TYPES OF SCREW COMPRESSORS
Two main categories of twin screw compressors screw and one screw. Twin-screw compressor is widely used and has many years of operating experience. He occupies the position of the piston and centrifugal type as standard range of refrigeration compressors. The single-screw type, described in Section 5.22, is becoming a well-established thanks to the efforts of several manufacturers. Twin - screw will simply be referred to in this Chapter as and screw compressors.
The invention and development of screw compressor bears a heavy Swedish imprint through a number of companies on the beginning of the turn of the century with the company Ljungstrom brothersname, which later became associated with Ljungstrom air heater for power plants. In 1913 brothers organized a subsidiary Svenska Turbinfabriks Aktiebolaget Ljungstrom, also known by the acronym " STEEL". After some successes and failures, Ljungstrom brothers resigned from the company in the 1920s and a new chief engineer, Alf Lysholm, was appointed, which gave the firm a few inventions, including screw compressors.
The first 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 LjungstrГ¶ms Angturbin was changed to Svenska Rotor Maskiner AB (SRM). Up until this time, screw compressors were equipped synchronization gear and operated dry, but in the 1950s the practice of injecting oil and started this development has provided a screw compressor a new impetus. Is mainly used for air compressors, initially, development work on the use of screw compressors and refrigerants began in the 1950s. Improvement of the rotor profiles provide ease of production and effective operation has been a constant focus in screw compressor development. Now about a million air compressors and almost 100 000 screw refrigerant compressors of production.
In conclusion of this conversation was that in recent decades the screw compressor has accumulated large compressor market in industrial refrigeration, especially in large-capacity units. Cooling capacity each year screw compressor offers more power than piston-type, so the principles, applications, and procedures described in this Chapter are especially important. Screw compressors are supplied in the amount of capacity ranges from 0.05 to 1.5 m3/s (100 to 3300 cfm), driven by engines range in output from 25 up to 1250 kW, working at normal speed 3550 rpm (2950 rpm, 50 Hz power).
This Chapter describes the screw compressor and explains how it works. Performance of the main compressor is first explored, in particular, when it detects temperature change of evaporation and condensation. Capacity control of the screw compressor is typically achieved through the use of special valve, which ensures continuous modulation of power in a wide range. Screw compressors are basically constant volume ratio of the machines, the consequences of which will be explored. Oil injected into the screw compressors to seal the space between the blades, and this oil must then be separated and cool. End users of refrigeration units, as a rule, buy screw compressors are included in the packages, which contain the necessary auxiliary equipment, which will be described. The Chapter concludes with an explanation of the single-rotor compressor...