The cylinder of screw compressor is equipped with a pair of Intermeshing Helical male-female rotors. Both rotors have concave teeth. They rotate opposite to each other. The main rotor (also known as the female rotor or the convex rotor) is driven by an engine or an electric motor (mostly driven by an electric motor).
The other rotor (also known as the male rotor or concave rotor) is driven by the oil film formed by the main rotor through injection, or by synchronous gears at the main rotor end and concave rotor end. So there is no metal contact in the drive (theoretically). The length and diameter of the rotor determine the exhaust volume (flow rate) and pressure of the compressor. The longer the rotor is, the higher the pressure is. The larger the diameter of the rotor is, the larger the flow rate is.
The spiral rotor groove is filled with gas as it passes through the suction port. When the rotor rotates, the groove of the rotor is closed by the shell wall to form a compression chamber. When the groove of the rotor is closed, the lubricant is injected into the compression chamber to seal, cool and lubricate. When the rotor rotates to compress the lubricant and gas, the volume of the compression chamber decreases and the mixture of oil and gas is compressed to the exhaust port. When the compression chamber passes through the exhaust port, the mixture of oil and gas is discharged from the compressor to complete a suction - compression - exhaust process.