Effect of Eccentricity on the Pumping Capacity in an Unbaffled Vessel

The aim of this study was to investigate the effect of the shaft eccentricity on the pumping capacity in stirred vessels estimated with the aid of the particle image velocimetry technique with impellers in centred and off-centred positions. For the off-centred case, 19 different planes in the azimuthal direction were taken to obtain a reliable average velocity into the whole tank. The velocity and vorticity fields were evaluated for all positions. A Rushton turbine and a pitched blade turbine (PBT) were operated in laminar and turbulent regimes. The pumping number increased considerably with eccentricity for the Rushton turbine (radial flow), whereas the effect for the PBT turbine (axial flow) was almost negligible.

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