燃煤鍋爐的燃燒進(jìn)程控制-畢業(yè)設(shè)計(jì)外文翻譯

1、1ControllingtheFurnaceProcessinCoalFiredBoilersTheunstabletrendsthatexistinthemarketoffuelsuppliedtothermalpowerplantsthesituationsinwhichtheparametersoftheiroperationneedtobechanged(preserved)aswellasthetendencytowardth

2、eeconomicalenvironmentalrequirementsplacedonthembecomingmestringentarefactsthatmaketheproblemofcontrollingthecombustionheattransferprocessesinfurnacedevicesveryurgent.Thesolutiontothisproblemhastwoaspects.Thefirstinvolve

3、sdevelopmentofacombustiontechnologyaccdinglythedesignofafurnacedevicewhennewinstallationsaredesigned.Thesecondinvolvesmodernizationofalreadyexistingequipment.Inbothcasesthetechnicalsolutionsbeingadoptedmustbeproperlysubs

4、tantiatedwiththeuseofbothexperimentalcalculationstudies.TheexperienceCentralBoilerTurbineInstituteResearchProductionAssociation(TsKTI)ZiOspecialistsgainedfromoperationofboilersexperimentalinvestigationstheycarriedoutonmo

5、delsallowedthemtoproposeseveralnewdesignsofmultifuelmaneuverable—inotherwdscontrollable—furnacedevicesthathadbeenputinoperationatpowerstationsfseveralyears.Alongwiththisanapproximatezeroonedimensionalzonewisecalculationm

6、odelofthefurnaceprocessinboilershadbeendevelopedattheTsKTIwhichallowedTsKTIspecialiststocarryoutengineeringcalculationsofthemainparametersofthisprocesscalculatestudiesoffurnacesemployingdifferenttechnologiesoffiringcombu

7、stionmodes.Naturallyfurnaceprocessadjustmentmethodslikechangingtheairexcessfactstackgasrecirculationfractiondistributionoffuelairamongthetiersofburnersaswellasotheroperationswrittenintheboileroperationaltareusedduringboi

8、leroperation.Howevertheeffecttheyhaveontheprocessislimitedinnature.Ontheotherhcontrolofthefurnaceprocessinaboilerimpliesthepossibilityofmakingsubstantialchangesintheconditionsunderwhichthecombustionheattransferproceedind

9、ertoconsiderablyexptherangeofloadsminimizeheatlossesreducetheextenttowhichthefurnaceiscontaminatedwithslagdecreasetheemissionsofharmfulsubstancesshifttoanotherfuel.Suchacontrolcanbeobtainedbymakinguseofthefollowingthreem

10、ainfacts:3estimatinghowefficientthemixingismaytoacertaindegreebeusedinanalyzingthefurnaceasamixingapparatus.Obviouslythegreaterthejetlength(itsmomentum)thelongerthetimeduringwhichthevelocitygradientitcreatesinthefurnacew

11、illpersistthereaparameterthatdetermineshowcompletelytheflowsaremixedinit.Notethatthehigherthedegreetowhichajetisturbulizedattheoutletfromanozzleburnertheshterthedistancewhichitcoversaccdinglythelesscompletelythecomponent

12、saremixedinthefurnacevolume.Oncethroughburnershaveadvantagesoverswirlonesinthisrespect.Itiswasproposedthattheextenttowhichoncethroughjetsaremixedastheyperatewithvelocityw2densityρ2intoatransverse(drift)flowmovingwithvelo

13、cityw1havingdensityρ1becrelatedwiththerelativejetthrowdistanceinthefollowingwayWhereksisaproptionalityfactthatdependsonthe“pitch”betweenthejetaxes(ks=1.5–1.8).Theresultsofanexperimentalinvestigationinwhichthemixingofgasw

14、ithairinaburnertheninafurnacewasstudiedusingtheincompletenessofmixingasaparameterarereptedin5.Aroundoncethroughjetisintensivelymixedwiththesurroundingmediuminafurnacewithinitsinitialsectionwheretheflowvelocityatthejetaxi

15、sisstillequaltothevelocityw2atthenozzleificeofradiusr0.Thevelocityofthejetblownintothefurnacesveryrapidlybeyondtheconfinesoftheinitialsectiontheaxisithasinthecaseofwallmountedburnersbendstowardtheoutletfromthefurnace.One

16、mayconsiderthattherearethreetheeticalmodelsfanalyzingthemixingofjetswithflowrateG2thatenterintoastreamwithflowrateG1.Thefirstmodelisfthecasewhenjetsflowintoa“free”space(G1=0)thesecondmodelisfthecasewhenjetsflowintoatrans

17、verse(drift)currentwithflowrateG1G2，thethirdmodelisfthecase?whenjetsflowintoadriftstreamwithflowrateG1G2.Thesecondmodelrepresentsmixinginthechannelofagasburnerthethirdmodelrepresentsmixinginafurnacechamber.Weassumethatth

18、emixingpatternwehaveinafurnaceisclosertothefirstmodelthanitistothesecondonesince0G1G21wewillassumethatthethrowdistancehofthejetbeingdriftedisequaltothelengthS0ofthe“free”jet’sinitialsection.Theejectionabilityofthejetbein