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1、Unit.Vacuum Pumps05/10/2004Title2Vacuum 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:mo
2、lecular pump ionization effect:ion pump physical/chemical sorption pump:sorption pump,cryopump(低温）,gettering(吸气）pump2.1 Principles of pumping05/10/2004Title3A sort of pumpI.Gas transfer pumpsremovegasparticlesfromthesystem.Therearerotaryvanepump,turbomolecularpumpanddiffusionpumpingastransferpumps.I
3、I.Entrapment pumpsinwhichgasparticlesthathaveenteredfromthesystemaretrappedeitherchemicallyorphysicallywithinthepump.Therearesputterionpump,sublimationpumpandsorptionpumpinentrapmentpumps.Vacuum pumps can be classified as either gas transfer pumps or entrapment pumps,according to their overall pumpi
4、ng mechanism.05/10/2004Title4VACUUM PUMPING METHODSSliding VaneRotary PumpMolecularDrag PumpTurbomolecularPumpFluid EntrainmentPumpVACUUM PUMPS(METHODS)ReciprocatingDisplacement PumpGas TransferVacuum PumpDragPumpEntrapmentVacuum PumpPositive DisplacementVacuum PumpKineticVacuum PumpRotaryPumpDiaphr
5、agmPumpPistonPumpLiquid RingPumpRotaryPiston PumpRotaryPlunger PumpRootsPumpMultiple VaneRotary PumpDryPumpAdsorptionPumpCryopumpGetterPumpGetter IonPumpSputter IonPumpEvaporationIon PumpBulk GetterPumpCold TrapIon TransferPumpGaseous Ring PumpTurbinePumpAxial FlowPumpRadial FlowPumpEjectorPumpLiqui
6、d JetPumpGas JetPumpVapor JetPumpDiffusionPumpDiffusionEjector PumpSelf PurifyingDiffusion PumpFractionatingDiffusion PumpCondenserSublimationPump05/10/2004Title5PUMP OPERATING RANGES10-1210-1010-810-610-410-2110+2P(mbar)RoughVacuumHighVacuumUltraHighVacuumVenturiPumpRotaryVaneMechanicalPumpRotaryPi
7、stonMechanicalPumpSorptionPumpDryMechanicalPumpBlower/BoosterPumpHighVac.PumpsUltra-HighVac.Pumps05/10/2004Title62.2 parameter and classification ultimate pressure lowest pressure at its inlet leakage vapour pressure pressure range (useful pumping action)adjacent 相近的 pumping speed(function of pressu
8、re)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:maintance of required low pressure a
9、t 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05/10/2004Title7Pumping Speed10-1010-310-1Pumping Speed(Air)1234Inlet Pressure(Torr)Critical Point1.Compression Ratio Limit2.Constant Speed
10、3.Constant Q(Overload)4.Mechanical Pump Effect05/10/2004Title8SelectivityMolecular pumpSorption pump05/10/2004Title9RotaryvanepumpOilsealedrotaryvanepumpsaresuitableforthedirectproductionofroughandmediumvacuum.Theyarealsousedextensivelytobackrootsvacuum,turbomolecularanddiffusionpumps.Four stages in
11、 the cycle of a rotary vane pumpThemechanism,whichislubricatedbyoil,consistsofahousingwithacylindricalboreintowhichisfittedarotor.Therotorturns,thetipsofthebladesareincontactwiththestatorwallatalltimes.Fourstagesinonerevolutionoftherotorareinduction,isolation,compressionandexhaustphases.05/10/2004Ti
12、tle10Mineraloilsarethemostcommonlyusedfluidsforrotarypumps.Ingeneral,oilsavailablefromagarageservicestationorstoredonothaveasuitablelowvapourpressureandnoneexhibittheservicelifeorlowlevelofbackmigrationrequiredformostprocess.Mineraloilsofferedbyvacuumpumpmanufacturesandothersuppliershavebeendistille
13、dtoremovevolatilecomponents.The cross section of rotary vane pumpSchematic of a rotary vane pumpRotary vane pump05/10/2004Title11CrosssectionofrotarypumpImage of rotary pump and partsRotaryvanepump05/10/2004Title1205/10/2004Title13Two stage rotary pump05/10/2004Title14constitute组成statorn.定子,固定片eccen
14、tricrotorn.偏心转子vane/blade：阀片diametralslotn.缝,狭槽cylindertubulationn.管dustfilter滤网arresterplate:锁定平板sheetofneoprene 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 pump05/10/2004Title15 rounded end submerge top seal 顶端密封 exhaust v
