Vortex generator for wind turbine blade, wind turbine blade, and wind power generating apparatus

A vortex generator for wind turbine blade includes: a platform; and at least one fin disposed projecting from an upper surface of the platform, and including a leading edge and a trailing edge. A rear end surface of the at least one fin, including the trailing edge, has a shape inclined backward as a distance from a bottom surface of the platform increases in a height direction of the fin.

TECHNICAL FIELD

The present disclosure relates to a vortex generator for wind turbine blade, a wind turbine blade, and a wind power generating apparatus.

This application claims the priority of Japanese Patent Application No. 2020-197416 filed on Nov. 27, 2020, the content of which is incorporated herein by reference.

BACKGROUND

Conventionally, approaches to improve aerodynamic performance of a wind turbine blade have been sought with the object of improving operation efficiency of a wind turbine. In one of the approaches, a vortex generator is disposed on a surface of the wind turbine blade to suppress separation of a flow along the surface of the wind turbine blade.

Patent Documents 1 to 8 disclose a vortex generator having a base portion mounted on a surface of a wind turbine blade, and a fin disposed upright on the base portion.

CITATION LIST

SUMMARY

Technical Problem

Meanwhile, since a surface of a wind turbine blade is curved, the smaller a platform of a vortex generator is, the easier the vortex generator is attached to the wind turbine blade. On the other hand, as the size of the wind turbine blade increases, the size of the vortex generator also tends to increase. Therefore, it is desired to realize a vortex generator mounted with a fin as large as possible on a platform, without excessively increasing the size of the platform.

In view of the above, an object of at least one embodiment of the present invention is to provide a vortex generator for wind turbine blade, a wind turbine blade, and a wind power generating apparatus capable of mounting an enlarged fin while suppressing an increase in platform size.

Solution to Problem

A vortex generator for wind turbine blade according to at least one embodiment of the present invention, includes: a platform; and at least one fin disposed projecting from an upper surface of the platform, and including a leading edge and a trailing edge. A rear end surface of the at least one fin, including the trailing edge, has a shape inclined backward as a distance from a bottom surface of the platform increases in a height direction of the fin.

A wind turbine blade according to at least one embodiment of the present invention, includes: a blade body; and the above-described vortex generator attached to a surface of the blade body.

A wind power generating apparatus according to at least one embodiment of the present invention, includes: a wind turbine rotor including the above-described wind turbine blade; and a generator configured to be driven by the wind turbine rotor.

Advantageous Effects

According to at least one embodiment of the present invention, provided are a vortex generator for wind turbine blade, a wind turbine blade, and a wind power generating apparatus capable of mounting an enlarged fin while suppressing an increase in platform size.

DETAILED DESCRIPTION

Some embodiments of the present invention will be described below with reference to the accompanying drawings. It is intended, however, that unless particularly identified, dimensions, materials, shapes, relative positions and the like of components described or shown in the drawings as the embodiments shall be interpreted as illustrative only and not intended to limit the scope of the present invention.

(Configuration of Wind Power Generating Apparatus)

First, with reference toFIGS.1and2, the overall configuration of a wind power generating apparatus and a wind turbine blade to which a vortex generator is applied according to some embodiments will be described.FIG.1is a schematic configuration view of the wind power generating apparatus according to an embodiment, andFIG.2is a perspective view of the wind turbine blade according to an embodiment.

As shown inFIG.1, a wind power generating apparatus40includes a rotor42composed of at least one (for example, three) wind turbine blade1and a hub43. It is configured such that the wind turbine blade1is radially mounted on the hub43, the rotor42is rotated by receiving wind with the wind turbine blade1, and electricity is generated by a generator (not shown) connected to the rotor42. In the embodiment shown inFIG.1, the rotor42is supported by a nacelle44disposed on an upper side of a tower46. Further, the tower46is disposed upright on a base structure48(a foundation structure, a floating structure, or the like) disposed on water or on land.

(Configuration of Wind Turbine Blade)

As shown inFIG.2, the wind turbine blade1includes a blade body2, and vortex generators10disposed on the surface of the blade body2(blade surface).

The blade body2includes a blade root3mounted on the hub43of the wind power generating apparatus40, a blade tip4located farthest from the hub43, and an airfoil portion5extending between the blade root3and the blade tip4. Further, the wind turbine blade1has a leading edge6and a trailing edge7from the blade root3to the blade tip4. Furthermore, an exterior shape of the wind turbine blade1is formed by a pressure surface (concave surface)8and a suction surface (convex surface)9disposed opposite to the pressure surface8.

