VF-0.850空气压缩机的设计开题报告

欢迎下载本文档参考使用，如果有疑问或者需要CAD图纸的请联系q1484406321编号无锡太湖学院毕业设计（论文）相关资料题目： VF-0.8/50空气压缩机的设计 整体、曲轴箱部件、曲轴部件设计 信机 系 机械工程及自动化专业学 号： 0923166学生姓名： 李 达 指导教师： 俞萍（职称：高级工程师 ） 2013年5月25日目 录一、毕业设计（论文）开题报告二、毕业设计（论文）外文资料翻译及原文三、学生“毕业论文（论文）计划、进度、检查及落实表”四、实习鉴定表 无锡太湖学院毕业设计（论文）开题报告题目： VF-0.8/50空气压缩机的设计 整体、曲轴箱部件、曲轴部件设计 信机 系 机械工程及自动化 专业学 号： 0923166 学生姓名： 李 达 指导教师： 俞萍（职称：高级工程师 ） 2012年11月12日 课题来源 “VF-0.8/50空气压缩机的设计”的课题来源于企业； 结合所学知识，老师拟定题目； 综合大学里所学知识，将理论与实践相互结合。科学依据（包括课题的科学意义；国内外研究概况、水平和发展趋势；应用前景等）1、 化工、冶金、化肥、食品、医疗等众多企业的生产过程需要用到气体 压缩机，而活塞式空气压缩机由于有较高的压缩比，在高压气体生产 与输送中尚不能被其它设备所替代，是许多工程项目中的关键设备。2、 活塞式压缩机上所用的密封活塞环通常用自润滑材料聚四氟乙烯制 成，由于活塞环长期运行在剧烈的摩擦环境下，活塞环极易磨损，导 致压缩机不能正常工作。为了减少高分子材料的摩擦磨损，传统气体 压缩机活塞环需要用油润滑，以减少活塞环与气缸壁的摩擦磨损，提 高活塞环的使用寿命。3、 无油润滑压缩机采用自润滑聚合物复合材料制造活塞环，活塞部位不 用油润滑，所生产的压缩气体洁净无污染，既节省了大量的润滑油， 又可简化生产工艺流程，降低能耗，减少环境污染，是当前活塞式压 缩机的发展方向。4、目前压缩机制造业已经发展成为机械制造工业的一个重要组成部分。研究内容1、 活塞式空气压缩机的工作原理以及工作形成；2、 活塞式压缩机参数与结构的设计；3、 活塞式滑压缩机设计图纸的绘制。拟采取的研究方法、技术路线、实验方案及可行性分析研究方法：通过阅读有关资料，文献，收集筛选，整理课题研究所需的 有关数据，理论依据，综合运用所学理论知识研究论文课题。技术路线：分析活塞式空气压缩机的各个参数的取值情况，包括结 构参数、工艺参数、热力学参数和动力学参数。确定各参数 的具体数值或取值区间。可行性分析：通过对论文课题的学习研究，达到巩固，扩大，深化已学 理论知识，提高思考分析解决实际问题等综合素质的目的。研究计划及预期成果1、 首先对活塞式空气压缩机整体结构进行分析，对传动结构进行筛选，初步选择达到设计要求的结构方案；2、 对活塞式压缩机的热力部分及动力部分进行计算，通过压缩机机构的分析计算可提高其自身的精度；3、 对活塞式压缩机的主要零件进行强度校核，提高机构稳定性，稳定性。特色或创新之处 通过对活塞式空气压缩机的设计及计算，形成一整套现代的设计方法，对理论和实践的结合，起到整体的规划的作用，达到降低损耗提高效率，优化结构设计方便使用。已具备的条件和尚需解决的问题已具备的条件：拥有机械设计手册等参考资料及文献；到企业进行参观， 对空气压缩机进行直观的了解与认识，对所学的机械基础 知识有较好的掌握；能熟练运用CAD制图软件，提高作 图效率。尚需解决的问题：对于活塞式空气压缩机的工作原理不是非常清楚和熟悉，缺乏自主设计的经验。 指导教师意见 指导老师签名： 年 月 日教研室（学科组、研究所）意见 教研室主任签名： 年 月 日系意见 主管领导签名：年 月 日 CompressorsThe main difference between pumps and compressors is that the fluid delivered by compressors - air - is compressed and under pressure at the time it is delivered, even if there is no load on the system. Most devices used to compress air are very similar in concept and - perhaps even in hardware - to hydraulic pumps, and selection considerations are similar. The only other substantive difference is that most hydraulic systems are powered by a single pump that is actually a part of the system, whereas a host of pneumatic systems are often powered by a single compressor, which is almost a utility in the plant like water or electric service. Nevertheless, many small compressors are available for specific, discrete jobs; typically they are positive-displacement compressors. Dynamic, or nonpositive-displacement compressors are typically larger, facility-type units. Compressors are fairly simple devices, capable of long periods of maintenance-free operation if properly integrated into pneumatic systems. Yet time and again they suffer from early failures because obvious precautions were ignored during system design. Four basic rules can provide substantial improvement in compressor life with only moderate design effort:Pumps and compressors should be sized to provide at least the required pressure and flow, and preferably 10 to 25% more.Filters should be selected to protect the pumping unit, and sometimes to protect downstream components or products as well.Relief valves should be selected to keep pressure or vacuum at appropriate levels.Pumping units should be placed in a clean, cool, dry environment. Bellows compressors consist of a welded metal bellows connected to inlet and outlet ports with check valves. These compressors typically cover the pressure range up to 10 psig, and are used in pollution detecting and measuring devices, gas-sampling instruments, and medical applications. Lubrication is not needed, allowing high purities to be maintained. Vane compressors are simple machines with few moving parts. Like their hydraulic counterparts, vane pumps, the compressors are inexpensive, with low operating cost, and low starting-torque requirement. They are compact and relatively vibration free, with little pulsation in the compressor output. The sliding vanes are closely fitted in the rotor slots and wear very little during operation. These compressors are available in power ranges from 10 to 500 hp, at pressures to 150 psi. Reciprocating compressors consist of a piston moving within the cylinder to trap and compress the gas. In principle, such a unit is like an automobile engine, with the pistons compressing the gas and valves