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1 Wang Jun. Development of high-efficiency mine local ventilators. Mechanical Science and Technology, 1999 (18) 3 2 Lu Wencan. Several problems in the design of the cyclone. Chemical and general machinery, 198 (11) 3 Wang Mingde. The overall optimized design of the axial flow fan. Journal of Xi'an Jiaotong University, 1985; (5) 4 Wang Jun. Mine design for the cyclone. In-flow simulation and experimental research. Ph.D. Thesis of Northwestern Polytechnical University, teaching and research work of 1999 Body Mechanics, participated in the optimization of energy-saving control of the drainage system. Research and development projects for high-efficiency fans. Mailing address: 710049 Department of Mechanical Engineering, Xi'an Institute of Science and Technology, Xi'an, Shaanxi.
Conception and development of gear compressors Deng Hanchang's pressure fluid injection work and oil seal method of Fuzhou Refrigeration Plant transformed the current gear pump into a gas compressor. This type of compressor has many advantages and has been confirmed by preliminary prototype tests.
Preface Gear-type liquid pump has been widely used, and its advantages are simple construction of two gears and one machine. The precision requirements are not high, the work is reliable, the fault is low, and the efficiency is high. The main part gears can be manufactured by powder metallurgy, saving materials and low cost. If some technical methods are used to transform it into a gas compressor, the economic benefits are very significant. This article focuses on the implementation of the gear compressor, working principle and operational test results.
2 gear compressor implementation design gear compressor must solve two problems: change the isometric compression work of the liquid pump into variable capacity compression work, change the isometric gas transmission of the cogging into variable volume gas, do There is compression.
Effectively eliminate leakage and backlash in the compressed gas machine.
According to Bernoulli's theorem, the pressure potential energy of the fluid can be completely transformed in the injection. The larger the pressure difference is, the higher the spray velocity is, and the two are linear. As the pressure in the cogging gradually rises, the injection gradually weakens and ends. Due to the "return" effect of the injection, the gear torque is reduced and the compressor shaft power is reduced. As shown in the figure, taking fuel injection as an example, AD is the fuel injection line. First, regardless of the cooling effect of the oil on the gas, there is: Lu product. V0P0 is a variable volume adiabatic compression. As can be seen from the above analysis, it is possible to solve the first problem with high pressure injection. The key is to reduce the loss. The current indication efficiency of the current working condition of the piston refrigeration compressor is 0. 835~0.85. The rework efficiency of the gear compressor should reach this level. The ejection efficiency of the streamlined shrink slit is 0.98, which completely solves the problem.
Solve the second problem using the "oil seal" method. In the past, the traditional method of relying solely on mechanical seals was used to build an oil pool in the lower part of the exhaust chamber to completely block the high and low pressure chambers. The compressor only dealt with oil leakage. The gas in the exhaust chamber does not penetrate the oil pool. The amount of oil leaking into the suction chamber during operation should be equal to that of the gear type oil pump, as long as the gas is not dissolved in the oil in a large amount. Compared with the piston type, this method has no clearance, no suction and exhaust valve, no air gap, and a high gas transmission coefficient U value.
In addition to solving the above two problems, engine oil has a third important role. One way of high pressure injection is the cold oil from the oil separation cooler whose temperature is close to the ambient temperature. The specific heat and specific gravity are much larger than the gas. The oil in the cogging is heated to 1C, and the gas is cooled by several tens of degrees. The gas is mixed, compressed and cooled by the cold oil, the temperature does not rise significantly, and the discharge temperature is close to the ambient temperature, so that cold exhaust can be achieved. The low discharge temperature also helps to improve the separation effect of the oil and is beneficial to the safe operation of the compressor. In a refrigeration system, the oil separation cooler actually performs part of the function of the condenser, that is, the cooling of the high temperature exhaust gas. However, it cools the gas in the internal tooth gap before the exhaust, which is a special feature of this solution, and also reduces the compression work. In the standard operating conditions, the ammonia discharge temperature has been reduced from adiabatic compression of 110C to 30C (ie, condensation temperature). The injection line is changed from AD to AD', and the compression work is also reduced to the ABCD'A area. The gear type air compressor can achieve high compression ratio isothermal compression, and the single-stage discharge pressure rises remarkably. In the refrigeration system, the condenser is also changed to a condenser, and the heat exchange area is greatly reduced.
The working principle of the geared compressor is as follows: the tooth gap is closed by the body and the front and rear end caps, forming a plurality of separate elementary volumes, and the low-pressure gas charged from the suction chamber is enclosed therein due to When the gear rotates, the gas in the suction chamber is continuously sent to the exhaust chamber. During the gas delivery, the oil and gas of the high pressure Pk are continuously injected into the slots in the tangential direction, pushing the slots forward, compressing and cooling the gas in the slots. The energy originally obtained from the compressor from the fluid is returned to the compressor. The ammonia system dynamometer is shown as a standard refrigeration condition.
