| Due to the predictability and huge reserves of tidal energy.It is considered to be a promising renewable energy to solve the power supply difficulties in coastal areas and some remote islands.Impeller,as the core structure of hydraulic turbine.It has always been the focus and difficulty of experts at home and abroad.According to the characteristics of traditional vertical axis turbine.This paper designs a lift drag compound impeller.The purpose is to realize the passive deflection angle of the blade through the gear transmission mechanism.While obtaining high energy utilization,it also enables the impeller to obtain large starting torque.Thus,the weakness that the traditional lift turbine cannot start by itself is effectively improved.Through ANSYS FLUENT software.The hydrodynamic performance of half rotating impeller of lift drag compound turbine is analyzed.The relevant parameters affecting the energy utilization rate of the impeller are explored.It has a certain reference value for the improvement and further research of the performance of lift drag turbine.Firstly,the research background,significance and research status of tidal current turbine at home and abroad are introduced.And the research status of half rotating impeller and variable deflection angle turbine.Facing the current situation that domestic research lags behind western countries.China should speed up the pace of in-depth research and development of new energy.By analyzing the current research direction and relevant technical means.Review of large tidal current power generation units that have been in commercial operation.Based on the current characteristics of vertical axis turbine,the research focus and direction of this paper are clarified.Secondly,based on the principle of half rotating mechanism,the working process of double blade half rotating impeller is analyzed.The hydrodynamic calculation model is established based on the disk flow tube model of leaf element theory.The movement and force of the blade are studied,which provides a theoretical basis for the later impeller design.During data processing,the results of theoretical analysis and numerical simulation can be combined for comparative analysis.As the impeller rotates,the blade itself is also rotating around the central axis of the blade,UDF can be used to control this more complex movement mode.Then,a device with high energy efficiency at low flow rate is designed.The parameters of the half rotating impeller are set and its hydrodynamic performance is studied.According to the principle of semi rotating mechanism,the tie rod can be designed as a rotating arm.The blade is used to replace the position of the half rotating component,so as to design the three-dimensional model of the half rotating impeller.The model is simplified and only the blades are retained for hydrodynamic analysis.Import the blade model into ICEM,create the computing domain and complete the meshing.Then,fluent is used to solve and calculate.To the post-processing module,through the processing and calculation of the results.The variation of turbine energy utilization and torque coefficient with speed is analyzed.Because the dynamic performance is closely related to the flow field,the variation law of the flow field is also analyzed and summarized.The internal mechanism of high energy efficiency of half rotating impeller is studied.Then,the different inflow velocity,impeller diameter,blade number and blade aspect ratio are studied.Influence on energy utilization of half rotating impeller.The incoming flow velocity has little effect on the energy utilization.However,the higher the inflow velocity,the greater the corresponding optimal speed and output power;Impeller diameter has a great influence on energy utilization.Because the impeller diameter affects the overall density of the impeller,a relatively small impeller diameter can keep the energy utilization in a high range;More blades will affect the flow field and make the flow field more complex.As a result,the energy utilization rate of the impeller is low;When the aspect ratio of the blade is 4,the energy utilization rate of the impeller is the best.Through the analysis of influencing factors,the relationship between impeller parameters and energy utilization is determined.It is of great value to the design and research of impeller.Finally,based on the design theory of airfoil and the design method of reversible airfoil.Through numerical simulation,the hydrodynamic performance of naca4412 airfoil and NACA0012 airfoil are compared.Naca4412 airfoil with better comprehensive performance is determined to be used as the original airfoil.An S-type reversible airfoil suitable for positive and negative working conditions is designed.NACA0012,naca4412,N1,N2 and flat plate are applied to the half rotating impeller.The effects of different blade shapes on energy utilization and torque coefficient of half rotating impeller are analyzed. |
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