Numerical Simulation Study on Hydraulic Transients in Hydropower Station with Trigeminy Surge Tank

Abstract

A static and dynamic model for hydraulic transient calculation of three-throttled-orifice surge tank was established based on the basic equations of surge tank, by using structure matrix method (matrix analysis of structure?). Control conditions in an engineering practice were calculated by a simplified model and a three-throttled-orifice model respectively. The results indicate that the maximum pressure at the volute end, the maximum rising rate of unit speed and the water level extremum of the surge tank are basically identical by using these two models, but the minimum pressure at draft tube inlet is significantly different. The three-throttled-orifice model was found capable of calculate the flow between throttled orifices at constant state and the pressure behavior at draft tube inlet during the transition accurately. The selection of the resistance factor is discussed in the end, and it is proved that the resistance factor is allowed to have a certain tolerance in the transition calculation, which will not obviously affect the maximum pressure at draft tube inlet and water level extremum of the surge tank. This research can provide reliable reference for the transient calculation of three-throttled-orifice surge tank in similar engineering practice.