风力机风轮振动频率及应力特性试验研究

Experiment on vibration frequency and stress characteristics of wheel in wind turbine

利用Pulse16.1结构振动分析系统,针对直径为1.4 m的小型水平轴风力机风轮进行静态固有振动频率和动态振动频率测试.研究发现:气动载荷对风轮二阶以下振动动频影响相对较小,且对一、二阶反对称振动动频的影响略大于对称振动动频;离心力对风轮二阶以下振动动频影响较显著,且对一、二阶对称振动动频的影响大于对反对称振动动频.此外,圆盘效应所引起的振动应力高于二阶以下其他振动应力,轴向窜动效应引起的振动应力介于一、二阶振动应力之间,这一结论与风轮静频测试中所获应力结果有很大的差异性,从而也考证了通过风轮静态测试间接分析其动态振动应力的方法并不适用.相关研究成果可为风力机在远短于设计寿命期内频繁发生疲劳损伤或断裂提供新的分析思路,同时为小型风力机风轮结构动力学性能的合理设计提供一定的理论支撑.

The static natural frequency and dynamic vibration frequency of three 1. 4 m diameter wheels in a small horizontal-axis wind turbine were measured by using Pulse16. 1 structure vibration analysis system. It was identified that the aerodynamic load has a weaker effect on the 2nd-order or less dynamic frequency of vibration;furthermore,the load affects the 1st and 2nd-dynamic frequencies of anti-symmetric vibration slightly dominated than on those of symmetric vibration. The centrifugal force exhibits a relatively remarkable influence on the 2nd or less order dynamic frequency of vibration,especially the force can affect the 1st and 2nd-order dynamic frequency of symmetric vibration more greatly than on those of anti-symmetric vibration. Besides,the vibration stress caused from disc effect is higher than the other 2nd or less vibration stresses. The vibration stress caused from axial movement effect is in between the 1st and 2nd order vibration stresses. This observation is quite different from the vibration stress measured from a static wind wheel. Clearly,it is inappropriate that the dynamic vibration stress is analyzed indirectly through measuring the stresses in a static wheel. These results can provide some new ideas and a theoretical support in analysis of fatigue damage or break which frequently occurs in wind turbine wheels in a period of time that is much shorter than the design life span of a wheel.Meanwhile,they can provide a theoretical support in designing a reasonable dynamic performance for the wheel in a small-scale wind turbine.