CN114201841A - Blade design method and blade for wind generating set - Google Patents

Blade design method and blade for wind generating set Download PDF

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Publication number
CN114201841A
CN114201841A CN202010911463.9A CN202010911463A CN114201841A CN 114201841 A CN114201841 A CN 114201841A CN 202010911463 A CN202010911463 A CN 202010911463A CN 114201841 A CN114201841 A CN 114201841A
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blade
design
lift coefficient
section
airfoil
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贾少红
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Jiangsu Goldwind Science and Technology Co Ltd
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Jiangsu Goldwind Science and Technology Co Ltd
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • 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
    • F03D1/0641—Rotors characterised by their aerodynamic shape of the blades of the section profile of the blades, i.e. aerofoil profile
    • 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
    • F05B2240/301—Cross-section characteristics
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/10—Noise analysis or noise optimisation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
    • 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

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Fluid Mechanics (AREA)
  • Geometry (AREA)
  • General Physics & Mathematics (AREA)
  • Evolutionary Computation (AREA)
  • Computer Hardware Design (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • Wind Motors (AREA)

Abstract

The invention provides a blade design method and a blade for a wind generating set, according to the blade design method, the whole or a certain section of the blade is taken as a design section along the spanwise direction of the blade, and the design lift coefficient is reduced to increase the chord length of the blade, reduce the torsion angle of the blade or reduce the relative thickness of the blade, thereby reducing the possibility of blade stall. According to the design method provided by the invention, the possibility of blade stall is reduced, the aerodynamic performance of the blade is improved, and the aerodynamic noise of the blade is reduced.

Description

Blade design method and blade for wind generating set
Technical Field
The invention belongs to the technical field of wind power generation, and particularly relates to a blade design method and a blade for a wind generating set.
Background
A wind generator is an aerodynamic device that relies on the lift of the blade airfoil to operate. When air flows through the blade airfoil, negative pressure is formed on the upper surface (suction surface) of the airfoil, positive pressure is formed on the lower surface (pressure surface), and the blade lift force is generated by the pressure difference between the upper surface and the lower surface, so that the impeller is pushed to rotate, and wind energy is converted into electric energy.
The lift of a blade airfoil increases linearly with increasing angle of attack, but after a certain critical value is reached, the lift suddenly drops and the drag increases substantially, i.e. stall occurs. The wind turbine blade should avoid working under stall or flow separation condition as far as possible, because stall not only brings the loss of unit power generation performance, but also causes the damage of relevant spare part even whole unit, thereby arouses unit security problem. The reasons for stall are many, such as reduced air density, poor blade surface condition, sudden changes in wind speed and direction turbulence, improper unit control, and the profile design of the blade itself.
The starting point of the existing blade shape design is cost and weight, the understanding and attention on the aerodynamic performance of an airfoil, the output performance of the blade and the stall are not enough, and the stall factor is added, so that the blade is hoisted, namely stalled, or stalled after being operated for several months; still other units have good power curve surfaces, but noise tests have found that there is local stall of the blades.
When blade stall is found to be severe, the blade needs to be redesigned to obtain a blade that meets the unit operating performance requirements.
Disclosure of Invention
One of the main objects of the present invention is to provide a blade design method and a blade for a wind park to reduce the possibility of blade stall.
According to an aspect of the present invention, there is provided a method for designing a blade, wherein the entire blade or a certain section of the blade is taken as a designed section in the spanwise direction of the blade, and the design lift coefficient is reduced to increase the chord length of the blade, reduce the twist angle of the blade, or reduce the relative thickness of the blade, thereby reducing the possibility of blade stall.
According to an aspect of the invention, the blade design method comprises the steps of: determining a blade airfoil of each design section of the blade; determining a plurality of design points of the design section along the span direction of the blade; setting the design lift coefficients of the plurality of design point locations so that the design lift coefficients of the plurality of design point locations are lower than a reference design lift coefficient by a predetermined value; and performing curve fitting on the design lift coefficients of the plurality of design point positions to obtain a design lift coefficient curve of the blade.
