Abstract
A wind turbine blade with a plurality of flow guiding device parts attached to a profiled contour on a pressure side of the blade is described. The longitudinally extending flow guiding device parts are grouped together to form a first flow guiding device group in the transition region of the blade.
Claims
1. A blade (10) for a rotor of a wind turbine (2) having a substantially horizontal rotor shaft, said rotor comprising a hub (8), from which the blade (10) extends substantially in a radial direction when mounted to the hub (8), the blade having a longitudinal direction (r) with a tip end (14) and a root end (16) and a transverse direction, the blade further comprising: a profiled contour (40, 42, 50) including a pressure side and a suction side, as well as a leading edge (18) and a trailing edge (20) with a chord having a chord length extending there between, the profiled contour, when being impacted by an incident airflow, generating a lift, wherein the profiled contour is divided into: a root region (30) having a substantially circular or elliptical profile closest to the hub, an airfoil region (34) having a lift-generating profile furthest away from the hub, and a transition region (32) between the root region (30) and the airfoil region (34), the transition region (32) having a profile gradually changing in the radial direction from the circular or elliptical profile of the root region to the lift-generating profile of the airfoil region, characterised in that the blade is provided with a plurality of longitudinally extending flow guiding device parts (70), which are grouped together to form a first flow guiding device group (77) in the transition region (32) of the blade (10), the first flow guiding device group extending along at least a longitudinal part of the transition region (32), wherein the flow guiding device parts having a first side near the leading edge of the blade, a second side near the trailing edge of the blade, a first longitudinal end nearest the root, and a second longitudinal end nearest the tip; each of the flow guiding device parts (70) is added to the profiled contour (40, 42, 50) of the blade on the pressure side (52) of the blade (10), the flow guiding device parts together forming a substantially continuous first side facing towards the leading edge of the blade so the flow guiding parts together form a flow guiding device, and wherein the flow guiding device parts (70) are arranged so as to generate a separation of airflow from the pressure side of the blade at a point between the flow guiding device parts (70) and the trailing edge (20) of the blade, when the blade is impacted by the incident airflow; the flow guiding device parts are spoiler device parts, wherein obstruction results in a higher pressure after the flow guiding device parts and between the flow guiding device parts and the trailing edge due to a detachment of airflow.
2. The wind turbine blade according to claim 1, wherein the flow guiding device parts are shaped as planar elements protruding from the profile.
3. The wind turbine blade according to claim 1, wherein the flow guiding device parts are shaped so that they have an inflow surface with a start point (74) oriented towards the leading edge (18) of the blade (10) and an end point (76) oriented towards the trailing edge (20) of the blade (10), the distance between the inflow surface (72) and the profiled contour (40, 42, 50) increasing from the start point (74) to the end point (76).
4. The wind turbine according to claim 1, wherein individual flow guiding parts (70) are arranged juxtaposed in the longitudinal direction of the wind turbine blade.
5. The wind turbine blade according to claim 4, wherein the flow guiding parts are arranged so as to abut each other at longitudinal ends.
6. The wind turbine blade according to claim 1, wherein the flow guiding device parts are arranged on a common, longitudinally extending base.
7. The wind turbine blade according to claim 1, wherein the individual flow guiding device parts are substantially straight in the longitudinal direction.
8. The wind turbine blade according to claim 1, wherein the individual flow guiding device parts are curved in the longitudinal direction.
