| As the focus on renewable energy has grown,so has wind power.How to improve the wind turbine to improve the efficiency of power generation has become a hot issue for researchers.In order to improve the efficiency of wind energy utilization and the stability of the wind turbine,a modified blade design scheme was proposed for the wind turbine.The blade tip structure was changed into a double-fork blade tip structure,and the fork angles were 0°,30° and 60°,respectively.The numerical calculation of aerodynamic and vibration characteristics of wind turbine and tower,the dynamic response analysis under turbulent wind field,and the experimental study of natural frequency and vibration characteristics of wind turbine were carried out to explore the changes of dynamic characteristics of wind turbines with different blade tip structures under the influence of the coupling effect of wind turbine and tower.The main research contents of this paper are as follows:(1)Wilson design method was used to design the blade parameters,establish the three-dimensional flow field model and finite element model of the wind turbine and the wind turbine,and numerically calculate the aerodynamic characteristics of the wind turbine.The results show that the rotor torque increases after blade tip modification,and the pressure difference between the maximum pressure value of the blade pressure surface and the suction surface increases.(2)The established flow field model and finite element model are used to conduct numerical calculation and analysis on the wind turbine models not affected by coupling effect and those affected by coupling effect.The results of natural mode calculation show that the natural frequencies of the first to sixth order of the wind turbine and the amplitude of tip shimmy in the high-order mode can be reduced for the two modified blade tip structures,and the natural frequencies and modes of the tower are little affected.The natural frequencies of the wind wheel and tower are reduced and the mode shapes do not change obviously after the wind wheel-tower coupling effect.The calculation results of vibration characteristics show that the modified blade tip structure can reduce the first-order vibration frequency of the wind wheel and tower in the two models,make the rated speed of the wind wheel far away from the corresponding speed of the resonance point,and reduce the risk of resonance.The modified blade tip structure θ=60 ° wind turbine has the best improvement effect on the vibration characteristic curve of wind turbine.(3)The numerical calculation of the dynamic response of the wind turbine was carried out by using Matlab and Ansys co-simulation.The results show that the modified tip structure can increase the displacement response and stress response of the two models,but has little effect on the simplified tower model without coupling effect.The coupling effect of wind wheel and tower increases the displacement response of wind wheel slightly,decreases the stress response,and greatly increases the displacement response and stress response of tower.The wind turbine with modified tip structure θ=60° has the greatest influence on the dynamic response curve of the wind turbine.(4)The vibration acceleration sensor is used to carry out the modal test and vibration characteristic test of the wind turbine.The experimental results show that the natural frequency and vibration frequency of the unmodified wind turbine and the modified tip structure wind turbine decrease after the coupling effect of the wind turbine and the tower,and the amplitude of the frequency reduction of the modified tip structure wind turbine is larger.The experimental results are consistent with the numerical results,which verifies the accuracy of the numerical calculation.In this paper,the structural dynamic characteristics of the wind turbine,such as mode,vibration characteristics and displacement,under the influence of the wind-wheel-tower coupling are analyzed by numerical calculation and test,and the structural dynamic characteristics,such as vibration characteristics and dynamic response of the wind turbine with different tip structures,under the influence of the wind-wheel-tower coupling are analyzed.The research results provide a new idea for optimal design of wind turbine blade structure. |
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