According to an aspect of the invention, the blade airfoil of each design section of said blade is determined based on a reference blade, said reference blade being a blade which stalls at a standard design air density ± 0.15kg/m3 at a predetermined position in span, said predetermined position being a standard airfoil position.
According to an aspect of the invention, the reference lift coefficient is a design lift coefficient corresponding to the reference blade at the plurality of design points, and the design lift coefficient of the plurality of design points is 0 to 0.5 lower than the reference lift coefficient.
According to an aspect of the invention, the blade comprises a common mode section common mode with the reference blade, in which common mode section the design lift coefficients of the plurality of design points are set to be the same as the reference lift coefficient, and a new design section in which the design lift coefficients of the plurality of design points are set to be 0.001-0.5 lower than the reference lift coefficient.
According to an aspect of the invention, in the new design section, the design lift coefficients of the plurality of design points are set to be lower than the reference lift coefficient by 0.01 to 0.05.
According to an aspect of the invention, the reference design lift coefficient comprises a maximum lift coefficient for the respective blade airfoil.
According to an aspect of the invention, in the case of dividing the blade into a plurality of design sections in the spanwise direction, curve fitting is performed in one of the following ways: (a) every 2m to 10m is taken as a design section, each section is subjected to curve fitting by a function not exceeding the power of 4, and the goodness of fit is not lower than 0.98; (b) taking every 10-20 m as a design section, and performing curve fitting on each section by using a function not more than 6 th power, wherein the goodness of fit is not lower than 0.97; (c) every 20 m-50 m is used as a design section, each section is subjected to curve fitting by a function not exceeding the power of 10, and the goodness of fit is not lower than 0.95.
According to an aspect of the invention, the blade airfoil is a laminar flow airfoil or a high lift airfoil.
According to an aspect of the invention, the plurality of design points includes at least one of positions corresponding to relative thicknesses of 30%, 25%, 24%, 21%, and 18%.
According to an aspect of the invention, said blade is longer than said reference blade, comprises an elongated section, and the design lift coefficient of said plus section at a plurality of design points is determined based on the maximum lift coefficient CLmax of the airfoil to which said elongated section corresponds.
According to an aspect of the invention, at least 2 design points are selected within a region of 2-8m of the common mode section near the tip side.
According to one aspect of the invention, the design lift coefficient of the 10% section of the blade tip of the blade is 0-2 lower than the local maximum lift coefficient CLmax, and the design lift coefficient is 0 at the position of the blade tip.
According to another aspect of the invention, a blade for a wind generating set is provided, the blade being designed by the blade design method described above, and the airfoil profile of the blade being a DU series airfoil profile.
According to one aspect of the invention, the design lift coefficient of the blade is 1.0-1.2 at the position where the spanwise length of the blade is 40-50 m.
According to one aspect of the invention, the blade chord length of the blade is 1.3-1.4 m.
According to one aspect of the invention, the twist angle of the blade is-2 deg to 0 deg.
According to an aspect of the invention, the relative thickness of the blade is 20-30%.
According to the invention, through fully understanding the aerodynamic performance of the airfoil profile, the middle part of the reference blade is cut off and the reference blade is designed to be extended, the attack angle far away from the stall is selected at the design point, and the stall degree of the extended blade is greatly reduced through the design of increasing the chord length of the blade and reducing the twist angle; the blade appearance design concept can be applied to all blade designs.
Drawings
The above and/or other objects and advantages of the present invention will become more apparent from the following description of the embodiments taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a graph illustrating an exemplary comparison of a design lift coefficient curve for a new blade to a design lift coefficient for a reference blade in accordance with one embodiment of the present invention;
FIG. 2 is a design lift coefficient curve fit example of a new blade according to an embodiment of the invention;
FIG. 3 is a chord length comparison example of a new blade to a reference blade according to one embodiment of the invention;
FIG. 4 is a twist angle comparison example of a new blade and a reference blade according to one embodiment of the present invention.
FIG. 5 is an exemplary plot of lift coefficient for a new blade at different incoming wind speeds in accordance with one embodiment of the present invention.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. However, it should not be understood that the aspects of the present invention are limited to the embodiments set forth herein. The same reference numerals in the drawings denote the same or similar structures, and thus their detailed description will be omitted.