9. The wind turbine blade according to claim 1, wherein the first flow guiding device group has a corrugated design in the longitudinal direction.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The invention is explained in detail below with reference to the drawing(s), in which
(2) FIG. 1 shows a wind turbine,
(3) FIG. 2 shows a schematic view of a first embodiment of a wind turbine blade provided with flow guiding device parts according to the invention,
(4) FIG. 3 shows a schematic view of an airfoil profile,
(5) FIG. 4 shows various cross-sectional designs of flow guiding device parts according to the invention,
(6) FIG. 5 shows a schematic view of a second embodiment of a wind turbine blade provided with flow guiding device parts according to the invention,
(7) FIG. 6 shows a schematic view of a first embodiment of flow guiding device parts according to the invention, seen from the side,
(8) FIG. 7 shows a schematic view of the first embodiment of flow guiding device parts according to the invention, seen from the top,
(9) FIG. 8 shows a schematic view of a second embodiment of flow guiding device parts according to the invention, seen from the top,
(10) FIG. 9 shows a schematic view of a third embodiment of flow guiding device parts according to the invention, seen from the side,
(11) FIG. 10 shows a schematic view of the third embodiment of flow guiding device parts according to the invention, seen from the top,
(12) FIG. 11 shows a schematic view of the fourth embodiment of flow guiding device parts according to the invention, seen from the top,
(13) FIG. 12 shows a schematic view of the fifth embodiment of flow guiding device parts according to the invention, seen from the top,
(14) FIG. 13 shows a schematic view of the sixth embodiment of flow guiding device parts according to the invention, seen from the top,
(15) FIG. 14 shows a schematic view of the seventh embodiment of flow guiding device parts according to the invention, seen from the top,
(16) FIG. 15 shows a schematic view of the eighth embodiment of flow guiding device parts according to the invention, seen from the side,
(17) FIG. 16 shows a schematic view of the ninth embodiment of flow guiding device parts according to the invention, seen from the side,
(18) FIG. 17 shows a schematic view of the tenth embodiment of flow guiding device parts according to the invention, seen from the side,
(19) FIG. 18 shows a schematic view of a first embodiment of a flow guiding device part according to the invention,
(20) FIG. 19 shows a schematic view of a second embodiment of a flow guiding device part according to the invention,
(21) FIG. 20 shows cross-sections of various designs of flow guiding device parts according to the invention,
(22) FIG. 21 illustrates the attachment of flow guiding device parts to a surface of a wind turbine blade,
(23) FIG. 22 shows a rear edge height of a first flow guiding device according to the invention as a function of the radial distance from the hub,
(24) FIG. 23a shows the rear edge height of a second flow guiding device according to the invention as a function of the radial distance from the hub,
(25) FIG. 23b shows the rear edge height of a third flow guiding device according to the invention as a function of the radial distance from the hub
(26) FIG. 24 shows an embodiment of flow guiding device parts provided with stiffening members, and
(27) FIG. 25 shows an embodiment, where ends of the device parts are provided with notches.
DETAILED DESCRIPTION OF THE INVENTION
(28) FIG. 1 illustrates a conventional modern upwind wind turbine according to the so-called Danish concept with a tower 4, a nacelle 6 and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub 8 and three blades 10 extending radially from the hub 8, each having a blade root 16 nearest the hub and a blade tip 14 furthest from the hub 8.
(29) FIG. 3 shows a schematic view of an airfoil profile 50 of a typical blade of a wind turbine depicted with the various parameters, which are typically used to define the geometrical shape of an airfoil. The airfoil profile 50 has a pressure side 52 and a suction side 54, which during usei.e. during rotation of the rotornormally face towards the windward side and the leeward side, respectively. The airfoil 50 has a chord 60 with a chord length c extending between a leading edge 56 and a trailing edge 58 of the blade. The airfoil 50 has a thickness t, which is defined as the distance between the pressure side 52 and the suction side 54. The thickness t of the airfoil varies along the chord 60. The deviation from a symmetrical profile is given by a camber line 62, which is a median line through the airfoil profile 50. The median line can be found by drawing inscribed circles from the leading edge 56 to the trailing edge 58. The median line follows the centres of these inscribed circles and the deviation or distance from the chord 60 is called the camber f. The asymmetry can also be defined by use of parameters called the upper camber and lower camber, which are defined as the distances from the chord 60 and the suction side 54 and pressure side 52, respectively.
(30) FIG. 2 shows a schematic view of a first embodiment of a wind turbine blade 10 according to the invention. The wind turbine blade 10 has the shape of a conventional wind turbine blade and comprises a root region 30 closest to the hub, a profiled or an airfoil region 34 furthest away from the hub and a transition region 32 between the root region 30 and the airfoil region 34. The blade 10 comprises a leading edge 18 facing the direction of rotation of the blade 10, when the blade is mounted on the hub, and a trailing edge 20 facing the opposite direction of the leading edge 18.
