A new flow controller for medical injectionWord文档格式.docx
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A new flow controller for medical injectionWord文档格式.docx
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,
a
aDepartmentofMechanicalEngineering,KoreanAdvancedInstituteofScienceandTechnology,373-1,Guseong-dong,Yuseong-gu,Daejeon305-701,SouthKorea
bMeinntech,1113-1Daran-dong,Dongan-gu,Anyang,Gyeonggi-do431-811,SouthKorea
cSchoolofMechanicalEngineering,PusanNationalUniversity,San30,Changjeon-dong,Kumjeong-ku,Pusan609-735,SouthKorea
Received4July2003;
Revised9April2004;
accepted23April2004.
Availableonline17June2004.
Abstract
Anewtypeofflowcontrollerformedicalinjectionwasdevelopedandevaluated.Theflowratewascontrolledbysimultaneouslyvaryingthefrictionlengthanddepthofthemicro-channelsuchthattherelationbetweentheflowrateandthelengthofthechannelbecomesmorelinear.Themicro-channelwasfabricatedusingultra-precisionmachiningtechnology.Asealmadeofbutylrubber
wasusedtostopfluidleakage.The
butylrubber
wascoatedwithsiliconeoiltomakethecontrollerrotatesmoothly.Theflowcontrollerwasvalidatedbycomparingexperimentaldatawiththeoreticalpredictions.Goodagreementwasfoundbetweentheoryandexperiment.
AuthorKeywords:
Flowcontroller;
Frictionlength;
Medicalinjection;
Butylrubber
ArticleOutline
1.Introduction
2.Designconceptandfabrication
3.Resultsanddiscussion
4.Conclusions
References
1.Introduction
Variousapplicationsrequireknowledgeoftheflowvolumepassingthroughaduct.Forexample,theabilitytoaccuratelymeasuretheflowvolumepassingthroughaninjectorisofvitalimportancewheninjectingaveinwithagivenamountofmedicine.AninjectionofRinger'
ssolutioniswidelyusedinhospitals,wheretheflowrateiscontrolledbytrappingtheflowbyaslidingroller.However,thismethoddoesnotallowprecisecontrolofflowratebecauseofmanualtrapping.
Inthepresentstudywedevelopanewtypeofflowcontrollercapableofaccurateflowcontrol.Insteadoftheslideroller,mostcontrollersusedinhospitalstodate,haveemployedthefrictionlengthalongalongductforflowcontrol.However,becausetheflowrateisinverselyproportionaltothefrictionlength,theflowrateofflowscontrolledexclusivelybythefrictionlengthwillbehighlysensitivetothefrictionlengthinthelowflowrateregionandinsensitivetothefrictionlengthinthehighflowrateregion.Thisproblemisresolvedinthepresentstudybyvaryingthedepthoftheductsuchthattherelationbetweentheflowrateandthelengthoftheductbecomesapproximatelylinear.Thisdesignenablesaccurateflowcontrol.Theproposedcontrollerwasvalidatedbycomparingexperimentaldatawiththeoreticalpredictions.Themicro-ductwasfabricatedusingultra-precisionmachiningtechnology.Sealsmadeof
butyl
rubberwereusedtostopfluidleakage;
the
rubberwascoatedwithsiliconeoiltomakethecontrollerrotatesmoothlywhenoperatedbyhand.Theflowrateiscontrolledinarange5
Q
250ml/h.Thetargetprecisionlevelofthenewflowcontrolleristhattherelativeerrorislessthan10%intheregion50
100ml/h,whichiswidelyusedinhospitals.Theapproachsuggestedherehastheadvantagethatitdoesnotinfringeuponpreviouslypublishedpatents.
2.Designconceptandfabrication
First,letusconsiderthecaseoffullydevelopedflowinacircularpipeoflengthLanddiameterDthathasapressuredropΔpoveritslengthL.Theflowratethroughthepipecanbeexpressedas
(1)
whereμisthefluidviscosity[1].AsseeninEq.
(1),theflowratecanbecontrolledbyadjustingtwomainparameters,LandD.However,QismuchmoresensitivetoD(Q
D4)thantoL(Q
1/L).MostflowcontrollersincurrentusecontroltheflowratebychangingthefrictionlengthL,thatis,theyemploytherelationQ
1/L.Inthepresentstudy,however,bothDandLaresimultaneouslyadjustedtocontroltheflowratesuchthattherelationemployedisclosedtotheformQ
L.
AschematicdiagramoftheflowcontrolisshowninFig.1.Anarrowflowchannelwithasquarecross-sectioniscutintothecircularplateB.Thechannelrunsfrombtodandpassesthroughc.ThefrictionlengthLofthechannelisdenotedbyL=Rθ,whereRisaradiusofthearcofthechannelandθisarotationangleasshowninFig.2.Thewidthofthechannelwisfixed,butthechanneldepthchangesfroma1toa2alongthefrictionlengthL.ByplacingplateAuponplateB,aclosedflowchannelismade.AsshowninFig.2,thefrictionlengthisthedistancealongthearcfromctod.Here,theinletpointcisadjustedbyrotatingplateBwithrespecttoplateA.Thespanofcisb
c
d.Theoutletpointd
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