CN104408260A - Design method for blade airfoil of tidal current energy water turbine - Google Patents

Abstract

The invention discloses a design method for a blade airfoil of a tidal current energy water turbine. In the method, the various requirements on design of the blade of the water turbine, including lift coefficient, resistance coefficient, lift-drag ratio, cavitation phenomenon and the like, are comprehensively considered; comprehensive estimation can be performed on the airfoil of the water turbine according to different design requirements by the selected target function. The transverse coordinates and the longitudinal coordinates of a head edge tangent, a tail edge tangent and control points of upper and lower curves of the airfoil are used as design variables. A cubic spline curve is adopted and has higher fitting accuracy. The hydrodynamic performance, the pressure distribution and the like of the hydrofoil shape are calculated by using FLUENT or CFX computational fluid dynamic software or XFOIL airfoil estimation software and the like, so the accuracy for computation is fully guaranteed. The hydrofoil shape design method is based on a genetic optimal algorithm, so a global optimal solution can be obtained. The hydrodynamic performance of the blade airfoil of the tidal current energy water turbine can be improved, and the maximum pressure coefficient of the surface can also be reduced, so that the purpose of avoiding cavitation phenomenon is achieved.

Description

A kind of tidal current energy water turbine vane airfoil profile method for designing

Technical field

The invention belongs to field of renewable energy, be specifically related to a kind of vane airfoil profile method for designing for the Design trend energy hydraulic turbine, can be used for all types of hydraulic turbine Airfoil Design.

Background technology

Along with the development of world economy, energy resource consumption gets more and more.The problems such as the environmental pollution brought due to fossil energy crisis and traditional energy and carbon emission, make the regenerative resource cleaned become more and more important.Marine tidal-current energy is a kind of very important new forms of energy, have reliably, periodically, the widely distributed and advantage such as sustainable, marine tidal-current energy will be played an important role in the energy in future.In order to utilize marine tidal-current energy, the hydraulic turbine is used as main energy capture device.Therefore the ability capture rate how improving tidal current energy water turbine becomes to be affected marine tidal-current energy and to generate electricity the key factor applied.

Hydrofoil profile, as one of most important factor of composition blade profile, has material impact to the energy conversion efficiency of tidal current energy water turbine.At present, known aerofoil profile all considers that the designing requirement such as Aero-Space and wind energy conversion system obtained substantially, and the special hydrofoil profile about tidal current energy water turbine is few, and Airfoil Design method is few especially.

Mainly there is two large problems in the Airfoil Design method of traditional application in Aero-Space and wind energy conversion system: one is that hydrofoil profile has some to be different from the particular design requirement of Aero-Space and wind energy conversion system, can not be suitable in the Airfoil Design method of Aero-Space and wind energy conversion system; Two be most of method for designing mostly based on single goal, and the Airfoil Design target of reality is very complicated, needs to consider that multiple goal could obtain rational aerofoil profile; Three is most of methods for designing is optimization methods based on sensitivity analysis, is difficult to obtain globally optimal solution.Along with carrying out of China's marine tidal-current energy power station project, in order to develop the tidal current energy water turbine with independent intellectual property right, complete Airfoil Design method must be set up.

Summary of the invention

The object of the invention is to the shortcoming and defect overcoming above-mentioned prior art, propose a kind of tidal current energy water turbine vane airfoil profile method for designing.

For solving above technical matters, the technical solution adopted in the present invention is:

Step one: according to designing requirement determination design variable and objective function, sets up hydrofoil profile Optimized model;

Step 2: determine the computing method of hydrodynamic performance and pressure coefficient and the fitness function of genetic algorithm;

Step 3: generate initial population, and matching hydrofoil profile curve;

Step 4: generate hydrofoil profile fluid mass grid model, calculate and export hydrodynamic performance, and exporting the information such as lift, resistance and pressure;

Step 5: according to hydrodynamic force coefficient and pressure coefficient calculating target function, assesses according to fitness function, judges whether convergence, and convergence then terminates to optimize, otherwise generates new population, returns step 3.

The method considers and comprises lift coefficient, resistance coefficient, the various requirement that lift-drag ratio and cavitation phenomenon etc. design at interior turbine blade, selected objective function can carry out comprehensive assessment according to different designing requirements to hydraulic turbine aerofoil profile, choose first edge tangent line, in trailing edge tangent line and aerofoil profile on lower curve the horizontal ordinate at reference mark and ordinate as design variable, have employed cubic spline curve, there is higher fitting precision, have employed FLUENT or CFX cfdrc or XFOIL aerofoil profile estimation software etc. to calculate the hydrodynamic performance of hydrofoil profile and pressure distribution etc., fully ensure that the accuracy of calculating, hydrofoil profile method for designing is based on genetic Optimization Algorithm, globally optimal solution can be obtained.