Gear type P-V indicator diagram The first injection slit is supplied from the oil separation cooler. The pressure difference is the largest (Pk P0), the injection is the most intense, and the cogging thrust is the largest. After the injection, the pressure in the cogging is increased from P0=0.24 MPa to 0.36 MPa. The second injection slit supplies oil from the oil pool of the exhaust chamber, and the cogging pressure rises to 0.70 MPa after the injection. The third injection slit is The jet is supplied with high-pressure steam from the exhaust chamber air tank. After the injection, the pressure in the cogging rises to Pk, which is 1.17MPa, the pressure difference disappears, and the injection-type rotary compressor is mainly based on mechanical compression, and the fuel injection amount is small. The temperature is high. It can be seen that the amount of work of the high pressure fluid during the injection process is much at ambient temperature. A change from (Pk-Po) to zero. Then, the high-pressure tooth groove enters the exhaust chamber, and the gas inside is driven out of the tooth groove by the oil of the oil pool, occupying the volume of the lower part of the exhaust chamber, and pushing the high-pressure gas in the upper part of the exhaust chamber out of the compressor. The gullet continues to be immersed and then meshed from bottom to top and corresponding teeth below the oil level, and the oil filled in the gullet is again displaced from the bottom to the upper by the meshing teeth. This process is identical to the gear pump. When the tooth groove that has drained the oil enters the suction chamber, the inflation is restarted, so that the working process of the compressor is continuously repeated. The oil injected into the cogging is concentrated at the crest behind the tooth groove due to the centrifugal force, effectively preventing the backflow of gas in the tooth groove. Since the centrifugal force direction and the injection direction are at an angle of 90 degrees, the oil accumulation does not change the mechanical seal to an oil seal, the gas leakage is substantially eliminated, the volumetric efficiency is high, and the gas transmission coefficient U value is large.
Compared with the screw compressor, the equal pressure compression and the isometric expansion do not occur in the operation of the gear compressor. When the pressure in the cogging does not rise to Pk, the injection does not stop. When the pressure reaches Pk, the pressure difference disappears and the injection cannot continue. The final pressure of compression in the cogging can only be the pressure Pk. Compared with the piston compressor, the gear compressor does not exhibit pressure abnormality in the compression space, and there is no resistance loss of the suction and exhaust valve. The piston compressor does not have the piston compressor shown and the ~2 loss.
(1) Breaking the tradition of first exhausting and then cooling the compressor, fully synchronizing compression and cooling, first cooling and then exhausting. Compression refers to rapid sliding back and forth within the cylinder. The screw compressor has a long contact fold line, which is forward-shifting during operation, pure sliding, and its mechanical efficiency is small. 9 Power consumption is low. The elimination in the figure will result in various jets back to the PubliSingHousebookmark3. Finally, the oil is plunged into the oil pool by the cogging speed at the top speed ve, so that the impact of the high-speed oil on the oil surface is transmitted to the bottom of the oil pool, the thrust of the meshing teeth is added, the gear torque is reduced, and the fuel injection belt is absorbed. Speed ​​"remaining kinetic energy". The oil level of the oil sump is controlled by the overflow plate of the vent. The excess oil flows over the overflow plate down the bottom of the horizontal exhaust pipe back to the oil separation cooler. It can be seen that the oil sump of the compressor is an important mechanism, which has four kinetic energys such as strengthening the tooth lubrication, oil seal, driving out the cogging, and absorbing the remaining injection oil.
The exhaust gas of the compressor enters the oil separation cooler, where it is washed and cooled by cold oil to remove oil. The bubble rises to the oil level, and becomes a low-speed airflow, losing the ability to carry oil. Since the temperature is not high, it is close to the ambient temperature, and there is no oil vapor (in the vapor refrigeration system, the exhaust gas is saturated steam here). A clean saturated gas decondenser dissipates heat. The oil separated from the exhaust gas and the oil returned from the oil sump overflow plate are cooled by the water pipe to be cooled, and then sent back to the first injection slit of the compressor by the oil pipe, and re-injected into the tooth groove, which is repeated. If it is accidental, the cogging is not filled with gas but liquid or oil in the suction chamber, then it does not matter. At this time, the cogging will not be sprayed on the way to the exhaust chamber, and the gas compressor will naturally become a liquid pump, and no dangerous liquid impact will occur. It can be seen that the gear compressor is an inhalable gas. A liquid-free compressor that can also be aspirated. From the above analysis, the gear compressor is a special type of positive displacement compressor rotary fluid compressor.
