《vacuumpump真空泵》PPT课件.ppt

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1、Unit . Vacuum Pumps,Vacuum pumps,be concerned with 与相关 pumping mechanism: lowering the molecules number compression-expansion: piston pump（活塞） liquid ring pump（液环） rotary pump Roots pump Drag by viscosity(黏性） : vapor ejecting pump Drag by diffusion effect: vapor diffusion pump molecular drag: molecu

2、lar pump ionization effect: ion pump physical/chemical sorption pump: sorption pump, cryopump(低温）, gettering(吸气） pump,2.1 Principles of pumping,A sort of pump,Gas transfer pumps remove gas particles from the system. There are rotary vane pump, turbomolecular pump and diffusion pump in gas transfer p

3、umps. Entrapment pumps in which gas particles that have entered from the system are trapped either chemically or physically within the pump. There are sputter ion pump, sublimation pump and sorption pump in entrapment pumps.,Vacuum pumps can be classified as either gas transfer pumps or entrapment p

4、umps, according to their overall pumping mechanism.,VACUUM PUMPING METHODS,Sliding Vane Rotary Pump,Reciprocating Displacement Pump,Entrapment Vacuum Pump,Positive Displacement Vacuum Pump,Kinetic Vacuum Pump,Rotary Pump,Diaphragm Pump,Piston Pump,Liquid Ring Pump,Rotary Piston Pump,Rotary Plunger P

5、ump,Roots Pump,Multiple Vane Rotary Pump,Dry Pump,Adsorption Pump,Cryopump,Getter Pump,Sputter Ion Pump,Cold Trap,Ion Transfer Pump,Turbine Pump,Axial Flow Pump,Radial Flow Pump,Liquid Jet Pump,Gas Jet Pump,Vapor Jet Pump,Diffusion Pump,Diffusion Ejector Pump,Self Purifying Diffusion Pump,PUMP OPERA

6、TING RANGES,10-12,10-10,10-8,10-6,10-4,10-2,1,10+2,P (mbar),Rough Vacuum,High Vacuum,Ultra High Vacuum,High Vac. Pumps,Ultra-High Vac. Pumps,2.2 parameter and classification,ultimate pressure lowest pressure at its inlet leakage vapour pressure pressure range (useful pumping action) adjacent 相近的 pum

7、ping speed( function of pressure) The pumping speed is the volumetric flow through the pumps intake port. specific exhaust pressure selectivity 抽气选择性 composition of the residual gas from my point of view (viewpoint) in my opinion roughing pump: pumping to acceptable operating pressure backing pump:

8、maintance of required low pressure at the out let of another pump outlet/inlet operating pump: 启动压强 sub-: submicron, subsidiary company， subsequent immobilize 固定不动 mobile phone ionization电离 sorption 吸附,Pumping Speed,Selectivity,Molecular pump,Sorption pump,Rotary vane pump,Oil sealed rotary vane pum

9、ps are suitable for the direct production of rough and medium vacuum. They are also used extensively to back roots vacuum, turbomolecular and diffusion pumps.,Four stages in the cycle of a rotary vane pump,The mechanism, which is lubricated by oil, consists of a housing with a cylindrical bore into

10、which is fitted a rotor. The rotor turns, the tips of the blades are in contact with the stator wall at all times. Four stages in one revolution of the rotor are induction, isolation, compression and exhaust phases.,Mineral oils are the most commonly used fluids for rotary pumps. In general, oils av

11、ailable from a garage service station or store do not have a suitable low vapour pressure and none exhibit the service life or low level of back migration required for most process. Mineral oils offered by vacuum pump manufactures and other suppliers have been distilled to remove volatile components

12、.,The cross section of rotary vane pump,Schematic of a rotary vane pump,Rotary vane pump,Cross section of rotary pump,Image of rotary pump and parts,Rotary vane pump,Two stage rotary pump,constitute 组成 stator n.定子, 固定片 eccentric rotor n.偏心转子 vane/blade ：阀片 diametral slot n.缝, 狭槽 cylinder tubulation

