DE102017107459A1 - Rotor blade for a wind turbine and the wind turbine - Google Patents

Abstract

The rotor blade (1) according to the invention for a wind power plant has a profile nose (10), which forms the front area of the rotor blade (1) as viewed in the direction of flow (26) of the rotor blade (1) and which holds the leading edge (2) of the rotor blade (1 ), wherein the profile nose (10) in the spanwise direction (27) has an outer region (7) having a plurality of in the spanwise direction (27) of the rotor blade side by side and of the profile nose (10) protruding projections (11) each having a peak (12) which is that portion of its associated projection (11) which projects most from the profile nose (10), the heights (18) of the peaks (12) and / or the distances (12) 19) the peak (12) to the immediately adjacent peaks (12) and / or the offset (20) of the peaks (12) away from the leading edge (2) in the flow direction (26) as a function of the chord length (28) of the Rotor blade (1) at the place of jew the lift - reducing effect of the projections (11) occurs only at those angles of incidence (21) of the rotor blade (1) which are equal to or greater than the design setting angle (25) of the rotor blade (1), in which the maximum glide ratio essentially sets. The wind power plant according to the invention has a rotor which has at least the rotor blade (1).

Description

The invention relates to a rotor blade for a wind turbine and the wind turbine with a rotor having at least one rotor blade.

A wind turbine has a tower on which a nacelle is mounted. In the nacelle, a generator and a transmission are provided, via which a rotor is coupled to the generator. The rotor usually has conventionally three rotor blades, which are mounted on a hub with a horizontally arranged axis of rotation. During operation of the wind turbine, the rotor is traversed by wind, whereby kinetic energy is withdrawn from the wind by means of the rotor blades. In the design of the rotor blades in particular site-specific boundary conditions are to be considered, in particular when and how strong wind occurs and the associated vibration load of the rotor blades. It is desirable that the wind turbine optimally absorbs the available kinetic energy of the wind and has a long total service life.

The total service life is determined in particular by the fatigue strength of the rotor blades. Due to gusts of wind, the rotor blades are excited to vibrate, wherein the rotor blades are subjected to bending vibrations. The bending vibrations lead to an increase of the alternating stress of the material of the rotor blades, whereby the fatigue strength of the rotor blades is reduced.

In the conventional wind turbine, the rotor blades are mounted pivotably about their longitudinal axis on the hub, so that the angle of attack of the rotor blades can be adapted to the respective wind situation with a corresponding control device. Here, the angle of attack of the rotor blades is selected such that the aerodynamic angle of attack is in the range of the design angle. In gusts of wind, the aerodynamic angle of attack varies very rapidly and strongly, with the aerodynamic angle of attack being high during the peak velocity of a gust of wind. As a result, the lift generated by the rotor blade increases during these moments, as a result of which the rotor blade is subjected to bending stress. As the gust of wind subsides, the wind speed reduces again to its nominal level, so that again aerodynamic design conditions prevail on the rotor blade. The rhythmic occurrence of wind gusts increases the dynamic load on the rotor blades with respect to bending.

A remedy could create a variably adapted to the wind gusts employment of the rotor blades, so that even during the gusts of wind generated on the rotor blade buoyancy in the design of the wind turbine and remains relatively constant. As a result, the dynamic load of the rotor blades with respect to bending would be low. However, due to the mechanical inertia of the rotor blades and various constructional limits, it is not feasible to implement an adequate counteracting of the wind gusts by means of corresponding adjustments of the angle of attack with the control device.

The object of the invention is to provide a rotor blade for a wind turbine and the wind turbine with a rotor having at least one rotor blade, wherein the wind turbine has a long total life.

The object is solved with the features of claims 1 and 10. Preferred embodiments thereof are given in the further claims.

