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Rotary positive displacement compressors

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Rotary compressors are positive displacement machines in which the compressing and displacement are affected by the positive action of rotating elements.

Types of rotary compressors

The two most common types of rotary positive displacement compressors are:

Vane compressors

The vane-type compressor consists of a cylindrical rotor with longitudinal slots in which radial sliding vanes are fitted. The rotor is positioned eccentrically within a cylindrical housing. The spaces between adjacent vanes form pockets of decreasing volume from a fixed inlet port to a fixed discharge port. Compressor inlet and discharge valves are not employed in the design. A vane compressor always compresses the gas to the design pressure defined by the manufacturer, regardless of the pressure in the system in which the compressor is discharging.

Screw compressors

The screw compressor, also known as a helical-lobe or spiral-lobe compressor, is a positive displacement rotary design that compresses gas between intermeshing helical lobes and chambers in the compressor housing. Screw compressors do not use valves. Their compression ratio is determined by the wrap angle of the lobes and the location of the opening edges of the discharge port. Of the various compressor types, screw compressors are best able to accommodate liquid carryover.


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See also



Reciprocating compressor

Centrifugal compressor