Publications

@inproceedings{pop00016,

title = {Flow Phenomena Related to the Unstable Energy-Discharge Characteristic of a Pump-Turbine in Pump Mode},

author = {Giorgio Pavesi and Giovanna Cavazzini and Jung Yang and Guido Ardizzon},

url = {https://www.researchgate.net/profile/Giorgio_Pavesi/publication/288996574_Flow_phenomena_related_to_the_unstable_energy-discharge_characteristic_of_a_pump-turbine_in_pump_mode/links/568e43ba08ae78cc051591d3.pdf},

year  = {2014},

date = {2014-01-01},

urldate = {2014-01-01},

booktitle = {15th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, ISROMAC 2014},

pages = {1-8},

publisher = {researchgate.net},

abstract = {Renewable energy sources such as wind and sun have varying and, to some extent, unpredictable production. Pumped storage power plants can play an important role in stabilizing the electric power system when the production is either too high or too low. Subsequently, many new pumped storage power plants have been recently initiated in numerous countries where the need for stabilization is high. The use of reversible pumps turbines are widely regarded as the most cost effective solutions. They can, depending on reservoir size, deliver long term energy storage and/or boost production (turbine) or consumption (pump) in peak power situations. Pump-turbines often involve problematic S-shaped and instability regions in their machine char- acteristics. Thus, while may solve some problems in the grid, the operation and control can lead to other problems including severe self-excited oscillation in the hydromechanical system. At off design conditions, neither the distributor, nor the draft tube works properly and give awk- ward boundary conditions to the impeller. In addi- tion there is a strong interaction between the runner and these parts. Flow features such as separation and recirculation occurs heavily in an unsteady manner. (Gonzalez et al. [1], Hong and Kang [2], Guo and Maruta [3], Majidi [4], Rodriguez et al. [5], Pavesi et al. [6, 9], Cavazzini et al. [7], and Feng et al. [8] ). One objective of this research is to understand the underlying physical mechanism of the pump- mode instability of a two-stages reversible-pump turbine. The pressure fluctuations will be monitored while the pump-turbine is operating at different flow rates by flush mounted micro pressure transducers in the guide vanes, in the bladed return channel and in the inflow. The flow pattern was also analysed by high- speed flow visualizations, using injected air bubbles. A quite uniform flow pattern in the vaned channels was evidenced at the normal operating range. Whereas at part load the flow is highly disturbed backflow and vortices during the rotating stall. Moreover, the unsteady numerical flow fields were analyzed by the commercial code ANSYS CFX 14.0, to highlight the fluid-dynamical characteristic of the instabilities and investigate their origin. The evolution of rotating stall was identified by these analyses and compared with the experimental results. The spectral analysis of the unsteady pressure, obtained in the diffuser and in the impeller by the numerical results, helped to underline the role of the rotor stator interaction (RSI) in the develop- ment of the instabilities.},

keywords = {Francis-type Reversible Turbine, Hump-instability, part load},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{pop00027,

title = {Pressure instabilities in a vaned centrifugal pump},

author = {Giovanna Cavazzini and Giorgio Pavesi and Guido Ardizzon},

url = {http://pia.sagepub.com/content/225/7/930.short http://journals.sagepub.com/doi/10.1177/0957650911410643},

doi = {10.1177/0957650911410643},

issn = {0957-6509},

year  = {2011},

date = {2011-01-01},

booktitle = {ETC 9 - 9th European Turbomachinery Conference},

volume = {225},

issue = {7},

pages = {1-10},

publisher = {pia.sagepub.com},

abstract = {This article reports the acoustic and fluid-dynamical analyses of large-scale instabil- ities in a vaned centrifugal pump. The unsteady pressure fields at full/part load were measured by dynamic piezoresistive transducers placed at the impeller discharge and on an instrumented diffuser vane. To spectrally characterize the inception and the evolution of the unsteady phe- nomena, spectral analyses of the pressure signals were carried out both in frequency and time– frequency domains. Numerical analyses were carried out on the same pump with the help of the commercial code CFX. All the computations were performed using the unsteady ‘transient’ model with a time step corresponding to about 1? of the impeller rotation. The turbulence was modelled by the detached eddy simulation model. Numerical pressure signals were compared with the experimental ones to verify the development of the same pressure instabilities. The unsteady numerical flow fields were analysed to study the fluid-dynamical evolution of the instabilities},

