Theoretical Study On The Controlled Law Of Blade Deflection Angle Of Tidal Current Turbine

Power coefficient is one of the most important parameters of vertical-axis tidal current turbine for ocean energy conversion. It has close correlation with the law of blade deflection angle. Therefore, seeking optimal deflection angle has become a critical problem for the design of turbine and the control of deflection angle. An optimization mathematic model for changing deflection angle of the vertical-axis turbine to enhance the turbine's power coefficient was presented in the thesis. In this model, the revolving orientation method was chosen to optimize the law of deflection angle and the stream tube method was applied to calculating the hydrodynamic performance of the turbine.Firstly, formula of stream tube method was summarized including single disk multi-tube model and double disk multi-tube model. Then the modification of the blade rotating effect was extended to arbitrary deflection angle.Secondly, mathematic model of optimization on the law of deflection angle was presented and Hicks-Henne function was introduced to optimize. This model was validated by comparing with other method's numerical results. According to lots of calculation results, the method how to select parameters in optimization process was determined.At last, the reason why power coefficient improved was discussed by analyzing the instantaneous power coefficient, hydrodynamic angle of attack and deflection angle and so on. Optimization results which were calculated by different objective function and different discrete format of design variables were analyzed. The optimization effect and difficult degree of engineering implementation were discussed.