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International Journal of Rotating Machinery
Volume 3, Issue 4, Pages 259-268

Measurements of the Flow in Backshroud/Casing Clearance of Precessing Centrifugal Impeller

1Engineering Science, Osaka University, Machikaneyama 1-3, Toyonaka, Osaka 560, Japan
2Mechanical Engineering, Kogakuin University, Nishishinjuku 1-24-2, Shinjuku, Tokyo 163-91, Japan

Received 6 March 1997; Revised 24 March 1997

Copyright © 1997 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.


Detailed flow measurements have been made to clarify the unsteady flow in the backshroud/ casing clearance of a precessing centrifugal impeller. The unsteady pressure was integrated to obtain the fluid force moment on the precessing impeller shroud for various precessing frequencies. It was shown that the fluid force moment can become rotordynamically destabilizing for small forward precessing motion as originally found by Ohashi et al. The effects of leakage flow in the backshroud/casing clearance and a gap between impeller side plate and casing at the impeller outlet are clearly shown, and the discussions are also made based on the unsteady velocity and pressure measurements.