note = {<b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G.; Pavesi, G.; Ardizzon, G.)<br/></b><br/><b>From Duplicate 1 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/><b>From Duplicate 1 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/><b>From Duplicate 1 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G.; Pavesi, G.; Ardizzon, G.)<br/></b><br/><b>From Duplicate 1 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G.; Pavesi, G.; Ardizzon, G.)<br/></b><br/><b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/>Query date: 2017-05-06<br/><br/><b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/>Query date: 2017-05-06<br/><br/><b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/>Query date: 2017-05-06<br/><br/><b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G.; Pavesi, G.; Ardizzon, G.)<br/></b><br/><b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/><b>From Duplicate 1 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/><b>From Duplicate 1 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G.; Pavesi, G.; Ardizzon, G.)<br/></b><br/><b>From Duplicate 1 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G.; Pavesi, G.; Ardizzon, G.)<br/></b><br/><b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/>Query date: 2017-05-06<br/><br/><b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/>Query date: 2017-05-06<br/><br/><b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/>Query date: 2017-05-06<br/><br/><b>From Duplicate 3 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, Giovanna; Pavesi, Giorgio; Ardizzon, Guido)<br/></b><br/><b>From Duplicate 1 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/><b>From Duplicate 1 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/><b>From Duplicate 1 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G.; Pavesi, G.; Ardizzon, G.)<br/></b><br/><b>From Duplicate 1 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G.; Pavesi, G.; Ardizzon, G.)<br/></b><br/><b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/>Query date: 2017-05-06<br/><br/><b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/>Query date: 2017-05-06<br/><br/><b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/>Query date: 2017-05-06<br/><br/><b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, Giovanna; Pavesi, Giorgio; Ardizzon, Guido)<br/></b><br/><b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/>And Duplicate 3 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/><b>From Duplicate 1 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/><b>From Duplicate 1 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G.; Pavesi, G.; Ardizzon, G.)<br/></b><br/><b>From Duplicate 1 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G.; Pavesi, G.; Ardizzon, G.)<br/></b><br/><b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/>Query date: 2017-05-06<br/><br/><b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/>Query date: 2017-05-06<br/><br/><b>From Duplicate 2 (<i>Pressure instabilities in a vaned centrifugal pump</i> - Cavazzini, G; Pavesi, G; Ardizzon, G)<br/></b><br/>Query date: 2017-05-06},

keywords = {Blockage, Centrifugal pump, Francis-type Reversible Turbine, hump-instability region, part load, Return channel, Rotating Instability, Unforced unsteadiness},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Dazin2010,

title = {Rotating Instabilities in a Radial Vaneless Diffuser},

author = {Antoine Dazin and Giovanna Cavazzini and Giorgio Pavesi and Patrick Dupont and Guido Ardizzon and Guy CAIGNAERT and Gérard Bois },

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 = {1-6},

abstract = {The paper reports on the flow field in a vaneless diffuser of a radial flow pump at partial flow conditions. Experimental data were obtained within the diffuser using 2D/3C high repetition rate PIV coupled with unsteady pressure transducers. The pressure measurements were acquired on the shroud wall of the vaneless diffuser and on the suction pipe of the pump. Pressure signals were investigated by frequency and time frequency analyses. PIV results were post processed using original averaging methods. Two partial flow rates were investigated in detail in this paper. Rotating instability occurred for both flow rates. A single instability mode was identified for the lowest flow rate whereas, for the higher one two competitive modes were recognized intermittently. Their spatiotemporal characteristics were described in the paper.},

keywords = {Analysis, Flow instability, Numerical Analysis, part load, PIV, radial flow pump, spectral, vaneless diffuser},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{pop00063,

title = {Rotating Instabilities in a Radial Vaneless Diffuser - Part I: High Speed Stereoscopic Measurements},

author = {Antoine Dazin and Giovanna Cavazzini and Giorgio Pavesi and Patrick Dupont and Sebastien Coudert and Guido Ardizzon and Guy Caignaert and Gérard Bois },

