2016
Pavesi, Giorgio; Cavazzini, Giovanna; Ardizzon, Guido
Numerical Simulation of a Pump-Turbine Transient Load Following Process in Pump Mode Proceedings Article
In: ISROMAC, researchgate.net, 2016, (Query date: 2017-05-06).
Abstract | Links | BibTeX | Tags: Francis Turbine, Francis-type Reversible Turbine, PAT, Variable Speed
@inproceedings{pop00006,
title = {Numerical Simulation of a Pump-Turbine Transient Load Following Process in Pump Mode},
author = {Giorgio Pavesi and Giovanna Cavazzini and Guido Ardizzon},
url = {https://www.researchgate.net/profile/Giorgio_Pavesi/publication/308522782_ISROMAC_2016_International_Sym-posium_on_Transport_Phenomena_and_Dynamics_of_Rotating_Machinery/links/57e630b608aedcd5d1a44471.pdf},
year = {2016},
date = {2016-01-01},
urldate = {2016-01-01},
booktitle = {ISROMAC},
publisher = {researchgate.net},
abstract = {This paper presents the simulation of the dynamic behaviour of variable speed pump-turbine. A power reduction scenario at constant wicket gate opening was numerically analysed from 100% to 93% rpm corresponding to a power reduction from full load to about 70% with a ramp rate of 1.5% per second. The flow field analysis led to the onset and development of unsteady phenomena progressively evolving in an organized rotating partial stall during the pump power reduction. These phenomena were characterized by frequency and time-frequency analyses of several numerical signals (pressure, blade torque, flow rate in blade passages). The unsteady pattern in return channel strengthened emphasizing its characteristic frequency with the rotational velocity decreasing posium on reaching a maximum and then disappearing. At lower rotational speed, the flow field into the Transport wickets gates channel start to manifest a full three-dimensional flow structure. This disturbance was related to the boundary layer separation and stall and it was noticed by a specific frequency},
note = {Query date: 2017-05-06},
keywords = {Francis Turbine, Francis-type Reversible Turbine, PAT, Variable Speed},
pubstate = {published},
tppubtype = {inproceedings}
}
This paper presents the simulation of the dynamic behaviour of variable speed pump-turbine. A power reduction scenario at constant wicket gate opening was numerically analysed from 100% to 93% rpm corresponding to a power reduction from full load to about 70% with a ramp rate of 1.5% per second. The flow field analysis led to the onset and development of unsteady phenomena progressively evolving in an organized rotating partial stall during the pump power reduction. These phenomena were characterized by frequency and time-frequency analyses of several numerical signals (pressure, blade torque, flow rate in blade passages). The unsteady pattern in return channel strengthened emphasizing its characteristic frequency with the rotational velocity decreasing posium on reaching a maximum and then disappearing. At lower rotational speed, the flow field into the Transport wickets gates channel start to manifest a full three-dimensional flow structure. This disturbance was related to the boundary layer separation and stall and it was noticed by a specific frequency
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.
2013
Santolin, Alberto; Pavesi, Giorgio; Cavazzini, Giovanna; Ardizzon, Guido
Variable-speed Pelton turbine for an efficient exploitation of the reserved flow: an Italian case study Proceedings Article
In: HYDRO 2013 - Promoting the Versatile Role of Hydro, 2013.
Abstract | BibTeX | Tags: Pelton Turbine, Variable Speed
@inproceedings{Santolin2013,
title = {Variable-speed Pelton turbine for an efficient exploitation of the reserved flow: an Italian case study},
author = {Alberto Santolin and Giorgio Pavesi and Giovanna Cavazzini and Guido Ardizzon},
year = {2013},
date = {2013-01-01},
urldate = {2013-01-01},
booktitle = {HYDRO 2013 - Promoting the Versatile Role of Hydro},
abstract = {This paper presents an Italian case study of a small hydropower plant exploiting the reserved flow (RF) at the dam outlet. The significant variations of the water level in the reservoir and of the seasonal RF discharged in accordance with the Italian environmental laws determine extremely variable operating conditions for the hydropower plant that can be efficiently faced only resorting to a variable speed turbine. This breakthrough technology allows to optimize the machine performance at a wider range of operating conditions, but still presents several issues to be faced, for example the lack of standardized design criteria. This study was focused on the design optimization of the variable-speed Pelton turbine to be installed in the small hydropower plant. Numerical analyses were carried out by the commercial code Ansys CFX 14 to define a Pelton bucket geometry characterized by high efficiency values in the requested wide operating range. , A transient homogeneous model coupled with a SST turbulence model was applied to solve the two-phase flow field., Experimental analyses were also carried out on the optimized runner in an open water test rig of the Laboratory of Turbomachinery of the University of Padova to validate the numerical simulations results. The experimental test rig, equipped with a pressurized reservoir, was properly settled so as to verify the turbine performance in a wide operating range. Finally, the results of the combined numerical and experimental design optimization were verified by comparison with the performance of the model installed in the small hydropower plant of Forte Buso.},
keywords = {Pelton Turbine, Variable Speed},
pubstate = {published},
tppubtype = {inproceedings}
}
This paper presents an Italian case study of a small hydropower plant exploiting the reserved flow (RF) at the dam outlet. The significant variations of the water level in the reservoir and of the seasonal RF discharged in accordance with the Italian environmental laws determine extremely variable operating conditions for the hydropower plant that can be efficiently faced only resorting to a variable speed turbine. This breakthrough technology allows to optimize the machine performance at a wider range of operating conditions, but still presents several issues to be faced, for example the lack of standardized design criteria. This study was focused on the design optimization of the variable-speed Pelton turbine to be installed in the small hydropower plant. Numerical analyses were carried out by the commercial code Ansys CFX 14 to define a Pelton bucket geometry characterized by high efficiency values in the requested wide operating range. , A transient homogeneous model coupled with a SST turbulence model was applied to solve the two-phase flow field., Experimental analyses were also carried out on the optimized runner in an open water test rig of the Laboratory of Turbomachinery of the University of Padova to validate the numerical simulations results. The experimental test rig, equipped with a pressurized reservoir, was properly settled so as to verify the turbine performance in a wide operating range. Finally, the results of the combined numerical and experimental design optimization were verified by comparison with the performance of the model installed in the small hydropower plant of Forte Buso.
