Design Of A Tidal Energy Extraction System Based On A Double Hydrofoil Linkage And Hydrodynamic Analysis

In order to reduce the dependence on fossil fuels and to control environmental pollution,our government has paid more attention to the development and utilization of clean and renewable energy.As a kind of ocean energy,Tidal current energy has great development value for coastal provinces.This paper study a tidal energy extraction system based on a double hydrofoil linkage.Provide reliable theoretical support for the design of power generation devices in the future.The oscillating motion of the hydrofoil can be decomposed into the vertical motion and the pitching motion of the hydrofoil around the pitch axis.The double hydrofoil linkage not only convert the water power into mechanical energy of the generator,but achieve a good self-maintenance and self-starting performance to the system.In order to study the performance of the double hydrofoil linkage system,this paper has done the following research work:Introducing the basic principle of a tidal energy extraction system based on an double hydrofoil linkage,and the concept of hydrofoil.Discuss the the hydrodynamic performance of hydrofoil based on the CFD technique.According to the results of the analysis,take the profile of NACA0018,the reduced frequency of 0.14,the piching of 75° as the basic parameters for the design of the tidal energy extraction system based on an double hydrofoil linkage.Establish a mathematical model of oscillating hydrofoil with large angle of attack based on the Theodorsen theory,and calculate the hydrodynamic characteristics of hydrofoil NACA0018,then compare the results with numerical simulation results based on Fluent.Comparison results show that this mathematical model can obtain good hydrofoil hydrodynamic prediction results,and could be used to cauculate the hydrodynamic coefficient of hydrofoil for the hydraulic system.Design the hydraulic system according the principle of the tidal energy extraction system based on a double hydrofoil linkage,and build a model of the hydraulic system based on AMESin software,then build a union model with Simulink by data interface.The influence of the inner diameter of the lifting cylinder on the hydrofoil and the hydraulic system is studied.When the power generation system catapult energy is 2kW,the oscillation period T = 2s,chord length and sag motion amplitude is 0.5m,for three group hydraulic cylinder diameter of 25mm,30mm and 35mm,the smaller the inner diameter,the higher the efficiency of the system,the higher the transmission efficiency.D = 30mm model can obtain 28.73%capture efficiency and 69.83%transmission efficiency;Applied a disturbance force which duration one oscillation period and the amplitude on the hydrofoil,the results shows that under the positive and negative disturbances,the double hydrofoil linkage can return to normal oscillation after 3 cycles.