Abstract
The axial hydraulic thrust has great influence on the safety and stability of a pump turbine. A common way to balance hydraulic thrust is to install a pressure-balance pipe, and the change in pipe diameter is one of the important factors affecting axial hydraulic thrust. In this paper, the influence of the diameter changes in a pressure-balance pipe on axial hydraulic thrust of a pump turbine, plus the seal clearance flow, is studied and analyzed under three work conditions, i.e., 100%, 75%, and 50% loads. It is found that under 100% and 75% load conditions, the axial hydraulic thrust increases vertically with the increase in pipe diameter; whereas, under 50% load condition, the axial hydraulic thrust increases first and then decreases with the increase in pipe diameter. The results aim to give guidelines for the choice of pressure-balance pipe diameters and to control the axial hydraulic thrust of a pumped-storage power station, so that the hydraulic excitation force can be better matched with the hydraulic mechanism.
Highlights
The axial hydraulic thrust has great influence on the safety and stability of a pump turbine
The influence of the change in the diameter of the pressure-balance pipe on the axial hydraulic thrust is studied by numerical simulation of the pump turbine with the upper crown clearance, the lower ring clearance, and the pressure-balance pipe in a pumped-storage power station
The results show that when the diameter of the pressure-balance pipe changes, the resultant force of axial hydraulic thrust on the runner is mainly determined by the pressure distribution on the outer surface of the upper crown and lower ring
Summary
Due to the large-scale grid connection of intermittent renewable energy such as solar and wind energy in China, the peak shaving capacity of the power system is insufficient, and the pumped-storage unit satisfies this demand of the power system well, achieving a leap development [1]. Studying the optimal design of the pressure-balance pipe and its influence mechanism on the performance of the pump turbine can significantly improve the stability, the safety, and reliability of the pumped-storage power station operation. Considering that the main purpose of setting a pressure-balance pipe is to improve the axial hydraulic thrust of a pump turbine, a numerical model of the whole flow channel including a pressure-balance pipe is established for a pump turbine of a pumped-storage power station. The influence of the diameter changes and the position of the pressurebalance pipe on the leakage volume (efficiency) and axial hydraulic thrust is studied by CFD technology, so as to find out the influence of the pressure-balance pipe on the stability of the pump turbine, guiding the optimal design of the pump turbine
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