15、alve 排气阀 intake 吸入量 cavity 空腔 volume rate pump displacement:排气量 abrasive 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/seri
16、es connection 并/串连dead volume05/10/2004Title16 Pumping speed curves fall off 下降 noticeable obvious gas ballast 气镇 condensible adj.可压缩(凝缩)的 contaminate vt.污染 evaporate-condense05/10/2004Title17Gas ballast1)Pump is connected to the vessel,whichis already almost empty of air(70 mbar)it must thus transp
17、ort mostly vapor particles2)Pump chamber is separated from the vessel compression begins3)Content of pump chamber is already so far compressed that the vapor condensesto form droplets overpressure is not yetReached4)Residual air only now produces the required overpressure and opens the discharge val
18、ve,but the vapor has already condensed and the droplets are precipitated inthe pump.Without gas ballast05/10/2004Title18Gas ballast1)Pump is connected to the vessel,which is already almost empty of air(70 mbar)it must thus transport mostly vapor particles2)Pump chamber is separated from the vessel n
19、ow the gas ballast valve,through which the pump chamber is filled with additional air from outside,opens this additional air is called gas ballast3)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
20、of the supplementary gas ballast air,as at the beginning the entire pumping process condensation cannot occur4)The pump discharges further air and vaporWith gas ballast05/10/2004Title19RootspumpTheRootspumpconsistoftwodouble-lobeimpellers.Thesearerotatedinoppositewithinthepumphousing.Thedirectionsof
21、rotationbeingthoseshowninthebelowfigure.TheimpellershaveidenticalcrosssectionsandaredimensionedandarrangedsothatalargeenoughpartofthesurfaceofR1isaclosefittoapartofthesurfaceofR2throughtherotation.Theimpellersarealsoaclosefitinsidethepumphousing.Therotatingimpellersdonot,however,touchoneanother,nord
22、otheytouchthehousing,butthereisasmallclearance(about0.1mm)atthepoints1,2and3.Aspoint1movesaroundtheinsidewallofthepumphousing,points2and3movecorrespondingly.Roots pump05/10/2004Title20ActionofRootspumpSincetheinletportisisolatedinfactfromtheoutletbyanarrowgap(clearancebetweenparts)thereisabackflowof
23、gasfromtheexhaustregiontotheinletregion,andthereforetheefficiencyofcompressionismuchlowerthaninthecaseofoilsealedpumps.However,theabsenceofrubbingcontactsmeansthathigherspeedsofrotation(1000-4000rpm)arepossible,leadingtomuchhigherpumpingspeeds.Processing05/10/2004Title211.Cover 2.Wear plate3.Rotary
24、lobe4.Casing5.Shaft6.Gear box7.Sealing monitorRootspumpschematic05/10/2004Title22Pumping speed curve of Roots pump05/10/2004Title23Roots pumpDouble-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 oil sealed pumpRubbing contactConductance
25、流导05/10/2004Title24 molecular drag pump 牵引分子泵Directional velocity 定向速率Impart 传递Turbomolecular pumpAlternateRoting/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(often also simply termed compression)of
26、 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.烃,碳氢化合物 05/10/2004Title25Classification
27、of molecular pump:Molecular Drag Pump Turbo Molecular Pump Compound Molecular PumpTurbomolecular 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 to a mechanism that is gradually
28、 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/secApplications;Nuclear technology Electronics and electrical industry Coating systemsTurbomolecularpump05/10/2004Title26Pump OperationM
29、oleculeVMoving Wall with Speed V(Drag)Principle of the molecular Pump(Page 83 manual)molecular Pump05/10/2004Title27molecular drag pumpHolweck,1913Alcatel product05/10/2004Title28ROTOR BODYHIGH PUMPING SPEEDHIGH COMPRESSIONEXHAUSTHIGH FREQ.MOTORINLET FLANGESTATOR BLADESBEARINGBEARING(Page 81 manual)
