Documents disponibles écrits par cet auteur

Analysis of the deterministic unsteady flow in a low-speed axial fan with inlet guide vanes / Jesús Manuel Fernández Oro in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 3 (Mars 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 12 p. Titre : Analysis of the deterministic unsteady flow in a low-speed axial fan with inlet guide vanes Type de document : texte imprimé Auteurs : Jesús Manuel Fernández Oro, Auteur ; Katia María Argüelles Díaz, Auteur ; Carlos Santolaria Morros, Auteur Année de publication : 2009 Article en page(s) : 12 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Periodic  stator-rotor  interaction;  low-speed  axial  fan;  inlet  guide  vanes;  fluctuation Résumé : This paper is conceived as an extension in the analysis of the periodic stator-rotor interaction in a low-speed axial fan with inlet guide vanes. Here, the present work focuses on the deterministic fluctuations that occur in the axial gap between the blade rows. In particular, we present experimental data on the phase averaged velocity in the stator frame of reference. Detailed measurements of the flow field were obtained using hot-wire anemometry in a traverse sector that covered the whole span of the stage for a complete stator pitch. The blade-to-blade velocity gradient in the rotor passage is observed as an unsteady flow in the stator frame of reference due to the relative motion of the blades. As a consequence, this periodic fluctuation is superimposed on the steady vane-to-vane velocity distribution, resulting in a nonuniform unsteadiness with additional phase-dependent wake-blockage interaction. This phase-dependent interaction is determined by the difference between the overall deterministic fluctuation and the rotating spatial blade-to-blade distribution, when the latter is accurately transformed to the stator reference frame. The results revealed that high unsteadiness in the tip region is mainly derived from the radial increase of the blade-to-blade nonuniformities in the rotor, whereas the wake-blockage interaction exhibits a spanwise uniform distribution. Hence, the hub-to-tip torsion of the blades is responsible for setting off a major spatial distortion between the rows. Complementarily, we observed that a reduction in the rows’ spacing or an increase in the blade loadings leads to a higher wake-blockage interaction, modifying the impingement of the incoming stator wakes. In addition, the deterministic stresses were calculated by time averaging the phase-dependent velocity correlations and compared to the turbulent stresses. The deterministic stresses were also segregated in temporal, spatial, and spatial-temporal correlations in order to analyze the dominant mechanisms involved in their generation. At this point, the deterministic kinetic energy levels were found to be generally lower than turbulent kinetic energy levels, with both temporal and spatial correlations being the most significant terms of the tensor. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Analysis of the deterministic unsteady flow in a low-speed axial fan with inlet guide vanes [texte imprimé] / Jesús Manuel Fernández Oro, Auteur ; Katia María Argüelles Díaz, Auteur ; Carlos Santolaria Morros, Auteur . - 2009 . - 12 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 3 (Mars 2008) . - 12 p. Mots-clés : Periodic  stator-rotor  interaction;  low-speed  axial  fan;  inlet  guide  vanes;  fluctuation Résumé : This paper is conceived as an extension in the analysis of the periodic stator-rotor interaction in a low-speed axial fan with inlet guide vanes. Here, the present work focuses on the deterministic fluctuations that occur in the axial gap between the blade rows. In particular, we present experimental data on the phase averaged velocity in the stator frame of reference. Detailed measurements of the flow field were obtained using hot-wire anemometry in a traverse sector that covered the whole span of the stage for a complete stator pitch. The blade-to-blade velocity gradient in the rotor passage is observed as an unsteady flow in the stator frame of reference due to the relative motion of the blades. As a consequence, this periodic fluctuation is superimposed on the steady vane-to-vane velocity distribution, resulting in a nonuniform unsteadiness with additional phase-dependent wake-blockage interaction. This phase-dependent interaction is determined by the difference between the overall deterministic fluctuation and the rotating spatial blade-to-blade distribution, when the latter is accurately transformed to the stator reference frame. The results revealed that high unsteadiness in the tip region is mainly derived from the radial increase of the blade-to-blade nonuniformities in the rotor, whereas the wake-blockage interaction exhibits a spanwise uniform distribution. Hence, the hub-to-tip torsion of the blades is responsible for setting off a major spatial distortion between the rows. Complementarily, we observed that a reduction in the rows’ spacing or an increase in the blade loadings leads to a higher wake-blockage interaction, modifying the impingement of the incoming stator wakes. In addition, the deterministic stresses were calculated by time averaging the phase-dependent velocity correlations and compared to the turbulent stresses. The deterministic stresses were also segregated in temporal, spatial, and spatial-temporal correlations in order to analyze the dominant mechanisms involved in their generation. At this point, the deterministic kinetic energy levels were found to be generally lower than turbulent kinetic energy levels, with both temporal and spatial correlations being the most significant terms of the tensor. