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.
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.
Mao, Xiuli; Sun, Aoran; Pavesi, Giorgio; Zheng, Yuan; Ge, Xinfeng
Simulation of flow induced noise in process of pump-turbine load rejection Journal Article
In: Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering, vol. 34, iss. 20, pp. 52-58, 2018, ISSN: 10026819.
Abstract | Links | BibTeX | Tags: Impellers, Load rejection process, Noise, Pressure, Pump as Turbine
@article{Mao2018,
title = {Simulation of flow induced noise in process of pump-turbine load rejection},
author = {Xiuli Mao and Aoran Sun and Giorgio Pavesi and Yuan Zheng and Xinfeng Ge},
url = {http://www.tcsae.org},
doi = {10.11975/j.issn.1002-6819.2018.20.007},
issn = {10026819},
year = {2018},
date = {2018-01-01},
journal = {Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering},
volume = {34},
issue = {20},
pages = {52-58},
abstract = {The grid market is redistributed with significantly increase of the exploitation of unpredictable renewable energy, such as wind and solar energy sources, however, the ways of electricity generation by both wind and solar energy depend on environment which is extremely unstable. For the sake of balancing electricity generated by renewable energy, pumped storage power stations are experiencing a thriving process. As the core of pumped storage power station, the stable operation of the pump turbine is extremely important, especially for pump-turbine working at transient conditions. In order to study pressure fluctuating characteristics and its' influence on flow-induced noise, a continuous unsteady simulation was carried out in pump-turbine guide vane closing process under generating mode. In this article, wall sliding mesh was used to realize guide vane continuous motion, which ensured that the mesh quality at any moment was larger than 60% compared with the initial mesh quality, meanwhile, DES turbulent model was adopted in all calculations due to its good performance in many industrial cases. The whole pump-turbine model was meshed with structured mesh by commercial software ICEM, and five different mesh sizes were used in mesh sensitivity validation, with the size of 14 million selected finally. On the other hand, a test was performed by the team of Giorgio Pavesi to prove this model in open test facility in Padova University, the entire model validation was carried out according to ISO standards, and relative parameters were measured based on IEC standards. Commercial software ANYSYS CFX 16.2 was used to realize all simulating calculations with 8 computer cores, one month was taken to finish this calculation. The flow field calculating results were analyzed in frequency and time-frequency domains, including mass flow, pressure, and torque et al., in the meantime, the pressure on the surfaces of blades was regarded as flow-induced noise source to study sound field. The solution obtained from flow field illustrates that pressure fluctuating amplitudes at guide vane outlet is more than twice compared to the relative value at guide vane inlet location, the main reason is flow in the vaneless space that is close to runner is affected by rotor-rotor interaction. In addition, pressure pulsations at runner outlet arrive at peaks when two vortexes appear in draft tube with two different rotating directions. As for frequency domain characteristics, both strauhal number St=0.051 and St=1 are captured, whereas the spectrum of those pressure fluctuations that are close to guide vane outlet is 10 times of the relative value at guide vane inlet, which explains that rotor-rotor interaction has a stronger influence on flow field than rotor-stator interaction. Some rules are found by analyzing flow-induced noise in sound field, the analysis illustrates that flow-induced noise radiation level is related to both pressure fluctuating and shell natural frequency captured in exterior acoustic field, the shape of sound distribution is like "∞" and sound level distributions in different directions and faces are symmetrical, this explains that the blade noise radiation has obvious dipole characteristics. Furthermore, at the first and second-order blade passage frequencies, the effect of flow rate on the radiation performance of noise is stronger under larger flow conditions during guide vane closure, which becomes weaker under smaller flow conditions in the first half of the guide vane closure, as for the second half phase of guide vane closure, the results are exactly opposite to the previous phenomena. Moreover, flow-induced noise radiation is consistent with fluid characteristics during pump-turbine load rejection. Consequently, to improve pressure fluctuating characteristics can reduce flow-induced noise.},
