Research On Aerodynamic Performance And Structure Of Lift-drag Hybrid Vertical Axis Wind-wheel

Compared with the horizontal-axis wind wheel,the vertical-axis wind wheel has the natural advantage that no wind yaw device is needed;however,there are few high-power vertical-axis wind turbines above the megawatt level.The main reasons are: lift-type wind turbines have high operating efficiency but poor startability,resistance-type vertical-axis wind turbines have good start-up performance,but poor operating efficiency.The combination of vertical and horizontal wind-up-and-drag rotors is the solution to improve start-up performance but the operating efficiency is reduced.In order to solve this problem better,this paper aims at the aerodynamic performance and structure of the vertical resistance wind turbine with different combination scheme.Based on the operating characteristics of the vertical axis wind turbine,the operational phases of the vertical axis wind turbine were clearly divided,and the key issues of the entire operational phase were studied.From the theoretical point of view,the operating characteristics of lifting blades and resistance blades and the operating principle of the combined vertical axis rotor are analyzed.A calculation formula for the torque coefficient and power coefficient of a vertical-axis wind turbine with lift-resistance combination is provided to provide theoretical guidance for aerodynamic performance analysis and structural design in the following sections.In order to solve the problem of better matching between lift and resistance rotors,FLUENT fluid simulation software was used to study the aerodynamic performance of single blades and the semi-circular airfoil of the drag blade airfoil and the lift blade of the NACA0015 was determined.In order to obtain a combination of wind turbines with good starting performance and improved operating efficiency,FLUENT's "Sliding Grid Technology" is used to numerically simulate four different combinations of the circumferential directions of the resistance blades with respect to the lift blades.The four aerodynamic performance key issues of start-up performance,operating efficiency,cutout wind speed and limit load were studied respectively.Finally,the best combination scheme for the resistance blade with respect to the lift position of the blade is 45 degrees.In order to obtain a blade that satisfies both strength,stiffness and lightness.Firstly,the FLUENT simulation results were used to analyze the load type and size of the blade,and the internal support structure of the blade was determined.Then the ACP ply simulation software was used to select the blade ply material and layering scheme,and the two blades were divided into pavement areas.With the determination of the thickness,the weight of the two blades was 14.2 tons and 0.98 tons respectively;finally,the modal analysis of the designed blades was performed by ANSYS,and the structural vibration characteristics of the blades were determined,and the minimum vibration frequencies of the lifting blades and the resistance blades were 0.22671 Hz and 6.6739 Hz,which did exceed the frequency of 0.1404 Hz corresponding to the blade rotation angular velocity,avoided the occurrence of blade resonance.In order to obtain a complete design scheme of the wind wheel structure,determine the structural parameters of the wind wheel support arm and the diagonal arm,the main shaft and the hub,and analyze the stability of the pressure arm;use the ANSYS to analyze the mode shape of the designed wind wheel structure.The first-order natural frequency of the wind wheel is 0.52958 Hz,which is larger than the frequency of 0.1404 Hz,which can effectively avoid the resonance of the entire wind wheel and ensure the reliability and safety of the entire wind wheel operation.