2023
Zanetti, Giacomo; Cavazzini, Giovanna; Santolin, Alberto
Three-dimensional evolution of the flow unsteadiness in the S-shape of pump-turbines and its correlation with the runner geometry Journal Article
In: Journal of Energy Storage, vol. 57, iss. September 2022, pp. 106176, 2023, ISSN: 2352152X.
Abstract | Links | BibTeX | Tags: Interblade vortex, Pump as Turbine, Pumped-hydropower, Rotating Stall, S-shape
@article{Zanetti2023,
title = {Three-dimensional evolution of the flow unsteadiness in the S-shape of pump-turbines and its correlation with the runner geometry},
author = {Giacomo Zanetti and Giovanna Cavazzini and Alberto Santolin},
url = {https://doi.org/10.1016/j.est.2022.106176},
doi = {10.1016/j.est.2022.106176},
issn = {2352152X},
year = {2023},
date = {2023-01-01},
journal = {Journal of Energy Storage},
volume = {57},
issue = {September 2022},
pages = {106176},
publisher = {Elsevier Ltd},
abstract = {Pump-turbines (RTP) are the most common mechanical equipment adopted in pumped-hydro power plants and, for grid balancing purposes, are required to sharply switch from pumping to generating mode, and to extend their operative, jeopardizing not only the machine operability but also its life. New design approaches to avoid the onset of unstable behaviours are still far from being defined, and control strategies for accelerating start-up/shut-down procedures are still not effective since these are based on semi-empirical approaches, due to the lack of identification of precursors of the unstable behavior. In this paper, a numerical analysis of the unstable behavior of an RPT during the transition from partial load up to the turbine-brake area was carried out. The fluid-dynamics in different operating points (partial load, run-away condition, turbine brake) was deeply investigated, identifying the rotor-stator mechanisms causing the 3D evolution of the flow field leading to the development of the unstable behavior. Three evolution phases (inception, growth and consolidation) were identified and clearly correlated with the runner geometry and with the S-Shape of the RPT characteristic curve. Customized signal processing strategies were adopted for spectrally characterizing each phase so as to identify potential triggers for new monitoring and control strategies. Moreover, for the first time, a clear fluid-dynamic explanation of the empirical results found in literature on the influence of the runner geometry is provided.},
keywords = {Interblade vortex, Pump as Turbine, Pumped-hydropower, Rotating Stall, S-shape},
pubstate = {published},
tppubtype = {article}
}
Pump-turbines (RTP) are the most common mechanical equipment adopted in pumped-hydro power plants and, for grid balancing purposes, are required to sharply switch from pumping to generating mode, and to extend their operative, jeopardizing not only the machine operability but also its life. New design approaches to avoid the onset of unstable behaviours are still far from being defined, and control strategies for accelerating start-up/shut-down procedures are still not effective since these are based on semi-empirical approaches, due to the lack of identification of precursors of the unstable behavior. In this paper, a numerical analysis of the unstable behavior of an RPT during the transition from partial load up to the turbine-brake area was carried out. The fluid-dynamics in different operating points (partial load, run-away condition, turbine brake) was deeply investigated, identifying the rotor-stator mechanisms causing the 3D evolution of the flow field leading to the development of the unstable behavior. Three evolution phases (inception, growth and consolidation) were identified and clearly correlated with the runner geometry and with the S-Shape of the RPT characteristic curve. Customized signal processing strategies were adopted for spectrally characterizing each phase so as to identify potential triggers for new monitoring and control strategies. Moreover, for the first time, a clear fluid-dynamic explanation of the empirical results found in literature on the influence of the runner geometry is provided.
2015
Yang, Jun; Pavesi, Giorgio; Yuan, Shouqi; Cavazzini, Giovanna; Ardizzon, Guido
Experimental Characterization of a Pump–Turbine in Pump Mode at Hump Instability Region Journal Article
In: Journal of Fluids Engineering, vol. 137, iss. 5, pp. 051109, 2015, ISSN: 0098-2202, (<b>From Duplicate 2 (<i>Experimental Characterization of a Pump–Turbine in Pump Mode at Hump Instability Region</i> - Yang, Jun; Pavesi, Giorgio; Yuan, Shouqi; ...; Cavazzini, Giovanna; Ardizzon, Guido)<br/></b><br/><b>From Duplicate 8 (<i>Experimental characterization of a pump–turbine in pump mode at hump instability region</i> - Yang, J; Pavesi, G; Yuan, S; ...)<br/></b><br/>Query date: 2017-05-06).