The invention has the advantages that:

1) relative to traditional Design of Hydraulic Turbine method, the present invention has considered the various aspects of hydraulic turbine hydrofoil profile design, can require to obtain best hydrofoil profile curve according to different waters and marine environment.

2) to propose in method for designing design variable and to select and curve-fitting method can the real hydrofoil profile curve of accurate description, design space can be expanded as much as possible,

3) relative to traditional optimization, genetic algorithm of the present invention have feasible solution represent popularity, collective search, random search and of overall importance etc. a little, can globally optimal solution be obtained.

Accompanying drawing explanation

Fig. 1 is the tidal current energy water turbine Airfoil Design method flow in the present invention;

Fig. 2 is hydrofoil profile in the present invention and design variable thereof;

Fig. 3 is the target lift coefficient curve in the present invention;

Fig. 4 is the cavitation phenomenon of the hydraulic turbine hydrofoil profile in the present invention;

Fig. 5 is different designs hydrofoil profile comparison of design in embodiment in the present invention;

Fig. 6 is the pressure distribution contrast in the present invention in embodiment in different designs objective function situation;

Fig. 7 is the lift coefficient contrast in the present invention in embodiment in different designs objective function situation;

Fig. 8 is the resistance coefficient contrast in the present invention in embodiment in different designs objective function situation;

Fig. 9 is the lift-drag ratio contrast in the present invention in embodiment in different designs objective function situation;

In figure:

1, hydrofoil; 2, Curve of wing; 3, aerofoil profile center line; 4, leading edge;

5, trailing edge; 6, reference mark; 7, reference mark design domain; 8, traditional lift coefficient curve;

9, target lift coefficient curve

Embodiment

Below in conjunction with drawings and Examples, the present invention is described in detail.

As shown in Figure 1, tidal current energy water turbine hydrofoil 1 Airfoil Design method proposed by the invention includes optimizes module, objective function module and performance calculating module.

Optimize module and mainly generate preliminary design scheme, the hydrodynamic performance of new hydrofoil 1 aerofoil profile scheme is assessed, and generate new Airfoil Design parameter on original design proposal basis.

Objective function module major function generates new geometric configuration, extraction and analysis result from Fluid Mechanics Computation analysis result according to hydrofoil 1 aerofoil profile parameter, and obtain objective function according to result of calculation.

The major function of performance calculating module generates discrete grid block data according to geometric configuration, and adopt FLUENT or CFX or XFOIL software to calculate the lift coefficient of hydrofoil 1 aerofoil profile, resistance coefficient and pressure distribution etc., for objective function module provides basis.

According to above three modules, the present invention adopts genetic algorithm to be optimized design to tidal current energy water turbine hydrofoil 1 aerofoil profile, and the hydrofoil 1 aerofoil optimization method proposed calculates carries out in accordance with the following steps.

The first step, according to designing requirement determination design variable and objective function, sets up hydrofoil 1 aerofoil optimization model.

Design variable is directly related to hydrofoil 1 aerofoil profile, therefore how addressing sampling spot method and curve-fitting method particularly important.Choosing of objective function, the performance of hydrofoil 1 aerofoil profile out designed by being directly connected to, needs to set flexibly according to design needs.

Be illustrated in figure 2 a typical hydrofoil 1, aerofoil profile center line 3 is connected between leading edge 4 and trailing edge 5, on the Curve of wing 2 of hydrofoil 1, the reference mark 6 of more than at least four is chosen according to preliminary design scheme, reference mark 6 is the point on Curve of wing 2, the position at reference mark 6 can be moved by the horizontal ordinate or ordinate size changing reference mark 6, thus Curve of wing 2 shape can be changed, and then reach the object improving hydrofoil 1 hydrodynamic performance, the horizontal ordinate that reference mark design domain 7 is reference mark 6 and the design space that ordinate bound surrounds, wherein the upper and lower Curve of wing 2 of hydrofoil gets m and n reference mark respectively, in order to control the shape of hydrofoil 1 leading edge and trailing edge, using the tangent line of leading edge and trailing edge also as design variable, design variable x is shown below.

x＝(x ₀₀,x ₁₁,y ₁₁,x ₁₂,y ₁₂,...,x _1m,y _1m,x ₂₁,x ₂₁,x ₂₂,y ₂₂,...,x _2n,y _2n,x ₀₁)

Wherein x ₀₀and x ₀₁be respectively the tangent line size of hydrofoil 1 aerofoil profile leading edge and trailing edge, (x _1m, y _1m) and (x _2n, y _2n) be respectively reference mark 6 coordinate on the upper and lower Curve of wing 2 of hydrofoil, x _2nand x _1mfor the horizontal ordinate at hydrofoil upper and lower Curve of wing 2 reference mark 6, and y _1mand y _2nfor the ordinate at hydrofoil upper and lower Curve of wing 2 reference mark 6.

