Study On Cavitation Characteristics Of The Pump-turbine Under Partial Load Condition

Pump-Turbine as a core part in pumped storage power station,it gradually transform to the high head,high speed and large capacitance.its stability problem has long been the concern of researchers.Most pump-turbine presently with high speed and head always start and stop with high frequency.In fact,the pump-turbine units always run in bad flow conditions,the internal flow changes more complex and special,so the research of the stability and reliability in pump-turbine is more urgent.According to the pump-turbine model test and the experience of operation in pumped storage power station,it can discover some problems such as vibration,noise,pressure pulsation,cavitation erosion and so on under off-design operating conditions.The occurrence of cavitation will depress the hydraulic performance of the unit,produce vibration and noise.In severe cases,its over-current components is easy to be damaged by cavitation,even shorten the operating life of the unit.To ensure the good cavitation performance has become the main aspect of the design and manufacture level on pump-turbine.Therefore,the research of cavitation plays an important role in ensuring the safe and stable operation of the unit to predict the occurrence regularity,put forward the corresponding improvement measures and determine the reasonable operation conditions.In order to explore the phenomenon and rules of cavitating flow in pump-turbine at pump mode,in this paper,a pump-turbine model in a pumped storage power station was selected as computational model,using the CFD method combined with the relevant experimental data.It mainly analyzes the vapor volume distribution and loading characteristic under different cavitation factors on the blade by unsteady pressure field calculation on the whole flow passage in pump-turbine.The major works and achievements are as following:(1)Build the numerical calculation model of whole passage field,then create calculating mesh of overflow region respectively,validate the grid independence,select the reasonable turbulence model,cavitation model and boundary conditions.finally,unsteady numerical simulation of the whole flow was performed using CFD simulation technology.(2)The whole flow passage of pump turbine has been simulated under different cavitation factors,the comparative analysis between simulation results and experimental data were carried out,then rationality of calculation model is verified.Detailed Analysis of pressure distribution,speed distribution and turbulent kinetic distribution in the runner-fixed guide blade region has been given.(3)The distribution law of the pressure and load on the blade and vapor volume in runner channel has carried on the selective analysis under different cavitation factors.