I. Basic structure of screw compressor: In the body of the compressor, a pair of intermeshing helical rotors are arranged in parallel. A rotor having a convex tooth outside the pitch circle is generally referred to as a male rotor or a male screw. A rotor having a concave tooth in a pitch circle is called a female rotor or a female rotor. Generally, the male rotor is connected with the prime mover, and the male rotor drives the female rotor to rotate. The last pair of bearings on the rotor are axially positioned and withstand the axial forces in the compressor. Cylindrical roller bearings at both ends of the rotor position the rotor radially and withstand the radial forces in the compressor. At both ends of the compressor body, openings of a certain shape and size are respectively opened. One for inhalation, called the intake port; the other for exhaust, called the exhaust port. Working principle: The working cycle of the screw compressor can be divided into three processes of intake, compression and exhaust. As the rotor rotates, each pair of intermeshing teeth successively complete the same duty cycle.
1. Intake process: When the rotor rotates, the space of the groove of the male and female rotor is the largest when it is turned to the opening of the inlet end wall. At this time, the space of the rotor groove is connected with the inlet, due to the gas in the groove during exhaust. It is completely discharged. When the exhaust is completed, the groove is in a vacuum state. When it is turned to the intake port, the outside air is sucked and enters the groove of the male and female rotor in the axial direction. When the gas fills the entire groove, the end face of the rotor is turned away from the inlet of the casing, and the gas in the groove is closed. 2. Compression process: At the end of the inhalation of the male and female rotors, the tip of the male and female rotors will be closed with the casing, and the gas will no longer flow out in the grooves. The mating surface gradually moves toward the exhaust end. The space between the meshing surface and the exhaust port is gradually smaller, and the gas in the groove is increased by the compression pressure. 3. Exhaust process: When the meshing end face of the rotor is turned into communication with the exhaust port of the casing, the compressed gas begins to be discharged until the meshing surface of the tooth tip and the groove moves to the exhaust end face, and the meshing surface of the male and female rotor is The gullet space of the casing exhaust port is 0, that is, the exhaust process is completed, and at the same time, the length of the groove between the meshing surface of the rotor and the air inlet of the casing is the longest, and the air intake process is performed again. It can be seen from the above working principle that the screw compressor is a volumetric gas compression machine with a working volume for rotary motion. The compression of the gas is achieved by a change in volume, which is achieved by the rotary motion of a pair of rotors of the compressor in the casing. Second, the characteristics of the screw air compressor: In terms of the principle of gas pressure increase, the screw air compressor is the same as the piston compressor, and is a positive displacement compressor. In terms of the form of motion of the main components, it is similar to a centrifugal compressor. Therefore, the screw compressor has the characteristics of the above two types of compressors. Advantages of screw air compressor: 1. High reliability: the screw compressor has few parts and no wearing parts, so it runs reliably and has a long service life. The interval between overhauls can reach 40,000 to 80,000 hours. 2. Convenient operation and maintenance: operators do not have to undergo professional training to achieve unattended operation. 3. Good dynamic balance: the screw compressor has no unbalanced inertia force, and the machine can work smoothly at high speed, which can achieve no basic operation. 4. Adaptability: The screw compressor has the characteristics of forced air transmission, and the displacement is almost independent of the exhaust pressure, which ensures high efficiency in a wide range. 5. Multi-phase mixing: Screw compressor The rotor tooth surface actually has a gap, so it can withstand liquid impact, and can be used to pump liquid-containing gas, dust-containing gas, and easily polymerized gas.
Shortcomings of screw air compressor: 1. High cost: The rotor tooth surface of the screw compressor is a space curved surface, which needs to be processed on expensive special equipment by using special tools. In addition, there is a high requirement for the machining accuracy of the screw compressor cylinder. 2. Not suitable for high pressure applications: Due to the limitations of rotor stiffness and bearing life, screw air compressors can only be used in medium and low pressure ranges, and the exhaust pressure should not exceed 3.0Mpa.
3. Can not be made into a miniature: screw air compressor relies on the gap sealing gas, currently only the volume flow is more than 0.2m3 / min, screw air compressor has superior performance.
This article is edited by China DSNEAIR Compressor Manufactory (https://air-compressor.net). Please indicate