523 / 2024-06-29 11:03:03

Artical—Hydraulic characteristics of inlet flow of plunging dropshaft

Pumped storage power plant,Plunging dropshaft,Orifice,Discharge capacity,Flow regime

Subtheme 1: Water-related Hazard and Risk Reduction > Topic 6: Safety Risk Prevention and Control of Water Engineering

Pumped storage power plants are increasingly being constructed due to their critical role in carbon reduction. These plants often utilize plunging dropshaft spillway tunnels, known for their high heads and large discharges. However, research on these dropshafts is limited. This study conducted physical model tests to observe the flow of two types of shaft inlets: sharp-crested and bell-mouth-shaped weirs. The inlets featured multiple middle piers arranged circumferentially, forming numerous discharge orifices. Jets from these orifices impacted each other, converged, and dropped to the shaft bottom, with splashed water filling cavities between adjacent jets. Two flow regimes were identified based on cavity filling: fully filled cavities, which could cause pressure oscillation due to lack of ventilation, and partly filled cavities, which allowed air ventilation and were thus preferable. Experimental results indicated that sharp-crested weir inlets often led to drowned cavities, whereas bell-mouth-shaped inlets allowed better ventilation. Further research on bell-mouth-shaped inlets using numerical simulation explored flow regimes and discharge capacity. Variables such as orifice inlet width, outlet width, and weir head were considered. A formula to estimate the discharge capacity of bell-mouth-shaped inlets was developed from the simulation results, providing valuable insights for practical engineering design. This research enhances the understanding of hydraulic characteristics in dropshaft spillways, aiding in the efficient design of pumped storage power plants.