CA2425447C - Wind turbine blade unit - Google Patents
Wind turbine blade unit Download PDFInfo
- Publication number
- CA2425447C CA2425447C CA002425447A CA2425447A CA2425447C CA 2425447 C CA2425447 C CA 2425447C CA 002425447 A CA002425447 A CA 002425447A CA 2425447 A CA2425447 A CA 2425447A CA 2425447 C CA2425447 C CA 2425447C
- Authority
- CA
- Canada
- Prior art keywords
- blade unit
- airfoil
- wind turbine
- wind
- main
- Prior art date
- Legal status (The legal status 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 status listed.)
- Expired - Fee Related
Links
- 230000003068 static effect Effects 0.000 claims abstract description 5
- 241000272517 Anseriformes Species 0.000 claims description 14
- 230000003190 augmentative effect Effects 0.000 claims 2
- 230000000153 supplemental effect Effects 0.000 claims 1
- 230000000977 initiatory effect Effects 0.000 abstract description 3
- 230000000452 restraining effect Effects 0.000 description 6
- RLQJEEJISHYWON-UHFFFAOYSA-N flonicamid Chemical compound FC(F)(F)C1=CC=NC=C1C(=O)NCC#N RLQJEEJISHYWON-UHFFFAOYSA-N 0.000 description 5
- 239000000463 material Substances 0.000 description 4
- 239000006096 absorbing agent Substances 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 230000000712 assembly Effects 0.000 description 2
- 238000000429 assembly Methods 0.000 description 2
- 239000003733 fiber-reinforced composite Substances 0.000 description 2
- 230000035939 shock Effects 0.000 description 2
- 241000596926 Sparaxis Species 0.000 description 1
- 239000011157 advanced composite material Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 239000003562 lightweight material Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002905 metal composite material Substances 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
- F03D—WIND MOTORS
- F03D1/00—Wind motors with rotation axis substantially parallel to the air flow entering the rotor
- F03D1/06—Rotors
- F03D1/0608—Rotors characterised by their aerodynamic shape
- F03D1/0633—Rotors characterised by their aerodynamic shape of the blades
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
- F05B2240/00—Components
- F05B2240/20—Rotors
- F05B2240/30—Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor
- F05B2240/31—Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor of changeable form or shape
-
- Y—GENERAL 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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/70—Wind energy
- Y02E10/72—Wind turbines with rotation axis in wind direction
Abstract
A blade unit assembly for applications such as wind turbines, characterized by the arrangement of a main airfoil and a smaller secondary airfoil joined by streamlined structural elements, is mounted on a rotor hub assembly using a holding spar extending from the main airfoil. The blade unit is balanced and can pivot about its holding spar longitudinal axis, and has aerodynamic static and dynamic stability that provides the blade unit with pitch angle self-adjustment capability for controlling the wind turbine rotor hub rotation speed, for initiating rotor rotation in low winds, and for limiting the rotor blades speed in high winds. A plurality of blade units is mounted on a rotor hub.
Description
WIND TURBINE BLADE UNIT
Description FIELD OF THE INVENTION
The present invention relates to rotating blades driven by the movement of a fluid or gas, in particular self adjusting pitch angle wind turbine blades.
BACKGROUND AND PRIOR ART
Historically, wind power was captured using windmills for the primary purpose of pumping water. Ancient windmills used sail foils and eventually rigid blade structures holding canvas material to control the amount of wind energy captured. Rotating the windmill in and out of the wind direction was also a method to control blade speed and limit damage to the windmill blades in high winds.
The slow rotating windmill blade assemblies have been replaced with modern airfoil blade profiles with predictable performances. Modern blade assemblies typically offer a lower rotor solidity, or surface area, than its ancestor's. The combination of higher relative wind speed capability and low solidity improves the wind turbine performance expectations.
Kinetic wind power increases with the cube of the wind speed. While extracting wind power in high wind conditions seems attractive, the physical limitations of the wind turbine assembly require that a system be in place to limit the resulting wind forces on the wind turbine to avoid damages.
Today, aerodynamic furling devices or hydraulic systems have been created to control the rotor blade assembly orientation relative to the wind in order to decrease the wind surface area in high wind conditions. In other cases, mechanical brakes are used to temporarily stop the rotation of the blade assembly to avoid all possible damage. Other methods have been developed to control the rotor rotational speed such as rotor blade aerodynamic brakes, rotor blade aerodynamic stall, rotor blade ailerons, centrifugal force based control systems, and rotor blade camber or pitch control systems.
The following patents have been issued in Canada and the United States of America to propose rotor speed control solutions:
1092983 1/1981 Lippert 1120538 3/1982 Kos et al.
2193972 8/2002 Shin 4,178,127 12/1979 Zahorecz 4,423,333 12/1983 Rossman 4,339,666 7/1982 Patrick et al.
4,348,156 9/1982 Andrews et al.
4,348,155 9/1982 Barnes et al.