4 Gear-type compressor thermodynamic characteristics self-adjusting effect: It can automatically adjust when the working condition changes during operation, so that the compressor maintains low loss and high efficiency. Screw compressors do not have this performance. As long as Pk and P0 deviate from the design value and the compression ratio e changes, the loss increases. The piston compressor is even worse, and as the compression ratio e is larger, the efficiency is declining. When e reaches a certain value, it must be upgraded. Gear-type compressors do not, and their jet strength is synchronized with pressure changes. When Pk rises or P0 falls, the pressure difference increases, and it is not necessary to change the jet slit or adjust the body to automatically meet the need for rework, compression, and cooling, and vice versa. As long as the design is made correctly, the machine will maintain good performance over a wide range of pressures.
Low friction loss and high mechanical efficiency. The tooth tip and the end faces of the gear have a gap with the body and cannot be touched. Only in the meshing position, the two gears are fully lubricated in the oil pool due to the contact line of the transmission, and are continuously rolled from the root of the driving gear to the top of the tooth. The rolling friction component is mostly, and the friction coefficient is small. The piston type compressor is driven by a crankshaft connecting rod, pushing or pulling the piston with a piston ring. ElectronicPubli Jianfu i City Cangshan District Cangli three 53° room rved. Since the cogging gas transmission process is always closed, so in the initial stage of pressure It is also possible to suck a few different pressure gases from small to large and then spray the oil. With the "intermediate suction" plus the suction volume of the compressor, the large cooling capacity and the compressor volume are not large, the various losses are not added, and the efficiency is greatly increased. The middle suction injection into the tooth gap also has the above functions of reducing power, pressure and cooling.
In addition to reducing losses, multiple compressors can also achieve a specific function of a refrigeration compressor while carrying several refrigeration temperatures. In the case of multiple levels of required temperature, such as household refrigerators, the installation of this special refrigerator can fully achieve the close proximity of the evaporating temperature of each level with the required temperature of the various levels, and the result is naturally power saving, and Reduce the working volume and reduce the size of the machine.
The special losses of geared compressors are: injected oil, oil leakage during operation, fluid injection loss and loss caused by high-speed agitation of the oil pool. According to preliminary calculation and analysis, the sum of the values ​​is less than the first point. The power gear type compressor that is saved by the exhaust is easy to manufacture, and the precision is the same as that of the gear type oil pump. The gear is mainly subjected to radial force, the axial thrust is small, and the assembly process is easy. The oil is mainly responsible for five functions: lubrication, sealing, compression, rework, and cooling.
The test prototype is a self-made external gear type compressor.
The compression gear is two identical straight tooth involute shift gears. Modulus m=5, 10 teeth, displacement coefficient d=0.4126 gear thickness b=50mm, rotation speed n=1440r/min. The cogging volume is calculated as heart=2å²µ(d-Rd/12) as V=6.826m3/ h. The author has successfully performed compressed air and ammonia refrigeration tests on the prototype. The simple system of the refrigeration test is as shown. The oil separation cooler was replaced by an intercooler. After more than half a year of running tests, the prototype startup, suction, exhaust and boost were normal. When the ammonia refrigeration test is performed, the evaporator is well frosted and the ammonia cycle is normal.
The prototype operation is in line with theoretical estimates and the exhaust temperature is indeed very low. For air, when the exhaust pressure is 1.5 CMPa (gauge pressure), the single-stage adiabatic compression exhaust gas temperature is about 400 C; for ammonia, the standard cooling service adiabatic compression exhaust gas temperature is about 110 ° C. The prototype did both of these operations for a long time, and the hand touched the exhaust pipe without any heat.
When the ammonia refrigeration test system (gauge pressure) is sequentially raised to 1.0 MPa (gauge pressure), the gas transmission coefficient X value is successively reduced from 0.98 to 0.77. This is very high for the piston compressor, but this is the same as the estimated number. deviation. Later, in many disassembly and assembly, the problem was found in that the gear of the prototype did not have axial positioning. During operation, the gear was rotated tightly to one end, so that the gap at the other end was doubled, and the oil leakage to the suction chamber was three times larger. If this problem is solved in the future, the expected value can be increased to 0. Prototype oil absorption test: first add a Rubber Hose at the suction port, when the prototype is running normally, the exhaust pressure is stable at 1.0MPa (gauge pressure), that is The rubber tube is inserted into the oil drum, at which time the compressor sounds slightly lower and the current does not rise much. A barrel of oil quickly absorbs light, the oil separation cooler oil level rises slightly, and then the machine returns to the original inhalation sound, and the current drops to the original number.
According to the test observation, since the exhaust gas temperature is low, the oil in the exhaust gas can be removed, and no oil trace is found. After half a year, the oil surface is basically unchanged.
The gear balance performance is good, the high-speed rotary vibration is small, the noise is low, and the sound is soft.
It can be seen that the gear compressor will change the face of China's refrigeration industry and has its application prospects in many sectors of the national economy.