The rotor blade according to the invention for a wind turbine has a profile nose, which forms the front of the rotor blade seen in the direction of flow of the rotor blade and having the leading edge of the rotor blade, wherein the profile nose seen in the spanwise direction has an outer region having a plurality of in the spanwise direction of the rotor blade arranged side by side and from the profile nose protruding projections, each having a summit, which is that portion of its associated projection which protrudes most from the profile nose, wherein the heights of the peaks and / or the distances of the summits to the immediate neighboring peaks and / or the offsets of the peaks away from the front edge in the flow direction as a function of that chord length of the rotor blade at the location of the respective summit are determined, wherein the buoyancy-reducing effect of the projections only at those angles of incidence of R otor blade occurs, which are equal to or greater than the design angle of the rotor blade, wherein the maximum glide ratio is substantially adjusted. The wind turbine according to the invention has a rotor which has at least one rotor blade according to the invention.

The glide ratio corresponds to the ratio of buoyancy and air resistance of the rotor blade. If the rotor blade has the angle of attack that corresponds to the design setting angle, the buoyancy and the air resistance of the rotor blade adjust such that the glide ratio lies in the region of the maximum glide ratio. It is preferred that the distance between the design adjustment angle and the angle at which the maximum glide ratio prevails is at most +/- 5%. It is particularly preferred that the design engagement angle is at most 5% greater than the angle at which the maximum glide ratio prevails.

Wind is a flow of the atmosphere that flows at a comparatively constant, nominal speed and is superimposed with wind gusts. During wind gusts, the wind speed is variable with respect to the nominal wind speed, increasing the wind direction, thereby increasing the aerodynamic pitch of the rotor blade during gusts.

Due to the fact that the lift-reducing effect of the projections only occurs at those angles of attack of the rotor blade which are equal to or greater than the design setting angle of the rotor blade, it is achieved according to the invention that the dynamic load with respect to bending of the rotor blade is low during the gusts of wind. Therefore, the wind turbine with the rotor blades according to the invention has a long total life. If the rotor blades of the wind turbine according to the invention made of glass fiber reinforced plastic, the total service life is extended by 100% compared to a conventional wind turbine. For steel components, such as the tower of the wind turbine, the overall service life is extended by 30%.

If the projections on the tread lug were arranged such that the buoyancy-reducing effect of the projections also occurs at those pitch angles of the rotor blade that are smaller than the design pitch angle of the rotor blade, this would be accompanied by excessive deterioration of the aerodynamic efficiency of the rotor blade.

By means of the projections, during the operation of the wind turbine, during the wind gusts, vortices are generated at the profile nose, which cause a local separation at the trailing edge of the rotor blade between two immediately adjacent projections, which has a buoyancy-reducing effect. Thereby, the buoyancy coefficient of the rotor blade according to the invention is at those angles of attack of the rotor blade, which are equal to or greater than the design pitch of the rotor blade, relatively constant compared to the lift coefficient, which adjusts the angle of attack of the rotor blade, which corresponds to the design angle of attack of the rotor blade.

On wind gusts, the outer area of the rotor blade is more sensitive than the near-nook area, because the outer area has a larger lever arm relative to the hub. Furthermore, the outer area has a higher circumferential speed than the near-nook area, whereby higher aerodynamic forces act on the outer area. The fact that the projections are located in the outer region of the rotor blade according to the invention, the buoyancy-reducing effect of the projections in the outer region is particularly well deployable. Nevertheless, the projections are accompanied by a disadvantageous increase in the flow resistance, which does not need to be handled significantly by the mere provision of the projections in the outer area. It is also conceivable, however, that the projections are located over the entire span of the rotor blade.

A method according to the invention for laying out the rotor blade according to the invention comprises the steps: on the basis of the expected wind conditions at the installation site of the wind turbine, determining the design pitch angle of the rotor blade, in which the maximum glide ratio is substantially established; Providing the heights of the peaks and / or the distances of the peaks to the immediately adjacent peaks and / or the offsets of the peaks away from the leading edge in the plurality of juxtaposed and in the spanwise direction of the rotor blade side protrusions the direction of flow can be determined as a function of the chord length of the rotor blade at the location of the respective peak, wherein the buoyancy-reducing effect of the projections only occurs at those angles of attack of the rotor blade which are equal to or greater than the design pitch angle of the rotor blade; Determining the maximum possible length of the rotor blade to the effect that predetermined limits to the maximum peripheral speed of the rotor blade are not exceeded.

