WO2009026926A1 - Wind turbine blade with submerged boundary layer control means comprisin crossing sub-channels - Google Patents

Wind turbine blade with submerged boundary layer control means comprisin crossing sub-channels Download PDF

Info

Publication number
WO2009026926A1
WO2009026926A1 PCT/DK2008/000310 DK2008000310W WO2009026926A1 WO 2009026926 A1 WO2009026926 A1 WO 2009026926A1 DK 2008000310 W DK2008000310 W DK 2008000310W WO 2009026926 A1 WO2009026926 A1 WO 2009026926A1
Authority
WO
WIPO (PCT)
Prior art keywords
channel
wind turbine
turbine blade
sub
sidewall
Prior art date
Application number
PCT/DK2008/000310
Other languages
French (fr)
Inventor
Peter Fuglsang
Stefano Bove
Original Assignee
Lm Glasfiber A/S
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Lm Glasfiber A/S filed Critical Lm Glasfiber A/S
Priority to DK08784433.8T priority Critical patent/DK2198153T3/en
Priority to CN2008801146427A priority patent/CN101883922B/en
Priority to AT08784433T priority patent/ATE517255T1/en
Priority to EP08784433A priority patent/EP2198153B1/en
Priority to US12/733,410 priority patent/US8550787B2/en
Publication of WO2009026926A1 publication Critical patent/WO2009026926A1/en

Links

Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03DWIND MOTORS
    • F03D1/00Wind motors with rotation axis substantially parallel to the air flow entering the rotor 
    • F03D1/06Rotors
    • F03D1/065Rotors characterised by their construction elements
    • F03D1/0675Rotors characterised by their construction elements of the blades
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B64AIRCRAFT; AVIATION; COSMONAUTICS
    • B64CAEROPLANES; HELICOPTERS
    • B64C2230/00Boundary layer controls
    • B64C2230/26Boundary layer controls by using rib lets or hydrophobic surfaces
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B64AIRCRAFT; AVIATION; COSMONAUTICS
    • B64CAEROPLANES; HELICOPTERS
    • B64C2230/00Boundary layer controls
    • B64C2230/28Boundary layer controls at propeller or rotor blades
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05BINDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00Components
    • F05B2240/10Stators
    • F05B2240/12Fluid guiding means, e.g. vanes
    • F05B2240/122Vortex generators, turbulators, or the like, for mixing
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05BINDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00Components
    • F05B2240/20Rotors
    • F05B2240/30Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05BINDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00Components
    • F05B2240/20Rotors
    • F05B2240/30Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor
    • F05B2240/306Surface measures
    • F05B2240/3062Vortex generators
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05DINDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2240/00Components
    • F05D2240/10Stators
    • F05D2240/12Fluid guiding means, e.g. vanes
    • F05D2240/127Vortex generators, turbulators, or the like, for mixing
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05DINDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2240/00Components
    • F05D2240/20Rotors
    • F05D2240/30Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/70Wind energy
    • Y02E10/72Wind turbines with rotation axis in wind direction
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02TCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T50/00Aeronautics or air transport
    • Y02T50/10Drag reduction

