大型风力机组停机状态下,塔筒与顺桨叶片尾涡干涉严重,进而产生叶片和塔筒的涡激共振现象,严重影响风力机可靠性。本文以NREL 5 MW风力机为研究对象,采用CFD与有限元方法,分别针对其流场与结构进行数值模拟计算,分析不同来流风速下叶片与塔筒一体化模型的模态频率与振型、尾涡形态与其脱落频率、以及表面压力变化特性。研究结果表明:风力机一体化模型的固有频率基频较小,低阶振型主要为风力机整体的摆振,高阶振型开始出现叶片的挥舞、摆振与扭转;在65~80 m高度区域内、8~12 m/s来流条件下,叶片与塔筒尾涡脱落存在尾涡合并现象,风速越大,合并现象愈明显,尾涡脱落频率也越高;10 m/s与12 m/s速度下,尾涡脱落频率与风力机固有频率较为接近,风力机易出现涡激共振现象。
Abstract
The wake interaction between wind tower and wind turbine blade is very serious resulting in the vortex-induced blade-tower vibration, which substantially affect the safety of the large-scale wind turbine. In this study, NREL 5 MW wind turbine is taken as the research object. CFD and finite element methods are used to calculate its structural characteristics and flow field respectively, and to analyze the modal frequency and mode shape, wake vortex and pressure distribution of blade-tower integration model under different incoming wind speeds. The results show that the fundamental frequency of the blade-tower integration model is small, and the low-order vibration mode mainly shows the oscillation of the whole wind turbine; flap, lag, twist of the blades appear in the high-order vibration mode. The existence of a strong mutually induced wake vortex between the blade and the tower at a height of 65-80 m and 8-12 m/s incoming flow conditions. There is a merging of the vortices between the blade and the tower. The higher the wind speed, the more pronounced the merging phenomenon and the higher the frequency of vortex shedding. The shedding frequency of the wake vortex is close to the natural frequency of the wind turbine when wind speed is in range of 10-12 m/s, which easily leads to vortex-induced resonance between the blade and tower.
关键词
风力机 /
塔筒 /
叶片 /
涡脱落 /
模态分析 /
涡激振动
Key words
wind turbines /
blades /
tower /
vortex shedding /
modal analysis /
vortex induced vibration
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基金
国家自然科学基金(51876054; 11502070; 12102125)