When the design lift coefficient of the blade is close to the maximum lift coefficient CLmax, there is a risk of easy stall. For example, in the case of large turbulence or changes in the base conditions, the blades may easily enter a stall condition or partial stall. Therefore, the closer the design lift coefficient of the blade is to the maximum lift coefficient CLmax, the more likely the blade is to stall, and the narrower the applicable air density range.
In addition, the surface of the new blade is relatively smooth and the corresponding maximum lift coefficient CLmax is relatively high, whereas with increasing time of use the blade surface becomes dirty and the corresponding maximum lift coefficient CLmax is relatively low. Therefore, when determining the design lift coefficient of the blade, not only the corresponding maximum lift coefficient CleanCLmax when the surface of the blade is smooth is referred to, but also the corresponding maximum lift coefficient RoughClmax when the surface of the blade is rough is considered, and a certain distance is kept between the design lift coefficient of the blade and the two maximum lift coefficients, especially a certain difference value is kept between the design lift coefficient of the blade and the RoughClmax, so as to ensure the safe operation margin of the blade. Therefore, a certain distance (difference) between the design lift coefficient of the blade and the maximum lift coefficient RoughCLmax needs to be met to reduce the risk of blade stall.
When a stall of the blade occurs or there is a risk of stall, the blade needs to be redesigned. AsFor example, when the blade is positioned at a predetermined position in the span direction at a standard air density of + -0.15 kg/m3When stall occurs under conditions, the blade is identified as a stalled blade and needs to be redesigned, where the predetermined position is referred to as the standard airfoil position.
Furthermore, other ways of determining whether the blade is at risk of stall may be used, for example, the blade may be deemed at risk of stall when the difference between the design lift coefficient of the blade and the corresponding maximum lift coefficient CleanCLmax is less than a predetermined value (e.g., less than 0.3). As another example, when the blade is designed for an air density of 1.0kg/cm3If the blade has an air density of 0.9kg/cm3Stall will occur and the blade needs to be redesigned. However, the present invention is not limited to the above examples, and the condition that the blade is at risk of stall may be determined according to actual conditions.
In the present invention, such a blade at risk of stall or having a stall problem is identified as a stalled blade (also referred to as an old blade or an old blade), and an improvement is proposed on the basis of the old blade, so as to design a new blade to replace the old blade.
The invention provides a blade design method. According to the blade design method, the whole or a certain section of the blade is taken as a design section along the spanwise direction of the blade, and the design lift coefficient is reduced to increase the chord length of the blade, reduce the torsion angle of the blade or reduce the relative thickness of the blade, so that the possibility of blade stall is reduced.
In the method, the new blade can be designed by taking the old blade as the reference blade, the air density range applicable to the blade is improved, and the stalling risk is reduced. For example, when the old blade has an air density of 1.1kg/cm3When stall occurs, the newly designed blade can be designed at an air density of 1.01kg/cm by the design method of the present invention3No stall occurs.
The blade design method according to the invention may comprise the steps of:
determining a blade airfoil of each design section of the blade; determining a plurality of design point positions of the design section along the span direction of the blade; setting design lift coefficients for the plurality of design point locations based on the reference lift coefficient. Specifically, the design lift coefficients of the plurality of design points may be made lower than the reference design lift coefficient by a predetermined value, which may be 0 to 0.5; and performing curve fitting on the design lift coefficients of the plurality of design point positions to obtain a design lift coefficient curve of the blade.
In determining the blade airfoil of each design section of a new blade, the blade airfoil of each design section of the blade may be determined based on a reference blade, which refers to a blade in which a stall occurs at a standard design air density ± 0.15kg/m3 at a predetermined position in the span direction of the reference blade, which refers to a standard airfoil position.
The blade airfoil of the new blade may be the same airfoil as the reference blade. For a determined airfoil the maximum lift coefficient CleanCLmax and the maximum lift coefficient RoughCLmax are determined, if wind tunnel tests are performed, the maximum lift coefficient CleanCLmax and the maximum lift coefficient RoughCLmax of the new blade will be the same as the maximum lift coefficient CleanCLmax and the maximum lift coefficient RoughCLmax of the old blade if it is considered that the new blade can still be designed with the same airfoil as the old blade.