4,352,634 10/1982 Andrews et all 4,462,753 7/1984 Harner et al.
4,533,297 8/1985 Bassett 4,632,637 12/1986 Traudt 4,656,362 411987 Harner et al.
4,715,782 12/1987 Shimmel 5,161,952 11/1992 Eggers. Jr.
5,527,152 6/1996 Coleman et al.
5,527,151 6/1996 Coleman et al.
5,456,579 10/1995 Olson 2002/0153729 10/2002 Beauchamp et al 2of11 WIND TURBINE BLADE UNIT
The solutions developed in the past mostly involved articulated components driven by mechanical actuators involving the use of electronic control systems. The resulting solutions are complex active systems such as in patent 4,423,333.
A departure from articulated control systems consists of passive methods such as advanced composite material rotor blades that twist under certain operating conditions. Rotor blades with passive pitch control characteristics have been conceived as in patent 4,178,127. However, the inherent aerodynamic stability of a rotor blade assembly has yet to be used as the single means to control the rotor blade pitch for initiating rotation of a wind turbine rotor in low winds, for controlling rotor blade speed under changing wind speed operating conditions, and for stopping rotation of a wind turbine rotor in high winds.
SUMMARY OF THE INVENTION
A main object of the present invention is the provision of a passive solution for controlling the pitch angle of wind turbine rotor blades, including initiating the pivoting of the rotor blades toward the incoming wind to initiate rotor blade rotation and to limit rotor blade rotation speed in high winds.
It is also an object of this invention to provide a means to attach a blade unit to a rotor hub assembly, whereby the blade unit may pivot about its longitudinal axis.
The present invention is a blade unit consisting of two blades disposed in a canard type configuration providing aerodynamic static and dynamic stability, whereby both airtoils provide positive lift. This invention may be used in combination with any type of airfoil structure.
It is an object of this invention to locate the smaller secondary airfoil ahead of the main airfoil leading edge and upwind in a canard configuration. The smaller airfoil may be located below or above the main airfoil chord axis. The positioning of the smaller canard airfoil is dependent on the designed operating rotational speed of the rotating blade unit as to avoid airtlow interference of the secondary airtoil on the main airfoil. The positive incidence angle of the small airfoil relative to the main airfoil chord axis combined with the proper combination of airfoil profile will ensure the canard airfoil will stall before the main airfoil in a gust wind situation and therefore ensure the blade unit assembly will tilt into the wind to restore generation of lift.
It is a main object of this invention to create a canard configured rotating blade unit assembly where the tip portion of the main airfoil forming less than 25% of the length of the blade unit assembly applies negative moment forces on the rotating blade unit about the longitudinal pivoting axis of the blade unit, given that the main airfoil lift component is located between the blade unit longitudinal pivoting axis and the main airfoil trailing edge. In high wind situations, a relative wind speed exceeding the rotating blade unit operating speed characterized by its aerodynamic static stability characteristics will cause the pivoting of the blade unit leading edges upwind and limit the rotor blade rotation speed due to the incremental lift acting on the tip portion of the main airfoil.
It is also an object of this invention to make the radius of the main airtoil of a blade unit extend radially outward beyond the secondary canard airfoil radius. In this particular configuration, the blade unit assembly operates at a designated rotational speed which, when exceeded, causes the section of the main airfoil to augment its lift component more rapidly than that of the secondary canard airfoil, thus creating a negative moment on the blade unit therefore reducing its pitch angle and limiting its rotational speed.
In the subject invention, a proposed means to attach a blade unit to a rotor hub assembly consists of a spar threaded at one extremity with a counterpart assembly on the hub. The center line of the blade unit holding spar longitudinal axis is located forward to the main blade aerodynamic center typically located at approximately 25% of the main blade chord.
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The blade unit is prevented from completely rotating about its longitudinal axis using restraining devices limiting the pivoting to no more than 90 degrees to ensure the resulting total lift from the blade unit makes the rotor assembly turn in the desired rotational direction.
In addition, the blade unit assembly is statically weight balanced around the holding spar as to ensure gravity forces do not affect blade unit pitch angle during its rotation. This is accomplished with the selection of proper materials, weight distribution and use of counterbalancing weights located on the blade unit holding spar near the hub assembly.
The said blade unit generates lift when the incoming wind causes the blade unit to pivot about its longitudinal axis, pointing the leading edge of the main and secondary airfoils into the wind, at which point a sufficient wind speed causes the blade unit to start rotating around the rotor hub. As the relative wind direction and speed on the blade unit changes with the increased rotor speed, the blade unit reaches a rotational speed determined by the proportions and dimensions of the bade unit assembly and by the power extracted through the rotor hub. Further increases in wind speed will increase the power transferred to the rotor blade unit, causing the blade unit rotational speed to increase if power is not extracted. If a condition is created such that the blade unit accelerates beyond its predetermined relative wind speed, the additional lift created at the tip of the main airfoil, in the area that extends beyond the radius of the secondary airfoil, will cause the blade unit to pivot into the wind and slow it down.
