| In recent years,cracks in blades of Francis turbines in some hydropower stations both here and abroad have resulted in severe vibration of turbines and seriously endangered the operation safety of turbines.Shuiniujia hydropower station is one of them.Due to the complexity of the actual operation of turbines,the interaction between the runner and the flow field is one of the important factors leading to the fatigue fracture of blades and dynamic instability.Therefore,studying the fluid-structure interaction characteristics of turbine runner is of great significance for understanding the vibration mechanism of blades,predicting the crack location of blades,avoiding hydraulic resonance and ensuring the safe and stable operation of turbines in Shuiniujia hydropower station.In this paper,the flow field distribution and fluid-structure interaction characteristics of Francis turbines in Shuiniujia hydropower station under some typical load conditions are simulated and analyzed.The results provide a theoretical reference for the optimization design of turbine overflow parts and the treatment of runner blade defects.The main research works are as follows:(1)According to the actual operation conditions of the turbine,nine working conditions of the minimum head,rated head and maximum head are selected under 40%,70% and 100% loads respectively.In each condition,the internal flow field and fluid-structure interaction analysis of the turbine are carried out.(2)According to the design parameters of the turbine,each components of the turbine are modeled by UG software and meshed in ANSYS software.(3)The standard k-? turbulence model is used to calculate the steady flow of various working conditions,and then the internal flow characteristics of the turbine under different head and load conditions are analyzed.(4)Based on the steady flow calculation results,the fluid-structure interaction characteristics of the turbine runner are calculated and analyzed by ANSYS software.(5)In order to better reflect the actual internal flow of the turbine under the actual operating conditions,the transient calculation of the turbine is carried out.The maximum total deformation,stress and strain of the runner are analyzed in detail,which provides a reference for predicting the crack location of the runner blades.The main results of the research are as follows:(1)According to the steady calculation,the results show that the flow internal the spiral casing and draft tube is relatively uniform,and there is a low pressure zone near the inlet of the back of the runner blades,where cavitation are prone to occur.(2)Through the fluid-structure interaction calculation,the sixth-order vibration frequency of the turbine is obtained,and comparing with self-vibration frequency,it can be seen that resonance phenomenon does not occur in the key parts of the turbine,which shows that the structural design of the turbine's overcurrent components is relatively reliable.Analysis of vibration modes of runner shows that the vibration form of runner is mainly manifested by the slight vibration deformation of the runner in the left and right direction of the runner,and in the higher mode,the vibration form is mainly manifested by the overall distortion of the whole runner.And the runner is gradually changed from a circular to an oblate shape.(3)Through transient calculations,the total deformation,equivalent strain and equivalent stress of the turbine runner under the condition of 40% load at the minimum head are analyzed in detail.It indicates that deformation and fracture are easily occurred at the connection position between runner blade and upper crown and lower ring.This is the same as the fracture location of the runner in the hydropower stations. |
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