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Some aspects of centrifugal fan characteristics in blower windtunnels

Published online by Cambridge University Press:  04 July 2016

A. E. Johnson  and
P. E. Hancock
A. E. Johnson
Affiliation:
School of Mechanical and MaterialsEngineering, University of Surrey, UK
P. E. Hancock
Affiliation:
School of Mechanical and MaterialsEngineering, University of Surrey, UK
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Abstract

Measurements have been made in the exit flows of the fan, diffuser, settling chamber and contraction of a low speed blower windtunnel driven by a centrifugal fan. A velocity deficit and streamwise vortex were observed at the diffuser exit when the fan was operating at less than about 0·9 of maximum efficiency but not when operating above. Unacceptably large unsteadiness (-0·7% rms) occurred at low speeds when the fan speed was increased from rest, but not when the fan speed was decreased from full speed. This unsteadiness was at the rotor frequency, and appears to have been caused by laminar boundary layer separation on one or more adjacent aerofoil blades, coupled with slight asymmetry in the rotor. Unsteadiness at the rotor frequency and of comparable magnitude has also been seen in another, larger fan, but was not eliminated in the same way. Attaining high quality flow is likely to require careful attention to the characteristics of individual fans.

Type
Research Article
Information
The Aeronautical Journal , Volume 101 , Issue 1010 , December 1997 , pp. 481 - 485
Copyright
Copyright © Royal Aeronautical Society 1997 

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Footnotes

†

Now at BP Research and Engineering, Middlesex, UK.

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