期刊名称：IOP Conference Series: Earth and Environmental Science
印刷版ISSN：1755-1307
电子版ISSN：1755-1315
出版年度：2019
卷号：240
期号：2
页码：1-10
DOI：10.1088/1755-1315/240/2/022029
出版社：IOP Publishing
摘要：The pressure fluctuations in draft tube causes serious vibration and instability, which may affect the safe operation of turbines. In this paper, the pressure fluctuation of hydraulic turbine is studied by means of model test. Two model turbines with specific speed NQE0 of 0.1221 and 0.1178 are selected for experimental research, and pressure fluctuation measurement and vortex observation are carried out on the universal hydraulic machinery test stand under typical part-load and overload operating conditions. The influence of Reynolds number and Thoma number on the draft tube vortex was verified by adjusting the test head HM and tail water pressure pDT on the model test stand. The high-speed photography technique was applied to observe the vortex in the draft tube, meanwhile, the pressure fluctuation signal of the vortex was acquired and analysed. The peak-to-peak amplitude and the frequency of the pressure fluctuation are analysed and compared with the vortex zone morphology. The results show that, 1) the influence of Reynolds number on pressure fluctuation can generally be neglected in the range of Reynolds number Re>4×106; 2) pressure fluctuation may decrease with the Thoma number before critical cavitation in special overload conditions, indicating that the impact of cavitation on fluctuation is related to the shape of vortex rope; 3) resonance frequency is obtained at special part-load point, the resonant condition should be confirmed accurately due to the risk of system resonance.