Definitions

  • Wind turbine blade with submerged boundary layer control means comprising crossing sub-channels
  • the present invention relates to a wind turbine blade having a longitudinal direction with a root end and a tip end as well as a chord extending in a transverse direction between a leading edge and a trailing edge, the blade comprising a flow control surface with a suction side and a pressure side.
  • US 4,455,045 describes an alternative means to maintain a flow of a flowing medium attached to the exterior of a flow control member, where an essentially triangular shaped channel is submerged in the surface of the flow control member.
  • the triangular shaped channel has an apex portion facing the flow of the flowing medium, and the channel emerges at the surface of this apex portion.
  • the object is achieved by a number of boundary layer control means being formed in the flow control surface, wherein the boundary layer control means include a channel submerged in the flow control surface with a first end facing towards the leading edge and a second end facing towards the trailing edge of the blade, the channel comprising a bottom surface extending from the first end to the second end, and wherein the channel at the first end comprises a first channel zone comprising a first sub-channel having a first cross-sectional area and a second sub-channel having a second cross-sectional area, the first sub-channel and the second sub-channel crossing each other at a point of crossing.
  • the two crossing sub-channels each direct a separate flow having a first velocity and second velocity direction, respectively, and due to the different velocity directions of these two oncoming flows vortices are generated at the point of crossing.
  • Such vortices will pull the bound- ary layer towards the flow control surface and energises the boundary layer, thereby delaying flow separation or preventing it entirely.
  • This provides for a wind turbine blade, where detachment of the flow can be delayed towards the trailing edge of the blade or be prevented entirely.
  • the point of crossing is located in a part of the first channel zone nearest the trailing edge of the blade, the first sub-channel and the second sub-channel thus converging towards the point of crossing.
  • the channel at the second end comprises a second channel zone having a shape so that vortices generated at the point of crossing can propagate in the flow direction through the second channel zone.
  • the vortices can propagate in the flow direction and thereby energise and re-energise the boundary layer effectively.
  • the second channel zone comprises a first sidewall extending between the flow control surface and the bottom surface, and a second sidewall extending between the flow control surface and the bottom surface, wherein the first sidewall and the second sidewall are substantially parallel, for instance parallel to the transverse direction or the flow direction.
  • the first sidewall and the second sidewall are diverging in the transverse direction or the flow direction.
  • the first channel zone and the second channel zone are separated by a sharp edge. That is, one sidewall of the first sub- channel continues over to the first sidewall of the second channel zone, and one sidewall of the second sub-channel continues over to the second sidewall of the second channel zone, the transverse distance between these sidewalls varying discontinuously in the flow direction.
  • the first cross-sectional area is substantially the same as the second cross-sectional area. According to another embodiment of the sub-channels, the first cross-sectional area is different from the second cross-sectional area. This enhances the shear stress between the two oncoming flows at the point of crossing, thereby more effectively producing flow vortices.
  • the second channel zone comprises a first additional sub-channel and/or a second additional sub-channel.
  • These two additional sub-channels can also have different cross-sectional areas and can be utilised for producing new sets of vortices downstream from the point of crossing.
  • the first cross-sectional area and/or the second cross-sectional area is decreasing in the flow direction.
  • This provides for a simple solution for accelerating the flows towards the point of crossing, thereby being able to produce even stronger vortices.
  • This can be achieved by letting sidewalls of a sub-channel being diverging in the flow direction and/or by letting the height of these sidewalls being decreasing in the flow direction.
  • the sidewalls of the sub-channels as well as the first and the second sidewalls form sidewall edges with the flow control surface, where these edges are relatively sharp, i.e. the sidewalls and the flow control surface form angles of about 90 degrees.
  • the edges need not be about 90 degrees for the vortex generating channels to function intentionally.
  • the first sidewall and the second sidewall may also cross-sectionally diverge, so that the first sidewall edge and the second sidewall edge form angles of more than 90 degrees.
  • the sidewall edges may extend beyond the flow control surface. This can for instance be implemented by forming a lip above the channel. Thereby, the channel does not have a sharp edge, thereby making it easier to mould the object with the flow control surface.
  • the bottom surface can also be either convex or concave in the flow direction.
  • the bottom surface can be rounded or substantially flat, when seen in the cross-section of the channel.
  • the channel can also be provided with an inlet arranged before the first channel zone and/or be provided with an outlet arranged after the second channel zone.
  • the channel can emerge at the flow control surface at the end of the inlet or at the end of the first channel zone, as well as emerge at the end of the second channel zone or at the end of the outlet.
  • the sidewalls can be substantially parallel to the flow direction within the inlet and the outlet of the channel.
  • the channel can also have a small discontinuity, i.e. the height of the channel or sidewalls may decrease stepwise.
  • the first sub-channel and the second sub-channel cross each other at the point of crossing with an angle between 10 and 100 degrees, or between 20 and 95 degrees, or between 25 and 90 degrees.
  • the number of means to maintain attached flow is arranged on the suction side of the blade.
  • the means, i.e. the vortex generating channels, are typically ar- ranged in an array in the spanwise or longitudinal direction of the blade.
  • the means for maintaining an attached flow can also be cascaded in the chordwise or transverse direction of the blade, i.e. in the direction of the chord.
  • the wind turbine blade is mounted to a rotor hub.
  • the blade is typically di- vided into a root region with a substantially circular profile closest to the hub, an airfoil region with a lift generating profile furthest away from the hub, and a transition region between the root region and the airfoil region, the profile of the transition region gradually changing in the radial direction from the circular profile of the root region to the lift generating profile of the airfoil region.
  • the means for maintaining an attached flow are positioned mainly on the profiled part of the blade, i.e. the airfoil region, and optionally the transition region of the blade.
  • the chordwise position of the means for maintaining attached flow can be between 10% and 80% of the chord as seen from the leading edge. Alternatively, they are posi- tioned within a region extending between 20% and 70% of the chord as seen from the leading edge.
  • the means are utilised to delay separation, where a forward position, i.e. close to the leading edge, is used to delay stall, and a backward position, i.e. further away from the leading edge, is used to increase efficiency.
  • the height of the channels is between 0.1% and 5% of the chord length, or alternatively between 0.2% and 3.5%, or alternatively between 0.5% and 2%. These heights effectively produce vortices of the desired size.
  • the mentioned channel height is preferably located at the position, where the vortices are generated, i.e. immediately after the start of the second channel zone.
  • the vortices preferably correspond to the height of the channels and/or the boundary layer.
  • the wind turbine blade is constructed as a shell member of fibre-reinforced polymer.
  • the chan- nels can be formed in the surface of the wind turbine blade during the moulding process, either by forming protrusions in a negative mould, or by moulding strips of a dissolvable material in the surface of the wind turbine blade, which after moulding is dissolved in order to form the vortex generating channels.
  • the channels can also be formed in the surface of the blade after moulding by for instance milling.
  • the invention also provides a wind turbine rotor comprising a number, preferably two or three, of the previously mentioned wind turbine blades.
  • a wind turbine comprising such a wind turbine rotor or a number of such wind turbine blades is provided.
  • the various embodiments of the boundary layer control means of course also may be used to other flow control members, i.e.
  • a flow control member having a flow control surface
  • the flow control member is provided with boundary layer control means for maintaining a flow of a flowing medium attached to the exterior of the flow control member, the flow having a flow direction
  • the boundary layer control means include: a channel submerged in the flow control surface, the channel having: a first end facing the flow of the flowing medium, a second end positioned downstream in the flow of the flowing medium from the first end, and a bottom surface extending from the first end to the second end, wherein the channel at the first end comprises a first channel zone comprising a first sub-channel having a first cross-sectional area and a second sub-channel having a second cross-sectional area, the first sub-channel and the second sub-channel crossing each other at a point of crossing.
  • Fig. 1 shows a wind turbine
  • Fig. 2 a schematic view of a wind turbine blade according to the invention
  • Fig. 3 a first embodiment of a boundary layer control means
  • Fig. 4 a second embodiment of a boundary layer control means
