Publications

@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}

}

@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}

}

@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{pop00020,

title = {Numerical characterization of pressure instabilities in a vaned centrifugal pump under partload condition},

author = {Jun Yang and Giorgio Pavesi and Giovanna Cavazzini and Shouqi Q. Yuan},

url = {http://iopscience.iop.org/article/10.1088/1757-899X/52/2/022044/meta http://stacks.iop.org/1757-899X/52/i=2/a=022044?key=crossref.51f7846194288a9a6286cc200d28e156},

doi = {10.1088/1757-899X/52/2/022044},

issn = {17578981},

year  = {2013},

date = {2013-01-01},

urldate = {2013-01-01},

booktitle = {IOP Conference Series: Materials Science and Engineering},

volume = {52},

issue = {2},

pages = {022-044},

publisher = {iopscience.iop.org},

abstract = {This paper studies the hysteresis/saddle phenomena of the head-drop in a scaled model pump turbine using CFD methods. This lag was induced by complicated flow patterns, which influenced the reliability of rotating machine that was analysed by a commercial code with DES model for computing turbulence. Analyses were carried out on the pressure signals both in frequency and time-frequency domains at full and part load conditions. The results highlighted the remarkable interaction between the unsteady structures in diffuser and return. © Published under licence by IOP Publishing Ltd.},

keywords = {Francis-type Reversible Turbine, hump-instability region, Pressure fluctuations},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Cavazzini2012a,

title = {Influence of the Return Channel Geometry on the Perfomance Stability of a Centrifugal Pump},

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

year  = {2012},

date = {2012-01-01},

urldate = {2012-01-01},

booktitle = {14th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, ISROMAC-14 February 27th - March 2nd, 2012},

issue = {January 2016},

pages = {1-8},

abstract = {The paper reports on fluid-dynamical investigations of largescale instabilities in a radial multistage pump with a vaneless return channel. To establish a relation between the flow field structure at high/partial load and acoustic radiation, numerical analyses were carried out by means of the commercial code CFX 12.0 on the entire machine so as to study the unsteady phenomena developing in the pump. All the computations were performed using the unsteady "transient" model. The time step for the calculation will be chosen according to a rotation of the runner of about 1 degree. Turbulence will be modelled by DES model. To validate the numerical analysis, numerical pressure signals were compared with experimental signals. Further numerical analyses were also carried out on simplified configurations in order to determine the geometrical and fluid-dynamical parameters affecting the development of the identified unsteady phenomena.},

keywords = {Francis-type Reversible Turbine, hump-instability region},

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{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}

}

@inproceedings{Pavesi2009c,

title = {Experimental Charactization of Rotating Instabilities in a Centrifugal Pump},

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

url = {https://www.researchgate.net/profile/Giorgio_Pavesi/publication/277598782_Experimental_characterization_of_rotating_instabilities_in_a_centrifugal_pump/links/556e803208aefcb861db9cbc.pdf},

year  = {2009},

date = {2009-01-01},

urldate = {2009-01-01},

booktitle = {ETC 8 - 8th European Turbomachinery Conference},

abstract = {The paper presents experimental investigations of large-scale instabilities 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 and two configurations with a vaneless and a vaned diffuser, were utilized in the study, as well as several angular and radial transducer positions at design and at off design flow rates. The spectra analyses of the pressure signals were carried out both in frequency and time-fre- quency domains to identified precursors, inception and evolution of the pressure instabilities. Be- cause of the non-linearity of the unsteady phenomena developing in the pump, 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. The results highlighted the existence of an asymmetrical rotating pressure structure at the im- peller discharge, having a fluid-dynamical origin and propagating both in the radial and circumferential direction, inside and downstream of the impeller. Nomenclature},

note = {Query date: 2017-05-06},

keywords = {Francis-type Reversible Turbine, hump-instability region},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{pop00041,

title = {Rotor-stator interactions in a radial flow pump},

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

year  = {2007},

date = {2007-01-01},

urldate = {2007-01-01},

booktitle = {Proceedings of the 7th European Conference on Turbomachinery: Fluid Dynamics and Thermodynamics, ETC 2007},

abstract = {The paper refers to the analysis of interactions between the impeller and the vaned dif- fuser of a radial flow pump. It mainly focuses on the flow within one blade passage of a vaned diffuser in four operating conditions. The 2D/2C PIV technique was used to analyze the diffuser flow field in various measuring planes in the hub to shroud direction, for one relative impeller position in the diffuser frame. These experimental results were compared to numerical data obtained with the help of CFX computer code.},

