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Research Papers: Flows in Complex Systems

Noise Prediction of a Centrifugal Fan: Numerical Results and Experimental Validation

[+] Author and Article Information
Rafael Ballesteros-Tajadura

Área de Mecánica de Fluidos, Universidad de Oviedo, Campus de Gijón, 33271 Gijón, Spainrballest@uniovi.es

Sandra Velarde-Suárez

Área de Mecánica de Fluidos, Universidad de Oviedo, Campus de Gijón, 33271 Gijón, Spainsandrav@uniovi.es

Juan Pablo Hurtado-Cruz

Área de Mecánica de Fluidos, Universidad de Oviedo, Campus de Gijón, 33271 Gijón, Spainjhurtado@usach.cl

J. Fluids Eng 130(9), 091102 (Aug 12, 2008) (12 pages) doi:10.1115/1.2953229 History: Received March 23, 2007; Revised April 17, 2008; Published August 12, 2008

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.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 14

Power spectra of volute pressure fluctuations in pascals (experimental, upper side; 3D-numerical simulation, bottom side) at the measurement Point P06 (at 60deg from the tongue, z∕B=0.15 and z∕B=0.40), with the fan operating at the BEP

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Figure 15

Power spectra of volute pressure fluctuations in pascals (experimental, upper side; 3D-numerical simulation, bottom side) at the measurement Point P10 (at 180deg from the tongue, z∕B=0.15 and z∕B=0.40), with the fan operating at the BEP

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Figure 16

Amplitude (pascals) of volute pressure fluctuation at the blade passing frequency, 3D-numerical (white squares) and experimental (dotted line), with the fan operating at the BEP

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Figure 17

Geometric parameters used in the Ffowcs Williams–Hawkings equation

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Figure 19

Predicted SPL (decibels) around the fan: (a) plane (x,0,z), (b) plane (x,y,0), and (c) plane (0,y,z); flow rate: BEP

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Figure 20

SPL (decibels) at the blade passing frequency around the fan; plane (x,0,z); flow rate: 1.70×BEP: (a) predicted and (b) measured

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Figure 21

Measured SPL (decibels) at the blade passing frequency around the fan; plane (x,0,z); flow rate: Qmax

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Figure 22

Predicted (full line) and measured (dotted line) SPLs (decibels) along a line on the plane (x,0,z): (a) x=0.5m and (b) x=1.5m; flow rate: 1.70×BEP

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Figure 7

Fan performance dimensionless curves: experimental (black squares) and numerical (black triangles), with the operating points selected in this study (white squares)

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Figure 6

Mesh details around the radial gap between the impeller front shroud and the casing

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Figure 5

General view of the geometry of the fan

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Figure 4

Sketch of the fan unstructured mesh

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Figure 3

Influence of mesh size on the fan total pressure coefficient

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Figure 2

Sketch of the test installation

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Figure 1

Tested fan with the location of some measurement points

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Figure 8

Contours of the relative tangential component of velocity at the impeller outlet (negative values are clockwise)

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Figure 9

Contours of the radial component of velocity at the impeller outlet

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Figure 10

Sketch of the fan with the measurement points

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Figure 11

Evolution of volute pressure fluctuations with time at Point P02 (at the tongue, z∕B=0.30)

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Figure 12

Evolution of volute pressure fluctuations with time at Point P10 (180deg from the tongue, z∕B=0.30)

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Figure 13

Power spectra of volute pressure fluctuations in pascals (experimental, upper side; 3D-numerical simulation, bottom side) at the measurement Point P02 (at 2deg from the tongue, z∕B=0.15 and z∕B=0.40), with the fan operating at the BEP

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Figure 18

Picture of the fan during the acoustic measurements

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