已阅读5页,还剩15页未读, 继续免费阅读
版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
EXPERIMENTALANDNUMERICALANALYSISOFLADLETEEMINGPROCESSGastnM.MazzaferroA,1,MarceloPivaB,2,SergioP.FerroA,3,PabloBissioB,4,MarinaIglesiasB,AdrianaCalvoB,5,MarcelaB.GoldschmitA,6.ACenterforIndustrialResearch,FUDETEC.Dr.Simini250,2804Campana,ARGENTINA.BPorousMediaGroup,EngineeringSchool,UniversidaddeBuenosAires,PaseoColn850,1063,BuenosAires,ARGENTINA.1E-mail:2E-mail:mpivafi.uba.ar3E-mail:4E-mail:.ar5E-mail:acalvofi.uba.ar6E-mail:ABSTRACTInthecontinuouscasting,themoltensteelispouredfromtheladletothetundishthroughanozzlelocatedatthebottomoftheladle.Thisprocess,however,mustbestoppedbeforetheladleiscompletelyemptiedtoavoidslagcarryovertothetundish.Theamountofsteelthatremainsunteemedintheladleisusuallysignificantsosteelplantsarehighlyinterestedinstudyingdifferentwaystoimprovetheprocess.Inthepresentwork,experimentalstudiesonwatermodelsandnumericalsimulationsareusedtoanalyzetheconditionsneededforvortexformationandtheinfluenceofgeometricalandflowparametersintheamountofwastedsteel.Bothexperimentalandnumericalresultsleadtotheconclusionthatnovortexformationisexpectedtotakeplaceduringladledrainageunderindustrialconditions.1.INTRODUCTIONDuringthecontinuouscastingprocess,moltensteelispouredfromladletotundishthroughanozzlelocatedinaneccentricpositionofladlefloor.Aladleisavesselofgenerallycylindricalshapewithadiameterof2-3metersandaheightofapproximately3meters.Itcontainsbetween100and200tonsofliquidsteelwhicharedrainedthrougha5/10cmdiameternozzle.Moltensteelinladleiscoveredbyaslaglayer(whichthicknessvariesbetween5and20cm)whichpreventsitsoxidationbyaircontact.Asthedrainingprocessprogresses,theinterfacethatseparatesthesteelfromtheslag,eventuallydeflectstowardsthedrainagenozzleandadoptstheformofa“funnel”.Funnelformationleadstoslagcarryoverfromladletotundish.Thedrainageisstoppedwhenfirsttracesofslagaredetectedinthenozzle,leavingasignificantamountofsteel(upto3tons)unteemedintheladle.Funnelformationeffecthasbeenanalyzedbyseveralstudies1-7,generallybasedonexperimentsperformedonphysicalmodelswherewaterisusedinsteadofsteel.Intheseexperimentswaterdrainagefromcylindricalorsquareshapedvesselswithflathorizontalfloorsisstudiedfordifferentnozzlediameters(0.54cmto8cm)andeccentricities(upto0.7).Thesubjacentfluiddynamicsofthephenomenonhasalsobeenanalyzedbyseveralauthors8-14.Accordingtobibliography1-8twodifferentmechanismscanleadtothedeflectionofthesteelsurface:vortexsinkordrainsink.Vortexsinkischaracterizedbyhightangentialvelocitiesintheneighborhoodofthenozzle(seeleftschemeonFigures1and2)andcanbedevelopedevenwithahighcolumnofsteelintheladle.Vortexformationcantakeplaceinvesselswherethefluidhasimportantinitialtangentialvelocitiesespeciallyifthedischargenozzleiscentered.Theamountofliquidinladlewhenvortexsinkreachesthenozzledependsoninitialrotationalvelocityandonnozzleeccentricity.Ontheotherhand,thedrainsinkischaracterizedbyradialflow(rightschemeonFigures1and2)anddevelopsinthelaststageoftheteemingprocess,whenlessliquidsteelisleftintheladle.Drainsinkisalwayspresentattheendoftheprocessanddoesnotdependonthepreviousformationofavortexsink.Theheightoftheliquidcolumnleftunteemedinladlewhendrainsinkirruptsinthenozzle,isapproximatelyequaltothediameterofthenozzle.Drainsinkirruptioninthenozzle,unlikevortexsinkirruption,leadstosignificantproportionofslagcarryover1,4,6.Takingintoaccounttheseconsiderationsfoundinliterature,itseemsthatduetonozzleeccentricityandtheabsenceofpreferredrotationsense,vortexsinkisnotexpectedtotakeplaceundergeneralplantconditions.Theamountofsteelusuallydowngradedinplantsduetoslagcarryoverisconsistentwiththishypothesis.InthisworkwefirstpresentwatermodelexperimentsSection2carriedouttoconfirmthelastassumptionbyestimatingtheprobabilityofvortexformationinactualcastingpractice.InSection3wepresentnumericalsimulationsofindustrialladledrainageprocess,withfocusondrainsinkformationandpossibleinfluenceofladlefloorgeometry.AnanalysisofexperimentalandnumericalresultsispresentedinSection4andconclusionsarepresentedinSection5.2.WATERMODELEXPERIMENTSWatermodelexperimentswerecarriedoutbythePorousMediaGroup,attheEngineeringSchoolofBuenosAiresUniversity.TheexperimentalsetupusedtoanalyzetheflowofwaterduringthedrainingprocessispresentedinFigure3.AcylindricalcontainerofdiameterD=20cmispartiallyfilledwithwateruptoaconstantheightH0,throughtwotangentialpipeslocatedatoppositesidesofthecontainerbottomandat1cmofthewall.Thiswayoffillingprovidesthefluidthetangentialvelocitynecessarytoinducevortexformation.Waterisdrainedthroughanozzleofdiameterdn=0.5cmandlengthhn=10cmlocatedatthebottomofthevesselandatadistancerfromitscenter.Oncethefillingprocesshasconcludedthevelocityfielddecayswithtimeuntilthefluidremainsatrest.So,wecanselecttheinitialvelocityfieldbythewaitingtime,ti,betweentheendofthefillingandthebeginningofthedrainage.AssumingthattheflowfieldisessentiallytangentialandaxisymmetricwecharacterizetheinitialflowconditionthroughV,definedasthemaximuminitialtangentialvelocitymeasuredatthefreesurface.Oncethenozzleisopenthemassofwaterleavingtheladle,m,iscollectedinasecondvesselwhereitsweightismonitoredasafunctionoftimewithaprecisionbalance.Inthiswaytheflowrateatthenozzleoutput,Q=dm/dt,canbeobtained.ThecriticalheightHc,definedasthelevelofwaterintheladlewhenairirruptioninthenozzletakesplace,wasanalyzedasfunctionofthenozzleeccentricity=2r/D,andinitialtangentialvelocity,V.InFigure4aanexampleshowingthetimeevolutionoftheflowrateQthroughthenozzleispresented.ThefigurecorrespondstothedrainageofaH0=11cmwatercolumnthroughacenterednozzle(=0)andlargeinitialtangentialvelocity,V2.5cm/s.Itcanbeseenthattheinitialflowrate,Qi32g/s,smoothlydecreaseswithtimeuntilt=28s.Inthisperiodthefreesurfaceofthefluidremainsalmostflatexceptinthevicinityofthenozzleaxiswheretheformationofasmallfreesurfacedepression(ordimple)wasobservedafterfewseconds.ThetheoreticalflowratecalculatedfromBernoullilawwasfoundtofitquitewelltheexperimentaldataindicatingtheinviscidnatureofthedrainageprocessinthisstage.Theabruptdropintheflowrateattc28sindicatesthebeginningofthevortexsink.ThecriticalheightisHc=8.6cmwhilethedrainedpercentageisabout22%.Simultaneouslythefreesurfacedimpleevolvesdownwardtoformalongvortexfunnelwhichgoesthroughtheoutputproducingtheirruptionofairinthenozzle.Afterthiscriticaleventtheflowratemeanvaluedecreasessmoothlywithfluctuationsduetothepresenceofairinthenozzle.Inthefinalpartofthedrainage,t190s,itisobservedthatthefunneldisappears:theremainingcirculationisnotenoughtosustainthevortexsinkandthefreesurfaceofthefluidbecomesflat.ThisphenomenonoccursatHdn.Thenozzleisagainfilledwithwaterandtheflowrateincreasessuddenlyduringafewsecondsproducingasignificantdrainage.Then,thedrainsinkoccursatt=198s.InFigure4banewexampleisconsideredwithidenticalconditionsasthepreviouscasebutwithamuchlowerinitialtangentialvelocity(muchlongerwaitingtime).Inthiscasetheinitialcirculationisnotlargeenoughtoproduceavortex,theladledrainswiththefreesurfacealmostflatuntilt=109swhenthedrainsinkoccurs.Thedrainedpercentageisabout85%.ToanalyzetheinfluenceofnozzleeccentricityweperformedexperimentsinsimilarconditionsasinFigure4a(H0=11cmandlargeinitialtangentialvelocity)butwithtwodifferentvaluesofthenozzleeccentricity:=0.5and=0.9.InFigure4ctheresultsfor=0.5areshown,itcanbeseenthatavortexdevelopsatt=96s.ThecriticalheightisHc=1.6cmandthedrainedpercentageis86%.For=0.9theflowrateevolutionissimilarasthatshowninFigure4cthatis,novortexisobservedinspiteoftheconsiderableamountofinitialcirculation.Again,thedrainsinkoccursattheendofthedrainagewhenHdn.AcompletesetofresultsarepresentedinFigure5wherethecriticalheightHcisplottedasafunctionoftheinitialtangentialvelocityVfor=0(circles),=0.5(downtriangles)and=0.9(squares).Inagreementwithpreviousstudies1-8wefoundthattherollplayedbynozzleeccentricityistodelaythevortexformationandeventoinhibititforthelargestvalueof.Thus,forthelargesteccentricity(=0.9)novortexwasobservedinanyoftheconsideredvaluesofV.Amoredetailedanalysisoftheseexperimentscanbefoundelsewhere15.InordertorelatetheresultsjustshownwithatypicalfullscalemoltensteeldrainageonecanusethedimensionalanalysisproposedbyGuthrieetal8.TheyconcludethatthedimensionlesscriticalheightHc/H0dependsonlyontwohydrodynamicsparameters:aReynoldsnumberdefinedasRe=VoutH0/(
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 2024年02月江苏省张家港市2024年公开招考76名事业单位工作人员笔试参考题库后附答案详解
- 2024年02月山西省文化和旅游厅所属事业单位2024年公开招考3名工作人员笔试参考题库后附答案详解
- 2024年02月云南省玉溪市事业单位2024年公开招聘919名工作人员5笔试参考题库后附答案详解
- 2022年执业药师考试《中药学综合知识与技能》高频考点1
- 2024年3月福建厦门医学院附属口腔医院辅助岗位人员招考聘用笔试参考题库附带答案详解
- 2024年3月广东石油化工学院人才引进100人笔试参考题库附带答案详解
- 2024年04月福建省龙岩仲裁委员会2024年公开招考2名聘用制工作人员笔试参考题库附带答案详解
- 2024年03月贵州黔西南州国防动员办公室2024年公开考聘1名事业人员工作笔试参考题库附带答案详解
- 2024年4月江苏苏州太仓市教育局招考聘用备案制教师40人笔试参考题库附带答案详解
- 立体定向脑电图临床应用考核试题及答案
- 起重机械监督检验规程
- 钉钉设置任务培训课件
- 2024年湖北省知名中小学教联体联盟中考第一次模拟考试语文试题
- 2024年广东省星海音乐厅招聘招聘历年高频考题难、易错点模拟试题(共500题)附带答案详解
- 产科院感知识培训课件
- 授权委托书:签订影视制作合同
- 人教版四年级数学下册第三单元运算定律 大单元作业设计
- 住培中医病例讨论-面瘫
- 管理体系审核的内外部审核
- 掼蛋比赛规则及方案主持
- 洗衣店转让协议书模板
评论
0/150
提交评论