Althoughtheprinciplesofoperationofhelicalscrewmachines, ascompressors or
expanders, have been well known for more than 100 years, it is only
during the past 30 years that these machines have become widely used.
The main reasons for the long period before they were adopted were their
relatively poor e?ciency and the high cost of manufacturing their
rotors. Two main developments led to a solution to these di?culties. The
?rst of these was the introduction of the asymmetric rotor pro?le in
1973. This reduced the bl- hole area, which was the main source of
internal leakage by approximately 90%, and thereby raised the
thermodynamic e?ciency of these machines, to roughly the same level as
that of traditional reciprocating compressors. The second was the
introduction of precise thread milling machine tools at - proximately
the same time. This made it possible to manufacture items of complex
shape, such as the rotors, both accurately and cheaply. From then on, as
a result of their ever improving e?ciencies, high rel- bility and
compact form, screw compressors have taken an increasing share of the
compressor market, especially in the ?elds of compressed air production,
and refrigeration and air conditioning, and today, a substantial
proportion of compressors manufactured for industry are of this type.
Despite, the now wide usage of screw compressors and the publication of
many scienti?c papers on their development, only a handful of textbooks
have been published to date, which give a rigorous exposition of the
principles of their operation and none of these are in English