In another aspect of the present invention, the wind turbine blade assembly consists of a plurality of blade units attached similarly to the rotor hub assembly. The blade units may be linked with a common pitch control assembly apparatus located on the blade unit spars to ensure all blades operate with a common pitch angle.
In an alternative construction of the blade unit, the blade unit is twisted as to reduce the pitch angle of the tip of the blade unit, to reduce the load at the tip of the blade unit in rotation, the said load created by the higher relative wind speeds at the tip of the blade.
BRIEF DESCRIPTION OF THE DRAWINGS
The benefits, advantages and characteristics illustrated in the drawings described below form part of the specification of this invention.
Figure 1 is a schematic side view of a canard configuration blade unit excluding the holding spar.
Figure 2 is a schematic plan view of a canard configuration blade unit.
Figures 3.a-3.b present views of the general location of the counterweight and pivoting restraining device on the blade unit holding spar, as well of a view of the blade unit holding spar threaded extremity and lateral force bearing assembly matching the sliding counterparts fixed on the wind turbine hub assembly.
Figures 4.a-4.c are schematic views of alternative blade unit canard configurations contributing to the blade self-adjusting characteristics aimed by this invention.
4of11 WIND TURBINE BLADE UNIT
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In the basic embodiment of the invention, the arrangement of the blade unit depicted in part in FIG. 1, consists of a positive camber main airfoil 1 on which a symmetrical secondary airtoil 2 is mounted using at least two streamlined structural elements 3 distributed along the length of the secondary airfoil 2. The airtoils 1 and 2 consists of sturdy but flexible structures made of lightweight materials such as fiber reinforced composite materials, wood or aluminum with fatigue resistant properties.
In the preferred embodiments, the secondary airtoil 2 is located ahead of the main airtoil 1 in a canard configuration. More specifically, the trailing edge of the secondary airfoil 2 shown in FIG. 1 is located ahead of the leading edge of the main airfoil 1 along the main airfoil chord axis 10.
FIG.1 shows the secondary airfoil 2 located below the main airfoil chord axis 10 as to not interfere with the main airfoil air flow in the direction depicted by the prominent relative wind direction 17. The operating relative wind direction 17 is primarily determined by the aerodynamic characteristics of the assembled blade unit. The wind 18 is shown transversal to the plan of rotation 14 as maintained by the horizontal axis wind turbines directional system.
The streamlined structural elements 3 depicted in FIGS. 1-4 are rigid structures made of vibration resistant metal or fiber reinforced composite material beams with an aerodynamic external profile in the direction perpendicular to the longitudinal axis of the main airfoil 1 and parallel to the main airfoil chord axis 10. The structural elements 3 are fastened to reinforced bottom surface areas of the main airfoil or are fastened to the main airfoil rib structures using locking type fasteners.
At the other end, the structural elements 3 are fastened to the thinner secondary airfoil 2 core structure preferably using locking type fasteners. Structural elements 3 maintain a constant distance between the main airfoil aerodynamic center and the secondary airfoil aerodynamic center. The structural elements 3 also counteract the lift forces and centrifugal forces on the secondary airfoil 2.
In the preferred embodiment of this invention, the canard configuration features aerodynamic static stability characteristics whereby specific physical proportions are respected.
In particular, the secondary airfoil 2 shown in FIG. 1 has a positive incidence pitch 13 defined by the angle between the main airfoil zero lift line direction 11 and the secondary airfoil zero lift line direction 12 which consequently is the same axis as the secondary airtoil chord axis for the preferably symmetrical secondary airfoil 2.
The said blade unit moves in a plan of rotation 14 shown in FIG. 1 around a rotor hub in the direction 15.
The said blade unit pivots about its longitudinal axis 7 depicted in FIG. 2, located between the main airtoil leading edge and the aerodynamic center of the main airfoil 2 depicted by the aerodynamic center line 16 located at approximately 25% of the main airfoil chord from the main airfoil leading edge.
FIG. 2 shows the preferred arrangement of the blade unit and presents a key aspect of the present invention whereby the main airfoil 1 extends further radially outward than the said secondary airfoil 2. The area of the tip of the main airfoil 1 which extends beyond the radius of the secondary airfoil 2 causes the blade unit to pivot into the wind and slow it down when the relative wind speed increases suddenly.
In another aspect of the present invention, a blade unit holding spar 5 extending from the root of the main airfoil is secured firmly to the main airfoil as shown in FIG. 2. In the preferred embodiment, the holding spar 5 is an extension and forms part of the main airfoil 2. The blade unit holding spar 5 provides a means to connect the said blade unit to the wind turbine rotor hub assembly 26 mounted on the rotor hub shaft 27, as shown in FIG. 3.b.
