The Numerical Analysis And Optimal Design Of The Tidal Current Turbine Balde

With the decline of the traditional energy reserves and the deterioration of the environment,the research and development of new marine energy has gradually become the focus of the maritime powers.In 2012,China has firstly proposed the strategic policy of building a maritime power.Tidal energy,as a new marine energy,has strong regularity and high efficiency.The hydraulic turbine is a device which can transform the abundant mechanical energy contained in the power flow energy into electric energy.As the key part of the turbine,the blade will directly affect the energy acquisition efficiency of the machine.Compared with foreign countries,China's application scale in the field of tidal power generation is still small.Accordingly,it has been the main research content for China to study how to use the power flow energy efficiently for power generation.For this purpose,it is necessary to increase the innovation in the structural design of hydraulic turbines,and develop a variety of current energy hydraulic turbines to meet the specific requirements of work in different sea areas.On the other hand,the researchers can also develop new hydrofoils suitable for tidal turbines.In this way,under the condition of meeting the structural strength requirements,it can improve the hydrodynamic performance of the flow energy turbine blades so as to improve the energy efficiency of the turbine.Therefore,the key content of this paper is to improve the hydrodynamic performance of blades.In this paper,design a new type of tidal current turbine with NACA4412 hydrofoil as its initial hydrofoil.In addition,change the four main geometric parameters of the hydrofoil,and then analyze the influence of different geometric parameters on the hydrodynamic performance of the hydrofoil.Finally,optimize the hydrofoil according to the obtained laws and obtain a new hydrofoil.The specific contents are as follows:To begin with,use a professional design software for hydrofoil—Profili to modify the geometric parameters of the initial hydrofoil by changing the single variable method.The maximum thickness,maximum curvature,maximum thickness position and maximum curvature position of the initial hydrofoil are all changed.Secondly,after finishing the hydrofoil modification,use Fluent software to simulate each hydrofoil in the range of-5°?25° attack angle.After the calculation,compare the lift drag coefficient,lift drag ratio,surface pressure distribution of the hydrofoil and the velocity streamline of the trailing edge with the initial hydrofoil in the whole angle of attack,so as to explore the influence of different geometric parameters on the hydrodynamic performance of the hydrofoil.Furthermore,the influence of the geometric parameters on the performance of the hydrofoil is taken as the constraint condition of the optimization design of the hydrofoil.Then,the Hicks-Hence type function method is used for the parametric modeling,and 6° is determined as the optimal angle of attack.After that,take the high lift drag ratio as the optimization goal,and adopts the multi island genetic algorithm to optimize.After the optimization,obtain a hydrofoil with high lift drag ratio.Finally,after getting the optimized hydrofoil,use Fluent software to simulate the hydrofoil and then compare the optimized hydrofoil with the original NACA4412 hydrofoil in lift coefficient,lift drag ratio,surface pressure distribution of special angle of attack and streamline diagram of hydrofoil trailing edge velocity.Through the analysis,it can be found that the lift coefficient and lift drag ratio of the optimized hydrofoil are higher than those of the original hydrofoil in the whole range of attack angle,and the advantage of lift drag ratio of the optimized hydrofoil before reaching the stall angle of attack is particularly obvious.In addition,when the angle of attack is 6°,the optimized hydrofoil lift drag ratio is 18.904,which is 20.1% higher than the maximum lift drag ratio of the original hydrofoil.What is more,it is also proved that the optimized hydrofoil has more dynamic performance from the cloud chart of the surface pressure distribution of the hydrofoil and the streamline chart of the trailing edge of the hydrofoil.All these further prove that the optimization method is correct.