controlling its inlet and outflows. Sizes range from less than 1 to over 5,000 hp. Reciprocating compressors have good part load efficiencies and are useful for wide variations in operating conditions. Diaphragm compressors are a modification of the reciprocating compressor. Compression is performed by the flexing of a metal or fabricated diaphragm which is caused by the motion of a reciprocating piston in a cylinder under the diaphragm. The space between the diaphragm and the piston is usually filled with liquid. Lobed-rotor compressors have two rotating elements that revolve in opposite directions in a chamber. In most compressors, the rotors do not actually touch and do not drive each other, being driven instead by timing gears. Because the rotors do not actually touch, air leaks between them at a small but constant rate. This leakage, called slip, is constant for a given compressor at a given pressure. For highest efficiency, these compressors should be operated at maximum speed. They are available in power ranges from 7 to 3,000 hp, delivering pressures to 250 psi. Because the internal lobes do not contact, they need no lubrication. Liquid piston compressors have no moving parts in wearing contact. A rotor with multiple forward-curved blades rotates in an elliptical casing. Fluid, trapped within the casing, is carried around the inner periphery by the blades. Space between the blades changes volume due to the elliptical fluid path, and the inner surface of the liquid ring trapped between the blades serves as the face of a liquid piston. These compressors accept liquid slugs and fine particles without serious damage. Lubrication is required only in bearings located outside the pump housing. These compressors deliver up to 150 psi throughout the range of 10 to 500 hp. Centrifugal compressors are best suited to moving large volumes of air at relatively low pressures. Basically, they consist of a high-speed rotating impeller, a diffuser section where velocity is reduced and pressure increased, and a collector section that further reduces velocity and increases pressure. Centrifugal compressors can handle high flow demands well, but when demand decreases much below rated flow and output pressure rises, the compressors can surge. In surge, the pressure field at the compressor outlet varies randomly. If allowed to continue, this condition can damage bearings, blades, and even the housing itself. Centrifugal compressors typically use from two to six stages, supplying from 400 to 3,000 cfm at speeds to 20,000 rpm. Regenerative blowers (also known as peripheral blowers) use a disclike impeller with blades mounted around its outside edge. As the impeller revolves, air is drawn into the space between the blades. Centrifugal force moves the air in a spiral path outward to the housing, where it slips by the initial blade and returns to the base of the succeeding blade, where the process is repeated. In some models, a flow splitter creates two flow paths, so that the air must make two circuits around the impeller. In other models, the splitter is omitted, and the air makes only one circuit before exiting. Regenerative blowers provide air flows up to 1,000 cfm and pressures to 8 psi. Helical compressors look like two giant screws meshing together; they work much like hydraulic screw pumps. Maximum pressure from these machines is approximately 125 psi in single-stage configurations. Helical compressors may be either oil flooded or dry. Dry helical compressors, like lobed units, require timing gears to maintain proper clearance between the rotating elements. These units are most efficiently operated at high continuous speeds. Flooded compressors do not require any timing gears, because the oil-laden screw surfaces can drive each other. However, oil separators are needed to remove the oil from the air as it leaves the compressor. They are available over a power range of about 7 to 300 hp. Single-screw compressors are based on the same principle as helical compressors. As the central screw rotates, air trapped between the screw teeth is compressed against the star-shaped rotors. These compressors tend to have low vibration and noise levels, and low discharge pressures. Lubrication