WO2016057110A1 - Pale de rotor de turbine éolienne comprenant une emplanture avec axe vers l'avant - Google Patents

Pale de rotor de turbine éolienne comprenant une emplanture avec axe vers l'avant Download PDF

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Publication number
WO2016057110A1
WO2016057110A1 PCT/US2015/044561 US2015044561W WO2016057110A1 WO 2016057110 A1 WO2016057110 A1 WO 2016057110A1 US 2015044561 W US2015044561 W US 2015044561W WO 2016057110 A1 WO2016057110 A1 WO 2016057110A1
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Prior art keywords
blade
section
root
axis
turbine according
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PCT/US2015/044561
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English (en)
Inventor
Richard Von Berg
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Richard Von Berg
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Publication of WO2016057110A1 publication Critical patent/WO2016057110A1/fr

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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
    • 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

Definitions

  • This invention relates to blades of wind turbine rotors, especially wind turbines of the front-runner or forward facing type, the resulting rotors and to wind turbines utilizing such rotors, wherein the root possesses a forward cone angle and the remainder of the blade, or a majority thereof, has an aft cone angle.
  • the invention also relates to rotor blades of unitary or segmented design, incorporating a forward angled root section and an aft angled outer or blade section, for use on wind turbines.
  • Aft-running or downwind facing wind turbines wherein the blades describe a cone angle, that is, where the blade's structural axis is inclined at an acute angle with respect to the rotational axis of the rotor are known in the art. Examples include Bassett US-A- 4,533,297, US-A-5,584,655, and US-B-7,530,785. Such blades are known to possess improved stability and experience reduced flutter and vibration under changing wind conditions. Disadvantageously, aft-running wind turbines experience excessive vibration and stress due to disruption of the wind by the wind turbine tower over the bottom portion of the rotor swept area. Scaling such turbines to large size, such as 5 or 10 MW of power generation, is extremely difficult due to this inherent design obstacle.
  • the spacer or extender provides an acute angle terminus for mounting the blade so that the axis of the blade does not Intersect the rotational axis of the wind turbine. The angle is inclined in the plane of rotation of the rotor.
  • the spacer is fixed to the rotor hub by means of a first flange and comprises a second flange for fixing the rotor blade thereto at an acute angle that opens away from the tower to provide increased clearance between the blade and tower under wind loads.
  • angling the rotor biade forward over its entire working length that is, using a forward cone angle over the entire blade length in a front running wind turbine makes the rotor extremely unstable and subject to vibration and flutter.
  • a blade of similar design to Wetzel et ai. included a torsional! 4 / rigid base, an inboard section having forward sweep comprising up to 25% of the blade's length, and an outboard section having aft sweep.
  • prior art aeroelastic designs necessarily employ inboard portions of the rotor having a thrust generating aerodynamic design. Because the innermost regions of the rotor have only minima! rotational speed, highly nonsymmetrical lift producing airfoil designs are employed in the inner most regions of the rotor in order to generate maximum power output, ideal forward sweep of the rotor, and high strength and rigidity to such regions of the rotor. Consequently, these regions of the rotor are required to use a highly asymmetrical airfoil design to produce maximum thrust. These airfoil designs are prone to movement of the center of wind pressure with varying wind angle of attack and speed, resulting in the generation of undesired flutter or induced vibration under changing wind conditions.
  • prior art aeroelastic rotor blades are designed such that the outer blade sections bend under norma! wind loads encountered during operation.
  • the ability of such blade designs to withstand additional or excessive loads under non-standard wind conditions is accordingly limited. That is, under operational conditions, blade bending movement is more limited in the positive (downwind) direction than it is in the negative (upwind) direction. This results in an undesirable asymmetric blade response to changing wind conditions and in operation causes movement in the center of thrust which induces unwanted vibration in the blade.
  • the present invention provides a blade adapted for use on a forward running wind turbine having an inner root section that is substantially rigid adapted for attachment to the wind turbine hub such that the aiignment axis of the root is disposed at an acute forward angle relative to a plane that is norma! to the axis of rotation of the hub (forward cone angle) and an outboard section of the blade such that the alignment axis of the outboard section or a portion thereof, is disposed at an aft acute ang!e relative to a plane that is norma! to the axis of rotation of the hub (aft cone angle).
  • root refers to the Innermost section of blade that is incapable of generating substantial amounts of lift or torque under operating conditions.
  • Preferred root sections of wind turbine blades for use herein do not possess a surface in the shape of an airfoil, excepting for purposes of drag reduction. Highly desirably they are incapable of generating more than 2 percent of total torque for the blade, more preferably, no more than 1 percent of total torque of the blade.
  • substantially rigid Is meant that no deformation results from torque forces and bending moments encountered during operation according to design specifications and deflection, if any, is inconsequential under the same conditions.
  • the present invention provides a b!ade according to the previous disclosure, wherein the aiignment axis of the blade root is also inclined at an acute forward angle with respect to the direction of rotation of the rotor about its rotational axis and the alignment axis of the outboard section is disposed at an acute receding angle with respect to the direction of rotation of the rotor about its rotational axis.
  • the invention provides a blade adapted for use on a wind turbine having a pitch axis, said blade having an inner root section that is substantially rigid adapted for attachment to the hub of the wind turbine and an outboard section, said blade being capable of providing a forward orientation of the alignment axis of the root relative to the pitch axis of the blade and an aft orientation of the alignment axis of the outboard section or a portion thereof, relative to said pitch axis.
