TABLE OF CONTENTS The two major categories of screw compressors are twin screw and single screw. The twin-screw compressor is widely used and has many years of operating experience. It occupies a position alongside reciprocating and centrifugal types as a standard choice of refrigeration compressors. The single-screw type, described in Section 5.22, is becoming well established because of the efforts of several manufacturers. The twin- screw will simply be referred to in this chapter as the screw compressor.
The invention and evolution of the screw compressor bears a heavy Swedish imprint through a succession of firms beginning about the turn of the century with the company of the Ljungstrom brothers a name that became associated later with the Ljungstrom air preheater for power plants. In 1913 the brothers organized a subsidiary, Svenska Turbinfabriks Aktiebolaget Ljungstrom, also known by the acronym STAL. Following some successes and reverses, the Ljungstrom brothers resigned from the company in the 1920s and a new chief engineer, Alf Lysholm, was appointed, who provided the firm with several inventions, including that of the screw compressor.
The early screw compressors were fraught with many deficiencies in design and operation which had to be solved one by one. In 1951 the name of AB Ljungstroms Angturbin was changed to Svenska Rotor Maskiner AB (SRM). Up until this time screw compressors were equipped with synchronizing gears and operated dry, but during the 1950s the practice of injecting oil began and this development gave the screw compressor...