When determining the blade airfoil shape, the laminar flow airfoil shape can be selected for blade design, and the high-lift airfoil shape can also be adopted for blade design. The laminar flow airfoil has higher maximum lift-drag ratio but low maximum lift coefficient; high lift airfoils, on the contrary, have a high maximum lift coefficient but a relatively low maximum lift-to-drag ratio. The high-lift wing type is characterized in that the natural transition is close to Clmax of full turbulence, and performance reduction caused by dirty leading edge or rough surface can be resisted; when the high-lift airfoil is adopted, the design value is not higher than 80% of the upper limit of the maximum lift coefficient RoughCrmax.
On each design section, 2-15 design point positions can be determined. For example, the blade may be taken as a whole as one design segment, or the blade may be divided into a plurality of design segments along the span direction of the blade, for example, every 2m to 10m as one design segment, every 5m to 20m as one design segment, or 20m to 50m as one design segment. As an example, the blade may be divided into three design sections, e.g., a root section, a midspan section, and a tip section. The plurality of design points may include at least one of locations corresponding to relative thicknesses of 30%, 25%, 24%, 21%, and 18%. When the design point position is determined, the design point position can be determined by considering factors such as aerodynamic performance or aerodynamic noise of the blade.
When setting the design lift coefficient of each design point of the new blade, the reference lift coefficient may be determined first. Alternatively, reference lift coefficients for a plurality of design point locations may be determined based on a reference blade. For example, the reference lift coefficient may be a design lift coefficient for the reference blade at the plurality of design points. When the new blade is increased in length compared to the reference blade, the maximum lift coefficient RoughCLmax or clearclmax of the airfoil corresponding to the lengthened section can be used as the reference lift coefficient.
For the determined blade airfoil, when the plurality of design point locations are standard design point locations, the reference maximum lift coefficient RoughCLmax or clearclmax corresponding to the plurality of design point locations can be determined according to the lookup table, and for the rest of design point locations, the reference maximum lift coefficient RoughCLmax or clearclmax can be obtained in an interpolation mode. The maximum lift coefficient comprises the corresponding maximum lift coefficient CleanCLmax in case of a smooth blade surface and the corresponding maximum lift coefficient RoughClmax in case of a rough blade surface. Since the maximum lift coefficient CleanCLmax is higher than the maximum lift coefficient RoughCLmax, and the maximum lift coefficient is determined for a specific blade airfoil, the maximum lift coefficient CleanCLmax can be used as a reference lift coefficient for each design point, and the maximum lift coefficient RoughCLmax can also be used as a reference lift coefficient.
After determining the reference lift coefficient, a design lift coefficient for the design segment is determined based on the reference lift coefficients for the corresponding design point locations. For example, at a design point location corresponding to the reference blade, the design lift coefficient of the point may be set to be 0 to 0.5 lower than the design lift coefficient of the reference blade.
The newly designed blade may include a common mode section common to the reference blade and the newly designed section. For example, for a 58 meter long blade, it is possible to co-mould over the inner 40 meters, with a redesign of the remaining 18 meters. In the common mode section, the design lift coefficients at the plurality of design points may be set to be the same as the reference lift coefficient, and in the new design section, the design lift coefficients at the plurality of design points may be set to be lower than the reference lift coefficient by 0.001 to 0.05. Preferably, in the new design section, the design lift coefficients of the plurality of design points are set to be lower than the reference lift coefficient by 0.01 to 0.05. The specific value is selected to set a relatively safe design lift coefficient based on the target stall free air density. The closer to the common mode section, the smaller the value of the reduction of the design lift coefficient relative to the design lift coefficient of the old blade.
In order to ensure the consistency and smoothness of the designed lift coefficient curve between the new design section and the common mode section, it is necessary to select 2 to 5 design points on the common mode section, and these design points are selected within a predetermined length range of the end of the common mode section close to the blade tip side, for example, if the common mode section length is 40m, the design points can be selected within the last 2m to 8m of the 40m length, and preferably 3 to 4 design points are selected.
