Simulation of the simultaneous load rejection processes of two parallel pump turbines using a 1D–3D approach

Abstract

A typical design scheme for pumped storage hydropower plants (PSPs) involves two or more pump turbines sharing one hydraulic and one electric unit. Load rejection is possible for a single pump turbine. It is also possible for multiple pump turbines to reject their loads simultaneously. The aim of this study is to simulate simultaneous load-rejection scenarios in PSPs using a one- and three-dimensional (1D–3D) coupling method. Here, a 1D method of characteristics (MOC) is applied to the pipeline modeling and 3D computational fluid dynamics (CFD) is applied to the turbine modeling. First, scenarios in which a pump turbine rejects its load with guide vanes stalled (or closed in 3 s) are simulated by using the 1D–3D coupling method. A comparison between the simulated results with 1D simulation and experimental results validates the coupling method. Simultaneous load rejection of two pump turbines is simulated in which only one pump turbine is modeled using 3D software. The simulated flow and head of the turbine are exchanged with the 1D pipeline model at two turbine-pipeline interfaces. Computational resources can be saved in this manner as other pump turbines are not modeled. A comparison with the 1D simulation indicates that the simplified 1D and 3D coupling methods are capable of effectively simulating the transient processes of PSPs with multiple pump turbines.