Editing Mixing (process engineering) (section)

===Turbines===
A selection of turbine geometries and power numbers are shown below.
{| class="sortable wikitable" style="float:right; margin: 0 0 0.5em 1em"
|+ Selected Turbine Geometries and Power Numbers <br />
!Name
!Power number
!Flow direction
!Blade angle (degrees)
!Number of blades
!Blade geometry
|-
| [[Rushton turbine]] || 4.6 || Radial || 0 || 6 || Flat
|-
| Pitched blade turbine || 1.3 || Axial || 45–60 || 3–6 || Flat
|-
| Hydrofoil || 0.3 || Axial || 45–60 || 3–6 || Curved
|-
| Marine Propeller || 0.2 || Axial || N/A || 3 || Curved
|- style="background:#ccc;"
|colspan=6 |
|}

[[File:Mixing - flusso assiale e radiale.jpg|thumb|200px|Axial flow impeller (left) and radial flow impeller (right).]]

Different types of impellers are used for different tasks; for instance, [[Rushton turbine]]s are useful for dispersing gases into liquids, but are not very helpful for dispersing settled solids into liquid. Newer turbines have largely supplanted the Rushton turbine for gas–liquid mixing, such as the Smith turbine and Bakker turbine.<ref>{{cite web |url=http://www.bakker.org/cfm/bt6.htm |title=Asymmetric Blade Impeller |publisher=Bakker.org |date=1998-12-16 |access-date=2017-06-23 |url-status=live |archive-url=https://web.archive.org/web/20170814175906/http://www.bakker.org/cfm/bt6.htm |archive-date=14 August 2017 |df=dmy-all }}</ref> 
The power number is an empirical measure of the amount of torque needed to drive different impellers in the same fluid at constant power per unit volume; impellers with higher power numbers require more torque but operate at lower speed than impellers with lower power numbers, which operate at lower torque but higher speeds.{{Cn|date=March 2025}}