Although in the blade design method described above the design lift coefficient of the new blade is determined by referring to the design lift coefficient of the old blade, the blade design method of the present invention is not limited thereto, and may be determined by referring to the local Clmax of the new blade instead of the design lift coefficient of the old blade.
Furthermore, the newly designed blade may also be longer than the reference blade, i.e. comprise an elongated section, the design lift coefficients of which at the time of determining the design lift coefficient may be determined for a plurality of design points on said elongated section based on the maximum lift coefficient RoughCLmax of the airfoil to which said elongated section corresponds.
As an example, the design lift coefficient of 10% of the blade tip is 0-2 lower than the local maximum lift coefficient Clmax (which can be CleanClmax or RoughCrmax) as much as possible, especially the most blade tip position, and the design lift coefficient can be 0, so that the blade tip loss and the vortex shedding noise caused by the three-dimensional vortex of the blade tip due to the pressure difference between the upper part and the lower part of the blade tip are prevented. When curve fitting the design lift coefficients of a plurality of design points on the design section, the curve fitting may be performed in one of the following ways: (a) every 2m to 10m is taken as a design section, each section is subjected to curve fitting by a function not exceeding the power of 4, and the goodness of fit is not lower than 0.98; (b) taking every 10-20 m as a design section, and performing curve fitting on each section by using a function not more than 6 th power, wherein the goodness of fit is not lower than 0.97; (c) every 20 m-50 m is used as a design section, each section is subjected to curve fitting by a function not exceeding the power of 10, and the goodness of fit is not lower than 0.95.
FIG. 1 is an exemplary plot of the design lift coefficient of a new blade versus the design lift coefficient of an old blade in accordance with one embodiment of the present invention. In fig. 1, the horizontal axis represents the blade span direction, each bin may represent a length of 5 meters, the vertical axis represents the maximum lift coefficient Clmax, and each bin may represent 0.2.
The design lift coefficient curve in fig. 1 is obtained by curve-fitting the design lift coefficients of a plurality of design point locations. The plurality of design point locations represents locations corresponding to a plurality of relative thickness percentages. For example, in the example shown in FIG. 1, two of the design points are shown, a first design point may be a location corresponding to 25% of the thickness and a second design point may correspond to 21% of the thickness.
In fig. 1, the ordinate Cl represents the lift coefficient, the abscissa represents the spanwise position, New represents the newly designed blade, Old represents the original blade, i.e., the reference blade, the dotted line represents the designed lift coefficient curve of the newly designed blade, and the solid line represents the designed lift coefficient curve of the reference blade. Taking the example of 5m per box span and 0.2 in the longitudinal direction, it can be seen that for the reference blade, the maximum lift coefficient CleanClmax (denoted by Old Clean) is about 0.2 higher for the smooth blade surface than RoughClmax (denoted by Old Rough) for the Rough blade surface. Meanwhile, it can be seen that, along the spanwise direction of the blade, the design lift coefficient curve of the newly designed blade is 0-0.18 lower than that of the reference blade. The new design blade has an increased length over the reference blade, and at the second design point shown, the new blade has a design lift coefficient about 0.57 less than the maximum lift coefficient CleanClmax, over the tip range.
The relative thickness of the airfoil of the blade is a monotone decreasing trend along the spanwise direction (the direction from the blade root to the blade tip). The root thickness is set to 100%, and as an example, in determining the airfoil of the blade, the relative thickness of the 1/3 length range on the inner side (near the root side) of the blade may be set to 100% -30%, the relative thickness of the 1/3 length of the middle of the blade may be 40% -20%, and the relative thickness of the 1/3 length range on the outer side (near the tip side) of the blade may be 30% -10%.
