Now also in centrifugal due to high rpm as it is directly coupled to electric motor the pump creates partial vacuum which means the Centrifugal Vacuum Pump liquid can flow through vacuum hence the liquid will end up being recieved at the centrifugal pumps suction and since the impeller rotates the fluid will be displaced aside forward with a particular energy.

A vacuum pump gets the inlet hooked up to one or both valve covers, sometimes the valley pan. It SUCKS the air from the engine, thus reducing the air flow pressure build up created by blow because of combustion gases going at night piston rings into the pan.