The most comprehensive analysis of the advantages and disadvantages of these five compressors is worth a look

The most comprehensive analysis of the advantages and disadvantages of these five compressors is worth a look There are five main types of compressors, piston compressors, rolling rotor compressors, turbo compressors, screw compressors, and centrifugal compressors. This article briefly introduces the advantages and disadvantages of various compressors. 1. Piston compressor (1) Working principle: 　　When the crankshaft of the piston compressor rotates, the piston will reciprocate through the transmission of the connecting rod, and the working volume composed of the inner wall of the cylinder, the cylinder head and the top surface of the piston will periodically change. When the piston of the piston compressor starts to move from the cylinder head, the working volume in the cylinder gradually increases. At this time, the gas moves along the intake pipe and pushes the intake valve into the cylinder until the working volume reaches the maximum. The intake valve is closed; when the piston of the piston compressor moves in the reverse direction, the working volume in the cylinder shrinks and the gas pressure increases. When the pressure in the cylinder reaches and is slightly higher than the exhaust pressure, the exhaust valve opens and the gas exits the cylinder. The exhaust valve closes until the piston moves to the limit position. When the piston of the piston compressor moves again in the reverse direction, the above process repeats itself. 　　 In short, the crankshaft of the piston compressor rotates once, the piston reciprocates once, and the process of intake, compression, and exhaust in the cylinder is completed, that is, a working cycle is completed. (2) Advantages: 　　 1. Regardless of the flow rate, you can get the required pressure, the exhaust pressure range is wide, the highest pressure can reach 320MPa (industrial application), or even 700 MPa (in the laboratory); 　　 2. The stand-alone capacity is any flow rate below 500 m3/min; 　　 3. Within the general pressure range, the requirements for materials are low, and most common steel materials are used, which is easier to process and cheaper to manufacture; 　　 4. The thermal efficiency is high, and the thermal insulation efficiency of general large and medium-sized units can reach about 0.7 to 0.85; 　　 5. When the air volume is adjusted, the adaptability is strong, that is, the exhaust range is wide, and it is not affected by the pressure level, and it can adapt to a wider pressure range and cooling capacity requirements; 　　 6. The gravity and characteristics of the gas have little effect on the working performance of the compressor. The same compressor can be used for different gases; 　　 7. The driving machine is relatively simple, most of them use electric motors, generally do not adjust the speed, and have strong maintainability; 　　 8. Piston compressor is relatively mature in technology, and has accumulated rich experience in production and use; (3) Disadvantages: 　　 1. The structure is complicated and bulky, there are many wearing parts, the area is large, the investment is high, the maintenance workload is large, and the service period is short, but after hard work, it can reach more than 8,000 hours; 　　 2. The rotation speed is not high, the machine is large and heavy, and the single machine exhaust is generally less than 500 m3/min; 　　 3. Vibration during machine operation; 　　 4. The exhaust is discontinuous, and the airflow has pulsation, which is easy to cause pipeline vibration. In severe cases, the pipeline network or machine parts are often damaged due to pulsation and resonance of the airflow; 　　 5. Flow adjustment adopts auxiliary volume or bypass valve, although simple, convenient and reliable, but the power loss is large, and the efficiency is reduced during partial load operation; 　　 6. For oil-lubricated compressors, the oil in the gas needs to be removed; 　　 7. When a large factory uses multiple compressor units, there are many operators or work intensity. 2. Rolling rotor compressor (1) Working principle: 　　 Rolling rotor compressor is a volume type rotary compressor. The change of the working volume of the cylinder is realized by the rolling of the cylindrical rotor of an eccentric device in the cylinder. 　　 1. The rotor makes one revolution, which will complete the compression and exhaust process of the previous working cycle and the suction process of the next working cycle; 　　 2. Since there is no steam inlet valve, the timing of the start of suction has a strict correspondence with the position of the suction port on the cylinder, and does not change with the change of working conditions; 　　 3. Due to the installation of the exhaust valve, the timing of the end of compression will vary with the pressure change in the exhaust pipe. (2) Advantages: 　　Compressors of this type are also commonly used in household refrigerators and air conditioners. Its advantages are: 　　 1. The structure is simple, the volume is small, and the weight is light. Compared with the piston compressor, the volume can be reduced by 40% to 50%, and the weight can also be reduced by 40% to 50%; 　　 2. Fewer parts, especially less wearing parts, and less friction loss between relative moving parts, so the reliability is higher; 　　 3. Only the slider has a small reciprocating inertial force, the rotating inertial force can be completely balanced, the rotation speed can be higher, and the vibration is small, and the operation is stable; 　　 4. No suction valve, long suction time, small clearance volume, and direct suction, reducing harmful overheating of the suction, so its high efficiency. However, its processing and assembly accuracy requirements are high. Because there is no gas valve, it can be used to transport dirty and process gas with droplets and dust. (3) Disadvantages: 　　The main disadvantage of rotary compressors is the large leakage, friction and wear between the sliding plate and the cylinder wall surface, which limits its working life and efficiency improvement; and this compressor requires higher processing accuracy. If a double-layer slide is used, the ends of the two slides keep in contact with the inner wall of the cylinder to form two seal lines, and an oil seal is formed between the two seal lines, which greatly reduces the leakage loss at the end of the slide. Reduce friction and friction loss, so that the working life and efficiency of the machine are improved. Once the compressor wears on its bearings, main shaft, rollers or sliding plates, and the gap increases, it will immediately have a significant adverse effect on its performance. Therefore, it is usually used in the refrigerators and air conditioners assembled in the factory. In the device, a high degree of cleanliness is also required in the system. 