| Nowadays, more and more countries have paid attention to the wind energybecause of its advantage of as a clean source of renewable energy. With the emphasison wind power, the wind turbine has been in recent years applied and developed wildly.The wind turbine blades are one of the most important components which take about20%of the whole wind turbine value. Moreover, the determinants for normal andstable operation are good design, reliable quality and superior performance.This work is supported by a grant from the National High Technology Researchand Development program of China (863Program, No.2012AA051301) and NationalNatural Science Foundation of China (No.51175526). Therefore, in this paper, theresearch topic is presented named the study on the parametrized coupled design theoryof wind turbine blade aerodynamic shape and structure. On the basis of the analysis ofdomestic and international wind turbine airfoils, blades shape, blade structure andaeroelastic theoretical methods, the functional integral theory of wind turbine airfoils isstudied. Based on curvature smooth continuity theory, a new method for improvingairfoils is presented. For the medium thickness airfoils, a novel method of airfoilparameterization which combined the airfoil integrated theory and B-spline theory ispresented. Then, using improved particle swarm algorithm and considering fully therequirements of the aerodynamic performance of the wind turbine airfoils and blades,we have designed seven standard airfoils with high aerodynamic performance (therelative thickness of the airfoils is from15%to40%). Then, based on the amendatorywind turbine aerodynamic theory, the shape of wind turbine blade along the span-wisedistribution is designed used CQU-A airfoil series within the region of wholegenerated power for the wind turbine. The multi-objective optimization model with themaximum the power coefficient and smallest blade area is proposed for the pitchregulation wind turbine. The wind turbine blade is designed by using an improvedmulti-objective particle swarm optimization. The results show that the blades exhibithigh performance and light mass. Lastly, the airfoils data, the new blade shapeparameters and the composite blade structure argument are integrated into the variableparametric analytical expression. The parameterized finite element model of thecomposite wind turbine blade is established. The structure of the wind turbine bladeunder the aerodynamic loads is optimized using PSO algorithm. The optimized results indicate that the mass of the blade is reduced. As a result, the new design method forairfoil, blade shape and blade structure is formed. More importantly, it will make thecoupled wind turbine blade shape and elastic deformation possible. The main studyand achievements are as follows:1) The effects of the airfoil geometric and aerodynamic parameter to the airfoilaerodynamic performance are discussed. The calculated method for the airfoilaerodynamic performance is studied. For three different thickness of wind turbineairfoils (WT180airfoil, DU93-W-210airfoil and DU91-W2-250airfoil), the resultsfrom RFOIL software and the results from experiments are analyzed comparativelyanalysis. The study indicates that the RFOIL software can predict the aerodynamicperformance of the wind turbine airfoils. This means that it is suitable for the directdesign method of the airfoils, as well as providing the effective computing tools for theaerodynamic performance of the new airfoil family design.2) In order to optimize wind turbine airfoil series with better aerodynamicperformance, an improved particle swarm algorithm is presented. Firstly, somecommon optimal algorithm used for airfoils are introduced. Then, the standard PSO isintroduced. The advantage and disadvantage between the PSO and other algorithms arecompared in detail. So as to overcome the lack of easily getting local best solution atthe time of the initial optimization, an improved PSO that the inertia weight is the formof inverse hyperbolic cosine function with nonlinear is presented. At the same time,some typical examples are analyzed using this improved PSO. The optimal resultsindicated that the improved PSO is better than the standard PSO whether the bestsolution or the stability. It is validated that the improved PSO has the effectiveness andfeasibility. The study of the improved PSO can provide the foundation of algorithmwhen optimizing the wind turbine airfoils.3) Based on curvature smooth continuity theory, a new method of improvingairfoils is presented. Comparatively, the aerodynamic performances of the new airfoilsuch as maximum lift coefficient, maximum lift-drag ratio, roughness insensitivity andso forth are better than the DU93-W-210airfoil performances. For the wind turbineairfoils with different relative thickness, the optimal design of wind turbine airfoils isstudied by using distinct methods to get airfoil profiles. For the thin thickness airfoils,based on the theory of functional integral design, a method that makes the appropriatenumbers of control variables in order to better controlling airfoil profiles is presented.Considering synthetically the airfoil leading edge roughness