  • the present invention provides a blade according to any of the previous embodiments wherein the blade, or a portion thereof, especially the root, Is bent or curved, such that the alignment axis of at least a portion of the outboard section is disposed at an aft acute angle relative to a plane that Is normal to the axis of rotation of the hub.
  • the present invention provides a blade according to the previous embodiment wherein the locus of the bend or curve occurs over the portion of blade located between 5 and 55 percent, preferably between 10 and 50 percent, more preferably between 15 and 45 percent of the total blade length from the root's proximal terminus.
  • the present invention provides a blade according to any of the previous embodiments wherein the outboard blade section is re!easably attached to the root or the blade is a single piece fiber or fabric reinforced laminate.
  • the present invention provides a blade according to any of the previous embodiments wherein the root section has a generally circular cross-sectional shape that is incapable of generation of substantial amounts of wind generated torque.
  • the present invention provides a blade according to an of the previous embodiments wherein the root section has a generally circular cross-sectional shape which tapers in diameter over a majority of the root's length.
  • the present invention provides a rotor for a wind turbine comprising a hub and at least one blade according to any one of the present designs.
  • the present invention provides a wind turbine that includes a rotor comprising a hub and at least one blade according to any one of the present designs.
  • the present invention provides a method for making a blade for a wind turbine comprising determining a blade shape by selecting axial alignment angles, size and shape for the root, and sizes, shapes, axiai aiignments, and optional sweep angles for the outer section of said blade so as to effectuate one or more of the following objectives: (a) decrease or eliminate shifts in centers of air pressure under varying air flow conditions experienced by the blade, (b) reduce or minimize an Increase in blade material necessary to maintain tip deflection within prescribed limits, (c) reduce or minimize negative effects on aerodynamics, especially reduce loads imposed onto the yaw control mechanism due to unstabilized blade design , (d) reduce or minimize pitching moment at the hub, especially under extreme weather conditions, or (ej maintain structural integrity and longevity under use conditions, and fabricating a blade in accordance with the determined blade shape.
  • FIG. 1 is an illustrative drawing of an airfoil shape.
  • FIG. 2 is a partial perspective view of an exemplary configuration of a forward running wind turbine of the present invention.
  • FIGs. 3a, 3b and 3c are side view drawings of exemplary separable root portions of blades suitable for use in the wind turbine configuration represented in FIG. 2.
  • FIG. 4 is drawing of a blade of the present invention suitable for use in the wind turbine configuration represented in FIG, 2.
  • FIG. 5 is a drawing of an alternate embodiment of blade configuration of the present invention having a bend or knee in the outer portion of the blade root.
  • FIG. 6 is a frontal view of an alternate embodiment of blade configuration of the present invention having non-radial alignment of the blade.
  • FIG. 7 is a drawing of a preferred blade airfoil shape for use in the outer section of a rotor according to the present invention.
  • FIG, 8 is a cross section drawing of one embodiment of the outer section of a rotor according to the present invention.
  • FIG. 9 is a partial front view of a rotor comprising a further alternate embodiment of blade configuration according to the present invention.
  • FIG. 10 is a top partial sectional view of a blade for use according to the invention comprising multiple segments.
  • FIG. 11 is a partial frontal view of a blade end in a further configuration of the present invention having improved aerodynamic properties.
  • FIG. 12 is a partial perspective view of a blade end fitted with a fin in a further alternate embodiment of the present invention having improved aerodynamic properties.
  • FIG. 13 is a partial frontal view of the blade end of FIG. 12.
  • airfoil refers to a closed curve, such as closed curve 100 depicted in FIG. 1, which represents the cross-sectional shape of an elongated surface (blade section) designed to produce lift when in contact with moving air.
  • Each airfoil shape likewise is elongated and the line connecting both extremities along the major dimension is referred to as the "chord”.
  • the median points between two respective points of the airfoil closed curve taken together form a curved segment called the "median line", with terminal points that are the same as the terminal points of the chord.
  • the working portion of a wind turbine blade comprises a series of such airfoil shaped cross-sections extending from the base to the tip or outer end of the blade section , the set of mid-points of the median lines thereof defining it's structural axis which Is a line for a fiat blade or a curve for a twisted or bent blade section.
  • the term " ' alignment axis" of the blade section or portion thereof refers to a line defined by the innermost and outermost median line mid-points of the biade section or portion thereof measured at full deflection under maximum operating conditions, the length of the blade section being the distance between the innermost and outermost median line mid -points.
  • the outer surface of the working blade is defined by the collection of curves from adjacent airfoil shaped cross- sections, the set of respective median lines of each airfoil shaped cross-section dividing said outer surface into two minor surfaces, a "high pressure” surface and a “low pressure” surface. Because airfoil shapes are often depicted with the chord arranged horizontally and the direction of wind proceeding relatively from left to right, the high pressure surface is often referred to as the "lower surface” and the low pressure surface is referred to as the "upper surface” regardless of the actual orientation of the working blade surfaces when in use.
  • a forward-running wind turbine 101 in some configurations comprises a nacelle 102 housing a generator and associated gearbox or alternative power transfer mechanism (not shown In FIG. 2).
  • Nacelle 102 is mounted atop a tall tower 104, only a portion of which is shown in FIG. 2.
  • Wind turbine 101 also comprises a rotor 106 that includes one or more rotor blades 108 (partially shown) attached to a rotating hub 110 having rotational axis S.