  • Fig. 5 a third embodiment of a boundary layer control means
  • Fig. 6 a fourth embodiment of a boundary layer control means
  • Fig. 7 a fifth embodiment of a boundary layer control means
  • Fig. 8 a cross-sectional view of a channel being part of the boundary layer control means
  • Fig. 9 a second cross-sectional view of a channel being part of the boundary layer control means
  • Fig. 10 a sixth embodiment of a boundary layer control means
  • Fig. 11 a seventh embodiment of a boundary layer control means.
  • Fig. 1 illustrates a conventional modern 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.
  • Fig. 2 shows a schematic view of an embodiment of a wind turbine according to the invention.
  • the wind turbine blade 10 comprises a number of boundary layer control means 40 according to the invention, the means being formed as submerged channels in the surface of a suction side of the wind turbine blade 10.
  • 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 region area 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.
  • 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 has a substantially circular or elliptical cross-section, which reduces loads from wind gusts and makes it easier and safer to mount the blade 10 to the hub.
  • the diameter of the root region 30 is typically constant along the entire root area 30.
  • the transition region 32 has a shape gradually changing from the circular shape of the root region 30 to the airfoil profile of the airfoil region 34, optionally with an intermediate elliptical shape.
  • the width of the transition region 32 typically increases substantially linearly with increasing distance L from the hub.
  • the airfoil region 34 has an airfoil profile 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 L from the hub. It should be noted that the chords of different sec- tions of the blade do not necessarily 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.
  • the boundary layer control means 40 are arranged in arrays in the spanwise or longitudinal direction L of the blade.
  • the sizes of the individual channels are grossly exaggerated in the figure and will normally be much smaller compared to the wind turbine blade.
  • the wind turbine blade can comprise a much higher number of boundary layer control means 40 in the longitudinal direction L of the wind turbine blade 10.
  • the boundary layer control means 40 are utilised to generate vortices of turbulent flow within the channel of the boundary layer control means 40, the vortices pulling a boundary layer of a flowing medium flowing across the surface of the wind turbine blade 10 from the leading edge 18 to the trailing edge 20 towards the surface of the wind turbine blade, thus preventing the boundary layer from separating from the exterior of the wind turbine blade 10.
  • the boundary layer control means 40 may be cascaded in the chord-wise direction (or equivalently the transverse direction) of the blade 10 in order to continuously generate vortices in the chord-wise direction L of the blade 10.
  • the boundary layer control means 40 can be of any of the embodiments shown in Figs. 3-11 or combinations thereof.
  • Fig. 3 shows a schematic view of a first embodiment of a boundary layer control means 100 for maintaining flow of a flowing medium attached to the exterior of a flow control member, such as a wind turbine blade, having a flow control surface 112.
  • the boundary layer control means 100 comprises a channel, which is submerged in the flow control surface 112.
  • the channel extends in the direction of a free flow having a flow direc- tion, which is depicted with arrows in the figure.
  • the channel comprises a first end 102 facing the free flow and a second end 104 positioned downstream in the flow of the flowing medium from the first end 102.
  • the channel further comprises a bottom surface 106 extending from the first end 102 to the second end 104.
  • the channel comprises a first channel zone 122 at the first end 102 of the channel, and a second channel zone 124 at the second end 104 of the channel.
  • the first channel zone 122 comprises a first sub-channel 118 and a second sub-channel, both of which are adapted to guide separate flows.
  • the first sub-channel 118 and the second subchannel and thereby also the separate guided flows cross each other at a point of crossing at a boundary between the first channel zone 122 and the second channel zone 124. Since the two separate flows have different velocity directions at the point of crossing, a set of vortices 132 is generated, which propagates through the second channel zone 124 in the flow direction.
  • the second channel zone comprises a first sidewall 108 extending between the flow control surface 112 and the bottom surface 106, as well as a second sidewall 110 extending between the flow control surface 112 and the bottom surface 106.
  • the first sidewall 108 and the second sidewall 110 are diverging in the flow direction.
  • the generated set of vortices 132 can freely propagate through the second channel zone 124.
  • the set of vortices 132 pulls the boundary layer of a the flowing medium towards the flow control surface 112, which ensures that the boundary layer separates further downstream of the flow or is prevented entirely. If the flow control member is a wind turbine blade, this means that the overall lift of the blade can be improved.
  • the height of the vortices should generally correspond to the height of the channel, i.e. the distance between the bottom surface 106 and the flow control surface 112, in order to efficiently energise the boundary layer and keep the flow attached to the exterior of the flow control member.
  • Fig. 4 shows a second embodiment of a boundary layer control means 200.
  • the second embodiment differs from the first embodiment in that the first sub-channel 218 has a first cross-sectional area and the second sub-channel 220 has a second cross- sectional area, where the first cross-sectional area differs from the second cross- sectional area. This enhances the shear stress between the two oncoming flows at the point of crossing, thereby more effectively producing flow vortices.
  • Fig. 5 shows a third embodiment of a boundary layer control means 300, where like numerals refer to like parts of the second embodiment. Therefore, only the differences between the third embodiment and the second embodiment are described.
  • This embodiment differs from the second embodiment in that the first sub-channel 318 contin- ues into the second channel zone 324. This sub-channel can then cross other subchannels in order to generate new sets of vortices in order to further ensure that the boundary layer separates further downstream.
  • Fig. 6 shows a fourth embodiment of a boundary layer control means 400, where like numerals refer to like parts of the second embodiment. Therefore, only the differences between the fourth embodiment and the second embodiment are described.
  • This embodiment differs from the second embodiment in that the first sidewall 408 and the second sidewall 410 are substantially parallel to the flow direction of the free flow in the second channel zone 424.
  • Fig. 7 shows a fifth embodiment of a boundary layer control means 500, where like numerals refer to like parts of the second embodiment. Therefore, only the differences between the fifth embodiment and the second embodiment are described.
  • This em- bodiment differs from the second embodiment in that the cross-sectional areas of the first sub-channel 518 and the second sub-channel 520 are decreasing in the flow direction. Thereby, the separate flows through the sub-channels are accelerated towards the point of crossing, thereby producing stronger vortices.
  • sidewall edges formed between sidewalls and the flow control surface are depicted as having an angle of about 90 degrees.
  • the sidewall edges can also protrude beyond the flow control surface and form lips 60, 62 above the channel as shown in Fig. 8, which depicts a cross-section of a channel according to the invention.
  • a first bottom edge 64 and a second bottom edge 66 formed between the first sidewall and the bottom surface and the second sidewall and the bottom surface, respectively, can be rounded.
  • the channel does not have any sharp edge, thereby making it easier to mould the object with the flow control surface.
  • the bottom surface of the channel can also be even more rounded as depicted in Fig. 9.
  • Fig. 10 shows a sixth embodiment of a boundary layer control means 600, wherein like numerals refer to like parts of the first embodiment.
  • This embodiment differs from the first embodiment in that the height of the sidewalls of the first sub-channel 608 and the second sub-channel 610 are decreasing towards the first end 602 so that the sub- channels 618, 620 emerge at the flow control surface 612 at the first end 602. Furthermore, the height of the first sidewall 608 and the second sidewall 610 is decreasing to- wards the second end 604 so that the channel emerges at the flow control surface 612 at the second end 604.
  • the channels can also be slightly curved or bent so that they cross each other with a lower angle of attack, and where the vortices are generated by flow separating from the first sidewail 608 and the second sidewall 610.
  • Fig. 11 shows a seventh embodiment of a boundary layer control means 700, wherein like numerals refer to like parts of the first embodiment.
  • This embodiment differs from the first embodiment in that the first sub-channel 718 and the second sub-channel 720 are provided with inlets 742 having sidewall, which are substantially parallel to the flow direction of the free flow, which is illustrated with arrows.
  • the height of the sidewalls is in the inlet region 742 decreasing towards the first end 702 so that the inlets 742 of the sub-channels 718, 720 emerge at the flow control surface 712 at the first end 702.
  • Fur- thermore the channel is provided with an outlet region 742 after the second channel zone, where the first sidewall 708 and the second sidewall 710 are substantially parallel to the flow direction of the free flow.
  • the height of the sidewalls is in the outlet region 744 decreasing towards the second end 704 so that the channel emerges at the flow control surface 712 at the second end 704.
  • x refers to a particular embodiment.
  • 402 refers to the first end of the fourth embodiment.