keywords = {Impellers, Load rejection process, Noise, Pressure, Pump as Turbine},
pubstate = {published},
tppubtype = {article}
}
The grid market is redistributed with significantly increase of the exploitation of unpredictable renewable energy, such as wind and solar energy sources, however, the ways of electricity generation by both wind and solar energy depend on environment which is extremely unstable. For the sake of balancing electricity generated by renewable energy, pumped storage power stations are experiencing a thriving process. As the core of pumped storage power station, the stable operation of the pump turbine is extremely important, especially for pump-turbine working at transient conditions. In order to study pressure fluctuating characteristics and its' influence on flow-induced noise, a continuous unsteady simulation was carried out in pump-turbine guide vane closing process under generating mode. In this article, wall sliding mesh was used to realize guide vane continuous motion, which ensured that the mesh quality at any moment was larger than 60% compared with the initial mesh quality, meanwhile, DES turbulent model was adopted in all calculations due to its good performance in many industrial cases. The whole pump-turbine model was meshed with structured mesh by commercial software ICEM, and five different mesh sizes were used in mesh sensitivity validation, with the size of 14 million selected finally. On the other hand, a test was performed by the team of Giorgio Pavesi to prove this model in open test facility in Padova University, the entire model validation was carried out according to ISO standards, and relative parameters were measured based on IEC standards. Commercial software ANYSYS CFX 16.2 was used to realize all simulating calculations with 8 computer cores, one month was taken to finish this calculation. The flow field calculating results were analyzed in frequency and time-frequency domains, including mass flow, pressure, and torque et al., in the meantime, the pressure on the surfaces of blades was regarded as flow-induced noise source to study sound field. The solution obtained from flow field illustrates that pressure fluctuating amplitudes at guide vane outlet is more than twice compared to the relative value at guide vane inlet location, the main reason is flow in the vaneless space that is close to runner is affected by rotor-rotor interaction. In addition, pressure pulsations at runner outlet arrive at peaks when two vortexes appear in draft tube with two different rotating directions. As for frequency domain characteristics, both strauhal number St=0.051 and St=1 are captured, whereas the spectrum of those pressure fluctuations that are close to guide vane outlet is 10 times of the relative value at guide vane inlet, which explains that rotor-rotor interaction has a stronger influence on flow field than rotor-stator interaction. Some rules are found by analyzing flow-induced noise in sound field, the analysis illustrates that flow-induced noise radiation level is related to both pressure fluctuating and shell natural frequency captured in exterior acoustic field, the shape of sound distribution is like "∞" and sound level distributions in different directions and faces are symmetrical, this explains that the blade noise radiation has obvious dipole characteristics. Furthermore, at the first and second-order blade passage frequencies, the effect of flow rate on the radiation performance of noise is stronger under larger flow conditions during guide vane closure, which becomes weaker under smaller flow conditions in the first half of the guide vane closure, as for the second half phase of guide vane closure, the results are exactly opposite to the previous phenomena. Moreover, flow-induced noise radiation is consistent with fluid characteristics during pump-turbine load rejection. Consequently, to improve pressure fluctuating characteristics can reduce flow-induced noise.
Yang, Jun; Xie, Tian; Giorgio, Pavesi; Liu, Xiaohua; Liu, Jun
Numerical study on rotating characteristics of unsteady flow inner pump-turbine in pump mode Journal Article
In: International Journal of Fluid Machinery and Systems, vol. 11, iss. 3, pp. 224-233, 2018, ISSN: 18829554.
