自动化专业本科毕业设计英文翻译.docx

自动化专业本科毕业设计英文翻译.docx

《自动化专业本科毕业设计英文翻译.docx》由会员分享，可在线阅读，更多相关《自动化专业本科毕业设计英文翻译.docx（17页珍藏版）》请在冰豆网上搜索。

自动化专业本科毕业设计英文翻译

自动化专业本科毕业设计英文翻译

学院（部）：

专业班级：

学生姓名：

指导教师：

2012年6月3日

THEPLC-BASEDBOILERCOMBUSTIONC

ONTROLSYSTEM

1Introduction

Combustioncontrolsystemisthemasterofthepowerplantboilersystem,whichincludingafuelcontrolsystem,airflowcontrolsystem,andfurnacepressurecontrolsystem.MostofthepowerplantboilercombustioncontrolsystemisstillusingPIDcontrol.Combustioncontrolsystembythemainsteampressurecontrolandtheburnratecontroltoformacascadecontrolsystem,inwhichthecombustionratecontroliscontrolledbytheamountoffuel,airvolumecontrol,citedairvolumecontrolconstitute.Eachsub-controlsystemisrespectively,andthroughthedifferentmeasurementcancontrolmethodstoensureeconomicburningcombustionandsafety.

2Thecontrolprogram

Boilerburningthebasictaskoftheautomaticcontrolsystemistomakefuelcombustion,sothatcanprovideheattoadapttotherequirementsoftheboileroutputsteamload.Butitmusttoensurethesafeandeconomicoperationoftheboiler.Aboilerfuel,airsupplyandbleedairvolumecontrolofthethreetasksarenotseparate.Thesethreecontrolvariablescanbecontrolledwiththreecontrollers,buteachothershouldbeco-coordinatedinordertoworkreliably.Tosetthewatertemperature,youneedtoadjusttheblastvolumeandtheproportionintheamountofcoaltotheboilerrunningatoptimumcombustionstate.Whenthefurnacememoryatacertainnegativepressure,itcanmaintaintheboilerthermalefficiencyandavoidtheoutwardflameofthefurnaceoverheatedinordertoensurethesafetyofpersonnelandenvironmentalhygiene.

2.1Thecontrolsystemintheoverallframeworkofdesign

Combustionprocessautomaticcontrolsystemtheprogramandthetypeofboilerequipment,operationandcontrolrequirements,itrelatedtothedifferentcircumstancesandrequirements.Unitpowerplantcombustionprocesscontrolledobjectseenasamultivariablesystems,designcontrolsystemandfullyconsiderthepracticalengineeringproblems.Bothofthemcanensurethatoperatingpersonnelnotonlyaccustomedtotheoperation,butalsotomaximizetheimplementationofthecombustionoptimization.TheoverallframeworkofthecontrolsystemisshowninFigure1.

Figure1unitpowerplantcombustionprocesscontrolschematic

Pistheunitloadheatsignal.Thecontrolsystemincludes:

slidingpressureoperationofthemainteampressuresettingvaluecalculationmodule（obtainedbythethermalsystemexperimentaldata,fittedcurveoftheavailableDCSpolylinefunctionblock）,theload-airsupplyfuzzycalculationmodule,andthemainsteampressurecontrolsystemandsentasquotedintheaircontrolsystem.ThemainsteampressurecontrolsystemusesconventionalcascadePIDcontrolstructure.

2.2Theamountoffuelcontrolsystem

Whenoutsidetherequirementsoftheboilersteamloadchanges,itmustbeappropriatetochangetheamountoffuelburnedbytheboiler.Thefuelcontrolisasystemboilercontrolthebasicandimportantpart.Italsoaffectsnotonlythemainsteampressuretotheamountofcoalsenttoleadtheairflowcontrol,alsoaffectsthesteamevaporationandsteamtemperatureandotherparametersinthedrumSotheamountoffuelcontrolhaveamajorimpactonboileroperation.FuelcontrolcanbeusedinFigure2.

Figure2theamountoffuelcontrolstrategy

Ofwhich:

NBtherequirementsfortheboilerload;Bistheamountoffuel;F（x）astheexecutingagency.

Oneofthepurposessettheamountoffuelcontrolsubsystemistouseittoeliminatethefuelsideoftheinternalspontaneousdisturbanceandimprovethequalityofregulation.Inaddition,duetothelargecapacityoftheunits,betweenthevariouspartscloselylinkedandinfluenceeachothercannotbeignored.Inparticular,changesinfueltype,andputintothefuelsupplydeviceandthenumberofdifferentfactorstothecontrolsystem.Thefuelcontrolsubsystemsettingalsoprovidesthemeanstoaddresstheseissues.

2.3Airvolumecontrolsystem

Inordertoachieveeconomiccombustion,whentheamountoffuelchanges,itmustbeappropriatetochangetheairflow,sothatchangetheairsupplyandtheamountoffuel.TherelationshipbetweentheamountoffuelandairsupplyareshowninFigure3.

Figure3theamountoffuelandairsupplyrelationship

Combustionprocessintheeconomywhetherornotismeasuredbythesurplusaircoefficient,excessaircoefficientisusuallyindirecteffectstheoxygencontentofthefluegas.Themostbasiceconomiccombustionairvolumeandtheamountoffuelmustbeinacertainproportion.