is required. Pumpsvacuum pumps In principle, industrial vacuum pumps are merely compressors run with the inlet attached to the vacuum system and the outlet open to exhaust. In smaller sizes, compressors and vacuum pumps are often identical machines. However, in the large sizes that might power a plant-wide vacuum system, the machines differ in minor ways that are intended to enhance efficiency for one application or the other. Manufacturers strongly advise that the same machine not be used for both vacuum and compression at the same time. The heavy loads will damage it. Three criteria control pump selection: degree of vacuum produced, rate of air removal, and power requirement. However, applications such as filtration may subject the unit to the ingestion of foreign material. The first pump performance criterion is the vacuum it produces. Manufacturers provide a maximum vacuum rating expressed as absolute pressure in mm Hg, or vacuum in in. Hg. Larger units are usually rated only for continuous duty, but smaller units may have a higher vacuum rating for intermittent duty. In smaller units, temperature-rise considerations limit the vacuum that can be produced. Continuous and intermittent vacuum ratings are determined for standard atmospheric pressure: 29.92-in. Hg. Lower ambient pressures reduce the vacuum that can be produced. The rating is determined from: where Va = adjusted vacuum rating, in. Hg; Vo = original vacuum rating at standard conditions, in. Hg; and Pa = anticipated atmospheric pressure at the application site, in.Hg.Rate of air removal is the second criterion. Vacuum pumps are flow rated according to the volume of air exhausted with no pressure differential across the pump. Manufacturers provide curves showing free air delivery at rated speed for vacuum levels ranging from 0-in. Hg (so-called open capacity) to maximum vacuum rating. Some manufacturers also provide curves of capacity at different speeds for a given vacuum. The last pump criterion is power requirement. Compared with air compressors, vacuum pumps require relatively little power. At low flows, vacuum (or pressure differential) is high; at high flows, vacuum is low. Therefore, power, which is proportional to flow and pressure differential, is generally low. Power output of the pump can be found from pressure-flow curves provided by manufacturers. Input power and speed requirements are also shown in the data. Overall pump efficiency (including both volumetric and mechanical efficiency) can be evaluated by combining this data. This is done by dividing the free-air capacity of the pump at the required vacuum level by drive power required at that condition. The result is proportional to the product of gage vacuum and air-flow rate and is representative of efficiency. All three performance criteria - vacuum, flow and power - can be affected by pump temperature. At higher vacuum levels, little air flows through the pump, so little heat is transferred to the air. Much of the heat generated by friction must be dissipated by the pump. This heat gradually raises pump temperature and can drastically reduce service life. Temperature excursions are especially important to intermittent-duty pump, which can overheat if on time greatly exceeds off time. Vacuum pumps are classified as either positive or nonpositive displacement. A positive-displacement pump creates vacuum by isolating and compressing a distinct, constant volume of air. The compressed air is vented out one port, and a vacuum is created at the other port where the air is drawn in. This generates relatively high vacuum, but little flow. A nonpositive-displacement pump, on the other hand, uses rotating impeller blades to accelerate air and create a vacuum at the inlet port. While nonpositive-displacement pumps cannot produce high levels of vacuum, they provide high flow rates. Principal types of positive-displacement vacuum pumps include piston, diaphragm, rocking-piston, rotary-vane, lobed-rotor, rotary-screw, and liquid-ring designs. Reciprocating-piston pumps generate relatively high vacuums - from 27 to more than 29 in. Hg - under a variety of operating conditions. Typical pumps of this type have one or more pistons linked to a rotating