CN103047079B - 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

One efficiently low year Blades For Horizontal Axis Wind special airfoil and design method thereof

Technical field

The present invention relates to a kind of special airfoil design method of Blades For Horizontal Axis Wind, particularly relate to a kind of based on mimetic design method there is efficiently low year, 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 turbines, 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 loading demands, we wish that wind energy conversion system has higher output power, and the impact of increase on wind electricity blade can again with lower load, particularly limit load is simultaneously larger.

Vane design of wind turbines requires that Special Airfoil of Wind Turbine has high maximum lift coefficient, to improve the aerofoil profile of the output power of blade, particularly blade outboard all the time.But actual Leaf operates near operating point for design more, instead of near maximum lift coefficient, and high design lift coefficient can reduce the chord length of aerofoil profile, to reduce weight, the reduction load of blade.And maximum lift coefficient is very little on the impact of the output power of blade, the increase of maximum lift coefficient can cause the increase of blade limit load on the contrary.

In wind energy conversion system running, due to fitful wind impact or control the various factors such as not in time, under wind energy conversion system can not operate in design conditions completely, require that wind mill airfoil has good Study on Variable Condition Features and level and smooth stalling characteristics.

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

In prior art, there is multiple Airfoil Design method, common are various forms of intelligent optimized design method, as now widely used based on the Optimization Design of genetic algorithm, another common Airfoil Design method is indirect problem design method, no matter use any design method can obtain suitable aerofoil profile, but in 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 designed based on this theory in use often shows efficiency, load is larger waits deficiency, which greatly limits the development of pneumatic equipment blades made.

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 to there is efficiently low year, 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 operating point for design (namely designing the angle of attack) more, instead of near maximum lift coefficient.Can be drawn by the formula of following power p, from Airfoil Aerodynamic Performance, improve the maximum lift-drag ratio of aerofoil profile with design lift coefficient C _lit is the key improving blade output power.And high design lift coefficient can reduce the chord length of aerofoil profile, to reduce weight, the reduction load of blade.

$\mathrm{dp}==\frac{1}{2}\mathrm{\ρ}{V_0}^2\mathrm{c\Ω}(C_l\sin \mathrm{\φ}-C_d\cos \mathrm{\φ})\mathrm{rdr}=\frac{1}{2}\mathrm{\ρ}{V_0}^2\mathrm{c\Ω}{C}_l\sin \mathrm{\φ}(1-\frac{1}{\frac{C_l}{C_d}\mathrm{tg\φ}})\mathrm{rdr}$

The aerodynamic load acted on pneumatic equipment blades made waves the shearing force F in direction _xbit is the principal element affecting blade limit load.By F _xbcalculating formula can find out, the maximum lift coefficient of aerofoil profile is higher, and the limit load produced can be larger, therefore will limit the maximum lift coefficient of aerofoil profile in design.

${\mathrm{dF}}_{\mathrm{xb}}=\frac{1}{2}\mathrm{\ρ}{V_0}^{2}c{C}_n=\frac{1}{2}\mathrm{\ρ}{V_0}^{2}c(C_l\sin \mathrm{\φ}-C_d\cos \mathrm{\φ})\mathrm{dr}$

In addition due in wind energy conversion system running, due to fitful wind impact or control the various factors such as not in time, under wind energy conversion system can not operate in design conditions completely, require that wind mill airfoil has good Study on Variable Condition Features and level and smooth stalling characteristics.

Draw according to above-mentioned analysis a kind of there is efficiently low year, the Blades For Horizontal Axis Wind special airfoil of good variable working condition and level and smooth stalling characteristics should have following aerodynamic characteristic: there is high maximum lift-drag ratio, high design lift coefficient, have compared with low maximum lift coefficient, design lift coefficient declines less and good Study on Variable Condition Features and level and smooth stalling characteristics under the coarse condition of leading edge.

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

A design method for Blades For Horizontal Axis Wind special airfoil, based on general Inverse Design Method of Airfoil, is characterized in that, described design method comprises the following steps:

Given aerofoil profile prescribed pressure distribution and initial baseline airfoil;

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

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

The pressure distribution of relatively middle aerofoil profile and prescribed pressure distribution, judge whether to need to continue aerofoil profile in the middle of adjustment according to the difference degree of the two, if described difference degree is in the margin of error allowed, then stop described adjustment, obtain target aerofoil profile, otherwise, continue the pressure distribution of aerofoil profile in the middle of adjustment, till the pressure distribution of middle aerofoil profile meets the demands;

Wherein,

Described aerofoil profile prescribed pressure distribution comprises the aerofoil profile prescribed pressure distribution under the design angle of attack and the aerofoil profile prescribed pressure distribution under critical stall angle: in the aerofoil profile prescribed pressure distribution under the described design angle of attack, pressure peak on suction surface is at distance aerofoil profile leading edge point 1-25% chord positions place, to 40% chord positions, all there is mild adverse pressure gradient from aerofoil profile suction surface leading edge, to obtain less resistance coefficient and higher design lift coefficient; In aerofoil profile prescribed pressure distribution under described critical stall angle, the pressure peak on suction surface distance aerofoil profile leading edge point 0-1% chord positions place, to control the maximum lift coefficient of aerofoil profile;

In design process, constraint aerofoil profile maximum ga(u)ge position is at 34.0%-37.0% chord positions place.

