AUTHOR=Zhang Xiaowen , Tang Fangping , Liu Chao , Shi Lijian , Liu Haiyu , Sun Zhuangzhuang , Hu Wenzhu 

TITLE=Numerical Simulation of Transient Characteristics of Start-Up Transition Process of Large Vertical Siphon Axial Flow Pump Station

JOURNAL=Frontiers in Energy Research

VOLUME=Volume 9 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/energy-research/articles/10.3389/fenrg.2021.706975

DOI=10.3389/fenrg.2021.706975

ISSN=2296-598X

ABSTRACT=In order to explore the transient characteristics of the large-scale vertical siphon axial flow pumping station during the start-up and exhaust process, numerical simulations were carried out on the start-up process of the axial flow pumping station under the two starting modes of pre-opening the vacuum breaking valve and keeping the vacuum breaking valve closed. The calculation results show that during the start-up phase of the unit, the flow separation phenomenon of the impeller channel of the pump device with the vacuum breaking valve closed is serious, the large-scale vortex in the guide vane blocks the flow channel, and the instantaneous impact on the blade surface is strong. The flow field of the pump device with the pre-opened vacuum breaking valve is significantly less affected by the instantaneous impact characteristics during pump startup. The range of the high-entropy production area in the impeller channel is reduced, and the duration of the high-entropy production area is significantly shortened. The instantaneous impact is weak. Under the two starting modes, the internal flow field of the pump device is similar in the evolutionary law. The unstable flow phenomenon of the pump device is most prominent in the weir flow stage. The maximum instantaneous impact on the blade surface also mainly occurs in the weir flow stage. A very small part of the remaining gas in the siphon formation stage is difficult to discharge and takes a long time. The external characteristic parameters of the pump device after exhausting and entering a stable operation state are in good agreement with the test results. Compared with the starting method in which the vacuum breaking valve is kept closed, the method of pre-opening the vacuum breaking valve reduces the maximum starting head by 20% and the exhaust time by 43%. Pre-opening the vacuum break valve to start effectively avoids the system instability caused by the pump device during the start-up and exhaust process.