Operation Hydrodynamic Numerical Analysis Of Current Energy Vertical Axis Tidal Turbine

Tidal current energy has become a central issue for its unique features in the renewable marine energy resources.The vertical axis tidal turbine,which is the significant device in the tidal current energy,has enjoyed high favor among the researchers for its simple structure,easy processing,low profit and non-affection with the direction of flow.In the previous numerical studies,it is quite different from the facts that vertical axis tidal turbine is often assumed to whirl in a constant angular velocity to analyze the hydrodynamic performance.The present study aims to adopt a dynamics method considering mass system based on CFD Numerical simulation of vertical axis tidal turbine and the characteristics of the performance on the angular velocity as the time changing,considering the affection of instantaneous steering angular velocity of the impeller by system damping and rotational inertia.It makes the simulation of vertical axis tidal turbine more precisely,so that the present study is of engineering significance.Firstly,two numerical methods of predicating the coupled motion performance in a fixed pitch vertical axis tidal turbine have been given at first,which is CFX User Fortran control method and CFX Rigid-body module.After the verification calculation,the feasibility and effectiveness has been testified.Secondly,the coupled motion hydrodynamic performance in a fixed pitch vertical axis tidal turbine has been studied by the control of CFX User Fortran to further analyze the affection of hydrodynamic performance by vertical axis tidal turbine rotational inertia,blade number,TSR and system damping.In addition,it has contrasted the computing results of coupling method(CFX User Fortran)and no coupling method(constant angular velocity).The findings show that the fluctuation amplitude of the angular velocity,thrust force and lateral force of turbine,the fluctuation of blade force have been reduced to enhance the operation efficiency of vertical axis water turbine because of the increase in the rotational inertia of vertical axis tidal turbine.To decrease the fluctuation amplitude of the angular velocity can be realized by increasing the TSR.Comparing the coupling method with the no-coupling method,the tangential force,normal force,thrust force and impeller moment are relatively low while the differences of lateral force in these methods are not significant.Finally,the analysis of the self-starting performance of the vertical axis tidal turbine with different blade numbers in different azimuths has been done by CFX rigid-body and the starting characteristic under the condition of different system damping of turbine.The findings are that the best self-starting azimuth of the vertical axis tidal turbine is ?=100°—120°.Electromagnetic torque has a great influence on the self-starting performance,which means the excess of electromagnetic torque coefficient leads to the loss of self-starting performance.When the self-starting performance vertical axis tidal turbine reaches the peak,the force bearing point of the spindle becomes the highest during the operation of vertical axis tidal turbine.