1, working principle and characteristics Single screw compressor (see figure 1), which is mainly composed of a six-headed screw, two eleven-toothed star wheels and the machine body. Simple structure, small volume and lighter weight than piston 1/6. There are twelve times of air suction and exhaust when the screw rotates once. When the screw runs at high speed, the airflow pulsation is small and the displacement is large. Due to the symmetrical installation of the star wheel, the stress of the screw is completely balanced (see Figure 2), and the vibration is small, and the noise is lower than that of the twin-screw type by more than 10dB. Due to the stress balance of single screw, the maximum pressure of one compression is greater than that of double screw; Single screw is more energy-saving than twin screw, bearing size is not limited by twin screw, and life is longer. When the compressor runs at high speed, the compressed gas will generate a lot of heat energy, so it is necessary to spray oil or other liquids (water, liquid refrigerant, etc.). ) for cooling. Single screw compressor generally adopts liquid lubrication, but it can be divided into oil lubrication, water lubrication and refrigerant lubrication. Different from the working condition that the screw compressor has bending deformation, the single screw compressor can work in a small working gap because the screw is completely balanced, with small leakage and high volumetric efficiency. When the injector works in a small gap, the viscous shear loss caused by oil will lead to the increase of specific power. The products we developed have high volumetric efficiency and the ability to reduce specific power when working in a small gap.
2. Overview of foreign countries At present, Japan, the United States, Britain, France, the Netherlands and other countries are producing single-screw compressors based on the technology introduced by Hofert Company of France. 1) British single-screw refrigeration (air-conditioning) machine Hall Company changed the split type into the integral type, which improved the rigidity and accuracy of the whole machine, and set up the air inlet pipe to reduce the viscous shear loss of oil and improve the air inlet efficiency. The performance of oil-injection single-screw refrigerator (air conditioner) is better than that of double-screw refrigerator (air conditioner), but the level is lower than that of Japan. Compare with that original twin-screw refrigerator produced by Daikin company, the single-screw refrigerator produce by Daikin company in Japan has a full load efficiency of 25% and a partial load efficiency of 40%. In the 1980s, Mitsubishi Corporation of Japan created its own high-precision processing and assembly technology, and the oil-free single-screw refrigerator (air conditioner) produced reduced the viscous shear loss of oil, saving 5% energy compared with the oil-injected single-screw refrigerator (air conditioner), and now the level has been further improved. The performance of large-scale oil-free single-screw refrigerator (air conditioner) has reached or surpassed that of the most energy-saving but expensive turbo refrigerator (air conditioner), and it has become the best refrigerator (air conditioner) in the contemporary era, which is also the development direction of refrigerator (air conditioner). The market prospect is good, and it can only be produced in Japan at present. Its cost is much lower than that of turbine type, but its price is higher. Single screw refrigerator (air conditioner) has high added value and good economic, economic and social benefits. 2) The comprehensive performance of single-screw compressor for process, especially its good reliability and easy computer control, is especially suitable for process flow, which is used to compress various gases in natural gas gathering and transportation, coal seam degassing, land gas injection, acid gas compression, gas turbine pressurization, steam recovery and various chemical production processes. Dreiser-Rand Company of the United States once purchased the screw and star wheel assembly machine of Mitsui Seiki Company of Japan, but it has stopped production at present. 3) Oil-injected single-screw air compressor This product has the largest output and the widest application among screw compressors, and its level is the highest in Mitsui Seiki Corporation of Japan. The company began to produce compressors in the 1930s. After the introduction of single-screw compressor in the 1970s, a high-precision machine tool with screw and star wheel was developed, and the processing and assembly technology was mastered. The whole machine was adopted, and the products were controlled by computer. In addition to producing single-screw compressors, we also provide screws, star wheels or main engines to European, American and Japanese manufacturers for producing single-screw compressors. Although the price of oil-injected single-screw compressor is higher than that of twin-screw compressor in the international market, it still accounts for 50% of the market. 4) Water-jet single-screw air compressor The demand for compressed air for medicine, food, electronics, new materials and high-tech products has increased and the awareness of environmental protection has increased, so has the demand for oil-free air compressors. Water-spraying single-screw compressor can provide clean compressed air (the air already contains water) because it avoids oil pollution, and at the same time greatly reduces the viscous shear loss caused by oil injection, which has a particularly good energy-saving effect; The water-jet single-screw compressor produced by Grimeyer Schmidt Company of the United States was established in the 1990s, saving 20% energy compared with the two-stage compression twin-screw compressor. The demand of water-jet single-screw compressor is increasing day by day. After a lot of experiments on more than a dozen compressors, the US Navy thinks that single-screw compressor is the best compressor for submarines and other ships, and high-pressure oil-free compressor is the only choice. The price of water-jet single-screw compressor is much higher than that of oil-jet compressor, but its economic benefit, social benefit and market prospect are very promising. Single-screw compressors for various purposes have excellent performance, broad market and good benefits. The invention patent of high-priced single-screw compressor has expired, and some countries are stepping up research and development.