13、n.管 dust filter 滤网 arrester plate: 锁定平板 sheet of neoprene n.丁晴橡胶垫（条） hinge 铰链 backing sleet 挡板 driving shaft 驱动轴 clearance 间隙 sliding fit: 滑动配合 spring 弹簧,rotating-vane pump/rotary pump,rounded end submerge top seal 顶端密封 exhaust valve 排气阀 intake 吸入量 cavity 空腔 volume rate pump displacement: 排气量 abrasi

14、ve material: 腐蚀性材料 dead volume: 余隙容积，有害空间 re- 又，再 discharge 排出 compression ratio: 压缩比 the main function of the oil: lubrication sealing filling the dead volume permanent gas total /partial gas Mcleod / pirani gauge reading 读数 Parallel/series connection 并/串连,dead volume,Pumping speed curves fall off

15、下降 noticeable obvious gas ballast 气镇 condensible adj.可压缩(凝缩)的 contaminate vt. 污染 evaporate-condense,Gas ballast,1) Pump is connected to the vessel, which is already almost empty of air (70 mbar) it must thus transport mostly vapor particles 2) Pump chamber is separated from the vessel compression be

16、gins 3) Content of pump chamber is already so far compressed that the vapor condenses to form droplets overpressure is not yet Reached 4) Residual air only now produces the required overpressure and opens the discharge valve, but the vapor has already condensed and the droplets are precipitated in t

17、he pump.,Without gas ballast,Gas ballast,Pump is connected to the vessel, which is already almost empty of air (70 mbar) it must thus transport mostly vapor particles 2) Pump chamber is separated from the vessel now the gas ballast valve, through which the pump chamber is filled with additional air

18、from outside, opens this additional air is called gas ballast 3) Discharge valve is pressed open, and particles of vapor and gas are pushed out the overpressure required for this to occur is reached very early because of the supplementary gas ballast air, as at the beginning the entire pumping proce

19、ss condensation cannot occur 4) The pump discharges further air and vapor,With gas ballast,Roots pump,The Roots pump consist of two double-lobe impellers. These are rotated in opposite within the pump housing. The directions of rotation being those shown in the below figure. The impellers have ident

20、ical cross sections and are dimensioned and arranged so that a large enough part of the surface of R1 is a close fit to a part of the surface of R2 through the rotation. The impellers are also a close fit inside the pump housing. The rotating impellers do not, however, touch one another, nor do they

21、 touch the housing, but there is a small clearance (about 0.1 mm) at the points 1, 2 and 3. As point 1 moves around the inside wall of the pump housing, points 2 and 3 move correspondingly.,Roots pump,Action of Roots pump,Since the inlet port is isolated in fact from the outlet by a narrow gap (clea

22、rance between parts) there is a back flow of gas from the exhaust region to the inlet region, and therefore the efficiency of compression is much lower than in the case of oil sealed pumps. However, the absence of rubbing contacts means that higher speeds of rotation (1000-4000 rpm) are possible, le

23、ading to much higher pumping speeds.,Processing,Cover Wear plate Rotary lobe Casing Shaft Gear box Sealing monitor,Roots pump schematic,Pumping speed curve of Roots pump,Roots pump,Double-lobe impeller 双叶转子 Housing 框架，泵体 identical 相同的 close fit clearance, narrow gap back flow 回流 efficient, effective

24、 oil sealed pump Rubbing contact Conductance 流导,molecular drag pump 牵引分子泵 Directional velocity 定向速率 Impart 传递 Turbomolecular pump Alternate Roting/stationary disc/plate Preferentially 优先的 Running clearance pitch angle 螺旋角, 螺旋上升角, (锥齿轮的)节面角 zero-flow compression ratio 零流量压缩比:The compression ratio (of

25、ten also simply termed compression) of turbomolecularpumps is the ratio between the partial pressure of one gas component at the forevacuum flange of the pump and that at the high vacuum flange: maximum compression k0 is to be found at zero throughput good compromise back diffuse: 反扩散 hydrocarbon n.

