CFD Investigation of the Hydraulic Short-Circuit Mode in the FMHL/FMHL plus Pumped Storage Power Plant

The flexibility of the FMHL+ pumped storage power plants can be improved by extending the hydraulic short-circuit operating mode. CFD simulations of the flow in three bifurcations are performed to calculate the head losses and to investigate the flow topology in the pipes. A specific attention is paid to the influence of the curvature correction that has been developed for two-equation RANS turbulence models. For the T-junction considered, the activation of the curvature correction influences the head losses whereas for the two Y-junctions computed, no effect is observed. By comparing with the Y-junctions, the T-junction leads to higher head losses and helicity in the pipes downstream of the bifurcation. Compared to the current the intragroup hydraulic short circuit operation permitted, the intergroup and interplant hydraulic short circuit mode should provide better performances with possible gains until of -55% in head losses and -94% in helicity upstream of the turbines.