Numerical investigation on the transient gas–liquid flow in the rapid switching process of pump turbine

The frequent switching of pump mode and turbine the leads to transient phenomena. To ensure safe stable operation unit, a detailed study on exhaust pressurization process when unit switches from has been carried out. Based Shear Stress Transfer model (SST) k–ω turbulent model, numerical simulations are processed both in steady unsteady state. visualization results gas–liquid two phases distribution dynamic given, characteristic references each stage also characteristics torque, axial, radial force runner guide vane analyzed by combining short-time Fourier transform. show that main frequencies this blade passing frequency its harmonic frequency. This presents high amplitude band at all values, which may be caused entrainment centrifugal action free liquid surface.