2018
Yang, Jun; Pavesi, Giorgio; Liu, Xiaohua; Xie, Tian; Liu, Jun
Unsteady flow characteristics regarding hump instability in the first stage of a multistage pump-turbine in pump mode Journal Article
In: Renewable Energy, vol. 127, pp. 377-385, 2018, ISSN: 09601481.
Abstract | Links | BibTeX | Tags: Hump instability, Pump as Turbine, Pump Mode, Return channel, Unsteady Flow
@article{Yang2018b,
title = {Unsteady flow characteristics regarding hump instability in the first stage of a multistage pump-turbine in pump mode},
author = {Jun Yang and Giorgio Pavesi and Xiaohua Liu and Tian Xie and Jun Liu},
url = {https://doi.org/10.1016/j.renene.2018.04.069 https://linkinghub.elsevier.com/retrieve/pii/S0960148118304774},
doi = {10.1016/j.renene.2018.04.069},
issn = {09601481},
year = {2018},
date = {2018-01-01},
journal = {Renewable Energy},
volume = {127},
pages = {377-385},
publisher = {Elsevier Ltd},
abstract = {This article reports the fluid-dynamical analyses of unsteady flow in the first stage of a multistage pump-turbine where hump instability occurs. This stage can be seen as a centrifugal pump with multistage guide vanes in pump mode. Experimental and numerical approaches are adopted to contribute the understanding of the highly complex flow regime inner the test pump. In the experimental test, both dynamic pressure measurement and flow visualization techniques are adopted. A commercial code with detached eddy simulation (DES) model is used to compute the flow regime. The frequency analysis indicates that two unsteady flow patterns with a constant frequency occur in the hump instability region. The numerical and experimental unsteady flow fields are analysed to study the fluid-dynamical features of these unsteady patterns, in order to investigate the origin and reveal their contributions to the hump instability.},
keywords = {Hump instability, Pump as Turbine, Pump Mode, Return channel, Unsteady Flow},
pubstate = {published},
tppubtype = {article}
}
This article reports the fluid-dynamical analyses of unsteady flow in the first stage of a multistage pump-turbine where hump instability occurs. This stage can be seen as a centrifugal pump with multistage guide vanes in pump mode. Experimental and numerical approaches are adopted to contribute the understanding of the highly complex flow regime inner the test pump. In the experimental test, both dynamic pressure measurement and flow visualization techniques are adopted. A commercial code with detached eddy simulation (DES) model is used to compute the flow regime. The frequency analysis indicates that two unsteady flow patterns with a constant frequency occur in the hump instability region. The numerical and experimental unsteady flow fields are analysed to study the fluid-dynamical features of these unsteady patterns, in order to investigate the origin and reveal their contributions to the hump instability.
2016
Yang, Jun; Yuan, Shouqi; Pavesi, Giorgio; Li, Chun; Ye, Zhou; Shouqi, Yuan
Study of Hump Instability Phenomena in Pump Turbine at Large Partial Flow Conditions on Pump Mode Journal Article
In: Journal of Mechanical Engineering, vol. 52, iss. 24, pp. 170, 2016, ISSN: 0577-6686.
