Yonggang Lu, Xianliang Li, Chuanbao Yi, Qingchang Meng, Alexandre Presas
Under pump startup conditions, rapid parameter fluctuations in pump-turbines lead to unstable flow and significant pressure pulsations, which compromise power plant safety. This study performs numerical simulations of the transient flow field during the startup process of a mixed-flow pump-turbine within a pumped storage power station. Analyses were carried out at discrete guide vane opening (GVO) positions. The main conclusions are as follows: Entropy production analysis indicates that the total entropy generation decreases nonlinearly as the guide vane opening increases. Pressure pulsation in the runner synchronizes with changes in guide vane opening, and pulsation intensity increases in the bladeless area. Both fast Fourier transform (FFT) and short-time Fourier transform (STFT) analysis reveal that the predominant frequency of pressure fluctuations across all regions is the blade passing frequency (5.5 Hz) and its harmonics, attributed to rotor–stator interaction.