Abstract | Links | BibTeX | Tags: Flow Visualization, high-speed, High-speed flow visualization, Hump-instability, hump-instability region, Pressure measurement, Pump, Pump as Turbine, Pump as Turbine, Rotating Stall, Turbine
@article{pop00008,
title = {Experimental Characterization of a Pump–Turbine in Pump Mode at Hump Instability Region},
author = {Jun Yang and Giorgio Pavesi and Shouqi Yuan and Giovanna Cavazzini and Guido Ardizzon},
url = {http://fluidsengineering.asmedigitalcollection.asme.org/article.aspx?doi=10.1115/1.4029572},
doi = {10.1115/1.4029572},
issn = {0098-2202},
year = {2015},
date = {2015-01-01},
urldate = {2015-01-01},
journal = {Journal of Fluids Engineering},
volume = {137},
issue = {5},
pages = {051109},
publisher = {… .asmedigitalcollection.asme.org},
abstract = {The unsteady phenomena of a low specific speed pump-turbine operating in pump mode were characterized by dynamic pressure measurements and high-speed flow visualization of injected air bubbles. Analyses were carried out on the pressure signals both in frequency and time-frequency domains and by bispectral protocol. The results obtained by high-speed camera were used to reveal the flow pattern in the diffuser and return vanes channels The unsteady structure identified in the return vane channel appeared both at full and part load condition. Furthermore, a rotating stall structure was found and characterized in the diffuser when the pump operated at part load. The characteristics of these two unsteady structures are described in the paper.},
note = {<b>From Duplicate 2 (<i>Experimental Characterization of a Pump–Turbine in Pump Mode at Hump Instability Region</i> - Yang, Jun; Pavesi, Giorgio; Yuan, Shouqi; ...; Cavazzini, Giovanna; Ardizzon, Guido)<br/></b><br/><b>From Duplicate 8 (<i>Experimental characterization of a pump–turbine in pump mode at hump instability region</i> - Yang, J; Pavesi, G; Yuan, S; ...)<br/></b><br/>Query date: 2017-05-06},
keywords = {Flow Visualization, high-speed, High-speed flow visualization, Hump-instability, hump-instability region, Pressure measurement, Pump, Pump as Turbine, Pump as Turbine, Rotating Stall, Turbine},
pubstate = {published},
tppubtype = {article}
}
The unsteady phenomena of a low specific speed pump-turbine operating in pump mode were characterized by dynamic pressure measurements and high-speed flow visualization of injected air bubbles. Analyses were carried out on the pressure signals both in frequency and time-frequency domains and by bispectral protocol. The results obtained by high-speed camera were used to reveal the flow pattern in the diffuser and return vanes channels The unsteady structure identified in the return vane channel appeared both at full and part load condition. Furthermore, a rotating stall structure was found and characterized in the diffuser when the pump operated at part load. The characteristics of these two unsteady structures are described in the paper.
2008
Pavesi, Giorgio; Cavazzini, Giovanna; Ardizzon, Guido
A Time-Frequency Post-Processing Technique for Characterization of the Unsteady Phenomena in the Turbomachines. Proceedings Article
In: XIX Biannual Symposium on Measuring Techniques in Turbomachinery Transonic and Supersonic Flow in Cascades and Turbomachines, pp. 1-5, 2008.
Abstract | BibTeX | Tags: Pump, Rotating Stall, Unsteady pressure, Wavelets
@inproceedings{Pavesi2008c,
title = {A Time-Frequency Post-Processing Technique for Characterization of the Unsteady Phenomena in the Turbomachines.},
author = {Giorgio Pavesi and Giovanna Cavazzini and Guido Ardizzon},
year = {2008},
date = {2008-01-01},
urldate = {2008-01-01},
booktitle = {XIX Biannual Symposium on Measuring Techniques in Turbomachinery Transonic and Supersonic Flow in Cascades and Turbomachines},
volume = {MTT1908-A6},
pages = {1-5},
abstract = {This paper presented a data processing technique that combines different signal analyses for the spectral characterization of the unsteady phenomena developing in the turbomachines. Tools of the classical Fourier analysis, such as second order spectra, were combined with tools of the time-frequency analysis (wavelets, cross-wavelet, coherence wavelet functions) to identify unsteady phenomena, to define their spectral structure, to analyse their evolution in time and to determine their possible propagation direction and velocity. Because of the non-linearity of several unsteady phenomena developing in turbomachines, high-order moment functions were applied to discriminate between non-linearly coupled pulsations and self-excited pulsations and to determine the fraction of the power of each pulsation that was due to the non-linear interaction of unsteady phenomena.},
keywords = {Pump, Rotating Stall, Unsteady pressure, Wavelets},
pubstate = {published},
tppubtype = {inproceedings}
}
This paper presented a data processing technique that combines different signal analyses for the spectral characterization of the unsteady phenomena developing in the turbomachines. Tools of the classical Fourier analysis, such as second order spectra, were combined with tools of the time-frequency analysis (wavelets, cross-wavelet, coherence wavelet functions) to identify unsteady phenomena, to define their spectral structure, to analyse their evolution in time and to determine their possible propagation direction and velocity. Because of the non-linearity of several unsteady phenomena developing in turbomachines, high-order moment functions were applied to discriminate between non-linearly coupled pulsations and self-excited pulsations and to determine the fraction of the power of each pulsation that was due to the non-linear interaction of unsteady phenomena.
