CN103047079A - Efficient low-load wing section special for horizontal shaft wind turbine blade and designing method of wind section - Google Patents

Abstract

The invention discloses a designing method of an efficient low-load wing section special for a horizontal shaft wind turbine blade and the wing section obtained on the basis of the method. The designing method is based on an anti-design method, and the designed wing section is efficient, low-load, good in variable working conditions, and smooth in stalling. The efficient low-load wing section has the advantages that a designing goal of traditional wing sections is changed, and a pneumatic characteristic required by the wing section is provided; the wind section has high maximum lift-drag ratio, high designed lift coefficient and low maximum lift coefficient, and low lift coefficient decreasing under the condition front edge roughness is achieved; the anti-design method is utilized to design the wing section; and corresponding pneumatic parameter designing indexes are provided aiming at wing section applied to the outer sides, with thickness not more than 25%, of wind turbine blades.

Description

A kind of efficient low Blades For Horizontal Axis Wind special airfoil and design method thereof of carrying

Technical field

The present invention relates to a kind of special airfoil design method of Blades For Horizontal Axis Wind, relate in particular to a kind of based on having of anti-design method efficient low carry, the design method of the Blades For Horizontal Axis Wind special airfoil of good Study on Variable Condition Features and level and smooth stalling characteristics.

Background technique

Wind electricity blade is the core component of wind-powered electricity generation unit, and the performance quality of pneumatic equipment blades made special airfoil directly affects the performance of pneumatic equipment blades made.And blade not only has the requirement of aeroperformance to also have the load requirement, and we wish that wind energy conversion system has higher output power, and the increase that can have again lower load, particularly limit load simultaneously is larger on the impact of wind electricity blade.

Vane design of wind turbines requires Special Airfoil of Wind Turbine to have high maximum lift coefficient all the time, with the aerofoil profile outside the output power of raising blade, particularly blade.Yet actual Leaf operates near the operating point for design more, rather than near the maximum lift coefficient, and high design lift coefficient can reduce the chord length of aerofoil profile, with the weight that reduces blade, reduce load.And maximum lift coefficient is very little on the impact of the output power of blade, and the increase of maximum lift coefficient can cause the increase of blade limit load on the contrary.

In the wind energy conversion system running, because the impact of fitful wind or control the various factorss such as untimely, wind energy conversion system can not operate under the design conditions fully, requires wind mill airfoil to have good Study on Variable Condition Features and level and smooth stalling characteristics.

Therefore develop a kind of have efficiently lowly carry, good Study on Variable Condition Features and the Blades For Horizontal Axis Wind special airfoil of level and smooth stalling characteristics be very important, it should have high maximum lift-drag ratio, high design lift coefficient, have than low maximum lift coefficient, under the coarse condition of leading edge descend less and good Study on Variable Condition Features and level and smooth stalling characteristics of design lift coefficient.

Summary of the invention

In the prior art, has multiple Airfoil Design method, common are various forms of intelligent optimized design methods, such as now widely used Optimization Design based on genetic algorithm, another common Airfoil Design method is the indirect problem design method, no matter use any design method can obtain suitable aerofoil profile, but in the existing Airfoil Design method, too pay attention to the raising of maximum lift coefficient etc., and usually to obtain larger maximum lift coefficient as design object, facts have proved, it is lower that the aerofoil profile of designing based on this theory in use often shows efficient, the larger deficiency that waits of load, this has limited the development of pneumatic equipment blades made greatly.

For the above-mentioned shortcoming and defect of prior art, the technical problem to be solved in the present invention be propose a kind of have efficiently lowly carry, the design method of the Blades For Horizontal Axis Wind special airfoil of good variable working condition and level and smooth stalling characteristics and possess the Blades For Horizontal Axis Wind special airfoil of above-mentioned characteristic.

Because wind energy conversion system operates near the operating point for design (namely designing the angle of attack) more, rather than near the maximum lift coefficient.Formula by following power p can draw, and from Airfoil Aerodynamic Performance, improves the maximum lift-drag ratio of aerofoil profile

With design lift coefficient C _lIt is the key that improves the blade output power.And high design lift coefficient can reduce the chord length of aerofoil profile, with weight, the reduction load that reduces blade.

