WO1992001865A1 - Wind turbine blade and rotor incorporating same - Google Patents

Wind turbine blade and rotor incorporating same Download PDF

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Publication number
WO1992001865A1
WO1992001865A1 PCT/GB1991/001265 GB9101265W WO9201865A1 WO 1992001865 A1 WO1992001865 A1 WO 1992001865A1 GB 9101265 W GB9101265 W GB 9101265W WO 9201865 A1 WO9201865 A1 WO 9201865A1
Authority
WO
WIPO (PCT)
Prior art keywords
wind turbine
blade
span
turbine blade
aerofoil
Prior art date
Application number
PCT/GB1991/001265
Other languages
French (fr)
Inventor
Peter Mckeich Jamieson
Original Assignee
Howden Wind Turbines Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Howden Wind Turbines Ltd. filed Critical Howden Wind Turbines Ltd.
Publication of WO1992001865A1 publication Critical patent/WO1992001865A1/en

Links

Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03DWIND MOTORS
    • F03D1/00Wind motors with rotation axis substantially parallel to the air flow entering the rotor 
    • F03D1/06Rotors
    • F03D1/0608Rotors characterised by their aerodynamic shape
    • F03D1/0633Rotors characterised by their aerodynamic shape of the blades
    • F03D1/0641Rotors characterised by their aerodynamic shape of the blades of the section profile of the blades, i.e. aerofoil profile
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05BINDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00Components
    • F05B2240/20Rotors
    • F05B2240/30Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor
    • F05B2240/301Cross-section characteristics
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/70Wind energy
    • Y02E10/72Wind turbines with rotation axis in wind direction

Definitions

  • the wind turbine rotor in accordance with the present invention uses a plurality of aerofoil section blades having this characteristic and set at an appropriate incidence with respect to the rotor hub so that wind passing through the rotor disc will generate a rotation force on the blades which exceeds any drag component and therefore maintains the rotor in rotating motion with adequate power extraction from the kinetic energy of the wind.
  • Figure 3 shows a third form of blade section in accordance with the present invention in which the high camber trailing part of the aerofoil section is again relatively smoothly integrated with the front part of the chord but now there is a slot 5 between the main part 6 of the aerofoil and the trailing part 7. The existence of this slot 5 further increases the C- ⁇ max value and results in an increased C-T/C Q ratio.

Abstract

A wind turbine blade has an aerofoil section resembling that of an aircraft wing with a high lift device (for example a slotted flap (7) defining a slot (5)). The wind turbine rotor is provided with a plurality of such blades set at an appropriate angle of incidence so that the blades are operating close to the stalling angle. The blade cross-section has a CL?/CD? of at least 75, and a CL?max of at least 1.8 at a stalling angle of no more than 12.