3. China Beiyitong Overview Beiyitong is the earliest single-screw compressor manufacturer in China. In 1976, the prototype was developed, and the service life of the meshing pair was only tens of hours. The factory failed to break through the key technology for a long time, and once reached a complete technical agreement with CP Company of the United States to introduce single-screw compressor, but later the United States unilaterally terminated the contract. North Yitong only got the prototype and incomplete drawings (the most critical screws and star wheel drawings are missing). After that, the factory made many efforts to seek introduction, but so far it has been fruitless. Wenling Chemical Machinery Factory and Subei Refrigerator Factory successively cooperated with Xi Jiaotong University to develop single-screw compressors, but they failed to solve the processing technology of meshing pairs for a long time and gave up their research work. Wuhan Air Compressor Factory cooperated with Xi Jiaotong University to develop an oil-injected single-screw air compressor, which was a key project of the State Science and Technology Commission in 1986. In addition, the 704 marine water injection single screw air compressor is a key project of the Science, Technology and Industry Committee for National Defense, and its development is unknown. Other domestic units went to Beitong to transfer technical production prototypes to retired workers, and the level was lower than that of Beitong. Key technology The biggest difficulty in the production of single-screw compressor is the key technology, that is, the parameter design and optimization of screw and star wheel, and the tooth profile accuracy (machining accuracy and assembly accuracy) of two meshing tooth surfaces. By solving these two problems, single-screw compressors for various purposes can be mass-produced. 1. Parameter optimization of the screw and the star wheel When the star wheel engages with the screw, there is another yoke contact line formed by the secondary envelope besides a straight generatrix Q on the working tooth surface of the star wheel. These instantaneous contact lines correspond to the effective rotation angle φ of the star gear teeth in a certain interval, forming a continuous curved surface S. The curved surface S is above half of the generatrix Q and below the other half of the generatrix Q. For a large part of the curved surface S, only at a certain moment, that is, at a certain rotation angle φ, can the contact between the lead screw and the star gear yoke be realized. After (or before) invading the screw entity and disturbing it. This part of the S-surface is not available. The shape and characteristics of curved surface S are closely related to the parameter setting of meshing pair. What we are facing is an "optimization" problem, whose "objective function" is how to maximize the available interval at the S plane within the effective rotation angle range, so as to increase the meshing area of the star gear tooth surface. And the service life of the meshing pair is effectively prolonged. 2. High-precision special machine tool High-precision special machine tool is an indispensable equipment for processing high-quality screws and star wheels, which is the key to the whole project and the focus of foreign blockade of China. In the past, some experts thought that the precision requirement of special plane transmission chain was too high to reach in China. At present, with the wide application of CNC servo system, it is possible to manufacture a special plane composed of the shortest transmission chain and ultra-high precision transmission components. 3. The linear envelope of foreign cutter is the only profile of single screw compressor. The tooth surface of this kind of screw is not developable and cannot be processed by grinding. It is the only feasible machining method to use finger milling cutter for rough machining and turning for finish machining. Star wheel processing has been an unsolved problem in China for more than 20 years. Now we have solved this problem theoretically and practically. When designing the star wheel, the contact area of the meshing pair in the whole meshing angle interval should be increased as much as possible. We calculated the three-dimensional coordinates of the star gear tooth surface and its first and second differential neighborhood characteristics, and designed an efficient razor, which can process the star gear tooth surface accurately without theoretical error.
