Investigate the full characteristic of a centrifugal pump-as-turbine (PAT) in turbine and reverse pump modes

Large centrifugal pumps can generate electricity in reverse, reducing the power supply pressure of grid. However, S region may occurs during operation and regulation pump as a steam turbine (PAT). The cause unstable unit startup, not only causing hydraulic system oscillation, but also accompanied by strong vibration noise. Understanding characteristic curve is great significance for improving stability efficiency. Previously, main research object area was small generator units. This article conducted unsteady numerical simulation experimental on large pump. Analysed internal flow rate, blade load, entropy generation, pulsation under three special operating conditions: optimal condition, runaway braking condition region. In addition, comparative analysis pairs mode reverse mode, with opposite direction, similar same speed. Research has found that pumps, chaos mainly impeller section, maximum stationary section.