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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 [...]