Research On The Optimization Design Of H-shaped Vertical Axis Wind Turbine Blade Structure Based On Fluid-structure Coupling

The countries around the world have invested heavily in clean and renewable wind resources,which accelerates the rapid development of wind power industry.The small H-type vertical axis wind turbine has the advantages of simple structure,friendly maintenance and low noise.However,the wind energy utilization is low,and the coupling effect between the structure and the flow field aggravates the deformation of blade,which leads to the serious degradation of structure performance.The performance of the wind turbine can be improved by adjusting the blade's structure and aerodynamic shape of the airfoil.Therefore,this paper performs the analysis of aerodynamic performance of trailing-edge modification for H-type vertical axis wind turbine blade considering camber effect and the optimization of structural geometry parameters and composite layer of the blade under fluid structure coupling condition.These studies have great engineering value of application for improving the wind energy utilization and obtaining the maximum economic benefit.The main research work and results are as follows:(1)Based on the theory of aerodynamic design,the geometric size design of the wind wheel of 100 W H-type vertical axis wind turbine are designed.Then,the blunt trailing-edge optimization and sharp trailing-edge modification are performed for NACA0021 airfoil,and the change rule of the wind energy utilization with the trailingedge thickness is analyzed.The airfoil's relative camber is then increased by making the middle arc line locate on the circumference of wind wheel,and the effects of the relative camber on the pressure and vorticity distribution,torque coefficient and wind energy utilization are investigated.The results indicate that after the relative camber increases,the positive and negative pressure region areas for airfoils decrease,and so do the length and distribution of the wake,but the torque coefficient and wind energy utilization increase.(2)The stress and strength ratio of the component under the bending deformation are solved by the analytic method and finite element method,and the results are compared and analyzed.The parametric finite element model of the blade with camber and sharp trailing-edge airfoil is established with the APDL language.The real-time pressure distribution on the blade surface is calculated by FLUENT to obtain the aerodynamic force using the FSI mapping method.Taking the minimum blade mass and maximum laminate strength ratio as the design objective,the multi-objective structure optimization under combined action of the gravity,centrifugal force and aerodynamic load is performed.The results indicate that after the optimization of single blade at different azimuth and wind wheel,the mass,maximum stress and displacement decrease,the phenomenon of stress concentration is weaken,and the strength ratio increases for the blade.(3)Based on the ANSYS Workbench platform,the geometric model,computational domain and grid of wind wheel are constructed,the turbulence model,boundary conditions and composite material laying are set up,and the fluid domain and solid domain are solved in a coupled way.The single-objective optimization of the blade structure under fluid-structure interaction conditions is performed using the response surface methodology to minimize the mass of wind wheel,which takes the thicknesses of glass cloth,colloid cloth,foam and the positions of webs as design variables.The frequency and vibration mode of original and optimized blades with and without pre-stress,and the displacement,stress and strain of wind wheels under different wind speeds,are studied.The results indicate that after the blade structure is optimized,the first-order frequency and critical speed become larger and other frequencies decrease in static,single pre-stress and multiple pre-stresses conditions.The first-order critical speeds before and after the optimization are greater than 20% of five times the rated speed of wind wheel,and the resonance phenomenon will not occur.The maximum displacement,stress and strain of wind wheel decrease under rated and extreme wind speeds,and the structural performance improves.