Working principle of two-stage screw compressor

The working principle of a two-stage screw compressor is primarily based on its unique rotor structure and mode of operation. This compressor features a pair of intermeshing helical rotors with opposite rotational directions, commonly referred to as the male rotor and female rotor. Here is a detailed explanation of the working principle of a two-stage screw compressor in English:

Basic Structure and Composition

• Rotors: The male rotor has convex teeth, while the female rotor has concave teeth. These rotors intermesh and rotate in opposite directions at a specific gear ratio.
• Working Volume: The working volume, also known as the basic volume, is formed by a pair of tooth surfaces on the rotors, the inner wall of the compressor body, and the end covers.
• Ports: The compressor body is equipped with specially shaped ports at both ends: one for suction (inlet port) and the other for discharge (outlet port).

Working Principle

The working principle of a two-stage screw compressor involves three main processes that occur continuously during the rotation of the rotors: suction, compression, and discharge.

1. Suction Process
   • As the rotors rotate, one tooth of the male rotor continuously disengages from a tooth groove of the female rotor, resulting in a gradual expansion of the tooth space volume.
   • This expanding tooth space volume connects with the suction port, allowing external gas to enter the tooth space volume through the suction port.
   • When the tooth space volume reaches its maximum size, it disconnects from the suction port, and the suction process ends. At this point, the tooth space volume is sealed and ready for the compression process.
2. Compression Process
   • As the rotors continue to rotate, before the tooth spaces of the male and female rotors become interconnected, the gas in the tooth space volume of the male rotor is initially compressed by the intrusion of the female rotor tooth.
   • After a certain rotation angle, the tooth spaces of the male and female rotors become interconnected, forming a “V”-shaped tooth space pair (basic volume).
   • As the two rotor teeth move closer, the basic volume is gradually pushed and reduced, thus compressing the gas within.
   • This compression process continues until the basic volume connects with the discharge port, at which point the discharge process begins.
3. Discharge Process
   • As the basic volume continues to shrink due to the rotation of the rotors, the compressed gas is delivered to the discharge pipe.
   • This process continues until the volume reaches its minimum size, at which point the gas within the tooth space volume is completely discharged through the discharge port.

Working Characteristics

• Efficiency: The two-stage screw compressor exhibits forced air delivery, with a discharge volume that remains relatively unaffected by discharge pressure, ensuring high efficiency across a wide range of operating conditions.
• Stability: It operates smoothly with good dynamic balance, resulting in minimal vibration and allowing for a smaller foundation.
• Reliability: The compressor has a simple structure with few components and no wearing parts. Key friction components such as rotors and bearings are highly durable and well-lubricated, ensuring long operating cycles and reliability.
• Maintainability: It is easy to maintain and conducive to automation.

In summary, the two-stage screw compressor achieves continuous suction, compression, and discharge of gas through its unique rotor structure and mode of operation, offering high efficiency, stability, reliability, and ease of maintenance.

Air Compressor Startup: 6 Effective Measures to Prevent High Exhaust Temperature