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International Journal of Rotating Machinery
Volume 7 (2001), Issue 3, Pages 173-181

Laser-Doppler Velocimetry Measurements Inside a Backward Curved Centrifugal Fan

1Professor, Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu, Taiwan
2Graduate Student, Department of Power Mechanical Engineering, National Tsing Hua University, Taiwan

Received 5 April 2000; Revised 27 May 2000

Copyright © 2001 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Laser-Doppler velocimetry (LDV) measurements are presented of relative mean velocity and turbulence intensity components inside the impeller passage of a centrifugal fan with twelve backward curved blades at design, under-design, and over-design flow rates. Additional LDV measurements were also performed at the volute outlet to examine the uniformity of the outlet flow for the three selected flow rates. Complementary flow visualization results in the tongue region are further presented. It is found that the number of characteristic flow regions and the average turbulence level increase with decreasing air flow rate. For the case of under-design flow rate, there are a through-flow region on the suction side, a reverse flow region on the pressure side, and a shear layer region in between. The corresponding average turbulence intensity is as high as 9.1% of blade tip velocity.