Screw air compressor principle and structure diagram

FeaturesScrew refrigeration compressor as a rotary refrigeration compressor, both piston and power (speed type) features.1) Compared with reciprocating piston refrigeration compressor, screw refrigeration compressor has a series of advantages, such as high speed, light weight, small size, small footprint, low exhaust pulsation, etc..2) screw refrigeration compressor has no reciprocating mass inertia force, good dynamic balance, smooth operation, low base vibration, small foundation. 3) screw refrigeration compressor structure is simple, few parts, no valve, piston ring and other wear parts, its rotor, bearings and other major friction parts of high strength and wear resistance, good lubrication conditions, so less processing, low consumption of materials, long operating cycle, reliable, simple maintenance, and is conducive to the realization of the operation of the automation. 4) compared with the speed of the compressor, screw compressor has a mandatory Compared with the speed compressor, the screw compressor has the characteristics of forced gas transmission, that is, the displacement is almost independent of the influence of exhaust pressure, in the displacement of a small amount of time will not appear the phenomenon of wheezing, screw compressor in a wide range of operating conditions can still maintain high efficiency. 5) the use of slide valve adjustment, can realize the energy of the infinite adjustment. 6) screw compressor is insensitive to the inlet liquid, can be cooled by the injection of oil. Therefore, under the same pressure ratio, the exhaust temperature is much lower than that of piston, so the single-stage pressure ratio is high.7)There is no residual clearance volume, so the volumetric efficiency is high.2 Working Principle1.Inhalation Process:Screw air inlet must be designed so that the compression chamber can fully inhale the air. And screw air compressor has no inlet and exhaust valves, the air intake is only regulated by the opening and closing of a regulating valve. When the rotor rotates, the space between the teeth grooves of the main rotor and the vice rotor is maximized at the opening to the air intake end wall. At this point, the cogging spaces of the rotors are connected to the free air at the air intake. Since all the air in the cogging space is expelled during exhaust, the cogging space is in vacuum at the end of exhaust. The maintenance of screw air compressor reminds that when the air fills the whole groove, the inlet side end face of the rotor turns away from the inlet port of the casing, and the air between the grooves is sealed.2. Sealing and conveying process:At the end of the suction of the main rotor and auxiliary rotor, the tops of the teeth of the main rotor and auxiliary rotor are sealed with the casing. At this time, the air is sealed in the tooth groove and no longer flows out, i.e. the sealing process. The two rotors continue to rotate, the top of the teeth and teeth groove in the suction end of the overlap, the overlap surface gradually to the exhaust end of the move. 3. compression and fuel injection process: in the process of conveying, the meshing surface gradually to the exhaust port, that is, between the meshing surface and the exhaust port gap gradually decreases, the gas in the gap is gradually compressed, the pressure increases, known as the compression process. In the compression at the same time, due to the pressure difference, the lubricant is also sprayed into the compression chamber, and mixed with the gas inside the chamber. 4. Exhaust process: when the screw air compressor rotor meshing surface in the maintenance of the rotor to turn to the casing of the exhaust port, (at this time, the compressed gas pressure is the highest), the compressed gas began to be discharged until the top of the teeth and the tooth groove of the meshing surface to move to the exhaust end surface, at this time, the two rotor meshing surface with the casing exhaust port At this time, the distance between the two rotor meshing surfaces and the casing exhaust port is zero, that is, the exhaust process is completed. At the same time, the rotor meshing surface and the casing inlet between the groove length of the longest, the inhalation process is carried out again. Classification screw compressor is divided into open, semi-hermetic and hermetic. 1, hermetic: the body is made of high-quality low porosity cast iron, thermal deformation is small. The body adopts double-wall structure with exhaust channel, high strength, good noise reduction. The internal and external forces of the body are basically balanced, and there is no risk of open or semi-closed high pressure. The shell is made of steel with high strength, beautiful appearance and light weight. Adopting vertical structure, the compressor covers a small area, which is favorable for the arrangement of multiple chillers; the lower bearing is immersed in the oil tank, and the bearing is well lubricated; the axial force of the rotor is reduced by 50% compared with that of semi-closed and open type (the balancing effect of the motor shaft on the exhaust side); there is no risk of horizontal motor cantilevering, and the reliability is high; it avoids the effect of the self-weight of the screw rotor, the slide valve and the motor rotor on the matching accuracy, and improves the reliability. Good manufacturability. Vertical design of the screw without oil pump makes the compressor run or stop without oil shortage. The lower bearing is completely submerged in the oil tank, and the upper bearing is supplied with oil by differential pressure; it requires low differential pressure on the system, and in case of emergency, the bearing lubrication protection function can avoid bearing oil shortage lubrication, which is favorable for the startup of the unit in the transition season. Disadvantages:Using exhaust cooling, the motor is in the exhaust port, which can easily lead to motor coil burnout; in addition, faults can not be removed in a timely manner.2. Semi-hermetic screw compressor working temperature is low, the long life of the liquid spray cooled motor; open compressors use air to cool the motor, the working temperature is high, which affects the life of the motor, and the working environment of the machine room is poor; when the motor is cooled by the exhaust gas, the motor's working temperature is very high, and the motor's life is very short. Generally the external oil volume is large, but the efficiency is very high; the built-in oil is combined with the compressor, and the volume is small, so the effect is worse. The oil separation effect of secondary oil can reach 99.999%, which can ensure good lubrication of the compressor under various working conditions. While the plunger type semi-hermetic screw compressor through the gear drive to increase the speed, high speed (about 12,000 rpm), wear and tear, poor reliability. 3. open screw compressor open unit advantages are: 1) the compressor is separated from the motor, so that the compressor can be used in a wider range of applications; 2) the same compressor can be used for different refrigerants. In addition to halogenated hydrocarbon refrigerants, ammonia can be used as a refrigerant by changing the material of certain components.3) Depending on the refrigerant and the operating conditions, motors of different capacities can be used. The main disadvantages of the open unit are:1) the shaft seal is easy to leak, which is the object of frequent maintenance by the user; 2) the matched motor rotates at high speed, the airflow is noisy, and the compressor itself is noisy, which affects the environment; 3) the need to configure a separate oil separator, oil cooler and other complex oil system components, which makes the unit bulky, and the use of the maintenance is inconvenient.