Experimental Study On Hydrodynamic Performances Of Flexible Blade Turbine Driven By Tidal Energy

Currently, the blades of turbines extracting energy from tidal current are rigid. Rigid blades have many weaknesses. For example, rigid blades can only work in high speed flowing conditions; it causes great noise, and it has serious cavitation. What's worse, the sharp edges of rigid blades can hurt the fish and other marine organisms. All above weaknesses are the primary factors that impact the development of tidal energy technologies. The flexible blade turbine is a new type of tidal energy conversion device. Its blades are made of flexible material. The flexible blades are characteristic with strong self-starting ability, working at low rotational speed, not serious cavitation. What's more, the flexible blades have the characteristic of project development: its rotational direction depends on the installation of flexible blades rather than the direction of fluid. Therefore, the flexible blade turbine can be used in the flow of changing direction.The flexible blade transforms adaptively to the fluid, so it has the shape of airfoil. The lift and drag forces act on the flexible blade. When one reduces, the other will increase. However, they are both the powers driving the turbine, so it extracts tidal energy efficiently.Firstly, taking the sail-winged flexible blade turbine with 4 blades as an example, this paper introduces the principle of flexible blade turbine, analyzes the forces acting on the blades, creates the mathematical models evaluating its hydrodynamic performances, and discusses many factors in equation. Then, the paper explains the common problems in the research of coupling between fluid and flexible materials. Thereby, the research method in the paper is mainly based on the experimental analysis.Under the guidance of dimensional analysis theory, the author works out a series of dimensionless parameters relative to the blade shape and rotor structure. These parameters directly affect power efficiency coefficient. Corresponding to these parameters, several turbine rotor models are designed. Then a reasonable experimental program is proposed. After that, the data obtained in experiment are analyzed. Thus, the law how these parameters affect the dynamic performances of flexible blade turbine is found. Then the hydrodynamic characteristics are demonstrated, and the optimization program is proposed according to structural parameters and turbine installation.Subsequently, the structures of the 5kW flexible blade turbine are discussed, and double floating-bodies lifting structure is adopted. And the first prototype of 5kW flexible blade turbine is created in China. According to special marine environment, the material of flexible blade is selected, and the blade shape and rotor structure are checked and optimized. At the same time, the carrier is designed and electric control system of prototype is introduced.Finally, the congregate effect of the duct is analyzed, and TSR is studied based on the datas of sea trial. Then the results of sea trial are compared with that of practical model test. Although there is a little gap, the trends suit each other well. The control schemes of working status at different flowing speeds are proposed. And ideas for the engineering application are provided.