Abstract | Links | BibTeX | Tags: Pump as Turbine, Pump Mode, Rotating characteristics, Unsteady Flow
@article{Yang2018a,
title = {Numerical study on rotating characteristics of unsteady flow inner pump-turbine in pump mode},
author = {Jun Yang and Tian Xie and Pavesi Giorgio and Xiaohua Liu and Jun Liu},
doi = {10.5293/IJFMS.2018.11.3.224},
issn = {18829554},
year = {2018},
date = {2018-01-01},
journal = {International Journal of Fluid Machinery and Systems},
volume = {11},
issue = {3},
pages = {224-233},
abstract = {In order to investigate the formation of the rotating stall in diffuser of pump-turbine in pump mode, the unsteady flow with radial rotating characteristics before the occurrence of rotating stall are investigated by detached eddy simulation. The results indicate that the unsteady flow patterns which occur in the return channel both at full and part load conditions contain two periodical disturbances with frequencies St≈0.042 and St≈0.085, and the Strouhal number St is frequency normalized by blade passing frequency of impeller. These periodical disturbances not only influence the pressure field but also cause rotating characteristics in diffuser channels. One is composed of 4 cells propagating at 0.073 times of impeller rotating speed. The other one is made up of 3 rotating cells with 0.2 times of backward impeller rotating speed. Meanwhile, there are two radial rotating characteristics which contribute the spectra peak at blade pass frequency in diffuser. One is at the inlet of diffuser propagating at impeller rotating speed with 7 cells, and the other one contains 4 cells with about 1.75 backward impeller rotating speed.},
keywords = {Pump as Turbine, Pump Mode, Rotating characteristics, Unsteady Flow},
pubstate = {published},
tppubtype = {article}
}
In order to investigate the formation of the rotating stall in diffuser of pump-turbine in pump mode, the unsteady flow with radial rotating characteristics before the occurrence of rotating stall are investigated by detached eddy simulation. The results indicate that the unsteady flow patterns which occur in the return channel both at full and part load conditions contain two periodical disturbances with frequencies St≈0.042 and St≈0.085, and the Strouhal number St is frequency normalized by blade passing frequency of impeller. These periodical disturbances not only influence the pressure field but also cause rotating characteristics in diffuser channels. One is composed of 4 cells propagating at 0.073 times of impeller rotating speed. The other one is made up of 3 rotating cells with 0.2 times of backward impeller rotating speed. Meanwhile, there are two radial rotating characteristics which contribute the spectra peak at blade pass frequency in diffuser. One is at the inlet of diffuser propagating at impeller rotating speed with 7 cells, and the other one contains 4 cells with about 1.75 backward impeller rotating speed.
Cavazzini, Giovanna; Houdeline, Jean-Bernard Bernard; Pavesi, Giorgio; Teller, Olivier; Ardizzon, Guido
Unstable behaviour of pump-turbines and its effects on power regulation capacity of pumped-hydro energy storage plants Journal Article
In: Renewable and Sustainable Energy Reviews, vol. 94, iss. April 2017, pp. 399-409, 2018, ISSN: 18790690.
Abstract | Links | BibTeX | Tags: Hump zone, Pump as Turbine, Pumped-hydro, S-shape, Storage, Unstable behaviour
@article{Cavazzini2018,
title = {Unstable behaviour of pump-turbines and its effects on power regulation capacity of pumped-hydro energy storage plants},
author = {Giovanna Cavazzini and Jean-Bernard Bernard Houdeline and Giorgio Pavesi and Olivier Teller and Guido Ardizzon},
url = {https://doi.org/10.1016/j.rser.2018.06.018 https://linkinghub.elsevier.com/retrieve/pii/S1364032118304532},
doi = {10.1016/j.rser.2018.06.018},
issn = {18790690},
year = {2018},
date = {2018-01-01},
journal = {Renewable and Sustainable Energy Reviews},
volume = {94},
issue = {April 2017},
pages = {399-409},
publisher = {Elsevier Ltd},