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Extended angular range of a three-hole cobra pressure probe for incompressible flow / Katia María Argüelles Díaz in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 10 (Octobre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 10 (Octobre 2008) . - 6 p. Titre : Extended angular range of a three-hole cobra pressure probe for incompressible flow Type de document : texte imprimé Auteurs : Katia María Argüelles Díaz, Auteur ; Jesús Manuel Fernández Oro, Auteur ; Eduardo Blanco Marigorta, Auteur Année de publication : 2009 Article en page(s) : 6 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Three-hole  cobra;  angular  range;  calibration;  data  reduction  method Résumé : This paper analyzes the operative characteristics of a three-hole cobra type probe especially designed to attain an angular range higher than 180deg for planar turbulent flows. A new calibration and data reduction method are also introduced, discriminating three different zones inside the angular range of the calibration. This methodology improves the probe performance, extending its operative angular range from the typical ±30degto±105deg. In addition, the transmission of the uncertainty—from the pressure measurements to the flow variables—is estimated, showing reasonably low levels for the whole angular range. Furthermore, the sensibility of the probe calibration to the Reynolds number and the pitch angle is considered, and the influence of the turbulence level is outlined. Regarding these factors, the probe precision in the extended angular range is found to be similar to that of the traditional range. Finally, the probe is tested in a flow field with large variations of the incidence angle, and the results obtained with the new method are compared to those given by the traditional calibration. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27341 [...] [article] Extended angular range of a three-hole cobra pressure probe for incompressible flow [texte imprimé] / Katia María Argüelles Díaz, Auteur ; Jesús Manuel Fernández Oro, Auteur ; Eduardo Blanco Marigorta, Auteur . - 2009 . - 6 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 10 (Octobre 2008) . - 6 p. Mots-clés : Three-hole  cobra;  angular  range;  calibration;  data  reduction  method Résumé : This paper analyzes the operative characteristics of a three-hole cobra type probe especially designed to attain an angular range higher than 180deg for planar turbulent flows. A new calibration and data reduction method are also introduced, discriminating three different zones inside the angular range of the calibration. This methodology improves the probe performance, extending its operative angular range from the typical ±30degto±105deg. In addition, the transmission of the uncertainty—from the pressure measurements to the flow variables—is estimated, showing reasonably low levels for the whole angular range. Furthermore, the sensibility of the probe calibration to the Reynolds number and the pitch angle is considered, and the influence of the turbulence level is outlined. Regarding these factors, the probe precision in the extended angular range is found to be similar to that of the traditional range. Finally, the probe is tested in a flow field with large variations of the incidence angle, and the results obtained with the new method are compared to those given by the traditional calibration. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27341 [...]

Turbulence and secondary flows in an axial flow fan with variable pitch blades / Jesús Manuel Fernández Oro 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) . - 11 p. Titre : Turbulence and secondary flows in an axial flow fan with variable pitch blades Type de document : texte imprimé Auteurs : Jesús Manuel Fernández Oro, Auteur ; Rafael Ballesteros-Tajadura, Auteur ; Eduardo Blanco Marigorta, Auteur Année de publication : 2009 Article en page(s) : 11 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Secondary  flows;  pitch  blades;  axial  flow  fan Résumé : This paper analyzes the structure of turbulence and secondary flows at the exit of an axial flow fan with variable pitch blades. The influence of changing the blades’ pitch angle over the turbulent structures is assessed by means of turbulence intensity values and integral length scales, obtained by using hot-wire anemometry for several test conditions. Since total unsteadiness is composed of both periodic and random unsteadiness, it is necessary to filter deterministic unsteadiness from the raw velocity traces in order to obtain turbulence data. Consequently, coherent flow structures were decoupled and thus, levels of turbulence—rms values of random fluctuations—were determined using a filtering procedure that removes all the contributions stemming from the rotational frequency, the blade passing frequency, and its harmonics. The results, shown in terms of phase-averaged distributions in the relative frame of reference, revealed valuable information about the transport of the turbulent structures in the unsteady, deterministic flow patterns. The anisotropic turbulence generated at the shear layers of the blade wakes was identified as a major mechanism of turbulence generation, and significant links between the blade pitch angle and the wake turbulent intensity were established. In addition, the autocorrelation analysis of random fluctuations was also used to estimate integral length scales—larger eddy sizes—of turbulence, providing useful data for computational fluid dynamics applications based on large eddy simulation algorithms. Finally, contours of radial vorticity and helicity gave a detailed picture of the vortical characteristics of the flow patterns, and the definition of secondary flow as the deviation of the streamwise component from the inviscid kinematics was introduced to determine the efficiency of the blade design in the energy exchange of the rotor. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Turbulence and secondary flows in an axial flow fan with variable pitch blades [texte imprimé] / Jesús Manuel Fernández Oro, Auteur ; Rafael Ballesteros-Tajadura, Auteur ; Eduardo Blanco Marigorta, Auteur . - 2009 . - 11 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 4 (Avril 2008) . - 11 p. Mots-clés : Secondary  flows;  pitch  blades;  axial  flow  fan Résumé : This paper analyzes the structure of turbulence and secondary flows at the exit of an axial flow fan with variable pitch blades. The influence of changing the blades’ pitch angle over the turbulent structures is assessed by means of turbulence intensity values and integral length scales, obtained by using hot-wire anemometry for several test conditions. Since total unsteadiness is composed of both periodic and random unsteadiness, it is necessary to filter deterministic unsteadiness from the raw velocity traces in order to obtain turbulence