基础存在裂缝的风机塔振动测试与分析

Vibration Test and Analysis of Wind Turbine Towers with Cracks in Concrete Foundations

风机塔混凝土基础常存在开裂、不均匀沉降现象,严重时会导致塔筒倒塌。相比不均匀沉降,开裂程度特别是非表层的开裂难以直接测量,也难以准确评估其影响。对基础存在裂缝的风机塔开展振动测试与分析:首先选择一座基础出现开裂的风机塔和一座作为参考的同类型同场地的风机塔,同时开展振动测试;然后分析两座风机塔的振动特性;最后通过对比固有频率、振动强度等振动特性,发现相同测试工况下基础出现裂缝的风机塔的振动特性相比作为参考的风机塔,前三阶固有频率值虽然相差不大,但是其第3阶和第1阶的FFT幅值比远大于作为参考的风机塔;其加速度最大值在微风时与作为参考的风机塔相差不大,但是在风力较大或机舱偏航冲击工况下明显大于作为参考的风机塔。测试结果表明:塔筒加速度振动强度对基础裂缝比较敏感,而固有频率值不敏感,但是其高阶的FFT幅值对基础裂缝比较敏感。测试结果可为基于风机塔振动特性的变化快速评估基础裂缝的严重程度及分析此类型故障对风机塔运营安全的影响提供一定的参考。

The phenomena of cracking and uneven settlement are often found in the foundations of the wind turbine towers which may cause the towers to collapse. Compared with the uneven settlement, it is difficult to measure the cracks especially the internal cracks in the foundations directly. It is also difficult to evaluate the influence of the cracks on the safety of the towers. In this study, the vibration test and analysis are carried out on the wind turbine towers with cracked foundations.First of all, the vibration test is carried out on two wind turbine towers of the same type in the same site. One tower has cracks in the concrete foundation and the other as a reference is intact. Then, the vibration characteristics of the two wind turbine towers are analyzed. Finally, the natural frequencies, vibration intensities and some other vibration characteristics of the two towers are compared. It is found that the first three-order natural frequencies of the two towers only have small differences but the FFT amplitude ratio of the first order and the third order of the tower with cracked foundation is much larger than that of the reference tower. The difference of maximum acceleration values of the two towers in breeze condition is small. But under the larger wind or the engine room yawing condition, the maximum acceleration value of the failure wind turbine tower is significantly greater than that of the reference tower. The test results show that, the vibration intensity of the tower is sensitive to the foundation cracks and the natural frequency is less sensitive, but the high order FFT amplitude is sensitive to the foundation cracks. Test results can provide a reference to quickly evaluate the seriousness of foundation cracks and the influence of this type of defects on the safety of wind turbine tower operation.