Documents disponibles écrits par cet auteur

Experimental Evidence of Hydroacoustic Pressure Waves in a Francis Turbine Elbow Draft Tube for Low Discharge Conditions / Jorge Arpe in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 8 (Août 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 8 (Août 2009) . - 09 p. Titre : Experimental Evidence of Hydroacoustic Pressure Waves in a Francis Turbine Elbow Draft Tube for Low Discharge Conditions Type de document : texte imprimé Auteurs : Jorge Arpe, Auteur ; Nicolet, Christophe, Auteur ; François Avellan, Auteur Année de publication : 2009 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : three-dimensional  unsteady  flow;  Francis  turbine Résumé : The complex three-dimensional unsteady flow developing in the draft tube of a Francis turbine is responsible for pressure fluctuations, which could prevent the whole hydropower plant from operating safely. Indeed, the Francis draft tube is subjected to inlet swirling flow, divergent cross section, and the change of flow direction. As a result, in low discharge off-design operating conditions, a cavitation helical vortex, so-called the vortex rope develops in the draft tube and induces pressure fluctuations in the range of 0.2–0.4 times the runner frequency. This paper presents the extensive unsteady wall pressure measurements performed in the elbow draft tube of a high specific speed Francis turbine scale model at low discharge and at usual plant value of the Thoma cavitation number. The investigation is undertaken for operating conditions corresponding to low discharge, i.e., 0.65–0.85 times the design discharge, which exhibits pressure fluctuations at surprisingly high frequency value, between 2 and 4 times the runner rotation frequency. The pressure fluctuation measurements performed with 104 pressure transducers distributed on the draft tube wall, make apparent in the whole draft tube a fundamental frequency value at 2.5 times the runner frequency. Moreover, the modulations between this frequency with the vortex rope precession frequency are pointed out. The phase shift analysis performed for 2.5 times the runner frequency enables the identification of a pressure wave propagation phenomenon and indicates the location of the corresponding pressure fluctuation excitation source in the elbow; hydroacoustic waves propagate from this source both upstream and downstream the draft tube. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Experimental Evidence of Hydroacoustic Pressure Waves in a Francis Turbine Elbow Draft Tube for Low Discharge Conditions [texte imprimé] / Jorge Arpe, Auteur ; Nicolet, Christophe, Auteur ; François Avellan, Auteur . - 2009 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 8 (Août 2009) . - 09 p. Mots-clés : three-dimensional  unsteady  flow;  Francis  turbine Résumé : The complex three-dimensional unsteady flow developing in the draft tube of a Francis turbine is responsible for pressure fluctuations, which could prevent the whole hydropower plant from operating safely. Indeed, the Francis draft tube is subjected to inlet swirling flow, divergent cross section, and the change of flow direction. As a result, in low discharge off-design operating conditions, a cavitation helical vortex, so-called the vortex rope develops in the draft tube and induces pressure fluctuations in the range of 0.2–0.4 times the runner frequency. This paper presents the extensive unsteady wall pressure measurements performed in the elbow draft tube of a high specific speed Francis turbine scale model at low discharge and at usual plant value of the Thoma cavitation number. The investigation is undertaken for operating conditions corresponding to low discharge, i.e., 0.65–0.85 times the design discharge, which exhibits pressure fluctuations at surprisingly high frequency value, between 2 and 4 times the runner rotation frequency. The pressure fluctuation measurements performed with 104 pressure transducers distributed on the draft tube wall, make apparent in the whole draft tube a fundamental frequency value at 2.5 times the runner frequency. Moreover, the modulations between this frequency with the vortex rope precession frequency are pointed out. The phase shift analysis performed for 2.5 times the runner frequency enables the identification of a pressure wave propagation phenomenon and indicates the location of the corresponding pressure fluctuation excitation source in the elbow; hydroacoustic waves propagate from this source both upstream and downstream the draft tube. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Investigation of control strategies for variable-speed pump-turbine units by using a simplified model of the converters / Pannatier, Yves in IEEE transactions on industrial electronics, Vol. 57 N° 9 (Septembre 2010) 

