School of Energy Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
State Key Laboratory of Hydro-Power Equipment, Harbin Institute of Large Electrical Machinery, Harbin 150040, China
During the process of switching conditions in pump-turbine, unstable ﬂow would take place and seriously impact on the stability and safety. This paper deals with the guide vanes’ moving process in pump mode through unsteady numerical simulations. Dynamic mesh methodology is used for simulations in which GVO (Guide Vane Opening) from 9mm to 26mm. Simulation results approve that, there are many complex vortex structures and ﬂow blockages phenomena under small GVO condition. Through the mathematical method of Fast Fourier Transform (FFT) and Short-Time Fourier Transform (STFT), the dominant pressure ﬂuctuation frequencies are from runner blade passing frequency (BPF) and its harmonic frequency, as well as some other low frequencies are from unsteady ﬂow states. Furthermore, the ﬂow states are more unstable and complex under small guide vanes moving process. Compared with ﬁxed GVO position, the ﬂow states are more unstable and complex under guide vanes moving process, while the amplitude of main frequencies becomes higher.