When the design lift coefficient of each design point position is determined, the design lift coefficient of the new blade can be determined by referring to the design lift coefficient of the old blade. Taking the first design point location on the left side of fig. 1 as an example, if the design lift coefficient of the design lift curve of the old blade at the point location is closer to RoughCLmax, the design lift coefficient of the new blade segment at the corresponding design point location can be reduced. For example, at the corresponding point, the design lift coefficient of the old blade is 1.15, and the design lift coefficient of the new blade section at the point may be set to 1.1. Taking the second design point on the right side of fig. 1 as an example, the corresponding RoughCLmax is approximately 1.4, and the design lift coefficient of the new blade segment at this point can be set to 1.05. That is, when determining the design lift coefficient of the design point location of the new blade section, the setting may be performed by lowering the design lift coefficient of the new blade section by 0 to 0.5 with reference to the design lift coefficient of the old blade at the design point location. In the case of a new blade that is lengthened with respect to the old blade, the design lift coefficient of the new blade section at the design point can be determined with reference to only the RoughCLmax of the corresponding airfoil profile at the design point, within the length of the extension. Therefore, for a blade design section, the lift coefficient of at least 3 design point positions can be determined, and then the design lift coefficients corresponding to the point positions are subjected to curve fitting, so that a design lift coefficient curve of the blade design section is obtained.
FIG. 2 is a design lift coefficient curve fit example of a new blade according to an embodiment of the invention. In the example shown in fig. 2, the blade stalls below tip ratio 9 with a reference blade length of 58m, DU airfoil.
The ordinate Cl in fig. 2 represents the lift coefficient and the abscissa represents the spanwise position in m, by way of example each cell in the longitudinal direction may represent 0.1 and each cell in the spanwise direction may represent 5m. The upper curve is the design lift curve of the old blade, and the lower curve is the design lift curve of the new blade. One design point location of the two design lift curves at the leftmost end may be located in the common mode section, at which point the two design lift curves coincide. Along the spanwise direction of the blade, the difference between the design lift coefficient of a plurality of design points close to the common mode section and the design lift coefficient of the old blade is gradually increased. However, the tendency to increase is not always maintained. The difference in the design lift coefficient between the two is greatest at a point approximately 16m from the first point on the left, and the difference in the design lift coefficient between the two is reduced again in the region near the tip of the blade.
In the example shown in fig. 2, the design lift coefficient curve of the common mode segment is omitted in the spanwise direction of the New blade, and the New design segment can be divided into three segments (denoted by New2, New3 and New4 respectively) for design lift coefficient curve fitting. By way of example, the three-stage lift coefficient curves may be a quadratic polynomial, a quartic polynomial, and a cubic polynomial, respectively, and the goodness-of-fit may be 0.9996, 0.9986, 0.9877, respectively. For example, in the first segment, the newly fitted design lift coefficient curve may be a quadratic function, and may be y-0.0007 x2+0.0827x-1.273, where y corresponds to the ordinate and represents the lift coefficient and x represents the spanwise position in m. In the section corresponding to the design section, the Old blade can be divided into two design sections (respectively represented by Old2 and Old 3) to carry out design lift coefficient curve fitting, and the fitting goodness can be respectively 0.9998 and 0.9995. In the corresponding design segment, the design lift coefficient curve of the corresponding old blade may also be a quadratic function, which may be expressed as y-8E-05 x2+0.0042x +0.6613, goodness of fit R20.9998. The expression of the above fitting curve and the goodness of fit are only shownFor example, the present invention is not limited thereto.
In the example shown in fig. 2, the length of the new blade is increased relative to the old blade, and the determination of the design lift coefficient of this increased portion can be referred to the RoughCLmax of the corresponding airfoil, which will not be described in detail here.
FIG. 3 is a chord length comparison example of a New blade (denoted New) to an Old blade (denoted Old) according to one embodiment of the present invention. In fig. 3, the ordinate represents chord length in m, each bin may represent 0.5m, and the abscissa represents spanwise position in m, each bin may represent 5m.
In the example shown in fig. 3, the blade stalls below tip speed ratio 9 with a reference blade length of 58 m. Therefore, the design lift coefficient of the newly designed blade at the position of 45m is 1.1, which is 0.05 lower than that of the corresponding position of the reference blade. The relative thickness of the newly designed blade at the 45m design point is 25%. From this figure it can be seen that the blade chord length increases with a decreasing design lift coefficient.
For the relative thickness, compared with the old blade, in the same spanwise position of the newly designed blade, the relative thickness is lower by 0-15% compared with the original design, especially the relative thickness near the blade tip can be lower by more than 20%, and the relative thickness is maintained to be locally constant or monotonically decreased from the blade root to the blade tip, so that the overall aerodynamic performance of the blade can be improved by about 0-5%, the aerodynamic noise can be reduced by 0-5dBA, and the noise reduction degree of the aerodynamic accessories can be improved by 0-3 dBA.