data. Consequently, coherent flow structures were decoupled and thus, levels of turbulence—rms values of random fluctuations—were determined using a filtering procedure that removes all the contributions stemming from the rotational frequency, the blade passing frequency, and its harmonics. The results, shown in terms of phase-averaged distributions in the relative frame of reference, revealed valuable information about the transport of the turbulent structures in the unsteady, deterministic flow patterns. The anisotropic turbulence generated at the shear layers of the blade wakes was identified as a major mechanism of turbulence generation, and significant links between the blade pitch angle and the wake turbulent intensity were established. In addition, the autocorrelation analysis of random fluctuations was also used to estimate integral length scales—larger eddy sizes—of turbulence, providing useful data for computational fluid dynamics applications based on large eddy simulation algorithms. Finally, contours of radial vorticity and helicity gave a detailed picture of the vortical characteristics of the flow patterns, and the definition of secondary flow as the deviation of the streamwise component from the inviscid kinematics was introduced to determine the efficiency of the blade design in the energy exchange of the rotor. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Unsteady flow patterns for a double suction centrifugal pump / José González in Transactions of the ASME . Journal of fluids engineering, Vol. 131 N° 7 (Juillet 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 09 p. Titre : Unsteady flow patterns for a double suction centrifugal pump Type de document : texte imprimé Auteurs : José González, Auteur ; Jesús Manuel Fernández Oro, Auteur ; Katia M. Argüelles Díaz, Auteur Année de publication : 2009 Article en page(s) : 09 p. Note générale : fluids engineering Langues : Anglais (eng) Mots-clés : double  suction  centrifugal  pump;  Unsteady  Reynolds  Averaged  Navier–Stokes  Equations  (URANS)  calculation Résumé : The flow in a double suction centrifugal pump is presented in this paper. The static performance of the machine has been obtained in a proper test rig, and the results have been compared with equivalent numerical results from an Unsteady Reynolds Averaged Navier–Stokes Equations (URANS) calculation. In a second step, the numerical results have been exploited to get detailed information about the flow inside the turbomachine. The main goal of the study is, on one hand, the validation of the numerical procedure proposed and, on the other hand, the detailed flow-field analysis for the machine, which points out the possibilities and drawbacks of the pump design. For a double suction machine, the inlet flow is characterized by the existence of a particular geometry that tries to force a uniform flow, at least for the nominal flow rate. On the contrary, at off-design conditions the lack of uniformity produces an unsteady incidence that gives rise to strong hydraulic loading variations. Instantaneous and average pressure fields have been analyzed in this paper to study the evolution of such inlet flow unsteadiness throughout the impeller and the volute. The analysis of both static and dynamic effects on the pump shaft has been carried out from the numerical calculation of the radial forces. The results have shown that the performance of the double suction centrifugal pump is suitable for typical design conditions. The best operation point or nominal flow rate is found to be at φ=0.274, which turns out to produce a specific speed ωS=1.25, well in the range for centrifugal impellers. This operating point is also found to be the one with better efficiency and with better flow characteristics, regarding the axisymmetry of the flow pattern and the fluid forces obtained. However, some particular features produce also interesting results for off-design operating points. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] Unsteady flow patterns for a double suction centrifugal pump [texte imprimé] / José González, Auteur ; Jesús Manuel Fernández Oro, Auteur ; Katia M. Argüelles Díaz, Auteur . - 2009 . - 09 p. fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 131 N° 7 (Juillet 2009) . - 09 p. Mots-clés : double  suction  centrifugal  pump;  Unsteady  Reynolds  Averaged  Navier–Stokes  Equations  (URANS)  calculation Résumé : The flow in a double suction centrifugal pump is presented in this paper. The static performance of the machine has been obtained in a proper test rig, and the results have been compared with equivalent numerical results from an Unsteady Reynolds Averaged Navier–Stokes Equations (URANS) calculation. In a second step, the numerical results have been exploited to get detailed information about the flow inside the turbomachine. The main goal of the study is, on one hand, the validation of the numerical procedure proposed and, on the other hand, the detailed flow-field analysis for the machine, which points out the possibilities and drawbacks of the pump design. For a double suction machine, the inlet flow is characterized by the existence of a particular geometry that tries to force a uniform flow, at least for the nominal flow rate. On the contrary, at off-design conditions the lack of uniformity produces an unsteady incidence that gives rise to strong hydraulic loading variations. Instantaneous and average pressure fields have been analyzed in this paper to study the evolution of such inlet flow unsteadiness throughout the impeller and the volute. The analysis of both static and dynamic effects on the pump shaft has been carried out from the numerical calculation of the radial forces. The results have shown that the performance of the double suction centrifugal pump is suitable for typical design conditions. The best operation point or nominal flow rate is found to be at φ=0.274, which turns out to produce a specific speed ωS=1.25, well in the range for centrifugal impellers. This operating point is also found to be the one with better efficiency and with better flow characteristics, regarding the axisymmetry of the flow pattern and the fluid forces obtained. However, some particular features produce also interesting results for off-design operating points. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]