abstract = {Intermittent renewable energy sources are characterized by a highly fluctuating, unpredictable and delocalized energy production, which significantly limits their penetration in the grid due to the great problems caused in the balance between demand and supply. Pumped Hydro Energy Storage plants represent an ideal solution because of their ability to provide large storage capacity with excellent grid connection properties, high cycle efficiency range and competitive costs. However, to provide primary and secondary regulation services, PHES have to increase their operation at part loads and to be able to switch fast and frequently between pump and turbine modes. At these operating conditions, pump-turbines suffer from behaviour instabilities, thereby constituting a limit when considering their exploitation in a wider continuous working range. So, the definition of a new concept of pump-turbines able to provide the full benefit of regulation in pumping mode and a wide range of power in generation mode is an urgent need to increase the exploitation of renewable energy sources. This paper clarifies the effects of the stable and unstable behaviour of pump-turbines on the power regulation capacity of pumped hydro energy storage plants, by presenting a description of the possible operating modes of PHES and by focusing on the impact of the hydraulic characteristics of pump-turbines on the capability of plant to start-up, shut-down or change its operating modes. A detailed review of the studies published in literature on the topic revealed the main characteristics of the hydraulic instabilities and the influence of one or more geometrical parameters on their onset. Even though some geometry modifications aimed at improving the RPT's stability in one operating mode were proposed in literature, the definition of a comprehensive design strategy, globally optimizing the pump-turbine design by considering simultaneously the complexity of the phenomena in both the operating modes, still represents a challenge.},
keywords = {Hump zone, Pump as Turbine, Pumped-hydro, S-shape, Storage, Unstable behaviour},
pubstate = {published},
tppubtype = {article}
}
Intermittent renewable energy sources are characterized by a highly fluctuating, unpredictable and delocalized energy production, which significantly limits their penetration in the grid due to the great problems caused in the balance between demand and supply. Pumped Hydro Energy Storage plants represent an ideal solution because of their ability to provide large storage capacity with excellent grid connection properties, high cycle efficiency range and competitive costs. However, to provide primary and secondary regulation services, PHES have to increase their operation at part loads and to be able to switch fast and frequently between pump and turbine modes. At these operating conditions, pump-turbines suffer from behaviour instabilities, thereby constituting a limit when considering their exploitation in a wider continuous working range. So, the definition of a new concept of pump-turbines able to provide the full benefit of regulation in pumping mode and a wide range of power in generation mode is an urgent need to increase the exploitation of renewable energy sources. This paper clarifies the effects of the stable and unstable behaviour of pump-turbines on the power regulation capacity of pumped hydro energy storage plants, by presenting a description of the possible operating modes of PHES and by focusing on the impact of the hydraulic characteristics of pump-turbines on the capability of plant to start-up, shut-down or change its operating modes. A detailed review of the studies published in literature on the topic revealed the main characteristics of the hydraulic instabilities and the influence of one or more geometrical parameters on their onset. Even though some geometry modifications aimed at improving the RPT's stability in one operating mode were proposed in literature, the definition of a comprehensive design strategy, globally optimizing the pump-turbine design by considering simultaneously the complexity of the phenomena in both the operating modes, still represents a challenge.
2017
Pavesi, Giorgio; Wang, Wenjie
Numerical investigation on transient flow of a high head pump-turbine in pump mode during rapid closure of wicket gates Proceedings Article
In: 12th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2017, 2017, ISSN: 24104833.
