水中运行设备共振幅频特性研究  

esearch on amplitude and frequency characteristics of resonance of equipment operating in water

作　　者：徐洪泉[1] 周叶[1] 廖翠林[1] 曹登峰[1] 邹志超 XU Hongquan;ZHOU Ye;LIAO Cuilin;CAO Dengfeng;ZOU Zhichao(China Institute of Water Resources and Hydropower Research,Beijing 100038,China)

机构地区：[1]中国水利水电科学研究院,北京100038

出　　处：《水利学报》2023年第5期610-620,共11页Journal of Hydraulic Engineering

基　　金：中国水利水电科学研究院科研专项项目(HM0145B432016)。

摘　　要：在水力机械等淹没水中设备的运行中,常遇到剧烈振动造成设备损坏等故障,多认为由共振引起。本文首先对单自由度简谐振动系统自由振动、强迫振动方程的稳态振动解进行无量纲化处理,计算出不同阻尼比条件下的共振频率比、共振幅值比,发现阻尼比、共振频率比、共振幅值比三者之间存在一一对应的单调变化关系,并据此提出了分别测量设备在水中及空气中的自由振动频率,假定空气中自由振动频率为设备固有频率,再依次确定水中阻尼比和共振幅值比的反求式估算方法。本研究采用敲击法进行了混流式水轮机模型转轮水中及空气中自由振动频率测试,发现其水中自由振动频率比空气中低,其水中一阶自由振动频率与空气中一阶自由振动频率之比约为0.758~0.872;如假定该值为水中自由振动频率比,可计算出相应的水中阻尼比为0.652~0.490,共振幅值比约为1.01~1.17。本研究还进行了中间固定两侧悬臂梁在空气及水中的真实共振试验,在两侧悬臂梁计算固有频率附近均发生明显共振,发现水中共振频率比空气中明显降低,用反求法获得的水中共振幅值比小于2,水中共振幅值对空气中初始振动幅值放大倍数也非常小,进一步说明水中共振时对激振幅值的放大作用非常有限。In the operation of equipment submerged in water such as hydraulic machinery,faults such as equipment damage caused by severe vibration are often encountered,which are mostly considered to be caused by resonance.Dimensionless treatment is carried out for steady-state vibration solutions of the free vibration and forced vibration equations of the simple harmonic vibration system with single degree of freed firstly.Then the resonance frequency ratio and resonance amplitude ratio with different damping ratios are calculated and it is found that there is a one-to-one corresponding monotonically varying relation between three ratios.A reverse estimation method is proposed and that is to measure the free vibration frequency of equipment in water and air respectively,assume the free vibration frequency in air is the natural frequency,and then determine the damping ratio and resonance amplitude ratio in water.The research uses the hammering method to measure the free vibration frequency of the model Francis turbine runner in water and air.It is found that the free vibration frequency in water is lower than that in air,and the ratio of the first-order free vibration frequency in water to that in air is about 0.758~0.872.If this value is assumed to be the free vibration frequency ratio in water,the corresponding damping ratio in water can be calculated to be 0.652~0.490,and the amplification ratio of the resonance amplitude is about 1.01~1.17.In this study,the real resonance test of the cantilever beams fixed in the middle was also carried out in air and water.Obvious resonance occurs near the calculated natural frequency of the cantilever beam during vibration test.During the vibration test in water,it was also found that the resonance frequency was significantly lower than that in the air.The ratio of resonance amplitude in the water obtained by the reverse method was less than 2,and the magnification of resonance amplitude in the water to the initial vibration amplitude in the air was also very small.It further indicate

关 键 词：水轮机转轮 悬臂梁 共振 自由振动 固有频率 阻尼 振幅 

分 类 号：TV734[水利工程—水利水电工程]