Structural Optimization Design Of Wind Turbine Blade With Piezoelectric Material Driven Trailing Edge Flap

Wind energy is developing rapidly as a clean energy in our country,but the gradually large scale of blades leads to a series of technical problems,especially when the external wind conditions are more complex,blades are prone to flutter and fracture,which causes great economic losses.At present,there are many methods to improve the structural performance of wind turbines,among which adding flaps on the trailing edge of wind turbines is considered to have more development potential.Meanwhile,the structural performance of wind turbine blades is affected by the position of composite materials,fiber direction,preparation technology and other factors.Therefore,this paper studied the performance response of wind turbine blade structure under the combined action of material layout and trailing edge flap adjustment by changing the laminate structure of the piezo-driven flap wind turbine blade.The main research conclusions are as follows:1)Optimization of laminate layout for composite wind turbine blades.The aerodynamic load on blade surface under IEC6.2 design standard for large wind turbine blades was calculated based on Fast software.The mathematical model of leaf optimization was established by removing the material from the web,taking the removal of material aperture as the optimization variable,the maximum Mises stress as the optimization constraint,and the leaf quality as the optimization objective.Constrained Optimization By Linear Approximation（COBYLA）algorithm was used to realize the quality optimization design,and the final blade mass was reduced by about 1.7%.Since the production cost of blades is usually positively correlated with blade quality,this method provides a reference for wind turbine blade cost control.2)Optimization of laminating parameters for composite wind turbine blades.In order to explore the effect of composite laminates on the structural performance of wind turbine blades,the aerodynamic load of5MW wind turbine blades was calculated by Open Fast wind turbine design software.In addition,considering the effects of gravity and centrifugal force on blades,blade stress and Tsai＿Wu failure factor were considered as optimization standard,BOBYQA quadratic approximation optimization algorithm was used to optimize the layering angles under three laminate stacking schemes[0°/±45°/90°]_N,[0°/±45°/90°/±45°]_N and[±45°/0°/±45°/90°]_N,and the stress changes of each fiber layer before and after optimization were compared.The results show that the blade performance is affected by many factors such as stack angle and stack scheme,among which the stack angle has a significant effect on the blade performance,while the same stack angle combination,changing the stack sequence has a small effect on the blade performance.For sandwich structure wind turbine blades,compared with^{[0°/±45°/90°]}_N,laying scheme[0°/±60°/90°]_N can reduce blade load and tip displacement.Meanwhile,for the PVC sandwich structure wind turbine blade,its stress mainly acts on the glass fiber layer,the PVC layer stress is small,when the[0°/±X°/90°]_N layer is used,for 90°fiber layer is mainly used to resist the tensile and compressive stress caused by blade tip deformation,it is easier to be destroyed.3)Simulation of wind turbine blade flow field with trailing edge flap.Wind turbine blades are prone to flutter breakage under extreme wind conditions.It is considered that the trailing edge flap of wind turbine blades can regulate the flow field around the blades.Therefore,the fluid-structure coupling simulation of wind turbine blade with trailing edge flap was carried out to analyze the changes of flow field around wind turbine blade under different flap deflection angles.Flow field analysis shows that when the inflow yaw angle is 0°,the high speed region of trailing edge increases under the positive flap angle,while the high speed region of trailing edge decreases under the negative flap angle,and a low pressure region appears near the trailing edge;when the inflow yaw angle is 90°,the low speed region of suction surface increases under the negative flap angle,while the low speed region of suction surface decreases and the low pressure region appears at the trailing edge under the positive flap angle,and the high pressure region of pressure surface slightly increases;when the inflow yaw angle is-90°,the suction surface high pressure area increases under the negative flap angle,while the suction surface high pressure area decreases under the positive flap angle and low pressure area appears at the trailing edge,in this case,the flap deflection has little influence on the blade surface load.