In yet another aspect of the present invention, the said blade unit holding spar 5 shown in FIG. 2 includes a threaded extremity 6 that screws smoothly in a matching threaded counterpart 24 mounted on the horizontal axis wind turbine hub assembly 26 depicted in FIG. 3.b. The said holding spar threaded extremity 6 has machined low pitch threads providing a rotating sliding grip on its matching counterpart 24 on the rotor hub assembly 26. The threaded extremity 6 of the holding spar 5 is preferably aligned and centered with the main airfoil aerodynamic center line 7 depicted in FIGS. 2 and 3.b. The said holding 5of11 WIND TURBINE BLADE UNIT
spar threaded extremity 6 is complemented by a lateral force bearing 23 located between threaded extremity 6 of the said holding spar 5 and the root of the main airtoil 1, the said force bearing 23 matching a sliding counterpart 25 fixed on the wind turbine rotor hub assembly 26. A
ring 28 secures the bearing 23 in position on the holding spar 5.
In yet another aspect of the present invention, the thread direction of the said threaded extremity 6 is such that the centrifugal forces on the rotating blade unit creates forces at the contact area of the threads in the direction that would cause the blade unit to pivot into the wind.
F1GS. 3a and 3.b depict mechanisms which are mounted to the blade unit holding spar 5. In another aspect of the present invention, the blade unit holding spar 5 comprises a counterweight 20 mounted on and secured to a ring 28 fastened to the holding spar 5 to balance the said blade unit weight about its longitudinal axis 7.
In another aspect of the present invention, the said blade unit holding spar 5 shown in FIG. 3.a further comprises a blade unit pivoting restraining device 21 to limit the operation of the said blade unit within a predetermined pitch angle range of less than 90 degrees about the longitudinal axis of the said blade unit to prevent the rotor blades from rotating in the opposite direction. As an improvement to the blade unit pivoting restraining device 21, the said restraining device 21 is also a shock absorber type strut linked to a rod mounted perpendicularly to the holding spar 5 to provide functions such as pitch angle range stopper, rotation movement absorber, and pitch adjuster for wind conditions below the cut-in wind speed to keep the pitch angle of the blade unit to the maximum - pointing into the wind. The other end of the shock absorber pivoting restraining device 21 is attached to the rotor hub assembly holding point 22 shown in FIG. 3.b.
FIGS. 4.a to 4.c show alternate blade unit canard configurations which provide improvements to this invention. The configurations present aerodynamic characteristics that augment the negative moment forces of the blade unit in high relative winds to cause the pivoting of the blade unit into the wind when the relative wind speeds along the blade unit exceed designated values. FIG. 4.a shows a secondary airtoil 31 with a longitudinal axis 30 tilting toward the main airfoil tip. In an alternate embodiment depicted in FIG. 4.b, the holding spar axis 34 is tilted laterally toward the leading edge of tip of the main airfoil at an angle no greater than 10 degrees. In this configuration, the secondary airfoil 33 is permitted to extend the length of the main airfoil as to create additional blade unit lift capacity.
In yet another embodiment depicted in FIG. 4.c, the secondary airfoil 36 is tapered at its tip. In this configuration, the secondary airfoil 36 is permitted to extend the length of the main airfoil as to create additional blade unit lift capacity.
6of11
Description FIELD OF THE INVENTION
The present invention relates to rotating blades driven by the movement of a fluid or gas, in particular self adjusting pitch angle wind turbine blades.
BACKGROUND AND PRIOR ART
Historically, wind power was captured using windmills for the primary purpose of pumping water. Ancient windmills used sail foils and eventually rigid blade structures holding canvas material to control the amount of wind energy captured. Rotating the windmill in and out of the wind direction was also a method to control blade speed and limit damage to the windmill blades in high winds.
The slow rotating windmill blade assemblies have been replaced with modern airfoil blade profiles with predictable performances. Modern blade assemblies typically offer a lower rotor solidity, or surface area, than its ancestor's. The combination of higher relative wind speed capability and low solidity improves the wind turbine performance expectations.
Kinetic wind power increases with the cube of the wind speed. While extracting wind power in high wind conditions seems attractive, the physical limitations of the wind turbine assembly require that a system be in place to limit the resulting wind forces on the wind turbine to avoid damages.
Today, aerodynamic furling devices or hydraulic systems have been created to control the rotor blade assembly orientation relative to the wind in order to decrease the wind surface area in high wind conditions. In other cases, mechanical brakes are used to temporarily stop the rotation of the blade assembly to avoid all possible damage. Other methods have been developed to control the rotor rotational speed such as rotor blade aerodynamic brakes, rotor blade aerodynamic stall, rotor blade ailerons, centrifugal force based control systems, and rotor blade camber or pitch control systems.
The following patents have been issued in Canada and the United States of America to propose rotor speed control solutions:
1092983 1/1981 Lippert 1120538 3/1982 Kos et al.
2193972 8/2002 Shin 4,178,127 12/1979 Zahorecz 4,423,333 12/1983 Rossman 4,339,666 7/1982 Patrick et al.
