1. College of Water Resources and Hydropower Engineering, Hohai University, Nanjing, Jiangsu 210098, China; 2. Liaoning Water Conservancy and Hydropower Survey and Design Research Institute Co., Ltd., Shenyang, Liaoning 110006, China; 3. School of Agricultural Science and Engineering, Hohai University, Nanjing, Jiangsu 210098, China
Abstract:Aiming at the long-distance and high drop water conveyance project with the combination of pressurization and gravity gravity gravity flow in a head pump station, the mathematical model of the whole system hydraulic transition process is established based on the characteristic line method commonly used in transient flow calculation, and the whole process of pump shutdown water hammer is simulated. In order to solve the problem of negative pressure in the pipeline after power failure of water pump unit, the protection scheme of using air tank behind the pump is put forward, the parameters of air tank are optimized, and the better shape of air tank is determined; A high-level water tank is set at the highest point of the pipeline, and the gravity flow section behind the water tank adopts the mode of series connection of pressure reducing valve and regulating tank for energy dissipation. Under the condition of pump shutdown, in order to avoid empty leakage of the high-level water tank, it is necessary to close all pressure reducing valves. In order to prevent the booster water hammer generated by valve closing from exceeding the pipeline pressure bearing standard, resulting in pipe explosion accident, and considering the influence of water level fluctuation of each regulating tank, different valve closing schemes are selected for comparison. The calculation results show that the preferred volume of the air tank of the project is 15 m3, and the pressure reducing valve is closed in a straight line in 120 s after the pump is stopped. Since the regulating tank is set behind the pressure reducing valve, closing the valve successively and closing the valve at the same time has little impact on the results. The research conclusion provides a reference for the design and safe operation of similar water supply projects.