3. Scroll compressor (1) Working principle: The main components of the scroll compressor are two involute scroll disks with the same shape but with angular phase positions that are 180° relative to each other. One is a fixed scroll disk, and the other is driven by an eccentric shaft whose axis is around A fixed orbiting scroll axis orbiting scroll. 　　 In the work, the two scroll disks are tangent to form a seal line at many places, plus the appropriate seals at the end surfaces of the two scroll disks, thereby forming a tooth-shaped air cavity for several months. The seal line at the common tangent point between the two scrolls continuously shifts along the vortex curve with the orbit of the orbiting scroll, causing the shape and size of these crescent-shaped air chambers to change all the time. The suction port of the compressor is opened in the upper part of the fixed scroll casing. 　　When the eccentric shaft rotates clockwise, the gas enters the suction chamber from the suction port, and is successively taken into the peripheral crescent-shaped air chamber communicating with the suction chamber. As these peripheral crescent-shaped air chambers are closed and no longer communicate with the suction chamber, their enclosed volume is gradually transferred to the center of the fixed scroll and shrinks continuously, the gas is continuously compressed and the pressure increases. (2) Advantages: 　　In terms of specific structure, the scroll compressor has no suction and discharge valves, which greatly improves the reliability of high-speed operation. Taken together, scroll compressors have the following main features: 1. Belongs to the third-generation compressor, multiple compression chambers work at the same time, the gas pressure difference between adjacent compression chambers is small, the gas leakage is small, the volumetric efficiency is high, up to 98%, which is more compressed than the rotor of the second-generation compressor The machine efficiency is about 5% higher; 　　 2. The eccentric shaft driving the movable scroll can rotate at high speed, therefore, the scroll compressor is small in size and light in weight; 　　3. The change of force on moving parts such as movable scroll and main shaft is small, and the vibration of the whole machine is small; 　　 4. Without suction and exhaust valves, the scroll compressor operates reliably, and is particularly suitable for variable speed movement and frequency conversion speed regulation technology; 5. The compression chamber of the scroll compressor is composed of scroll profiles. It is a multi-chamber compression mechanism. When the center of the movable scroll makes a circular motion around the center of the static scroll, the volume of each compression chamber changes with the rotation angle of the main shaft. Correspondingly reduce or expand, so as to achieve the gas suction, compression and exhaust process, because the intake and exhaust process is almost continuous, the whole machine noise is very low; 6. The axial and radial flexible structure improves the production efficiency of the scroll compressor, and ensures that the sealing effect of the axial gap and the radial gap is not reduced due to friction and wear, that is, the scroll compressor has reliable and effective Tightness, so its cooling coefficient does not decrease with the increase of operating time, but slightly improves; 7. The scroll compressor has good working characteristics, and its performance is mainly affected by its own compression ratio and suction pressure. The exhaust pressure range is wide. It is suitable for various indoor and outdoor environments to ensure that the compressor has been running at a high energy efficiency ratio. So as to ensure the energy efficiency ratio of the air conditioning unit. In the heat pump type air conditioning system, it is particularly manifested in high heating performance, good stability and high safety; 8. The scroll compressor has no clearance volume and belongs to multi-compartment compression in structure. The pressure difference between adjacent chambers is not very large (approximately continuous change). At the same time, the sealing strip at the contact surface of the dynamic and static scroll end faces the shaft The back pressure is compressed to make the dynamic and static scrolls closely contact, and achieve a good sealing effect with the help of freezing oil, so that the internal leakage is almost non-existent; when the end surface of the sealing strip is worn, it can be along the axial direction The direction is automatically compensated to ensure that the end surface of the movable scroll and the bottom surface of the fixed scroll are always tight, and the longer the compressor works, the better the cooperation of these tight relative moving surfaces and the better the sealing effect. These advantages make the scroll The compressor does not have the problem of secondary compression of refrigerant gas, which is one of the important guarantee factors for maintaining high volumetric efficiency operation; 　　 9. The torque change is small, the balance is high, the vibration is small, the operation is stable, so the operation is simple and easy to realize automation; 　　10. Because of its few moving parts and no reciprocating mechanism, it has a simple structure, small size, light weight, few parts (especially few wearing parts), high reliability, and a life span of more than 20 years. (3) Disadvantages: 　　 1. The surfaces of moving parts are mostly curved surfaces. The processing and inspection of these curved surfaces are complicated. The manufacturing requires high-precision processing equipment and precise self-aligning assembly technology, so the manufacturing cost is high; 2. Between moving parts or between moving parts and fixed parts, a certain movement gap is often used to achieve the seal, and the gas will inevitably cause leakage through the gap, which limits the difficulty of the rotary compressor to achieve greater compression. Than, therefore, most rotary compressors are more used in air conditioning conditions. 