4,348,156 9/1982 Andrews et al.
4,348,155 9/1982 Barnes et al.
4,352,634 10/1982 Andrews et all 4,462,753 7/1984 Harner et al.
4,533,297 8/1985 Bassett 4,632,637 12/1986 Traudt 4,656,362 411987 Harner et al.
4,715,782 12/1987 Shimmel 5,161,952 11/1992 Eggers. Jr.
5,527,152 6/1996 Coleman et al.
5,527,151 6/1996 Coleman et al.
5,456,579 10/1995 Olson 2002/0153729 10/2002 Beauchamp et al 2of11 WIND TURBINE BLADE UNIT
The solutions developed in the past mostly involved articulated components driven by mechanical actuators involving the use of electronic control systems. The resulting solutions are complex active systems such as in patent 4,423,333.
A departure from articulated control systems consists of passive methods such as advanced composite material rotor blades that twist under certain operating conditions. Rotor blades with passive pitch control characteristics have been conceived as in patent 4,178,127. However, the inherent aerodynamic stability of a rotor blade assembly has yet to be used as the single means to control the rotor blade pitch for initiating rotation of a wind turbine rotor in low winds, for controlling rotor blade speed under changing wind speed operating conditions, and for stopping rotation of a wind turbine rotor in high winds.
SUMMARY OF THE INVENTION
A main object of the present invention is the provision of a passive solution for controlling the pitch angle of wind turbine rotor blades, including initiating the pivoting of the rotor blades toward the incoming wind to initiate rotor blade rotation and to limit rotor blade rotation speed in high winds.
It is also an object of this invention to provide a means to attach a blade unit to a rotor hub assembly, whereby the blade unit may pivot about its longitudinal axis.
The present invention is a blade unit consisting of two blades disposed in a canard type configuration providing aerodynamic static and dynamic stability, whereby both airtoils provide positive lift. This invention may be used in combination with any type of airfoil structure.
It is an object of this invention to locate the smaller secondary airfoil ahead of the main airfoil leading edge and upwind in a canard configuration. The smaller airfoil may be located below or above the main airfoil chord axis. The positioning of the smaller canard airfoil is dependent on the designed operating rotational speed of the rotating blade unit as to avoid airtlow interference of the secondary airtoil on the main airfoil. The positive incidence angle of the small airfoil relative to the main airfoil chord axis combined with the proper combination of airfoil profile will ensure the canard airfoil will stall before the main airfoil in a gust wind situation and therefore ensure the blade unit assembly will tilt into the wind to restore generation of lift.
It is a main object of this invention to create a canard configured rotating blade unit assembly where the tip portion of the main airfoil forming less than 25% of the length of the blade unit assembly applies negative moment forces on the rotating blade unit about the longitudinal pivoting axis of the blade unit, given that the main airfoil lift component is located between the blade unit longitudinal pivoting axis and the main airfoil trailing edge. In high wind situations, a relative wind speed exceeding the rotating blade unit operating speed characterized by its aerodynamic static stability characteristics will cause the pivoting of the blade unit leading edges upwind and limit the rotor blade rotation speed due to the incremental lift acting on the tip portion of the main airfoil.
It is also an object of this invention to make the radius of the main airtoil of a blade unit extend radially outward beyond the secondary canard airfoil radius. In this particular configuration, the blade unit assembly operates at a designated rotational speed which, when exceeded, causes the section of the main airfoil to augment its lift component more rapidly than that of the secondary canard airfoil, thus creating a negative moment on the blade unit therefore reducing its pitch angle and limiting its rotational speed.
In the subject invention, a proposed means to attach a blade unit to a rotor hub assembly consists of a spar threaded at one extremity with a counterpart assembly on the hub. The center line of the blade unit holding spar longitudinal axis is located forward to the main blade aerodynamic center typically located at approximately 25% of the main blade chord.
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The blade unit is prevented from completely rotating about its longitudinal axis using restraining devices limiting the pivoting to no more than 90 degrees to ensure the resulting total lift from the blade unit makes the rotor assembly turn in the desired rotational direction.
In addition, the blade unit assembly is statically weight balanced around the holding spar as to ensure gravity forces do not affect blade unit pitch angle during its rotation. This is accomplished with the selection of proper materials, weight distribution and use of counterbalancing weights located on the blade unit holding spar near the hub assembly.
The said blade unit generates lift when the incoming wind causes the blade unit to pivot about its longitudinal axis, pointing the leading edge of the main and secondary airfoils into the wind, at which point a sufficient wind speed causes the blade unit to start rotating around the rotor hub. As the relative wind direction and speed on the blade unit changes with the increased rotor speed, the blade unit reaches a rotational speed determined by the proportions and dimensions of the bade unit assembly and by the power extracted through the rotor hub. Further increases in wind speed will increase the power transferred to the rotor blade unit, causing the blade unit rotational speed to increase if power is not extracted. If a condition is created such that the blade unit accelerates beyond its predetermined relative wind speed, the additional lift created at the tip of the main airfoil, in the area that extends beyond the radius of the secondary airfoil, will cause the blade unit to pivot into the wind and slow it down.
