CFD Research on Francis Pump-Turbine Load Rejection Transient Under Pump Condition

Abstract

In the paper, three dimensional unsteady CFD numerical method is established to simulate load rejection transient of Francis pump-turbine in pump mode. First, pumped storage power station’s whole flow system geometric model including diversion tunnel, surge tank, penstock, pump turbine unit and tailrace tunnel has been built and subdivided with prism and tetrahedral mesh. Then, three dimensional unsteady CFD simulation begins from the original steady pump condition, with the Realizable k–ε turbulent model. Through numerical calculation, the variation regularity of unit rotate speed, flow rate, torque, axial thrust and static pressure of measuring points with time are revealed during the load rejection transient. By comparison with experimental data, the changing regularity of transient dynamic parameters can be verified and their differences in the detail also can be reflected. Simultaneously, the phenomenon of water hammer has been captured by recording time-varying static pressure of measuring points. Furthermore, flow configuration in the passage undergoes very complex and unsteady change during load rejection transient.

Load Rejection Transient Process Simulation of a Kaplan Turbine Model by Co-Adjusting Guide Vanes and Runner Blades

“…The internal flow of the Kaplan turbine calculated in this paper is an incompressible and turbulent flow with water as the flow media, and the energy conservation equation can be neglected due to the minimal heat exchange. According to the grid rotating motion, the governing equations described by the arbitrary Lagrangian Eulerian (ALE) method [35][36][37] is used to provide the grid motion velocity, and the continuity equation can be written as follows:…”