Turbine blade has different designing requirements along exhibition to direction diverse location, near blade outside left, require that aerofoil profile has larger lift coefficient and lift-drag ratio, and less resistance coefficient, make to adopt less chord length just can reach the hydrodynamic load of specifying.From the angle of hydrodynamics design, the lift-drag ratio of tip region is of paramount importance parameter.Load suffered by the hydraulic turbine is comparatively large, in order to meet the requirement of structural design, and the aerofoil profile that general employing is thicker.Owing to bearing great load near wing root position, in order to the needs of arrangement, therefore must there be special requirement to profile thickness, but now can sacrifice larger hydrodynamic performance again.In order to make the hydrodynamic performance of the hydraulic turbine reach optimum, therefore arranging different aerofoil profiles along spanwise, needing to require to design specific aerofoil profile according to different designs.Therefore design object is divided into two classes by the present invention, and a class is basic hydrodynamic performance, includes lift coefficient, resistance coefficient and lift-drag ratio, is directly connected to the energy conversion efficiency of the hydraulic turbine; Equations of The Second Kind is pressure coefficient, is directly connected to cavitation phenomenon, may affect serviceable life and the reliability of the hydraulic turbine.

First for hydrodynamic performance.For the aerofoil profile in wind energy conversion system field, pneumatic equipment blades may be in stall region, and after the angle of attack arrives stalling point, pneumatic efficiency may sharply decline.Be illustrated in figure 3 traditional lift coefficient curve 8 and the contrast of target lift coefficient curve 9, traditional aerofoil profile may cause the sharply decline of lift coefficient near stalling point, can have an impact to the energy utilization efficiency of tidal current energy water turbine, therefore and be not suitable as hydraulic turbine hydrofoil 1 aerofoil profile.For tidal current energy water turbine, more wish that the change of hydrodynamic performance not along with the angle of attack is too violent, especially in stall region in the design.Therefore the present invention proposes in concrete Airfoil Design, require that burble point slowly moves to trailing edge along with the increase of the angle of attack, is embodied in and is slowly changed along with the increase of the angle of attack by the lift coefficient of target lift coefficient curve 9, fully ensure turbine characteristics.In addition, resistance coefficient, lift-drag ratio etc. equally also can produce material impact to hydraulic turbine hydrofoil 1 hydrodynamic performance.In order to design hydrofoil 1 aerofoil profile of performance the best, the hydrodynamic performances such as lift coefficient, resistance coefficient, lift-drag ratio and pressure coefficient under this just requires objective function to consider multiple various working, carry out Synthetical Optimization.

Secondly for pressure coefficient problem.Bubble will be formed when the pressure of a certain fluid mass is less than cavitation force value.Cavity breaks rapidly because an air ducks in drink, and creates a shock wave.Usually occurred in by type cavity in the physical constructions such as water pumper, screw propeller and impeller.From the angle of fluid design, the cavitation cavity problem caused due to the reason of turbine blade pressure should be considered in turbine blade Airfoil Design, because producing important destruction to hydraulic turbine structure by the produced shock wave that breaks of inertia cavity.Be illustrated in figure 4 the Production conditions of cavitation phenomenon on hydrofoil 1, pressure coefficient distribution there will be a maximal value, as the pressure coefficient C on hydrofoil 1 along with chordwise location distributes _pbe greater than cavitation coefficient, cavitation factor, Toma coefficient σ _ctime will produce cavitation phenomenon.

Cavitation efficiency is defined as follows:

${\mathrm{\σ}}_c=\frac{p_0-p_v}{0.5\mathrm{\ρ}{V}^2}$

Pressure coefficient is defined as follows:

$C_p=\frac{P_L-P_0}{0.5\mathrm{\ρ}{V}^2}$

Wherein p _vfor cavity pressure, p _lfor hydrofoil 1 airfoil surface pressure, depend on the temperature of water.P ₀for local pressure, q is dynamic pressure, V flow rate of water flow.

