(2) Intermeshing
An electric motor, drives the main rotor through the coupling, or belts. As the two
rotors are intermeshed with each other, the main rotor directly drives the sub rotor
to rotate together. The cooling lubrication oil is directly injected into the intermeshing
part via a nozzle, from the lower part of the casing of the compressor. Oil is mixed
with the air, takes along the heat generated by compression and reaches the cooling
effect. Meanwhile, the cooling lubrication oil forms the oil film, which prevents the
direct metal contact between the rotors and prevents the clearance between the
sealing rotors and between the rotors and the casing. The injected lubrication oil can
also reduce the noise generated by the compression in high speed. Because of the
difference of the air exhaust pressure, all the weight of the injected oil is 5-10 times
larger than that of the air.
3. The compression principles of the screw type compressor
(1) The course of absorbing the air.
An air suction port on the air suction side of the screw type compressor is designed
as the compression chamber can fully absorb the air. However, the screw type
compressor has a suction valve and an internal check valve to prevent air back flow.
The intake valve is regulated from a solenoid valve which opens and closes the
suction valve. When the rotors are rotated, the space of the tooth grooves of the
main rotor and sub rotor is maximized as the rotors are rotated into an open intake
end wall. At that time, the space of the tooth grooves on the rotors is produced
with the free air in the air inlet. Therefore, the air in the tooth groove is totally
taken out when the air is exhausted. After the air is completely exhausted, the
tooth grooves are still under a vacuum state. When the rotors are rotated into the
air inlet, the outside air is absorbed and flows into the tooth grooves of the main
rotor and the sub rotor. When the air is full in the tooth grooves, the air intake side
end surfaces of the rotors are rotated away from the air inlet of the casing, and the
air between the tooth grooves is sealed. The above course is called as the ‘the
course of absorbing the air’.
(2) The course of sealing and conveyance.
When the main rotor and the sub rotor complete air suction, the tooth peaks of the
main rotor and sub rotor and the casing will be sealed together. At that time, the
air is sealed in the tooth groove and eliminates back flow. This course is called ‘the
sealing course’. The two rotors are continuously rotated. The tooth peaks and the
tooth grooves are inosculated with each other at the air suction end. The
inosculating surface is gradually moved toward the air exhaust end. This course is
called as ‘the conveyance course’
(3) The course of compression and injecting oil
