Learning guide: Focus on understanding the structure, principles, functions, and materials of the components, and pay attention to understanding the energy regulation system and lubrication system of the compressor, as well as the principle of the economizer.

At present, most of the oil injected screw compressors used in refrigeration systems adopt a single-stage open structure. Some small Freon screw compressors adopt semi enclosed or fully enclosed structures.
The structure of the screw compressor is shown in the animation above. Its main components are rotor, body, bearings, shaft seal, balance piston, and energy regulating device.














Single screw compressor (as shown in the picture) Double screw compressor (as shown in the picture)
(1) Shell


Due to the internal fuel injection of the body, the temperature inside the cylinder can be directly reduced, so there is no need for a cooling water jacket. Instead, ribs are added outside the casing to enhance its strength and provide heat dissipation. The casing is commonly cast with gray cast iron such as HT200.






(2) Rotor


It is the main component for implementing variable capacity compression, consisting of female and male rotors 3 and 7, commonly made of ductile iron such as QT600-3.






(3) Bearing
(4) Balance piston
(5) Shaft seal
(6) Energy regulation mechanism
(7) Silencer

2、 Gas transmission regulation device
Screw refrigeration compressors commonly use slide valves to adjust energy, which means installing an axially movable slide valve on the high-pressure side of both rotors to regulate energy and unload start-up. The principle of adjusting energy with a slide valve is to use the slide valve to move in the axial direction of the screw to change the effective axial working length of the screw, so that the energy can be continuously and infinitely adjusted between 100% and 10%.