| With the development of economy, the human demand for energy is growing year byyear. Ocean energy is a renewable clean energy, many countries focuses on developing it.Tidal turbine is the most common form developing tidal current energy. Vertical axis tidalcurrent turbine has simple structure, high reliability, and don’t subject to the direction of flow.But the energy efficiency of the Vertical axis tidal current turbine is low, which restricts itsdevelopment and promotion. Variable pitch vertical axis tidal turbine has higher energyefficiency than fixed pitch turbine. The main work of this paper is to find a way to control themotion of the blade, which can improve the energy efficiency of the vertical axis turbine.First, genetic algorithm is used to optimize blade motion of vertical axis turbine,choosing Single Disk Multiple Stream-Tube Model as the calculation method of theindividual fitness, maximum efficiency as the optimization objective. Base on the result andrealizability in practice, we find a data processing method to deal with the optimization data.At last we get the blade motion formula.CFD is used to verify the blade motion law we get above. Two-dimensional mesh is usedin many vertical axis turbines numerical simulation, the results show the energy efficiency ofvertical axis turbine become higher significantly after optimization, and verify effectivenessof the blade motion law and the blade motion formula.In this thesis, a research is made on the three-dimensional effect of vertical axis turbinein numerical simulation. Three-dimensional effect reduces the energy efficiency of thevertical axis turbine, when the tip-speed ratio is high, and this effect decreases with the bladeaspect ratio increases. Installation of baffle structure at the end of the blade can reduce theinfluence of three-dimensional effect. When the tip-speed ratio is low, energy efficiency inthree-dimensional is higher than two-dimensional. |
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