Daily Question 201803023: Screw Refrigeration Compressors – Basic Structure and Characteristics (Extra Question)
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This post was last edited by YORK Industrial Refrigeration on 2018-3-27 at 09:11. This year’s 【Daily Question】is divided into three categories: screw refrigeration compressors, refrigeration systems, and oil circuits, aiming to provide a comprehensive understanding of refrigeration technology. (If you encounter something you don’t know or can’t answer, please actively look up information; as you do so, your skills will improve!) ) All participants in the comments on this post will receive 10 wealth points; those who give complete answers will receive 20 points, with the validity period being two days. ============================== Basic structure and characteristics of screw refrigeration compressors (additional question): What are the differences between screw air compressors and screw refrigeration compressors? (Answer from the perspectives of structure and principle.) Structure: Generally, refrigeration compressors have more balance pistons than air compressors ； In terms of energy regulation, the refrigeration compressor uses an energy regulation device with slide valves and sliders, while the air compressor is controlled by a minimum opening valve. Principle: Different compression media; other similarities ============================== High-quality promotions: Mechanical equipment——Videos on the repair and adjustment of York compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1806833 Mechanical equipment——Maintenance procedures for York screw compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=1806833 Mechanical equipment——Upgrading of York Quinton control centers https://bbs.hcbbs.com/thread-1804837-1-1.html Mechanical equipment——Major repairs of GEA Grasox screw compressors https://bbs.hcbbs.com/thread-1800467-1-1.html Mechanical equipment——Disassembly and maintenance of British HOWDEN screw compressors https://bbs.hcbbs.com/thread-1832529-1-1.html Mechanical equipment——Disassembly and maintenance of Japanese Maekawa MYCOM screw compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=
In principle, the medium transported by a refrigeration unit is primarily a refrigerant, whereas the medium transported by an air compressor is air. Structurally, screw refrigerators often use slide valves or sliders to regulate the cooling capacity. Air compressors, on the other hand, do not require a slide valve mechanism.
The basic structure of a screw-type refrigeration compressor consists mainly of a rotor, a casing (including the cylinder block in the middle and the suction and discharge end caps at both ends), bearings, shaft seals, a balance piston, and an energy regulation device. The operation of a screw compressor relies on the meshing motion of an male rotor and a female rotor, and it takes place within the space enclosed by the inner wall of the casing surrounding this pair of rotors. As the rotor rotates continuously, the processes of suction, compression, and exhaust cycle repeatedly, with each elementary volume taking turns to operate, thus forming the working cycle of a screw refrigeration compressor. The working principle of a screw air compressor involves four processes: suction, sealing and delivery, compression, and exhaust. As the screw rotates within the housing, it engages with the toothed grooves of the housing. Air is drawn in through the intake port, along with engine oil. As the toothed grooves rotate, they seal the inhaled air and oil mixture and transport it toward the exhaust port. During this transportation process, the gap between the toothed grooves gradually decreases, causing the air and oil mixture to be compressed. When the toothed grooves rotate to the exhaust port of the housing, the high-pressure air and oil mixture is expelled from the device.
A screw-type refrigeration compressor is mainly composed of a rotor, a casing (including the cylinder block in the middle and the suction and discharge end caps at both ends), bearings, shaft seals, a balance piston, and an energy regulation device. The operation of a screw compressor relies on the meshing motion of an male rotor and a female rotor, and it takes place within the space enclosed by the inner wall of the casing surrounding this pair of rotors. As the rotor rotates continuously, the processes of suction, compression, and exhaust cycle repeatedly, with each elementary volume taking turns to operate, thus forming the working cycle of a screw refrigeration compressor. The working principle of a screw air compressor involves four processes: suction, sealing and delivery, compression, and exhaust. As the screw rotates within the housing, it engages with the toothed grooves of the housing. Air is drawn in through the intake port, along with engine oil. As the toothed grooves rotate, they seal the inhaled air and oil mixture and transport it toward the exhaust port. During this transportation process, the gap between the toothed grooves gradually decreases, compressing the air and oil mixture. When the toothed grooves rotate to the exhaust port of the housing, the high-pressure air-oil mixture is discharged from the unit
Inside the compressor housing, a pair of intermeshing spiral rotors are arranged parallel to each other; the rotor with protruding teeth on its pitch circle (as viewed in cross-section) is usually referred to as the male rotor or male screw； A rotor with recessed teeth inside the pitch circle (as viewed in cross-section) is called a female rotor or female screw. Generally, the male rotor serves as the driving rotor, and it is the male rotor that causes the female rotor to rotate. The ball bearings on the rotor enable axial positioning of the rotor and bear the axial forces in the compressor. The tapered roller thrust bearings at both ends of the rotor enable radial positioning of the rotor, and they bear the radial and axial forces in the compressor. Holes of certain shapes and sizes are provided at both ends of the compressor unit; one of them, used for intake, is called the suction port ； The other one for exhaust and intake is called an exhaust port.
The working cycle of a screw compressor can be divided into the suction process (including suction and sealing processes), the compression process, and the discharge process. As the rotor rotates, each pair of intermeshing teeth sequentially completes the same working cycle; for simplicity, we will consider only one such pair of teeth.
Inside the compressor housing, a pair of intermeshing spiral rotors are arranged parallel to each other; the rotor with protruding teeth on its pitch circle (as viewed in cross-section) is usually referred to as the male rotor or male screw； A rotor with recessed teeth inside the pitch circle (as viewed in cross-section) is called a female rotor or female screw. Generally, the male rotor serves as the driving rotor, and it is the male rotor that causes the female rotor to rotate. The ball bearings on the rotor enable axial positioning of the rotor and bear the axial forces in the compressor. The tapered roller thrust bearings at both ends of the rotor enable radial positioning of the rotor, and they bear the radial and axial forces in the compressor. Holes of certain shapes and sizes are provided at both ends of the compressor unit; one of them, used for intake, is called the suction port ； The other one for exhaust and intake is called an exhaust port.
In terms of structure and principle: 1. A screw-type refrigeration compressor is mainly composed of a rotor, a casing (including the cylinder block in the middle and the suction and discharge end caps at both ends), bearings, shaft seals, a balance piston, and an energy regulation device. The operation of a screw compressor relies on the meshing motion of an male rotor and a female rotor, and it takes place within the space enclosed by the inner wall of the casing surrounding this pair of rotors. As the rotor rotates continuously, the processes of suction, compression, and exhaust cycle repeatedly, with each elementary volume taking turns to operate, thus forming the working cycle of a screw refrigeration compressor. 2. The working principle of a screw air compressor is based on four processes: suction, sealing and delivery, compression, and exhaust. As the screw rotates within the housing, it engages with the toothed grooves of the housing. Air is drawn in through the intake port, along with engine oil. As the toothed grooves rotate, they seal the inhaled air and oil mixture and transport it toward the exhaust port. During this transportation process, the gap between the toothed grooves gradually decreases, causing the air and oil mixture to be compressed. When the toothed grooves rotate to the exhaust port of the housing, the high-pressure air and oil mixture is expelled from the device. From the perspective of the compressed medium: Refrigeration units use refrigerants, while air compressors compress air
According to the diagram you provided, the air compressor is an oil-free screw compressor with synchronous gears. The chiller is an oil-injected screw compressor. Of course, there are also air compressors with oil injection. Air compressors use valves with the minimum opening, while chillers use slide valves.