水轮机真机转轮动应力试验分析

在一台容量为600 MW的大型水轮发电机组上开展运行稳定性及转轮叶片动应力试验研究.通过固定在发电机大轴顶端的无线动应力测试仪,实时采集机组运行过程中叶片上30个不同位置的应变数据,离线分析在导叶不同开度工况下的水轮机转轮动应力变化规律和频率特征;在动应力试验进行的同时,采用另一套基于NI硬件平台的测试仪对机组的运行稳定性指标进行实时分析,将稳定性试验结果与动应力测量结果进行比较并做相关分析,发现机组在导叶小开度工况约30%设计流量时,叶片动应力达到比涡带区更高的峰值,此时蜗壳压力钢管部位以及尾水部位的压力脉动波形在频域上与动应力的频谱有一定的相似性,在动应力和压力脉动的频谱上都可以看到较为明显的导叶通过频率和谐波以及分布在20~50 Hz区间的丰富频率成分.

Experimental analysis of dynamic stress on blades of hydro-turbine

A piece of experimental work is conducted on the different blades in the runner of a 600 MW hydro-turbine to study its operational stability and dynamic stress. The strain gauge data at 30 locations on a blade in the runner are acquired online by using a wireless dynamics stress instrument installed on the top of the power generator set, then the variation and frequency characteristics of dynamic stress at different guide vane openings are analyzed offline. Meanwhile, the vibration and pressure pulsation data in this machine are monitored simultaneously using another instrument based on NI hardware, the results are compared with and correlated to the dynamic stress observations. It is indicated that the amplitude of dynamic stress at round 30% design opening is higher than in the vortex-rope operational region, meanwhile the spectrum of pressure fluctuations in the penstock and draft tube has some similarity to that of dynamic stress. In the spectrum of pressure fluctuations and dynamic stress, the guide vane passing frequency and harmonics as well as plenty frequency components ranged in 30-50 Hz can be observed evidently.