Analysis of Transient Force Performances of Pump-Turbine during Stop Process in Pump Mode

The stop process occurs frequently for pump turbine due to the requirement of switching from pump mode to turbine mode. During stop process, the operating parameters such as the axial thrust, radial thrust and torque of the runner change rapidly, causing vibration of runner. In some cases, the rotating part can be lifted. In this paper, the unbalanced force acting on a pump-turbine during stop process in pump mode was studied using numerical simulation method. The CFD analysis was based on Reynolds averaged equation and the SST model was used to predict the transient flow characteristics. The clearance flow was also taken into consideration. Results show that the axial thrust was in opposite direction of gravity and changed with the variation of the head and torque. The axial thrust reached the maximum value in no-load condition.