Can a low-head pumped hydrostorage unit operate in the hump region?

The pump mode of the low-head pumped hydrostorage unit (pump-turbine) may operate in the hump region under extreme conditions due to the influence of water level variation, and the resulting energy conversion instability will seriously threaten the safety of the unit.

How much energy does a guide vane hump lose?

Meanwhile, the guide vane cascade demonstrates an energy loss of 42.62 %, slightly exceeding that of the impeller. Therefore, it is imperative to consider the energy losses in both the impeller and the guide vane cascade when investigating the beginning of the hump.

Why does a pump turbine hump?

Particularly, when pump turbine operates under part load in pump mode, the presence of various unstable flow structures will trigger the formation of the hump region on the performance curve, which will result in notable vibration and noise, posing a critical risk to the safe and stable operation of the unit [11, 12].

Does a pump turbine have a hump region?

By utilizing particle image velocimetry (PIV) measuring equipment, Xue et al. conducted an experimental study on the rotating stall of a pump turbine in pump mode and demonstrated that the rotating stall in the guide vane region was not a sufficient condition for the occurrence of the hump region.

Does hump instability occur at 0.80 qdes?

Meanwhile, 0.80 QDes is around the beginning stages of hump instability. Hence, the follow-up study aims to investigate the mechanism of flow structures within the impeller at 0.80 QDes.

Can hump instability be captured by numerical simulation?

In brief, more flow details can be captured through numerical simulation after considering the compressibility of water at the beginning of the hump instability (0.80 QDes), and the results are closer to the experimental values than without considering the compressibility.