1、 毕业设计 (论文 )外文翻译 学生姓名 专业班级 机械 06-4 班 指导教师 职 称 所在单位 机械工程学院 教学部主任 完成日期 2010 年 6 月 16 日 1 Pneumatic Transmission Similar to hydraulic transmission, pneumatic transmission performs the function of energy transfer and control by the medium of flow. They have a great deal in common in the aspects of workin
2、g principle, components structure, system composition and graphic symbol. The readers should notice their differences.A pneumatic system incorporates the following components and devices: (1)Air supply devices: They include pressure generation devices, air regeneration and storing devices, F. R. L.
3、(air filter, pressure reducing valve and oil mist lubricator) combination, etc. It provides qualified compressed air for pneumatic systems. (2)Actuators: They convert the compressed air pressure into mechanical energy, such as air cylinders and air motors. (3)Control elements: They are used to contr
4、ol the pressure, flow rate and moving direction for the components, such as valves. (4)Pneumatic attachments: They incorporate the components which are used to cool, silence, purify, and lubricate compressed air and those to joint each component. 1.1 Air Supply Devices Air supply devices are used to
5、 provide compressed air for pneumatic systems. An air supply device is an important part of a pneumatic system, which supplies qualified compressed air (with a certain lever of pressure, flow rate and purification) for the pneumatic system. Generally, for the delivery surpasses or equals 6 - 12m/min
6、, a compressed air station is needed. But for the delivery less than 6 - 12m/min.the air compressor can be mounted besides the pneumatic equipment directly. An air supply device incorporates four parts: pressure generation devices, air regeneration and storing devices, air lines and F. R. L. combina
7、tion. Normally the first two parts are located in compressed air station as a center to supply gas in industry or workshop. Air compressor: pressurize atmospheric air； Cooler: cool compressed air； condense water and hydrocarbon vapours； Oil and water separator: remove gross solid and liquid particul
8、ates； Receivers: air storage； settling chamber for particulates； cool air； Air dryer: further reduce water and oil vapour content； Air filter: further remove desiccant dust and fines. In a pneumatic system, the compressed air flowing out from receiver is for general use and that from another receive
9、r is for special use (such us the control circuits composed by 2 pneumatic meters or fluidic elements). 1.1.1 Pressure generation devices Compressor is one type of pressure generation devices, which converts mechanical energy into pressure energy. Compressors can be classified according to their wor
10、king principles, structures or performance properties. (1) According to working principles: Displacement and dynamic； (2) According to structures (3) According to output pressures: Low pressure (0.2 - 1.0MPa), medium pressure (1.0 - 10MPa), high pressure (10 - 100MPa), super high pressure (100MPa).
11、(4)According to output flow rates(delivery): Mini (100 m/min). 1.1.2 Purification and storing devices and equipments for compressed air Normally, purification equipments for compressed air involve: cooler, a moisture separator, a receiver and an air dryer. 1.1.2.1 Cooler:cooler is usually set at the
12、 outlet port of the compressor and serves as a heat exchanger to cool compressed air after leaving the compressor. Cooling can reduce an air temperature of 120 - 150C to 40 - 50C. Coolers can be further classified based on their arrangement: coil tubular type, series tubular type, thermosyphon syste
13、m and tube drive type. There are two types of cooling: water cooling and air cooling. 1.1.2.2 Moisture separator: it is used to separate the impurities such as condensed water and oil stain from the compressed air to gain an initial purified compressed air. When compressed air enters the separator,
14、its flow rate and velocity will change sharply and the impurities with a higher density initially purified. The configurations of separators incorporate: ring revolving type, strike and return type, centrifugal rotary type, water-bath type, etc. This is a strike and return type moisture separator. W
15、hen the compressed air enters the separator, it strikes against the baffle and turns sharply before falling down. When air falls down, it again strikes the case bottom and then rises up. The water droplets and oil are then separated from the compressed air by the centrifugal force produced by the sh
16、arp turning action. 1.1.2.3 Receiver: it is used to store a certain amount of compressed air, reduce its pressure fluctuation and provide gas continuously and stably. There are two types of receivers: horizontal and vertical. Vertical type receivers are more often adopted to save room. Nowadays, the arrangement with the combination of cooler, moisture separator and receiver has found many applications. 1.1.2.4 Air dryer:the compressed air after having been purified and treated by the cooler,