Airsupplycontrolsubsystemtaskistomaketheboilerairsupplyandfueltheamountofphasecoordination,theboilerthehighestthermalefficiencycanbeachieved,toensuretheuniteconomics,buttheboilerthermalefficiencycannotdirectmeasurements,andthereforeusuallythroughsomeindirectmethodstoachievepurpose.ShowninFigure4,measuredtheamountoffuelBastheairflowregulatorforagivenvalue,theairvolumeVandtheamountoffuelBintoacertainproportion.

Figure4theamountoffuelair-conditioningsystems

Inthesteadystate,thesystemcanguaranteetheamountoffuelandairsupplytomeet

Select

airvolumeisslightlylargerthanthetheoreticalairBcompletecombustionneeds.Theadvantageofthissystemissimple;itcanbeeliminatedfromtheloadsideandfuelsideofthevariousdisturbances.

2.4Citationofairvolumecontrolsystem

TheextentrequiredinordermaintainingthefurnacepressureofthewindandtheairsupplytoadaptFurnacepressurewillalsoinfluencethelevelofsecurityandeconomicoperationoftheboiler.Furnacepressureistoolowtomakealotofcoldairtoleakintothefurnacewillincreasetheloadandsmokedamageinduceddraftfan,thefurnacepressureistoolowandmayevencausetheimplosion;furnacepressurehigherthanatmosphericpressure,willTheflamesandsmoketoemerge,notonlyahealthhazard,andmayevenaffecttheequipmentandlifesafety.Leadthetaskoftheairvolumecontrolsubsystemistoensurethatthefurnacenegativepressure,andvacuumfurnacemustbecontrolledwithintheallowablerange,generally-20Pa.Meanstocontrolthefurnacepressureandadjusttheamountofinduceddraftfan,induceddraftfan,itsmainexternaldisturbanceistheairsupply.Asaregulatoroftheinertiaofthefurnaceflue,nomatter,includinginterferenceandoutsideinterferencearesimilartoaproportionalcomponent.Generallyuseasingleloopcontrollersystem,plusthemethodofthefeedforwardcontrolisshowninFigure5

Figure5citedtheairvolumecontrolsubsystem

Furnacepressureandthefigureforagivenvalue,SisthemeasuredfurnacepressureandQistheleadairvolume,Vistheairsupply.Furnacepressureandactuallydeterminethebalanceofairvolumeandtheamountofthewind,theairflowasafeedforwardsignaltoimprovetheregulationperformanceofthesystem.Inaddition,becausetheadjustmentobjectisequivalenttoaproportionalcomponent,wastheamountofreactionistoosensitive,inordertopreventminordeviationscausedbythefrequentactionoftheinduceddraftfanbaffle,youcansettheratiooftheregulatorwithauto-correctionlink,makingasmalldeviationincreaseregulatorproportionalband.Sismeasuresignalforthenegativepressure,andtheneedforlow-passfiltertosuppressthevolatilityofthemeasuredvalue,thesystemhardwareconfiguration.

Conventionalinstrumentsintheboilercombustionprocesscontrol,lag,intermittentadjustment,theoxygencontentinthefluegasexceedsagivenvalue,lowloadandlowfluegastemperature.AdoptsPLCtocontroltheboiler,duetoitsfastcomputingspeed,highprecision,accurateandreliable,canbeadaptedtothecomplexanddifficulttodealwiththecontrolsystem.Thus,youcansolveadifficultproblemtosolvetheabovecontrolbyconventionalinstruments.TheselectedPLCsystemrequiresastrongcompatibilitywithminimuminvestmentinthesystemtothecompletionandoperation.Secondly,whenthedesignautomationsystemtochangedoesnotrequirere-programming,inputandoutputsystemdoesnotrequire.Thewiringdoesnotneedtore-trainofpersonnel,wouldenablethePLCsystemupgrade.Finally,highersystemisperformance.ThehardwarestructureisshowninFigure6.

.

Figure6hardwarestructure

Accordingtotherequirementsofthesystem,selectSiemensPLCS7-200CPU226ascontrolcore,anditalsoextendsthetwoEM231AnalogInputModulesandaCP243-1Ethernetmodule.TheCPU226I/Opointis2416,sothatfullymeettherequirementsofthesystem.Atthesametime,thechoiceoftheEM231module,whichistheA/Dconvertermodulehasfouranaloginputs12A/D,itssamplingrateof25μs,temperaturesensors,pressuresensors,flowsensorsandoxygendetectionsensoroutputsignalconditioningandamplificationprocessingbecomethestandardsignalof0~5V,theEM231moduleautomaticallycompletetheA/Dconverter.

ThephysicalcharacteristicsoftheS7-200PPIinterfaceRS-485canworkinthePPI,MPI,andfreecommunicationportmode.ItprovidesavarietyofoptionsforcommunicationbetweenPCandPLC.

Fortherealizationoftheman-machinedialoguefunction,suchassystemstatusandvariablegraphics,parameterchanges,etc.,butalsoextendsaEview500seriesoftouchscreen,simple,convenientoperationcontrol,canbeusedtosetsystemparameters,displaytheboilertemperature.ThereisanEthernetmoduleCP243-1,whoseroleistoallowtheS7-200directlyconnectedtoEthernetviaEthernetlong-distanceexchangedatawithotherS7-200fordatatransmission,communicationbasedonTC