Cavitation phenomenon is specific problem in Design of Hydraulic Turbine, and the cavitation phenomenon occurred in tidal current energy water turbine operation process directly may produce hydraulic turbine structure and destroy, thus affects shelf life and the reliability of the hydraulic turbine.Therefore need to reduce the possibility that tidal current energy water turbine produces cavitation phenomenon as far as possible.In order to avoid the generation of cavitation phenomenon, need to reduce therefore when carrying out hydrofoil 1 and designing, the maximum pressure coefficient on hydrofoil 1 top should be made as far as possible.But pressure coefficient is directly connected to the hydrodynamic performance such as lift coefficient and lift-drag ratio, lift coefficient can carry out numerical integration acquisition by pressure coefficient along Curve of wing 2.Therefore can realize both can avoiding cavitation phenomenon in two in Optimized model, not lose again the object of hydrodynamic performance.Reduce maximum pressure coefficient as far as possible on the one hand, make pressure coefficient be uniformly distributed along Curve of wing 2 on the other hand as far as possible.In order to avoid the generation of cavitation phenomenon, the present invention proposes pressure coefficient as one of design object function.

Finally, in order to obtain hydrofoil 1 Curve of wing 2 of best performance, objective function combines considers lift coefficient, resistance coefficient, lift-drag ratio and pressure coefficient, in conjunction with design variable, sets up following aerofoil optimization model:

Objective function:

f(x)＝f(C _L,C _L/C _D,C _D,C _pmax)

Constraint condition:

$x_{00}^L\≤x_{00}\≤x_{00}^U$

$x_{01}^L\≤x_{01}\≤x_{01}^U$

$x_{1i}^L\≤x_{1i}\≤x_{1i}^U,i=1...m$

$x_{2j}^L\≤x_{2j}\≤x_{2j}^U,j=1...n$

$y_{1i}^L\≤y_{1i}\≤y_{1i}^U,i=1...m$

$y_{2j}^L\≤y_{2j}\≤y_{2j}^U,j=1...n$

Wherein C _l, C _l/ C _d, C _dand C _pbe respectively the lift coefficient under any situations of attack, lift-drag ratio, resistance coefficient and maximum pressure coefficient, be the function of design variable x. with be respectively the lower bound of leading edge, trailing edge, aerofoil profile upper surface reference mark horizontal ordinate, aerofoil profile upper surface reference mark ordinate, aerofoil profile lower surface reference mark horizontal ordinate and aerofoil profile lower surface reference mark ordinate, with be respectively the upper bound of leading edge, trailing edge, aerofoil profile upper surface reference mark horizontal ordinate, aerofoil profile upper surface reference mark ordinate, aerofoil profile lower surface reference mark horizontal ordinate and aerofoil profile lower surface reference mark ordinate.M and n is respectively the quantity at the upper and lower Curve of wing reference mark of hydrofoil.The reference mark design domain 7 at the reference mark 6 on hydrofoil 1 Curve of wing 2 is abscissa zone, aerofoil profile upper surface reference mark 6 interval with ordinate or abscissa zone, aerofoil profile lower surface reference mark 6 interval with ordinate the rectangular extent surrounded, reference mark 6 just changes within the scope of this, and solves optimal value.

Objective function f (x) can be any combination of hydrodynamic performance and pressure coefficient, can select flexibly as required in actual Airfoil Design.Optional objective function pattern has several as follows:

1)f(x)＝w ₁C _L+w ₂C _L/C _D+w ₃C _D+w ₄C _pmax

Wherein w _i(i=1...4) be the weight of lift coefficient, lift-drag ratio, resistance coefficient and maximum pressure coefficient respectively, and meet with 0≤w _i≤ 1 (i=1,2,3), can need to select flexibly according to design in actual Airfoil Design.

2)f(x)＝(w ₁C _L+w ₂C _L/C _D+w ₃C _D)C _pmax

This objective function is the long-pending of aerofoil profile hydrodynamic performance and pressure coefficient, wherein w _i(i=1...3) be the weight of lift coefficient, lift-drag ratio and resistance coefficient respectively, and meet with 0≤w _i≤ 1 (i=1,2,3), can need to select flexibly according to design in actual Airfoil Design.

Concrete objective function does not limit above three kinds of patterns yet, can select flexibly according to the needs in actual marine site.And lift coefficient, resistance coefficient, lift-drag ratio and pressure coefficient can be single any situations of attack, it also can be composite function g (x) of each hydrodynamic force coefficient and pressure coefficient function under the multiple situations of attack be shown below.

$g\left(x\right)=g(f{\left(x\right)}_{{\mathrm{\α}}_1},f{\left(x\right)}_{{\mathrm{\α}}_2},...,f{\left(x\right)}_{{\mathrm{\α}}_v})$

Wherein, α _ufor hydrofoil angle of attack size, for angle of attack size is α _uhydrodynamic performance objective function in situation, v is the angle of attack number selected in objective function, composite function g (x) can consider arbitrarily hydrodynamic performance parameter under a situations of attack, and the array mode of any pattern can be taked, preferably can take the weighted sum method be shown below.