(31) The airfoil region 34 (also called the profiled region) has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region 30 due to structural considerations has a substantially circular or elliptical cross-section, which for instance makes it easier and safer to mount the blade 10 to the hub. The diameter (or the chord) of the root region 30 is typically constant along the entire root area 30. The transition region 32 has a transitional profile 42 gradually changing from the circular or elliptical shape 40 of the root region 30 to the airfoil profile 50 of the airfoil region 34. The width of the transition region 32 typically increases substantially linearly with increasing distance r from the hub.
(32) The airfoil region 34 has an airfoil profile 50 with a chord extending between the leading edge 18 and the trailing edge 20 of the blade 10. The width of the chord decreases with increasing distance r from the hub.
(33) The chords of different sections of the blade normally do not lie in a common plane, since the blade may be twisted and/or curved (i.e. pre-bent), thus providing the chord plane with a correspondingly twisted and/or curved course, this being most often the case in order to compensate for the local velocity of the blade being dependent on the radius from the hub.
(34) The wind turbine blade 10 according to the invention is provided with a number of flow guiding device parts 70, which are grouped together and protrude from the pressure side of the blade in at least the transition region 32 of the blade. However, advantageously the flow guiding device parts 70 may also extend into the airfoil region 34 and/or the root region 30 of the blade. The flow guiding device parts 70 comprise an inflow surface with a start point 74 and an end point 76.
(35) The cross sectional design of the flow guiding device parts may take many shapes and still obtain a pressure build up on the pressure side of the blade and thus increase the lift of the particular blade section. As a first example, the flow guiding device parts may comprise a plate-shaped element or rib, which is angled forwards towards the leading edge of the blade as shown in FIG. 4 (a). In this embodiment, the plate-shaped element is located in front of a normal to the profiled contour at an attachment point of the plate-shaped element, i.e. between said normal and the leading edge of the blade. This embodiment has the advantage that an additional pressure is built up in front of the flow guiding device parts. A second example is shown in FIG. 4 (b), in which a plate-shaped element is angled backwards towards the trailing edge of the blade. A third example is shown in FIG. 4 (c), in which a plate-shaped element protrudes substantially normal to the surface of the wind turbine blade. A forth example is shown in FIG. 4 (d), in which the flow guiding device parts comprise a triangular or wedge-shaped cross section similar to those shown in WO2007/118581.
(36) In FIGS. 4 (b) and (d), the flow guiding device parts comprise an inflow surface with a start point and an end point. The angles and shape of the inflow surface may advantageously correspond to the designs proposed in European patent application EP08171530.2 by the present applicant. In FIGS. 4 (a)-(d), the distance of a distal point of the flow guiding device to the surface of the blade may advantageously correspond to the designs proposed in European patent application EP08171533.6 by the present applicant.
(37) FIG. 18 shows a first embodiment of a flow guiding device part 70 according to the invention. The flow guiding device is formed as a longitudinally extending device having a base 90. The base 90 comprises a first longitudinally end 91, whichwhen the flow guiding device 70 is attached to the profiled contour of the wind turbine blade 10is arranged nearest the root end of the blade and a second longitudinal end 92, which is arranged nearest the tip end of the blade 10. The base 90 further comprises a first side 93 arranged nearest the leading edge 18 of the blade 10 and a second side 94 arranged nearest the trailing edge 20 of the blade. The base 90 also comprises a first surface 95, which is attached to surface of the blade 10, and a second surface, which faces away from the surface of the blade 10. A plate-shaped element 97 protrudes from the second surface 96 of the base 90 from a part substantially in the middle between the first side 93 and the second side 94. The plate-shaped element 97 extends longitudinally along the entire longitudinal extent of the base 90. The plate-shaped element comprises a front surface 98, which faces towards the leading edge 18 of the blade 10, and a back surface 99, which faces towards the trailing edge 20 of the blade 10. During operation of the wind turbine, the front surface 98 of the plate-shaped 97 element is thus impacted by an oncoming airstream. The plate-shaped element 97 functions as an obstruction to the flow on the pressure side of the profile. After the flow guiding device, i.e. between the flow guiding device and the trailing edge of the blade, a separation of the airflow occurs. This obstruction is resulting in a higher pressure after the flow guiding device, i.e. between the flow guiding device and the trailing edge of the wind turbine blade, due to a detachment of the flow. This higher pressure contributes to a higher lift in the longitudinal section, in which the flow guiding device 70 is arranged.