Abstract

A wind turbine blade having a longitudinal direction with a root end and a tip end as well as a chord extending in a transverse direction between a leading edge and a trail- ing edge is described. The blade comprises a flow control surface with a suction side and a pressure side. A number of boundary layer control means is formed in the flow control surface. The boundary layer control means include a channel submerged in the flow control surface with a first end facing towards the leading edge and a second end facing towards the trailing edge of the blade. The channel further comprises a bottom surface extending from the first end to the second end. The channel at the first end comprises a first channel zone comprising a first sub-channel having a first cross- sectional area and a second sub-channel having a second cross-sectional area, the first sub-channel and the second sub-channel crossing each other at a point of crossing.

Description

Title: Wind turbine blade with submerged boundary layer control means comprising crossing sub-channels
Technical Field
The present invention relates to a wind turbine blade having a longitudinal direction with a root end and a tip end as well as a chord extending in a transverse direction between a leading edge and a trailing edge, the blade comprising a flow control surface with a suction side and a pressure side.
Background
There are many situations, where it is desirable to provide a method of delaying or preventing flow separation between a flowing medium and a flow control surface in re- gions, where the boundary layer of the flow medium due to the profile of the flow control surface is subjected to pressure gradients, which are sufficient to cause flow separation.
When a viscous fluid passes over a wind turbine blade towards the trailing edge, the fluid flows from a region with low static pressure to a region with high static pressure, in the process being subjected to an adverse pressure gradient. This results in forces, which tend to retard the boundary layer, which can be strong enough to arrest or reverse the flow, which can cause the fluid to separate and behave in a non-predictable manner. This in turn causes an increase in drag due to the cross-sectional area of separated flow in the wake of the flow control medium, which in turn reduces the lift of the wind turbine blade and even may cause the blade to stall.
It is well-known to delay or prevent flow separation by mixing free flow with the boundary layer by use of vortex generators protruding from the flow control surface, i.e. from the surface of the wind turbine blade. There is a large number of different vortex generator types, such as of the vane type, see for instance WO 01/16482, or vortex generators formed as delta shaped protrusions as shown in WO 00/15961. However, all of these vortex generators are encumbered with a drawback of relatively high drag. Furthermore, these vortex generators, which are usually mounted on the surface of the wind turbine blade after production of the blade, have a tendency to break off during transport, which may seriously impair the functionality of the blade. US 4,455,045 describes an alternative means to maintain a flow of a flowing medium attached to the exterior of a flow control member, where an essentially triangular shaped channel is submerged in the surface of the flow control member. The triangular shaped channel has an apex portion facing the flow of the flowing medium, and the channel emerges at the surface of this apex portion.
Disclosure of the Invention
It is an object of the invention to provide a new blade for a rotor of a wind turbine, which overcomes or ameliorates at least one of the disadvantages of the prior art or which provides a useful alternative.
According to a first aspect of the invention, the object is achieved by a number of boundary layer control means being formed in the flow control surface, wherein the boundary layer control means include a channel submerged in the flow control surface with a first end facing towards the leading edge and a second end facing towards the trailing edge of the blade, the channel comprising a bottom surface extending from the first end to the second end, and wherein the channel at the first end comprises a first channel zone comprising a first sub-channel having a first cross-sectional area and a second sub-channel having a second cross-sectional area, the first sub-channel and the second sub-channel crossing each other at a point of crossing. The two crossing sub-channels each direct a separate flow having a first velocity and second velocity direction, respectively, and due to the different velocity directions of these two oncoming flows vortices are generated at the point of crossing. Such vortices will pull the bound- ary layer towards the flow control surface and energises the boundary layer, thereby delaying flow separation or preventing it entirely. This provides for a wind turbine blade, where detachment of the flow can be delayed towards the trailing edge of the blade or be prevented entirely. Thus, the overall lift and efficiency of the wind turbine blade can be increased. The point of crossing is located in a part of the first channel zone nearest the trailing edge of the blade, the first sub-channel and the second sub-channel thus converging towards the point of crossing.
According to a first embodiment, the channel at the second end comprises a second channel zone having a shape so that vortices generated at the point of crossing can propagate in the flow direction through the second channel zone. Thereby, the vortices can propagate in the flow direction and thereby energise and re-energise the boundary layer effectively.
In one embodiment according to the invention, the second channel zone comprises a first sidewall extending between the flow control surface and the bottom surface, and a second sidewall extending between the flow control surface and the bottom surface, wherein the first sidewall and the second sidewall are substantially parallel, for instance parallel to the transverse direction or the flow direction. Alternatively, the first sidewall and the second sidewall are diverging in the transverse direction or the flow direction. These two solutions provide simple embodiments, where the vortices can propagate in the flow direction.
According to one embodiment of the blade, the first channel zone and the second channel zone are separated by a sharp edge. That is, one sidewall of the first sub- channel continues over to the first sidewall of the second channel zone, and one sidewall of the second sub-channel continues over to the second sidewall of the second channel zone, the transverse distance between these sidewalls varying discontinuously in the flow direction.
According to a first embodiment of the sub-channels, the first cross-sectional area is substantially the same as the second cross-sectional area. According to another embodiment of the sub-channels, the first cross-sectional area is different from the second cross-sectional area. This enhances the shear stress between the two oncoming flows at the point of crossing, thereby more effectively producing flow vortices.
In one embodiment according to the invention, the second channel zone comprises a first additional sub-channel and/or a second additional sub-channel. These two additional sub-channels can also have different cross-sectional areas and can be utilised for producing new sets of vortices downstream from the point of crossing.
In another embodiment according to the invention, the first cross-sectional area and/or the second cross-sectional area is decreasing in the flow direction. This provides for a simple solution for accelerating the flows towards the point of crossing, thereby being able to produce even stronger vortices. This can be achieved by letting sidewalls of a sub-channel being diverging in the flow direction and/or by letting the height of these sidewalls being decreasing in the flow direction. According to advantageous embodiments, the sidewalls of the sub-channels as well as the first and the second sidewalls form sidewall edges with the flow control surface, where these edges are relatively sharp, i.e. the sidewalls and the flow control surface form angles of about 90 degrees. However, the edges need not be about 90 degrees for the vortex generating channels to function intentionally. Thus, the first sidewall and the second sidewall may also cross-sectionally diverge, so that the first sidewall edge and the second sidewall edge form angles of more than 90 degrees. Alternatively, the sidewall edges may extend beyond the flow control surface. This can for instance be implemented by forming a lip above the channel. Thereby, the channel does not have a sharp edge, thereby making it easier to mould the object with the flow control surface.