$g\left(x\right)=\underset{u=1}{\overset{v}{\mathrm{\Σ}}}{\mathrm{\ω}}_{u}f{\left(x\right)}_{{\mathrm{\α}}_u}$

Wherein ω _ufor weight coefficient, and meet

Second step, determines the computing method of hydrodynamic force coefficient and pressure coefficient and the fitness function of genetic algorithm.

After establishing Optimized model, next optimal design is adopted to set up model.In order to the hydrodynamic performance of accurate evaluation hydrofoil 1, adopt FLUENT or CFX or XFOIL numerical simulation program computation lift coefficient, resistance coefficient, lift-drag ratio and pressure distribution.Which kind of numerical computation method concrete can need to select flexibly according to design.In order to obtain hydrofoil 1 Curve of wing 2 of performance the best, adopt the genetic algorithm with ability of searching optimum, carry out in process in genetic algorithm, the fitness function assessing each design proposal has material impact to optimum results and calculation procedure.

Fitness function is the key factor of assessment hydrofoil 1 aerofoil profile hydrodynamics, relates to searching process, retains the high solution of fitness, eliminate the solution of fitness difference in optimizing process according to fitness function.The present invention adopts the fitness function be shown below.

$h\left(s\right)=\frac{f\left(x_s\right)}{\underset{s=1}{\overset{\mathrm{ss}}{\mathrm{\Σ}}}f\left(x_s\right)}$

Wherein h (s) is the fitness of s design proposal, and ss is the design proposal quantity in population, f (x _s) be the objective function of s design proposal.

3rd step, generates initial population, and matching hydrofoil 1 Curve of wing 2.

According to design variable and bound thereof, a random ss preliminary design scheme (ss is more than or equal to 10), this group preliminary design scheme is initial population.This group preliminary design scheme is generated and fits to hydrofoil 1 Curve of wing 2.In order to can accurate description aerofoil profile, and too much can not sacrifice geological information again, choosing of matched curve is most important, and polynomial spline curve significantly can reduce the number of design variable.Mainly cubic spline curve is have employed in the present invention, be different from general cubic spline interpolation method, the present invention proposes the horizontal ordinate at reference mark 6 and ordinate, leading edge and trailing edge tangent line to carry out matching cubic spline curve, thus can be reached through and control leading edge and trailing edge tangent line size and the object of the hydrodynamic performance keeping aerofoil profile good.But in concrete enforcement, do not limit the mode of this matched curve yet, can adopt other any curve-fitting methods yet.In order to expand search volume as far as possible, selection reference mark 6 as much as possible on Curve of wing 2, adopts each horizontal ordinate put and ordinate as design variable, carrys out matching Curve of wing 2 by the tangent line of the point on Curve of wing 2 and leading edge and trailing edge.And then generate hydrofoil 1 Curve of wing 2.

4th step, generates hydrofoil 1 aerofoil profile fluid mass grid model, calculates and export hydrodynamic performance, and exporting the information such as lift, resistance and pressure.

Generated hydrofoil 1 Curve of wing 2 is processed curve in the geometric manipulations softwares such as AUTOCAD or CATIA, generates geometric model.Generated geometric model is imported in the Grid Generation Software such as ICEMCFD or GRIDGEN or GAMBIT, and sets up the grid model of hydrofoil 1 aerofoil profile fluid mass in software.Generated grid file is imported in the fluid dynamics software such as FLUENT or CFX, and calculates corresponding lift, resistance and pressure, and exported, as the foundation of calculating target function.In the present invention in order to improve counting yield, also can adopt XFOIL software, this software only needs geometrical curve information, does not need to carry out complicated geometry CAD information and grid process, therefore, it is possible to greatly improve counting yield.

5th step, according to hydrodynamic force coefficient and pressure coefficient calculating target function, assesses according to fitness function, judges whether convergence, and convergence then terminates to optimize, otherwise generates new population, returns the 3rd step.

Extract result of calculation and calculate the objective function of different designs scheme in population, assess according to the fitness of fitness function to ss different designs scheme, and each design proposal is sorted according to fitness, judge whether convergence according to the fitness of each design proposal in population and iterations.If convergence, then terminate to calculate, using the optimum solution of design proposal the highest for fitness in population as hydrofoil 1 Curve of wing 2.If do not restrain, then need to regenerate new population as follows.

