中英文文献翻译螺杆式压缩机.docx

中英文文献翻译螺杆式压缩机.docx

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中英文文献翻译螺杆式压缩机

英文原文

ScrewCompressors

Thedirectionnormaltothehelicoids,canbeusedtocalculatethecoordinatesoftherotorhelicoidsandfromxandytowhichtheclearanceisaddedas:

，，（2.19）

wherethedenominatorDisgivenas：

（2.20）

andservetocalculatenewrotorendplanecoordinates,x0nandy0n,withtheclearancesobtainedforanglesθ=/pandτrespectively.Theseandnowservetocalculatethetransverseclearanceδ0asthedifferencebetweenthem,aswellastheoriginalrotorcoordinatesand.

Ifbyanymeans,therotorschangetheirrelativeposition,theclearancedistributionatoneendoftherotorsmaybereducedtozeroontheflatsideoftherotorlobes.Insuchacase,rotorcontactwillbeprohibitivelylongontheflatsideoftheprofile,wherethedominantrelativerotormotionissliding,asshowninFig.2.29.Thisindicatesthatrotorseizurewillalmostcertainlyoccurinthatregioniftherotorscomeintocontactwitheachother.

Fig.2.29.Clearancedistributionbetweentherotors:

atsuction,midrotors,anddischargewithpossiblerotorcontactatthedischarge

Fig.2.30.Variableclearancedistributionappliedtotherotors

Itfollowsthattheclearancedistributionshouldbenon-uniformtoavoidhardrotorcontactinrotorareaswhereslidingmotionbetweentherotorsisdominant.

InFig.2.30,areducedclearanceof65μmispresented,whichisnowappliedinrotorregionsclosetotherotorpitchcircles,whileinotherregionsitiskeptat85μm,aswasdonebyEdstroem,1992.AscanbeseeninFig.2.31,thesituationregardingrotorcontactisnowquitedifferent.Thisismaintainedalongtherotorcontactbeltclosetotherotorpitchcirclesandfullyavoidedatotherlocations.Itfollowsthatifcontactoccurred,itwouldbeofarollingcharacterratherthanacombinationofrollingandslidingorevenpuresliding.Suchcontactwillnotgenerateexcessiveheatandcouldthereforebemaintainedforalongerperiodwithoutdamagingtherotorsuntilcontactceasesorthecompressorisstopped.

2.6ToolsforRotorManufacture

Thissectiondescribesthegenerationofformedtoolsforscrewcompressorhobbing,millingandgrindingbasedontheenvelopegearingprocedure.

2.6.1HobbingTools

Ascrewcompressorrotoranditsformedhobbingtoolareequivalenttoapairofmeshingcrossedhelicalgearswithnonparallelandnonintersectingaxes.TheirgeneralmeshingconditionisgiveninAppendixA.Apartfromthegashesformingthecutterfaces,thehobissimplyahelicalgearinwhich.

Fig.2.31.Clearancedistributionbetweentherotors:

atsuction,midofrotoranddischargewithapossiblerotorcontactatthedischarge

Eachreferredtoasathread,Colburne,1987.Owingtotheiraxesnotbeingparallel,thereisonlypointcontactbetweenthemwhereasthereislinecontactbetweenthescrewmachinerotors.TheneedtosatisfythemeshingequationgiveninAppendixA,leadstotherotor–hobmeshingrequirementforthegivenrotortransversecoordinatepointsandandtheirfirstderivative.Thehobtransversecoordinatepointsandcanthenbecalculated.ThesearesufficienttoobtainthecoordinateTheaxialcoordinate,calculateddirectly,andarehobaxialplanecoordinateswhichdefinethehobgeometry.

Thetransversecoordinatesofthescrewmachinerotors,describedintheprevioussection,areusedasanexampleheretoproducehobcoordinates.herotorunitleadsare48.754mmforthemainand−58.504mmfortheaterotor.Singlelobehobsaregeneratedforunitleads:

6.291mmforthemainrotorand−6.291mmforthegaterotor.Thecorrespondinghobhelixanglesψare85◦and95◦.Thesamerotor-to-hobcentredistanceC=110mmandtheshaftangleΣ=50◦aregivenforbothrotors.Figure2.32containsaviewtothehob.

Reversecalculationofthehob–screwrotortransformation,alsogiveninAppendixApermitsthedeterminationofthetransverserotorprofilecoordinateswhichwillbeobtainedasaresultofthemanufacturingprocess.Theseaybecomparedwiththoseoriginallyspecifiedtodeterminetheeffectof

Fig.2.32.Rotormanufacturing:

hobbingtoolleft,rightmillingtool

manufacturingerrorssuchasimperfecttoolsettingortoolandrotordeformationuponthefinalrotorprofile.

Forthepurposeofreversetransformation,thehoblongitudinalplanecoordinatesandandshouldbegiven.Theaxialcoordinateisusedtocalculate,whichisthenusedtocalculatethehobtransversecoordinates:

，（2.21）

Thesearethenusedasthegivencoordinatestoproduceameshingcriterionandthetransverseplanecoordinatesofthe“manufactured”rotors.

AcomparisonbetweentheoriginalrotorsandthemanufacturedrotorsisgiveninFig.2.33withthedifferencebetweenthemscaled100times.Twotypesoferrorareconsidered.Theleftgaterotor,isproducedwith30umoffsetinthecentredistancebe