is the mechanism through which force is applied to a gas. There are three basic types of compressors: dynamic, reciprocating, and rotary. A dynamic compressor (also called kinetic) may be either centrifugal or axial flow. A centrifugal compressor uses the rotation of an impeller and a shaft to push the gas outward. An axial flow-type uses the rotation of a propeller-type blade to move the gas in the axial direction of the shaft. A reciprocating compressor employs a piston and cylinder to compress the gas. A rotary compressor uses a rotating vane or screw. Both reciprocating and rotary-type compressors are also known as positive displacement compressors. To reduce temperature rise and minimize oil oxidation and deposit buildup, some compressors are multi-stage, raising the air to the desired pressure in several steps through a sequence of chambers and cooling the air between steps. Because gas compression generates heat, a compressor lubricant should have high oxidation stability, as well as good demulsibility, rust and corrosion inhibition and anti-foam properties.

Also see anti-foam agent, corrosion inhibitor, intercooling, rust inhibitor.