Study On Integrated Aerodynamic Shape And Structure Design Theory For Wind Turbine Blade Based On Airfoil Library

With the decreasing of fossil fuel reserves, energy crisis scare has become more and more serious. As a clean source of renewable energy, the wind energy has been arousing more and more attention in the world. The wind turbine blades whose costs account for 20 percent of the total cost of the wind turbine are one of the most important components. And its performance will directly affect the conversion efficiency of wind energy. Thus, it is worth analyzing the performance of the turbine blades accurately and designing a novel efficient wind turbine rotor on theory and in industrial applications.This research is supported by the grant from the National Natural Science Foundation of China(No.51175526) and the National High Technology Research and Development program of China(863 Program, No.2012AA051301).In this paper, a research topic, study on integrated aerodynamic shape and structure design theory for wind turbine blade based on airfoil library, is proposed. By analyzing the domestic and international method of designing wind turbine airfoils, a novel representation method which combines the functional integral theory of wind turbine airfoils and spline curves is proposed. Then, the effects of airfoil profile on aerodynamic and structural performance are considered in design phase. And airfoils which have well aerodynamic and structural performance are obtained. The effects of aeroelasticity on wind capture capability have been researched deeply, and experimental verification has been conducted. Based on the study mentioned above, an integrated aerodynamic shape and structure design method for wind turbine blade based on airfoil library has been proposed by carefully considering the interactions between the turbine airfoils, blade aerodynamic shape and structure. The main study and achievements are as follows:① In the reaserch process of wind turbine airfoils, a novel representation method which combines Theodorsen theory and B-spine curve is proposed. And a new concept, airfoil structural performance, is introduced. Based on the study mentioned above, an integrated aerodynamic and structural design method for wind turbine airfoil has been proposed, in the new method, the best aerodynamic and structural performance are the optimization goal, and the improved genetic algorithm is optimization method. The optimization is accomplished and new airfoils named CQU-L with different maximum relative thickness have been designed. The original airfoil library is composed of the new airfoils, which have well aerodynamic and structural performance.② A novel aerodynamic model is established considering the influence of aeroelasticity. In this new model, the torsion deformation of blade is introduced. And then based on this model, a novel fluid-solid coupling approach capable of predicting the performance of wind turbine blades with aeroelastic effect is presented. In this method, the load of blade is decoupled into load function and applied on blade. Finally the performance analysis in a variety of wind speed conditions is done by using this approach. The result shows that the load exerted on wind turbine roter increases along with the wind speed. And elastic deformation of blade also increases. As a result, the obvious change of the blade shape influences the practical performance of wind turbine roter. Although aeroelasticity has a little effect on maximum power coefficient, yet it causes obvious negative effect on performance of wind turbines in high wind speed and big load conditions which reduces the absorption of wind energy.③ A new 1kW wind turbine blade shape is designed by the existing design method for wind turbine blade shape. The composite blade is manufactured by FRP molding technology. Then the roter assembly is finished. According to GB/T18451.2-2012 standards, the test platform is established by using a car as the carrier. After that, the test for performace of the 1k W wind turbine is fineshed. It is proven that the method for wind turbine blades analysis with aeroelastic effect is correct by comparing the tese results with theory analysis result.④A novel aerodynamic model is established, considering the influence of the strength failure analysis theory. In this model, a new quantity, twisting angle of loaded blade, is introduced. The optimization model which maximizes the power at the rate speed is proposed for the pitch regulation wind turbine. The chord length and twist angle are the design variables, then the mathematical optimization model considering aeroelasticity for the 850 kW wind turbine blade is established. Lastly, the wind turbine blade is designed by using genetic algorithm. Compared the reference blade, the optimization results show that the maximum power coefficient of the optimized blade has been improved, and the output power of the optimized blade has increased at most 23 kW while the mass has been reduced. The study of the new designed blade provides a theoretical basis for the designing high performance, light quality and low-cost wind turbine blade.⑤Based on the parametric expression of airfoil, blade chord and twist distribution and the layout for the structure of the composite wind turbine blade, a complete finite element parametric model for the blade is established. It is validated that parameterized model established in this paper can simulate accurately the real structure of wind turbine blade by comparing the mass and dynamic characteristics of the established finite element parametric model and the real blade. Moreover, the double-objective optimization model with maximum the output power and minimum the blade mass is proposed considering the interactions of airfoil profile, blade chord and twist distribution and layout of composite blade in design phase. Then the optimization mathematical model for a new 3MW wind turbine blade is established. This study shows that the performance of the new designed blade has been improved and its mass is reduced within the strength requirement. This study has important theoretical guiding significance for design of airfoil and blade structure of wind turbine.