  • axis S is tilted up from horizontal from about 3 to 10 degrees, to lessen the effect of any bow wave emanating from the tower and to obtain more evenly balanced wind currents from top to bottom of the rotor ' s swept area since wind speeds close to ground level are often attenuated due to ground effect.
  • the direction of rotation of rotating hub 110 is indicated by arc D which is usually clockwise viewed from the front.
  • wind turbine 101 illustrated in FIG. 2 includes three rotor blades 108, there are no specific limits on the number of rotor blades required by the present invention.
  • the innermost portion of each blade, identified as 114 comprises the blade root.
  • the outermost segment of blade 108 is identified as segment 116 and comprises a suitable airfoil shape designed to produce thrust that causes rotation of rotor 106.
  • Nacelle 102 containing the rotor system, typically pivots about the vertical tower 104 to take advantage of wind from any direction.
  • the pivoting about this vertical-axis is known as yaw or yaw response and the vertical-axis is commonl referred to as the yaw-axis.
  • Effective yaw control of upwind horizontal axis wind turbines is highly desirable in order to position the rotor system properly relative to the mean wind direction.
  • the efficiency of the rotor system is significantly reduced.
  • an angle of separation develops between the mean wind direction and the axis of rotor rotation, the power output of the rotor system, and therefore of the turbine, decreases.
  • Various undepicted components of wind turbine 101 are housed in nacelle 102 and hub 110 atop tower 104.
  • Examples include a generator, drive train, bearings, braking system, yaw control mechanism, wind speed sensors, pitch control mechanism, and so forth.
  • one or more sensors and controllers comprise a control system used for overall system monitoring and control including pitch and speed regulation, high-speed shaft and yaw brake application, yaw and pump motor application and fault monitoring, electrical wave form modification and energy storage.
  • Hub 110 and blades 108 together comprise wind turbine rotor 106.
  • Rotation of rotor 106 causes a generator to produce electrical power, generally through a power transfer mechanism such as a gear box.
  • main bearings are provided both in front of and behind hub 110 to support the entire rotor weight while in operation.
  • Support for the forward bearing may be provided by a fixed quill (not depicted) supported from the main structural base of nacelle 102 and projecting through the center of hub 110 as is known In the art.
  • the pitches of blades 108 can be controlled individually by pitch control mechanisms located within the hub 110 (not depicted). Moreover, in one embodiment no pitch control mechanism is provided and blades 108 are fixed in spatial relation to hub 110. Yaw control of the nacelle 102 is employed for protection against over speeding of the generator and other mechanical parts.
  • wind turbines may be allowed to continue turning during high wind conditions, using yaw control to limit rotational speeds, thereby avoiding total shut down of the turbine.
  • the blades of the present invention may be manufactured as a single unit, for purposes of ease of transportation and manufacture, the root and blade are desirably manufactured separately and assembled into a single combination blade unit or rotor at the wind turbine erection site.
  • the present invention comprises a separable blade root 114a having proximal terminus 201a adapted for attachment to the rotor hub and a distal terminus 202a adapted for attachment to the base of blade section 116 thereby forming combination blade 108.
  • A is the alignment axis of the root defined as a longitudinal line connecting the geometrical centers, CI and C2, of the proximal and distal terminal surfaces.
  • the length of root 114 is the distance between respective geometrical centers of the outer faces of proximal terminus 201a and distal terminus 202a, Although flanges are depicted in FiG, 3a for attachment to the rotor hub and blade section 116 using, for example, bolts or other attachment means, it is to be understood that any suitable method of attaching both termini, such as interlocking clasps; a socket and corresponding fitment; stud bolts bonded, molded, or otherwise inserted Into either the hub, root or blade section base; or other suitable mechanism may be employed for joining the respective portions of the rotor, it only being requisite that both ends of root 114 are shaped or adapted for attachment so that when attached to the wind turbine hub the root's alignment axis is tilted forward relative to a plane that is normal to the axis of rotation of the hub thereby providing a forward cone angle for the root, and the blade section's alignment axis is tilted aft relative to a plane that is also normal to
  • the reverse cone angle where the root and blade are joined is due, at least in part, to off-axis alignment between the structural axis of the innermost one percent length of blade 116 and alignment axis A.
  • FIG 3b discloses an alternative embodiment of separable root 114b which tapers in cross-sectional size from proximal terminus 201b to distal terminus 202b. Tapering reduces the total mass of the blade and is highly desirable for this reason.
  • a blade root having circular cross-sectional shape may have a diameter at the proximal terminus of about 5 m while the diameter at the distal terminus may be about 4 m. in general, all joints or surface transitions on the blade or joining the blade with the hub are chamfered, rounded, filleted, beveled or fairings are placed over any protruding or receding sections of various rotor components to Improve aerodynamic performance.
  • FIG 3c discloses yet another embodiment Illustrating root 114c having proximal terminus 201c fitted with numerous stud bolts 205c placed in a circular pattern and located near the circumference of proximal terminus 201c for attachment to a hub.
  • a bend 112 in root 114c imparts aft axial alignment to a blade section attached to distal terminus 202c.
  • Alignment axis A includes the geometrical centers CI and C2 of the proximal and distal terminal outer surfaces.
  • the proximal and distal termini in general are shaped so that their faces conform in size and shape to the corresponding attachment surface, that is, either the corresponding hub or blade section face.