4. Processing technology and assembly technology Processing technology is the core of single screw compressor technology. If you master it, you can develop a high-precision special plane that does not depend on imports. Otherwise, the high-precision special plane can also produce high-quality compressors. No matter how high the machining accuracy is, the assembly is not correct, and the previous efforts are in vain. The precision of machining and assembly focuses on the meshing of tooth surfaces. Under the condition of no running-in, the meshing pair shall realize simultaneous meshing of all tooth surfaces in the meshing area, and the total meshing area of each tooth surface shall not be less than 90%. Product use and market Single-screw air compressor is mainly used in petroleum, chemical industry, energy, transportation, machinery, metallurgy, mining, construction, medicine, food and other fields. Such as pneumatic tools, pneumatic fixtures, automatic control, precision measurement, sandblasting, painting, pneumatic conveying of bulk materials (cement, pulverized coal, powder, etc.). ), etc. Among them, the oil-free single-screw compressor can provide clean energy and save energy, and the market demand is increasing day by day. Single screw compressor is used to compress all kinds of gases except air, mainly used in chemical production process. It is also used for the transportation of natural gas and natural gas. Single screw compressor is the best type of refrigeration (air conditioning) machine, and it also has important military uses, such as submarine and missile launch. In western developed countries, screw compressors have basically replaced piston compressors, with a market share of nearly 80%. Atlas in Sweden produces about 654.38+0.8 million twin-screw compressors every year, and I-R in the United States produces about 0.9 million compressors every year. The domestic 1986 screw is only 2%, accounting for about 30% in recent years, and the market potential is huge. As mentioned earlier, foreign businessmen and Taiwanese businessmen have seized the China market by taking advantage of technology and other aspects, and the sales situation is good. However, domestic manufacturers have poor sales. Sales situation is a trade secret, which is difficult to collect, but it can be seen from the production capacity; Liuzhou Dafu Machinery Co., Ltd. is newly established. The annual production capacity (Sino-Italian joint venture) is: 5,000 twin-screw compressors with an output value of more than 200 million yuan. The annual production capacity of national twin-screw air compressors is estimated to be more than 20,000. In 2002, the output value of screw compressor produced by Shanghai Fu Sheng Company reached 654.38+0.5 billion yuan, and the output value of Ingersoll Rand Air Compressor Factory reached 0.5 billion yuan. With the rapid development of national economy, the demand of single-screw compressor will increase day by day. Several points show that single screw compressor is a technology-intensive and labor-intensive product, and it is profitable to produce the whole machine with imported technology and purchased screws and star wheels. Our country adopts its own complete set of technology to produce, the quality is not lower than that of foreign countries, and the price advantage is obvious. Once the international market is opened, the output and benefit will be more considerable, which can drive the development of related industries, such as electronics, instruments and electrical appliances. In addition, the project will be put into production without pollution. There are four types of single screw compressors: CC, CP, PP and PC. One of the most energy-saving is the last PC, which is praised as an ideal freezer (air conditioner) by the inventor of single-screw compressor. The production technology of PC is the most difficult. At present, two companies can produce this type of air compressor. The appearance of PC eliminated CC. In addition, changing the shape of CP screw from cylindrical to conical will form a new type of machine. Just as PC mode is superior to CC mode, the new mode is more energy-efficient than CP mode.