Rotating instability waves as a noise source in a ducted axial fan

M. H. Krane, P. H. Bent, D. A. Quinlan

Research output: Contribution to conferencePaper

Abstract

Experimental evidence for efficient sound generation by a rotating instability in a small, low tip speed, ducted axial cooling fan is described. The radiated noise is spectrally decomposed to obtain the acoustic source spectra. A notable feature of the acoustic spectra is a broad peak that becomes dominant close to the best efficiency point of the fan. The existence of a rotating modal pattern in the fan flowfield is demonstrated using both hot-wire and blade-mounted hot-film sensor measurements. The autospectra of both velocity and hotfilm voltage show a broad hump composed of harmonically related narrow-band tones in the frequency range at which the large peaks appear in the acoustic source spectra. Correlation analysis of hot-film sensor signals demonstrates that this spectral pattern is highly coherent in the tip region of the blades and that it is rotating relative to the fan. Furthermore, the fluctuations on adjacent blades are shown to be in phase at the frequency of the acoustic spectral peaks, indicating that the acoustic peaks arise from constructive interference of pressure fluctuations on all blades.

Original languageEnglish (US)
Pages19-40
Number of pages22
StatePublished - Dec 1 1995
EventProceedings of the 1995 ASME International Mechanical Engineering Congress and Exposition - San Francisco, CA, USA
Duration: Nov 12 1995Nov 17 1995

Other

OtherProceedings of the 1995 ASME International Mechanical Engineering Congress and Exposition
CitySan Francisco, CA, USA
Period11/12/9511/17/95

Fingerprint

Acoustic signal processing
Correlation methods
fans
Spectrum analysis
Fans
spectrum analysis
Acoustics
Acoustic waves
blades
acoustics
tip speed
Sensors
Acoustic noise
sensors
low speed
narrowband
Wire
Cooling
frequency ranges
wire

All Science Journal Classification (ASJC) codes

  • Mechanical Engineering
  • Acoustics and Ultrasonics

Cite this

Krane, M. H., Bent, P. H., & Quinlan, D. A. (1995). Rotating instability waves as a noise source in a ducted axial fan. 19-40. Paper presented at Proceedings of the 1995 ASME International Mechanical Engineering Congress and Exposition, San Francisco, CA, USA, .
Krane, M. H. ; Bent, P. H. ; Quinlan, D. A. / Rotating instability waves as a noise source in a ducted axial fan. Paper presented at Proceedings of the 1995 ASME International Mechanical Engineering Congress and Exposition, San Francisco, CA, USA, .22 p.
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Krane, MH, Bent, PH & Quinlan, DA 1995, 'Rotating instability waves as a noise source in a ducted axial fan' Paper presented at Proceedings of the 1995 ASME International Mechanical Engineering Congress and Exposition, San Francisco, CA, USA, 11/12/95 - 11/17/95, pp. 19-40.

Rotating instability waves as a noise source in a ducted axial fan. / Krane, M. H.; Bent, P. H.; Quinlan, D. A.

1995. 19-40 Paper presented at Proceedings of the 1995 ASME International Mechanical Engineering Congress and Exposition, San Francisco, CA, USA, .

Research output: Contribution to conferencePaper

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AU - Bent, P. H.

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PY - 1995/12/1

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N2 - Experimental evidence for efficient sound generation by a rotating instability in a small, low tip speed, ducted axial cooling fan is described. The radiated noise is spectrally decomposed to obtain the acoustic source spectra. A notable feature of the acoustic spectra is a broad peak that becomes dominant close to the best efficiency point of the fan. The existence of a rotating modal pattern in the fan flowfield is demonstrated using both hot-wire and blade-mounted hot-film sensor measurements. The autospectra of both velocity and hotfilm voltage show a broad hump composed of harmonically related narrow-band tones in the frequency range at which the large peaks appear in the acoustic source spectra. Correlation analysis of hot-film sensor signals demonstrates that this spectral pattern is highly coherent in the tip region of the blades and that it is rotating relative to the fan. Furthermore, the fluctuations on adjacent blades are shown to be in phase at the frequency of the acoustic spectral peaks, indicating that the acoustic peaks arise from constructive interference of pressure fluctuations on all blades.

AB - Experimental evidence for efficient sound generation by a rotating instability in a small, low tip speed, ducted axial cooling fan is described. The radiated noise is spectrally decomposed to obtain the acoustic source spectra. A notable feature of the acoustic spectra is a broad peak that becomes dominant close to the best efficiency point of the fan. The existence of a rotating modal pattern in the fan flowfield is demonstrated using both hot-wire and blade-mounted hot-film sensor measurements. The autospectra of both velocity and hotfilm voltage show a broad hump composed of harmonically related narrow-band tones in the frequency range at which the large peaks appear in the acoustic source spectra. Correlation analysis of hot-film sensor signals demonstrates that this spectral pattern is highly coherent in the tip region of the blades and that it is rotating relative to the fan. Furthermore, the fluctuations on adjacent blades are shown to be in phase at the frequency of the acoustic spectral peaks, indicating that the acoustic peaks arise from constructive interference of pressure fluctuations on all blades.

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Krane MH, Bent PH, Quinlan DA. Rotating instability waves as a noise source in a ducted axial fan. 1995. Paper presented at Proceedings of the 1995 ASME International Mechanical Engineering Congress and Exposition, San Francisco, CA, USA, .