Abstract | BibTeX | Tags: Closure of Wicket Gate, Moving mesh, Pump as Turbine, transient flow, Water compressibility
@inproceedings{Pavesi2017a,
title = {Numerical investigation on transient flow of a high head pump-turbine in pump mode during rapid closure of wicket gates},
author = {Giorgio Pavesi and Wenjie Wang},
issn = {24104833},
year = {2017},
date = {2017-01-01},
booktitle = {12th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2017},
abstract = {Copyright © by the Authors. Transient flow in pump turbines appears because the hydropower storage plant needs to experience variable operation modes to make a balance between the electricity production and consumption, thus causing high-pressure fluctuations and shortening life expectancy. In this paper, three-dimensional numerical simulation, based on Detached Eddy Simulation (DES) turbulent model, was carried out to investigate the flow characteristics in a high head pump turbine in pump mode during rapid closure of wicket gates. The dynamic mesh technique was applied to simulate the rotation of the guide vane. In this work, the influence of water compressibility on pressure fluctuations was considered. The transient flow characteristics during load reduction were investigated by time-frequency analysis methods of the numerical data.},
keywords = {Closure of Wicket Gate, Moving mesh, Pump as Turbine, transient flow, Water compressibility},
pubstate = {published},
tppubtype = {inproceedings}
}
Copyright © by the Authors. Transient flow in pump turbines appears because the hydropower storage plant needs to experience variable operation modes to make a balance between the electricity production and consumption, thus causing high-pressure fluctuations and shortening life expectancy. In this paper, three-dimensional numerical simulation, based on Detached Eddy Simulation (DES) turbulent model, was carried out to investigate the flow characteristics in a high head pump turbine in pump mode during rapid closure of wicket gates. The dynamic mesh technique was applied to simulate the rotation of the guide vane. In this work, the influence of water compressibility on pressure fluctuations was considered. The transient flow characteristics during load reduction were investigated by time-frequency analysis methods of the numerical data.
2016
Pavesi, Giorgio; Cavazzini, Giovanna; Ardizzon, Guido
Numerical analysis of the transient behaviour of a variable speed pump-turbine during a pumping power reduction scenario Journal Article
In: Energies, vol. 9, iss. 7, pp. 1-15, 2016, ISSN: 19961073.
Abstract | Links | BibTeX | Tags: Adjustable Speed Hydro Plants, Dynamic response, Dynamic response of hydro plants, Hydro plant control, Pump as Turbine, Variable Speed, Variable-speed regulation
@article{pop00005,
title = {Numerical analysis of the transient behaviour of a variable speed pump-turbine during a pumping power reduction scenario},
author = {Giorgio Pavesi and Giovanna Cavazzini and Guido Ardizzon},
url = {http://www.mdpi.com/1996-1073/9/7/534 http://www.mdpi.com/1996-1073/9/7/534/htm},
doi = {10.3390/en9070534},
issn = {19961073},
year = {2016},
date = {2016-01-01},
urldate = {2016-01-01},
journal = {Energies},
volume = {9},
issue = {7},
pages = {1-15},
publisher = {mdpi.com},
abstract = {To achieve the carbon free electricity generation target for 2050, the penetration of renewable energy sources should further increase. To address the impacts of their unpredictable and intermittent characteristics on the future electricity grid, Pumped Hydro Energy Storage (PHES) plants should enhance their regulation capability by extending their continuous operating range far beyond the optimal normal working range. However, for the time being, the regulation capability of the new generation of PHES, equipped with reversible pump-turbines due to their cost-effectiveness, is limited at part load by instability problems. The aim of this paper is to analyse, during a pumping power reduction scenario, the onset and development of unsteady phenomena leading to unstable behaviour. A 3D transient numerical simulation was carried out on the first stage of a variable-speed two-stage pump-turbine from full load to the unstable operating zone by progressively reducing the speed from 100% to 88% rpm corresponding to a power reduction from full load to about 60% with a ramp rate of 1.5% per s. Two three-dimensional unsteady flow structures affecting the return channel and the wicket gates at the end of the first stage were identified and their evolution in the power regulation scenario was fluid-dynamically and spectrally characterized to determine the fluid-dynamical conditions causing the head drop in the hump zone.},
keywords = {Adjustable Speed Hydro Plants, Dynamic response, Dynamic response of hydro plants, Hydro plant control, Pump as Turbine, Variable Speed, Variable-speed regulation},
pubstate = {published},
tppubtype = {article}
}
To achieve the carbon free electricity generation target for 2050, the penetration of renewable energy sources should further increase. To address the impacts of their unpredictable and intermittent characteristics on the future electricity grid, Pumped Hydro Energy Storage (PHES) plants should enhance their regulation capability by extending their continuous operating range far beyond the optimal normal working range. However, for the time being, the regulation capability of the new generation of PHES, equipped with reversible pump-turbines due to their cost-effectiveness, is limited at part load by instability problems. The aim of this paper is to analyse, during a pumping power reduction scenario, the onset and development of unsteady phenomena leading to unstable behaviour. A 3D transient numerical simulation was carried out on the first stage of a variable-speed two-stage pump-turbine from full load to the unstable operating zone by progressively reducing the speed from 100% to 88% rpm corresponding to a power reduction from full load to about 60% with a ramp rate of 1.5% per s. Two three-dimensional unsteady flow structures affecting the return channel and the wicket gates at the end of the first stage were identified and their evolution in the power regulation scenario was fluid-dynamically and spectrally characterized to determine the fluid-dynamical conditions causing the head drop in the hump zone.
