Refrigeration compressors are divided into several categories according to the working principle
①Displacement compressor. Its working principle is to use a mechanical method to reduce the volume of the closed container, so that the gas is compressed to increase its pressure. The P-volume compressor can be divided into reciprocating piston type and rotary piston type; rotary piston type can be divided into screw type and sliding plate Type, scraper type. Piston compressors are the most commonly used positive displacement compressors, but rotary compressors have developed rapidly in recent years, especially in terms of high efficiency, miniaturization, and light weight. Rolling piston type (rolling rotor type) and scroll type And screw type have great advantages. Reciprocating piston compressors are divided into connecting rod type and sliding tube type. There are crankshaft type and crank type in connecting rod type. The bottom of the crankshaft compressor casing is connected with the base of the refrigerator. The whole movement is supported on the inner wall of the casing by the spring. The stator of the compressor motor is fixed on the machine body, and the rotor of the motor drives the crankshaft to rotate. The upper and lower bearings of the main shaft are fixed on the machine body. The crankshaft between the two bearings is connected to the connecting rod in a dynamic fit, and the other end of the connecting rod is connected to the piston. When the motor rotates the spear to drive the main shaft, due to the joint action of the crankshaft and the connecting rod, the piston reciprocates in the cylinder, and the high-pressure valve plate and the low-pressure valve plate on the cylinder head are alternately opened and closed to complete the suction and discharge of gas . The lower end of the main shaft is immersed in the freezing oil, and the cooling oil is brought to the upper part by the oil hole on the shaft to lubricate the various parts to change the crankshaft into a crank structure, which is called a crank piston compressor.
In some medical and household refrigerators, in order to further simplify the structure of the compressor, a sliding tube slider type mechanism is used instead of the connecting rod assembly. The hollow cylindrical piston and the sliding tube are welded into a straight T-shaped overall g slider is a cylinder, which can slide in the sliding tube b has a round hole in the center of its waist, and the crank pin on the crankshaft passes through the sliding The tube wall is inserted vertically into this round hole to form a secondary shaft. When the crankshaft rotates, the slider rotates around the center of the crankshaft and slides back and forth in the slide tube, driving the entire slide tube piston to reciprocate in the cylinder to achieve compression The role of gas. The other structure is similar to the general piston structure.
②Speed type compressor. Its working principle is to use mechanical methods to make the flowing gas obtain a high flow rate, and then reduce the gas flow rate in the expanding channel to convert the kinetic energy of the gas into pressure energy, thereby increasing the pressure of the gas. Speed compressors are centrifugal and axial. Mechanical principles of refrigeration compressors Refrigerating compressor In the vapor compression refrigeration system, the refrigerant is raised from low pressure to high pressure, and the refrigerant is continuously circulated, so that the system continuously discharges the internal heat to the environment above the system temperature. The refrigeration compressor is the heart of the refrigeration system. The refrigeration system inputs electrical energy through the compressor, thereby discharging heat from a low-temperature environment to a high-temperature environment. The energy efficiency ratio of the refrigeration compressor determines the energy efficiency ratio of the entire refrigeration system. Since the ambient temperature changes frequently, the compressor is under partial load most of the time, so the compressor must have energy regulation.
The screw compressor does not have the cylinder, piston, piston ring, cylinder liner and other vulnerable parts required by the piston compressor. The machine has a compact structure, small volume, light weight, no clearance volume, and no liquid impact when a small amount of liquid enters the machine Danger. The valve can be used for 10% to 100% stepless energy adjustment. It has a wide range of application, stable and reliable operation, long maintenance cycle, and trouble-free operation time of (2 to 5) × 104h. Due to the use of lubricating oil, the cooling and sealing performance of the machine is improved, and the exhaust temperature is reduced. Even if the evaporation temperature is low (-40 ℃) and the compression is relatively high (about 25), it can still operate in a single stage, that is, within a certain range Can replace the two-stage compression cycle. However, the processing and assembly of screw refrigeration compressors require high precision, which is not suitable for variable operating conditions, and there is a lot of noise. Under normal circumstances, noise reduction and sound insulation equipment are required. Lubricating oil requires more auxiliary equipment such as oil pump, oil cooler and oil recoverer.
A Helmholtz resonator is closed and connected to the outside of the compressor housing, that is, the cavity of the Helmholtz resonator is connected to the cavity inside the compressor housing through the hole neck to reduce the amplitude of the excited acoustic mode in the compressor cavity. Modulating the resonance frequency of the resonator to the maximum excited vibration mode of the actual compressor cavity will greatly reduce the resonance peak and cause a significant change in the response spectrum. But this will affect the appearance of the compressor and the layout in the refrigerator, and its research results have not been applied to the product.
The compressor as the most critical component of the transcritical carbon dioxide air conditioning system's efficiency and reliability should be fully redesigned in conjunction with the specific characteristics of the carbon dioxide supercritical cycle. CO2, like ammonia, has a high adiabatic index K value of 1.30, which may make the compressor discharge temperature higher, but because the pressure ratio of the compressor required by CO2 is small, there is no need to cool the compressor itself. Because of the high thermal insulation index and small pressure ratio, the re-expansion loss of the compressor's clearance volume can be reduced and the compressor's volumetric efficiency can be higher. After experimental and theoretical research, Jurgen SUB and Horst Kruse found that the reciprocating compressor has a good oil film sliding seal and has become the first choice for CO2 systems. BOCK has improved its carbon dioxide compressor exhaust valve, and the efficiency of the improved carbon dioxide compressor has increased by 7%.
The remaining amount of lubricating oil and the winding of the motor end coil will also cause a difference between the sound levels of batch compressors of the same model (deviation from the average value of the sound level). Increase the torsional stiffness and reduce the vibration surface by changing the external support of the shell; the complexity of noise research requires researchers to have a strong theoretical quality, require enterprises to have a good technical foundation, and require large investment and long time. This aspect is one of the weak links of Chinese compressor companies, basically in the stage of qualitative experimental research, accompanied by a lot of randomness and chance.
The application of new refrigerants based on environmental protection requirements is also a hot issue in the refrigeration compressor industry. With the end of the R22 refrigerant replacement work for refrigerator products, the research of new refrigerant compressors is mainly concentrated in the air conditioning industry. In addition to the relatively mature R410A, R407C research, the biggest hot issue is the study of carbon dioxide compressors. Because the pressure of the carbon dioxide system is much higher than that of the traditional pressure-critical circulation system, the shaft seal design requirements of the compressor are much higher than the original compressor, and the leakage of the compressor shaft seal will still be the main reason hindering its practical use for a period of time. .
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