It is preferred that the heights of the peaks and / or the distances of the peaks to the immediately adjacent peaks and / or the offset of the peaks away from the leading edge in the flow direction are determined directly proportional to that chord length of the rotor blade at the location of the respective summit , This is based on the finding that, in the case of local profilings having a large chord length, suitably adjusted heights and / or distances and / or displacements of the summits of the protrusions are advantageous with regard to the lift-reducing effect of the protrusions. Conversely, in the case of local profilings having a small chord length, correspondingly adjusted heights and / or distances and / or offset of the summit of the projections are advantageously provided with regard to the lift-reducing effect of the projections.

It is particularly preferred that the heights of the peaks are up to 12%, in particular 0.2% to 1.5%, particularly preferably 1%, or in particular 4% to 12%, particularly preferably 5%, of that chord length of the rotor blade at the location of the rotor blade corresponding summit. Furthermore, it is particularly preferred that the distances of the peaks to the immediately adjacent peaks to 50%, in particular 2% to 10%, particularly preferably 4% to 5%, or in particular 30% to 45% of that chord length of the rotor blade at the place of respective summit correspond. Either one of the summits or the other of the peaks of the two immediately adjacent summits can be taken as reference. Moreover, it is particularly preferred that the offsets of the peaks away from the leading edge in the flow direction correspond to 0% to 3%, in particular 1% to 2%, of the chord length of the rotor blade at the location of the respective peak. These preferred embodiments are based on the finding that in this case a surprisingly good solution of the problem can be achieved, namely the advantageous buoyancy-reducing effect of the projections.

In particular, with the dimensioning of the height of the summit, that angle of incidence is set from which the buoyancy-reducing effect of the projections occurs, this angle of attack corresponding to the design setting angle. The greater the heights of the peaks in relation to the chord lengths present locally at the projections, the smaller is the angle of attack above which the buoyancy-reducing effect of the projections occurs.

The rotor blade preferably has a tip, the outer region extending from the tip to a portion of the rotor blade located at 50% to 70% of the span of the rotor blade. The tip is the longitudinal end of the rotor blade which is located furthest away from the hub-side longitudinal end of the rotor blade. These preferred embodiments are based on the finding that in this case a surprisingly good solution of the problem can be achieved, namely the sufficient buoyancy-reducing effect of the projections, wherein the loss of efficiency associated with the protrusions is justifiable.

The projections are preferably formed by a wavy shape of the profile nose and each have a wave crest, wherein between each of the immediately adjacent wave crests each have a wave trough is arranged. In this case, it is preferred that the peaks extend in the direction of flow up to the maximum of the thickness profile of the rotor blade. Alternatively preferably, the projections extend to 10% to 15% of that chord length of the rotor blade at the location of the respective summit. In this case, it is preferred that the heights of the peaks correspond to 4% to 12%, preferably 5%, of that chord length of the rotor blade at the location of the respective summit. Furthermore, it is particularly preferred that the distances of the peaks to the immediately adjacent peaks correspond to 30% to 45% of that chord length of the rotor blade at the location of the respective summit.

Alternatively or additionally, it is preferred that the projections are cylindrical, cuboidal, hemispherical, dome-shaped and / or conical, the diameter of which preferably corresponds in the range of 1% to 3% of that chord length of the rotor blade at the location of the respective projection. Here it is preferred that the heights of the peaks correspond to 0.2% to 1.5% of that chord length of the rotor blade at the location of the respective summit. Furthermore, it is particularly preferred that the distances of the peaks to the immediately adjacent peaks correspond to 2% to 10%, in particular 4% to 5%, of that chord length of the rotor blade at the location of the respective summit. Moreover, it is particularly preferred that the offsets of the peaks away from the leading edge in the flow direction correspond to 0% to 3%, in particular 1% to 2%, of the chord length of the rotor blade at the location of the respective peak.

It is conceivable that the projections extend only on the suction side or only on the pressure side or both on the suction side and on the pressure side of the rotor blade. Furthermore, it is conceivable that the projections are provided in the region of the expected stagnation point at nominal wind speed.