The bottom surface can also be either convex or concave in the flow direction. The bottom surface can be rounded or substantially flat, when seen in the cross-section of the channel.
The channel can also be provided with an inlet arranged before the first channel zone and/or be provided with an outlet arranged after the second channel zone. Thus, the channel can emerge at the flow control surface at the end of the inlet or at the end of the first channel zone, as well as emerge at the end of the second channel zone or at the end of the outlet. The sidewalls can be substantially parallel to the flow direction within the inlet and the outlet of the channel. The channel can also have a small discontinuity, i.e. the height of the channel or sidewalls may decrease stepwise.
According to advantageous embodiments, the first sub-channel and the second sub- channel cross each other at the point of crossing with an angle between 10 and 100 degrees, or between 20 and 95 degrees, or between 25 and 90 degrees.
Preferably, the number of means to maintain attached flow is arranged on the suction side of the blade. The means, i.e. the vortex generating channels, are typically ar- ranged in an array in the spanwise or longitudinal direction of the blade. The means for maintaining an attached flow can also be cascaded in the chordwise or transverse direction of the blade, i.e. in the direction of the chord.
During use, the wind turbine blade is mounted to a rotor hub. The blade is typically di- vided into a root region with a substantially circular profile closest to the hub, an airfoil region with a lift generating profile furthest away from the hub, and a transition region between the root region and the airfoil region, the profile of the transition region gradually changing in the radial direction from the circular profile of the root region to the lift generating profile of the airfoil region.
The means for maintaining an attached flow are positioned mainly on the profiled part of the blade, i.e. the airfoil region, and optionally the transition region of the blade.
The chordwise position of the means for maintaining attached flow can be between 10% and 80% of the chord as seen from the leading edge. Alternatively, they are posi- tioned within a region extending between 20% and 70% of the chord as seen from the leading edge. In general the means are utilised to delay separation, where a forward position, i.e. close to the leading edge, is used to delay stall, and a backward position, i.e. further away from the leading edge, is used to increase efficiency.
According to an advantageous embodiment of the wind turbine blade, the height of the channels is between 0.1% and 5% of the chord length, or alternatively between 0.2% and 3.5%, or alternatively between 0.5% and 2%. These heights effectively produce vortices of the desired size. The mentioned channel height is preferably located at the position, where the vortices are generated, i.e. immediately after the start of the second channel zone. In general, the vortices preferably correspond to the height of the channels and/or the boundary layer.
According to a preferred embodiment of the blade according to the invention, the wind turbine blade is constructed as a shell member of fibre-reinforced polymer. The chan- nels can be formed in the surface of the wind turbine blade during the moulding process, either by forming protrusions in a negative mould, or by moulding strips of a dissolvable material in the surface of the wind turbine blade, which after moulding is dissolved in order to form the vortex generating channels. The channels can also be formed in the surface of the blade after moulding by for instance milling.
According to a second aspect, the invention also provides a wind turbine rotor comprising a number, preferably two or three, of the previously mentioned wind turbine blades. According to a third aspect, a wind turbine comprising such a wind turbine rotor or a number of such wind turbine blades is provided. The various embodiments of the boundary layer control means of course also may be used to other flow control members, i.e. a flow control member having a flow control surface, wherein the flow control member is provided with boundary layer control means for maintaining a flow of a flowing medium attached to the exterior of the flow control member, the flow having a flow direction, wherein the boundary layer control means include: a channel submerged in the flow control surface, the channel having: a first end facing the flow of the flowing medium, a second end positioned downstream in the flow of the flowing medium from the first end, and a bottom surface extending from the first end to the second end, wherein the channel at the first end comprises a first channel zone comprising a first sub-channel having a first cross-sectional area and a second sub-channel having a second cross-sectional area, the first sub-channel and the second sub-channel crossing each other at a point of crossing.
Brief Description of the Drawings
The invention is explained in detail below with reference to the drawings, in which
Fig. 1 shows a wind turbine,
Fig. 2 a schematic view of a wind turbine blade according to the invention,
Fig. 3 a first embodiment of a boundary layer control means,
Fig. 4 a second embodiment of a boundary layer control means,
Fig. 5 a third embodiment of a boundary layer control means,
Fig. 6 a fourth embodiment of a boundary layer control means,
Fig. 7 a fifth embodiment of a boundary layer control means,
Fig. 8 a cross-sectional view of a channel being part of the boundary layer control means,
Fig. 9 a second cross-sectional view of a channel being part of the boundary layer control means, Fig. 10 a sixth embodiment of a boundary layer control means, and
Fig. 11 a seventh embodiment of a boundary layer control means.
Detailed description of the Invention
Fig. 1 illustrates a conventional modern 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.
Fig. 2 shows a schematic view of an embodiment of a wind turbine according to the invention. The wind turbine blade 10 comprises a number of boundary layer control means 40 according to the invention, the means being formed as submerged channels in the surface of a suction side of the wind turbine blade 10.
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 region area 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.
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 has a substantially circular or elliptical cross-section, which reduces loads from wind gusts and makes it easier and safer to mount the blade 10 to the hub. The diameter of the root region 30 is typically constant along the entire root area 30. The transition region 32 has a shape gradually changing from the circular shape of the root region 30 to the airfoil profile of the airfoil region 34, optionally with an intermediate elliptical shape. The width of the transition region 32 typically increases substantially linearly with increasing distance L from the hub.
The airfoil region 34 has an airfoil profile 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 L from the hub. It should be noted that the chords of different sec- tions of the blade do not necessarily 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.
The boundary layer control means 40 are arranged in arrays in the spanwise or longitudinal direction L of the blade. The sizes of the individual channels are grossly exaggerated in the figure and will normally be much smaller compared to the wind turbine blade. Thus, the wind turbine blade can comprise a much higher number of boundary layer control means 40 in the longitudinal direction L of the wind turbine blade 10.
The boundary layer control means 40 are utilised to generate vortices of turbulent flow within the channel of the boundary layer control means 40, the vortices pulling a boundary layer of a flowing medium flowing across the surface of the wind turbine blade 10 from the leading edge 18 to the trailing edge 20 towards the surface of the wind turbine blade, thus preventing the boundary layer from separating from the exterior of the wind turbine blade 10. The boundary layer control means 40 may be cascaded in the chord-wise direction (or equivalently the transverse direction) of the blade 10 in order to continuously generate vortices in the chord-wise direction L of the blade 10.
