高速泵结构比较文章图Word文件下载.docx

高速泵结构比较文章图Word文件下载.docx

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WuJian-bo

ChemicalMachineryResearchInstitute,HefeiUniversityofTechnology,Hefei,China,23009

gmriwjb2000@

HeYu-jie

Heyujie301@

LiQiang

hfliqiang@

ABSTRACT

Inordertostudytheeffectofthestructuralstyleofhigh-speedpumponinternalflow,4typeshigh-speedpumpofdifferentstructuralstyleareselectedforcomprehensiveanalysis，S-AturbulencemodelandSIMPLIECalgorithmareadoptedfornumericalsimulationofinternalflow.Bycomprehensivelycomparingthestaticpressure,totalpressure,sectionalvelocityvectorandflowpathline,twotypesofhigh-speedpumpswithcylindrical-bladeimpellermatchingnozzletypepumpcasinghaverelativelyidealpressurefieldandflowcondition,canreducehydraulicloss.Thecomprehensiveperformanceof4typesofhigh-speedpumpispredictedthroughcomputationalsimulation,thehigh-speedpumpwithopencylindrical-bladeimpellermatchingnozzletypepumpcasinghasmostexcellentperformance,indicatingthestructuralstyleofhigh-speedpumphaseffectonitsinternalflowandperformance.

Keywords:

high-speedpump,structuralstyle,numericalsimulation,flowanalysis,performance.

NOMENCLATURE

Impellerdiameter，m

Impellerwidthatoutlet，m

Numberoflong/shortblades

Basiccircleofvolutecasing，m

Throatdiameterofdiffuser，m

Lengthofdiffusionsectionofdiffuser，m

Diffusionangle，0C；

Totalpressure

Staticpressure

Absolutespeed

Totalpressureatimpellerinlet

Totalpressureatoutletofpumpcasing

SumofmomentsaboutZ-axis

INTRODUCTION

High-speedpartialemissionpumpistheonewithspecialconstructionandloworultra-lowspecificspeed（<

50[1]）,ithasthefeaturesofsmallflow,highhead,highspeed,simpleconstruction,highreliability,convenientmanufactureandrepair,etc.[2],itiswidelyappliedinthefieldofaviation,sprayirrigation,firefighting,petrochemicalengineeringetc.Themediumentersthesuctionchamberofthepumpandisdischargedafterpassingthroughopenimpeller,annularvolutecasingandnozzletypediffuser,theinternalflowofthepumpisverycomplexandbelongstounsteadyflow[3].Internalflowdiffersfordifferentstructuralstyleofhigh-speedpumpandthehydraulicperformancedifferssomewhat;

inliterature[4~6]onlysingle-itemnumericalsimulationiscarriedoutonimpeller,internalflowpassageandvolute,thuscannottrulyreflectstheoverallflowconditionofhigh-speedpump,whereasliterature[7]conductedfully3Dunsteadycomputationalsimulationontheentireconstant-speedcentrifugalpump,inthispaperfocusisplacedonanalysisandcomparisonofinternalflowcharacteristicsof4differentstructuresofhigh-speedpump,andinternalflowanalysisandnumericsimulationstudyarecarriedoutondifferentstructuresofhigh-speedpumpforthecommon4combinationsofimpellerandnozzlestylecasingwiththeturbulencemodelsofNavier-StokesandRealizableequationsfor3DturbulentflowusingFluentsoftware,wall-functionmethodandmeshtechniqueforslidingbetweenimpellerandpumpcasingandS-AturbulencemodelandimplicitcorrectionSIMPLIECalgorithmofsecond-ordercentraldifferencescheme.

STRUCTURALSTYLEOFIMPELLERANDNOZZLESTYLEPUMPCASING

4differentstructuralstylesareformedbymatching4typesofimpellerwithnozzlestylepumpcasing,amongthemtheassemblyofstraight-bladeimpellerandnozzlestylepumpcasinghasmoreapplicationinpractice.

Structuralstyleofimpeller

Thecommonstructuralstylesofimpeller[8-9]athomeandabroadareshownasinFig.1,thesefourtypesofimpellerhavethesamegeometricdimensions,seeTable1and2.

Table1:

Performanceparametersofhigh-speedpump

DescriptionValue

Flow（m3/h）15

Head（m）400

NPSH（m）3.5

Speed（r/min）8500

Power（kW）75

Table2:

hydraulicdimensionsofhigh-speedpump

Impellerdiameter（m）0.17

Impellerwidthatoutlet（m）0.012

Numberoflong/shortblades8/8

Basiccircleofvolutecasing（m）0.186

Throatdiameterofdiffuser（m）0.0095

Lengthofdiffusionsectionofdiffuser（m）0.067

Diffusionangle（0C）8

（a）Semi-openstraight-bladecompositeimpeller

（b）Openstraight-bladeimpeller

（c）Opencylindrical-bladeimpeller

（d）Semi-opencylindrical-bladecompositeimpeller

Figure1.Structuraldiagramofimpeller

Structuralstyleofpumpcasing

Thepumpcasingiscomposedofannularvoluteandnozzlestylediffuser,asshowninFig.2.