$\mathrm{dp}==\frac{1}{2}\mathrm{\&rho;}{{\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="HDA00002635419400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_0}^2\mathrm{c\&Omega;}(C_l\sin \mathrm{\&phi;}-C_d\cos \mathrm{\&phi;})\mathrm{rdr}=\frac{1}{2}\mathrm{\&rho;}{{\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="HDA00002635419400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_0}^2\mathrm{c\&Omega;}{C}_l\sin \mathrm{\&phi;}(1-\frac{1}{\frac{C_l}{C_d}\mathrm{tg\&phi;}})\mathrm{rdr}$

The aerodynamic load that acts on the pneumatic equipment blades made is waved the shearing force F of direction _XbIt is the principal element that affects the blade limit load.By F _XbCalculating formula can find out, the maximum lift coefficient of aerofoil profile is higher, therefore the limit load that produces can be larger, will limit the maximum lift coefficient of aerofoil profile in the design.

${\mathrm{dF}}_{\mathrm{xb}}=\frac{1}{2}\mathrm{\&rho;}{{\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="HDA00002635419400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_0}^{2}c{C}_n=\frac{1}{2}\mathrm{\&rho;}{{\mathrm{<figure-callout\; id="0"\; label="V"\; filenames="HDA00002635419400011.png"\; state="\{\{state\}\}">V</figure-callout>}}_0}^{2}c(C_l\sin \mathrm{\&phi;}-C_d\cos \mathrm{\&phi;})\mathrm{dr}$

In addition because in the wind energy conversion system running, because the impact of fitful wind or control the various factorss such as untimely, wind energy conversion system can not operate under the design conditions fully, requires wind mill airfoil to have good Study on Variable Condition Features and level and smooth stalling characteristics.

According to above-mentioned analysis draw a kind of have efficient low carry, good variable working condition and the Blades For Horizontal Axis Wind special airfoil of level and smooth stalling characteristics should have following aerodynamic characteristic: have high maximum lift-drag ratio, high design lift coefficient, have than low maximum lift coefficient, under the coarse condition of leading edge descend less and good Study on Variable Condition Features and level and smooth stalling characteristics of design lift coefficient.

The present invention is that the technological scheme that its technical problem of solution adopts is:

A kind of design method of Blades For Horizontal Axis Wind special airfoil, the Inverse Design Method of Airfoil based on general is characterized in that, described design method may further comprise the steps:

Given aerofoil profile goal pressure distributes and initial baseline airfoil;

The pressure distribution of adjusting baseline airfoil obtains middle aerofoil profile;

Use the Euler equation to calculate the pressure distribution of middle aerofoil profile;

The pressure distribution of aerofoil profile and goal pressure distribute relatively, difference degree according to the two judges whether that needs continue to adjust middle aerofoil profile, if described difference degree is in the margin of error that allows, then stop described adjustment, obtain the target aerofoil profile, otherwise the pressure distribution of aerofoil profile in the middle of continue adjusting is until till the pressure distribution of middle aerofoil profile meets the demands;

Wherein,

Described aerofoil profile goal pressure distribute comprise that aerofoil profile goal pressure under the design angle of attack distributes and critical stall angle under the aerofoil profile goal pressure distribute: in the aerofoil profile goal pressure distribution under the described design angle of attack, pressure peak on the suction surface is in distance aerofoil profile leading edge point 1-25% chord length position, all has mild adverse pressure gradient from aerofoil profile suction surface leading edge to 40% chord length position, to obtain less resistance coefficient and higher design lift coefficient; During aerofoil profile goal pressure under described critical stall angle distributed, the pressure peak on the suction surface was in distance aerofoil profile leading edge point 0-1% chord length position, with the maximum lift coefficient of control aerofoil profile;

In the design process, constraint aerofoil profile maximum ga(u)ge position is in 34.0%-37.0% chord length position.