In the wind turbine blade1shown inFIG.2, the plurality of the vortex generators are attached to the suction surface9of the blade body2. The plurality of vortex generators are arranged on the suction surface9of the blade body2and along a blade spanwise direction. Hereinafter, in the present specification, the “blade spanwise direction” refers to a direction connecting the blade root3and the blade tip4.

Next, the vortex generator10according to some embodiments will be described in detail with reference toFIGS.3to8.

FIG.3is a perspective view of the vortex generator according to an embodiment, andFIG.4is a plan view (a view as viewed from a fin height direction) of the vortex generator shown inFIG.3.FIG.5is a view of the vortex generator shown inFIG.4as viewed from the direction of an arrow B.FIG.6is a view showing a cross section taken along line A-A inFIG.4(a cross section including a chord and the height direction of the fin).FIGS.7and8are each a view showing a cross section orthogonal to a blade height direction of the vortex generator shown inFIG.4.

As shown inFIGS.3to6, the vortex generator10includes a platform11mounted on a surface of the wind turbine blade1(more specifically, a surface of the blade body2), and at least one fin12disposed on the platform11.

The platform11has an upper surface11awhere the fin12is disposed, and a bottom surface11bopposite to the upper surface11a. The vortex generator10is attached to the surface (for example, the suction surface9) of the blade body2via the bottom surface11b. As shown inFIGS.3and4, the platform11may have a circular shape as viewed from the height direction of the fin12. Alternatively, the platform11may have a shape other than a circle, such as an ellipse, a polygon, or the like as viewed from the height direction.

The at least one fin12is disposed projecting from the upper surface11aof the platform11. In the illustrated embodiment, two fins12A,12B are disposed on the platform11. Hereinafter, the fins12A,12B are collectively referred to as the fin12. The fin12is disposed to be inclined at a predetermined angle with respect to the wind inflow direction.

As shown inFIGS.3to6, the fin12has a leading edge13located upstream in a wind inflow direction, a trailing edge14located downstream in the wind inflow direction, a pressure surface (concave surface)15of the fin12facing upstream in the wind inflow direction, and a suction surface (convex surface)16of the fin12facing downstream in the wind inflow direction. In the fin12, a direction of straight lines each connecting the leading edge13and the trailing edge14is a chordwise direction of the fin12. Further, the fin12extends between a top portion18and a base portion17connected to the platform11, in a height direction of the fin12. The height direction of the fin12in the present specification is equal to a direction orthogonal to the bottom surface11bof the platform11.

C1to C4inFIG.4are each a contour of the fin12in the cross section orthogonal to the height direction of the fin12, and a distance from the bottom surface11bof the platform11increases from C1toward C4.

Herein, the effect of the vortex generator10will briefly be described.

Separation of a flow on the suction surface9of the wind turbine blade1is caused by gradually thickening a boundary layer from a streamline flow region in the vicinity of the leading edge6toward a turbulent flow region downstream thereof, and separating the flow before arriving at the trailing edge7. The vortex generator10attached to the wind turbine blade1generates a longitudinal vortex on the suction surface16side of the fin12with a lift produced by the fin12. Further, a flow flowing into the fin12forms a longitudinal vortex along an edge extending from a most upstream position (the leading edge13ain the base portion) toward a top portion (the leading edge13bin the top portion) of the leading edge13of the fin12. The longitudinal vortex thus generated by the fin12promotes momentum exchange in the height direction of the fin12between the inside and the outside of the boundary layer on the wind turbine blade1surface, on a wake side of the vortex generator10. Thus, the boundary phase on the surface of the wind turbine blade1becomes thin, suppressing the separation of the flow from the wind turbine blade1surface.

In some embodiments, as shown inFIGS.3to6, a rear end surface19of the at least one fin12, including the trailing edge14, has a shape inclined backward (that is, in a direction from the leading edge13toward the trailing edge14in the chordwise direction of the fin12) as a distance from the bottom surface11bof the platform11increases in the height direction of the fin12. The rear end surface19may include a flat surface including the trailing edge14.