• 1 eine perspektivische Darstellung einer ersten Ausführungsform des erfindungsgemäßen Rotorblatts,
• 2 eine perspektivische Darstellung von Detail Y aus 1,
• 3 eine perspektivische Darstellung eines Ausrisses einer zweiten Ausführungsform des erfindungsgemäßen Rotorblatts,
• 4 eine Profilschnittdarstellung der Profilnase der zweiten Ausführungsform und
• 5 ein Diagramm, bei dem ein Auftriebskoeffizient gegen den Anstellwinkel aufgetragen ist.

In the following, a preferred embodiment of the rotor blade according to the invention will be explained with reference to the accompanying schematic drawings. Show it:

• 1 a perspective view of a first embodiment of the rotor blade according to the invention,
• 2 a perspective view of detail Y from 1 .
• 3 a perspective view of an outbreak of a second embodiment of the rotor blade according to the invention,
• 4 a profile sectional view of the profile nose of the second embodiment and
• 5 a diagram in which a buoyancy coefficient is plotted against the angle of attack.

Like it out 1 to 5 can be seen, has a rotor blade 1 a rotor of a wind turbine a leading edge 2 and a trailing edge 3 on, with wind being the rotor blade 1 flows, first on the leading edge 2 hits, then the rotor blade 1 flows around generating lift and then at the trailing edge 3 from the rotor blade 1 flows. The flow around the rotor blade 1 takes place substantially perpendicular to the longitudinal direction of the rotor blade 1 , wherein the direction of the flow around as the flow direction 26 is designated. The rotor blade 1 extends in its longitudinal direction from its root 4 up to its peak 5 where the direction is from the root 4 to the top 5 as the spanwise direction 27 is designated. The distance from the front edge 2 to the trailing edge 3 in the flow direction 26 seen as the chord length 28 designated. At the one Side of the rotor blade 1 , at the flow around the rotor blade 1 Overpressure is present than the pressure side 29 whereas that side of the rotor blade 1 , at the flow around the rotor blade 1 There is negative pressure, as the suction side 30 is designated. The rotor has a hub to which the rotor blade 1 with its root 4 is mounted. The rotor rotates during operation of the wind turbine around the axis of rotation of the hub, leaving the tip 5 the area of the rotor blade 1 is, which has the highest movement speed. The span 8th of the rotor blade 1 is the distance between the root 4 and the top 5 , The rotor blade 1 is designed for a nominal wind with a nominal wind speed. This results for the rotor blade 1 a design adjustment angle 25 in which the maximum glide ratio is given at the nominal wind speed on condition that the wind is flowing. It is conceivable that the distance of the design angle of attack to the angle of attack, at which the maximum glide ratio prevails, is a maximum of +/- 5%.

The rotor blade 1 is from an interior area 6 and an outdoor area 7 formed, with the interior area 6 from the root 4 to the middle of the rotor blade 1 extends and the outdoor area 7 from the top 5 to the interior 6 extends. The interface between the interior 6 and the outdoor area is 68% of the span 8th of the rotor blade 1 from the root 4 seen in the spanwise direction 27 , Thus, the length is 9 of the outdoor area 7 32% of the span 8th ,

The flow direction 26 faces facing the rotor blade 1 one the leading edge 2 having profile nose 10 on. The profile nose 10 has a plurality of in the spanwise direction 27 of the rotor blade 1 juxtaposed projections 11 on top of the profile nose 10 protrude. The projections 11 each have a peak 12 Locally, that area of the respective projection 11 is the most of the surface of the profile nose 10 protrudes. Between two immediately adjacent projections 11 is each a trough 13 arranged, which is the level of the surface profile nose 10 corresponds to that between the protrusions 11 is present.

According to the first embodiment, as in 1 and 2 is shown, the projections 11 from a wavy shape of the profile nose 10 educated. The profile nose 10 has a plurality of wave crests 14 as the protrusions, wherein between two of the immediately adjacent wave crests 14 one wave trough each 15 is arranged, that of the hollow 13 equivalent. The wavy shape of the profile nose 10 is designed such that the wave crests 14 and the troughs 15 in the flow direction 26 seen to extend to 12% of the local chord length. Alternatively, it is conceivable that the wave crests 14 and the troughs 15 in the flow direction 26 seen to the maximum 16 the thickness of the rotor blade 1 extend.

