Numerical Simulation Of Hydrodynamic Performance Of Vertical Axis Tidal Turbine And Duct

Ocean contains enormous amount of energy which has been not developed sufficiently. As it is reliable and cleaning, tidal current power generation is one of promising research field. There are two kinds of tidal turbines, horizontal axis turbine and vertical axis turbine. Though vertical axis tidal turbine holds the advantages of being able to work in any direction of flow and being simple mechanism, compared with horizontal axis tidal turbine, it has a lower power coefficient. In addition, researchers also review that hydrodynamic torque on rotors shows the fluctuation in operation, which has negative effects on structure safety of turbine. What's more, electric generator is usually connected with tidal turbine directly or indirectly, and the load torque associated with rotational speed and parameter of electric generator has effects on the performance of tidal turbine. So, to diverse kind of power producer, the output power of turbine can be different from one another in the same work condition.First, the hydrodynamic performance of tidal turbine which tested in place was analyzed by using ANSYS FLUENT software. Consider the varying rotational velocity and load from output end, and model four conditions according to diverse load coefficients of electric generator in the process of analysis. The results indicate that rotational velocity of turbine vary periodically when it runs. And its fluctuation become more dramatic with the rise of load coefficient. Besides, to some extent, the output power coefficient of turbine can be up to 46% when load coefficients increase in a reasonable range. And if beyond that, the turbine will fail to give a normal operation.Second, in view of the drawback of vertical axis tidal turbine, in this paper, present a feasible duct, and then analyze the performance of duct. It reviews that the area with higher flow rate is located in the middle of duct and the maximum value can be twice the current velocity.Finally, form the turbine and duct in a part to analyze its hydrodynamic performance with the same method, and make a comparison with previous results to review the mechanisms of interaction between tidal turbine and duct. The results show that, a duct can dramatically enhance the velocity of tidal flowing through duct, nevertheless, for certain instances, the duct with a turbine will lead a negative effect on that. Though, the duct can also improve output power coefficient of tidal turbine from 46% to 58% by smoothing the fluid and weakening flow tread of fluid towards outside. What's more, the results also suggest that duct has abilities to reduce the fluctuation of hydrodynamic torque on rotor and rotational speed of turbine, which benefits the structure safety.