According to the above-described embodiments, the rear end surface19of the fin12has the shape inclined backward as the distance from the bottom surface11bof the platform11increases in the height direction of the fin12. Therefore, by shifting the position of the trailing edge14bin the top portion18of the fin12, where contribution to aerodynamic performance of the wind turbine blade1is large, backward with respect to the position of the trailing edge14ain the base portion17of the fin12where the contribution to the aerodynamic performance is relatively small, a sufficient chord length of the fin12in the top portion18is secured easily. Thus, the size of the platform11can be made relatively small relative to the fin12, while maintaining the aerodynamic performance of the vortex generator10. Therefore, it is possible to obtain the vortex generator10mounted with the larger fin12while suppressing the increase in size of the platform11.

In some embodiments, in the cross section including the chord and the height direction of the fin12, an inclination angle α (seeFIG.6) of the rear end surface19with respect to the bottom surface11bof the platform11is not less than 55 degrees and not greater than 65 degrees. The inclination angle α is an angle formed by a straight line, which connects the position of the trailing edge14ain the base portion17of the fin12and the position of the trailing edge14bin the top portion18of the fin12, and a straight line including the bottom surface11bof the platform11, in the above-described cross section.

According to the above-described embodiments, since the above-described inclination angle α is not greater than 65 degrees, the trailing edge portion of the fin12has a shape inclined backward. Therefore, the position of the trailing edge14bin the top portion18of the fin12can be shifted backward by a relatively large amount with respect to the position of the trailing edge14ain the base portion17of the fin12. Thus, it becomes easy to secure a sufficient chord length of the fin12in the top portion18. Further, since the above-described inclination angle α is not less than 55 degrees, the trailing edge portion of the fin12has a shape which is not excessively inclined backward. Therefore, it is possible to obtain the vortex generator10provided with the fin12having an appropriate size, while inclining the trailing edge portion of the fin12. Thus, it is possible to relatively reduce the size of the platform11, while maintaining the aerodynamic performance of the vortex generator10.

In some embodiments, for example, as shown inFIG.6, in at least a part of a region in the height direction of the fin12, the leading edge13of the fin12is inclined backward as the distance from the bottom surface11bof the platform11increases in the height direction. In some embodiments, in the cross section including the chord and the height direction of the fin12, the inclination angle α (seeFIG.6) of the rear end surface19with respect to the bottom surface11bof the platform11is greater than an inclination angle β of the leading edge13with respect to the bottom surface11bof the platform11. Herein, the inclination angle β is an angle formed by a straight line, which connects the position of the leading edge13ain the base portion17of the fin12and the position of the leading edge13bin the top portion18of the fin12, and the straight line including the bottom surface11bof the platform11, in the above-described cross section.

According to the above-described embodiments, the cross-sectional area of the fin12in the region on the top portion18side of the fin12is easily reduced, thereby easily improving the aerodynamic performance. Thus, it is possible to relatively reduce the size of the platform11, while maintaining the aerodynamic performance of the vortex generator10.

In some embodiments, in the cross section including the chord and the height direction of the fin12, the inclination angle β of the leading edge with respect to the bottom surface of the platform11is not less than 10 degrees and not greater than 20 degrees.

According to the above-described embodiments, since the above-described inclination angle β is not less than 10 degrees, it is easy to obtain the fin12having the appropriate size, while inclining a leading edge portion13′ of the fin12. Further, since the above-described inclination angle β is not greater than 20 degrees, it is easy to ensure the aerodynamic performance of the vortex generator10. Thus, it is possible to relatively reduce the size of the platform11, while maintaining the aerodynamic performance of the vortex generator10.

In some embodiments, the leading edge13of the fin12is inclined backward to a maximum height position of the fin12(that is, the position of the top portion18of the fin12) as the distance from the bottom surface11bof the platform11increases in the height direction.

According to the above-described embodiments, since the leading edge13is inclined backward to the maximum height position of the fin12as the distance from the bottom surface11bof the platform11increases in the height direction of the fin12, it is easy to ensure the aerodynamic performance of the vortex generator10. Thus, it is possible to relatively reduce the size of the platform11, while maintaining the aerodynamic performance of the vortex generator10.

FIG.7is a view showing a cross section orthogonal to the height direction of the fin12, at a first position P1(seeFIG.6) in the height direction of the fin12, andFIG.8is a view showing a cross section orthogonal to the height direction of the fin12, at a second position P2(seeFIG.6) where the distance from the bottom surface11bof the platform11is smaller than at the first position P1. InFIG.6, Pa indicates a position of the bottom surface11bof the platform11in the height direction of the fin12, and Pb indicates a position of the top portion18of the fin12in the height direction of the fin12. Further, inFIGS.6to8, L1is a chord length of a first airfoil shape CP1, and L2is a chord length of a second airfoil shape CP2.

