At this point also in centrifugal because of high rpm as it is directly coupled to engine the pump creates partial vacuum this means the liquid will certainly flow through vacuum therefore the liquid will become recieved in the centrifugal pumps suction and as the Centrifugal Vacuum Pump impeller rotates the fluid will be displaced away forward with a particular energy.
A vacuum pump has the 
inlet hooked up to one or both valve covers, sometimes the valley pan. It SUCKS the air flow from the engine, hence reducing the air flow pressure build-up created by blow because of combustion gases going at night piston rings in to the pan.