The boundary layer control means 40 can be of any of the embodiments shown in Figs. 3-11 or combinations thereof.
Fig. 3 shows a schematic view of a first embodiment of a boundary layer control means 100 for maintaining flow of a flowing medium attached to the exterior of a flow control member, such as a wind turbine blade, having a flow control surface 112. The boundary layer control means 100 comprises a channel, which is submerged in the flow control surface 112. The channel extends in the direction of a free flow having a flow direc- tion, which is depicted with arrows in the figure. The channel comprises a first end 102 facing the free flow and a second end 104 positioned downstream in the flow of the flowing medium from the first end 102. The channel further comprises a bottom surface 106 extending from the first end 102 to the second end 104.
The channel comprises a first channel zone 122 at the first end 102 of the channel, and a second channel zone 124 at the second end 104 of the channel. The first channel zone 122 comprises a first sub-channel 118 and a second sub-channel, both of which are adapted to guide separate flows. The first sub-channel 118 and the second subchannel and thereby also the separate guided flows cross each other at a point of crossing at a boundary between the first channel zone 122 and the second channel zone 124. Since the two separate flows have different velocity directions at the point of crossing, a set of vortices 132 is generated, which propagates through the second channel zone 124 in the flow direction.
The second channel zone comprises a first sidewall 108 extending between the flow control surface 112 and the bottom surface 106, as well as a second sidewall 110 extending between the flow control surface 112 and the bottom surface 106. The first sidewall 108 and the second sidewall 110 are diverging in the flow direction. Thus, the generated set of vortices 132 can freely propagate through the second channel zone 124. The set of vortices 132 pulls the boundary layer of a the flowing medium towards the flow control surface 112, which ensures that the boundary layer separates further downstream of the flow or is prevented entirely. If the flow control member is a wind turbine blade, this means that the overall lift of the blade can be improved.
The height of the vortices should generally correspond to the height of the channel, i.e. the distance between the bottom surface 106 and the flow control surface 112, in order to efficiently energise the boundary layer and keep the flow attached to the exterior of the flow control member.
Fig. 4 shows a second embodiment of a boundary layer control means 200. In the fig- ure like numerals refer to like parts of the first embodiment. Therefore, only the differences between the first embodiment and the second embodiment are described. The second embodiment differs from the first embodiment in that the first sub-channel 218 has a first cross-sectional area and the second sub-channel 220 has a second cross- sectional area, where the first cross-sectional area differs from the second cross- sectional area. This enhances the shear stress between the two oncoming flows at the point of crossing, thereby more effectively producing flow vortices.
Fig. 5 shows a third embodiment of a boundary layer control means 300, where like numerals refer to like parts of the second embodiment. Therefore, only the differences between the third embodiment and the second embodiment are described. This embodiment differs from the second embodiment in that the first sub-channel 318 contin- ues into the second channel zone 324. This sub-channel can then cross other subchannels in order to generate new sets of vortices in order to further ensure that the boundary layer separates further downstream.
Fig. 6 shows a fourth embodiment of a boundary layer control means 400, where like numerals refer to like parts of the second embodiment. Therefore, only the differences between the fourth embodiment and the second embodiment are described. This embodiment differs from the second embodiment in that the first sidewall 408 and the second sidewall 410 are substantially parallel to the flow direction of the free flow in the second channel zone 424.
Fig. 7 shows a fifth embodiment of a boundary layer control means 500, where like numerals refer to like parts of the second embodiment. Therefore, only the differences between the fifth embodiment and the second embodiment are described. This em- bodiment differs from the second embodiment in that the cross-sectional areas of the first sub-channel 518 and the second sub-channel 520 are decreasing in the flow direction. Thereby, the separate flows through the sub-channels are accelerated towards the point of crossing, thereby producing stronger vortices.
In the embodiments shown in Figs. 3-7 sidewall edges formed between sidewalls and the flow control surface are depicted as having an angle of about 90 degrees. However, the sidewall edges can also protrude beyond the flow control surface and form lips 60, 62 above the channel as shown in Fig. 8, which depicts a cross-section of a channel according to the invention. Furthermore, a first bottom edge 64 and a second bottom edge 66 formed between the first sidewall and the bottom surface and the second sidewall and the bottom surface, respectively, can be rounded. Thus, the channel does not have any sharp edge, thereby making it easier to mould the object with the flow control surface. The bottom surface of the channel can also be even more rounded as depicted in Fig. 9.
Fig. 10 shows a sixth embodiment of a boundary layer control means 600, wherein like numerals refer to like parts of the first embodiment. This embodiment differs from the first embodiment in that the height of the sidewalls of the first sub-channel 608 and the second sub-channel 610 are decreasing towards the first end 602 so that the sub- channels 618, 620 emerge at the flow control surface 612 at the first end 602. Furthermore, the height of the first sidewall 608 and the second sidewall 610 is decreasing to- wards the second end 604 so that the channel emerges at the flow control surface 612 at the second end 604.
The channels can also be slightly curved or bent so that they cross each other with a lower angle of attack, and where the vortices are generated by flow separating from the first sidewail 608 and the second sidewall 610.
Fig. 11 shows a seventh embodiment of a boundary layer control means 700, wherein like numerals refer to like parts of the first embodiment. This embodiment differs from the first embodiment in that the first sub-channel 718 and the second sub-channel 720 are provided with inlets 742 having sidewall, which are substantially parallel to the flow direction of the free flow, which is illustrated with arrows. The height of the sidewalls is in the inlet region 742 decreasing towards the first end 702 so that the inlets 742 of the sub-channels 718, 720 emerge at the flow control surface 712 at the first end 702. Fur- thermore, the channel is provided with an outlet region 742 after the second channel zone, where the first sidewall 708 and the second sidewall 710 are substantially parallel to the flow direction of the free flow. The height of the sidewalls is in the outlet region 744 decreasing towards the second end 704 so that the channel emerges at the flow control surface 712 at the second end 704.
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. For instance can the second channel zones of adjacent means merge into a common channel zone.
List of reference numerals
In the numerals, x refers to a particular embodiment. Thus, for instance 402 refers to the first end of the fourth embodiment.
2 wind turbine
4 tower
6 nacelle
8 hub
10 blade
14 blade tip
16 blade root
18 leading edge
20 trailing edge
30 root region
32 transition region
34 airfoil region
40 boundary layer control means
60, 62 lips
64 first bottom edge
66 second bottom edge xOO boundary layer control means xO2 first end χO4 second end xO6 bottom surface xO8 first sidewall x10 second sidewall x12 flow control surface x18 first sub-channel x20 second sub-channel x22 first channel zone x24 second channel zone x32 set of vortices x42 inlet x44 outlet

