Investigation on Synchronous and Asynchronous Characteristics of Pressure Fluctuations towards Precessing Vortex Rope in Francis Turbine Draft Tube

被引：0
|
作者：
Sun L. [1 ]
Guo P. [1 ]
Luo X. [1 ]
机构：
[1] State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi'an University of Technology, Xi'an
来源：
Nongye Jixie Xuebao/Transactions of the Chinese Society for Agricultural Machinery | 2019年 / 50卷 / 09期
关键词：
Asynchronous components; Decomposition for pressure fluctuation; Francis turbine; Precessing vortex rope in draft tube; Synchronous components;
D O I：
10.6041/j.issn.1000-1298.2019.09.014
中图分类号：
学科分类号：
摘要：
Precessing vortex rope (PVR) in Francis turbine draft tube is an unsteady swirling flow under a given partial load operating conditions and characterized by high-amplitude pressure fluctuation, and the pressure fluctuation excited by PVR can cause several directed and adverse effects on the operating stability or even fatigue damage. Numerical solution with SST k-ω turbulent model and experimental test were respectively carried out to investigate the internal flowing of draft tube towards a model Francis turbine operating at 42.35% of rated power. An excellent agreement between numerical and experimental results of pressure fluctuation amplitude and frequency was obtained with corresponding errors of 2.70% and 2.62%, respectively. The monitored pressure pulsates periodically at low frequency of 0.25 time of the runner revolution frequency, the monitoring positions travelled over by the PVR structure captured a minimum pressure value, and higher pressure amplitude compared with the rest regions due to the movement of vortex structure. In order to further clarify the complex flow features and dynamic characteristics towards the PVR, the pressure signals measured was decomposed into the synchronous and asynchronous components. Relative to the synchronous component, the decomposed asynchronous component remained the same frequency as the frequency of vortex rope evolution and obtained an absolute dominance of pressure fluctuation amplitude. On the contrary, the dominant frequency of synchronous component was changed with lower pressure amplitude. The analysis indicated that the contribution of the non-synchronous component to the formation of the vortex rope was greater than that of the synchronous component. At different elevations of draft tube cone, the quantitative analysis to the amplitudes showed that the asynchronous component held leading status, the amplitude of asynchronous component was increased initially and then decreased along the flow direction, while the synchronous component amplitude kept increased. © 2019, Chinese Society of Agricultural Machinery. All right reserved.
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页码：122 / 129
页数：7
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