url = {http://www.academia.edu/download/39639243/Rotating_instabilities_in_a_radial_vaneless_diffuser_Part_I_High_speed_stereoscopic_measurements.pdf},

isbn = {9783851250367},

year  = {2009},

date = {2009-01-01},

urldate = {2009-01-01},

booktitle = {8th Conference on Turbomachinery, Fluid Dynamics and Thermodynamics},

pages = {1-10},

abstract = {The paper refers to the behaviour of a vaneless diffuser of a radial flow pump in partial flow operating conditions. Experimental data have been obtained within the diffuser using 2D/3C high repetition rate PIV coupled with unsteady pressure transducers. The pressure measurements were acquired on the shroud wall of the vaneless diffuser and on the suction pipe of the pump. Various operating conditions were investigated in order to characterize the unsteady flow field especially at partial flow rates when the rotating instability appears. A Fourier analysis has been carried out both on the pressure and velocity signals to identify the characteristics of the rotating instability. Averaged results of the PIV data allowed the topology of the instability cells to be visualized and described. Nomenclature},

keywords = {Analysis, Flow instability, Numerical Analysis, part load, PIV, radial flow pump, spectral, vaneless diffuser},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{ArdizzonGPavesiG1999,

title = {Analisi Sperimentale della Caratteristica Interna di una Turbomacchina ai Carichi Parziali},

author = {Guido Ardizzon, Giorgio Pavesi},

year  = {1999},

date = {1999-01-01},

urldate = {1999-01-01},

booktitle = {MIS - MAC VI Metodi di Sperimentazione nelle Macchine},

pages = {63-74},

publisher = {SGE - Padova},

abstract = {Direct and reverse operation of three radial flow turbomachines at part load conditions are investigated in order to evaluate the energy exchange between runner and fluid. Recirculation phenomena that occur at low flowrates interact with the blade passages with a net exchange momentum which has to be supplied by the impeller in pump mode, while reducing the one transmitted to the rotor by the fluid in turbine mode. Partial flow characteristic curves are also influenced in both operation modes. In order to highlight the role played by backward flows on the performances, the runnerfluid energy transfer has been evaluated from both velocity and power measurements. In particular, leakage and windage losses have been segregated and measured. The experimental results show that when recirculation phenomena occur within the runner, the energy exchange obtained from angular momentum equation only represents the work done by the driving motor on the discharge flowrate in pump mode. While it represents the net energy transferred to the rotor by the driving flowrate in reverse mode, that is the mechanical work available on the shaft when internal recirculation losses are taken into account.},

keywords = {Losses, part load, Pump, Pump as Turbine, Turbine},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{PavesiGArdizzonG1997,

title = {Influenza degli Elementi Statorici sulle Prestazioni ai Carichi Parziali delle Turbomacchine Operatrici Centrifughe},

author = {Guido Ardizzon and Giuseppe Ventrone and Giorgio Pavesi},

editor = {SGE},

year  = {1997},

date = {1997-01-01},

urldate = {1997-01-01},

booktitle = {52° Congresso Nazionale ATI},

pages = {829 - 840},

abstract = {Vengono presentati i risultati di una ricerca volta ad accertare l’influenza della geometria degli organi statorici sullo sviluppo della ricircolazione che si manifesta all’ingresso e all’uscita di una girante operatrice centrifuga nel funzionamento ai carichi parziali. Le indagini sperimentali sono state condotte su una macchina modello alla quale è stato possibile rimuovere il diffusore palettato posto a valle della girante e modificare la geometria all’aspirazione inserendo, dapprima una schiera di pale radiali statoriche, e successivamente un diaframma con diametro interno opportuno. Parallelamente all’esplorazione del campo di moto all’ingresso e all’uscita della girante mediante sonde 3-D è stata eseguita una analisi del rumore rilevato da un trasduttore di pressione piezoelettrico posto a filo della corrente. Dal confronto dei risultati ottenuti con i due sistemi di misura è stato possibile appurare l’influenza degli elementi statorici sull’innesco della ricircolazione all’ingresso e all’uscita della girante, distinguere l’insorgere delle due forme di instabilità funzionale e valutare la loro interferenza sulle prestazioni della macchina.},

keywords = {part load, Pump, Pump Design},

pubstate = {published},

tppubtype = {inproceedings}

}