Researsch On Controlling For Varible-pitch Rule Of Vertical-axis Wind Turbine Devices

Horizontal axis wind turbines (HAWTs) and vertical axis wind turbines (VAWTs) are two main types of wind turbines. With higher efficiency, the former one has been treated as main trend in the present. But there are still some inherent drawbacks which have increased its cost. For example, stress changes on blades of HAWTs are complex, the engine room mounted on the top of the tower is not easy to be maintained, and so on. Compared with HAWT, VAWT has the advantages of easier maintain, lower noise, more stable stress, and so on. But the lower efficiency and no self-starting ability have restricted its development all the time.In this paper, the present status at home and abroad has been summarized. After these, the variable pitch laws of VAWT have been investigated to solve the problems mentioned above. The main research steps are shown below.Firstly, the model of variable pitch VAWT has been built based on Blade Element Theory. And it has been used to analyze the advantages of symmetric blade airfoils. The airfoil of NACA0015 has been simulated numerically in FLUENT to obtain its aerodynamic parameters. Based on this model, the optimum variable pith laws at different tip speed ratios have been calculated in Matlab. After this, the practical switch points between these laws have been determined manually.Afterwards, two types of variable pitch VAWTs based on different pitch laws have been designed. And the instantaneous moments, average moments and efficiencies of both turbines have been calculated by the use of Double Disks Multiple Streamtubes Model. Besides of these, three-dimensional numerical simulation has been done in FLUENT to analyze the force conditions of blades at different azimuth angles.Lastly, the synchronous and optimum variable-pitch VAWT prototypes, including the general structures, power conversion systems, pitch control systems and so on, are designed and manufactured. And the synchronous one has been made experiments to study the aerodynamic load and electrical performance. Just an initial test has been done on the optimum one. The experimental results indicate that the variable-pitch laws have improved the self-starting performance and the system efficiency significantly.