Briefly explain the principle, advantages and disadvantages of screw compressors The screw compressor has the characteristics of small size, light weight, easy maintenance, etc. It is a model that develops faster in refrigeration compressors. On the one hand, the screw profile and structural design have made great progress. On the other hand, the introduction of special milling machines for screw rotors, especially grinding machines, has improved the machining accuracy and processing efficiency of these key parts, which has effectively improved the performance of screw compressors. At present, screw compressors are mainly used in compressed air and medium-sized refrigeration heat pump air conditioning systems. Due to the continuous improvement of the working reliability of the screw compressor, it has gradually replaced the reciprocating compressor in the range of medium refrigeration capacity, and has occupied part of the market of the centrifugal compressor. working principle
1. Inhalation process When the rotor rotates, the groove volume gradually expands with the rotation of the rotor, and communicates with the suction port. The gas from the evaporation system enters the groove volume through the orifice for the gas suction process. After the rotor rotates to a certain angle, the interdental volume crosses the suction orifice position and is disconnected from the suction orifice, and the suction process ends. 2. Compression process When the rotor continues to rotate, the gas in the tooth groove closed by the body, the suction end seat and the exhaust end seat is pressed toward the exhaust end due to the mutual engagement of the female and male rotors and the mutual filling of the teeth, and the pressure Gradually increase the compression process. 3. Exhaust process When the rotor rotates so that the cogging space communicates with the exhaust port on the exhaust end seat, the gas is pressed out and discharged from the exhaust flange port to complete the exhaust process. Because the above three processes must occur in the working cycle of each cog slot, when the compressor is running at high speed, several pairs of cog slots' working volume repeat the suction, compression and exhaust cycles, so that the compressor's output The gas is continuous and stable. classification The common products of screw compressors are screw air compressors commonly known as screw air compressors, screw refrigeration compressors and screw process compressors. Screw compressors are more and more widely used. Various open and semi-closed screw compressors have formed a series, and later a fully enclosed series of screw compressors has appeared. The twin screw compressor is abbreviated as screw compressor, which is composed of two rotors, while the single screw compressor is composed of a rotor and two star wheels. Their cooling and heating input power range has been developed to 10-1000KW, based on the screw type and A series of advantages of single screw compressor, its research and development fields are very wide, and the performance optimization potential is great. advantage Screw compressors are the same as piston compressors, and both belong to positive displacement compressors. In terms of use effect, the screw air compressor has the following advantages:
1. High reliability. The screw compressor has few parts and no wearing parts, so it operates reliably and has a long service life. The interval between overhauls can reach 40,000-80,000 hours. 2. Convenient operation and maintenance. The screw compressor has a high degree of automation, and the operator does not need to go through long-term professional training to achieve unattended operation. 3. Good power balance. The screw compressor has no unbalanced inertial force, the machine can work smoothly at high speed, and it can be operated without foundation. It is especially suitable for mobile compressors, with small size, light weight and small footprint. 4. Strong adaptability. The screw compressor has the characteristics of forced gas transmission, the volume flow is almost not affected by the discharge pressure, and it can maintain high efficiency in a wide range. It is suitable for a variety of working conditions without any change in the compressor structure. 5. Multi-phase mixed transmission, there is actually a gap between the rotor tooth surfaces, so it can withstand liquid impact, and can pressurize the liquid containing gas, dust-containing gas, easily polymerized gas and so on. 6. The flow of the spool valve is adjusted without backflow, which can effectively reduce energy consumption. Compared with reciprocating heavy-duty water-cooled compressors, screw compressors have a 30% lower initial investment per unit of horsepower. Naturally, in operation, screw compressors are one of the simplest types of compressors. Using oil injection to control the compressor discharge temperature is so effective that the compressor load is allowed to vary over a wide range. Disadvantages
1. High cost: Since the rotor tooth surface of the screw compressor is a spatial curved surface, special tools are needed to process on expensive special equipment. In addition, the machining accuracy of the screw machine cylinder is also high. 2. Cannot be used in ultra-high pressure occasions: Due to the limitations of rotor stiffness and bearing life, the screw machine is only suitable for low, medium and high pressure ranges, the exhaust pressure generally does not exceed 10MPa, and the ultra-high pressure is still dominated by the reciprocating machine .
