Research On Parameter Optimization Design Of Vertical-axis Dual-rotor Tidal-current Turbine

With the gradual shortage of global resources,the tidal energy,a clean energy with huge reserves,has become a new energy development trend in over the world.At present,tidal energy turbines,as the important device for the development and utilization of tidal energy,have appeared many different types under different sea conditions.Owing to strong ability to adapt to different incoming flow directions,vertical axis turbine has attracted extensive attention and research in recent years.Compared with the power generation capacity of vertical axis single-rotor current turbine,the dual-rotor tidal-current turbine can bring more significant economic benefits due to the different layout methods.Therefore,studying the structural layout parameters of the dual-rotor turbine is an important link to solve the problem of future tidal current power generation scale.At first the working principle of the vertical-axis turbine was introduced in this dissertation,and analyzed the overall and local stress of the turbine and defined the dimensionless parameters of the relevant structure.By comparing with the four vertical axis turbine research methods,the CFD method based on STAR-CCM+computational fluid dynamics software was determined to use in this dissertation as a research method.After that,through grid independence verification,unsteady time step verification and comparison with previous experimental data,a reliable numerical simulation method for studying vertical axis turbines was obtained.Based on this method,the variation law of the output torque of the turbine blade is summarized.Subsequently,the energy efficiency of single-axis and double-rotor turbines was calculated numerically,and it was concluded that the double-rotor turbines could improve power generation efficiency to a certain extent.Finally,this dissertation carried out numerical calculations on the parallel-arranged dual-rotor turbines from the two aspects of the distance between the rotating shafts and the relative position angle between the rotors.The characteristics of the flow field,the difference in energy efficiency between the rotors and the change in energy efficiency gain of the dual-rotor turbine are analyzed in detail.The study found that the energy efficiency of the dual-rotor turbine is not linearly related to the distance between the rotating shafts,the reasonable spacing of the rotating shafts(D_y=1.4D)can maximize the energy efficiency of the turbine,the maximum energy efficiency gain rate is 31.01%.In addition,in the area of high peak speed ratio,increasing the relative position angle between two rotors has a positive effect on improving the energy utilization of the turbine.Therefore,when designing the layout parameters of the dual-rotor turbine,the research results of this paper have a high reference significance.