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.
2010
Pavesi, Giorgio; Cavazzini, Giovanna; Ardizzon, Guido
Time–Frequency Characterization of a Rotating Multi-Lobes Pressure Fluctuation in a Centrifugal Vaned Pump: Experimental Investigation Proceedings Article
In: 13th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery 2010, ISROMAC-13, pp. 1-8, 2010, ISBN: 9781617388484.
Abstract | BibTeX | Tags: Francis-type Reversible Turbine, Pressure fluctuations, Pump as Turbine
@inproceedings{Pavesi2010a,
title = {Time–Frequency Characterization of a Rotating Multi-Lobes Pressure Fluctuation in a Centrifugal Vaned Pump: Experimental Investigation},
author = {Giorgio Pavesi and Giovanna Cavazzini and Guido Ardizzon},
isbn = {9781617388484},
year = {2010},
date = {2010-01-01},
urldate = {2010-01-01},
booktitle = {13th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery 2010, ISROMAC-13},
pages = {1-8},
abstract = {This paper presents experimental investigations of the unsteady phenomena developing in a centrifugal vaned pump. Miniaturized pressure transducers were mounted flushed with the walls on one diffuser blade, in the inlet duct and at the impeller discharge, at different radial and circumferential positions. The analysis was carried out at several flow rates and at two different impeller rotation velocities. The influence of the operating conditions, the presence of diffuser blades on the existence, and the characteristics of the unsteady phenomena were studied. Linear spectral analysis techniques were applied both in frequency and in the time-frequency domains in order to define the pressure signals spectral content and its evolution in time. Moreover, the possible presence of mechanisms of non-linear interaction between pressure pulsations was studied applying functions of the high-order spectral analysis so as to discriminate between fundamental frequency and coupled pulsations due to the interaction between the phenomena. The existence of a rotating multi-lobes pressure structure at the impeller discharge, having fluid-dynamical origin, was demonstrated. This instability was verified to propagate both inside and downstream the impeller. Copyright ? 2010 by ISROMAC-13.},
keywords = {Francis-type Reversible Turbine, Pressure fluctuations, Pump as Turbine},
pubstate = {published},
tppubtype = {inproceedings}
}
This paper presents experimental investigations of the unsteady phenomena developing in a centrifugal vaned pump. Miniaturized pressure transducers were mounted flushed with the walls on one diffuser blade, in the inlet duct and at the impeller discharge, at different radial and circumferential positions. The analysis was carried out at several flow rates and at two different impeller rotation velocities. The influence of the operating conditions, the presence of diffuser blades on the existence, and the characteristics of the unsteady phenomena were studied. Linear spectral analysis techniques were applied both in frequency and in the time-frequency domains in order to define the pressure signals spectral content and its evolution in time. Moreover, the possible presence of mechanisms of non-linear interaction between pressure pulsations was studied applying functions of the high-order spectral analysis so as to discriminate between fundamental frequency and coupled pulsations due to the interaction between the phenomena. The existence of a rotating multi-lobes pressure structure at the impeller discharge, having fluid-dynamical origin, was demonstrated. This instability was verified to propagate both inside and downstream the impeller. Copyright ? 2010 by ISROMAC-13.