In some embodiments, for example, as shown inFIGS.6to8, the fin12has the first airfoil shape CP1at the first position P1(seeFIG.6) in the height direction, and has the second airfoil shape CP2at the second position P2(seeFIG.6) in the height direction, the second airfoil shape CP2including a leading edge region102which coincides with a similar figure CP1′of the first airfoil shape CP1larger in size than the first airfoil shape CP1, and a trailing edge region104with a shape from which a part of the similar figure CP1′is missing. However, inFIG.8, in the leading edge region102of the fin12, the similar figure CP1′(dashed line) of the first airfoil shape CP1and the second airfoil shape CP2(solid line) overlap each other. That is, inFIG.8, the chord length L2of the second airfoil shape CP2is shorter than a chord length L1′of the similar figure CP1′of the first airfoil shape CP1.

According to the above-described embodiments, since the second airfoil shape CP2at the second position P2on the base portion17side of the fin12has the shape, from which a part of the similar figure CP1′of the first airfoil shape larger in size than the first airfoil shape CP1at the first position P1on the top portion18side is missing, in the trailing edge region104, while basically having the shape of the similar figure CP1′, it is possible to mount the relatively large fin12on the platform11. Further, since the fin12has at the first position P1on the top portion18side the first airfoil shape CP1with a shape, from which the trailing edge portion is not missing, compared to the second airfoil shape CP2, the chord length of the fin12is easily secured in the region on the top portion18side of the fin12where the contribution to the aerodynamic performance is large. Thus, it is possible to relatively reduce the size of the platform11, while maintaining the aerodynamic performance of the vortex generator10.

In some embodiments, for example, as shown inFIGS.7and8, in the fin12, a first blade thickness ratio t1/L1at the first position P1in the height direction may be less than a second blade thickness ratio t2/L2at the second position P2where the distance from the bottom surface11bof the platform11is smaller than at the first position P1in the height direction. Note that t1is a maximum value of the blade thickness (maximum blade thickness) of the first airfoil shape CP1, and t2is a maximum value of the blade thickness (maximum blade thickness) of the second airfoil shape CP2. The blade thickness is the size (thickness) of each airfoil shape in the direction orthogonal to the chordwise direction (that is, the thickness direction of the fin12).

For example, in the examples shown inFIGS.7and8, since the fin12has at the second position P2the second airfoil shape CP2including the trailing edge region104with the shape from which a part of the similar figure CP1′of the first airfoil shape CP1is missing, the chord length L2at the second position P2is shorter than the chord length L1′of the similar figure CP1′of the first airfoil shape CP1. Thus, the first blade thickness ratio t1/L1(=t2/L1′) at the first position P1is less than the second blade thickness ratio t2/L2at the second position P2.

According to the above-described embodiments, since the fin12has the shape, in which the chord length L2relative to the maximum blade thickness t2is relatively short, at the second position P2on the base portion17side, the relatively large fin12can be mounted on the platform11. Further, since the fin12has the shape, in which the chord length L1relative to the maximum blade thickness t1is relatively long, at the first position P1on the top portion18side, the aerodynamic performance of the vortex generator10is maintained easily. Thus, it is possible to relatively reduce the size of the platform11, while maintaining the aerodynamic performance of the vortex generator10.

In some embodiments, for example, as shown inFIG.4, as viewed from the height direction of the fin12, a rear end portion14′ including the trailing edge14of the fin12projects outward from an outer edge11cof the platform11. That is, as viewed from the height direction, the position of the trailing edge14bin the top portion18of the fin12may be positioned outside the outer edge11cof the platform11.

According to the above-described embodiments, since the rear end portion14′ of the fin12projects outward from the outer edge11cof the platform11, the chord length of the fin12in the top portion18is secured easily. Thus, it is possible to easily reduce the size of the platform11, while maintaining the aerodynamic performance of the vortex generator10.

In some embodiments, the rear end portion14′ of the fin12may not project from the outer edge of the platform11. That is, as viewed from the height direction, the rear end portion14′ of the fin12may fit inside the outer edge11cof the platform11. Alternatively, as viewed from the height direction, the position of the trailing edge14bin the top portion18of the fin12may be positioned inside the outer edge11cof the platform11.