(38) FIG. 19 shows a second embodiment of a flow guiding device part 170 according to the invention, wherein like numerals refer to like parts of the embodiment shown in FIG. 18. Therefore, only the difference between the two embodiments is described. In this embodiment, the plate-shaped element 197 is angled forward so that the plate-shaped element 197 forms a first angle with the base 190. Thus, the front surface 198 also faces slightly downwards towards the base 190 and the surface of the blade 10. When the front surface 198 during normal operation of the wind turbine is impacted by an oncoming airstream, an air pocket is formed in front of the front surface, which increases the pressure in front of the flow guiding device, and which guides the airflow around the flow guiding device 170. Thus, an increased pressure is built up both in front of and behind the flow guiding device 170. Thereby, the lift is increased along a large part of the blade section. The first angle is advantageously at least 20 degrees and angles around 30 to 45 degrees have shown excellent results, both with respect to the gain in lift and with regards to the flexibility of the flow guiding device.
(39) However, the plate-shaped element need not be protruding substantially normal to the base (and the profiled contour of the blade) as shown in FIG. 18 or be forwardly angled as shown in FIG. 19. Also, the plate-shaped element need not be protruding from a middle part of the base. FIG. 20 shows variations of the cross-sectional design of the flow guiding device parts.
(40) FIGS. 20 (a)-(e) show different examples of flow guiding device parts, which as such are shaped as angle bars. In all the embodiments, it is assumed that the leading edge of the blade is arranged to the right and the trailing edge to the left. Thus, during normal operation of a wind turbine, the oncoming airstream is from the right to the left.
(41) In embodiment (a), the plate-shaped element is angled forwards and protrudes from the second side of the base. In embodiment (b), the plate-shaped element is angled backwards and protrudes from the first side of the base. In these two embodiments, the angle between the plate-shaped elements of (a) and (b) forms an angle of 45 degrees with the base.
(42) In embodiment (c), the plate-shaped element is angled forwards and protrudes from the second side of the base. In embodiment (d), the plate-shaped element is angled backwards and protrudes from the second side of the base. In these two embodiments, the plate-shaped element forms an angle of approximately 135 degrees with the base.
(43) In embodiment (e), the plate-shaped element protrudes substantially normally to the base from the first side of the base.
(44) Embodiments (f)-(h) show embodiments, where the plate-shaped element protrudes from a middle part of the base, i.e. between the first side and the second side of the base. The plate-shaped element may e.g. be forwardly angled as shown in embodiment (f), be backwardly angled as shown in embodiment (g) or protrude normally from the base as shown in embodiment (h).
(45) In all the previous embodiments, the plate-shaped element is designed as a planar element. However, the plate-shaped elements of the previous embodiments may be slightly bent or curved, e.g. in a concave shape as shown in embodiment (i) or a convex shape as shown in embodiment (j). Yet again, the plate-shaped element may comprise different planar parts, which are differently angled with respect to the base, the plate-shaped element thus having a discontinuous design as shown in embodiment (k).