4. Screw compressor (1) Working principle: The screw compressor is formed by the meshing of a male rotor composed of five convex teeth (hereinafter referred to as M rotor) and a female rotor composed of six concave teeth (hereinafter referred to as F rotor) to form a tooth-shaped space. The tooth space compresses the refrigerant to a predetermined pressure. The working process of screw compressor is as follows: 　　 1. Inhalation stroke: 　　 The refrigerant is sucked from the suction port that opens in the axial direction to the radial direction. With the rotation of the rotor, on the lower side of the rotor, the engagement is separated, the length of the tooth groove is increased, and the refrigerant is drawn into the tooth space; 　　 2. Compression stroke: 　　 Starting from the suction side of the tooth groove, the tooth shape meshes, the seal line gradually moves toward the discharge side, the tooth space decreases, and compression is performed; 　　Lubricant sucked together with the refrigerant forms an oil film seal in the rotor gap and lubricates the rotor. The male rotor and female rotor gradually approach the discharge port for compression, and the pressure increases; 　　 3. Discharge stroke: 　　 The toothed space is connected to the discharge port to start the discharge stroke. This stroke continues until the discharge end until the refrigerant in the tooth space is completely sent out. (2) Advantages: 　　 1. Fewer parts, less wearing parts and high reliability; 　　 2. Convenient operation and maintenance; 　　 3. No unbalanced inertial force, stable and safe operation, low vibration; 　　 4. With the characteristics of forced gas transmission, the exhaust volume is almost not affected by the exhaust pressure, and the adaptability of the working conditions is strong; 　　 5. The rotor tooth surface of the screw compressor actually has a gap, so it is not sensitive to wet stroke and can withstand liquid shock; 　　 6. The exhaust temperature is low, and it can be operated under a higher pressure ratio; 　　 7. Stepless adjustment of cooling condition can be realized. A slide valve mechanism is adopted to make stepless adjustment of the cooling capacity from 15% to 100%, saving operating costs; 　　 8. Easy to realize automation and remote communication. (3) Disadvantages: 　　 1. The rotor tooth surface is a space curved surface, which needs special tools to be processed on expensive equipment. The machining accuracy of body parts also has high requirements, and high-precision equipment must be used; 　　 2. Because the interdental volume periodically communicates with the suction and exhaust ports, the compressor noise is high; 　　 3. Due to the limitations of rotor stiffness and bearing life, the compressor can only rely on the gap seal, so the screw compressor can only be used in the medium and low pressure range, not in high pressure occasions; 　　 4. Due to the large amount of fuel injection and the complicated oil treatment system, there are many auxiliary equipment of the unit; 　　 5. The screw compressor relies on the gap to seal the gas and does not have superior performance in a small volume range. 5. Centrifugal compressor (1) Working principle: 　　The structure and working principle of centrifugal refrigeration compressor are very similar to centrifugal blower. However, its working principle is fundamentally different from that of a piston compressor. It does not use the cylinder volume reduction method to increase the gas pressure, but depends on the change of kinetic energy to increase the gas pressure. 　　 Centrifugal compressors have a working wheel with blades. When the working wheel rotates, the blades drive the gas movement or make the gas get kinetic energy, and then convert part of the kinetic energy into pressure energy to increase the pressure of the gas. This type of compressor is called centrifugal compressor because it continuously sucks refrigerant vapor and continuously throws it out in the radial direction while it is working. (2) Advantages: 　　 1. The centrifugal compressor has large air volume, simple and compact structure, light weight, small unit size and small footprint. Compared with the piston compressor, when the cooling capacity is the same, the weight is five to eight times lighter than the piston type; 　　 2. Because it has no wearing parts such as steam valve piston ring, and no crank connecting rod mechanism, it has balanced operation, reliable operation, high operation rate, and few friction parts. Therefore, it requires less spare parts, less maintenance costs and fewer personnel; 　　 3. There is no friction between the working wheel and the casing, and no lubrication is needed. In the chemical process, the centrifugal compressor can achieve an absolutely oil-free compression process for the chemical medium; 　　 4. Centrifugal compressor is a rotary motion machine, which is suitable for direct drag of industrial steam turbine or gas turbine. For general large chemical plants, by-product steam is often used to drive industrial steam turbines as power, which provides the possibility of comprehensive utilization of thermal energy. (3) Disadvantages: 1. Centrifugal compressors are currently not suitable for applications where the air volume is too small and the pressure ratio is too high, and because it is suitable to use a refrigerant with a relatively large molecular weight, it is only suitable for large refrigeration capacity, generally 25 to 300,000 kcal / Hour or more; 　　 2. The stable working area of the centrifugal compressor is narrow. Although its air volume adjustment is more convenient, it is less economical; 　　 3. At present, the efficiency of centrifugal compressors is generally lower than that of piston compressors; 　　 4. Generally, a speed-increasing gear is used for transmission, which has a relatively high speed and high requirements on the sealing of the shaft end. These all increase the manufacturing difficulties and the structural complexity.

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