In some embodiments, for example, as shown inFIG.5, a width W of the rear end surface19of the fin12decreases as the distance from the bottom surface11bof the platform11increases in the height direction. The width W of the rear end surface19is a width of the rear end surface19in the thickness direction of the fin12(the direction orthogonal to the chordwise direction of the fin12). In the exemplary embodiment shown inFIG.5, the rear end surface19of the fin12has a trapezoidal shape, but may have a triangular shape in another embodiment.

According to the above-described embodiments, the width W of the rear end surface19of the fin12decreases as the distance from the bottom surface11bof the platform11increases in the height direction of the fin12. Thus, since the width W of the rear end surface19is relatively large in the base portion of the fin12where the contribution to the aerodynamic performance is relatively small, it is possible to mount the relatively large fin12on the platform11. Further, since the width W of the rear end surface19in the base portion of the fin12is secured, the fin12is supported easily. Furthermore, since the width W of the rear end surface19is relatively narrow in the top portion18of the fin12where the contribution to the aerodynamic performance is large, the chord length of the fin12in the top portion18is secured easily. Thus, it is possible to relatively reduce the size of the platform11, while maintaining the aerodynamic performance of the vortex generator10.

In some embodiments, for example, as shown inFIG.4, the fin12includes the leading edge portion13′ having the curved contour in the cross section orthogonal to the height direction of the fin12. InFIG.4, as the contours C1to C4of the fin12in the cross section orthogonal to the height direction of the fin12, the leading edge portion13′ has the curved contours.

According to the above-described embodiments, since the fin12includes the leading edge portion13′ having the curved contour in the cross section orthogonal to the height direction of the fin12, when the vortex generator10is installed on the wind turbine blade1, a resistance to the flow of air flowing into the vortex generator10is reduced easily. Therefore, the aerodynamic performance of the vortex generator10is improved.

Further, in some embodiments, for example, as shown inFIG.4, the fin12has the shape symmetrical about the chord of the fin12. InFIG.4, as to the contours C1to C4of the fin12in the cross section orthogonal to the height direction of the fin12, the leading edge portion13′ has the curved contours. Further, inFIG.4, the contours C1to C4each have the shape symmetrical about the chord of the fin12. InFIG.4, the contours C1to C4each have the shape symmetrical about the chord of the fin12.

In the above-described embodiments, since the fin12has the shape symmetrical about the chord of the fin12, the vortex generator10is molded easily compared with the case where the fin12has a shape asymmetrical about the chord. For example, molding by injection molding or the like is facilitated.

In some embodiments, the fin12may have the shape asymmetrical about the chord of the fin12.

In some embodiments, the blade thickness ratio (maximum blade thickness/chord length) of the fin12may be at least 10% and at most 20%. In an embodiment, in a region of at least 30% in the height direction of the fin12, the blade thickness ratio of the fin12may be at least 10% and at most 20%. In an embodiment, in an entire region in the height direction of the fin12, the blade thickness ratio of the fin12may be at least 10% and at most 20%.

According to the above-described embodiments, since the blade thickness ratio of the fin12is at least 10% and at most 20%, the vortex generator10tends to have good aerodynamic performance.

In some embodiments, the vortex generator10(the platform11and the fin12) may be made of a resin. The resin used as the material of the vortex generator10may be a thermoplastic such as ASA (Acrylate Styrene Acrylonitrile), AES (Acrylonitrile-Ethylene-Styrene), or the like.

According to the above-described embodiments, since the platform11and the fin12are made of the platform11and the fin12are made of a resin, molding is relatively easily.

When a vortex generator having a general shape is formed by injection molding, the vortex generator can be molded with a pair of upper and lower halves of a mold (that is, a mold halved in the height direction of the fin). However, in the vortex generator10according to the above-described embodiments, since the rear end surface19of the fin12has the shape inclined backward as the distance from the bottom surface11bof the platform11increases in the height direction of the fin12, it is difficult to form the vortex generator10only with the pair of upper and lower halves of the mold.

Therefore, when the vortex generator10according to the above-described embodiments is formed by injection molding, in addition to the pair of upper and lower molds, a mold is used which corresponds to the trailing edge portion (the portion including the rear end surface19inclined backward) of each fin12. For the pair of upper and lower molds, the molded product is released in the vertical direction, whereas for the mold corresponding to the trailing edge portion of each fin12, the molded product is released in the longitudinal direction of the fin12(the chordwise direction of the fin12). In this manner, the vortex generator10according to the above-described embodiments can be molded by injection molding.

