3.2.7. Screw compressor


Fig. 3.14: Symbol of screw compressor

The screw compressor is a rotary displacement compressor.

Two parallel rotors with differing profiles work in opposite directions inside a housing.

The intake air is compressed in chambers, which continuously decrease in size due to the rotation of the rotors until the final pressure is reached, and is then forced out of the discharge outlet. The chambers are formed by the casing walls and the meshing helical gears of the rotors.

Fig. 3.15: Op. diagram of screw compressor
Oil-free screw compressors

On screw compressors that seal without oil, and with which the air in the compression chamber does not come into contact with oil, the two rotors are connected by a synchronised transmission so that the surface profiles do not touch.

Screw compressors with oil-injection cooling

On screw compressors with oil-injection cooling only the main rotor is under power. The secondary rotor turns without contact. <BR><BR>

Fig. 3.16: Section through screw compressor stage
    • Small size.
    • Continuous air production.
    • Low final compression temperature.
      (with oil-injection cooling)