Generally, there are two types of screw air compressors: the single-screw type and the twin-screw (or double-screw) type. Here, we will make a comparison between these two types of air compressors.
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Structure of the air compressor
Single Screw A screw rotor and two symmetrically star wheels. As a result of the screw groove and the inner wall of the casing, a closed elementary volume is created. This way, the gas can reach its required pressure. Moreover, its structure is simple and the volume is small.
Twin Screw The twin-screw blower is a twofold shaft positive uprooting compressor. The primary (male) pair (female) two rotors coordinate to frame a meshing pair. The tooth profile of the main and auxiliary rotors shapes a closed elementary volume with the inner wall of the casing.
Working principle of the screw air compressor
Single Screw The motor transmits power to the screw shaft through coupling or a belt. The screw drives the star wheel to rotate. The gas enters the screw groove from the suction chamber. The exhaust port and the exhaust chamber compress the gas and it is discharged. The role of the star wheel is equivalent to the piston of a reciprocating piston compressor. When it moves relative to each other, the enclosed volume is gradually reduced. Then the gas is compressed.
Twin Screw The motor drives the main rotor through a coupling, speed-increasing gear or belt. The main rotor directly drives the auxiliary rotor to rotate together. Under the action of relative negative pressure, it sucks the air in. The gas is transported and compressed under the anastomosis of the tooth crest and tooth groove. When the rotor meshing surface turns to communicate with the exhaust port of the casing, they discharge the compressed gas.
Technical history of the screw air compressor
Single Screw The single screw type was invented more than ten years after the twin-screw type.
Twin Screw The twin-screw compressor had been invented way before the single screw.
Force Balance of the screw air compressor
Single Screw The screw's radial and axial forces are automatically adjusted. The planetary gear's gas force necessitates suitable strength and rigidity.
Twin Screw The screw rotor is subjected to significant radial and axial forces. It is necessary for the screw rotor to be strong and sturdy. Finally, the bearing must support a significant load.
Reliability of the screw air compressor
Single Screw The star wheel is a particularly vulnerable feature. It normally has a life expectancy of only a few thousand hours due to material issues. There will be no further dependability issues if it is managed as a consumable.
Twin Screw Due to the heavy bearing load, most screw compressors need to be maintained every 20,000 to 50,000 hours. The bearing needs to be replaced and it's worth a lot of money.
Noise and Vibration of the screw air compressor
Single Screw Good force balance, low noise and vibration
Twin Screw Poor force balance, high-frequency noise when the rotor meshes
Manufacturing cost of the screw air compressor
Single Screw For screw and star wheel bearings, ordinary bearings can be used. The cost of production is lower.
Twin Screw Due to the comparatively high load of two-screw rotors, better precision bearings are necessary. The cost of production is higher.
Maintenance and repairs of the screw air compressor
Single Screw Maintenance and repair are not difficult when it comes to single screws.
Twin Screw The twin-screw requires extremely little maintenance. Because of the widespread use of the twin-screw, there are an increasing number of professionals available to repair the main engine. There is no need to return to the factory or seek manufacturer assistance.
Scope of application of the screw air compressor
Single Screw It can function under extreme conditions and is ideal for situations involving high exhaust pressure. The star wheel and the single-screw rotor are in contact sealing. Oil-free is easier to achieve at low speeds.
Twin Screw It can only be used for power, refrigeration and gas transmission in medium and low-pressure applications. In most cases, it is less than 4.5 MPa. Because the rotors cannot mesh without oil lubrication, they must spin at a fast rate (usually above 10,000 rpm). The efficiency is insufficient.
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