Public ISBD [article]  in IEEE transactions on industrial electronics > Vol. 57 N° 9 (Septembre 2010) . - pp. 3039 - 3049 Titre : Investigation of control strategies for variable-speed pump-turbine units by using a simplified model of the converters Type de document : texte imprimé Auteurs : Pannatier, Yves, Auteur ; Kawkabani, Basile, Auteur ; Nicolet, Christophe, Auteur Année de publication : 2011 Article en page(s) : pp. 3039 - 3049 Note générale : Génie électrique Langues : Anglais (eng) Mots-clés : Control  strategy  Dynamic  simulation  Induction  machine  Power  converter  Pulsewidth  modulation  (PWM)  Pump  turbine  Torque  Variable  speed Index. décimale : 621.38 Dispositifs électroniques. Tubes à électrons. Photocellules. Accélérateurs de particules. Tubes à rayons X Résumé : This paper presents the modeling, simulation, and analysis of the dynamic behavior of a fictitious 2 × 320 MW variable-speed pump-turbine power plant, including a hydraulic system, electrical equipment, rotating inertias, and control systems. The modeling of the hydraulic and electrical components of the power plant is presented. The dynamic performances of a control strategy in generating mode and one in pumping mode are investigated by the simulation of the complete models in the case of change of active power set points. Then, a pseudocontinuous model of the converters feeding the rotor circuits is described. Due to this simplification, the simulation time can be reduced drastically (approximately factor 60). A first validation of the simplified model of the converters is obtained by comparison of the simulated results coming from the simplified and complete models for different modes of operation of the power plant. Experimental results performed on a 2.2-kW low-power test bench are also compared with the simulated results coming from both complete and simplified models related to this case and confirm the validity of the proposed simplified approach for the converters. DEWEY : 621.38 ISSN : 0278-0046 En ligne : http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=5342518 [article] Investigation of control strategies for variable-speed pump-turbine units by using a simplified model of the converters [texte imprimé] / Pannatier, Yves, Auteur ; Kawkabani, Basile, Auteur ; Nicolet, Christophe, Auteur . - 2011 . - pp. 3039 - 3049. Génie électrique Langues : Anglais (eng) in IEEE transactions on industrial electronics > Vol. 57 N° 9 (Septembre 2010) . - pp. 3039 - 3049 Mots-clés : Control  strategy  Dynamic  simulation  Induction  machine  Power  converter  Pulsewidth  modulation  (PWM)  Pump  turbine  Torque  Variable  speed Index. décimale : 621.38 Dispositifs électroniques. Tubes à électrons. Photocellules. Accélérateurs de particules. Tubes à rayons X Résumé : This paper presents the modeling, simulation, and analysis of the dynamic behavior of a fictitious 2 × 320 MW variable-speed pump-turbine power plant, including a hydraulic system, electrical equipment, rotating inertias, and control systems. The modeling of the hydraulic and electrical components of the power plant is presented. The dynamic performances of a control strategy in generating mode and one in pumping mode are investigated by the simulation of the complete models in the case of change of active power set points. Then, a pseudocontinuous model of the converters feeding the rotor circuits is described. Due to this simplification, the simulation time can be reduced drastically (approximately factor 60). A first validation of the simplified model of the converters is obtained by comparison of the simulated results coming from the simplified and complete models for different modes of operation of the power plant. Experimental results performed on a 2.2-kW low-power test bench are also compared with the simulated results coming from both complete and simplified models related to this case and confirm the validity of the proposed simplified approach for the converters. DEWEY : 621.38 ISSN : 0278-0046 En ligne : http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=5342518

