Abstract
Hydroelectric energy is an increasingly vital and effective renewable energy for modern society. The protective effect on the water hammer in the pipeline, the operational stability of the hydropower system, and the flow regime in the air-cushion surge chamber (ACSC) are three main problems during the design of the hydropower station with an ACSC. Comprehensively comparing the above issues between the horizontal and vertical ACSCs is meaningful. This study established the one-dimensional (1D) model based on the Method of Characteristics (MOC) under large load disturbances (LLD) and the rigid water column theory under small load disturbances (SLD). At the same time, the three-dimensional (3D) model was built based on the Volume of Fluid (VOF) to obtain a more detailed flow regime in the ACSC under the load acceptance condition. The results showed that the vertical ACSC was superior to the horizontal one for its large safe water depth, smaller maximum air pressure, and more stable flow under LLD. In contrast, the horizontal one was better than the vertical one for its extensive water area to calm the SLD during the transient process and smaller fluctuation of the surge under SLD. This study will provide a reference for a future project on selecting the structure of the ACSC.