26、烃, 碳氢化合物,Classification of molecular pump: Molecular Drag Pump Turbo Molecular Pump Compound Molecular Pump Turbomolecular pump was invented by Becker (1958) and initially exploited commercially by A. Preiffer GmbH. The device is a multi-stage, bladed, axial flow turbine that compress gas according

27、to a mechanism that is gradually being established (Tu and Yang, 1987; Tu et al., 1988). This process occurs most efficiently under conditions of molecular flow. The theoretical pumping speed ; 102 103 l/sec Applications ; Nuclear technology Electronics and electrical industry Coating systems,Turbom

28、olecular pump,Pump Operation,Molecule,V,Moving Wall with Speed V (Drag),Principle of the molecular Pump,(Page 83 manual),molecular Pump,molecular drag pump,Holweck, 1913,Alcatel product,ROTOR BODY,HIGH PUMPING SPEED,HIGH COMPRESSION,EXHAUST,HIGH FREQ. MOTOR,INLET FLANGE,STATOR BLADES,BEARING,BEARING

29、,(Page 81 manual),Turbomolecular Pump,Rotor - stator assembly,(Page 82 manual),Schematic of turbomolecular pump,The turbo pump works by giving gas molecules a push in a particular direction by the action of rotating vanes. Imagine you are looking at the right side that is rotating about a horizontal

30、 axis. The diagonal lines represent the vanes which would be moving essentially and vertically on the page. A gas molecule is shown impinging from chamber on the upside, and as it enters the vanes it is given a velocity component down-and-to-the-right. In other words, the molecule is pushed toward t

31、he backing pump. On the other hand, if a molecule were incident from the right it would be pushed back in the direction from which it came when it encountered the vanes. In this way, a turbo pump maintains a pressure difference across itself by creating a preferred gas flow direction. In a typical t

32、urbo pump there are several rotating disks separated by stators with the vane angle decreasing at each stage.,The system of stator and rotor in turbomolecular pump,Turbomolecular pumps are designed to operate under molecular flow conditions. The physical basis for the pumping action is the interacti

33、on effect between a molecule and a moving surface. The short but finite residence time occurring when a molecule strikes a surface results in the molecule acquiring an additional velocity component in the direction of the moving surface.,Orientation of rotors and stators in a turbomolecular pump,The

34、 orientation of the moving (rotor) blades and stationary (stator) blades to the axial direction in a turbomolecular pump is as shown Figure. The molecule shown incident on a rotor blade and its pitch(斜度）. The stator blades are also pitched. Their pitch direction is such that they preferentially tran

35、smit molecules that have left the rotors and are moving axially down the pump. Molecules moving in the reverse direction (back-diffusion) are likely to be reflected back.,More detailed description of turbomolecular pump,For the blades to be effective with rapidly moving molecules, the blade speeds m

36、ust approach the molecule speeds; otherwise the molecules will pass through the rotor regions without being struck. Lighter molecules are more difficult for turbomolecular pumps to pump, because they are more likely to pass through the rotors without being hit by a blade, increasing the likelihood o

37、f back diffusion of the gas. Pump performance depends on blade design as well as rotor speed. Variables include the pitch angle, blade width and the distance between blades. Overall performance is optimized by varying the blade geometry through the pump. Ingestion（摄取） of foreign objects into any tur

38、bomolecular pump during operation will cause severe damage to the rotor and stator blade. In order to reduce this risk most pumps are provided with a wire mesh inlet guard.,Pumping selectivity,Pumping speed depends on the types of gas (molecular weight, momentum transfer) for the operation principle

39、,ADVANTAGES 1. Fast recovery from “Dumping” 2. Fast start-up 3. Constant speed 4. Clean ( No oil ) 5. Operating costs 6. High throughput 7. Small to large size,DISADVANTAGES 1. Sensitive to particulates 2. Requires mechanical pump 3. High rpm ( Noise/Vibration ) 4. Low speed for hydrogen and helium

40、5. High maintenance cost 6. 1 10-3 Torr upper limits 7. High initial cost,Advantages and disadvantages of the turbomolecular pump,Vapor pump: ejector pump and diffusion pump Distinction：mean free path at the intake port vs. throat width In relation to 关于 涉及 boiler Mercury Chimney Deflect 偏转 Umbrella

41、 伞形钟罩 Pressure gradient viscous drag and turbulent mixing Diminish, cross-section Orifice 孔 vapor booster pump: combination the diffusion and ejector pump,1 Nozzle (Laval) 2 Diffuser nozzle (Venturi) 3 Mixing chamber 4 Connection to the vacuum chamber,1 Steam inlet 2 Jet nozzle 3 Diffuser 4 Mixing region 5 Connection to the vacuum chamber,