Flow Characteristics of Pump Turbine in Four Operating Quadrants: Computational Fluid Dynamics Simulation and Particle Imaging Velocimetry Measurement

Owing to the need for power grid peak regulation and frequency regulation, the pumped storage unit has to undergo frequent working condition conversion, and the pump turbine runs across the four quadrants of the full characteristics during the transition. This study used the full flow numerical simulation and particle imaging velocimetry test to examine the internal flow characteristics of three guide vane openings (GVO). Consequently, the evolution law of the internal flow pattern of the pump turbine was obtained. According to our results, in the high-efficiency areas of the turbine and the pump, the runner and guide vane areas flowed steadily, whereas, under other unsteady conditions, there was a vortex structure between the runner area and the vane area. Except for the pump-braking mode, all the most unstable flow areas appeared in the vaneless space. The flow in the runner channel was most unstable in pump-braking mode. Finally, we obtained test images of different operating points in the four-quadrant operating area as well as vortex motion trends.