Research On The Characteristics Of Low Wind Speed Startup Vertical Axis Wind Turbine

Wind energy, which is a renewable energy, has been attached importance by many countries in the world from the mid-1980s.During recent twenty years, wind power has the ability to compete with the power of coal or nuclear.Horizontal axis wind turbine propeller is the most popular wind turbine at home and abroad, but due to low wind speed start, convenient installation and maintenance, wind resistant ability strong and so on characteristics of vertical axis wind turbine, it is gradually attached more and more importance.By comparison of many commercial vertical axis wind turbines at home and abroad, it's discovered that the prototype of the turbines is Savonieus rotor or Lafond turbine. After the previous and current research activities of above two turbines are compared, the Lafond turbine, which is suitable for working under the low speed condition, is selected for the study. The design of improved Lafond turbine is based on research findings of the improved Savonieus rotor from Shanghai University researchers and structural patterns of commercial vertical axis wind turbines at home and abroad.In the dissertation, research focuses on low wind speed startup vertical axis wind turbine, whinch is suitable for low wind speed areas.An numerical and experimental research on the turbine wind generator and its guide vane-wind shield is presented in the dissertation. The flow fields of the wind turbines with guide vane-wind shield and without them are numerically simulated with application of the CFD software FLUENT.The simulation is performed in two dimentional unsteady implict SIMPLE algorithm, the governing equations are discreted in second-order upwind schemes and the Spalart-Allmaras turbulence model is used.Analyzing the flow field characteristics of wind turbines with guide vane-wind shield, it is explained the reasons of the great improvement of wind power coefficient of wind turbine with guide vane-wind shield. The structural parameters of wind terbine include the shape of rotor blades, the number of rotor blades, the size of the rotor diameter, the number of guide vane-wind shield, and the installation angle of guide vane-wind shield and so on. If the structural parameters of wind terbine are different, the structural patterns are different correspondingly. In order to make sure the optimum relation of structural parameters, the means of orthogonal optimization should be adopted. After the optimization, the wind energy utilization ratio of wind turbines with guide vane-wind shield has remarkably increased.The straight-flow low speed wind tunnel is constructed for wind tunnel test in order to confirm the results of the means of orthogonal optimization. In the wind tunnel experiment, the models of Lafond turbines and guide vane-wind shields under different structural factors have been made. The capability of both different shapes of wind turbines and guide vane-wind shield are tested with the help of testing instruments, such as revolution meter, ventometer, frequency converters and so on. According to experimental results, the performance the improved Lafond turbine and guide vane-wind shield is superior to the prototypes. The Lafond turbine with guide vane-wind shield can reduce start speed, increase rotating speed, and increase output torque. The overall performance of the new turbine can be improved significantly, and the availability of the digital simulation results is validated.