Experimental Research On Hydrodynamic Performance Of Active Pitch Vertical Axis Tidal Turbine

The development of ocean renewable energy is an important part of the optimization of the energy structure,as well as a part of improving our country's marine resource development capabilities.Compared with fossil energy,ocean renewable energy is not only clean,but also has huge reserves.It also provides ideas for solving the problem of power supply for ships and islands in the deep sea,and is of great practical significance for building a powerful nation of marine.Among all sorts of ocean renewable energy,tidal current energy has attracted wide attention of researchers due to its high energy density,high predictability,and high stability.The vertical axis turbine is a tidal current energy conversion device and has nature of universal convection,which makes its structure simple.Since it does not require a convection device,the cost is lower than that of a horizontal axis turbine.The blade pitch technology is one of the efficient methods to improve the energy conversion efficiency of vertical axis turbines.Its principle is to increase the blade lift and change the blade hydrodynamic coefficient by changing the blade deflection angle,so as to obtain higher torque and lower load fluctuation.Based on the genetic algorithm,Dr.Jiang Jin from our research group proposed an optimal pitching law under constant speed ratios.Numerical simulation studies have found that the power coefficient of variable pitch turbine using this pitching law can be increased by a maximum of 0.2 compared to that of a fixed pitch turbine.On the basis of optimal pitching model proposed by Jiang Jin,this paper takes the turbine power coefficient as the objective function to solve and fit the pitching law function of the best power coefficient under different blade tip speed ratio conditions.Then active pitch turbine experiment model and scheme are designed to study the power performance and load performance of the variable-pitch turbine under the influence of different parameters.A fixed pitch turbine experiment is conducted to verify the performance advantages of the active pitch turbine over the fixed pitch turbine.First,the theory and experimental research methods of vertical axis turbines are reviewed,and the current research status of fixed pitch turbines and variable pitch turbine are described.Thus,the shortcomings in the active pitch experiment research are analyzed.Second,the motion model,force analysis and numerical simulation method of variable pitch turbine are introduced.Then,experimental model and experimental scheme are designed to study the performance of a cantilever active pitch vertical axis turbine.The experimental model introduces the blade pitch control mechanism,main shaft wheel and support and arm mechanism,the upper frame of the experimental platform and the test instruments used in the test in detail.The experimental scheme includes the experimental process,working condition parameters,instrument calibration,experimental data processing and error analysis,etc.And validation of experimental data and numerical simulation is carried out to verify the numerical model.After that,based on the experimental results,the power and load performance of the active pitch turbine are analyzed from the three aspects of solidity,incoming flow velocity and blocking ratio.Finally,a comparative analysis of the experimental performance of fixed pitch and variable pitch turbines is carried out,and the influences of solidity,incoming flow velocity and blocking ratio on the advantages of active pitch turbines over fixed pitch turbines in terms of power and load under specific conditions are discussed.