Researsh On Aerodynamic Performaceand Rotor Configuration Of Large-scale Straight-blade Vertical Axis Wind Turbine

The vertical axis wind turbine(VAWT) is an important product type of wind turbine market, however, because of long term insufficiency in investment and research after its appearance, so the relevant technology is not mature and its application is almost concentrated on small and medium-sized products. Studies show that the vertical axis wind turbine has similar ability of utilizing wind energy to horizontal axis wind turbine, and it also has other advantages like no yaw mechanism, simple blade structure as well as low fatigue load and so on, therefore it is recommended to develop large-scale products. Although many countries around the world have explored and investigated large-scale VAWT, multi-megawatt straight-blade vertical axis wind turbines are so far in design, whose theory is still needed to be enhanced. Based on analysis above, this paper will firstly establish suitable mathematical model for VAWT and improve the method of CFD simulation, then the aerodynamic and structural analysis for the rotor of wind turbine will be researched with both mathematical model and CFD simulation. The results can guide the further design of large-scale VAWT.Based on the double-multiple stream tube model for Darrieus VAWT, this paper has established a mathematical model which can be used to analyze straight-blade VAWT. By interpolating the lift coefficient and drag coefficient under high Reynolds number and computing power coefficient, this paper has analyzed the impact of tip ratio, rotation radius and solidity on wind turbine’s aerodynamic performance. As the large-scale wind turbine in wild environment will encounter wind shear, therefore the influence of this factor will be discussed as well.As the aerodynamic performance of VAWT cannot be described simply by mathematical model, this paper has also adopted the 2D-CFD simulation technology. According to the time-consuming characteristics of CFD method, this paper firstly studies the equilibrium problem of accuracy and efficiency, especially focus on the impact of turbulence model, grid number and time step on the computing results, and put forward a parameter setting strategy to improve simulation efficiency. Comparing the results of both mathematical model and CFD simulation to existed experimental data in the literature, this paper has analyzed the feasibility and limitation of two research method.Large-scale wind turbine should choose low solidity rotor. Based on CFD simulation, fixing the magnitude of rotational radius and solidity, this paper analyze the impact of different combination of blade number and chord on the aerodynamic performance of wind turbine from aspects of power coefficient, torque efficient and airfoil vortices respectively. The result shows that wind turbine decrease the degree of torque fluctuation without increasing solidity. Based on analysis of airfoil and installation angle of blade, this paper finally chooses parameters of the rotor.In order to reduce the fatigue load and extend life time of main shaft of turbine, after having discussed various layout of VAWT, this paper finally chooses multi-layer interlaced layout scheme of turbine, then designs and checks the specific structure of blade beam, supporting arm and supporting shaft. To prevent resonance of rotor when rotating at rated speed, modal analysis is carried out at last.