crankshaft. The alternating piston action moves air past check valves in the cylinder head to create a vacuum at the inlet port. Lubricated piston pumps are quieter, produce less vibration, have a higher capacity, and feature a much longer life than oilless designs, but they are also heavier and more expensive. Diaphragm pumps offer the advantage of the fluid chamber being totally sealed from the pumping mechanisms. An eccentric connecting rod mechanically flexes a diaphragm inside the closed chamber to create a vacuum. This results in somewhat lower vacuum compared to that produced by a reciprocating piston. However, the diaphragms lower compression ratio - low flow, large diameter, and short stroke - makes for quiet, economical, and reliable operation. The design is available in both one and two-stage versions. Single-stage pumps provide vacuum up to 25.5 in. Hg, while two-stage units are rated to 29 in. Hg. Rocking-piston pumps combine the compact size and quiet, oilless operation of the diaphragm pump with the high-vacuum capabilities of the reciprocating-piston pump. Here, a piston is rigidly mounted (no wrist pin) on top of the diaphragm units eccentric connecting rod. An elastomeric cup skirts the piston and functions both as a seal - equivalent to the rings on a piston compressor - and as a guide member for the rod. The cup expands as the piston travels upward, thus maintaining contact with the cylinder walls and compensating for the rocking motion. The absence of a wrist pin is the key to the pumps light weight and compact size. Single-stage rocking-piston pumps produce vacuum to 27.5 in. Hg; two-stage designs can generate 29 in. Hg or more of vacuum. Rocking-piston pumps are also relatively quiet, operating at sound levels as low as 50 dBA. A drawback to rocking-piston pumps is that they cannot generate a lot of airflow. Even the largest twin-cylinder models have flow rates of less than 10 cfm. Rotary-vane pumps use a series of sliding, flat vanes rotating in a cylindrical case to generate vacuum. As an eccentrically mounted rotor turns, the vanes slide in and out, trapping a quantity of air and moving it from the inlet side of the pump to the outlet. Rotary-vane pumps usually have lower vacuum ratings than piston pumps, in the 20 to 28 in. Hg range. However, there are a few exceptions. Some two-stage, oil-lubricated designs have vacuum capabilities up to 29.5 in. Hg. Pumps with recirculating oil systems reach still higher vacuums, in the less than 1-torr range. The pumps offer a number of advantages, including high flow capacities, low starting and running torque requirements, vibration-free operation, and continuous airflow. No valves restrict flow or require maintenance in the rotary design. The compact units are also quiet, generating as little as 45 dBA or sound. Depending on the application and vacuum level required, an economical alternative to using a high-vacuum pump is two standard, staged rotary-vane pumps. Or, a high-volume, low-duty pump rated for continuous duty of 20 in. Hg sometimes can be operated at restricted airflow or blanked-off conditions for short periods of time to provide higher vacuums. As with other types of pumps available in both lubricated and oilless configurations, lubricated rotary-vane pumps are capable of slightly higher vacuum compared to oilless designs. Liquid-ring pumps feature a multiblade impeller, mounted eccentrically in a cylindrical case that is partly filled with water. As the impeller rotates, liquid is thrown outward by centrifugal force to form a liquid ring concentric with the periphery of the casing. Due to the eccentric position of the impeller, the air space in the impeller cell expands during the first 180 of rotation, creating a vacuum. During the next 180 of rotation, the air space is reduced, discharging compressed air and water. In addition to being the compression medium, the liquid ring absorbs the heat of compression as well as any powder or liquid slugs entrained in the air. Rotary-screw and lobed-rotor vacuum pumps are two other types of positive displacement pumps. Neither lubricated design is as widely used as rotary-vane and piston pumps, especially in smaller sizes. Due to the size of t