| In order to study the vibration characteristics of wind turbines with different blade tip structures under yaw conditions,the aerodynamic numerical simulation,vibration characteristics numerical simulation,harmonic response simulation analysis with excitation frequency and natural frequency and vibration modal characteristics test of airfoil and rotor of wind turbine under yaw conditions were carried out to explore the variation of vibration characteristics of wind turbines with different blade tip structures under yaw conditions.(1)Firstly,using the Glauret design method,the S809 airfoil is selected to design the unmodified blade and the wind turbine blade with different blade tip structures.Two different tip structures are modified tip structure-1and modified tip structure-2.The ICEM is used to divide the structured grid.Based on the incompressible N-S equation,the wind turbine with S809 airfoil and different blade tip structures is numerically simulated in the simulation software.The numerical results show that the aerodynamic performance of the airfoil gradually increases with the increase of the angle of attack.When the angle of attack is 15 °,it is the critical stall angle of attack and the aerodynamic performance is the best at this angle of attack.With the increase of wind velocity,the turbulent kinetic energy increases,and the maximum turbulent kinetic energy is mainly distributed at the intersection of trailing edge separation vortices.As the yaw angle decreases,the pressure coefficient gradually increases,the area enclosed by the suction surface and the pressure surface increases,and the cross-section airfoil obtains greater lift.Through the pressure difference of wind turbines with different blade tip structures,the modified blade tip structure-1 wind turbine has better aerodynamic characteristics.(2)Then,using the results of numerical calculation of blade aerodynamic performance as the condition of applying load,the vibration modal calculation of wind turbine with different blade tip structures is carried out.The results show that with the increase of wind turbine speed,the first three order vibration frequency shows a gradual upward trend,while the modified blade tip structure can reduce the increase of wind turbine vibration frequency compared with the unmodified blade tip structure wind turbine.The effect of modified blade tip structure-2 on reducing vibration frequency is the best and the modified blade tip structure-2 can break away from the triple frequency resonance band faster.With the increase of yaw angle,the vibration frequency of modified tip structure-2 wind turbine increases the smallest and the vibration frequency is the lowest.The excitation frequency is applied to the wind turbine with different blade tip structures.The modified blade tip structure wind turbine can reduce the resonance frequency range compared with the unmodified blade tip structure wind turbine.(3)Finally,the blade modal test and the dynamic vibration test of the wind turbine in the wind tunnel were carried out.The vibration frequency and vibration acceleration amplitude of the wind turbine with different yaw angles,different inflow wind speeds and different blade tip structures were tested and analyzed.The test results show that the modified blade tip structure-2 wind turbine can effectively reduce the vibration acceleration amplitude at the second-order vibration frequency at different yaw angles compared with the unmodified blade tip structure wind turbine.When the yaw angle is 0°,10°,20° and 30°,the modified blade tip structure-2 wind turbine can effectively reduce the vibration acceleration amplitude in the x-axis and y-axis directions,and the vibration frequency and vibration acceleration amplitude in the z-axis direction are concentrated between300Hz-400Hz;through the comparative analysis of test data and numerical simulation data,the correctness and reliability of the test and numerical simulation are further verified.There are errors between the test results and the numerical simulation results,but their development trends are consistent.In this paper,the vibration modal analysis of wind turbines with different blade tip structures under yaw condition is carried out.The aerodynamic load of the wind turbine is used as the applied load condition,and the variation law of the vibration characteristics of the wind turbine under different working conditions is analyzed by changing the yaw angle and the tip structure.Finally,the test and simulation results are further compared and analyzed. |