30、Turbomolecular Pump05/10/2004Title29Rotor-stator assembly(Page 82 manual)05/10/2004Title3005/10/2004Title31SchematicofturbomolecularpumpTheturbopumpworksbygivinggasmoleculesapushinaparticulardirectionbytheactionofrotatingvanes.Imagineyouarelookingattherightsidethatisrotatingaboutahorizontalaxis.Thed
31、iagonallinesrepresentthevaneswhichwouldbemovingessentiallyandverticallyonthepage.Agasmoleculeisshownimpingingfromchamberontheupside,andasitentersthevanesitisgivenavelocitycomponentdown-and-to-the-right.Inotherwords,themoleculeispushedtowardthebackingpump.Ontheotherhand,ifamoleculewereincidentfromthe
32、rightitwouldbepushedbackinthedirectionfromwhichitcamewhenitencounteredthevanes.Inthisway,aturbopumpmaintainsapressuredifferenceacrossitselfbycreatingapreferredgasflowdirection.Inatypicalturbopumpthereareseveralrotatingdisksseparatedbystatorswiththevaneangledecreasingateachstage.05/10/2004Title32Roto
33、rStatorPump inletPump outletThesystemofstatorandrotorinturbomolecularpumpTurbomolecularpumpsaredesignedtooperateundermolecularflowconditions.Thephysicalbasisforthepumpingactionistheinteractioneffectbetweenamoleculeandamovingsurface.Theshortbutfiniteresidencetimeoccurringwhenamoleculestrikesasurfacer
34、esultsinthemoleculeacquiringanadditionalvelocitycomponentinthedirectionofthemovingsurface.05/10/2004Title33OrientationofrotorsandstatorsinaturbomolecularpumpTheorientationofthemoving(rotor)bladesandstationary(stator)bladestotheaxialdirectioninaturbomolecularpumpisasshownFigure.Themoleculeshownincide
35、ntonarotorbladeanditspitch(斜度）.Thestatorbladesarealsopitched.Theirpitchdirectionissuchthattheypreferentiallytransmitmoleculesthathavelefttherotorsandaremovingaxiallydownthepump.Moleculesmovinginthereversedirection(back-diffusion)arelikelytobereflectedback.05/10/2004Title34Moredetaileddescriptionoftu
36、rbomolecularpumpForthebladestobeeffectivewithrapidlymovingmolecules,thebladespeedsmustapproachthemoleculespeeds;otherwisethemoleculeswillpassthroughtherotorregionswithoutbeingstruck.Lightermoleculesaremoredifficultforturbomolecularpumpstopump,becausetheyaremorelikelytopassthroughtherotorswithoutbein
37、ghitbyablade,increasingthelikelihoodofbackdiffusionofthegas.Pumpperformancedependsonbladedesignaswellasrotorspeed.Variablesincludethepitchangle,bladewidthandthedistancebetweenblades.Overallperformanceisoptimizedbyvaryingthebladegeometrythroughthepump.Ingestion（摄取）offoreignobjectsintoanyturbomolecula
38、rpumpduringoperationwillcauseseveredamagetotherotorandstatorblade.Inordertoreducethisriskmostpumpsareprovidedwithawiremeshinletguard.05/10/2004Title35Pumping selectivityPumping speed depends on the types of gas(molecular weight,momentum transfer)for the operation principle05/10/2004Title36ADVANTAGES
39、 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 sizeDISADVANTAGES 1.Sensitive to particulates 2.Requires mechanical pump 3.High rpm(Noise/Vibration)4.Low speed for hydrogen and helium 5.High maintenance cost 6.1 10-3
40、 Torr upper limits 7.High initial costAdvantagesanddisadvantagesoftheturbomolecularpump05/10/2004Title37Vapor pump:ejector pump and diffusion pumpDistinction：mean free path at the intake port vs.throat widthIn relation to 关于 涉及boilerMercuryChimneyDeflect 偏转Umbrella 伞形钟罩Pressure gradientviscous drag
41、and turbulent mixingDiminish,cross-sectionOrifice 孔 vapor booster pump:combination the diffusion and ejector pump05/10/2004Title381 Nozzle(Laval)2 Diffuser nozzle(Venturi)3 Mixing chamber4 Connection to the vacuum chamber1 Steam inlet2 Jet nozzle3 Diffuser4 Mixing region5 Connection to thevacuum chamber