compound materials like GFK. or (TK, or a combination of these materials. Such a structure ensures that the element can withstand weather conditions as well as the mechanical load under its usage conditions. Of course other materials which are equivalent can be used, that meet the requirements of weather resistance and stability.

7
The invention not only relates to rotor blades but also to flat elements that can be attached on a profile rotor blade of a wind power plant, aligned mainly in flow direction and standing away from the suction side; their height and length arc selected in such a way that they bring about an effective reduction of a cross-current flowing outwards from the blade root. Such elements can be used for post-equipping already erected wind power plants.
In a preferred extension it is foreseen, that a flat element is designed in the position of its attachment tightly connected to the contour run of the rotor profile. However, the element can also be clastically or plastically shaped, so that it can be adapted in the position of its attachment to the contour run of the rotor profile only at the time of assembly.
The invention is shown in the drawings, schematically and as example in a preferred design form. The following are shown:
Fig. I Top view on the suction side of a rotor blade of a wind power plant as per the
invention;
Fig.2a a section along the line A-A in fig. 1: and Fig.2b a further section along the line A-A in fig. 1 in another design extension.
Fig. 1 shows rotor blade 10 with a front edge 11. a rear edge 12, a blade root 13, a blade peak 14. a suction side 15 and a compression side 16. The rotor blade has in the course of its run a relative thickness that reduces from the blade root 13 outwards to the blade peak 14. The front edge 11 points in the rotation direction of the rotor blade. On the suction side 15 flat elements 17 and 18 are attached, arranged in flow direction, which eliminate a cross-current on the suction side 15 and thus prevent a premature a flow-stalling. A transition region 19 has the special feature, that here the cylindrical profile of the blade root 1 3 passes over into a globule-shaped profile that generates uplift. The cross-current is indicated by an arrow.

8
Fig. 2a shows a section through the rotor blade along the line A-A in fig. I with a front edge 21, a rear edge 22. a suction side 25 and a compression side 26. On the suction side 25 the flat element 28 is arranged, which stretches from the front edge 21 up to the rear edge 22 and hence over the entire width of the blade and eliminates a cross-current on the suction side 25.
Fig. 2b shows a further section through the rotor along the line A-A in fig. 1 in another design extension with a front edge 21, a rear edge 22, a suction side 25 and a compression side 26. On the suction side 25 the flat element 28 is arranged, which stretches from the front edge 21 up to the rear edge 22 and has chamfered edges. The flat element 28 has holes 29, which if properly dimensioned, contribute towards effective prevention of a cross-current on the suction side 25.

9 Patent Claims
1. Rotor blade for a wind power plant with a profile that has in its run a relative thickness that largely reduces from a blade root outwards to a blade peak, in which a profile has a front edge and a rear edge as well as a suction side and a compression side and in case of the initial flow with moved air on the suction side generates an under-pressure with respect to the compression side, which leads to an uplift, and in which the rotor blade has a mechanism on the suction side for optimising the circulation of the profile, having the distinctive feature that
the mechanism has a fiat element (17. 18) aligned mainly in flow direction and standing away from the suction side (15): this element is arranged in the region of a cross-current flowing on the suction side (15) of the profile from the blade root (13) to the blade peak (14). where the height and length of the fiat element (17, 18) are selected in such a way, that the element (17, 18) brings about an effective reduction in this cross-current.
2. Rotor blade as per claim 1,
having the distinctive feature that
the fiat element is arranged at least in a region of a cross-current flowing on the suction side of the profile between a region having the maximum relative thickness of the profile and the rear edge of the profile.
3. Rotor blade as per one of the previous claims,
having the distinctive feature that
the length of the fiat element stretches over the entire width of the suction side of the rotor profile.
4. The rotor blade as per one of the previous claims,
having the distinctive feature that
the fiat element is designed straight in its longitudinal extension.

10
5. Rotor blade as per claim 4.
having the distinctive feature that
the alignment of the flat element does not deviate by more than 10c from the path of the tangent of the circle with the radius of the rotor blade corresponding the position of the element.
6. Rotor blade as per one of the claims 1 - 3,
having the distinctive feature that
the flat element is designed in such a way. that it stretches in the direction of its longitudinal extension following the rotation path of the radius that conforms to the distance of the front end of the Hat element to the rotation axis of the rotor.
7. Rotor blade as per one of the previous claims,
having the distinctive feature that
the rotor blade has several flat elements on the suction side of its profile.
8. Rotor blade as per claim 7.
having the distinctive feature that
the flat elements on the suction side of the rotor blade are arranged in a region that stretches from the blade root up to half the length of the rotor blade.
9. Rotor blade as per claim 7.
having the distinctive feature that
the flat elements on the suction side of the rotor blade are arranged in a region that stretches from the blade root up to one-third of the length of the rotor blade.
10. Rotor blade as per claim 8 or 9.
having the distinctive feature that
at least one flat element is arranged in a region that, seen from the blade root, lies beyond a transition /.one in which the profile of the blade root passes over into a profile generating an uplift.

11
11. Rotor blade as per one of the claims 8 - 10,
having the distinctive feature that
at least one tlat element is arranged in a region that, seen from the blade root, lies within the side of a transition zone in which the profile of the blade root goes over into a profile generating an uplift.
12. Rotor blade as per one of the previous claims,
having the distinctive feature that
the flat element is at least section-wise designed to be air-permeable, e.g. in the form of a grid screen or with holes.
I 3. Rotor blade as per one of the previous claims, having the distinctive feature that
the flat element is made of metal, e.g. precious steel or aluminium, of plastic, of compound materials like GFK or CFK, or a combination of these materials.
14. Flat element according to one of the previous claims,
having the distinctive feature that
the Hat element can be arranged aligned on a profiled rotor blade of a wind power plant largely in How direction and standing away from the suction side: its height and length can be selected in such a way, that the flat element brings about an effective reduction in a cross-current flowing from the blade root outwards.
15. Flat element as per claim 14.
having the distinctive feature that
the side of the flat element towards the rotor blade is adapted to the contour run of the rotor profile at the position of its attachment.
16. Flat element as per claim 14.
having the distinctive feature that
the flat element can be shaped elastically or plastically and adapted at the position of its attachment to the contour run of the rotor profile.

ROTOR BLADE FOR A WIND POWER PLANT

Documents:

Inventors:

PCT Conventions: