The screw air compressor is a core equipment for industrial air supply, and its working principle is based on the volumetric compression of a pair of intermeshing screw rotors. It converts the mechanical energy of the motor into the pressure energy of compressed air through continuous "sucking, compressing, and exhausting" cycles. Below is a detailed breakdown of its working principle, key components, and operational cycle.
Before understanding the working principle, it is necessary to clarify the core components that drive the compression process. The most critical part is the compression chamber composed of two rotors and a casing:
The compression process relies on the relative rotation of the male and female rotors—as the rotors mesh, the volume of the "cavity" formed between the rotor teeth and the casing continuously changes, thereby completing three key stages: suction, compression, and exhaust.
- When the motor drives the male rotor to rotate, the female rotor follows the meshing teeth to rotate in the opposite direction.
- As the rotors rotate, the grooves on the rotor ends (near the suction port) gradually "open"—the volume of the cavity formed between the rotor teeth and the casing increases, and the internal pressure decreases (lower than atmospheric pressure).
- Under the action of pressure difference, atmospheric air (or air from the air filter) is sucked into the cavity through the suction port until the rotor teeth rotate to the end of the suction port (the cavity is fully filled with air).
- After the suction is completed, the rotors continue to rotate, and the "air-filled cavity" is gradually pushed toward the exhaust port (high-pressure side) by the subsequent meshing teeth.
- During this process, the volume of the cavity is continuously compressed and reduced (because the rotor teeth gradually mesh and the cavity space shrinks). According to Boyle’s Law (constant temperature, pressure is inversely proportional to volume), the air pressure in the cavity increases sharply.
- For oil-injected screw compressors, cooling oil is injected into the compression chamber at this stage: it absorbs the heat generated by compression (preventing overheating), enhances the sealing of the cavity (reducing air leakage), and lubricates the rotating rotors.
- When the compressed air in the cavity reaches the design pressure (consistent with the system pressure demand), the cavity is just connected to the exhaust port on the casing.
- With the continuous rotation of the rotors, the high-pressure air (mixed with oil mist for oil-injected models) is completely "squeezed out" of the cavity and discharged through the exhaust port.
- After exhaust, the rotors return to the initial position, and the next suction-compression-exhaust cycle starts immediately. The entire process is continuous and non-pulsating, so the output air pressure is stable.
The working principle of the two types is similar (both rely on rotor meshing compression), but the core difference lies in whether oil is involved in the compression process—this determines their application scenarios:
The working principle of screw compressors gives them unique advantages over other types (e.g., piston compressors):
- Stable Output: Continuous cyclic operation, no pulsation in air pressure, and low noise.
- High Efficiency: Large compression cavity volume, fast rotation speed, and high air displacement per unit time.
- Simple Maintenance: Fewer moving parts (only two rotors rotate, no reciprocating parts like pistons), low wear, and long service life.
- Wide Adaptability: Can adjust the exhaust pressure and displacement by matching frequency converters (frequency conversion screw compressors), adapting to variable load demands.
In summary, the screw air compressor realizes efficient and stable compression of air through the "volume change caused by rotor meshing". Its design (oil-injected or oil-free) is tailored to different industrial needs, making it the mainstream choice for modern industrial air supply systems.
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