2023
Zanetti, Giacomo; Cavazzini, Giovanna; Santolin, Alberto
Effect of the von Karman Shedding Frequency on the Hydrodynamics of a Francis Turbine Operating at Nominal Load Journal Article
In: International Journal of Turbomachinery, Propulsion and Power 2023, Vol. 8, Page 27, vol. 8, iss. 3, pp. 27, 2023, ISSN: 2504-186X.
Abstract | Links | BibTeX | Tags: Francis Turbine, Interblade vortex, mechanical resonance, von Karman vortices
@article{Zanetti2023b,
title = {Effect of the von Karman Shedding Frequency on the Hydrodynamics of a Francis Turbine Operating at Nominal Load},
author = {Giacomo Zanetti and Giovanna Cavazzini and Alberto Santolin},
url = {https://www.mdpi.com/2504-186X/8/3/27/htm https://www.mdpi.com/2504-186X/8/3/27},
doi = {10.3390/IJTPP8030027},
issn = {2504-186X},
year = {2023},
date = {2023-01-01},
journal = {International Journal of Turbomachinery, Propulsion and Power 2023, Vol. 8, Page 27},
volume = {8},
issue = {3},
pages = {27},
publisher = {Multidisciplinary Digital Publishing Institute},
abstract = {This paper presents a numerical analysis of the influence of the von Karman vortex shedding at the blade trailing edge on the hydrodynamics of a recently installed small hydro Francis turbine manifesting very loud and high-frequency acoustic pulsations when operating close to the nominal load. A reduced single-passage numerical model is developed to reduce the computational effort of the simulation while ensuring high accuracy in the assessment of fluid flow. The accuracy of the proposed numerical approach is investigated by comparing the frequency spectrum of the experimentally acquired acoustic frequency and the numerical pressure signals, confirming the nature of the machine’s vibrations. The validated numerical model represents a useful tool for an in-depth analysis of the machine’s hydrodynamics in the preliminary design phases. The proposed approach represents a valid alternative to the traditional correlation-based approach for the evaluation of the von Karman shedding frequency with less computational effort compared with a transient simulation of the entire machine.},
keywords = {Francis Turbine, Interblade vortex, mechanical resonance, von Karman vortices},
pubstate = {published},
tppubtype = {article}
}
This paper presents a numerical analysis of the influence of the von Karman vortex shedding at the blade trailing edge on the hydrodynamics of a recently installed small hydro Francis turbine manifesting very loud and high-frequency acoustic pulsations when operating close to the nominal load. A reduced single-passage numerical model is developed to reduce the computational effort of the simulation while ensuring high accuracy in the assessment of fluid flow. The accuracy of the proposed numerical approach is investigated by comparing the frequency spectrum of the experimentally acquired acoustic frequency and the numerical pressure signals, confirming the nature of the machine’s vibrations. The validated numerical model represents a useful tool for an in-depth analysis of the machine’s hydrodynamics in the preliminary design phases. The proposed approach represents a valid alternative to the traditional correlation-based approach for the evaluation of the von Karman shedding frequency with less computational effort compared with a transient simulation of the entire machine.
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
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.
1998
Ardizzon, Guido; Pavesi, Giorgio; Ventrone, Giuseppe
Analisi Sperimentale del Moto e delle Perdite Fluidodinamiche in una Turbina Francis Proceedings Article
In: 53° Congresso Nazionale ATI, pp. 925-936, SGE - Padova, 1998.
Abstract | BibTeX | Tags: Francis Turbine, Hydraulic Losses
@inproceedings{ArdizzonGPavesiGVentroneG1998,
title = {Analisi Sperimentale del Moto e delle Perdite Fluidodinamiche in una Turbina Francis},
author = {Guido Ardizzon and Giorgio Pavesi and Giuseppe Ventrone},
year = {1998},
date = {1998-01-01},
urldate = {1998-01-01},
booktitle = {53° Congresso Nazionale ATI},
pages = {925-936},
publisher = {SGE - Padova},
abstract = {Sono presentati 1 risultati di una ricerca volta ad accertare le perdite in una turbina Francis a diverse condizioni operative. Misure di pressione e velocitä hanno permesso di valutare le perdite fluidodinamiche all’interno della macchina, mentre la sostituzione della girante con una piena, ma di uguale forma geometrica esterna, ha consentito di misurare la portata di fuga e la potenza dissipata per ventilazione. E” stata, inoltre, ricercata la condizione d’incidenza ottimale e stimata l’entità della deviazione della corrente relativa all’uscita della girante.},
keywords = {Francis Turbine, Hydraulic Losses},
pubstate = {published},
tppubtype = {inproceedings}
}
Sono presentati 1 risultati di una ricerca volta ad accertare le perdite in una turbina Francis a diverse condizioni operative. Misure di pressione e velocitä hanno permesso di valutare le perdite fluidodinamiche all’interno della macchina, mentre la sostituzione della girante con una piena, ma di uguale forma geometrica esterna, ha consentito di misurare la portata di fuga e la potenza dissipata per ventilazione. E” stata, inoltre, ricercata la condizione d’incidenza ottimale e stimata l’entità della deviazione della corrente relativa all’uscita della girante.