  • forward cone angle may be produced using roots of the invention having proximal terminal surfaces disposed at angles other than 90 degrees to the alignment axis of the root, by the use of hubs having attachment mechanisms imparting a forward cone angle to a root having proximal terminal surface oriented normal to the alignment axis of the root, by the presence of one or more longitudinal curves or bends in the root body, or by a combination of the foregoing methods.
  • aft cone angle may be produced by attachment of a blade having an angled attachment face to a separate root having a distal terminus disposed perpendicularly to the alignment axis of the root.
  • rotor blades 108 attached to hub 110 of a wind turbine comprise root 114 aligned along alignment axis A oriented forward, that is up wind, relative to a plane N normal to the axis of rotation S.
  • An optional conventional pitch control mechanism (not depicted) is located within hub 110 and Is attached to the base of root 114 to provide pitch control of blade 108 aiong pitch axis P.
  • Forward alignment of the root as disclosed herein may aiso be referred to as providing a forward cone angle to blade root 114, due to the fact that upon rotation of hub 110, the blade root describes a cone having its apex along the axis of rotation of the hub and its base in front or upwind of the rotor.
  • the angles by which alignment axis A departs from a plane N define forward cone angle c of root 114.
  • a pitching moment of blade 108 at the base of root 114 is reduced or eliminated due to aft alignment of outer blade section 116.
  • aft axial alignment of blade segment 116 is depicted by aft cone angle c', which is the acute angle by which A ' , the alignment axis of blade segment 116, departs from a plane N', a plane that is parallel to plane N.
  • forward cone angle c is greater than pitch angle p, which is the angle, if any, between P, the pitch axis of the rotor and plane N.
  • the forward cone angle c of the present invention is at least 1 degree, preferably at least 7 degrees, more preferabl at least 12 degrees, desirably at least 15 degrees, highly desirably at least 16 degrees, and most desirably at least 18 degrees.
  • the forward cone angle c of the present invention is at most 45 degrees, preferably at most 40 degrees, more preferably at most 38 degrees, and highly desirably no more than 35 degrees.
  • Desirable ranges for aft cone angle c are at least 1 degree, more desirably at least 3 degrees, highly desirably at least 5 degrees, and most desirably at least 6 degrees; and a maximum of 10 degrees, more desirably a maximum of 9 degrees, and most desirably a maximum of 8 degrees.
  • the pitch angle p of the present invention Is between 0 degrees and 10 degrees, preferably from 2 degrees to 9 degrees and most preferably from 3 degrees to 7 degrees.0044]
  • the respective lengths of root 114 (g) and blade section 116 (g'), are selected so as to produce a desirable reduction of stress at the hub and of pitching moment experienced by the drive components.
  • the root length, g is a minimum of at least 5 percent of g' " , the length of blade 116, more preferably 10 percent, and most preferably 20 percent.
  • the root maximum length is 50 percent of g', more preferably 45 percent, and most preferably 40 percent
  • the pitch angle, fore and aft cone angles, and respective lengths of root 114 and blade 116 are selected such that the pitch axis P intersects the structural axis of blade section 116 at a point that produces minimal rotational moment, preferably at or near, that is, no more than 5 percent of blade section length from the center of mass of combination blade 108. Highly desirably, this point of intersection is from 25 to 50 percent of g' from the base of blade section 116.
  • Suitable blade lengths for use herein are from 20 m to 200 m, preferably from 30 m to 100 m.
  • One specific application may employ a rotor diameter of about 110 m, and have a total swept area of 10,000 m 2 or more.
  • the blades according to the invention possess improved aerodynamic properties due to the absence of any surface that might cause flat plate vortex generation and flutter under certain wind conditions. Also, the sudden arrival of an advancing storm generated wind gust or wall of hail from a storm does not impact the entire blade length simultaneously, possibly causing structural failure of the blade or rotor.
  • An additional and unexpected benefit that is believed to result from the present design is greater visibility to birds. Because the outer portion of the spinning rotor is raked or inclined with the wind direction, soaring birds are likely to encounter a smaller portion of the blade sweep before becoming visually aware of the rotating blade.
  • roots 114 are highly rigid with respect to both torsional and bending forces, desirably having an elastic limit that is at least three times, preferably at least four times, the maximum stress expected under operational conditions (design limit).
  • Suitable materials of construction include glass fiber, carbon fiber, polyaramide fiber, or other high strength fiber or fabric reinforced resins and laminates comprising the same, as well as metals, especially aluminum, titanium or steel alloy castings or forgings. Because the latter materials are easier to fabricate than laminates or fiber reinforced resinous materials, their use for constructing the present roots Is preferred.
  • the blades of the present invention have the advantage in that worn or damaged outer blade sections 116 may simply be replaced at reduced cost and inconvenience than is the case with the use of larger single piece blades. Construction, transportation and field mounting are also simplified due to reduced size and weight of the portion of the blade that needs to be replaced.
  • the use of high strength metals as the materials of construction also allows the diameter or thickness of the root to be substantially reduced, or at least the longitudinally outer most portions thereof to be tapered, thereby reducing overall weight of the rotor and providing less aerodynamic drag.
  • the cross-sectional shape of roots 114 is unlimited and specifically may include an airfoil shape, for simplicity of construction and ease of assembly, root 114 desirably has a cross-sectional shape that is incapable of generation of substantial amounts of wind generated torque or power.
