Abstract:In order to study the internal flow characteristics and stress characteristics of pump turbines with diverging blades in different operating conditions under the small opening, with the hydraulic model of a pumped-storage power station with shunt blade pump turbine was taken as the analysis object. CFD numerical simulation method was used, the SST k-ω calculation model was adopted. The internal flow characteristics of the turbine, brake and reverse pump at 7.5° opening were numerically simulated, The pressure pulsation characteristics and axial force distribution of typical monitoring points inside the unit under different working conditions were analyzed. The results indicate that the internal flow characteristics of a pump turbine with shunt blades can be well simulated and analyzed by CFD numerical calculation. Under braking and reverse pump conditions, there is obvious unstable flow in the runner flow passage. Secondary flow and eddy structure fill the runner and cause flow congestion. The distributor blade can make the runner′s outlet speed more uniform; after the unit′s load rejection operation enters the braking condition, the axial force on the runner obviously increases, accompanied by negative value, and the fluctuation range is larger; the existence of the distributor blade can prevent the negative pressure in the runner area and help to reduce the strength of the vortex structure.