Claims

Claims
1. A wind turbine blade (10) having a longitudinal direction with a root end (16) and a tip end (14) as well as a chord extending in a transverse direction between a leading edge (18) and a trailing edge (20), the blade (10) comprising a flow control surface with a suction side and a pressure side, characterised in that a number of boundary layer control means (40) is formed in the flow control surface, wherein the boundary layer control means (40) include a channel submerged in the flow control surface (112; 212; 312; 412; 512; 612; 712) with a first end facing towards the leading edge (18) and a second end facing towards the trailing edge (20) of the blade (10), the channel comprising a bottom surface (106; 206; 306; 406; 506) extending from the first end (102; 202; 302; 402; 502; 602; 702) to the second end (104; 204; 304; 404; 504; 604; 704), and wherein the channel at the first end (102; 202; 302; 402; 502; 602; 702) comprises a first channel zone (122; 222; 322; 422; 522) comprising a first sub-channel (118; 218; 318; 418; 518; 618; 718) having a first cross-sectional area and a second sub-channel (120; 220; 320; 420; 520; 620; 720) having a second cross-sectional area, the first subchannel (118; 218; 318; 418; 518; 618; 718) and the second sub-channel (120; 220; 320; 420; 520; 620; 720) crossing each other at a point of crossing.
2. A wind turbine blade according to claim 1 , wherein the number of boundary layer control means (40) is arranged on the suction side of the blade.
3. A wind turbine blade according to claim 1 or 2, wherein the channel at the second end (104; 204; 304; 404; 504; 604; 704) comprises a second channel zone (124; 224; 324; 424; 524) having a shape so that vortices generated at the point of crossing can propagate in the transverse direction through the second channel zone (124; 224; 324; 424; 524).
4. A wind turbine blade according to any of the preceding claims, wherein the first sub-channel and the second sub-channel cross each other at the point of crossing with an angle between 10 and 100 degrees, or between 20 and 95 degrees, or between 25 and 90 degrees.
5. A wind turbine blade according to any of the preceding claims, wherein the sec- ond channel zone (124; 224; 324; 424; 524) comprises a first sidewall (108; 208; 308;
408; 508; 608; 708) extending between the flow control surface (112; 212; 312; 412; 512; 612; 712) and the bottom surface (106; 206; 306; 406; 506), and a second side- wall (110; 210; 310; 410; 510; 610; 710) extending between the flow control surface (112; 212; 312; 412; 512; 612; 712) and the bottom surface (106; 206; 306; 406; 506), and wherein the first sidewall (108; 208; 308; 408; 508; 608; 708) and the second sidewall (110; 210; 310; 410; 510; 610; 710) are substantially parallel.
6. A wind turbine blade according to any of claims 1-4, wherein the second channel zone (124; 224; 324; 424; 524) comprises a first sidewall (108; 208; 308; 408; 508; 608; 708) extending between the flow control surface (112; 212; 312; 412; 512; 612; 712) and the bottom surface (106; 206; 306; 406; 506), and a second sidewall (110; 210; 310; 410; 510; 610; 710) extending between the flow control surface (112; 212; 312; 412; 512; 612; 712) and the bottom surface (106; 206; 306; 406; 506), and wherein the first sidewall (108; 208; 308; 408; 508; 608; 708) and the second sidewall (110; 210; 310; 410; 510; 610; 710) are diverging towards the trailing edge (18) of the blade.
7. A wind turbine blade according to claim 5 or 6, wherein the first sidewall (108; 208; 308; 408; 508; 608; 708) and the second side wall is continuously connected to a sidewall of the first sub-channel (118; 218; 318; 418; 518; 618; 718) and a sidewall of the second sub-channel (120; 220; 320; 420; 520; 620; 720), respectively.
8. A wind turbine blade according to any of the preceding claims, wherein the first channel zone (122; 222; 322; 422; 522) and the second channel zone (124; 224; 324; 424; 524) are separated by a sharp edge.
9. A wind turbine blade according to any of the preceding claims, wherein the first cross-sectional area is substantially the same as the second cross-sectional area.
10. A wind turbine blade according to any of claims 1-8, wherein the first cross- sectional area is different from the second cross-sectional area.
11. A wind turbine blade according to one of the preceding claims, wherein the second channel zone comprises a first additional sub-channel and/or a second additional sub-channel.
12. A wind turbine blade according to one of the preceding claims, wherein the first cross-sectional area and/or the second cross-sectional area is decreasing towards the trailing edge (18) of the blade.
13. A wind turbine blade according to any of the preceding claims, wherein the height of the channels is between 0.1% and 5% of the chord length, or alternatively between 0.2% and 3.5%, or alternatively between 0.5% and 2%.
14. A wind turbine blade according to any of the preceding claims, wherein the blade is divided into:
- a root region (30) with a substantially circular or elliptical profile closest to the root end,
- an airfoil region (34) with a lift generating profile furthest away from the root end and closest to the tip end, and - a transition region (32) between the root region (30) and the airfoil region (34), the profile of the transition region (32) 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.
15. A wind turbine blade according to claim 14, wherein the number of boundary layer control means (40) is provided in the airfoil region (34) only.
16. A wind turbine blade according to claim 14, wherein the number of boundary layer control means (40) is provided in the airfoil region (34) and the transition region (32).
17. A wind turbine rotor comprising a number, preferably two or three, of wind turbine blades according to any of the preceding claims.
18. A wind turbine comprising a number of blades according to claims 1-16 or a wind turbine rotor according to claim 17.
PCT/DK2008/000310 2007-08-31 2008-08-29 Wind turbine blade with submerged boundary layer control means comprisin crossing sub-channels WO2009026926A1 (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
DK08784433.8T DK2198153T3 (en) 2007-08-31 2008-08-29 Wind turbine blades with recessed boundary layer controllers including interlaced subchannels
CN2008801146427A CN101883922B (en) 2007-08-31 2008-08-29 Wind turbine blade with submerged boundary layer control means comprisin crossing sub-channels
AT08784433T ATE517255T1 (en) 2007-08-31 2008-08-29 WIND TURBINE BLADE WITH RECESSED BOUNDARY LAYER CONTROL MEANS COMPRISING CROSSING SECONDARY CHANNELS
EP08784433A EP2198153B1 (en) 2007-08-31 2008-08-29 Wind turbine blade with submerged boundary layer control means comprising crossing sub-channels
US12/733,410 US8550787B2 (en) 2007-08-31 2008-08-29 Wind turbine blade with submerged boundary layer control means comprising crossing sub-channels

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP07388065A EP2031244A1 (en) 2007-08-31 2007-08-31 Means to maintain flow of a flowing medium attached to the exterior of a flow control member by use of crossing sub-channels
EP07388065.0 2007-08-31

Publications (1)

Publication Number Publication Date
WO2009026926A1 true WO2009026926A1 (en) 2009-03-05

Family

ID=39204865

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DK2008/000310 WO2009026926A1 (en) 2007-08-31 2008-08-29 Wind turbine blade with submerged boundary layer control means comprisin crossing sub-channels

Country Status (7)

Country Link
US (1) US8550787B2 (en)
EP (2) EP2031244A1 (en)
CN (1) CN101883922B (en)
AT (1) ATE517255T1 (en)
DK (1) DK2198153T3 (en)
ES (1) ES2370096T3 (en)
WO (1) WO2009026926A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9039381B2 (en) 2010-12-17 2015-05-26 Vestas Wind Systems A/S Wind turbine blade and method for manufacturing a wind turbine blade with vortex generators

Families Citing this family (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100988237B1 (en) * 2008-11-06 2010-10-18 표수호 Rotating blade having structure for increasing fluid velocity
KR101005661B1 (en) * 2009-09-08 2011-01-05 김낙회 Propulsion device using fluid flow
US8047784B2 (en) 2011-03-22 2011-11-01 General Electric Company Lift device for rotor blade in wind turbine
US8414261B2 (en) 2011-05-31 2013-04-09 General Electric Company Noise reducer for rotor blade in wind turbine
EP2548800A1 (en) * 2011-07-22 2013-01-23 LM Wind Power A/S Method for retrofitting vortex generators on a wind turbine blade
US20130224037A1 (en) * 2011-09-13 2013-08-29 Dennis Simpson Compound airfoil
US9341158B2 (en) * 2011-12-08 2016-05-17 Inventus Holdings, Llc Quiet wind turbine blade
KR20140018036A (en) * 2012-08-03 2014-02-12 김낙회 Propulsion device using fluid flow
US20140328688A1 (en) * 2013-05-03 2014-11-06 General Electric Company Rotor blade assembly having vortex generators for wind turbine
EP3181895A1 (en) * 2015-12-17 2017-06-21 LM WP Patent Holding A/S Splitter plate arrangement for a serrated wind turbine blade
DE102016219035A1 (en) * 2016-09-30 2018-04-05 Ford Global Technologies, Llc Automotive underbody paneling with air intake
CN107143470A (en) * 2017-07-07 2017-09-08 中航瑞德(北京)科技有限公司 Wind electricity blade is vortexed synergy component and its installation method
GB201718069D0 (en) 2017-11-01 2017-12-13 Rolls Royce Plc Aerofoil
CN111577531A (en) * 2020-06-28 2020-08-25 上海海事大学 Shark gill type blade drag reduction structure for wind driven generator, blade and manufacturing method
CN112253391B (en) * 2020-10-30 2022-02-01 上海电气风电集团股份有限公司 Air flow control device, fan blade comprising same and wind generating set

