Research On The Start-up Transient Process Of Reversible Pump Turbine

Pumped storage power stations are frequently transformed in actual production,so that the whole turbine unit mainly bear the load adjustment of “cutting peaks and filling valleys” and takes into account the phase modulation and frequency modulation for the power grid.At present,China is making great efforts to develop pumped storage power stations.It is of great practical significance for the research on the stability of the unit's rapid start-up and grid connected transient process.In this paper,the reversible pump-turbine in a domestic pumped storage power station is studied,the relationship between rotational speed and time in start-up process of the unit is discussed,and three-dimensional numerical simulation of the whole flow field of the reversible pump-turbine starting transition process is carried out.In order to study the internal transient flow characteristics of the reversible pump-turbine under different starting modes,the user-defined function(UDF)in fluent is used to control the movement of the active guide vanes in the starting process,and based on the dynamic and sliding grid method,Combined with the speed change of the iterative computer group in the internal flow field of the reversible pump-turbine in the start-up process,the realizable k-? turbulence model was used to simulate the synchronous opening and the asynchronous opening of the movable guide vane of the reversible pump-turbine.Through the numerical simulation of two start-up modes,the rotational speed of the runner is obtained and compared with the results after the theoretical study,the coincidence degree is higher,which indicates that the three-dimensional numerical simulation method can simulate the starting transition process of the reversible pump-turbine more accurately.By monitoring the pressure fluctuation signal in the river basin,a short time Fourier transform(STFT)is used to deal with the pressure signal,and the flow field pulsation characteristic is obtained.The characteristics of pressure fluctuation and dynamic instability in the flow field are studied by combining the internal flow characteristics of the two start-up modes.The results show that the instability of the reversible water pump turbine during start-up is mainly caused by the pressure pulsation in the runner.During the start-up process,the pressure pulsation in the flow channel is affected by the movement of the rotor and the movable guide vane in the wake of the trailing edge of the active guide vane.During the start-up process of the active guide vane,the trailing edge wake flow of the active guide vane affects the pressure pulsation.Instead of the synchronous guide vanes(MGV)open start-up process,because the active guide vane of the games in the double row cascade generated excitation,the excitation effect will produce a 200 Hz and 400 Hz in the flow of the pulse frequency,the flow channel within the high power,high amplitude of the frequency pulsation.