sensitivity, off-design condition, stall condition and noise, the thin thickness airfoils are optimized by usingthe improved PSO method coupled the RFOIL software that the aerodynamicperformance can be calculated.3kinds of different thin thickness airfoils namedCQU-A150, CQU-A180, and CQU-A210respectively are designed. For the mediumand thick thickness airfoils, a novel method combined the airfoil integral theory andB-spline is presented. Considering mainly the structural compatibility and theaerodynamic performance, four airfoils with medium or thick relative thickness aredesigned by using the improved PSO method. The names of the four airfoils areCQU-A250, CQU-A300, CQU-A350, CQU-A350and CQU-A400respectively. Theaerodynamic performances of the seven airfoils are analyzed in detail. The new airfoilsshow high aerodynamic characteristics. Compared with the commonly used windturbine airfoils, the new airfoils show the higher lift coefficient and larger lift/dragratio in both smooth condition and rough condition at the main angle of attacks. Theperformances of the new airfoils show a significant improvement compared with thetypical airfoils. In a word, the functional integral design theory is consummated in thisstudy of this chapter, and not only broadening the idea of the wind turbine airfoildesign, but also making a good foundation for designing wind turbine blades.4) Based on the wind turbine aerodynamic theory, the effects of the keyparameters (such as tip speed ratio, wind diameter, Reynolds, blade root loads and soon) to the performance of the wind turbine are analyzed in detail. Then, the shape ofthe wind turbine blade along the span-wise distribution is designed used the newlyCQU-A airfoil series within the region of whole generated power for the wind turbine.The multi-objective optimization model with maximum the power coefficient andsmallest blade area is proposed for the pitch regulation wind turbine. Then themathematical model of design and optimization for a new2MW wind turbine blade isestablished. Lastly, the wind turbine blade is designed by using an improvedmulti-objective particle swarm optimization. The optimization results show that,compared the original2MW wind turbine blade and Tjaere2MW test blade, theperformance of the new designed blade have been improved, and the area issignificantly smaller which means that the mass is reduced greatly and also reduced thematerial cost of the blade. Moreover, the load for the blade root is effectivelycontrolled. The study of the new designed blade provides a theoretical basis for thedesigning high performance, light quality and low-cost wind turbine blade.5) Based on elasticity of the composite wind blade and the equivalent design method which is often used in composite structural design, the initial layout design forthe structure of the composite wind turbine blade is determined. The finite elementparametric model for the blade is established. Based on the modified Blade ElementMomentum theory, a new one-way fluid-structure interaction method is introduced. Aprocedure combining finite element analysis and particle swarm algorithm to optimizecomposite structures of the wind turbine blade is developed. The procedure proposednot only allows thickness variation but also permits the spar cap location variation overthe structure. The results show that, compared to the initial blade, the mass of theoptimized blades is reduced and especially for the scheme Ⅱ (the location of bladespar cap is seen as one of the variables) which exhibit more mass saving. Finally, thestrain of the optimal blade is analyzed, and the location of the max strain of the optimalblade is pointed out. This present study has important significance for the structuraldesign and optimization of wind turbine blades. Moreover, the highly coupledaero-elastic problem of the structure and aerodynamic models can be solved.6) The static aeroelastic basic functions suitable for the two dimensional (2D)airfoil sections of wind turbine blades were derived based on the aeroelasticity theorywithin the linear elastic range. Through taking the attack angle as input, pressure asoutput and the elastic twist angle of the airfoils as the feedback of the system, anaeroelastic feedback model for the elastic airfoils of wind turbine blades wereestablished. Finally, the influence of different airfoils (including the new airfoildesigned by author) on the additional twist angle of the2D airfoil sections and the liftforce distribution of wind turbine blades was mainly studied. The study showed thatthe aerodynamic performance of the airfoils improved with the increased additionaltwist angle when the torsion stiffness is small, and the aerodynamic performance of theairfoils had litter changed with litter increased additional twist angle when the torsionstiffness is large. Meanwhile, the study also indicated that the static aeroelasticcharacteristics of the new airfoil designed by author are reasonable. The considerationof the elastic deformation of blades has important theoretical guiding significance forstudying the aeroelastic problems of large wind turbine blades. |
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