At this point also in centrifugal because of high rpm as it is directly coupled to motor the pump creates partial Centrifugal Vacuum Pump vacuum this means the liquid will flow through vacuum therefore the liquid will become recieved at the centrifugal pumps suction and as the 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 surroundings from the engine, thus reducing the surroundings pressure build up created by blow because of combustion gases going past the piston rings in to the pan.