Pavesi, Giorgio; Cavazzini, Giovanna; Ardizzon, Guido
Time-frequency characterization of the unsteady phenomena in a centrifugal pump Journal Article
In: International Journal of Heat and Fluid Flow, vol. 29, iss. 5, pp. 1527-1540, 2008, ISSN: 0142727X.
Abstract | Links | BibTeX | Tags: Pump, Rotating Stall, Unsteady pressure, Wavelets
@article{Pavesi2008a,
title = {Time-frequency characterization of the unsteady phenomena in a centrifugal pump},
author = {Giorgio Pavesi and Giovanna Cavazzini and Guido Ardizzon},
doi = {10.1016/j.ijheatfluidflow.2008.06.008},
issn = {0142727X},
year = {2008},
date = {2008-01-01},
journal = {International Journal of Heat and Fluid Flow},
volume = {29},
issue = {5},
pages = {1527-1540},
abstract = {The paper presents an experimental investigation of the flow field instability in a centrifugal pump. Pressure fluctuations were measured with transducers placed flush with the inlet duct, and at the impeller discharge. Two impeller rotation speeds were utilized in the study, as well as several angular and radial transducer positions at design, and at off-design flow rates. A spectral analysis was carried out on the pressure signals in frequency and in time-frequency domains. The results highlighted the existence of an asymmetrical rotating pressure structure at the impeller discharge, having a fluid-dynamical origin and propagating both in the radial and circumferential direction, inside and downstream of the impeller. © 2008 Elsevier Inc. All rights reserved.},
keywords = {Pump, Rotating Stall, Unsteady pressure, Wavelets},
pubstate = {published},
tppubtype = {article}
}
The paper presents an experimental investigation of the flow field instability in a centrifugal pump. Pressure fluctuations were measured with transducers placed flush with the inlet duct, and at the impeller discharge. Two impeller rotation speeds were utilized in the study, as well as several angular and radial transducer positions at design, and at off-design flow rates. A spectral analysis was carried out on the pressure signals in frequency and in time-frequency domains. The results highlighted the existence of an asymmetrical rotating pressure structure at the impeller discharge, having a fluid-dynamical origin and propagating both in the radial and circumferential direction, inside and downstream of the impeller. © 2008 Elsevier Inc. All rights reserved.
Pavesi, Giorgio; Cavazzini, Giovanna; Ardizzon, Guido
Time-frequency characterization of rotating instabilities in a centrifugal pump with a vaned diffuser Journal Article
In: International journal of rotating …, vol. 29, iss. 5, pp. 1527-1540, 2008, ISSN: 0142727X.
Abstract | Links | BibTeX | Tags: Pump, Rotating Stall, Unsteady pressure, Wavelets
@article{pop00038,
title = {Time-frequency characterization of rotating instabilities in a centrifugal pump with a vaned diffuser},
author = {Giorgio Pavesi and Giovanna Cavazzini and Guido Ardizzon},
url = {https://www.hindawi.com/journals/ijrm/2008/202179/abs/ http://www.sciencedirect.com/science/article/pii/S0142727X08001124},
doi = {10.1016/j.ijheatfluidflow.2008.06.008},
issn = {0142727X},
year = {2008},
date = {2008-01-01},
urldate = {2008-01-01},
journal = {International journal of rotating …},
volume = {29},
issue = {5},
pages = {1527-1540},
publisher = {hindawi.com},
abstract = {The paper presents an experimental investigation of the flow field instability in a centrifugal pump. Pressure fluctuations were measured with transducers placed flush with the inlet duct, and at the impeller discharge. Two impeller rotation speeds were utilized in the study, as well as several angular and radial transducer positions at design, and at off-design flow rates. A spectral analysis was carried out on the pressure signals in frequency and in time-frequency domains. The results highlighted the existence of an asymmetrical rotating pressure structure at the impeller discharge, having a fluid-dynamical origin and propagating both in the radial and circumferential direction, inside and downstream of the impeller. © 2008 Elsevier Inc. All rights reserved.},
keywords = {Pump, Rotating Stall, Unsteady pressure, Wavelets},
pubstate = {published},
tppubtype = {article}
}
The paper presents an experimental investigation of the flow field instability in a centrifugal pump. Pressure fluctuations were measured with transducers placed flush with the inlet duct, and at the impeller discharge. Two impeller rotation speeds were utilized in the study, as well as several angular and radial transducer positions at design, and at off-design flow rates. A spectral analysis was carried out on the pressure signals in frequency and in time-frequency domains. The results highlighted the existence of an asymmetrical rotating pressure structure at the impeller discharge, having a fluid-dynamical origin and propagating both in the radial and circumferential direction, inside and downstream of the impeller. © 2008 Elsevier Inc. All rights reserved.
