| With the rapid development of China’s economic construction, electric capacity keeps increasing. To solve the problem of peak regulation for the electrical network, the development of large pumped storage plant is an effective way to enhance the ability to regulate the power system. The inlet/outlet is an important part of water conveyance system for pumped storage plant. Inlet and outlet are one, it is called inlet when the water flows into orifices, while it is called outlet when the water flows out of orifices, which contains a complex two-direction flow. The inlet/outlet adjusts incoming flow from the tunnel to meet the velocity requirements of trash rack in outflow condition, and collects the water from the reservoir basin into the tunnel without harmful circulation or vortex in inflow condition. The inlet/outlet can be categorized into two basic types, lateral inlet/outlet and vertical pipe inlet/outlet. The direction of flow in the lateral inlet/outlet is nearly horizontal and does not involve a dramatic transformation, while the flow in the vertical pipe inlet/outlet with water delivery conduit perpendicularly linking to the reservoir is subjected to a sharp directional change of two 90° turnings.The inlet/outlet is the throat for pumped storage plant and controls the hydraulic conditions of inflow and outflow, its design relates directly to the safety and economic benefits of the power station. However, the current study on two-direction flow characteristics of inlet/outlet is still inadequate. Especially for the vertical pipe inlet/outlet that has been closely concerned in recent years, the study of which is generally specific project based, and mainly focuses on the hydraulic characteristics of flow at the diversion orifices, which lacks a general study of hydraulic characteristics for the complete inlet/outlet. For the lateral inlet/outlet, some research papers have been published, however, most of them focus on single inlet/outlet, it still lacks a flow pattern understanding of multi-inlet/outlet for large pumped storage plant.This paper systemically investigates two-direction flow characteristics of lateral inlet/outlet and vertical pipe inlet/outlet by model test and numerical simulation.(1) The two-direction flow characteristics of lateral inlet/outlet are undertaken a comprehensive study. With the background of Fengning pumped storage plant which contains six lateral inlets/outlets, the hydraulic characteristics such as circulation and vortex, head loss, and velocity distribution of diversion orifices are studied by model test and numerical simulation. The harmful circulation in the open channel in front of the intakes is successfully predicted and optimized by numerical simulation, meanwhile the general optimal thought and method are proposed. Feasible optimization schemes are put forward for the harmful vortex. The velocity distribution law of diversion orifices under different conditions is analyzed. The importance of adjustment section to the velocity distribution of diversion orifices is explored.(2) The two-direction flow characteristics of vertical pipe inlet/outlet are undertaken a comprehensive study. Firstly special model tests of the internal flow fields in the vertical pipe inlet/outlet are conducted to clear the internal flow fields of the complete inlet/outlet. Two sets of the models with different scales were designed respectively for ADV measurement and PIV measurement. The flow fields in the diversion orifices and reservoir are revealed by the ADV experiment, while the flow fields in the bend and diffuser are revealed by the PIV experiment. Secondly with the background of Yimeng pumped storage plant, the laws of flow motion in the complete vertical pipe inlet/outlet are studied using Finite Point Method, moreover, the impacts of the bend, the straight pipe, the number of diversion orifices and operation modes on hydraulic characteristics are analyzed. |
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