In another aspect of the present invention, the wind turbine blade assembly consists of a plurality of blade units attached similarly to the rotor hub assembly. The blade units may be linked with a common pitch control assembly apparatus located on the blade unit spars to ensure all blades operate with a common pitch angle.
In an alternative construction of the blade unit, the blade unit is twisted as to reduce the pitch angle of the tip of the blade unit, to reduce the load at the tip of the blade unit in rotation, the said load created by the higher relative wind speeds at the tip of the blade.
BRIEF DESCRIPTION OF THE DRAWINGS
The benefits, advantages and characteristics illustrated in the drawings described below form part of the specification of this invention.
Figure 1 is a schematic side view of a canard configuration blade unit excluding the holding spar.
Figure 2 is a schematic plan view of a canard configuration blade unit.
Figures 3.a-3.b present views of the general location of the counterweight and pivoting restraining device on the blade unit holding spar, as well of a view of the blade unit holding spar threaded extremity and lateral force bearing assembly matching the sliding counterparts fixed on the wind turbine hub assembly.
Figures 4.a-4.c are schematic views of alternative blade unit canard configurations contributing to the blade self-adjusting characteristics aimed by this invention.
4of11 WIND TURBINE BLADE UNIT
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In the basic embodiment of the invention, the arrangement of the blade unit depicted in part in FIG. 1, consists of a positive camber main airfoil 1 on which a symmetrical secondary airtoil 2 is mounted using at least two streamlined structural elements 3 distributed along the length of the secondary airfoil 2. The airtoils 1 and 2 consists of sturdy but flexible structures made of lightweight materials such as fiber reinforced composite materials, wood or aluminum with fatigue resistant properties.
In the preferred embodiments, the secondary airtoil 2 is located ahead of the main airtoil 1 in a canard configuration. More specifically, the trailing edge of the secondary airfoil 2 shown in FIG. 1 is located ahead of the leading edge of the main airfoil 1 along the main airfoil chord axis 10.
FIG.1 shows the secondary airfoil 2 located below the main airfoil chord axis 10 as to not interfere with the main airfoil air flow in the direction depicted by the prominent relative wind direction 17. The operating relative wind direction 17 is primarily determined by the aerodynamic characteristics of the assembled blade unit. The wind 18 is shown transversal to the plan of rotation 14 as maintained by the horizontal axis wind turbines directional system.
The streamlined structural elements 3 depicted in FIGS. 1-4 are rigid structures made of vibration resistant metal or fiber reinforced composite material beams with an aerodynamic external profile in the direction perpendicular to the longitudinal axis of the main airfoil 1 and parallel to the main airfoil chord axis 10. The structural elements 3 are fastened to reinforced bottom surface areas of the main airfoil or are fastened to the main airfoil rib structures using locking type fasteners.
At the other end, the structural elements 3 are fastened to the thinner secondary airfoil 2 core structure preferably using locking type fasteners. Structural elements 3 maintain a constant distance between the main airfoil aerodynamic center and the secondary airfoil aerodynamic center. The structural elements 3 also counteract the lift forces and centrifugal forces on the secondary airfoil 2.
In the preferred embodiment of this invention, the canard configuration features aerodynamic static stability characteristics whereby specific physical proportions are respected.
In particular, the secondary airfoil 2 shown in FIG. 1 has a positive incidence pitch 13 defined by the angle between the main airfoil zero lift line direction 11 and the secondary airfoil zero lift line direction 12 which consequently is the same axis as the secondary airtoil chord axis for the preferably symmetrical secondary airfoil 2.
The said blade unit moves in a plan of rotation 14 shown in FIG. 1 around a rotor hub in the direction 15.
The said blade unit pivots about its longitudinal axis 7 depicted in FIG. 2, located between the main airtoil leading edge and the aerodynamic center of the main airfoil 2 depicted by the aerodynamic center line 16 located at approximately 25% of the main airfoil chord from the main airfoil leading edge.
FIG. 2 shows the preferred arrangement of the blade unit and presents a key aspect of the present invention whereby the main airfoil 1 extends further radially outward than the said secondary airfoil 2. The area of the tip of the main airfoil 1 which extends beyond the radius of the secondary airfoil 2 causes the blade unit to pivot into the wind and slow it down when the relative wind speed increases suddenly.
In another aspect of the present invention, a blade unit holding spar 5 extending from the root of the main airfoil is secured firmly to the main airfoil as shown in FIG. 2. In the preferred embodiment, the holding spar 5 is an extension and forms part of the main airfoil 2. The blade unit holding spar 5 provides a means to connect the said blade unit to the wind turbine rotor hub assembly 26 mounted on the rotor hub shaft 27, as shown in FIG. 3.b.
