positive displacement pump
A positive displacement pump makes a fluid move by trapping a fixed amount and forcing (displacing) that trapped volume into the discharge pipe. ... Liquid flows into the pumpas the cavity on the suction side expands and the liquid flows out of the discharge as the cavity decreases.
The most common type among centrifugal pump is the radial flow pump. ... The main difference between these types of pumps and centrifugal is that positive displacement pumps will move fluid at the same speed regardless of the pressure on the inlet end and centrifugal pumps will not