Description

WIND TURBINE BLADE AND ROTOR INCORPORATING SAME
The present invention relates to a rotor blade for a wind turbine, and to a wind turbine rotor incorporating such blades. It is known that the performance coefficient Cp of a wind turbine rotor is greater when the aerofoil used is one which has a high lift to drag ratio (C*/CD) . Traditionally the aerofoils used for such high C-T/CQ wind turbine blades are carefully designed so as to offer high lift to drag ratios in the "clean" configuration (without the operation of any high lift devices or deflection of any camber flaps) .
It is also known to provide high lift devices to augment the lift of an aircraft wing aerofoil in the landing and take-off configurations (particularly with regard to landing) , in order to allow the speed to be reduced without loss of lift. This implies both high angles of attack and high CL by virtue of deployment of the lift augmentation means. However, normal cruising flight will reguire the aerofoil to be in its clean configuration. Traditionally the designers of both lift surfaces and stabilizer surfaces on aircraft and of wind turbine blades have striven for optimum performance of the aerofoil in its clean configuration. In the case of the aircraft designer, he has the knowledge that he can rely on lift augmentation devices for landing and take-off; the wind turbine designer has no need for such measures as the rotor is designed to operate only in its cruising mode (clean configuration) .
According to the present invention we now provide a wind turbine blade having a tip and a root end, in which over at least half of the span the aerofoil section of the blade is one having a C-*-/CD ratio of at least 75 and a C^max of at least 1.8 at a stalling angle of attack which is less than or equal to 12°. The invention also relates to a wind turbine rotor incorporating a plurality of such blades mounted for rotation about an axis, and set with an angle of incidence appropriate to allow the blade to operate close to its stalling angle of attack when rotated by wind passing through the rotor disc. In order that the present invention may more readily be understood the following description is given, merely by way of example, reference being made to the accompanying drawings, in which:-
FIGURE 1 is a section of an aerofoil of a wind turbine blade in accordance with the present invention, the aerofoil being designed to have a section similar to that of a conventional integral aerofoil with a camber flap deflected to an incidence of +20°;
FIGURE 2 is a section of an alternative aerofoil in which the trailing part of the aerofoil section has been designed with a more curved form, but again with a very high camber portion reminiscent of the deflected camber flap shown in Figure 1; and
FIGURE 3 is a view similar to Figure 2 but showing a slot through the aerofoil section making the high camber trailing part of the aerofoil section operate in the manner of a slotted trailing edge flap.
As indicated above, the present invention provides an aerofoil section wind turbine blade adding a high lift configuration reminiscent of an aircraft wing in its landing or take-off configuration, but fixed with such high lift configuration for all operating regimes. Figure 1 shows the blade 1 as having the usual rounded nose 2 and a deflected trailing edge portion 3 reminiscent of a plain aircraft wing flap or an aileron, at positive incidence (deflected downwardly) . The wind turbine rotor in accordance with the present invention uses a plurality of aerofoil section blades having this characteristic and set at an appropriate incidence with respect to the rotor hub so that wind passing through the rotor disc will generate a rotation force on the blades which exceeds any drag component and therefore maintains the rotor in rotating motion with adequate power extraction from the kinetic energy of the wind.
Whereas the aircraft designer traditionally aims for high lift without being too concerned about the drag in the landing configuration (although he may to some extent aim for avoiding high drag in the take-off configuration and will certainly aim for optimum C;Q/CD in the cruising configuration for considerations of power consumption) , we now propose to use the aerofoil section in its high lift configuration throughout the operating regimes of the rotor, and to aim for a high Cj*/CD ratio in this high lift configuration. By "high lift to drag ratio" or "high CL/CD" we mean ratios of at least 75.
We aim for a maximum C- , of at least 1.8, when the aerofoil is at its stalling angle of attack, and we aim that this stalling angle should be no greater than 12°.
Traditionally the aircraft designer will aim for a high stalling angle in order to allow the aircraft to he operated with maximum safety on take-off and landing and when manoeuvring at low speeds on the approach path, whereas we aim to keep the stalling angle low so that in normal operation the wind turbine blade is close to its stalling angle and this enables the wind turbine to be operated safely in that in the event of wind gusts there will be no overspeed of the rotor because its blades will already be working near the stalling angle and they will simply stall due to the changing angle of attack resulting from the high wind speed.
This feature of operating near the stall is quite different from the considerations of aircraft design where avoidance of the stall in cruising flight makes it necessary to operate well below the stalling angle, and where a high lift configuration in cruising flight will mean that there are no means of still further augmenting lift for landing. Figure 2 shows an aerofoil which has a camber similar to that of Figure 1 but is more smoothly curved so that the "permanently deployed high lift device" comprising the high camber trailing section is more smoothly integrated with the front part of the chord of the aerofoil. Clearly, such an aerofoil would be of no use to the aircraft designer because of the inability of an aerofoil with such a permanently high camber section to cruise effectively. However, for a wind turbine rotor blade with such a cross- section operates effectively close to the stalling angle and with its high C*/CD ratio and high CLmax value at stall. Figure 3 shows a third form of blade section in accordance with the present invention in which the high camber trailing part of the aerofoil section is again relatively smoothly integrated with the front part of the chord but now there is a slot 5 between the main part 6 of the aerofoil and the trailing part 7. The existence of this slot 5 further increases the C-^max value and results in an increased C-T/CQ ratio.
Still further forms of permanently deployed high lift devices may be found to give the desired C- CΓJ ratios of at least 75 and a C-^max value of at least 1.8. For example, a leading edge slat may be found to give the desired results, or possibly a permanently deployed leading edge flap may be used.
Effectively, the wind turbine blade in accordance with the present invention has a cross-section along the majority of the blade span which resembles that of an aircraft wing on landing and/or take-off, but that section is never "cleaned" during operation of the wind turbine. The normal approach to optimization of blade performance in propellers and wind turbines uses optimization of the product of the chord c and the lift coefficient CL at all points along the blade span. Clearly, when a higher value of ^ is possible, c can be reduced for the same product c.CL, and this results in a reduction of the installed blade area, both giving optimum aerodynamic performance and also avoiding high static loads arising on the blade and tower structure of a wind turbine in the event of high winds while the blades are stationary. This benefit alone makes the present invention very attractive.
A further advantage of operating with high C]*/CD ratios is that the operating speed of the rotor can increase, giving a lower torque value on the hub and the transmission train.
Still a further advantage of the high lift to drag ratio used in the present invention is that the performance coefficient Cp can be increased, where desirable, in order further to enhance the overall efficiency of the wind turbine.
It is well known that for a wind turbine there is a theoretical maximum value of Cp of 0.58, the so-called "Glauert ideal" value, and that in practice wind turbines fail to match that value but can approach the Cp max condition with careful blade optimization. We believe that the blade optimization possibility open to the designer of a wind turbine rotor in accordance with the present invention provide for much closer approach to the ideal than was previously possible.
Blade optimization may result in varying the cross- section of the wind turbine blade along its span while still maintaining the optimum value of c.Cp, and it may be that the criteria of
Figure imgf000007_0001
greater than or equal to 1.8 may not be achieved at the inboard parts of the blade, but in accordance with the present invention the majority of the blade should comply with these criteria. in summary, the criteria of (i) high CL/CD, (ii) a
CLmax in excess of 1.8 and (iii) a reduced stalling angle result in greater energy capture by the wind turbine rotor, safer stall regulation of operation (by virtue of the lower stall angle) , and reductions in the required blade area which both reduce the static loading and facilitate blade construction in that a more simplified construction from less expensive materials can be possible and can then reduce the manufacturing costs of the wind "turbine.
A preliminary investigation of the present invention has shown that the performance coefficient Cp can be increased from 0.45 to 0.48 simply by adopting the high lift to drag ratio and high C-^max proposed in accordance with the present invention, without indulging in any optimization of the rotor blade design. Such blade optimization (involving variation in the section and/or angle of incidence along the blade span) may result in still further increase of Cp closer to the Glauert ideal.
Since the root end of the blade span is not normally aerodynamically as effective as the tip end, we believe that the aerofoil section of this invention should be incorporated at least over the part of the span nearer the tip, preferably over at least the outboard 50% of the span, and more preferably the outboard 85%.