Figure2.Structuraldiagramofpumpcasing

NUMERICCOMPUTATION

Griddivision

Pro/Eisappliedtobuild3Dhydraulicmodeldiagramofpump,andinordertoobtainbettercomputationalresults,alengthofleadingpipewhoselengthis3timesofpipediameterisaddedatimpellerinletandoutletofvolutecasing.Thehydraulicdimensionsofhigh-speedpumparegenerallyrelativelysmall,andthegapbetweenimpellerandpumpchamberisverysmall,inordertoobtainbettercomputationalresults,thelocationsofsmalldimensionsarelocallyencryptedingriddivision,thesizeofgriddivisionshouldnotbetoobig.ANSYS-Fluentpre-processingsoftwareGambitisusedforgriddivision,andnon-structuredhybridgridTGirdisadoptedtodividetheentiremodel,thisgridismainlycomposedoftetrahedrons,andhexahedrons,conesandwedgesatlocallocations,itcanwellprocessgriddivisionofcomplexmodel;

themax.divisionsizeofimpellerandannularvoluteis1,thenumberofdivisionelementsofimpelleris1307994andthatofannularvoluteis380929.

Selectionofturbulencemodel

Dr.Basquepointedoutthattheflowpatternvariessignificantlyonthewallareaofhigh-speedpartialemissionpump,theflowintheflowpassageofimpellercanalmostbedeemedtobeastateofrigidmotionwithimpeller,therotatingflowinannularvolutealsodoesnothavemotionrelativetoimpeller,therefore,thestressofturbulentflowactshardly;

modeloflowReynoldsnumberisselectedintheanalysisofhigh-speedpump.

InANSYS-Fluent,theSpalart-AllmarasmodelisproventobeveryeffectiveforbuildinglowRe-numbermodel,especiallyithasshownveryeffectforwallrestrainingflow,andhasmoreextensiveapplicationinrotarymachinery;

byreferencetoselectionofturbulencemodelfornumericanalysisofpartialemissionpumpwithspecificspeedintherangeof50~130,thismodelisselectedastheturbulencemodelfornumericsimulationofhigh-speedpumpwithlowspecificspeed.

Settingofboundaryconditions

Theinletboundaryconditionissettobeaninletofuniformandcontinuousvelocitywithoutrotation,andtheoutletissettobetheoneoffreeoutflow;

thefrontandrearcover,wallofannularvolute,wallofwaterpilotingsectionatinletandoutletandwaterbodyaresettobestationary;

theimpellerwallandwaterbodyofimpelleraresettoberotarywiththerotaryspeedof8500rpm,MRFmodelisselectedandimpellerwall,frontandrearshroudandwallofvolutehousingareallsettobesliplessadiabaticwall[6].

ANALYSISOFSIMULATIONRESULTS

Analysisofpressurefield

TaketheaxialmiddlesectionofannularvolutetocalculatethestaticpressureinsidetheannularvoluteandimpelleranduseANSYS-CFD-Postprogramtoanalyzethecomputationalresults.

Nomenclature

Typeahigh-speedpumpofcombinedconstructionofsemi-openstraight-bladecompositeimpellerandnozzlestylepumpcasing.

Typebhigh-speedpumpofcombinedconstructionofopenstraight-bladecompositeimpellerandnozzlestylepumpcasing.

Typechigh-speedpumpofcombinedconstructionofopencylindrical-bladecompositeimpellerandnozzlestylepumpcasing.

Typedhigh-speedpumpofcombinedconstructionofsemi-opencylindrical-bladecompositeimpellerandnozzlestylepumpcasing.

（a）High-speedpumpoftypea

（b）High-speedpumpoftypeb

（c）High-speedpumpoftypec

（d）High-speedpumpoftyped

Figure3．Staticpressurediagramsofthefourtypesofhigh-speedpump

Cavitationtendstotakeplaceattheinletsofthefourtypesofhigh-speedpump,thepressurepresentsatendencyofannularoutwardincrement,yetthepressuregraduallyincreasesfrominlettooutletandfromhubtorim,indicatingtheworkdonebybladeprofileincreasesradially.Takethetangentialpositionofnozzletoexcircleofannularvoluteas0°

position,intheareawhichissweptacrossthenozzletovoluteshroudbytheimpellerfrom0°

positioninthedirectionofimpellerrotation,thepressureinimpellerandannularflowpassagehassomewhatdropcomparedtootherareasandthepressuregradientincreasesslowly;

intheareafrom0°

to90°

largernegativepressureareaappearsatimpellerinletandbladeinlet,whichextremelytendstocausecavitation.

Intheannularflowpassageofannularvolute,thestaticpressuredistributionisratheruniformintherangefrom90°

to360°

intherotationaldirectionofimpeller;

especiallyinfrontofinletofstraightpipesection,thestaticpressuredropssignificantly;

intheareafromstraightpipesectiontodif