2 - Compressor types and applications

Abstract

This chapter presents an overview of compressor types and their applications. The two basic classifications of compressors are—positive displacement and dynamic compressors. Positive displacement compressors are constant volume, variable energy machines that are not affected by gas characteristics. The type of compressor that will be used for a specific application therefore depends on the flow rate and pressure required and the characteristic of the gas to be compressed. Rotary lobe compressors are usually supplied with noise enclosures or silencers to reduce their characteristic high noise level. The single-stage design consists of a pair of rotors that mesh in a one-piece, dual-bore cylinder. The male rotor usually consists of four helical threads that are spaced 90° apart. Liquid ring rotary compressors consist of a round, multiblade rotor that revolves in an elliptical casing. The elliptical casing is partially filled with a liquid, which is usually water. The compression cycle of a reciprocating compressor consists of two strokes of the piston which include the suction stroke and the compression stroke. A diffuser surrounds the impeller and it serves to gradually reduce the velocity of the gas as the gas leaves the impeller. The centrifugal multistage integral gear is also elaborated.