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The mean flow field produced by a 45° pitched blade turbine: Changes in the circulation pattern due to off bottom clearance
Author(s) -
Kresta Suzanne M.,
Wood Philip E.
Publication year - 1993
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.5450710107
Subject(s) - impeller , circulation (fluid dynamics) , flow (mathematics) , flow visualization , mechanics , turbine , blade (archaeology) , leading edge , materials science , geology , mechanical engineering , engineering , physics
The impeller discharge stream and bulk circulation flow produced by a pitched blade turbine (PBT) in a fully baffled stirred tank have been defined, using a combination of flow visualization and laser Doppler anemometry measurement techniques. Two distinct bulk circulation patterns have been identified, one for higher off bottom clearances, and one for lower clearances. The circulation patterns are shown to have a substantial impact on the discharge stream, even very close to the edge of the impeller blades. These findings indicate that the action of the impeller is not independent of the tank geometry, but contains a substantial feedback component from the bulk flow. This conclusion has substantial implications for the modelling and prediction of stirred tank flow fields.