Claims

C A I M S
1. A wind turbine blade having a tip and a root end, in which over at least half of the span the aerofoil section of the blade is one having a C-/CΓJ ratio of at least 75 and a CLmax of at least 1.8 at a stalling angle of attack which is less than or equal to 12° .
2. A wind turbine blade according to claim 1 wherein over said at least half of the span the CL/CD ratio is at least 100.
3. A wind turbine blade according to claim 2, wherein over at least a part of the span the Cι/CD ratio is substantially 200.
4. A wind turbine blade according to claim 1, wherein said at least half of the blade span extends inwardly from the tip end of the blade.
5. A wind turbine blade according to claim 4, wherein said at least half of the span extends over 85% of the span.
6. A wind turbine blade according to any one of the preceding claims, wherein said aerofoil section over at least the majority of the span resembles an aircraft wing with a high lift device permanently deployed.
7. A wind turbine blade according to claim 6, wherein the blade resembles a wing having a trailing edge flap deflected.
8. A blade according to claim 7, wherein the section resembles that of a wing with a slotted flap deflected.
9. A wind turbine according to claim 2 or 3, wherein said at least half of the blade span extends inwardly from the tip end of the blade.
10. A wind turbine rotor comprising a plurality of blades each constructed in accordance with any one of tne preceding claims, and mounted on a hub with the appropriate angle of incidence appropriate to allow the blade to operate close to its stalling angle of attack when rotated by wind passing through the rotor disc.
PCT/GB1991/001265 1990-07-26 1991-07-26 Wind turbine blade and rotor incorporating same WO1992001865A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9016435A GB2246398A (en) 1990-07-26 1990-07-26 Wind turbine blade and rotor incorporating same
GB9016435.1 1990-07-26

Publications (1)

Publication Number Publication Date
WO1992001865A1 true WO1992001865A1 (en) 1992-02-06

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0690236A1 (en) * 1994-06-27 1996-01-03 COFIMCO S.p.A. Untwisted blade for axial-flow fan
CN102072080A (en) * 2011-01-18 2011-05-25 华北电力大学 High-performance blade of wind turbine
EP1856408B1 (en) 2005-02-22 2017-04-05 Vestas Wind Systems A/S Wind turbine blade
EP2007981B1 (en) 2006-04-02 2021-01-20 Wobben Properties GmbH Wind turbine with slender blade