FIG. 4 is a twist angle comparison example of a new blade to an old blade according to one embodiment of the present invention. The ordinate indicates the twist angle deg and the abscissa indicates the spanwise position. Each cell in the longitudinal direction represents 1deg, and each cell in the transverse direction represents 5m. It can be seen from this figure that the twist angle of the newly designed blade is much smaller in absolute value than the twist angle of the reference blade.
In the example shown in fig. 4, the blade stalls below tip speed ratio 9 with a reference blade length of 58 m. Therefore, the design lift coefficient of the newly designed blade at the position of 45m is 1.1, which is 0.05 lower than that of the corresponding position of the reference blade. The relative thickness of the newly designed blade at 45m. design point location is 25%.
FIG. 5 is an exemplary plot of lift coefficient for a new blade at different incoming wind speeds in accordance with one embodiment of the present invention. The abscissa indicates the spanwise position in m, each cell may represent 5m, the ordinate indicates the lift coefficient Cl, and each cell may represent 0.2.
It can be seen from fig. 5 that when the blades reach the transition section, the rotating speed is unchanged, the wind speed is increased, the operating attack angle and the lift coefficient are increased, and the newly designed blades are far away from clearclmax; if the blade manufacturing process is not good or the project site has more sand storm or mosquitoes, the distance between the new design and the RoughCrmax is also far, and the blade is difficult to enter a stall state. The blades do not enter stall, so that the power generation performance is good, the AEP (annual energy production) is high, the noise is low, all parts of the whole machine are stable, and the safety is high.
According to the blade design method, the possibility of blade stall is reduced through the blade profile design with large chord length, small torsion angle and low relative thickness, the aerodynamic performance of the blade is improved, and the aerodynamic noise of the blade is reduced. According to the design method provided by the invention, the chord length of the blade is increased by reducing the design lift coefficient of the blade. For example, the chord length of the new blade with a length of 60m may be about 0% to 500% (about 0 to 1.5m) larger than that of the original blade, the torsion angle may be about 0 to 10deg smaller than that of the original design, the design lift coefficient may be 0 to 0.5% lower than that of the original design, and the relative thickness may be 0 to 200% (about 0 to 20% relative thickness absolute value) lower than that of the original design.
The blade design method has the advantages that the new blade can run at a lower attack angle or lift coefficient, the distance from the stall attack angle or lift coefficient has a margin of 0-5 deg or 0-0.5, even if the blade is manufactured to have a certain deviation or the leading edge is not smooth enough, or the air density is lower, such as 1.0kg/m3Or improper unit control or sudden changes in wind speed, will not cause stall. Compared with a new design, the old design has small chord length, low solidity and high design lift coefficient, is particularly easy to enter local stall or large-area stall, causes power curve reduction and noise increase, and can cause blade vibration seriously.
According to an aspect of the invention, there is provided a blade for a wind park, the airfoil of the blade being a DU airfoil, the blade being designed using the blade design method described above.
The design lift coefficient of the blade is 0-3, the chord length of the blade is 0-5 m, the twist angle is-10-2 deg and the relative thickness is 10-100% at the spanwise length of the blade from 0m to the tip. For example, when the length of the blade is within a range from 58m to 65m, the design lift coefficient of the blade can be 1.0 to 1.2, the chord length of the blade can be 1.3m to 1.4m, the twist angle of the blade can be-2 to 0deg, and the relative thickness of the blade can be 20 to 30% at a position where the spanwise length of the blade is 40m to 50 m.
The described features, structures, or characteristics of the invention may be combined in any suitable manner in one or more embodiments. In the above description, numerous specific details are provided to give a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

Claims (18)

1. A method for designing a blade, characterized in that the whole or a certain section of the blade is taken as a design section along the spanwise direction of the blade, and the design lift coefficient is reduced to increase the chord length of the blade, reduce the twist angle of the blade or reduce the relative thickness of the blade, thereby reducing the possibility of the blade stalling.