Preferably, be less than or equal to the aerofoil profile of 25% for the relative thickness being applied to blade outboard, judge whether in the step needing to continue aerofoil profile in the middle of adjustment described, also need each aerodynamic parameter of aerofoil profile in the middle of judging further whether to meet following condition:

(a) high efficiency:

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

Design lift coefficient: C _ldesign>1.16;

(b) low year property: maximum lift coefficient C _lmaxwith design lift coefficient C _ldesignmeet

(c) coarse immunity: $0.85\≤\frac{C_{\mathrm{ldesign}}^{\′}}{C_{\mathrm{ldesign}}}\≤1,$

D Study on Variable Condition Features that () is good:

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 stalling characteristics that () is level and smooth:

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

In various above:

C ' _ldesignfor the design lift coefficient of coarse condition Airfoil;

C _l, C _d, C _ldesign, C _lmax, for designing lift coefficient, resistance coefficient, design lift coefficient, maximum lift coefficient, the maximum lift-drag ratio of angle of attack Airfoil under smoothness condition; for the ratio of lift coefficient to drag coefficient of smoothness condition lower critical stall angle Airfoil;

α, α _stall, Δ α is respectively the angle of attack, stall angle, the angle of attack are poor.

Further, the design lift coefficient C ' of the coarse condition Airfoil of described calculating _ldesignstep, be to middle the aerofoil profile that obtains in design, by arranging the fixing turn of design lift coefficient calculated when twisting at upper surface 1% chord length, lower surface 10% chord positions.

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

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

Summary of the invention

Accompanying drawing explanation

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

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

Fig. 3 for the relative thickness that the present invention designs be 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.

Power suffered by aerofoil profile is that the distributed force acting on upper and lower surface is made a concerted effort, and surface force has two kinds, and one is normal force, and another kind is tangential force.Definition and perpendicular the making a concerted effort for lift of front far away incoming flow, and carry out consistent the making a concerted effort for resistance of flow path direction 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, with angle of attack variation, can form lift efficiency and resistance curve.Originally the lift coefficient of aerofoil profile is along with the increase of the angle of attack, and after the angle of attack reaches certain value, lift coefficient just reaches 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 the lift coefficient corresponding when ratio of lift coefficient to drag coefficient is maximum.

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

The design method of the Blades For Horizontal Axis Wind special airfoil that the present invention proposes, based on general Inverse Design Method of Airfoil, comprises the following steps: given aerofoil profile prescribed pressure distribution and initial baseline airfoil; The pressure distribution of adjustment baseline airfoil obtains middle aerofoil profile; Euler equation is used to calculate the pressure distribution of middle aerofoil profile; The pressure distribution of relatively middle aerofoil profile and prescribed pressure distribution, judge whether to need to continue aerofoil profile in the middle of adjustment according to the difference degree of the two, if described difference degree is in the margin of error allowed, then stop described adjustment, obtain target aerofoil profile, otherwise, continue the pressure distribution of aerofoil profile in the middle of adjustment, till the pressure distribution of middle aerofoil profile meets the demands; Wherein, described aerofoil profile prescribed pressure distribution comprises the aerofoil profile prescribed pressure distribution under the design angle of attack and the aerofoil profile prescribed pressure distribution under critical stall angle: in the aerofoil profile prescribed pressure distribution under the described design angle of attack, pressure peak on suction surface is at distance aerofoil profile leading edge point 1-25% chord positions place, to 40% chord positions, all there is mild adverse pressure gradient from aerofoil profile suction surface leading edge, to obtain less resistance coefficient and higher design lift coefficient; In aerofoil profile prescribed pressure distribution under described critical stall angle, the pressure peak on suction surface distance aerofoil profile leading edge point 0-1% chord positions place, to control the maximum lift coefficient of aerofoil profile; In design process, constraint aerofoil profile maximum ga(u)ge position is at 34.0%-37.0% chord positions place.

Be less than or equal to the aerofoil profile of 25% for the relative thickness being applied to blade outboard, judge whether in the step needing to continue aerofoil profile in the middle of adjustment described, also need each aerodynamic parameter of aerofoil profile in the middle of judging further whether to meet following condition:

(a) high efficiency:

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

Design lift coefficient: C _ldesign>1.16;

(b) low year property: maximum lift coefficient C _lmaxwith design lift coefficient C _ldesignmeet

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

D Study on Variable Condition Features that () is good:

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 stalling characteristics that () is level and smooth:

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

In various above:

C ' _ldesignfor the design lift coefficient of coarse condition Airfoil;

C _l, C _d, C _ldesign, _clmax, for designing lift coefficient, resistance coefficient, design lift coefficient, maximum lift coefficient, the maximum lift-drag ratio of angle of attack Airfoil under smoothness condition; for the ratio of lift coefficient to drag coefficient of smoothness condition lower critical stall angle Airfoil;

α, α _stall, Δ α is respectively the angle of attack, stall angle, the angle of attack are poor.

