The Suppression of Hump Instability inside a Pump Turbine in Pump Mode Using Water Injection Control

Abstract

The occurrence of hump instability in pump mode within a pump turbine poses a significant challenge to the safe and stable operation of Pumped Storage Power Plants (PSPP). To achieve more precise numerical simulations, this paper establishes a weakly compressible model of water based on the Tait equation. Using this model, it is discovered that the onset of hump instability is closely linked to an increase in hydraulic losses induced by stalled rotation within the diffuser. Then, a flow control approach employing water injection into the guide vanes of a pump turbine is proposed in order to suppress flow instabilities and optimize the hump region. The findings reveal that the water injection approach can mitigate hydraulic losses, suppress unstable structures, and diminish the pulsation amplitude within the diffuser, ultimately delaying the emergence of the hump region to lower flow mass conditions. This study is helpful in widening the range of the safe and stable operation of pump turbines in pump mode.

Research on the Internal Flow Difference between Peak and Valley Conditions of Water Jet Propulsion Pump during Working at Hump Region

“…Liu Yong [9] attributed the hump phenomenon in centrifugal pumps primarily to the reduction in impeller's functional capacity due to rotational stall, followed by the increased asymmetry of the flow and turbulence intensity within the volute, resulting in increased hydraulic losses. The theoretical head-flow curve of centrifugal pumps is more prone to exhibit humps, and the selection of an appropriate blade outlet angle and blade profile curvature helps to address the hump problem in pumps [10][11][12].…”