Numerical Simulation Of "S" Characteristic Zone Of Pump Turbine

Pump turbine is one of the core components of pumped storage power station.It can be used as a hydraulic turbine and pump operation.However,in the operation of the turbine,the "S" shape curve appears in the full characteristic curve.In the "S" shaped region,the flow in the pump turbine is complex,the operation is very unstable,which will cause the problem of the grid connected system,and has a serious impact on the normal operation of the power station.In order to study the instability of pump turbines as turbines,based on the similarity theory,a model of pump turbine machine as the research object,select the "S" characteristics in the first quadrant condition for numerical simulation,study the development of the internal flow field,and provide some reference suggestions for the stable operation of the pump turbine prototype.The main contents of this paper are as follows:(1)The characteristics and research progress of water pump "S" are reviewed.(2)Using ANSYS CFD preprocessor ICEM software to divide the different parts of the model.(3)In this paper,the numerical simulation of the whole flow path of the pump water turbine is carried out.The basic theory and calculation method of the numerical simulation are used to select the SST turbulence model.The first order upwind scheme is used to separate the control equations.The SIMPLEC algorithm is used to calculate the flow field.The FLUENT software of ANSYS CFD was used to simulate the hydraulic turbine condition,the braking zone and the zero flow condition of the pump turbine.(4)The CFD-POST software is used to post-process the calculation results to generate the pressure distribution and flow chart of each flow component in different working conditions.By comparing the flow field under different working conditions,the running rules of the pump are obtained: when the opening degree is small,it is not affected by the "S" characteristic,and it can run stably;with the increase of the opening degree,it will be affected by the "S" characteristic,when it is running in the "S" feature area,the flow channel filled with a large number of,resulting in unstable operation.Finally,some suggestions are put forward for the stable operation of the pump turbine.