Modeling and Surge Characteristics of Differential Surge Chamber in Hydropower Station during the Transient Process

Abstract The differential surge chamber (DSC) is an effective pressure reduction measure for hydropower stations, offering significant advantages in reducing surge amplitude and accelerating the attenuation of hydraulic fluctuations. However, most existing studies do not adequately consider the hydraulic interactions between different transient stages of the DSC, which limits their ability to capture surge characteristics. In this study, a transient model for the DSC was established, accounting for three critical stages (preoverflow, overflow, and postoverflow) and their hydraulic interactions. The surge characteristics of the DSC under load rejection and load acceptance conditions were revealed, and the impacts of DSC parameters on surge characteristics were identified. A principle for hydraulic design optimization of the DSC is also proposed. The results indicated that the maximum water level difference between the riser and the main tank occurred within the first cycle of water level fluctuation, posing a threat to the safety of the riser. When the riser overflowed, the water column height in the riser could exceed the water level in the main tank, thereby becoming the DSC’s highest water level. In addition, the surge characteristics of the DSC were influenced by the riser area, main tank area, riser elevation, and orifice area. As the riser, main tank, and orifice areas increased and the riser elevation decreased, the highest water level under load rejection decreased. Additionally, increases in the riser, main tank, and orifice areas led to an increase in the lowest water level under load acceptance conditions. Overall, the findings of this study provide guidance for the design and optimization of DSCs.