(46) The flow guiding device is typically mounted on a curved surface of the wind turbine blade. Thus, the sides of the base may potentially detach slightly from the surface of the blade as shown in FIG. 21 (a). Accordingly, it is advantageous that the base of the flow guiding device is made of a flexible material so that stress formations are reduced along the entire base plate. Further, by making the plate-shaped element flexible, peel forces are reduced at the ends of the flow guiding device. This can be obtained by forming the base as a relatively thin plate, e.g. made of a composite material, such as a polymer matrix material reinforced with fibreglass. Alternatively, the base may be slightly curved as shown in FIG. 21 (b) so as to complement the surface of the wind turbine blade. The base may be attached to the surface of the blade by e.g. adhering the first surface of the base to the surface of the blade, or by connecting it to the blade via connection means, such as screws or nuts and bolts. It is also possible to mould the flow guiding device on to the surface of the blade. Yet again, the flow guiding device may be attached to the blade surface by use of magnet means, if for instance the base plate and/or the blade shell comprise a magnetisable material. Also, the curvature of the first surface of the base may vary in the longitudinal direction of the base in order to accommodate to the varying shape of the wind turbine blade.
(47) FIG. 5 shows a schematic view of a wind turbine blade provided with flow guiding device parts 170, which are grouped together in a first flow guiding device group 177 in the transition region of the blade and protruding from the pressure side of the blade. The first flow guiding device group 177 further extends slightly into the root region and the airfoil region of the blade. The first flow guiding device group 177 is shown as extending substantially parallel to a longitudinal axis (or pitch axis) of the blade. However, it may be arranged slightly skewed or curved compared to said longitudinal axis.
(48) FIG. 6 depicts the flow guiding device group 177, seen from the side. As can be seen the group 177 comprises a number of individual flow guiding device parts 170, which mutually are separated by gaps 181. The individual parts may for instance have a longitudinal extent of between 50 cm and 200 cm, e.g. 100 cm. The gaps 181 between adjacent flow guiding device parts 170 may for instance be between 5 mm and 30 mm. According to another embodiment (not shown), the flow guiding device parts abut each other. The shown modular construction makes the construction of the flow guiding device group 170 more flexible than conventional longitudinally extending flow guiding devices and reduces peel forces, which normally occur at the ends of the flow guiding devices. Thus, the modular parts will have a smaller tendency to break off from the surface of the blade.
(49) FIG. 7 shows the flow guiding device parts 170 seen from the top, here depicted as a proximal part of a plate-shaped element. In the shown embodiment, the gaps 181 between adjacent flow guiding device parts 170 are closed by intermediate elements 179 made of a flexible material, such as rubber. In this particular embodiment, the intermediate elements 179 are attached to a front surface of the plate-shaped elements 170.
(50) FIG. 8 shows a second embodiment of flow guiding device parts 270 according to the invention. In this embodiment the gaps are also closed by intermediate elements 279 made of a flexible material, such as rubber. In this embodiment, the intermediate parts fill the entire gap between the flow guiding device parts 270 and are attached to both a front surface and back surface of the flow guiding device parts 270.
(51) FIG. 9 shows a schematic view of a third embodiment of flow guiding device parts 370 according to the invention, seen from the side. In this embodiment, the flow guiding device parts 370 are partially overlapping in the longitudinal direction. Accordingly, one end of one flow guiding device part extends beyond a second end of a second flow guiding device part. The ends may be slightly angled as shown in the Figure.
(52) FIG. 10 shows a schematic view of the third embodiment of flow guiding device parts 370 according to the invention, seen from the top. It can be seen the flow guiding device parts 370 are staggered in the longitudinal direction. The back surface of one flow guiding device part may abut the front surface of a second flow guiding device part, or there may be a small gap in the transverse direction of the blade.
(53) FIG. 11 shows a schematic view of the fourth embodiment of flow guiding device parts 470 according to the invention, seen from the top. In this embodiment, the flow guiding device parts are alternately arranged in front of and behind other flow guiding device parts.
(54) FIG. 12 shows a schematic view of the fifth embodiment of flow guiding device parts 570 according to the invention, seen from the top, which is similar to the fourth embodiment with the exception that the flow guiding device parts 570 are alternately convex and concave in the longitudinal direction. In the shown embodiment, two flow guiding device parts are arranged behind the others. However, they may also advantageously be arranged in front of the other flow guiding device parts, thereby obtaining a slightly different overall design.