In the design in order to make aerofoil profile have high design lift coefficient and high maximum lift-drag ratio, retrain the pressure peak of aerofoil profile away from aerofoil profile leading edge at design point, to reduce the length of the unfavorable inverse pressure section of aerofoil profile.And control to 40% chord positions, all to there is lower adverse pressure gradient from aerofoil profile suction surface leading edge, keep aerofoil profile to have longer laminar region, thus obtain less resistance coefficient.

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

The coarse meeting of leading edge causes the laminar boundary layer of aerofoil profile to turn in advance to twist, thus is separated in advance, causes lift coefficient to decline.By suitably controlling the upper surface thickness of aerofoil profile in design, and maximum ga(u)ge position, to reduce adverse pressure gradient, controlling to be separated, reducing design lift to the coarse receptance of leading edge.To the middle aerofoil profile obtained in design, by arranging fixing turning twist at upper surface 1% chord length, lower surface 10% chord positions, 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 have devised to reach the present invention to propose quantizes to require is 18%, 21%, 25% 3 aerofoil profile.Develop middle part and the outside that aerofoil profile is applicable to the above wind energy conversion system of MW level, the object reducing blade loading while improving pneumatic equipment blades made output power can be reached.

Fig. 1 adopts the relative thickness of the design method in the present invention and means exploitation to be the geometry molded line of 18%, 21%, 25% 3 aerofoil profile.Analysis verification is carried out for the aerofoil profile that relative thickness is 25%, Fig. 2,3 is designed 25% thickness aerofoil profile in the pressure distribution of design point and critical angle of attack, can find out that the pressure peak of designed aerofoil profile at design point is away from leading edge, at 1.4% chord positions, mild to 40% chord length internal pressure graded in leading edge.When critical angle of attack, pressure peak near leading edge, at 0.22% chord positions.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 and the DU91-W-250 Airfoil Aerodynamic Performance of table 1 the present invention design contrast

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

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

(2) low year property: maximum lift coefficient and design lift coefficient ratio 1.14 are less than designing requirement value 1.25, and are 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 meets design objective requirement;

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

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

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

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

Claims (2)

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

Given aerofoil profile prescribed pressure distribution and initial baseline airfoil;

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

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

The pressure distribution of relatively middle aerofoil profile and prescribed pressure distribution, judge whether to need to continue aerofoil profile in the middle of adjustment according to the difference degree of the two, if described difference degree is in the margin of error allowed, then stop described adjustment, obtain target aerofoil profile, otherwise, continue the pressure distribution of aerofoil profile in the middle of adjustment, till the pressure distribution of middle aerofoil profile meets the demands;

Wherein,

Described aerofoil profile prescribed pressure distribution comprises the aerofoil profile prescribed pressure distribution under the design angle of attack and the aerofoil profile prescribed pressure distribution under critical stall angle: in the aerofoil profile prescribed pressure distribution under the described design angle of attack, pressure peak on suction surface is at distance aerofoil profile leading edge point 1-25% chord positions place, to 40% chord positions, all there is mild adverse pressure gradient from aerofoil profile suction surface leading edge, to obtain little resistance coefficient and high design lift coefficient; In aerofoil profile prescribed pressure distribution under described critical stall angle, the pressure peak on suction surface distance aerofoil profile leading edge point 0-1% chord positions place, to control the maximum lift coefficient of aerofoil profile;

In design process, constraint aerofoil profile maximum ga(u)ge position is at 34.0%-37.0% chord positions place;

Be less than or equal to the aerofoil profile of 25% for the relative thickness being applied to blade outboard, judge whether in the step needing to continue aerofoil profile in the middle of adjustment described, also need each aerodynamic parameter of aerofoil profile in the middle of judging further whether to meet following condition:

(a) high efficiency:

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

Design lift coefficient: C _ldesign>1.16;

(b) low year property: maximum lift coefficient C _{l max}with design lift coefficient C _ldesignmeet

(c) coarse immunity:

D Study on Variable Condition Features that () is good:

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 stalling characteristics that () is level and smooth:

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

In various above:

C ' _ldesignfor the design lift coefficient of coarse condition Airfoil;

C _l, C _d, C _ldesign, C _{l max}, for designing lift coefficient, resistance coefficient, design lift coefficient, maximum lift coefficient, the maximum lift-drag ratio of angle of attack Airfoil under smoothness condition; for the ratio of lift coefficient to drag coefficient of smoothness condition lower critical stall angle Airfoil;

α, α _stall, Δ α, α _designbe respectively that the angle of attack, stall angle, the angle of attack are poor, the design angle of attack.

2. design method according to claim 1, is characterized in that, the design lift coefficient C ' of the coarse condition Airfoil of described calculating _ldesignstep, be to middle the aerofoil profile that obtains in design, by arranging the fixing turn of design lift coefficient calculated when twisting at upper surface 1% chord length, lower surface 10% chord positions.