  • the cross-sectional shape of root 114 is desirably circular, oval, tear-drop, or ellipsoidal shaped. Furthermore, said diameter or major axis, at least at or near the outer terminal portion thereof, is desirably less than the diameter or major cross-sectional axis length of the innermost terminal portion of outer blade 116, not counting any mounting or fastening apparatus.
  • root 114 is tapered, that is, it has a generally gradually decreasing diameter or cross-sectional major and minor axis measurements over a majority of the distance from the inner to the outer ends thereof (not counting any larger sized distal terminus and corresponding adjoining radii).
  • root 114 is circular in cross-sectional shape over a majority of it's length.
  • the roots of blades according to the present invention may be designed purely for strength and not airfoil shaped to produce thrust, cheaper materials of construction, such as steel or aluminum, may be employed for the blade root.
  • Suitable aluminum alloys for use especially include high strength alloys such as 6000 or 7000 series alloys (Internationa! Alloy Designation System), and scandium containing alloys. Larger effective blade lengths (counting root and blade section), the components of which are more durable and easily transported than single piece units, with little compromise of performance or even improved performance are obtainable.
  • blade 108 may include a curved or bent region 112 in root 114, leading to an aft acute angle of attachment for blade section 116.
  • the shape and size of distal terminus 202 is selected based on various criteria including the presence of attachment means for assembly of blade 116, aerodynamic concerns, or other
  • blade section 116 may also include one or more curves or bends, if desired,, and the resulting blade may include both curved root 114 and curved blade section 116 without departing from the scope of the present invention.
  • the locus of a bent or curved portion of a blade is defined as the point along the structural axis where a plane that is norma! to the axis of rotation is also tangential to said structural axis.
  • an alternative point, the geometric centroid of the root ' s distal terminal surface is employed as the locus.
  • Configurations of the present invention can be applied to an existing wind turbine by replacing conventional blades with blade configurations of the present invention without the need for expensive upgrades of pitch drive hardware. Furthermore, use of reduced diameter or cross-sectional sized roots, when comparing distal regions to proximal regions thereof, according to the present invention results in improved aerodynamic performance of the resulting rotor design as well as increased blade longevity due to reduction in harmful pulsation and vibration generation under operating conditions or high wind conditions. Additional benefits include reduction in acoustic vibrations (noise) as well as the abilit to operate safely at higher wind velocities thereby allowing power generation over wider ranges of wind conditions. Highly desirably, the foregoing benefits are obtained in designs of the present invention wherein pitch axis P intersects the structural axis of outer blade section 116 at a point that Is between 25 and 50 percent of the length of outer blade section 116.
  • root 114 of blade 108 is attached to hub 110 such that the root alignment axis A, is aligned with the hub in a leading angle, f, with respect to radial line R, a line intersecting S and located in a plane that is norma! to S. Accordingly, alignment axis A is disposed either axiai!y (not depicted) or in a forward inclination with respect to the direction of rotation.
  • the distal terminus of root 114 is adapted such that the alignment axis A' of blade 116 is oriented backward with respect to the direction of rotation D of the wind turbine thereby defining an angle f with respect to radial line R. in such design, reduced stress at the blade base and improved stability of the rotor is achieved.
  • the angles of forward inclination f may range between 0 degrees and 10 degrees, preferably from 0 degrees to 8 degrees, more preferably from 0 to 7 degrees, and highly desirably from 0 to 5 degrees.
  • Desirable ranges for backward orientation f are from 1 to 12 degrees, more desirably from 2 to 10 degrees, and most desirably from 2 to 8 degrees, in a most preferred embodiment, a plane containing radial line line R and rotational axis S (not depicted in FIG.6) intersects the structural axis of blade section 116 at or near the center of mass of combination blade 108. By near is ment the intersection point is within 5 percent of total blade length from said center of mass.
  • the outer segment 116 comprises the working airfoil of blade 108.
  • one suitable airfoil shape is depicted for a sample cross-section of segment 116 showing the upper or low pressure surface and bottom or high pressure surface of the airfoil.
  • highly asymmetrical airfoil designs are avoided, especially an airfoil design having negative camber in the trailing half of the blade, due to the large amount of drag created during usage and large shift in center of lift under varying wind conditions.
  • a modestly asymmetrical airfoil design such as a NACA 4412, or a Grant X series airfoil shape, or Grant X- 8 through Grant X-10, (c.f., Charles Hampson Grant, Model Airplane Design and Theory of Flight, Jay Publishing Corporation. New York, 1942, pg. 27).
  • Characteristics include a chord length X, that is the distance between front and rear chord starting points, half chord point f, half chord length, X f , point of maximum chord diameter d, and length at maximum chord diameter, X d .
  • the shape of the airfoil joining upper and lower surfaces at the front leading edge is a partial circle having radius r ⁇ .
  • the ratio of ⁇ /d is from 1/5 to 1/20, most preferably from 1/6 to 1/10.
  • r N is relatively small, ideally from 10 to 50 mm, more preferably from 12 to 30 mm.
  • blade section 116 has a substantially constant chord length and airfoil shape, a substantially straight taper, or a combination of such shapes over at least the inner most 85 percent of blade section length, preferably at least the inner most 90 percent of blade section length.
  • the leading edge of the outer blade section substantially conforms to a straight line and the blade is twisted such that the outer most blade section leading edge has a reduced angle of attack with respect to the effective wind direction.