Preferably, for the relative thickness that is applied to the blade outside less than or equal to 25% aerofoil profile, described judge whether to need to continue to adjust in the middle of in the step of aerofoil profile, whether each aerodynamic parameter of aerofoil profile satisfies following condition in the middle of also needing further to judge:

(a) high efficiency:

Maximum lift-drag ratio: ${\left(\frac{C_l}{C_d}\right)}_{\max }>150,$

Design lift coefficient: C _Ldesign1.16;

(b) low carrying property: maximum lift coefficient C _LmaxWith design lift coefficient C _LdesignSatisfy

(c) coarse immunity: $0.85\&le;\frac{C_{\mathrm{ldesign}}^{\&prime;}}{C_{\mathrm{ldesign}}}\&le;1,$

(d) good Study on Variable Condition Features:

Δα=α _stall-α _design≥5， $0<\frac{C_{l\max }-C_{\mathrm{ldesign}}}{\mathrm{\&Delta;\&alpha;}}<0.05,$ $\frac{|{\left(\frac{C_l}{C_d}\right)}_{\mathrm{stall}}-{\left(\frac{C_l}{C_d}\right)}_{\max }|}{\mathrm{\&Delta;\&alpha;}}<21;$

(e) level and smooth stalling characteristics:

${\left(\frac{{(\mathrm{Cl}-{\mathrm{Cl}}_{\max })}^2}{\mathrm{\&alpha;}-{\mathrm{\&alpha;}}_{\mathrm{stall}}}\right)}_{\max }<0.005,0<\mathrm{\&alpha;}-{\mathrm{\&alpha;}}_{\mathrm{stall}}<10,$

Above various in:

C ' _LdesignDesign lift coefficient for coarse condition Airfoil;

C _l, C _d, C _Ldesign, C _Lmax,

Lift coefficient, resistance coefficient, design lift coefficient, maximum lift coefficient, maximum lift-drag ratio for design angle of attack Airfoil under the smoothness condition;

Ratio of lift coefficient to drag coefficient for smoothness condition lower critical stall angle Airfoil;

α, α _Stall, that Δ α is respectively the angle of attack, stall angle, the angle of attack is poor.

Further, the design lift coefficient C ' of the coarse condition Airfoil of described calculating _LdesignStep, be to the middle aerofoil profile that obtains in the design, by arranging and fixedly turn the design lift coefficient that calculates when twisting in upper surface 1% chord length, lower surface 10% chord length position.

The design method of Blades For Horizontal Axis Wind special airfoil of the present invention and the pneumatic equipment blades made special airfoil that designs according to the method have the following advantages:

1, pneumatic equipment blades made special airfoil of the present invention have efficient low carry, good variable working condition and level and smooth stalling characteristics, changed the traditional Airfoil Design target of the larger maximum lift coefficient that covets; 2, pneumatic equipment blades made special airfoil of the present invention has good aerodynamic characteristic, effectively improved Blade Properties, have high maximum lift-drag ratio, high design lift coefficient, have than low maximum lift coefficient, under the coarse condition of leading edge the design lift coefficient less characteristics that descend; 3, wind turbine blade airfoil family of the present invention can improve the blade output power, reduces load, reduces the weight of blade, reduces the blade cost.

Description of drawings

The geometric type line chart of Fig. 1 18%, 21%, 25% 3 aerofoil profile of the present invention;

The relative thickness that Fig. 2 designs for the present invention is that 25% aerofoil profile is in the pressure distribution of design point;

The relative thickness that Fig. 3 designs for the present invention is the pressure distribution of 25% aerofoil profile under critical stall angle.

Embodiment

Below in conjunction with example and accompanying drawing the present invention is described in detail.

The suffered power of aerofoil profile is that the distributed force that acts on upper and lower surface is made a concerted effort, and surface force has two kinds, and a kind of is normal force, and another kind is tangential force.Definition and perpendicular the making a concerted effort of the place ahead far away incoming flow are lift, and come consistent the making a concerted effort of flow path direction to be resistance with a distant place.Lift and resistance are typically expressed as nondimensional lift coefficient and resistance coefficient.The lift coefficient of aerofoil profile and resistance coefficient can form lift efficiency and drag characteristic curve with angle of attack variation.Originally the lift coefficient of aerofoil profile is along with the increase of the angle of attack, and after the angle of attack reached certain value, lift coefficient had just reached its maximum value, and this value is designated as maximum lift coefficient.

Ratio of lift coefficient to drag coefficient refers to the ratio of wing section lift coefficient and resistance coefficient.

Design lift coefficient refers to corresponding lift coefficient when ratio of lift coefficient to drag coefficient is maximum.

Definite method of design objective of the present invention is: according to aforementioned high efficiency, a low property, coarse immunity, good Study on Variable Condition Features and the level and smooth stalling characteristics judgement schematics of carrying the DU series aerofoil profile and the NACA aerofoil profile that are widely used on the pneumatic equipment blades made are analyzed, proposed to be applied to pneumatic equipment blades made outside relative thickness less than the aeroperformance design objective of 25% aerofoil profile.