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB0001399D0 (en) * 2000-01-22 2000-03-08 Rolls Royce Plc An aerofoil for an axial flow turbomachine
EP2078852B2 (en) 2008-01-11 2022-06-22 Siemens Gamesa Renewable Energy A/S Wind turbine rotor blade
US8240993B2 (en) * 2011-01-04 2012-08-14 General Electric Company System and method of manipulating a boundary layer across a rotor blade of a wind turbine
CN103174604A (en) * 2011-12-26 2013-06-26 珠海市洁源电器有限公司 Small-size wind turbine blade airfoil family

Citations (9)

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Publication number Priority date Publication date Assignee Title
US1547644A (en) * 1921-10-31 1925-07-28 Fed Engineering Company Aerofoil
US2441151A (en) * 1945-04-12 1948-05-11 Robert T Jones Control surfaces with beveled trailing edge
GB612413A (en) * 1943-11-01 1948-11-12 Wincharger Corp Improvements in wind driven prime movers
DE2322654A1 (en) * 1972-05-04 1973-11-08 Mc Donnell Douglas Corp HIGH PERFORMANCE WINGS AND METHODS OF CONSTRUCTING THE SAME
DE3045695A1 (en) * 1980-12-04 1982-08-19 Hans 5300 Bonn Müller Wing design for wind-driven mechanism - has inclined auxiliary wing behind main wing, forming gap for increase of force
DE3207539A1 (en) * 1982-03-03 1983-09-08 Leo 6800 Mannheim Maniura Propeller with two double blades - for a wind power plant
US4408958A (en) * 1980-12-23 1983-10-11 The Bendix Corporation Wind turbine blade
GB2186638A (en) * 1986-02-05 1987-08-19 Howden James & Co Ltd Wind turbines
AU598498B2 (en) * 1986-12-12 1990-06-28 Robert B. Wheat High drag airfoil apparatus

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GB299387A (en) * 1927-10-25 1929-01-31 Camille Edmond Outurquin Improvements in air propellers
GB944166A (en) * 1960-03-02 1963-12-11 Werner Hausammann Rotor for turbines or compressors
IT1141170B (en) * 1980-02-06 1986-10-01 Cofimco Sas AXIAL FAN WITH BENDS NOT CROSSED AND WITH INCREASED TRACTION
EP0082162B1 (en) * 1981-06-19 1984-11-28 KOLECKI, Jerzy A propeller blade
NL8203019A (en) * 1982-07-28 1984-02-16 Transinvest Bv DEVICE FOR CONVERTING WIND ENERGY IN ANOTHER FORM OF ENERGY.

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1547644A (en) * 1921-10-31 1925-07-28 Fed Engineering Company Aerofoil
GB612413A (en) * 1943-11-01 1948-11-12 Wincharger Corp Improvements in wind driven prime movers
US2441151A (en) * 1945-04-12 1948-05-11 Robert T Jones Control surfaces with beveled trailing edge
DE2322654A1 (en) * 1972-05-04 1973-11-08 Mc Donnell Douglas Corp HIGH PERFORMANCE WINGS AND METHODS OF CONSTRUCTING THE SAME
DE3045695A1 (en) * 1980-12-04 1982-08-19 Hans 5300 Bonn Müller Wing design for wind-driven mechanism - has inclined auxiliary wing behind main wing, forming gap for increase of force
US4408958A (en) * 1980-12-23 1983-10-11 The Bendix Corporation Wind turbine blade
DE3207539A1 (en) * 1982-03-03 1983-09-08 Leo 6800 Mannheim Maniura Propeller with two double blades - for a wind power plant
GB2186638A (en) * 1986-02-05 1987-08-19 Howden James & Co Ltd Wind turbines
AU598498B2 (en) * 1986-12-12 1990-06-28 Robert B. Wheat High drag airfoil apparatus

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0690236A1 (en) * 1994-06-27 1996-01-03 COFIMCO S.p.A. Untwisted blade for axial-flow fan
EP1856408B1 (en) 2005-02-22 2017-04-05 Vestas Wind Systems A/S Wind turbine blade
EP2007981B1 (en) 2006-04-02 2021-01-20 Wobben Properties GmbH Wind turbine with slender blade
CN102072080A (en) * 2011-01-18 2011-05-25 华北电力大学 High-performance blade of wind turbine

Also Published As

Publication number Publication date
GB2246398A (en) 1992-01-29
GB9016435D0 (en) 1990-09-12

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