According to the second, to the first alternative embodiment, as in 3 and 4 is shown, the projections 11 cylindrical, wherein the cylinder axes of the projections 11 perpendicular to the surface of the profile nose 10 stand. The projections 11 are on the pressure side 29 of the rotor blade 1 along the front edge 2 lined up in parallel and from the surface of the profile nose 10 arranged above. The projections 11 are as protrusion bodies 17 formed at the profile nose 10 are attached. As the protrusion bodies 17 Rivets with a cylinder head are conceivable in the material of the profile nose 10 are riveted. Other shapes, bulges from the surface of the profile nose 10 and body for the projections 11 are also possible.

The vertical distance of one of the peaks 12 to the surface of the profile nose 10 is the height 18 this summit 12 , Further, the distance is one of the peaks 12 to an immediately adjacent summit 12 the distance 19 this summit 12 , In addition, the offset 20 one of the peaks 12 the distance of this summit 12 from the front edge 2 in the flow direction 26 seen. The heights 18 the summit 12 and the distances 19 the summit 12 to the immediately adjacent peaks 12 and the offenses 20 the summit 12 away from the leading edge 2 in the flow direction 26 are seen depending on that chord length 28 of the rotor blade 1 at the place of the respective summit 12 determined so that the buoyancy-reducing effect of the projections 11 only at those angles of attack 21 of the rotor blade 1 occurs equal to or greater than the design angle of attack 25 of the rotor blade 1 are.

The heights 18 the summit 12 and the distances 19 the summit 12 to the immediately adjacent peaks 12 and the offenses 20 the summit 12 away from the leading edge 2 in the flow direction 26 seen are directly proportional to that chord length 28 of the rotor blade 1 at the place of the respective summit 12 certainly. When determining the distances 19 can either be one of the protrusions 11 or the other of the projections 11 the two immediately adjacent projections 11 to be taken as a reference.

According to the first embodiment, the heights correspond 18 the summit 12 5% of that chord length 26 of the rotor blade 1 at the place of the respective summit 12 , Furthermore, the distances correspond 19 the summit 12 to the immediately adjacent peaks 12 38% of that chord length 26 of the rotor blade 1 at the place of the respective summit 12 , Either one of the peaks 12 or the other the summit 12 the two immediately adjacent projections 11 to be taken as a reference.

According to the second embodiment, the heights correspond 18 the summit 12 0.86% of that chord length 26 of the rotor blade 1 at the place of the respective summit 12 , Furthermore, the distances correspond 19 the summit 12 to the immediately adjacent peaks 12 4 , 3% of those chord length 26 of the rotor blade 1 at the place of the respective summit 12 , Either one of the peaks 12 or the other the summit 12 the two immediately adjacent projections 11 to be taken as a reference. In addition, the offsets correspond 20 the summit 12 away from the leading edge 2 in the flow direction 26 seen 1.57% of that chord length 26 of the rotor blade 1 at the place of the respective summit 12 ,

The heights 18 , the distances 10 and the offenses 20 are dimensioned such that the buoyancy-reducing effect of the projections occurs only when the angle of attack 21 the rotor blade 1 equal to or greater than the design angle of attack 25 is. 5 shows a diagram in which the buoyancy coefficient 22 of the rotor blade 1 above the angle of attack 21 of the rotor blade 1 is applied to its inflow. With 23 is the buoyancy course of a conventional rotor blade without the projections 11 whereas, at 24, the buoyancy curve of the rotor blade according to the invention is shown 1 with the projections 11 is shown. The design adjustment angle 25 is 4 °. At the design adjustment angle 25 sets the maximum glide ratio.

5 shows that inflows of the rotor blade according to the invention 1 that have a pitch angle 21 which is smaller than the design angle 25 is, no difference in the lift coefficient 22 to a conventional rotor blade show. Rather, the buoyancy at expansion angles divided 21 equal to or greater than the design angle of attack 25 are. In the rotor blade according to the invention 1 remains the buoyancy coefficient 24 versus the buoyancy coefficient 23 of the conventional rotor blade relatively constant, whereas the buoyancy 23 of the conventional rotor blade increases. As a result, the conventional rotor blade is sensitive to wind gusts, which lead to increased cycling of the conventional rotor blade.