The design method of the Blades For Horizontal Axis Wind special airfoil that the present invention proposes, the Inverse Design Method of Airfoil based on general may further comprise the steps: given aerofoil profile goal pressure distributes and initial baseline airfoil; The pressure distribution of adjusting baseline airfoil obtains middle aerofoil profile; Use the Euler equation to calculate the pressure distribution of middle aerofoil profile; The pressure distribution of aerofoil profile and goal pressure distribute relatively, difference degree according to the two judges whether that needs continue to adjust middle aerofoil profile, if described difference degree is in the margin of error that allows, then stop described adjustment, obtain the target aerofoil profile, otherwise the pressure distribution of aerofoil profile in the middle of continue adjusting is until till the pressure distribution of middle aerofoil profile meets the demands; Wherein, described aerofoil profile goal pressure distribute comprise that aerofoil profile goal pressure under the design angle of attack distributes and critical stall angle under the aerofoil profile goal pressure distribute: in the aerofoil profile goal pressure distribution under the described design angle of attack, pressure peak on the suction surface is in distance aerofoil profile leading edge point 1-25% chord length position, all has mild adverse pressure gradient from aerofoil profile suction surface leading edge to 40% chord length position, to obtain less resistance coefficient and higher design lift coefficient; During aerofoil profile goal pressure under described critical stall angle distributed, the pressure peak on the suction surface was in distance aerofoil profile leading edge point 0-1% chord length position, with the maximum lift coefficient of control aerofoil profile; In the design process, constraint aerofoil profile maximum ga(u)ge position is in 34.0%-37.0% chord length position.

For the relative thickness that is applied to the blade outside less than or equal to 25% aerofoil profile, described judge whether to need to continue to adjust in the middle of in the step of aerofoil profile, whether each aerodynamic parameter of aerofoil profile satisfies following condition in the middle of also needing further to judge:

(a) high efficiency:

Maximum lift-drag ratio: ${\left(\frac{C_l}{C_d}\right)}_{\max }>150,$

Design lift coefficient: C _Ldesign1.16;

(b) low carrying property: maximum lift coefficient C _LmaxWith design lift coefficient C _LdesignSatisfy

(c) coarse immunity: $0.85\&le;\frac{C_{\mathrm{ldesign}}^{\&prime;}}{C_{\mathrm{ldesign}}}\&le;1,$

(d) good Study on Variable Condition Features:

Δα=α _stall-α _design≥5， $0<\frac{C_{l\max }-C_{\mathrm{ldesign}}}{\mathrm{\&Delta;\&alpha;}}<0.05,$ $\frac{|{\left(\frac{C_l}{C_d}\right)}_{\mathrm{stall}}-{\left(\frac{C_l}{C_d}\right)}_{\max }|}{\mathrm{\&Delta;\&alpha;}}<21;$

(e) level and smooth stalling characteristics:

${\left(\frac{{(\mathrm{Cl}-{\mathrm{Cl}}_{\max })}^2}{\mathrm{\&alpha;}-{\mathrm{\&alpha;}}_{\mathrm{stall}}}\right)}_{\max }<0.005,0<\mathrm{\&alpha;}-{\mathrm{\&alpha;}}_{\mathrm{stall}}<10,$

Above various in:

C ' _LdesignDesign lift coefficient for coarse condition Airfoil;

C _l, C _d, C _Ldesign, _Clmax,

Lift coefficient, resistance coefficient, design lift coefficient, maximum lift coefficient, maximum lift-drag ratio for design angle of attack Airfoil under the smoothness condition;

Ratio of lift coefficient to drag coefficient for smoothness condition lower critical stall angle Airfoil;

α, α _Stall, that Δ α is respectively the angle of attack, stall angle, the angle of attack is poor.

In design in order to make aerofoil profile have high design lift coefficient and high maximum lift-drag ratio, in the pressure peak of design point constraint aerofoil profile away from the aerofoil profile leading edge, to reduce the unfavorable contrary length of pressing section of aerofoil profile.And control all has lower adverse pressure gradient from aerofoil profile suction surface leading edge to 40% chord length position, keeps aerofoil profile to have long laminar region, thereby obtains less resistance coefficient.