One-dimensional analysis of full load draft tube surge / Changkun Chen in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 4 (Avril 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 4 (Avril 2008) . - 6 p. Titre : One-dimensional analysis of full load draft tube surge Type de document : texte imprimé Auteurs : Changkun Chen, Auteur ; Nicolet, Christophe, Auteur ; Koichi Yonezawa, Auteur Année de publication : 2009 Article en page(s) : 6 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Flow  (dynamics);  stress;  diffusers;  equations;  surges;  pressure;  cavities Résumé : One-dimensional stability analysis of a hydraulic system composed of a penstock, a runner, and a draft tube was carried out to determine the cause of the full load draft tube surge. It is assumed that the cavity volume at the runner exit is a function of the pressure at the vortex core evaluated from the instantaneous local pressure at the runner exit and an additional pressure decrease due to the centrifugal force on the swirling flow. It was found that the diffuser effect of the draft tube has a destabilizing effect over all flow rates, while the swirl effects stabilize∕destabilize the system at larger∕smaller flow rates than the swirl-free flow rate. Explanations of the destabilizing mechanism are given for the diffuser and swirl flow effects. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27307 [...] [article] One-dimensional analysis of full load draft tube surge [texte imprimé] / Changkun Chen, Auteur ; Nicolet, Christophe, Auteur ; Koichi Yonezawa, Auteur . - 2009 . - 6 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 4 (Avril 2008) . - 6 p. Mots-clés : Flow  (dynamics);  stress;  diffusers;  equations;  surges;  pressure;  cavities Résumé : One-dimensional stability analysis of a hydraulic system composed of a penstock, a runner, and a draft tube was carried out to determine the cause of the full load draft tube surge. It is assumed that the cavity volume at the runner exit is a function of the pressure at the vortex core evaluated from the instantaneous local pressure at the runner exit and an additional pressure decrease due to the centrifugal force on the swirling flow. It was found that the diffuser effect of the draft tube has a destabilizing effect over all flow rates, while the swirl effects stabilize∕destabilize the system at larger∕smaller flow rates than the swirl-free flow rate. Explanations of the destabilizing mechanism are given for the diffuser and swirl flow effects. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27307 [...]

Parametric study of water column separation in Francis pump-turbine draft tube / Nicolet, Christophe in La Houille blanche, N° 3 (Juin 2012) 

Public ISBD [article]  in La Houille blanche > N° 3 (Juin 2012) . - pp. 44-50 Titre : Parametric study of water column separation in Francis pump-turbine draft tube Type de document : texte imprimé Auteurs : Nicolet, Christophe, Auteur ; Sébastien Alligne, Auteur ; Bergant, Anton, Auteur Année de publication : 2012 Article en page(s) : pp. 44-50 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Transient  analysis  Pump-turbine  Cavitation  Water  hammer  Hydroacoustic  modeling Résumé : The paper presents the modelling, simulation and analysis of the transient behaviour of a 340 MW pump-turbine in case of emergency shutdown in generation mode with particular attention to the possible draft tube water column separation. First, the model of a pumped storage power plant with simplified layout is setup with the EPFL software SIMSEN. This model includes a penstock feeding one 340 MW pump-turbine with the related rotating inertia and a tailrace tunnel. The model of the tailrace tunnel allows for water column separation simulation. Thus, the related SIMSEN model is introduced and validations are briefly presented. Then, the influence of the tailrace tunnel length and diameter on the minimum pressure in the draft tube is investigated through a parametric study first without water column separation model. Finally, the simulation results of the transient behaviour of the pump-turbine with downstream water column separation are presented for different degree of severity triggered by the submergence and the tailrace tunnel dimensions taken as parameters. ISSN : 0018-6368 En ligne : http://www.shf-lhb.org/index.php?option=com_article&access=standard&Itemid=129&u [...] [article] Parametric study of water column separation in Francis pump-turbine draft tube [texte imprimé] / Nicolet, Christophe, Auteur ; Sébastien Alligne, Auteur ; Bergant, Anton, Auteur . - 2012 . - pp. 44-50. Hydraulique Langues : Anglais (eng) in La Houille blanche > N° 3 (Juin 2012) . - pp. 44-50 Mots-clés : Transient  analysis  Pump-turbine  Cavitation  Water  hammer  Hydroacoustic  modeling Résumé : The paper presents the modelling, simulation and analysis of the transient behaviour of a 340 MW pump-turbine in case of emergency shutdown in generation mode with particular attention to the possible draft tube water column separation. First, the model of a pumped storage power plant with simplified layout is setup with the EPFL software SIMSEN. This model includes a penstock feeding one 340 MW pump-turbine with the related rotating inertia and a tailrace tunnel. The model of the tailrace tunnel allows for water column separation simulation. Thus, the related SIMSEN model is introduced and validations are briefly presented. Then, the influence of the tailrace tunnel length and diameter on the minimum pressure in the draft tube is investigated through a parametric study first without water column separation model. Finally, the simulation results of the transient behaviour of the pump-turbine with downstream water column separation are presented for different degree of severity triggered by the submergence and the tailrace tunnel dimensions taken as parameters. ISSN : 0018-6368 En ligne : http://www.shf-lhb.org/index.php?option=com_article&access=standard&Itemid=129&u [...]