‌Rotary screw air compressor‌ is a gas compressor that uses a rotary positive displacement mechanism, usually consisting of helical gears (screws), to compress air by reducing the volume of the cavity. Its working principle is similar to other compressor types, such as reciprocating piston and centrifugal compressors, but provides a constant (non-pulsating) flow of compressed air and operates at 100% duty cycle‌.

how does a rotary screw air compressor work?

Air Intake:
Ambient air is drawn into the compressor through an intake valve.
The air enters the compression chamber, which is formed by the two rotating screws (the male and female rotors).
Trapping Air:
As the rotors rotate, the air is trapped in the cavities (or "pockets") between the rotors and the compressor housing.
The rotation of the screws reduces the volume of these cavities, compressing the air.
Compression:
As the rotors continue to turn, the trapped air is pushed along the length of the screws.
The volume of the air pockets gradually decreases, which increases the air pressure.
During this process, the temperature of the air rises due to compression.
Oil Injection (in oil-flooded compressors):
In oil-flooded rotary screw compressors, oil is injected into the compression chamber.
The oil serves three main purposes:
Cooling: It absorbs heat generated during compression.
Sealing: It helps seal the gaps between the rotors and the housing, improving efficiency.
Lubrication: It reduces friction between the moving parts.
Air-Oil Separation:
After compression, the air-oil mixture exits the compression chamber.
The mixture passes through a separator tank, where the oil is separated from the compressed air.
The oil is then filtered and recirculated back into the compression chamber.
Discharge:
The compressed air, now free of oil (in oil-flooded compressors), is discharged through the outlet valve.
The air may pass through an aftercooler to reduce its temperature before being used or stored.

Types and designs

Rotary screw air compressors can be divided into two types according to their design: single screw and twin screw. Single-screw compressors consist of a single main screw that meshes with two paired gate rotors. Twin-screw compressors contain two helical screws (one called "male" and the other called "female") that mesh with each other to compress air. Twin-screw compressors are more efficient in larger sizes, can handle higher pressure ratios, and operate at higher temperatures.

Application scenarios

Rotary screw air compressors are widely used in industrial applications that require large amounts of high-pressure air, such as large industrial applications or operating high-powered pneumatic tools, air cannons, etc. Because they provide a constant flow of compressed air, they are suitable for occasions that require a continuous and stable air supply.

In addition, rotary screw air compressors can operate around the clock without interruption, which is suitable for industrial environments that require long-term stable operation.