note = {<b>From Duplicate 1 (<i>Rotor-stator interactions in a radial flow pump</i> - Pavesi, G; Cavazzini, G; Dupont, P; Coudert, S.; Caignaert, G.; Bois, G.; Ardizzon, G.)<br/></b><br/>Query date: 2017-05-06<br/><br/><b>From Duplicate 2 (<i>Rotor-stator interactions in a radial flow pump</i> - Pavesi, Giorgio; Cavazzini, Giovanna; Dupont, Patrick; Coudert, Sebastien; Caignaert, Guy; Bois, Gérard; Ardizzon, Guido)<br/></b><br/><b>From Duplicate 2 (<i>Rotor-stator interactions in a radial flow pump</i> - Pavesi, G; Cavazzini, G; Dupont, P; Coudert, S.; Caignaert, G.; Bois, G.; Ardizzon, G.)<br/>And Duplicate 3 (<i>Rotor-stator interactions in a radial flow pump</i> - Pavesi, G; Cavazzini, G; Dupont, P; Coudert, S.; Caignaert, G.; Bois, G.; Ardizzon, G.)<br/>And Duplicate 4 (<i>Rotor-stator interactions in a radial flow pump</i> - Pavesi, G; Cavazzini, G; Dupont, P; Coudert, S.; Caignaert, G.; Bois, G.; Ardizzon, G.)<br/></b><br/>Query date: 2017-05-06},

keywords = {Francis-type Reversible Turbine, Pump, Pump as Turbine, Rotor Stator Interaction},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Pavesi2006a,

title = {Experimental and computation investigation of the rotating instability in a centrifugal pump impeller},

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

year  = {2006},

date = {2006-01-01},

urldate = {2006-01-01},

booktitle = {Proceedings of ISROMAC2006: The Eleventh International Symposium on Transport Phenomena and Dynamics of Rotating Machinery},

pages = {1-10},

abstract = {The paper reports on experimental and numerical investigations aimed at understanding the mechanisms of rotating instabilities in a centrifugal pump. The phenomena of rotating instabilities in the impeller were first identified with an experimental study. Afterward an unsteady numerical analysis was applied to confirm the phenomena and to detail the mechanisms behind them. The experimental study was conducted with high-response pressure measurements at three planes, at the pump, and at diffuser inflows. The numerical investigation, for the entire pump, was performed with an unsteady 3-D Navier-Stokes method. Turbulence was modelled both by the k-ω transport equations model and Reynolds Stress Model. The effects of the tip leakage flow were considered by meshing the tip clearance between rotor blade and casing The current study reveals that a vortex structure forms near the leading edge plane. The formation and movement of this vortex seem to be the main causes of unsteadiness when rotating instability develops. This unsteady phenomenon was highlighted both at design flow rate and at low flow rates. The azimuthal distributions exhibited no significant uniformities and the amplitude of this non-uniformity was sensitive to the flow rate.},

keywords = {Francis-type Reversible Turbine, hump-instability region},

pubstate = {published},

tppubtype = {inproceedings}

}

@inproceedings{Pavesi2005b,

title = {Rotating Instability in a Centrifugal Pump Impeller},

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

url = {http://www.scopus.com/scopus/inward/record.url?eid=2-s2.0-33645960402&partnerID=40&rel=R7.0.0},

doi = {10.1115/imece2005-79937},

issn = {08888116},

year  = {2005},

date = {2005-01-01},

urldate = {2005-01-01},

booktitle = {2005 ASME International Mechanical Engineering Congress and Exposition},

volume = {261 FED},

issue = {1},

pages = {1-9},

abstract = {The objective of the study was the experimental and computational investigation of the unsteady flow in the centrifugal pumps. This paper analysed the effect of the vaneless stator interference on the exit flow field of a radial pump operated in the DIM facility. High-response pressure transducers were used to determine unsteady pressure field at three planes at the pump and at diffuser inflows. The experimental data showed that unsteady pressure disturbances modes change when the flow was reduced. Detailed analysis showed that disturbances occur at distinct frequencies and that these rotated in the circumferential direction. Comparison of the pressure signals measured at two circumferential locations on the casing confirmed the characteristic frequency pattern to be a so called "rotating instability". This unsteady phenomenon was highlighted both at design flow rate and at low flow rates. The azimuthal distributions exhibited significant nonuniformities. The amplitude of this non-uniformity was sensitive to the flow rate. A simple model showed that, contrary to the common belief, the transport of the vane wake and secondary flows across the rotor was not enough to explain the magnitude of the variations. In this paper numerical investigations of the unsteady three-dimensional flow through the pump stage were also presented. Turbulence was modelled both by the k-? transport equations model, and Reynolds Stress Model based on the coequation. The effects of the tip leakage flow were considered by meshing the tip clearance between rotor blade and casing. Results showed the jet-wake flow pattern induced an unstable vortex, which influenced flow discharging from the adjacent passage and destabilised jet-wake flow in the passage. Both calculations and measurements detected the periodic fluctuations at impeller discharge which were found to be coherent from blade to blade and possessed a rich harmonic content. Copyright 2005 by ASME.},

keywords = {Francis-type Reversible Turbine, Pump},

pubstate = {published},

tppubtype = {inproceedings}

}