Author(s): Sorin-Ioan Lupa; Silviu Muntean; George Abdul-Nour

Linked Author(s):

Keywords: Water hammer; Load rejection; Francis turbine; Transient regimes; Hydropower plant

Abstract: The refurbishment of the hydropower plant aims to upgrade the performance, in particular on the availability and safety of the units. The transient regimes (e.g. start-up procedure, load rejection, speed-no-load, and so on) shorten the lifetime, raise the maintenance requirement and cause a loss of energy production. Therefore, the objective of this study is the analysis of the temporal interaction between the factors during the load rejection of the Francis turbines. The approach aims to identify transient hydrodynamic phenomena, especially in the framework of operating hydropower units equipped with Francis turbines as main regulating factor for the electrical grid. The investigations focus on evaluating the maximum pressure generated in the hydraulic pathway and comparing them with the admissible pressure value. Thus, the influence of certain physical factors identified in the flow passing through the turbine operated in transient regimes is explored. Also, the effect of some operating parameters of the hydropower plant on water hammer generation was examined. The investigation is based on the analysis of the experimental data connected with the analytical calculation of the maximum overpressure and a numerical simulation of the temporal interaction between the factors. The phenomena associated with the emergency shutdown (load rejection) of the Francis turbine from different wicket gate openings (e.g. 100%, 75%, 50% and 25%WG) considering the same wicket gate closing slope are analysed. The conclusions are drawn in the last section together with a few recommendations to reduce the overpressure with a direct impact on the required maintenance, lifetime of the hydropower unit and the safe operation of the equipment.

DOI: https://doi.org/10.1088/1755-1315/1483/1/012014

Year: 2023