In some embodiments, a mounting angle (chordwise direction) of the fin12(the fin12A and/or the fin12B) is not less than 12 degrees and not greater than 18 degrees with respect to the wind inflow direction. By attaching the vortex generator10having such fin12to the wind turbine blade1, it is possible to effectively suppress the separation of the flow from the wind turbine blade1surface.

In some embodiments, for example, as shown inFIGS.3to5, each of the fins12A,12B may be disposed such that a distance between the pair of fins12A,12B widens from upstream toward downstream in the wind inflow direction (that is, from the leading edge6side toward the trailing edge7side of the wind turbine blade1(seeFIG.2)).

When the plurality of fins are arranged along the blade spanwise direction of the wind turbine blade, from the viewpoint of aerodynamic performance, it is considered that the plurality of fins are disposed such that a distance between adjacent pressure surfaces is longer than a distance between adjacent suction surfaces. In this regard, in the above-described embodiments, since the fin12A and the fin12B are disposed on the platform11such that the suction surface16of the fin12A and the suction surface16of the fin12B face each other, the distance between the fin12A and the fin12B can relatively be short. Thus, it becomes easier to reduce the size of the platform11.

In some embodiments, for example, as shown inFIG.4, the platform11is configured to have a circular shape as viewed from the height direction of the fin12.

According to the above-described embodiments, since the platform11has the circular shape as viewed from the height direction of the fin12, the platform11is easily and stably adhered to the surface of the wind turbine blade1. Thus, it is possible to suppress separation of the vortex generator10from the wind turbine blade1.

The contents described in the above embodiments would be understood as follows, for instance.

(1) A vortex generator (10) for wind turbine blade (1) according to at least one embodiment of the present invention, includes: a platform (11); and at least one fin (12) disposed projecting from an upper surface (11a) of the platform, and including a leading edge (13) and a trailing edge (14). A rear end surface (19) of the at least one fin, including the trailing edge, has a shape inclined backward as a distance from a bottom surface (11b) of the platform increases in a height direction of the fin.

With the above configuration (1), the rear end surface of the at least one fin has the shape inclined backward as the distance from the bottom surface of the platform increases in the height direction of the fin. Therefore, by shifting the position of the trailing edge in the top portion of the fin, where contribution to aerodynamic performance of the wind turbine blade is large, backward with respect to the position of the trailing edge in the base portion of the fin where the contribution to the aerodynamic performance is relatively small, a sufficient chord length of the fin in the top portion is secured easily. Thus, the size of the platform can be made relatively small relative to the fin, while maintaining the aerodynamic performance of the vortex generator. Therefore, it is possible to obtain the vortex generator mounted with the larger fin while suppressing the increase in size of the platform.

(2) In some embodiments, in the above configuration (1), the fin has a first airfoil shape (CP1) at a first position (P1) in the height direction, and has a second airfoil shape (CP2) at a second position (P2) where the distance from the bottom surface of the platform is smaller than at the first position in the height direction, the second airfoil shape including a leading edge region (102) which coincides with a similar figure (CP1′) of the first airfoil shape larger in size than the first airfoil shape, and a trailing edge region (104) with a shape from which a part of the similar figure is missing.

With the above configuration (2), the fin has the first airfoil shape at the first position in the height direction, and has the second airfoil shape at the second position where the distance from the bottom surface of the platform is smaller than at the first position, the second airfoil shape including the leading edge region which coincides with the similar figure of the first airfoil shape larger in size than the first airfoil shape, and the trailing edge region with the shape from which a part of the similar figure is missing. That is, since the second airfoil shape at the second position on the base portion side of the fin has the shape, from which a part of the similar figure of the first airfoil shape larger in size than the first airfoil shape at the first position on the top portion side is missing, in the trailing edge region, while basically having the shape of the similar figure, it is possible to mount the relatively large fin on the platform. Further, since the fin has at the first position on the top portion side the first airfoil shape with a shape, from which the trailing edge portion is not missing, relative to the second airfoil shape, the chord length of the fin is easily secured in the region on the top portion side of the fin where the contribution to the aerodynamic performance is large. Thus, it is possible to relatively reduce the size of the platform, while maintaining the aerodynamic performance of the vortex generator.

(3) In some embodiments, in the above configuration (1) or (2), in the fin, a first blade thickness ratio at a first position in the height direction is less than a second blade thickness ratio at a second position where the distance from the bottom surface of the platform is smaller than at the first position in the height direction.

