How Rotary Screw Air Compressors Work
A rotary screw air-end or element has twin rotors, which include male and female parts rotating in opposite directions. Air fills the space between the rotors and, as they rotate, the volume between them and the surrounding housing decreases, squeezing or compressing the air into a smaller space. The length, pitch of the screw, and the form of the discharge port collectively determine the pressure ratio. Beyond that, there are no valves, or other mechanical forces that can cause unbalance, which allows a screw compressor to operate at high speeds while combining a large flow rate with small exterior dimensions – it packs a good punch for its size.
Original Source: https://www.atlascopco.com/en-us/compressors/faq-section/rotary-screw-air-compressors