Performance Analysis Of Vertical-axis Tidal Current Turbines And Optimizing Turbines Array

Energy crisis and environment pollution push people to look for clear and renewable energy for replacing fossil fuel. As an alternative solution, ocean energy attracts more and more attention from the world. China has a long coastline which means rich tidal energy, one of some main ocean energy types. Vertical-axis tidal turbine is a device that can turn tidal energy into electric energy. Owning many advantages, it will be the most promising energy converting means in the foreseeable future.Both theory method and experiment method are major ways to research vertical-axis tidal turbines. With the development of computer technology and theory of computational fluid dynamics (CFD), CFD method becomes an important investigating tool of researchers. CFD method has been used to develop turbomachinery for years, but it is still fresh in studying tidal turbines. This thesis focuses on researching the performance of vertical-axis tidal turbines and optimizing turbines array with the CFD method.Firstly, the research progress is reviewed to conclude the research development of tidal turbine followed with some basic CFD theories. A classic experiment is simulated with CFD method to evaluate the influence of different parameters setting. By comparing simulation results and experiment data, an optimal choice is presented. Secondly, a3D-CFD model is used to investigate the performance of turbines instead of the generally used2D-CFD model. As expected,3D-CFD method result is more accurate than other methods. By changing the tip speed ratio (TSR) and solidity, it implicates that there is always a best TSR and solidity for a certain configured vertical-turbine to maximize its output. Like wind farms, large numbers of turbines can be arranged in the sea to generate electricity economically. For this reason, different array patterns are proposed and compared to assess their output and wake. Analysis results show that the average output of all turbines in an optimized array is much larger than an isolate turbine owning to a synergistic effect. It also shows rotation direction is not an important factor to influence turbine output. In the end, an optimized model is suggested to build a first-generation commercial turbine farm.