Research And Experimental Investigation On Mooring Tidal Current Energy Conversion System With Double Ducted Turbines

With the increasing depletion of fossil energy, marine renewable energy hasbecome the focus of the world’s attention gradually. Nowadays China also activelysupports research and experiments on ocean energy devices. Within this framework,various marine energy development and utilization devices emerge endlessly. Thisdissertation is supported by one of projects, Mooring Tidal Current Energy ConversionSystem with Double Ducted Turbines, to develop a suitable ducted turbine for thefloating system.First, this paper investigates appropriate methodologies and approaches to simulatethe hydrodynamic performance of bare tidal current turbines based on ComputationalFluid Dynamics (CFD). Both numerical and experimental investigations have beencarried out for two different turbines respectively based on S814airfoil and BDAbidirectional airfoil. According to the comparison, CFX can accurately predict thehydrodynamic performance of tidal stream turbines, except in the circumstances thatlarge vortex separation around the blade is generated.Second, the influence on the fluid velocity field caused by the duct are analyzedand discussed. The researches and simulations are undertaken in those aspects, whichare the different mechanisms of nozzles and diffusers, the influences on the throatvelocity caused by different geometry features and the interactions between the diffuserand the turbine. The CFD result indicates that the diffuser with less thickness has thebetter acceleration effect.To obtain an optimum shroud design that has higher throat velocity, lower drag andsmaller size, the combination use of ANSYS-Workbench and ANSYS-CFX cansignificantly reduce the computational cost during the process. Then the hydrokineticperformance of the designed shrouded turbine simulated by actuator disk theory isCp=0.82. On the other hand, another simulation under the experimental conditionsatshhneog wlceos).ntfhidate nlacreg eto e dthdei eps readnidc tteudr bruelseunlctse sw bheihchin dc otmhep ututer btihnee hairgeh pesrot dCupc=ed0.6a5n(d+l5o°w tewriesdtTests are conducted in water circulating channel to measure the power coefficientsand the drag coefficients with the generator to measure the generated power and the dynamometer to measure the drag. Results show that when+5°twist angle turbineblades are in TSR=6.6ducted turbine has higher power coefficient (Cp=0.74) andlower drag coefficient (CT/10=0.265).