(55) FIG. 13 shows a schematic view of the sixth embodiment of flow guiding device parts 670 according to the invention, seen from the top. In this embodiment, the first flow guiding device group consists of alternately convex and concave flow guiding device parts, which are interconnected. Overall, a corrugated design is obtained in the longitudinal direction of the blade.
(56) FIG. 14 shows a schematic view of the seventh embodiment of flow guiding device parts according to the invention, seen from the top, in which individual flow guiding device parts 770 are interconnected via intermediate flow guiding device part 779. Overall, an alternative corrugated design is obtained in the longitudinal direction of the blade.
(57) FIG. 15 shows a schematic view of the eighth embodiment of flow guiding device parts according to the invention, seen from the side. In this embodiment, the first flow guiding device group comprises a number of individual flow guiding device parts 870, which are interconnected by intermediate flow guiding device parts 879. The flow guiding device 870 parts have a first stiffness, and the intermediate flow guiding device parts 879 have a second stiffness. This may for example be achieved by using different plies in the longitudinal direction of the blade, or by changing the fibre direction of such parts made of a fibre-reinforced composite material. Yet again, it is possible to achieve the varying stiffness by manufacturing the flow guiding device as a sandwich structure with different sandwich core materials, e.g. foamed plastic and balsa wood.
(58) FIG. 16 shows a schematic view of the ninth embodiment of flow guiding device parts 970 according to the invention, seen from the side. In this embodiment, the flow guiding device parts 970 are arranged on a common, longitudinally extending base. Thus, the base typically comprises a first side and second side, as well as a first longitudinal end and a second longitudinal end as shown in FIG. 18. The flow guiding device 970 parts are separated by recesses 981 or gaps.
(59) FIG. 17 shows a schematic view of the tenth embodiment of flow guiding device parts 1070 according to the invention, seen from the side, similar to the ninth embodiment. In this embodiment, the recesses 1018 comprise a bottom part, i.e. a part nearest the base and the wind turbine blade, where a keyhole design 1085 is provided at said bottom part, the key hole having a diameter, which is larger than the immediate width of the recesses 1081. This will reduce stress concentrations and peel forces even further.
(60) In a first embodiment, a height h of the first flow guiding device group may as shown in FIG. 22 be decreasing in the longitudinal direction (or radial distance from the hub) towards the tip end r of the bladeat least within the central longitudinal portion 71 of the first flow guiding device group. The height of the flow guiding device is shown as a function of the radial distance r from the hub in FIG. 20. At the longitudinal end of the flow guiding device group nearest the hub, the flow guiding device group is rounded or tapered in order to obtain a smooth transition to the profiled contour of the blade.
(61) In a second embodiment, the height of the flow guiding device group is as shown in FIG. 23a substantially constant in the longitudinal direction of the blade, at least within the central longitudinal portion 71. Furthermore, it is seen that the flow guiding device group can be rounded or tapered near the longitudinal ends of the flow guiding device group in order to obtain a smooth transition to the profiled contour of the blade.
(62) In a third embodiment, the height of the flow guiding device group increases in a first longitudinal part and decreases in a second longitudinal part as shown in FIG. 23b.
(63) When the flow guiding device part is shaped as a plate-shaped element as shown in FIG. 19, the device part may advantageously be provided with stiffening devices 1190 arranged at the back surface of the plate-shaped element as shown in FIG. 24. The stiffening devices may advantageously be formed as triangular shaped plates between the back surface and the base of the device. The stiffening devices are advantageously arranged substantially in the transverse direction of the blade, i.e. substantially parallel to the local chord.
(64) The flow guiding device or individual modules of the group of flow guiding device may advantageously be provided with a notch 1285, a cut or the like at one or both ends of the device as shown in FIG. 25. This will reduce stress concentrations and peel forces even further similar to the keyhole design shown in FIG. 17. The notches may be useful relevant shape such as triangular, rounded square or the like.
(65) The invention has been described with reference to a preferred embodiment. However, the scope of the invention is not limited to the illustrated embodiment, and alterations and modifications can be carried out without deviating from the scope of the invention.