With the above configuration (3), the first blade thickness ratio at the first position in the height direction is less than the second blade thickness ratio at the second position where the distance from the bottom surface of the platform is smaller than at the first position in the height direction. That is, since the fin has the shape, in which the chord length relative to the maximum blade thickness is relatively short, at the second position on the base portion side, the relatively large fin can be mounted on the platform. Further, since the fin has the shape, in which the chord length relative to the maximum blade thickness is relatively long, at the first position on the top portion side, the aerodynamic performance of the vortex generator is maintained easily. Thus, it is possible to relatively reduce the size of the platform, while maintaining the aerodynamic performance of the vortex generator.

(4) In some embodiments, in the above configurations (1) to (3), a width of the rear end surface of the fin decreases as the distance from the bottom surface of the platform increases in the height direction.

In the above configuration (4), the width of the rear end surface of the fin decreases as the distance from the bottom surface of the platform increases in the height direction. Thus, since the width of the rear end surface is relatively large in the base portion of the fin where the contribution to the aerodynamic performance is relatively small, it is possible to mount the relatively large fin on the platform. Further, since the width of the rear end surface in the base portion of the fin is secured, the fin is supported easily. Furthermore, since the width of the rear end surface is relatively narrow in the top portion of the fin where the contribution to the aerodynamic performance is large, the chord length of the fin in the top portion is secured easily. Thus, it is possible to relatively reduce the size of the platform, while maintaining the aerodynamic performance of the vortex generator.

(5) In some embodiments, in the above configurations (1) to (4), a rear end portion (14′) of the fin projects outward from an outer edge (11c) of the platform, as viewed from the height direction.

With the above configuration (5), since the rear end portion of the fin projects outward from the outer edge of the platform, the chord length of the fin in the top portion is secured easily. Thus, it is possible to easily reduce the size of the platform, while maintaining the aerodynamic performance of the vortex generator.

(6) In some embodiments, in the above configurations (1) to (5), an inclination angle (α) of the rear end surface with respect to the bottom surface of the platform is not less than 55 degrees and not greater than 65 degrees, in a cross section including a chord of the fin and the height direction.

With the above configuration (6), since the inclination angle of the rear end surface with respect to the bottom surface of the platform is not greater than 65 degrees, in the cross section including the chord of the fin and the height direction, the trailing edge portion of the fin has the shape inclined backward. Therefore, the position of the trailing edge in the top portion of the fin can be shifted backward by a relatively large amount with respect to the position of the trailing edge in the base portion of the fin. Thus, it becomes easy to secure a sufficient chord length of the fin in the top portion. Further, since the above-described inclination angle is not less than 55 degrees, the trailing edge portion of the fin has a shape which is not excessively inclined backward. Therefore, it is possible to obtain the vortex generator provided with the fin having an appropriate size, while inclining the trailing edge portion of the fin. Thus, it is possible to relatively reduce the size of the platform, while maintaining the aerodynamic performance of the vortex generator.

(7) In some embodiments, in the above configurations (1) to (6), the leading edge of the fin is inclined backward as the distance from the bottom surface of the platform increases in the height direction of the fin, in at least a part of a region in the height direction, and an inclination angle of the rear end surface with respect to the bottom surface of the platform is greater than an inclination angle (β) of the leading edge with respect to the bottom surface of the platform, in a cross section including a chord of the fin and the height direction.

With the above configuration (7), the leading edge of the fin is inclined backward as the distance from the bottom surface of the platform increases in the height direction of the fin, in the at least a part of the region in the height direction, and the inclination angle of the rear end surface with respect to the bottom surface of the platform is greater than the inclination angle of the leading edge with respect to the bottom surface of the platform, in the cross section including the chord of the fin and the height direction. Therefore, the cross-sectional area of the fin in the top portion is easily reduced, thereby easily improving the aerodynamic performance. Thus, it is possible to relatively reduce the size of the platform, while maintaining the aerodynamic performance of the vortex generator.

(8) In some embodiments, in the above configurations (1) to (7), the fin includes a leading edge portion (13′) having a curved contour in a cross section orthogonal to the height direction of the fin, and has a shape symmetrical about a chord of the fin.

With the above configuration (8), since the fin includes the leading edge portion having the curved contour in the cross section orthogonal to the height direction of the fin, when the vortex generator is installed on the wind turbine blade, the resistance to the flow of air flowing into the vortex generator is reduced easily. Therefore, the aerodynamic performance of the vortex generator is improved. Further, since the fin has the shape symmetrical about the chord of the fin, the vortex generator is molded easily compared with the case where the fin has a shape asymmetrical about the chord.

