Flow-Induced Vibration Analysis Of Pelton Turbine

In normal operation of Pelton turbine,problems are highlighted that structural vibration can be caused by the jet flow,part of the bucket surface are damaged,even the whole buckets can break off,which in turn impact the safety and stability of the turbine operation.At present,the study of the mechanics performance of Pelton turbine runner only stay at the stage of choosing a transient to analyze in static way.Based on previous studies,with improved loading method of finite element analysis,this paper try to study the structure dynamics of Pelton turbine’s runner.Utilizing Static Structural module from Ansys Workbench to make static analysis of runner structure,the distributed rules of runner structure’s displacement and stress under three working states-starting,rated and runaway,can be obtained.Through the analysis of Pelton turbine in free state,constrained state and pre-stressed state,separately,the static frequency,dynamic frequency and their corresponding vibration mode can be acquired.The results show that the maximum equivalent stress is observed at the blades’ root.The turbine’ s low-frequency mode shape mainly consists of contortion and swing of blades,which is the key dynamical parameters in analyzing stress distribution of the dynamical stress for the blades.In this paper,CJA475-W-83 Pelton turbine runner is the research object.It includes runner designing,3D modeling,fluid analysis,static analysis and the study of dynamic characteristics of Pelton runner.The main issues of this paper are as follows:(1)According to fluid dynamics theory,use Ansys Workbench software"Fluent" to establish the Turbine Flow Field-D transient analysis model,which consider mixing air and water effects.The law of flow pattern and pressure distribution were obtained in the last.And the pressure will be the load of static analysis.(2)Using unidirectional flow-solid coupling mode,extract flow field analysis results as a runner loads of static analysis.Using Ansys Workbench platform static structural,under three states of starting,rated and runaway,the placement and stress distribution of runners can be obtained.Hereafter,it provide stress for modal analysis under different conditions.(3)Through the analysis to the pelton of the free mode,the constrained mode and the pre-stressed mode,the static frequency,dynamic frequency and their corresponding vibration mode can be calculated.By analyzing the frequency,we get the natural frequency domain of runner structure;by analyzing vibration mode,vibration law was found;at the same time,this paper also explore the effects of wheel speed and fluid on the impact of pelton modal;combined operating conditions,we can analyze the possibility of structural resonances.This paper simulates the hydraulic characteristics and structural characteristics of the Pelton turbine during the transition process,and analyzes the multi-nozzle water bucket turbine.The conclusion can help to guide the design and operation of the turbine runner and have reference value for the actual project.