According to the fitness of ss in population different designs scheme, the low design proposal of fitness is eliminated according to certain ratio (5%-20%), then binary number is adopted to encode each design proposal in population, all 2m+2n+2 design variables coding in some design proposals becomes a binary number, and according to the order arrangement of leading edge tangent line, aerofoil profile upper surface curvilinear abscissa and ordinate, aerofoil profile lower surface curvilinear abscissa and ordinate, trailing edge tangent line.The preferably design proposal retained is carried out variation and crossover operation to obtain new explanation according to certain ratio (5%-20%), thus guarantee population quantity ss is constant.The binary number that each design proposal is encoded into is shown below:

P=[leading edge tangent line aerofoil profile upper surface m horizontal ordinate and ordinate aerofoil profile lower surface n horizontal ordinate and ordinate trailing edge tangent line]

Wherein leading edge tangent line, aerofoil profile upper surface curvilinear abscissa and ordinate, aerofoil profile lower surface curvilinear abscissa and ordinate, trailing edge tangent line adopt a binary number representation respectively.Expression is as follows, and first row represents the binary number after conversion, and second row represents the numbering of design variable in the binary number be encoded into, and a total 2m+2n+2 design variable, the 1st is leading edge tangent line x ₀₀, the 2nd to 2m+1 is aerofoil profile upper surface curvilinear abscissa and ordinate, and according to (x ₁₁, y ₁₁) (x ₁₂, y ₁₂) ... (x _1m, y _1m) order arrangement, 2m+2 to 2m+2n+1 is individual is aerofoil profile lower surface curvilinear abscissa and ordinate, and according to (x ₂₁, y ₂₁) (x ₂₂, y ₂₂) ... (x _2m, y _2m) order arrangement, last is trailing edge tangent line x ₀₁.

Design proposal in new population is decoded as decimal number from binary coding, and returns the 3rd step, and ignore the step wherein generating new population.

Embodiment 1:

In order to verify method for designing proposed by the invention, design is optimized to the hydrofoil profile curve in different designs situation.For tidal current energy water turbine, blade along exhibition to diverse location have different designing requirements, near tip location, having compared with the thin airfoil of high lift-drag ratio is preferably select, and in a wider range of angles of attack, must have higher lift coefficient and lift-drag ratio, and resistance coefficient should be little as much as possible.Because root bears larger load, in order to ensure that blade has enough rigidities of structure and intensity, require that root aerofoil profile has larger thickness.In addition, in order to avoid cavitation phenomenon, needs may be caused to select thicker aerofoil profile.In order to avoid the generation of cavitation phenomenon, maximum pressure coefficient should be reduced as far as possible.Therefore in order to the tidal current energy water turbine Airfoil Design method that comprehensive assessment is proposed by the invention, Reynold number is adopted to be 1e6, the lift coefficient of objective function to be the angle of attack be 3 ° of situations, resistance coefficient, lift-drag ratio and pressure coefficient.Upper and lower Curve of wing is respectively got three reference mark, altogether six reference mark, there are horizontal ordinate and ordinate two design variables in each reference mark, and add that the tangent line one of first edge and trailing edge has eight design variables, initial population quantity have selected 10.

Based on Optimized model proposed by the invention and method for solving, finally obtain several different designs and require that Curve of wing in various situation as shown in Figure 5.As seen from the figure, with minimized drag coefficient with when maximizing lift coefficient, Curve of wing is comparatively close, and during maximization lift-drag ratio, maximum gauge is positioned at apart from aerofoil profile leading edge 35% place, and maximum gauge is 8.8% of chord length; In minimized drag coefficient situation, maximum gauge is apart from leading edge 35%, and maximum gauge is 8.3% of chord length.For the hydraulic turbine, because larger lift component is the thrust perpendicular to hydraulic turbine plane, and it is less to revolving force proportion to be converted into turbine shaft.Be different from lift coefficient, the reduction of resistance coefficient can significantly improve hydrodynamic performance, and therefore resistance coefficient has even more important effect in Design of Hydraulic Turbine.Be different from first two aerofoil profile, maximizing lift coefficient and minimizing the aerofoil profile that minimum pressure coefficient obtains then has larger difference.Under maximizing lift coefficient situation, aerofoil profile front portion is thicker, reduces to trailing edge place profile thickness, and maximum gauge is positioned at apart from aerofoil profile leading edge 39% place, and maximum gauge is 11.4% of chord length; And for minimizing minimum sub-atmospheric pressure coefficient, maximum gauge is positioned at apart from aerofoil profile leading edge 52% place, maximum gauge is 8.8% of chord length.

Four kinds of different airfoil profiles surface pressure coefficient under 3 ° of situations of attack as shown in Figure 6, as seen from the figure, pressure distribution during minimum pressure coefficient is the most even, minimum value is positioned at about-0.5, visible minimum pressure coefficient can improve the pressure distribution of airfoil surface greatly, as much as possible can avoid the generation of cavitation phenomenon.Minimized drag coefficient and the aerofoil profile under maximizing lift-drag ratio situation, minimum pressure coefficient is about-1.1, and both are comparatively close.The minimum pressure coefficient peak value maximized in lift coefficient situation is minimum, reaches about-1.5, most possibly more easily can produce Cavitation Problems.

