The System Design And Optimization Study On Dish-type Overtopping Wave Energy Convertor

The growing demand for energy has resulted in a dependency on fossil fuels. The price of fossil fuels and security of energy supply has been a concern all over the world; many researchers focus on ocean energy. Wave energy is most abundantly in China, there is a brightly future for its development. The Dish-Type Wave Energy Convertor is a new offshore overtopping wave energy convertor, which has the advantages of high conversion efficiency, excellent adaptability and stability.Primary design of the convertor is given by previous research, it has the ability of gathering the hydraulic head between 1.0m to 2.5m, and maximum overtopping discharge is 8.32m3/s. For the conversion device, low-head turbine is the key component of wave energy technologies; the thesis proposes two types of low-head turbine: the Curved Surface Vane Turbine and the Axial-flow Turbine. The geometric configuration of the above turbines is introduced, and mathematical models of main performance parameters of the blade turbines are set up. According to the gathered hydraulic head and overtopping discharge, the initially design of the above turbines is achieved.Study on low-head turbine involves the complex hydrodynamic mechanism of the coupling between fluid and blade, which is difficult to solve in theory. Thus the research method of combining model test with numerical simulation is proposed. Two turbine test sets are designed, several models are made. Based on the test results, the working performance of Axial-flow turbine is much better than Curved Surface Vane turbine.The thesis establishes numerical models to study more about the turbine, optimization of the Curved Surface Vane turbine is carried out in a 2D numerical model, while capability analysis of Axial-flow turbine (ZDK283-LM-80) is in a 3D numerical model. Computational result shows that the Axial-flow turbine has the ability to output more power, and can be utilized in the Dish-type Overtopping Wave Energy Convertor.Using the ZDK283 turbine, with hydraulic head H=1.5m, overtopping discharge Q=1.57m3/s, the output power can easily reach 6kW, thus primary design of the device is too big, and need to be optimized. The thesis establishes an overtopping-outflow hydraulic numerical model of the wave energy convertor in Fluent. Numerical results of overtopping phenomena and discharge show good agreement with model test results, therefore, the hydraulic numerical model can be applied to optimize parameters of the device.According to computation of various scale numerical model, device parameters such as whole diameter R, sloping ratio m, outflow pipe diameter d, and its length hd are all optimized. Computational analysis finds that the taper outflow surface is better than column surface, thus taper outflow surface is employed in the device. The wave energy convertor is steadily moored to the bottom of the sea by six tension leg-anchor chains.After optimization of the Overtopping System, the Outflow System, the Low-head Hydropower System and the Mooring System, the whole assemblage of Dish-type Overtopping Wave Energy Convertor is given out.