In yet another aspect of the present invention, the said blade unit holding spar 5 shown in FIG. 2 includes a threaded extremity 6 that screws smoothly in a matching threaded counterpart 24 mounted on the horizontal axis wind turbine hub assembly 26 depicted in FIG. 3.b. The said holding spar threaded extremity 6 has machined low pitch threads providing a rotating sliding grip on its matching counterpart 24 on the rotor hub assembly 26. The threaded extremity 6 of the holding spar 5 is preferably aligned and centered with the main airfoil aerodynamic center line 7 depicted in FIGS. 2 and 3.b. The said holding 5of11 WIND TURBINE BLADE UNIT
spar threaded extremity 6 is complemented by a lateral force bearing 23 located between threaded extremity 6 of the said holding spar 5 and the root of the main airtoil 1, the said force bearing 23 matching a sliding counterpart 25 fixed on the wind turbine rotor hub assembly 26. A
ring 28 secures the bearing 23 in position on the holding spar 5.
In yet another aspect of the present invention, the thread direction of the said threaded extremity 6 is such that the centrifugal forces on the rotating blade unit creates forces at the contact area of the threads in the direction that would cause the blade unit to pivot into the wind.
F1GS. 3a and 3.b depict mechanisms which are mounted to the blade unit holding spar 5. In another aspect of the present invention, the blade unit holding spar 5 comprises a counterweight 20 mounted on and secured to a ring 28 fastened to the holding spar 5 to balance the said blade unit weight about its longitudinal axis 7.
In another aspect of the present invention, the said blade unit holding spar 5 shown in FIG. 3.a further comprises a blade unit pivoting restraining device 21 to limit the operation of the said blade unit within a predetermined pitch angle range of less than 90 degrees about the longitudinal axis of the said blade unit to prevent the rotor blades from rotating in the opposite direction. As an improvement to the blade unit pivoting restraining device 21, the said restraining device 21 is also a shock absorber type strut linked to a rod mounted perpendicularly to the holding spar 5 to provide functions such as pitch angle range stopper, rotation movement absorber, and pitch adjuster for wind conditions below the cut-in wind speed to keep the pitch angle of the blade unit to the maximum - pointing into the wind. The other end of the shock absorber pivoting restraining device 21 is attached to the rotor hub assembly holding point 22 shown in FIG. 3.b.
FIGS. 4.a to 4.c show alternate blade unit canard configurations which provide improvements to this invention. The configurations present aerodynamic characteristics that augment the negative moment forces of the blade unit in high relative winds to cause the pivoting of the blade unit into the wind when the relative wind speeds along the blade unit exceed designated values. FIG. 4.a shows a secondary airtoil 31 with a longitudinal axis 30 tilting toward the main airfoil tip. In an alternate embodiment depicted in FIG. 4.b, the holding spar axis 34 is tilted laterally toward the leading edge of tip of the main airfoil at an angle no greater than 10 degrees. In this configuration, the secondary airfoil 33 is permitted to extend the length of the main airfoil as to create additional blade unit lift capacity.
In yet another embodiment depicted in FIG. 4.c, the secondary airfoil 36 is tapered at its tip. In this configuration, the secondary airfoil 36 is permitted to extend the length of the main airfoil as to create additional blade unit lift capacity.
6of11
Claims (7)
1. A wind turbine blade unit supported by a rotor hub assembly mounted on a horizontal axis wind turbine rotor shaft for pivotal deflection about a spanwise blade unit pivot axis comprising:
a main airfoil extending radially outward and generally parallel to said spanwise blade unit pivot axis with its aerodynamic center positioned rearward to said spanwise blade unit pivot axis for providing the main positive lift to said blade unit and for a providing negative moment forces about said spanwise blade unit pivot axis;
a secondary airfoil rigidly attached to said main airfoil in a canard configuration using streamlined structural elements, wherein the secondary airfoil has its aerodynamic center forward to said spanwise blade unit pivot axis and has a predetermined positive incidence angle relative to the main airfoil chord axis for providing secondary positive lift to said blade unit and for establishing aerodynamic static and dynamic stability to said blade unit and thereby establishing a pitch angle self-adjustment means of operation to said blade unit; and a blade unit holding spar rigidly mounted to said main airfoil and pivotally attached to said rotor hub assembly.
a main airfoil extending radially outward and generally parallel to said spanwise blade unit pivot axis with its aerodynamic center positioned rearward to said spanwise blade unit pivot axis for providing the main positive lift to said blade unit and for a providing negative moment forces about said spanwise blade unit pivot axis;
a secondary airfoil rigidly attached to said main airfoil in a canard configuration using streamlined structural elements, wherein the secondary airfoil has its aerodynamic center forward to said spanwise blade unit pivot axis and has a predetermined positive incidence angle relative to the main airfoil chord axis for providing secondary positive lift to said blade unit and for establishing aerodynamic static and dynamic stability to said blade unit and thereby establishing a pitch angle self-adjustment means of operation to said blade unit; and a blade unit holding spar rigidly mounted to said main airfoil and pivotally attached to said rotor hub assembly.
