Study On Hydrodynamic Performances Of A Tidal Current Energy Conversion Device With Flexible Blade Turbine

As renewable energy, the tidal current is becoming one of the research focuses at home and aboard. The resource of tidal current energy in china is rich, so its development potentiality is promising. As the conversion device, turbine is the key component of tidal current energy technologies. Ongoing research is focused on its structure, power mechanisms, and performance optimization.The author developed an innovative type of fluid energy extracting device—flexible blade turbine, borrowing ideas from impelling mechanism of sailing, the coupling effect of the flexible sail and the aerodynamic characteristics of wing. Using flexible materials as blade which can take good advantage of fluid dynamic, it can adjust attack angle automatically, taking full use of the lift and drag effect generated by the coupling with fluid. Thereby, it has an excellent hydrodynamic performance that the rigid blades do not have.This paper puts forward the geometric configuration of the flexible blade and the structural of flexible blade turbine; analyzes the shapes of flexible blade and forces acting on it in rotation; studies the principle and performance characteristics of the flexible blade turbine preliminarily; sets up the mathematical models of the main performance parameter of the flexible blade turbine; finds the main factors effecting the performance of the flexible blade turbine via dimensional analysis.The study on flexible blade turbine involves in the complex hydrodynamic mechanism of the coupling between fluid and flexible blade, which is a difficult problem unsolved at present. So the research method of combining water tank model test with numerical simulation is proposed.The author designed a water tank model test system and the testing means of hydrodynamic performances of flexible blade turbine. Several models with different blade shapes, blade fixed methods, rotor structures and installation are designed. Then water tank testing was carried out. Based on the analysis of results, the hydrodynamic performances of flexible blade turbine and their influence factors are researched plenty. Then the structures of flexible blade turbine are selected and optimized preliminarily.With the development of CFD, it's becoming possible to solve the problem of the coupling between the flexible blade and fluid so as to predict its hydrodynamic performances using numerical simulation. By considering knowledge from related research field such as flexible wings, parachute inflation process and fluid-solid coupling of heart valves, the author proposed the way to solve the problem of the coupling between flexible blade and fluid using numerical simulation in CFD. First of all, the fluid-solid coupling equations are founded. The shape of flexible blade will be acquired using fluid-solid coupling analysis. Then the physical models of flexible blade at different positions are created. In the process of simulation, dynamic mesh technology is adopted. And the rotational speed of rotor is defined via user-defined functions. The numerical simulation and performances prediction of flexible blade turbine are implemented finally.Under the research method of combination of water tank model test and CFD numerical simulation, the hydrodynamic performances of flexible blade turbine are studied and certificated. The main factors that affect its hydrodynamic performances are analyzed. Then its structures, performance parameters are optimized. Based on this, the 5kW flexible blade turbine is developed for the sea trial. The results of two times sea trials prove its predominant hydrodynamic performances, and an excellent agreement was found between sea trials and water tank model test & numerical simulation results.