  • desirable airfoil designs include those having a center of lift close to the structural center of the blade as well as close to the center of mass thereof, more desirably between Xd and Xf, By close, is meant that the center of lift under working conditions is desirably within 10 percent of total chord length from the position on the chord closest to the airfoil's cross-sectional center of mass.
  • the blade is designed and constructed of materials selected to provide a center of mass that is forward of the structural or geometric center of the blade as well as forward of the midpoint of the chord as well as the midpoint of the median line.
  • the blade includes a box beam or other structural member to carry loads the axis of which is centered along the structural axis of the blade or at least parallel thereto.
  • FIG. 8 shows a cross-section of a suitable laminated working blade section 116 for use according to the invention having internal structural components 130 forming a box beam and outer surface skin 131 forming the lower and upper surfaces of the blade, the laminated structure forming a single mass.
  • Suitable materials of construction include, without limitation, glass fiber, carbon fiber, poiyaramide fiber, or other high strength fiber or fabric reinforced thermosetting resins, especially epoxy resins.
  • the method of construction is controlled such that the center of mass of the resulting structure is located at a point forward of the center point of the chord,, without addition of metal rods or beams in the front interior portion of the blade.
  • additional mass may be included in the forward half of blade segment 116 by the inclusion of a metal rod or shaft 132.
  • this metal rod is steel or brass and is located in an extreme forward portion of the blade, especially adjacent to the leading edge of blade section 116, or within 10 percent of the total chord distance from the leading edge, most preferably within 5 percent of the total chord length from the leading edge of blade section 116.
  • multiple rods or shafts may be included in the blade design, and if extending longitudinally end to end within the blade segment, are desirably joined into a single structure, such as by welding or brazing adjoining ends, to increase blade rigidity.
  • rod or shaft 132 is long enough or multiple rods are joined together to extend for at least the outer 40 percent, preferably 50 percent, and most preferably 70 percent of the length of blade segment 116. Due to the concentration of mass in the present blade design in the stated forward position with respect to the structural axis of the blade, centrifugal forces generated by the blade rotation serve to partially or fully offset wind generated bending forces experienced by the rotating blade, leading to reduced stress and improved longevity of the present blade design. 0055] Referring to FIG.
  • blades 108 which include blade section 116 which may be slightly tapered over all or a portion thereof, and which terminates with a relatively highly tapered outer end, 220 having length g", starting at a point 223 on the leading edge of the blade.
  • the relatively highly tapered section 220 is only- tapered on the leading edge of the blade. That is, the width or chord length of blade section 116 decreases, preferably linearly, from front to back proceeding longitLidinally outward over the remaining length g' of the blade section with the trailing edge remaining substantially In line with the trailing edge of the remainder of the blade section.
  • the length of relatively highly tapered section 220 that is, g" is desirably from 5 to 12 percent of g', the length of blade segment 116, more desirably from 6 to 10 percent, in one desirable configuration, the width of tapered outer end 220 at its outer extremity is from 75 percent to 50 percent of its initial width.
  • the presence of tapering on the outer extreme end of blade section 116 is desirable due to formation of a discontinuity in the leading edge a point 223 which causes vortices to be shed outward,, especially at high angles of attack, resulting in a reduction in blade pulsation, oscillation, or vibration generation and improved aerodynamic performance. Additionally, ice build-up is more readily shed from the blade by the presence of an angled leading edge of blade section 116 after point 223.
  • the cross sectional size of root 114 near distal terminus 202 may be smaller than the cross-sectional size of blade 116 near it's base, causing a discontinuation 206 where the leading edge of blade 116 joins root 114. That is, when viewed in profile, the leading edge of the blade, or at least the innermost portion thereof, describes a line or curve that, if continued in the direction of the root, does not intersect the root's forward edge. This desirably acts as a vortex generator, leading to improved aerodynamic response of the blade as changing wind conditions or gust Induced air-stream separation is more likely to initiate at the base of blade section 116 rather than further outward and is less likely to induce vibration and flutter in the blade.
  • root 114 is tapered and hollow.
  • a protective surface cover or coating 140 applied or bonded to some or ail of the leading edge of blade segment 116, for example sheet metal such as copper, brass, tin, stainless steel, or steel. Desirably, the cover or coating is applied to at least the outermost 10 to 20, more preferably 10 to 50 percent of the blade length.
  • the coating may also comprise a durable, non-metallic hard surface such as ceramic or other impact resistant material. The purpose of the protective surface cover or coating is to protect the blade leading edge from impact with hail or other hard objects as well as to increase the mass located forward of the structural center of the blade.
  • the leading edge surface for a distance from 1 to 10 percent of total distance to the trailing edge above and below the blade center line is covered by the protective surface coating.
  • the leading edge surface covering if conductive, may also be grounded, through connection to a suitable grounding point (not illustrated).
  • a suitable grounding point not illustrated.
  • the blade root of the Invention must itself be conductive and grounded or include therein a conductor connected to ground for completion of the grounding circuit with surface cover 140 In this embodiment of the invention.
  • the point identified as 224 marks an inflection point on the high pressure surface of the outer blade section where an optional sloping end cap begins.
  • FIG. 10 there is depicted a blade comprising multiple sections 116a, 116b and 116c, comprising a protective coating 140a, 140b and 140c respectively, on the surface of the leading edge of one or more blade segments.
  • the leading edge of each segment describes substantially a straight line however, each succeeding section proceeding outward toward the blade tip progressively narrows due, at least partially, to slight angling of the leading edge.