2. The wind turbine blade unit of claim 1, wherein said main airfoil extends further radially outward from said rotor hub assembly than said secondary airfoil for causing the blade unit to pivot into the wind, to slow down and then to stop its rotation about said horizontal axis wind turbine rotor shaft when the relative wind reaches predetermined speeds.
3. The wind turbine blade unit of claim 1, wherein said blade unit holding spar comprises a threaded extremity matching a threaded counterpart on said rotor hub assembly and thereby providing a means for pivotally attaching the blade unit to said rotor hub assembly.
4. The wind turbine blade unit of claim 3, wherein the thread direction of the said threaded extremity is such that centrifugal forces on said blade unit create a tendency for said blade unit to pivot into the wind.
5. The wind turbine blade unit of claim 4, wherein said blade unit holding spar further comprises a lateral force bearing means located between said threaded extremity of said blade unit holding spar and the root of said main airfoil for providing a supplemental means to pivotally hold the blade unit to said rotor hub assembly.
6. The wind turbine blade unit of claim 1, wherein the longitudinal axis of said secondary airfoil is outwardly tilted toward said main airfoil in the plan of rotation of said blade unit for augmenting the relative negative moment forces of said main airfoil in high relative wind speed conditions.
7. The wind turbine blade unit of claim 1, wherein the longitudinal axis of said holding spar is tilted toward the tip of the secondary airfoil in the plan of rotation of said blade unit for augmenting the negative moment forces of said main airfoil in high relative wind speed conditions.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002425447A CA2425447C (en) | 2003-04-17 | 2003-04-17 | Wind turbine blade unit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002425447A CA2425447C (en) | 2003-04-17 | 2003-04-17 | Wind turbine blade unit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2425447A1 CA2425447A1 (en) | 2004-10-17 |
| CA2425447C true CA2425447C (en) | 2006-03-14 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002425447A Expired - Fee Related CA2425447C (en) | 2003-04-17 | 2003-04-17 | Wind turbine blade unit |
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| CA (1) | CA2425447C (en) |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BRPI0600613B1 (en) * | 2006-03-14 | 2015-08-11 | Tecsis Tecnologia E Sist S Avançados S A | Multi-element blade with aerodynamic profiles |
| DK2078852T4 (en) * | 2008-01-11 | 2022-07-04 | Siemens Gamesa Renewable Energy As | Rotor blade for a wind turbine |
| EP2107235A1 (en) * | 2008-04-02 | 2009-10-07 | Lm Glasfiber A/S | A wind turbine blade with an auxiliary airfoil |
| ES2330500B1 (en) * | 2008-05-30 | 2010-09-13 | GAMESA INNOVATION & TECHNOLOGY, S.L. UNIPERSONAL | AEROGENERATOR SHOVEL WITH HYPERSUSTENTING ELEMENTS. |
| DE102008026474A1 (en) * | 2008-06-03 | 2009-12-10 | Mickeler, Siegfried, Prof. Dr.-Ing. | Rotor blade for a wind turbine and wind turbine |
| US9200614B2 (en) | 2009-05-19 | 2015-12-01 | Vestas Wind Systems A/S | Wind turbine and a blade for a wind turbine |
| EP2438299A2 (en) * | 2009-06-03 | 2012-04-11 | Flodesign Wind Turbine Corporation | Wind turbine blades with mixer lobes |
| EP2383465A1 (en) | 2010-04-27 | 2011-11-02 | Lm Glasfiber A/S | Wind turbine blade provided with a slat assembly |
| CN102434384A (en) * | 2011-11-11 | 2012-05-02 | 张向增 | Novel composite material blade of horizontal shaft wind generating set |
| US8376703B2 (en) * | 2011-11-21 | 2013-02-19 | General Electric Company | Blade extension for rotor blade in wind turbine |
| WO2014006542A2 (en) * | 2012-07-05 | 2014-01-09 | Nelson Mandela Metropolitan University | Turbine arrangement |
| WO2014113888A1 (en) * | 2013-01-22 | 2014-07-31 | Distributed Thermal Systems Ltd. | Multiple airfoil wind turbine blade assembly |
| US20150322916A1 (en) * | 2014-05-08 | 2015-11-12 | Siemens Aktiengesellschaft | Soiling shield for wind turbine blade |
| US10253753B2 (en) | 2014-09-25 | 2019-04-09 | Winfoor Ab | Rotor blade for wind turbine |
| US10094358B2 (en) * | 2015-07-21 | 2018-10-09 | Winnova Energy LLC | Wind turbine blade with double airfoil profile |
| CN105298741B (en) * | 2015-11-03 | 2018-11-06 | 周方 | The reinforced blade of wind-driven generator |
-
2003
- 2003-04-17 CA CA002425447A patent/CA2425447C/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| CA2425447A1 (en) | 2004-10-17 |
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