Rotary lobe air compressors are positive displacement, non-contact or clearance type compressors. Two intermeshing rotors have lobe profiles that intermesh during rotation. Air flows into the compression chamber from the two inlet ports while the discharge ports are sealed by the rotor lobes. Rotation continues until the two discharge ports are exposed to the compression chamber, when the air is discharged. The dual inlet/outlet ports eliminate any axial thrust loads.
Lubrication
With no mechanical contact within the compression chamber of a rotary lobe compressor, lubrication within this chamber is eliminated. Lubrication of bearings, timing gears and speed increasing gears is all external to the compression chamber, and shaft seals prevent any migration of oil to the compression chamber. This ensures oil-free compression and air delivery.
Cooling
As for most industrial air compressors operating in the 80 - 125 psig range, two stages of compression are required to handle the heat of compression in oil-less rotary lobe compressors. Air leaving the first stage is passed through an air intercooler, where its temperature is reduced as close as possible to atmospheric temperature and resulting condensate drained off, before it enters the second stage compression chamber where it is compressed to the desired system pressure. A typical air end consists of a cast iron stator housing that may have passage for air or water cooling.
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