Abstract | Links | BibTeX | Tags: Francis-type Reversible Turbine, Hump instability, large partial flow conditions, Pump, Pump, Pump as Turbine, Pump Mode, unsteady flow pattern
@article{Yang2016,
title = {Study of Hump Instability Phenomena in Pump Turbine at Large Partial Flow Conditions on Pump Mode},
author = {Jun Yang and Shouqi Yuan and Giorgio Pavesi and Chun Li and Zhou Ye and Yuan Shouqi},
url = {http://www.cjmenet.com.cn/Jwk_jxgcxb/CN/10.3901/JME.2016.24.170},
doi = {10.3901/JME.2016.24.170},
issn = {0577-6686},
year = {2016},
date = {2016-01-01},
urldate = {2016-01-01},
journal = {Journal of Mechanical Engineering},
volume = {52},
issue = {24},
pages = {170},
abstract = {For middle- and high-specific speed pump turbines, the hump instability appearing at large partial flow conditions seriously restricts its stable operation range. These phenomena relate closely to the inner unsteady flow in pump turbine. We investigate the characterization of pressure fluctuation and the mechanism of unsteady flow by an experimental and numerical study of the unsteady flow occurring among the adjustable blades. For pump working at either full or part load conditions, two kinds of periodic pressure pulsations in the diffuser vane have been observed and analyzed. A hump instability appears only when the actual flow rate of head curve is 0.45-0.75 times of the designed value, and our frequency analysis further shows that its appearance is closely related to the two above pressure fluctuations.},
keywords = {Francis-type Reversible Turbine, Hump instability, large partial flow conditions, Pump, Pump, Pump as Turbine, Pump Mode, unsteady flow pattern},
pubstate = {published},
tppubtype = {article}
}
For middle- and high-specific speed pump turbines, the hump instability appearing at large partial flow conditions seriously restricts its stable operation range. These phenomena relate closely to the inner unsteady flow in pump turbine. We investigate the characterization of pressure fluctuation and the mechanism of unsteady flow by an experimental and numerical study of the unsteady flow occurring among the adjustable blades. For pump working at either full or part load conditions, two kinds of periodic pressure pulsations in the diffuser vane have been observed and analyzed. A hump instability appears only when the actual flow rate of head curve is 0.45-0.75 times of the designed value, and our frequency analysis further shows that its appearance is closely related to the two above pressure fluctuations.
2015
Pavesi, Giorgio; Yang, Jun; Cavazzini, Giovanna; Ardizzon, Guido
Experimental analysis of instability phenomena in a high-head reversible pump-turbine at large partial flow condition Proceedings Article
In: 11th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2015, pp. 1-2, euroturbo.eu, 2015, ISSN: 24104833.
Abstract | Links | BibTeX | Tags: Flow instability, Francis Turbine, Francis-type Reversible Turbine, Hump instability, PAT, Pump as Turbine
@inproceedings{pop00010,
title = {Experimental analysis of instability phenomena in a high-head reversible pump-turbine at large partial flow condition},
author = {Giorgio Pavesi and Jun Yang and Giovanna Cavazzini and Guido Ardizzon},
url = {http://www.euroturbo.eu/paper/ETC2015-060.pdf},
issn = {24104833},
year = {2015},
date = {2015-01-01},
urldate = {2015-01-01},
booktitle = {11th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2015},
pages = {1-2},
publisher = {euroturbo.eu},
abstract = {Growing environmental concerns, and the need for better power balancing and frequency control have increased attention in renewable energy sources, such as, the reversible pump-turbine which can provide both power generation and energy storage. Pump-turbine operation along the hump-shaped curve can lead to unusual increases in water pressure pulsations, which lead to machine vibrations. Measurements of wall pressure in the stators were performed together with high-speed flow visualizations. Starting from the best efficiency point (BEP) and by decreasing the flowrate, a significant increase of the pressure fluctuations was observed mainly in the wicket gates channels. The analyses in frequency and time-frequency domains showed a rise of low frequency components. High-speed movies revealed a quite uniform flow pattern in the guide vanes channels at the normal operating range, whereas, the flow was highly disturbed by rotating stall passage at part load. The situation was more critical in the dump flow rate range, where backflow and vortices in the guide vanes channels developed during the stall cell passage.},
keywords = {Flow instability, Francis Turbine, Francis-type Reversible Turbine, Hump instability, PAT, Pump as Turbine},
pubstate = {published},
tppubtype = {inproceedings}
}
Growing environmental concerns, and the need for better power balancing and frequency control have increased attention in renewable energy sources, such as, the reversible pump-turbine which can provide both power generation and energy storage. Pump-turbine operation along the hump-shaped curve can lead to unusual increases in water pressure pulsations, which lead to machine vibrations. Measurements of wall pressure in the stators were performed together with high-speed flow visualizations. Starting from the best efficiency point (BEP) and by decreasing the flowrate, a significant increase of the pressure fluctuations was observed mainly in the wicket gates channels. The analyses in frequency and time-frequency domains showed a rise of low frequency components. High-speed movies revealed a quite uniform flow pattern in the guide vanes channels at the normal operating range, whereas, the flow was highly disturbed by rotating stall passage at part load. The situation was more critical in the dump flow rate range, where backflow and vortices in the guide vanes channels developed during the stall cell passage.
