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Noise prediction of a centrifugal fan / Rafael Ballesteros-Tajadura in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 9 (Septembre 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 12 p. Titre : Noise prediction of a centrifugal fan : numerical results and experimental validation Type de document : texte imprimé Auteurs : Rafael Ballesteros-Tajadura, Auteur ; Sandra Velarde-Suárez, Auteur ; Juan Pablo Hurtado-Cruz, Auteur Année de publication : 2009 Article en page(s) : 12 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Centrifugal  fan;  noise  prediction Résumé : Centrifugal fans are widely used in several applications, and in some cases, the noise generated by these machines has become a serious problem. The centrifugal fan noise is frequently dominated by tones at the blade passing frequency as a consequence of the strong interaction between the flow discharged from the impeller and the volute tongue. In this study, a previously published aeroacoustic prediction methodology (Cho, Y., and Moon, Y.J., 2003, “Discrete Noise Prediction of Variable Pitch Cross-Flow Fans by Unsteady Navier-Stokes Computations ,” ASME J. Fluids Eng., 125, pp. 543–550) has been extended to three-dimensional turbulent flow in order to predict the noise generated by a centrifugal fan. A three-dimensional numerical simulation of the complete unsteady flow on the whole impeller-volute configuration has been carried out using the computational fluid dynamics code FLUENT ® . The unsteady forces applied by the fan blades to the fluid are obtained from the data provided by the simulation. The Ffowcs Williams and Hawkings model extension of Lighthill’s analogy has been used to predict the aerodynamic noise generated by the centrifugal fan from these unsteady forces. Also, the noise generated by the fan has been measured experimentally, and the experimental results have been compared to the numerical results in order to validate the aerodynamic noise prediction methodology. Reasonable agreement has been found between the numerical and the experimental results. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...] [article] Noise prediction of a centrifugal fan : numerical results and experimental validation [texte imprimé] / Rafael Ballesteros-Tajadura, Auteur ; Sandra Velarde-Suárez, Auteur ; Juan Pablo Hurtado-Cruz, Auteur . - 2009 . - 12 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 9 (Septembre 2008) . - 12 p. Mots-clés : Centrifugal  fan;  noise  prediction Résumé : Centrifugal fans are widely used in several applications, and in some cases, the noise generated by these machines has become a serious problem. The centrifugal fan noise is frequently dominated by tones at the blade passing frequency as a consequence of the strong interaction between the flow discharged from the impeller and the volute tongue. In this study, a previously published aeroacoustic prediction methodology (Cho, Y., and Moon, Y.J., 2003, “Discrete Noise Prediction of Variable Pitch Cross-Flow Fans by Unsteady Navier-Stokes Computations ,” ASME J. Fluids Eng., 125, pp. 543–550) has been extended to three-dimensional turbulent flow in order to predict the noise generated by a centrifugal fan. A three-dimensional numerical simulation of the complete unsteady flow on the whole impeller-volute configuration has been carried out using the computational fluid dynamics code FLUENT ® . The unsteady forces applied by the fan blades to the fluid are obtained from the data provided by the simulation. The Ffowcs Williams and Hawkings model extension of Lighthill’s analogy has been used to predict the aerodynamic noise generated by the centrifugal fan from these unsteady forces. Also, the noise generated by the fan has been measured experimentally, and the experimental results have been compared to the numerical results in order to validate the aerodynamic noise prediction methodology. Reasonable agreement has been found between the numerical and the experimental results. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/Issue.aspx?issueID=27337 [...]

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 [...]