  • the difference in angle of the leading edge between two representative segments is indicated by q, the amount by which two adjacent blade segments differ in outer blade width.
  • the skilled artisan will appreciate that the amount by which adjacent blade segments differ in width may or may not be constant and the numbers of such segments per blade is not limited, but is preferably a number from 3 to 10.
  • Each segment length likewise is variable and the portion of the blade in which such segmented construction occurs is desirably at least the outer most length of the blade, most preferably at least the outermost 25 percent, more preferably the outermost 50 percent, and most preferably the outermost 75 percent of blade length.
  • sheet metal may be readily shaped to conform to the leading edge, with the entire blade thereby approximating a curved leading edge over the course of its length.
  • Preferred metals for use in this embodiment of the invention include aluminum, steel, galvanized steel, brass or titanium.
  • the distal portion of blade section 116 terminates in a sloped end piece or cap 222 starting on the high pressure side at previously identified point 224 on the blade section surface and in a plane perpendicular to the structural axis and terminating on the low pressure side.
  • the angle at which the sloped end piece 222 is inclined with respect to the structural axis is indicated by angle t.
  • t is an angle from 30 to 60 degrees, more preferably from 40 to 50 degrees, and most desirably 43-47 degrees.
  • the purpose of slopping the end of blade section 116 by means of end cap 222 is to allow gradual recombination of high and low pressure air streams and also to cause the ensuing vortex to be directed outside the radius of the spinning rotor. This greatly reduces flutter, vibration and noise generation by the spinning turbine rotor.
  • the point 22.4 is located at approximately 85 to 99 percent of the distance of g' starting at the base of blade section 116, most desirably from 87 to 98 percent of the distance g'.
  • blade end 222 need not form a flat surface as depicted, but may also be a rounded or curved surface, without departing from the scope of the invention.
  • blade end 222 comprises a fin 225 which, with respect to its point of attachment to blade 116, projects both outward (above) and behind the trailing portion of blade 116 on the low pressure side thereof and terminates in an apex 226 located outward and behind the trailing edge of blade segment 116.
  • fin 225 extends above the upper surface of blade 116 for a distance that is from 10 to 50 percent of the blade thickness measured at point 224, and extends behind the trailing edge of blade 116 for a distance that is from 2 to 10 percent of the blade chord length measured at point 224.
  • fin 225 causes the vortex formed upon recombination of high and low pressure air masses on opposite sides of blade segment 116 to be directed further outside and behind the blade than is obtainable with only a sloped blade end, to thereby further reduce pulsation, oscillation, or vibration generation by the rotor blade.
  • fin 225 is also conductive and is grounded by means of a conductor 227 which is connected through the blade to a suitable grounding source and connected to fin 225 by an electrically conductive connector 229. Due to rotation of the turbine rotor, conductor 227 may ultimately require connection to ground via a commutator or other rotating electrical connection (not depicted) within the turbine hub in order to form a suitable connection to fin 225.
  • An additional advantage of inclusion of electrical conductor 227 is to provide additional mass in the forward portion of the blade as previously discussed.
  • conductor 227 is securely attached within the interior of blade 116 within 20 percent, preferably within 15 percent of total chord length from the leading edge of the blade.
  • the entire blade segment 116 or a portion thereof may be formed of conductive materials such as aluminum or steel and suitably attached to conductive fin 225 and a grounding source to thereby effectively ground fin 225.
  • Suitable materials of construction of conductive fin 225 include metal, especially steel, brass or aluminum, as well as electrical conductive laminated materials such as the previously mentioned metal mesh reinforced laminated materials.
  • the thickness of fin 225 may vary within wide tolerances, but generally is from about 2 to 20 mm in maximum thickness. Although depicted as a flat plate with squared off edges, the skilled artisan will appreciate that fin 225 ma be rounded or curved on its edges, sides and surfaces as well as embossed, engraved, grooved, or otherwise shaped If desired.
  • the ends of the blade may include holes to allow inspection of the blade Interior, drainage of water or other accumulated liquids, or internal pressure relief as well as projections for purposes of lightening reception and conduction, or other use.
  • the purpose of providing a grounded fin is to enhance dissipation of static electricity from the blade section surface through a corona discharge from the tips of the blades, thereby reducing the incidence of damage to the blade section due to lightning strikes.
  • a metallic covering for impact protection of the leading edge of the blade section which also serves as at least a portion of the electrical grounding circuitry, an additional desirable benefit to the present design Is achieved, since an internal conductor or wiring is not required to be included within the blade itself, or a smaller sized grounding conductor may be employed.
  • the root of the invention must itself be conductive and grounded or include therein a conductor connected to ground for completion of the grounding circuit with fin 225 in this embodiment of the invention.
  • the root is electrically conductive and serves partially or wholly as a lightening strike ground conductor or a static discharge ground conductor.
  • the working blade section of the present wind turbine blades may include a lengthwise twist to better match the airfoil to the apparent wind angle. This ideally allows the outermost regions of the blade to maintain thrust under reduced wind speeds or varying wind conditions thereb avoiding vibration or flutter inducing conditions. All of the previously disclosed modifications to blade design including longitudinal and cross-sectional tapering and fin placement also contribute to the foregoing Improved aerodynamic properties.
  • additional linkages such as cables, spars or tensioning stays may be incorporated to join the forward most regions of blades disclosed herein thereby more evenly distributing centrifugal forces within the rotor.