Lift coefficient, resistance coefficient and lift-drag ratio in different designs objective function situation are as Figure 7-9.Similar with aerofoil profile data result, two kinds of aerofoil profiles that minimized drag coefficient and maximization lift-drag ratio obtain have hydrodynamic performance closely.Using negative pressure coefficient as in objective function situation, lift coefficient is significantly smaller than other three kinds of situations, and resistance coefficient is then close with minimized drag coefficient situation.Although maximize lift coefficient there is larger lift coefficient, but resistance coefficient is obviously greater than other aerofoil profiles, although and this aerofoil profile has maximum lift coefficient under 3 ° of situations of attack, but along with the increase of the angle of attack, aerofoil profile when maximizing lift-drag ratio and minimized drag coefficient has greater lift coefficient.Therefore when carrying out Airfoil Design, only can not consider the hydrodynamic performance under a kind of angle of attack, needing to carry out comprehensive Design.

Can be drawn by embodiment, hydraulic turbine hydrofoil profile method for designing proposed by the invention can not only significantly improve lift coefficient, resistance coefficient and lift-drag ratio, maximum pressure coefficient can also be reduced, thus reach and improve hydrodynamic performance and avoid the object of cavitation phenomenon.

The content that above-described embodiment is illustrated should be understood to these embodiments only for being illustrated more clearly in the present invention, and be not used in and limit the scope of the invention, after having read the present invention, the amendment of those skilled in the art to the various equivalent form of value of the present invention has all fallen within the application's claims limited range.

Claims (8)

1. a tidal current energy water turbine vane airfoil profile method for designing, is characterized in that, comprises the following steps:

Step one: according to designing requirement determination design variable and objective function, sets up hydrofoil profile Optimized model;

Wherein,

Objective function:

f(x)＝f(C _L,C _L/C _D,C _D,C _pmax)

Design variable:

x＝(x ₀₀,x ₁₁,y ₁₁,x ₁₂,y ₁₂,...,x _1m,y _1m,x ₂₁,x ₂₁,x ₂₂,y ₂₂,...,x _2n,y _2n,x ₀₁)

Constraint condition:

$x_{00}^L\≤x_{00}\≤x_{00}^U$

$x_{01}^L\≤x_{01}\≤x_{01}^U$

$x_{1i}^L\≤x_{1i}\≤x_{1i}^U,i=1...m$

$x_{2j}^L\≤x_{2j}\≤x_{2j}^U,j=1...n$

$y_{1i}^L\≤y_{1i}\≤y_{1i}^U,i=1...m$

$y_{2j}^L\≤y_{2j}\≤y_{2j}^U,j=1...n$

Wherein, C _l, C _l/ C _d, C _dand C _pmaxbe respectively the lift coefficient under any situations of attack, lift-drag ratio, resistance coefficient and maximum pressure coefficient, be the function of design variable x;

with be respectively the lower bound of leading edge, trailing edge, aerofoil profile upper surface reference mark horizontal ordinate, aerofoil profile upper surface reference mark ordinate, aerofoil profile lower surface reference mark horizontal ordinate and aerofoil profile lower surface reference mark ordinate, with be respectively the upper bound of leading edge, trailing edge, aerofoil profile upper surface reference mark horizontal ordinate, aerofoil profile upper surface reference mark ordinate, aerofoil profile lower surface reference mark horizontal ordinate and aerofoil profile lower surface reference mark ordinate;

M and n is respectively the quantity at the upper and lower Curve of wing reference mark of hydrofoil;

X ₀₀and x ₀₁be respectively hydrofoil profile front and rear edge tangent line, (x _1m, y _1m) and (x _2n, y _2n) be respectively reference mark coordinate on the upper and lower Curve of wing of hydrofoil, x _2nand x _1mfor the horizontal ordinate at the upper and lower Curve of wing reference mark of hydrofoil, and y _1mand y _2nfor the ordinate at the upper and lower Curve of wing reference mark of hydrofoil;

Step 2: determine the computing method of hydrodynamic performance and pressure coefficient and the fitness function of genetic algorithm;

Step 3: generate initial population, and matching hydrofoil profile curve;

Step 4: generate hydrofoil profile fluid mass grid model, calculate and export hydrodynamic performance, and exporting the information such as lift, resistance and pressure;

Step 5: according to hydrodynamic force coefficient and pressure coefficient calculating target function, assesses according to fitness function, judges whether convergence, and convergence then terminates to optimize, otherwise generates new population, returns step 3.

