Design And Optimization Of Blade For Low Velocity Marine Current Turbine

At present,mankind's demand for energy is increasing,while the stock of traditional fossil energy is decreasing.The development and utilization of renewable energy has become an important support for global sustainable development.As a kind of renewable energy,ocean current energy has attracted attention from all over the world due to its large inventory,green and clean characteristics.However,a large part of the world's oceans have low velocity.How to make efficient use of ocean current energy resources in low-velocity oceans is an important research content in the field of ocean energy development and has great engineering value and strategic significance.In this paper,the impeller structure of the low-velocity ocean current energy unit is studied.From the perspective of airfoil structure optimization,blade hydrodynamic shape design based on different blade number configurations,and concentrating hood design,the energy capture characteristics of the low-velocity impeller and its performance are completed.Research on structural characteristics.The contents of each chapter are as follows:The first chapter introduces the research background of this subject.The development status of sea current energy generating units under the conditions of conventional flow rate(usually above 2m/s)and low flow rate are described respectively,and the research content and significance of this paper are proposed.The second chapter introduces the basic theory of blade design and the optimization design method of airfoil.It mainly describes the design method based on leaf element momentum theory,the parameterized expression of airfoil and the optimization method of airfoil.In chapter 3,CFD simulation analysis is performed on different airfoils,the basic airfoil of low-flow blades is determined,and the airfoil is optimized based on genetic algorithm.The pressure distribution and lift resistance performance of the airfoil are analyzed to provide parameter basis for the subsequent blade design.Chapter 4 designs the blade hydrodynamic structure with different blade numbers based on the theory of leaf element momentum.By comparing and analyzing their starting performance,energy harvesting efficiency and axial thrust,the optimal structural configuration of the impeller is determined.Finally,the mechanical properties of the blade were checked,including static strength,deflection and natural frequency,and the surface cavitation of the impeller was analyzed.In the fifth chapter,in order to effectively improve the utilization efficiency of low flow velocity and reduce the size of the energy harvesting mechanism,based on the theory of negative pressure,the design of the concentrating hood with different parameters,and the CFD method was used to simulate and analyze the effect of speed increase of the ocean current and determine Concentrating hood structure with the best speed increasing effect.Through the overall simulation of the concentrating cover and the impeller,the effectiveness of the concentrating cover to increase the energy capture efficiency of the impeller is verified.Finally,a low-velocity bidirectional impeller performance test system was built in the sea area of Zhailuo Mountain in Zhoushan and related experiments were conducted.Chapter 6 summarizes the research work of the subject and proposes further research directions.