Editing Impeller (section)

== In pumps ==
[[File:Pump Impellers-1.jpg|thumb|right|Several different types of pump impellers]]
[[File:Impellerrad.jpg|thumb|right|[[Flexible impeller]] of cooling system pump of an [[outboard engine]] ([[1 euro cent coin]] for comparison, diameter 16.25 mm)]]
An impeller is a rotating component of a [[centrifugal pump]] that accelerates fluid outward from the center of rotation, thus transferring [[energy]] from the [[Engine|motor]] that drives the pump to the [[fluid]] being pumped.<ref>{{Cite book
|last=Gülich
|first=Johann Friedrich
|title=Centrifugal Pumps
|edition=2nd
|isbn=978-3-642-12823-3
|year=2010
|publisher=Springer
}}</ref><ref>{{cite book|last1=Manuals|first1=Seloc Marine|title=Volvo Penta Stern Drives 2003-2012: Gasoline Engines & Drive Systems (Seloc Marine Manuals|year=2008|publisher=Seloc Publishing|isbn=978-0893300746}}</ref> The acceleration generates output pressure when the outward movement of the fluid is confined by the pump casing. An impeller is usually a short cylinder with an open inlet (called an eye) to accept incoming fluid, vanes to push the [[fluid]] radially, and a [[spline (mechanical)|splined]], [[Key (engineering)|keyed]], or threaded bore to accept a drive shaft.

It can be cheaper to [[casting|cast]] an impeller and its spindle as one piece, rather than separately. This combination is sometimes referred to simply as the "rotor."