At this point also in centrifugal because of high rpm since it is directly coupled to engine the pump creates partial vacuum this means the liquid will flow through vacuum Centrifugal Vacuum Pump therefore the liquid will be recieved in the centrifugal pumps suction and because the impeller rotates the liquid will be displaced away forward with a specific energy.
A vacuum pump gets the inlet hooked up to 1 or both valve covers, sometimes the valley pan. It SUCKS the surroundings from the engine, hence reducing the air pressure build up created by blow because of combustion gases 
going at night piston rings in to the pan.