Be the maximum lift coefficient of restriction aerofoil profile, the confining pressure peak value is near the aerofoil profile leading edge near the critical angle of attack of aerofoil profile, and turning point moves forward rapidly, makes aerofoil profile occur separating, thereby reduces its maximum lift coefficient.Control simultaneously the maximum ga(u)ge position of aerofoil profile in the 34.0%-37.0% chord length.

The coarse meeting of leading edge causes that the laminar boundary layer of aerofoil profile turns in advance twists, thereby separates in advance, causes lift coefficient to descend.By suitably controlling the upper surface thickness of aerofoil profile, reach the maximum ga(u)ge position in the design, to reduce adverse pressure gradient, control separates, and reduces design lift to the coarse receptance of leading edge.To the middle aerofoil profile that obtains in the design, by arranging fixedly to turn and twist in upper surface 1% chord length, lower surface 10% chord length position, analyze the coarse immunity of designed aerofoil profile.

The relative thickness that the design objective that the present invention adopts above-mentioned design method and design means to design to reach the present invention to propose quantizes to require is 18%, 21%, 25% 3 aerofoil profile.The aerofoil profile of developing is applicable to middle part and the outside of the above wind energy conversion system of MW level, can reach the purpose that reduces blade loading when improving the pneumatic equipment blades made output power.

Fig. 1 is how much molded line of 18%, 21%, 25% 3 aerofoil profile for the relative thickness of the design method among employing the present invention and means exploitation.Carry out analysis verification as an example of the aerofoil profile of relative thickness as 25% example, Fig. 2,3 is that designed 25% thickness aerofoil profile is in the pressure distribution of design point and critical angle of attack, can find out designed aerofoil profile in the pressure peak of design point away from leading edge, in 1.4% chord length position, mild to 40% chord length internal pressure graded in leading edge.When critical angle of attack, pressure peak is near leading edge, in 0.22% chord length position.The maximum ga(u)ge position of this aerofoil profile is in 34.6% chord length simultaneously.The pneumatic special parameter that designed aerofoil profile and DU91-W-250 aerofoil profile compare is as shown in table 1.

25% aerofoil profile of table 1 the present invention design and the contrast of DU91-W-250 Airfoil Aerodynamic Performance

As seen from Table 1, the design's aerofoil profile 25% aerofoil profile is compared with the DU91-W-250 aerofoil profile and is had following characteristic:

(1) high efficiency: maximum lift-drag ratio reaches more than 150, and design lift coefficient 1.27 is greater than designing requirement value 1.16, and greater than the design lift coefficient 1.19 of DU91-W1-250 aerofoil profile;

(2) low carrying property: maximum lift coefficient and design lift coefficient ratio 1.14 are worth 1.25 less than designing requirement, and less than 1.22 of DU91-W1-250 aerofoil profile;

(3) coarse immunity is lower slightly: its parameter value 0.85 is slightly less than 0.89 of DU91-W1-250 aerofoil profile, but satisfies the design objective requirement;

(4) better Study on Variable Condition Features: its corresponding parameter value 0.035 is worth 21 less than designing requirement value 0.05,17.4 less than designing requirement;

(5) level and smooth stalling characteristics: its parameter value 0.0048 is worth 0.005 less than designing requirement, and less than 0.0066 of DU91-W1-250 aerofoil profile.

By above analysis, 25% aerofoil profile indices parameter of the present invention design meets design requirement, except a coarse immunity a little less than the DU91-W1-250 aerofoil profile, other performances all are higher than this aerofoil profile.Therefore the whole aeroperformance of the design's relative thickness 25% aerofoil profile is better than the DU91-W1-250 aerofoil profile.

For further verifying above-mentioned result of implementation, it is that example is analyzed its power and load that designed 25% aerofoil profile replacement DU91-W1-250 aerofoil profile is applied to the 42.8m1.5MW pneumatic equipment blades made.Draw, replace by aerofoil profile, pneumatic equipment blades made is at 8m/s---and output power improves 1% between the 10.3m/s (10.3m is rated wind speed).The maximum lift coefficient of two aerofoil profiles of limit load only differs from 0.01, and its limit load slightly reduces, and is the 1.83e5N magnitude, reaches control load and puies forward high-power purpose.

