无叶片风力机是通过其捕能柱的涡激横向摆动来捕获风能。建立了捕能柱三维涡激摆动的简化模型,推导了捕能柱系统固有频率及其能量捕获效率的计算式,并基于非线性回复力矩关系,构建了捕能柱的变固有频率计算式;在对简化模型进行验证的基础上,采用计算流体动力学(CFD)/刚体动力学(RBD)耦合方法,研究了变固有频率系统对捕能柱涡激横向摆动特性及捕能效率的影响。结果表明,非线性回复力矩函数斜率控制着捕能系统的固有频率,且非线性化程度越大系统固有频率变化速率越快;捕能柱横向摆幅峰值和能量捕获效率随回复力矩非线性化程度的增大而减小,其对应的风速向前推移;选择适当的变固有频率系统可增大主频锁定区间和高摆幅区间;捕能柱在涡激摆动过程中随柱体高度产生不同程度的斜涡脱落,对涡激摆动的频率锁定具有一定影响。
Abstract
Bladeless wind turbine captures wind energy through vortex-induced swing of its energy-capturing column. Here, a simplified dynamic model for 3D vortex-induced swing of the turbine system was established, and calculation formulas for natural frequency and energy harvesting efficiency of the turbine system were derived. Based on the nonlinear restoring torque function, the calculation formula for variable natural frequency of the turbine system was built. Based on verification of the established simplified model, effects of the variable natural frequency system on its swing characteristics and energy harvesting efficiency were further studied by using the computational fluid dynamics (CFD)-rigid body dynamics (RBD) coupled method. The results showed that slope of nonlinear restoring torque function controls variable natural frequency of the energy capturing system, the higher the level of nonlinearity, the faster the variation rate of natural frequency of the system; peak amplitude of swing and energy capture efficiency of the system decrease with increase in nonlinearity level of restoring torque, and the corresponding wind speed moves forward; selecting the appropriate variable natural frequency system can increase locking interval of main frequency and high swing amplitude interval; in process of vortex-induced swing, oblique vortex-shedding with different degrees occurs with height varying of energy-capturing column to have a certain effect on frequency locking of vortex-induced swing.
关键词
无叶片风力机 /
涡激横向摆动 /
变固有频率 /
捕能效率 /
非线性回复力矩
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Key words
bladeless wind turbine /
vortex-induced swing /
variable natural frequency /
energy harvesting efficiency /
nonlinear recovery torque
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脚注
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