- Conveying to discharge side
- Pressure equalisation
As the rotors turn, air in the inlet is trapped between the rotor lobes and the casing. When the advancing lobe reaches the lip of an eccentric bore hole in the casing, this "pre-inlet channel" allows gradual equalisation of pressure between the trapped inlet air and the air drawn in from the discharge side. Pressure equalisation in two-lobe blocks occurs abruptly as the advancing lobe crosses the lip of the discharge port. This is the main reason why three-lobe blocks generate significantly less pulsation than two-lobe blocks. The air is then finally pushed out against the pressure in the pipe work.