(9) In some embodiments, in the above configurations (1) to (8), a blade thickness ratio of the fin is at least 10% and at most 20%.

With the above configuration (9), since the blade thickness ratio of the fin is at least 10% and at most 20%, the vortex generator tends to have good aerodynamic performance.

(10) In some embodiments, in the above configurations (1) to (9), the leading edge of the fin is inclined backward as the distance from the bottom surface of the platform increases in the height direction of the fin, in at least a part of a region in the height direction, and an inclination angle of the leading edge with respect to the bottom surface of the platform is not less than 10 degrees and not greater than 20 degrees, in a cross section including a chord of the fin and the height direction.

With the above configuration (10), since the inclination angle of the leading edge with respect to the bottom surface of the platform is not less than 10 degrees, in the cross section including the chord of the fin and the height direction, it is easy to obtain the fin having an appropriate size, while inclining the leading edge portion of the fin. Further, since the above-described inclination angle is not greater than 20 degrees, it is easy to ensure the aerodynamic performance of the vortex generator. Thus, with the above configuration (10), it is possible to relatively reduce the size of the platform, while maintaining the aerodynamic performance of the vortex generator.

(11) In some embodiments, in the above configuration (10), the leading edge of the fin is inclined backward to a maximum height position of the fin as the distance from the bottom surface of the platform increases in the height direction.

With the above configuration (11), since the leading edge of the fin is inclined backward to the maximum height position of the fin as the distance from the bottom surface of the platform increases in the height direction of the fin, it is easy to ensure the aerodynamic performance of the vortex generator. Thus, it is possible to relatively reduce the size of the platform, while maintaining the aerodynamic performance of the vortex generator.

(12) In some embodiments, in the above configurations (1) to (11), the platform has a circular shape as viewed from the height direction of the fin.

With the above configuration (12), since the platform has the circular shape as viewed from the height direction of the fin, the platform is easily and stably adhered to the surface of the wind turbine blade. Thus, it is possible to suppress separation of the vortex generator from the wind turbine blade.

(13) In some embodiments, in the above configurations (1) to (12), the platform and the fin are formed of a resin.

With the above configuration (13), since the platform and the fin are made of the resin, the vortex generator is molded relatively easily.

(14) A wind turbine blade (1) according to at least one embodiment includes, in the above configurations (1) to (13): a blade body (2); and the vortex generator (10) according to any one of the above (1) to (13) attached to a surface of the blade body.

With the above configuration (14), the rear end surface of the at least one fin has the shape inclined backward as the distance from the bottom surface of the platform increases in the height direction of the fin. Therefore, by shifting the position of the trailing edge in the top portion of the fin, where contribution to aerodynamic performance of the wind turbine blade is large, backward with respect to the position of the trailing edge in the base portion of the fin where the contribution to the aerodynamic performance is relatively small, a sufficient chord length of the fin in the top portion is secured easily. Thus, the size of the platform can be made relatively small relative to the fin, while maintaining the aerodynamic performance of the vortex generator. Therefore, it is possible to obtain the vortex generator mounted with the larger fin while suppressing the increase in size of the platform.

(15) A wind power generating apparatus according to at least one embodiment includes, in the above configuration (14): a wind turbine rotor (42) including a wind turbine blade; and a generator configured to be driven by the wind turbine rotor.

With the above configuration (15), the rear end surface of the at least one fin has the shape inclined backward as the distance from the bottom surface of the platform increases in the height direction of the fin. Therefore, by shifting the position of the trailing edge in the top portion of the fin, where contribution to aerodynamic performance of the wind turbine blade is large, backward with respect to the position of the trailing edge in the base portion of the fin where the contribution to the aerodynamic performance is relatively small, a sufficient chord length of the fin in the top portion is secured easily. Thus, the size of the platform can be made relatively small relative to the fin, while maintaining the aerodynamic performance of the vortex generator. Therefore, it is possible to obtain the vortex generator mounted with the larger fin while suppressing the increase in size of the platform.

Embodiments of the present invention were described in detail above, but the present invention is not limited thereto, and also includes an embodiment obtained by modifying the above-described embodiments and an embodiment obtained by combining these embodiments as appropriate.

As used herein, the expressions “comprising”, “including” or “having” one constitutional element is not an exclusive expression that excludes the presence of other constitutional elements.

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