Research On The Influence Of Duct On The Performance Of Vertical Axis Tidal Turbine

The vertical axis tidal turbine(VAT)sevred as an important part of obtaining energy has many advantanges,such as the simple structure of blades,which is adjust to the direction change of incoming flow without any yaw mechanism.However,the terminal generator which acted as a damper will produce load torque,which not only can change its motion but also reduce its power coefficient.In order to improve the power coefficient of the VAT,the influence of diversion device on the performance of VAT is studied in this paper.Otherwise,the influence of the generator(load)coefficient on the turbine is also necessary during the start-up process.Moreover,when the channel interacts with the turbine,the spacing between VAT and channell will also have a certain impact on the hydrodynamic performance.The numerical software Fluent is used to simulate the VAT in different load factors.The hydrodynamic performance of the turbine is analyzed from the state of motion,flow field,torque and power coefficient.The results show when the load torque is equal to the hydro moment,the turbine reaches the stable stage and the torque of the blade reaches the maximum at the upstream(?/2?=0.25).The power coefficient increases and then decreases with the increase of load factor.The maximum Cp is 0.45 when the load factor is 70.If beyond 90,the turbine will be reversed,which can lead to overload phenomenon.Secondly,In order to solve the influence of the violent fluctuation on the device structure,a new type of flow control device came into being.Through simulating the performance of the device,The conclusions show that the flow speed can largely be increased twice than ever in the middle of the duct.Thus,the turbine's horizontal position is established in the middle of the turbine.Finally,taking the impact of the variable speed,load factor and the gaps into account,the hydro performance of the channelled turbine is investigated.Compared with the duct,it show that the exist of turbine not only hinders the water flow inside the duct,but also reduces the flow mass rate of the water.in addition,when it is compared with the standalone turbine,we can concluded the speed and torque ripple coefficient of the channelled turbine are greatly reduced,the power factor is increased more than 30%.Besides,the ripple coefficient of the channelled turbine drops to the lowest,and the efficiency reaches to the maximum.