1.1 Intake Process:

In a screw compressor, the intake flow is regulated solely by the opening and closing of the intake throttle valve. When the space between the teeth of the male and female rotors rotates to the opening at the inlet end of the housing, the volume of this space is at its maximum. At this point, the space below the rotors communicates with the inlet port. Since all air in the tooth spaces is completely expelled during the discharge stroke, the tooth spaces are in a vacuum state when the discharge is complete. When the rotors rotate to the inlet port, outside air is drawn in and flows axially into the tooth spaces of the male and female rotors. When the space fills the entire tooth groove, the inlet end face of the rotors moves away from the housing’s inlet port, and the air within the tooth grooves is sealed off. This constitutes the “inlet process.”

1.2 Sealing and Delivery Process:

At the end of the intake stroke, the tooth crests of the male and female rotors seal against the housing, preventing the air in the tooth grooves from escaping; this is the “sealing process.” As the rotors continue to rotate, their tooth crests and grooves align at the intake end, and the contact surface gradually moves toward the exhaust end; this is the “delivery process.”
2.3 Compression and Oil Injection Process:
During the conveying process, the meshing surface gradually moves toward the discharge end, meaning the space between the meshing surface and the discharge port gradually decreases. The air within the tooth grooves is gradually compressed, and the pressure gradually increases; this is the “compression process.” Simultaneously with compression, lubricating oil is injected into the compression chamber due to the pressure difference and mixes with the air.
Oil injection primarily serves four functions:
A. Lubrication: The lubricating oil forms an oil film between the rotors, preventing direct contact and reducing friction;

B. Cooling: Since the lubricating oil absorbs a significant amount of compression heat, the compression process approaches isothermal compression, thereby reducing the compressor’s specific power;

C. Sealing: The oil film generated by the lubricating oil acts as a seal for the compressed air, improving the compressor’s volumetric efficiency;

D. Noise reduction: It reduces noise generated by high-frequency compression.

1.4 Exhaust Process:
When the exhaust end face of the rotors communicates with the housing (at which point the compressed gas pressure is at its highest), the compressed gas begins to be discharged until the meshing surfaces of the tooth crests and grooves move to the exhaust end face of the housing. At this point, the space between the meshing surfaces of the two rotors and the housing exhaust port is zero, thus completing the “exhaust process.” At the same time, the length of the tooth-to-tooth space between the meshing surfaces of the rotors and the housing’s inlet port reaches its maximum, thereby initiating a new compression cycle.