2. a kind of tidal current energy water turbine vane airfoil profile method for designing according to claim 1, it is characterized in that, objective function f (X) adopts following form:

f(x)＝w ₁C _L+w ₂C _L/C _D+w ₃C _D+w ₄C _pmax

Wherein w _i(i=1...4) be the weight of lift coefficient, lift-drag ratio, resistance coefficient and maximum pressure coefficient respectively, and meet with 0≤w _i≤ 1 (i=1,2,3).

3. a kind of tidal current energy water turbine vane airfoil profile method for designing according to claim 1, it is characterized in that, objective function f (X) adopts following form:

f(x)＝(w ₁C _L+w ₂C _L/C _D+w ₃C _D)C _pmax

This objective function is the long-pending of aerofoil profile hydrodynamic performance and pressure coefficient, wherein w _i(i=1...3) be the weight of lift coefficient, lift-drag ratio and resistance coefficient respectively, and meet with 0≤w _i≤ 1 (i=1,2,3).

4. a kind of tidal current energy water turbine vane airfoil profile method for designing according to claim 1, is characterized in that, objective function can adopt composite function g (x) of each hydrodynamic force coefficient and pressure coefficient function under the multiple situations of attack be shown below,

$g\left(x\right)=g(f{\left(x\right)}_{{\mathrm{\α}}_1},f{\left(x\right)}_{{\mathrm{\α}}_2},...,{f\left(x\right)}_{{\mathrm{\α}}_v})$

Wherein, α _ufor hydrofoil angle of attack size, for angle of attack size is α _uhydrodynamic performance objective function in situation, v is the angle of attack number selected in objective function, composite function g (x) can consider arbitrarily hydrodynamic performance parameter under a situations of attack, and the array mode of any pattern can be taked, preferably can take the weighted sum method be shown below:

$g\left(x\right)=\underset{u=1}{\overset{v}{\mathrm{\Σ}}}{\mathrm{\ω}}_{u}f{\left(x\right)}_{{\mathrm{\α}}_u}$

Wherein ω _ufor weight coefficient, and meet

5. a kind of tidal current energy water turbine vane airfoil profile method for designing according to claim 1, is characterized in that, adopts FLUENT or CFX or XFOIL numerical simulation program computation lift coefficient, resistance coefficient, lift-drag ratio and pressure distribution.

6. a kind of tidal current energy water turbine vane airfoil profile method for designing according to claim 1, it is characterized in that, fitness function described in step 2 adopts following form:

$h\left(s\right)=\frac{f\left(x_s\right)}{\underset{s=1}{\overset{\mathrm{ss}}{\mathrm{\Σ}}}f\left(x_s\right)}$

Wherein h (s) is the fitness of s design proposal, and ss is the design proposal quantity in population, f (x _s) be the objective function of s design proposal.

7. a kind of tidal current energy water turbine vane airfoil profile method for designing according to claim 1, is characterized in that, adopts the horizontal ordinate at reference mark on hydrofoil profile curve and ordinate, aerofoil profile leading edge and trailing edge tangent line to carry out matching hydrofoil profile curve in step 3.

8. a kind of tidal current energy water turbine vane airfoil profile method for designing according to claim 1, it is characterized in that, the method generating new population in step 5 is:

According to the fitness of ss in population different designs scheme, the low design proposal of fitness is eliminated according to the ratio of 5%-20%, then binary number is adopted to encode each design proposal in population, all 2m+2n+2 design variables coding in some design proposals becomes a binary number, and according to the order arrangement of first edge tangent line, aerofoil profile upper surface curvilinear abscissa and ordinate, trailing edge tangent line and aerofoil profile lower surface curvilinear abscissa and ordinate; Leading edge tangent line, aerofoil profile upper surface curvilinear abscissa and ordinate, aerofoil profile lower surface curvilinear abscissa and ordinate, trailing edge tangent line adopt a binary number representation respectively.Expression is as follows, and first row represents the binary number after conversion, and second row represents the numbering of design variable in the binary number be encoded into, and a total 2m+2n+2 design variable, the 1st is leading edge tangent line x ₀₀, the 2nd to 2m+1 is aerofoil profile upper surface curvilinear abscissa and ordinate, and according to (x ₁₁, y ₁₁) (x ₁₂, y ₁₂) ... (x _1m, y _1m) order arrangement, 2m+2 to 2m+2n+1 is individual is aerofoil profile lower surface curvilinear abscissa and ordinate, and according to (x ₂₁, y ₂₁) (x ₂₂, y ₂₂) ... (x _2m, y _2m) order arrangement, last is trailing edge tangent line x ₀₁, it is numbered 2m+2n+2 in binary number,

The preferably design proposal retained is carried out variation and crossover operation to obtain new explanation according to the ratio of 5%-20%, thus guarantee population quantity ss is constant.