2. A blade design method according to claim 1, comprising the steps of:
determining a blade airfoil of each design section of the blade;
determining a plurality of design points of the design section along the span direction of the blade;
setting the design lift coefficients of the plurality of design point locations so that the design lift coefficients of the plurality of design point locations are lower than a reference design lift coefficient by a predetermined value;
and performing curve fitting on the design lift coefficients of the plurality of design point positions to obtain a design lift coefficient curve of the blade.
3. The blade design method of claim 2, wherein the blade airfoil of each design section of the blade is determined based on a reference blade, which is defined as a standard design air density ± 0.15kg/m at a predetermined position in a spanwise direction3A blade in which stall occurs under conditions, the predetermined position being a standard airfoil position.
4. The blade design method according to claim 3, wherein the reference lift coefficient is a design lift coefficient corresponding to the reference blade at the plurality of design points, and the design lift coefficient at the plurality of design points is 0 to 0.5 lower than the reference lift coefficient.
5. The blade design method according to claim 4, wherein the blade comprises a common mode section common mode with the reference blade, in which common mode section the design lift coefficients of the plurality of design points are set to be the same as the reference lift coefficient, and a new design section in which the design lift coefficients of the plurality of design points are set to be 0.001 to 0.5 lower than the reference lift coefficient.
6. The blade design method according to claim 5, wherein in the new design section, the design lift coefficients at the plurality of design points are set to be lower than the reference lift coefficient by 0.01 to 0.05.
7. The blade design method of claim 1, wherein the reference design lift coefficient comprises a maximum lift coefficient for the respective blade airfoil.
8. The blade design method of claim 2, wherein in the case of dividing the blade into a plurality of design sections in a spanwise direction, curve fitting is performed in one of the following ways:
(a) every 2m to 10m is taken as a design section, each section is subjected to curve fitting by a function not exceeding the power of 4, and the goodness of fit is not lower than 0.98;
(b) taking every 10-20 m as a design section, and performing curve fitting on each section by using a function not more than 6 th power, wherein the goodness of fit is not lower than 0.97;
(c) every 20 m-50 m is used as a design section, each section is subjected to curve fitting by a function not exceeding the power of 10, and the goodness of fit is not lower than 0.95.
9. The blade design method of claim 2, wherein the blade airfoil is a laminar flow airfoil or a high lift airfoil.
10. The blade design method of claim 2, wherein the plurality of design point locations includes at least one of locations corresponding to relative thicknesses of 30%, 25%, 24%, 21%, and 18%.
11. A method for blade design according to claim 5, where the blade is longer than the reference blade, comprising an elongated section, the design lift coefficient of the plurality of design points on the added section being determined based on the maximum lift coefficient CLmax of the airfoil to which the elongated section corresponds.
12. The blade design method of claim 5, wherein at least 2 design points are selected within a 2m-8m area of the common mode section near the tip side.
13. The method of claim 11, wherein the design lift coefficient of the 10% section of the blade tip of the blade is 0-2 lower than the local maximum lift coefficient CLmax, and the design lift coefficient is 0 at the blade tip position.
14. A blade for a wind park according to any of claims 1 to 13, wherein the blade is designed according to the blade design method of any of claims 1 to 13, and wherein the airfoil profile of the blade is a DU series airfoil profile.
15. The blade for the wind generating set according to claim 14, wherein the design lift coefficient of the blade is 1.0-1.2 at the position where the spanwise length of the blade is 40-50 m.
16. The blade for a wind generating set according to claim 15, wherein the blade has a blade chord length of 1.3m to 1.4 m.
17. The blade for the wind generating set according to claim 15, wherein the twist angle of the blade is-2 to 0 deg.
18. The blade for a wind park according to claim 15, wherein the blade has a relative thickness of 20% to 30%.
CN202010911463.9A 2020-09-02 2020-09-02 Blade design method and blade for wind generating set Pending CN114201841A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111810353A (en) * 2020-06-04 2020-10-23 何立武 Forward-bent and backward-raised chord blade

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111810353A (en) * 2020-06-04 2020-10-23 何立武 Forward-bent and backward-raised chord blade

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