Helical-Lobe Screw Rotary Compressors

The helical-lobe compressor is further divided into a dry and a flooded form. The dry fonn uses timing gears to hold a prescribed timing to tlie relative motion of the rotors the flooded form uses a liquid media to keep the rotors from touching. The helical-lobe compressor is the most sophisticated and versatile of the rotary compressor group and operates at the highest rotor tip Mach number of any of the compressors in the rotary family. This compressor is usually referred to as the screw compressor or the SRM compressor. ... 

Figure 8,7 Helical lobe, or screw, rotary air compressor...

The only major moving parts in screw compressors are two intermeshing helical rotors. The rotors consist of one male lobe, which functions as a rolling piston, and a female flute, which acts like a cylinder. The female rotor is composed of six flutes while the male rotor only has four lobes. Since rotary screw compression is a continuous positive-displacement process, no surges are created within the system. One cycle of compression is shown in Fig. 5.30. 

The spiral-lobe and helical-screw compressors are rotary positive-displacement machines and quite adaptable to a wide assortment of process and refrigeration gases. This class of equipment is usually built to comply with the American Petroleum Institute Standard 619. These units oper-... 

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