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ID:34519895
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页数:29页
时间:2019-03-07
《A.C.Hoffmann-4Cyclone Flow Pattern and Pressure Drop.pdf》由会员上传分享,免费在线阅读,更多相关内容在学术论文-天天文库。
1、4CycloneFlowPatternandPressureDropPredictingtheseparationefficiencyofcyclonesinvolvespredictinghowparti-clesbehaveintheseparationspace.Inordertodothis,weneedtoknowthevelocitydistributionofthegas.Someresearchershavemadeall-embracingmodelsforbothgasflowpatternandseparationefficien
2、cy;othershavecon-centratedononeortheother.Welookatthetwoissuesseparatelyhere.Modelsforcyclonepressuredropsometimesspringfrommodelsfortheflowpatternandarebasedonanestimationoftheactualdissipativelossesinthecyclone;othersarepurelyempirical.Inthischapterwediscussmodelsfortheflow
3、patternandpressuredrop,andinthesubsequenttwochapters,modelsfortheseparationefficiency.Weshallnotlookatallofthemodelshere;aninitialdiscussionwillleadtoatreatmentofafewofthemostpopularones.Withsomeregrettheauthorshavetoacceptthatitisnotpossibletogiveafullaccountofthederivations
4、ofthemodelequations.Thischaptercanonlyindicatetheprinciplesbehindthederivations.Itisourintent,however,topresentenoughofthetheoryandderivationstoallowthepracticingdesignandplantengineertoappreciatethe‘theory’underlyingcycloneperformance.Itisalsoourhopethattheuserofthisbookwi
5、llbeabletotakewhatispresentedhereinandapplyittowardsthedesign,evaluationandtroubleshootingofcommercialcycloneinstallations.Thereaderwishingtostudythedetailsofthederivationsisreferredtotheoriginalpapers.Attheendofthechapterwewilllookathowwellthemodelassumptionsfitwiththerealfl
6、owincyclones.WorkedexamplesforcalculatingcyclonepressuredropcanbefoundinAppendix4.A.4.1DiscussionInthissectionwewillconsidersomespecialfeaturesoftheflowandthepressuredropthatareduetotheswirlingmotioninthecyclone.Swirlingflowcanbeawkwardtoconsiderintuitively.Nevertheless,wetry
7、tolookatsomeoftheflowfeaturesonanintuitivebasishere.604CycloneFlowPatternandPressureDrop4.1.1FlowPatternThestandardwayofarrivingatflowequationsinTransportPhenomenaistobalanceforcesondifferentialelements.Thisistrickyinswirlingflowsincylindricalcoordinatesystems.Thesafestmethodof
8、derivingflowequationsinsuchsystemsistostartwiththeNavier-Stokesequationsandsimplify
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