  • a wind turbine having a rotor equipped with three blades having a design rating of 8 Mw.
  • the blades are comprised of roots of circular cross-section 2.4 m long, with proximal diameter 3.7 m, distal diameter 2.0 m, disposed at a 20 degree forward alignment angle (forward cone angle).
  • the working blades are 56 m long and disposed at 7 degree aft alignment angle (aft cone angle).
  • the axis of rotation is tilted up approximately 5 degrees.
  • Blade tip clearance in front of the base is approximately 7 m, and blade loading is 122 kg/m 2 .
  • a forward running wind turbine having a rotor comprising a hub and one or more blades having an Inner root section that is substantially rigid adapted for attachment to the hub of said wind turbine such that the alignment axis of the root is disposed at an acute forward angle (cone angle) relative to a plane that is normal to the axis of rotation of the hub and an outboard section of the blade such that the alignment axis of the outboard section is disposed at an aft acute angle relative to a plane that is norma! to the axis of rotation of the hub.
  • a turbine according to embodiment 1 wherein said forward cone angle is from 1 to 45 degrees.
  • a turbine according to embodiment 1 wherein said forward cone angle is from 12 to 40 degrees. 4. A turbine according to embodiment 3 wherein said aft acute angle Is from 3 to 9 degrees.
  • a turbine according to embodiment 9 wherein the root section is circular in cross- sectional shape over a majority of it's length and is tapered.
  • a turbine according to embodiment 1 wherein the length of the root section is from 5 to 50 percent of the length of the outer blade section.
  • a turbine according to embodiment 1 wherein the outer section has an airfoil cross sectional shape and the center of mass of each cross sectional shape Is located at a point forward of the center point of the chord thereof.
  • a turbine according to embodiment 1 wherein the blade comprises a single piece fiber or fabric reinforced laminate.
  • a blade adapted for use on a forward running wind turbine having an inner root section that is substantially torsiona!ly rigid adapted for attachment to the hub of said wind turbine such that the alignment axis of the root is disposed at an acute forward angle (cone angle) relative to a plane that is normal to the axis of rotation of the hub and an outboard section of the blade such that the alignment axis of the outboard section is disposed at an aft acute angle relative to a plane that is normal to the axis of rotation of the hub.
  • a blade according to embodiment 21 wherein said forward cone angle is from 1 to 45 degrees.
  • a blade according to embodiment 22 wherein said forward cone angle is from 12 to 40 degrees.
  • a blade according to embodiment 23 wherein said forward cone angle is from 16 to 38 degrees.
  • a blade according to any one of embodiments 21-24 wherein said aft acute angle is from 1 to 10 degrees.
  • a blade according to embodiment 25 wherein said aft acute angle is from 3 to 9 degrees.
  • a blade according to embodiment 26 wherein said aft acute angle is from 6 to 8 degrees.
  • a blade according to embodiment 38 wherein the ratio of r N /d is from 1/6 to 1/10.
  • a blade according to embodiment 41 wherein the length of the root section is from 20 to 50 percent of the length of the outer blade section.
  • a blade according to embodiment 46 wherein the protective surface cover is sheet metal.
  • a blade according to embodiment 49 wherein the final width at the tip is 50 to 75 percent of the initial width of said outer section
  • a blade according to embodiment 52 wherein the sloped end comprises a fin which, with respect to its point of attachment to the outer blade section, projects both outward and behind the trailing portion of the blade on the low pressure side thereof and terminates In an apex located outward and behind the trailing edge of blade section.
  • a rotor for a forward running wind turbine said rotor having a hub and at least one blade according to any one of embodiments 21-55,
  • a wind turbine comprising a rotor according to embodiment 56.
  • a wind turbine comprising a rotor according to embodiment 40,

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  • Sustainable Energy (AREA)
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Abstract

Turbine éolienne comprenant un rotor possédant un moyeu et au moins une pale conçue pour être fixée audit moyeu à l'aide d'une emplanture de manière à créer une orientation axiale vers l'avant de l'emplanture par rapport à un plan qui est perpendiculaire à l'axe de rotation du moyeu et une section extérieure de la pale ayant une orientation axiale arrière par rapport à un plan qui est perpendiculaire à l'axe de rotation du moyeu.
PCT/US2015/044561 2014-10-11 2015-08-11 Pale de rotor de turbine éolienne comprenant une emplanture avec axe vers l'avant WO2016057110A1 (fr)

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PCT/US2015/044131 WO2016057107A1 (fr) 2014-10-11 2015-08-07 Dispositif d'espacement pour pale de rotor de turbine éolienne
PCT/US2015/044561 WO2016057110A1 (fr) 2014-10-11 2015-08-11 Pale de rotor de turbine éolienne comprenant une emplanture avec axe vers l'avant
PCT/US2015/045600 WO2016057120A1 (fr) 2014-10-11 2015-08-18 Entretoise pour pale de rotor de turbine éolienne

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CN114761195A (zh) * 2019-10-07 2022-07-15 维斯塔斯风力系统有限公司 用于制造风力涡轮机叶片的改进方法
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CN113107759A (zh) * 2021-04-21 2021-07-13 远景能源有限公司 叶片扫塔预防装置及其安装方法、风力发电机
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WO2024017673A1 (fr) * 2022-07-21 2024-01-25 Siemens Gamesa Renewable Energy A/S Pale de rotor d'éolienne

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