Analysis Of The Vibration In High-head Francis Turbine Caused By Rotor-stator Intercation

It has been recognized that pressure fluctuations in vaneless space are induced primarily by the interactions between runner blades and guide vanes,i.e,rotor-stator interactions(RSI). The pressure fluctuations in vaneless space are propagating all turbines,which may cause vibration of turbine. It has been found that a lot of abnormal vibrations caused by RSI exist in many hydropower plants, and the vibrations have been exerting great impact on the daily operation of these turbines, even the safety of the generator-sets in the powerhouses. In this paper the abnormal vibrations of No.1 turbine of Xiao Tiandu Hydropower Plant caused by RSI was inverstigated through theoretical analysis, prototype test and numerical simulation.The theoretical analysis method in hydro turbine fault diagnosis mainly focused on the relationship between the abnormal vibrations and structure of the turbine. Then the installation scheme of sensors was suggested after the analysis of mechanism in Rotor Stator Interactions(RSI).Field testing is the most direct means to investigate stabilization of the Francis turbine. During the prototype tests, vibration, oscillation, noise and pressure fluctuation signals were recorded simultaneously in order to analyze the root cause of the abnormal vibrations and noises. In this prototype test,two different water heads were selected to compare the results of the load-variant experiments at the test rig. It has been proved that the high frequency vibration of turbine is caused by RSI across changing the cascade combination of turbineAlso, the pressure fluctuation and velocity of spiral casing and vaneless space could be studied with the three-dimensional unsteady numerical simulation using two different guide vanes scheme. The former could verify with the experimental results that the pressure fluctuation frequency of the RSI exceeded all the other frequencies in the spiral casing and penstock. The latter is concerned with changing the cascades combination of the guide vanes and runner could alleviate the pressure fluctuation of the RSI frequency dramatically in spiral casing and vaneless space.