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2800291A (en) * 1950-10-24 1957-07-23 Stephens Arthur Veryan Solid boundary surface for contact with a relatively moving fluid medium
US4455045A (en) * 1981-10-26 1984-06-19 Wheeler Gary O Means for maintaining attached flow of a flowing medium
GB2173861A (en) * 1985-04-22 1986-10-22 Gen Electric Directing air flow to an airstream probe
DE19738278A1 (en) * 1997-09-02 1999-03-04 Felix Hafner Adaptive rotor for wind power plants
WO2001016482A1 (en) * 1999-09-01 2001-03-08 Stichting Energieonderzoek Centrum Nederland Blade for a wind turbine
WO2002064422A1 (en) * 2001-02-02 2002-08-22 Fobox As Recesses on a surface
WO2007035758A1 (en) * 2005-09-19 2007-03-29 University Of Florida Research Foundation, Inc. Wind turbine blade comprising a boundary layer control system

Family Cites Families (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB120741A (en) 1917-06-08 1918-11-28 Brereton Burgess Roberts Improvements in Automatic Guns.
GB1257041A (en) * 1968-03-27 1971-12-15
US4699340A (en) * 1983-11-07 1987-10-13 Vehicle Research Corporation Laminar vortex pump system
CN85105039B (en) * 1985-06-29 1988-07-06 库斯托基金会 Apparatus for producing a force when in a moving fluid
FR2619069A1 (en) * 1987-08-03 1989-02-10 Weldon Thomas Motor vehicle equipped with aerodynamic means
US5114099A (en) * 1990-06-04 1992-05-19 W. L. Chow Surface for low drag in turbulent flow
US5598990A (en) * 1994-12-15 1997-02-04 University Of Kansas Center For Research Inc. Supersonic vortex generator
AU5618099A (en) 1998-09-16 2000-04-03 Lm Glasfiber A/S Wind turbine blade with vortex generator
US6494280B1 (en) 1999-08-27 2002-12-17 International Truck Intellectual Property Company, L.L.C. Telescoping torsion bar vehicle hood assist system
US6402470B1 (en) * 1999-10-05 2002-06-11 United Technologies Corporation Method and apparatus for cooling a wall within a gas turbine engine
EP1188902A1 (en) * 2000-09-14 2002-03-20 Siemens Aktiengesellschaft Impingement cooled wall
WO2006122547A1 (en) * 2005-05-17 2006-11-23 Vestas Wind Systems A/S A pitch controlled wind turbine blade, a wind turbine and use hereof
US7604461B2 (en) * 2005-11-17 2009-10-20 General Electric Company Rotor blade for a wind turbine having aerodynamic feature elements

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2800291A (en) * 1950-10-24 1957-07-23 Stephens Arthur Veryan Solid boundary surface for contact with a relatively moving fluid medium
US4455045A (en) * 1981-10-26 1984-06-19 Wheeler Gary O Means for maintaining attached flow of a flowing medium
GB2173861A (en) * 1985-04-22 1986-10-22 Gen Electric Directing air flow to an airstream probe
DE19738278A1 (en) * 1997-09-02 1999-03-04 Felix Hafner Adaptive rotor for wind power plants
WO2001016482A1 (en) * 1999-09-01 2001-03-08 Stichting Energieonderzoek Centrum Nederland Blade for a wind turbine
WO2002064422A1 (en) * 2001-02-02 2002-08-22 Fobox As Recesses on a surface
WO2007035758A1 (en) * 2005-09-19 2007-03-29 University Of Florida Research Foundation, Inc. Wind turbine blade comprising a boundary layer control system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9039381B2 (en) 2010-12-17 2015-05-26 Vestas Wind Systems A/S Wind turbine blade and method for manufacturing a wind turbine blade with vortex generators

Also Published As

Publication number Publication date
DK2198153T3 (en) 2011-11-14
EP2031244A1 (en) 2009-03-04
CN101883922B (en) 2012-11-21
CN101883922A (en) 2010-11-10
ATE517255T1 (en) 2011-08-15
EP2198153B1 (en) 2011-07-20
EP2198153A1 (en) 2010-06-23
ES2370096T3 (en) 2011-12-12
US20100260614A1 (en) 2010-10-14
US8550787B2 (en) 2013-10-08

Similar Documents

Publication Publication Date Title
US8550787B2 (en) Wind turbine blade with submerged boundary layer control means comprising crossing sub-channels
US8579594B2 (en) Wind turbine blade with submerged boundary layer control means
EP2589797B1 (en) Wind turbine blade comprising a slat mounted on a stall fence of the wind turbine blade
EP2799710B1 (en) Rotor blade assembly having vortex generators for wind turbine
EP2368035B1 (en) Wind turbine blade having a spoiler with effective separation of airflow
EP2368034B1 (en) Wind turbine blade having a flow guiding device with optimised height
US9951749B2 (en) System and method for trailing edge noise reduction of a wind turbine blade
WO2013060722A1 (en) Wind turbine blade provided with slat
EP2957766B1 (en) Pressure side stall strip for wind turbine blade
CN103711651A (en) Wind turbine rotor blade
EP3390812B1 (en) Splitter plate arrangement for a serrated wind turbine blade
US10280895B1 (en) Fluid turbine semi-annular delta-airfoil and associated rotor blade dual-winglet design
US10815963B2 (en) Wind-turbine rotor blade, trailing edge for wind-turbine rotor blade tip, method for producing a wind-turbine rotor blade, and wind turbine
WO2018046067A1 (en) Wind turbine blade comprising an airfoil profile
EP3472456B1 (en) Wind turbine blade with tip end serrations
EP4234917A1 (en) Vortex generator for wind turbine blade, wind turbine blade, and wind-power generation apparatus
DK201770908A1 (en) Wind turbine blade vortex generators
US20230279835A1 (en) Wind turbine serrations with upstream extension
GB2588258A (en) Wind turbine blade with a flow controlling element
CN113958445A (en) Rotor blade for a wind power plant, rotor for a wind power plant, building and wind power plant

Legal Events

Date Code Title Description
WWE Wipo information: entry into national phase

Ref document number: 200880114642.7

Country of ref document: CN

121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 08784433

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

WWE Wipo information: entry into national phase

Ref document number: 2008784433

Country of ref document: EP

WWE Wipo information: entry into national phase

Ref document number: 12733410

Country of ref document: US