||This thesis investigates a horizontal water turbine blade designed to suit the periodical ocean current in Penghu sea region. Blade element momentum theory is exploited to design blade profiles. Then, CFD software, Fluent, is used to obtain such simulation result for torque, power, and efficiency. Firstly, performance of turbines with various cross-sectional profiles is discussed. Then, we use quasi-steady method to simulate power output of turbines from periodical ocean current and estimate how much ocean current energy we can obtain per day. Further, the performance of a turbine installed for different immersed depth from the surface is investigated.|
Our studies show that airfoil profile NACA6409 can outperform others in terms of high lift/drag ratio under low Reynolds number, and better hydrodynamic properties help the water turbine obtain higher torque and power output. A water turbine designed by using NACA6409, at R=1 m, at uniform velocity=2 m/s is estimated to generate 5KW output power. On condition of periodical current flow, the ebb tidal current can rotate water turbine, but power output is only 0.54 times of flood tidal current. The water turbine can generate more power when it is sited in deeper water, and less torque when it is sited near the water surface.