Axial thrust in a vessel with unsteady rotating axial impeller

Unsteady motion of the impeller is one of many methods to improve mixing in an unbaffled vessel. It is very important in pharmaceutical industry, crystallization processes or some chemical reactions with catalyst where baffles are not recommended. The literature data shows that unsteady mixing causes generation of axial flow for radial impellers (Rushton turbine). The purpose of this study was to investigate axial force for axial impellers like A315, HE-3 and SC-3. Moreover, the momentum number, flow number and pumping efficiency were analysed. Results show that axial force for unsteady mixing was higher in comparison to steady-state mixing. Also, the comparison of axial force between impellers shows that blades influence momentum number and flow number. Impellers with larger blade surface generate stronger axial force. The obtained results reveal that unsteady mixing with axial impellers could be applied for solid-liquid mixing as a suitable alternative to steady-state mixing.