By contrast, the rotor blade according to the invention 1 Protected against the influence of the harmful cyclic load, since an occurrence of the gusts of wind does not increase the cycling of the rotor blade according to the invention 1 leads.

LIST OF REFERENCE NUMBERS

1

Rotor blade of a rotor of a wind turbine

2

leading edge

3

trailing edge

4

root

5

top

6

interior

7

outdoors

8th

span

9

Exterior length

10

profile nose

11

head Start

12

summit

13

trough

14

Wellenberg

15

trough

16

Range of maximum profile thickness

17

projection body

18

height

19

distance

20

offset

21

angle of attack

22

lift coefficient

23

Buoyancy coefficient curve of an unmodified rotor blade

24

Buoyancy coefficient curve of a modified rotor blade

25

Auslegungsanstellwinkel

26

flow direction

27

span direction

28

chord length

29

pressure side

30

suction

Claims (10)

Rotor blade for a wind power plant, having a profiled nose (10) which forms the front area of the rotor blade (1) in the direction of flow (26) of the rotor blade (1) and which has the leading edge (2) of the rotor blade (1) Profile nose (10) in the spanwise direction (27) seen an outer region (7) having a plurality of in the spanwise direction (27) of the rotor blade (1) arranged side by side and of the profile nose (10) projecting projections (11), each having a summit (12), which is that portion of the associated projection (11) which protrudes most from the profile nose (10), wherein the Heights (18) of the peaks (12) and / or the distances (19) of the peaks (12) to the immediately adjacent peaks (12) and / or the gaps (20) of the peaks (12) away from the leading edge (2) in the flow direction (26) as a function of that chord length (28) of the rotor blade (1) at the location of the respective summit (12) are determined, wherein the buoyancy-reducing effect of the projections (11) only at those angles of incidence (21) of the rotor blade (1 ) equal to or greater than a design pitch angle (25) of the rotor blade (1) at which the maximum glide ratio substantially adjusts. Rotor blade according to Claim 1 wherein the heights (18) of the peaks (12) and / or the distances (19) of the peaks (12) to the immediately adjacent peaks (12) and / or the offsets (20) of the peaks (12) away from the leading edge (2) in the direction of flow (26) are directly proportional to that chord length (28) of the rotor blade (1) determined at the location of the respective peak (12). Rotor blade according to Claim 1 or 2 wherein the heights (18) of the peaks (12) to 12%, in particular 0.2 to 1.5% or 4% to 12%, of that chord length (26) of the rotor blade (1) at the location of the respective peak (12) correspond. Rotor blade according to one of Claims 1 to 3 wherein the distances (19) of the peaks (12) to the immediately adjacent peaks (12) to 50%, in particular 2% to 10%, in particular 4% to 5%, 4% to 5% or in particular 30% to 45% which correspond to chord length (26) of the rotor blade (1) at the location of the respective peak (12). Rotor blade according to one of Claims 1 to 4 in that the offsets (20) of the peaks (12) seen from the leading edge (2) in the flow direction (26) correspond to 0% to 3% of that chord length (26) of the rotor blade (1) at the location of the respective peak (12) , Rotor blade according to one of Claims 1 to 5 wherein the rotor blade (1) has a tip (5) and the outer region (7) extends from the tip (5) to a region of the rotor blade (1) which is at 50% to 70% of the span of the rotor blade (1 ) is arranged. Rotor blade according to one of Claims 1 to 6 , wherein the projections (11) of a wavy shape of the profile nose (10) are formed and each having a wave crest (14), wherein between each of the immediately adjacent wave crests (14) each have a trough (15) is arranged. Rotor blade according to Claim 7 , wherein the peaks (12) in the flow direction (26) seen to the maximum (16) of the thickness profile of the rotor blade (1) extend. Rotor blade according to one of Claims 1 to 6 , wherein the projections (11) are cylindrical, cuboid, hemispherical, dome-shaped and / or conical. Wind turbine with a rotor, the at least one rotor blade according to one of Claims 1 to 9 having.

Images