Claims (4)

1. the design method of a Blades For Horizontal Axis Wind special airfoil, the Inverse Design Method of Airfoil based on general is characterized in that, described design method may further comprise the steps:

Given aerofoil profile goal pressure distributes and initial baseline airfoil;

The pressure distribution of adjusting baseline airfoil obtains middle aerofoil profile;

Use the Euler equation to calculate the pressure distribution of middle aerofoil profile;

The pressure distribution of aerofoil profile and goal pressure distribute relatively, difference degree according to the two judges whether that needs continue to adjust middle aerofoil profile, if described difference degree is in the margin of error that allows, then stop described adjustment, obtain the target aerofoil profile, otherwise the pressure distribution of aerofoil profile in the middle of continue adjusting is until till the pressure distribution of middle aerofoil profile meets the demands;

Wherein,

Described aerofoil profile goal pressure distribute comprise that aerofoil profile goal pressure under the design angle of attack distributes and critical stall angle under the aerofoil profile goal pressure distribute: in the aerofoil profile goal pressure distribution under the described design angle of attack, pressure peak on the suction surface is in distance aerofoil profile leading edge point 1-25% chord length position, all has mild adverse pressure gradient from aerofoil profile suction surface leading edge to 40% chord length position, to obtain little resistance coefficient and high design lift coefficient; During aerofoil profile goal pressure under described critical stall angle distributed, the pressure peak on the suction surface was in distance aerofoil profile leading edge point 0-1% chord length position, with the maximum lift coefficient of control aerofoil profile;

In the design process, constraint aerofoil profile maximum ga(u)ge position is in 34.0%-37.0% chord length position.

2. design method according to claim 1, it is characterized in that, for the relative thickness that is applied to the blade outside less than or equal to 25% aerofoil profile, need to continue to adjust in the step of middle aerofoil profile described judging whether, whether each aerodynamic parameter of aerofoil profile satisfies following condition in the middle of also needing further to judge:

(a) high efficiency:

Maximum lift-drag ratio: ${\left(\frac{C_l}{C_d}\right)}_{\max }>150,$

Design lift coefficient: C _Ldesign1.16;

(b) low carrying property: maximum lift coefficient C _LmaxWith design lift coefficient C _LdesignSatisfy

(c) coarse immunity: $0.85\&le;\frac{C_{\mathrm{ldesign}}^{\&prime;}}{C_{\mathrm{ldesign}}}\&le;1,$

(d) good Study on Variable Condition Features:

Δα=α _stall-α _design≥5， $0<\frac{C_{l\max }-C_{\mathrm{ldesign}}}{\mathrm{\&Delta;\&alpha;}}<0.05,$ $\frac{|{\left(\frac{C_l}{C_d}\right)}_{\mathrm{stall}}-{\left(\frac{C_l}{C_d}\right)}_{\max }|}{\mathrm{\&Delta;\&alpha;}}<21;$

(e) level and smooth stalling characteristics:

${\left(\frac{{(\mathrm{Cl}-{\mathrm{Cl}}_{\max })}^2}{\mathrm{\&alpha;}-{\mathrm{\&alpha;}}_{\mathrm{stall}}}\right)}_{\max }<0.005,0<\mathrm{\&alpha;}-{\mathrm{\&alpha;}}_{\mathrm{stall}}<10,$

Above various in:

C ' _LdesignDesign lift coefficient for coarse condition Airfoil;

C _l, C _d, C _Ldesign, C _Lmax,

Lift coefficient, resistance coefficient, design lift coefficient, maximum lift coefficient, maximum lift-drag ratio for design angle of attack Airfoil under the smoothness condition;

Be light

The ratio of lift coefficient to drag coefficient of sliding condition lower critical stall angle Airfoil;

α, α _Stall, that Δ α is respectively the angle of attack, stall angle, the angle of attack is poor.

3. design method according to claim 2 is characterized in that, the design lift coefficient C ' of the coarse condition Airfoil of described calculating _LdesignStep, be to the middle aerofoil profile that obtains in the design, by arranging and fixedly turn the design lift coefficient that calculates when twisting in upper surface 1% chord length, lower surface 10% chord length position.

4. the Blades For Horizontal Axis Wind special airfoil that obtains to the design method of 3 each described Blades For Horizontal Axis Wind special airfoils according to claim 1.

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