Reserch On A Bidirectional Tidal Current Turbine (TCT) Combining With A Permanent Magnet-directly Driven Generator System

With the exhaustion of the sources of petroleum and coal, the conversion of thekinetic energy present by tidal stream offers an alternative as it can provide regular andpredictable energy resource. And how to solve the difficulty of supplying food andpower to isolated island was set forth in the Eleventh Five-Year Plan. Taking thesethings into account, the performance of bidirectional tidal stream power device isstudied in present dissertation.The dissertation consists of four parts. The first part is a prolegomenon; it describesthe background of the subject and gives an introduction to some of the current situationof TCT both at home and abroad. Finally, several TCTs are reviewed in detail, and theadvantage and disadvantages are pointed out.The second part is the bidirectional airfoil design. The tidal current turbine has towork at both of the tidal current directions. The common airfoils have goodaerodynamic performances when they face incoming flow, but the aerodynamicperformances get worse when their back is towards incoming flow. To solve thisproblem, steering which is transferred from wind turbines is the routine solution, butunderwater installations and maintenances are very difficult and expensive. In order tosolve the above problems, the bidirectional airfoil is created designed and investigatedin the dissertation, which has nearly the same hydrodynamic performance at both of thetidal current directions.Blade design and numerical calculation is the third part. The tidal current turbineblade is designed by using blade element momentum (BEM) theory. In order to reducecomputing time, the flow field of computing model is divided into two ranges to formrotating domain and static domain. Numeca and Ansys-CFX are used to predict thehydrodynamic performance of this turbine. The grid generation of the blade and flowfield is completed by using the numeca software. And then, the grid model is importedinto ANSYS-CFX with some other manipulations, such as delimiting the boundaryconditions and solves the N-S equation, etc. The power coefficient of bidirectional tidalstream turbine obtained by CFD method is39.536%at the design tip speed ratio.Model test is the fourth part in present dissertation. System structure design, powertest and the efficiency test of system are the major parts. The turbine speed and outputpower are modified through changes in external loads in this test. The power coefficientof bidirectional tidal current turbine is obtained after the power test and the efficiencytest of system. Through the comparison between experimental results and numericalprediction results, the correctness of the numerical method and the feasibility of someinstruments in the model are validated.