Segment V12.3: Windshield Washer Pump

(Related to Textbook Section 12.4 - The Centrifugal Pump)

For each revolution or cycle of a positive displacement pump, a given amount of fluid is pumped. Except for leakage, the volume flowrate is independent of the operating pressure differential.

Although the impeller for a windshield washer pump looks like that for a centrifugal pump (a turbomachine), it is a positive displacement pump. The shaft of the flexibleblade impeller is off-set from the center of the chamber in which it is housed. As the impeller rotates, each blade deforms, causing the fluid to alternately enter or leave the variable-volume cavity between successive impeller blades, thereby causing a pumping action.