The Effect of Impeller and Tank Geometry on Power Number for a Pitched Blade Turbine

Previous studies of the Rushton turbine have shown that the power number is sensitive to the details of impeller geometry, and in particular to the blade thickness, but is independent of the impeller diameter to tank diameter ratio. In this paper, a similar study is reported for the pitched blade impeller. The results show that the power number is independent of blade thickness, but dependent on the impeller to tank diameter ratio. This is exactly the opposite result to that observed for the Rushton turbine. Physical explanations are given for the differences in behaviour between the two impellers. For the Rushton turbine, power consumption is dominated by form drag, so details of the blade geometry and flow separation have a significant impact (30%) on the power number. For the pitched blade impeller, form drag is not as important, but the flow at the impeller interacts strongly with the proximity of the tank walls, so changes in the position of the impeller in the tank can have a significant impact on the power number.

[1]  J. H. Rushton,et al.  Power Characteristics of Mixing Impellers part 1 , 1950 .

[2]  S. Nagata,et al.  Power Characteristics of Mixing Impellers , 1956 .

[3]  R. Bates,et al.  Examination of Some Geometric Parameters of Impeller Power , 1963 .

[4]  F. A. Holland,et al.  Liquid Mixing and Processing in Stirred Tanks , 1966 .

[5]  A. Nienow,et al.  A dynamometer for the accurate measurement of mixing torque , 1969 .

[6]  A. W. Nienow,et al.  Impeller Power Numbers in Closed Vessels , 1971 .

[7]  S. Nagata.  Mixing: Principles and Applications , 1975 .

[8]  Stanley M. Barnett,et al.  Mixing of single and two phase systems: Power consumption of impellers , 1982 .

[9]  Alvin W. Nienow,et al.  A MULTIPURPOSE STIRRED TANK FACILITY FOR FLOW VISUALISATION AND DUAL IMPELLER POWER MEASUREMENT , 1983 .

[10]  Vincent W. Uhl,et al.  Mixing: Theory and Practice , 1986 .

[11]  Jyeshtharaj B. Joshi,et al.  Improvements in gas inducing impeller design , 1987 .

[12]  Alvin W. Nienow,et al.  The dependency on scale of power numbers of Rushton disc turbines , 1987 .

[13]  G. B. Tatterson,et al.  Power consumption in a mixer , 1988 .

[14]  Gary B. Tatterson,et al.  Fluid mixing and gas dispersion in agitated tanks , 1991 .

[15]  Suzanne M. Kresta,et al.  The mean flow field produced by a 45° pitched blade turbine: Changes in the circulation pattern due to off bottom clearance , 1993 .

[16]  A. Nienow,et al.  Power curves and flow patterns for a range of impellers in newtonian fluids: 40 , 1995 .

[17]  Jamshid M. Nouri,et al.  The application of a strain gauge technique to the measurement of the power characteristics of five impellers , 1995 .

[18]  G. Zhou,et al.  Distribution of Energy Between Convective and Turbulent-Flow for 3 Frequently Used Impellers , 1996 .

[19]  Michael Yianneskis,et al.  The Influence of Rushton Impeller Blade and Disk Thickness on the Mixing Characteristics of Stirred Vessels , 1996 .

[20]  Barbara Mazzarotta,et al.  Power Consumption in Stirred Tanks Provided with Multiple Pitched-Blade Turbines , 1999 .

[21]  Jie Wu,et al.  Performance analysis of axial‐flow mixing impellers , 2000 .