外文翻译--有限时间热力学优化活塞行动改进的发动机性能 英文版.pdf

Proc.Natl.Acad.Sci.USAVol.78,No.4,pp.19861988,April1981AppliedPhysicalSciencesFinteimthermodynamicsEgprfoacprovedbyoptimzedpistonmotinOtocyle/optimzedheatngies/optimalcontrlMICHAELOZURKEWICHANDR.SBERYDepartmntofChemistryandtheJamesFranckInstiute,TheUniversityhicgo,hicgo,Ilinois60637ContributedbyR.StephenBery,ember29,1980ABSTRCThemethodsoffiniteimthermodynamicsareusdtofindtheoptimaltimepathofanOtocyclwithrictonandatlekage.Optimltyisdeinebymaximzionheorkpeyclehesysmisconstranedooperatefxedfrequency,sotmaximumpowriobtained.Theeulisnimprovemntofabout10inthefctivenesecondlaefcncyofconventonalarsnusoidalengine.Finitemhermodynamisisnxtensionithemodynamicsrlvantiprncplacosstentrpaofthesubjct,fromthemosabstrleveltohemostapplied.Thepproahibadontheconsructiofgenealizedtmmicpotentils1forprocescontaningtimeorrateondionsamongtconsraintsonthesystm2andonthedetrminatonofoptmalpahshayildtheextrmorespondingohosegenerlizedpotentals.Hretofor,workonfiniteimtrmodynamicshasconcentratdonratheridealizemodels27andonexistncheorms2,alontheabstrideofhesubjec.Thisworkisintendedstpconneingtabstrcthermmiceptsthavemrgedinfnitimhermodynamisihprial,engineerngsiofubject,hedesgnprincplesofaelmchine.Inthirport,wetramodeloftheinternalcombustionenginecloselyrlatedotheidealOocyclebutihconstraintsnformofhewomajorlsfoundinrlengines.Woptimztheenginebycontrollingtimedependenceofthevolumethais,thepitonmoton.Asarult,ithoutundetakingatldengineringsudy,warbletoundersandhowtloseafecdheimepahofhepistonandtoetimtheimprovementineficncyobtinablbyoptmztpistmotion.THEMODLOurmodelisbaedonthestandardfourstroketocycle.Thisconsistofanintkestroke,acompreontroke,powetoke,andnexhausstrokeHerwbrieflydescribehebasiftursofhismodelandmhodusdtfindheoptimalpistonmoton.Adetaledprentatiwilbegivenelswhere.Wsumhathecomprionatio,fueltoairtio,fuelconsumption,andperiodofthecyclealrefixed.Tseonstrntservetopurposes.Frt,heyreductheoptimztionproblmtofindinghepitmotion.Alo,theyguaanttharformancecrteanotconsiderednhisanalysisarecomparablethoseforrelngine.Relxingnyofhestrantscaonlyimprovetpeformncfurr.Wekehelosestobehealekageandricton.Bothoftheseartedependentandthusafcttimerponsoftsystm.Thealekisaumdtobeproportionaltoheinsntneoussurfaceofthecylinderandtohetemperaturediferncbetwentheorkingfluidandtwli.e.,Newtoninheloss.Bcushistmpeaturdifrnceislargeonlyonhepowerstoke,alossincudedonlyonroke.Theictonforctkentobeproporionaltopitonvelocity,correspondingtoelubraedmtalonmealslidingthus,hefriconaosseaditlrelad,tsquarofheveocity.Theselossarenotsameoralstroke.Thehighprsurinhepowetokemakesfrictoncoefinthigherthaniheotrstoke.Thentakestrokehascontributiondueoviscouslowthroughthevalve.Tfuncionweoptimzedistmaximumworkpercycle.Bcausebothfuelconsumptionandcycltimarfxed,hiloisequivalenttomaximizngicencyandtheavergepower.Infidgthoptimalpistonmti,wefirstepartedhpowerandnopowerstokes.Aunspecebutfxedmewalotdtohepowsokeitheminderofhecycltimegivetohenonpowrstokes.Bhporionsoftcycleroptimzeithhistimeconstraintndwertncombinedtofindtotalorkperl.Tduratonofpowrsokestnvaidandtheprocesasrepetduntilthenetworksmximum.Theoptimalpistonmotiforthenonpowrsokesakesimpleform.Becausofthequadraticveloctydependenceofriconlose,toptimummotonholdsthevelociyconsntduringmosofachstroke.Atndsofhesr,thepistacelrasnddeelratsthemaximumlowedra.Becaustfictonloserhigheontintakestroke,heoptimlsolutionaotsmortimtohisrokehantoothetwo.ThepistonvelocityasfunctioftmeihownFg.1.Thepowerstokewasmoredificultooptimzebecauseofthepresncoftheatlek.heproblmwaolvedbyusingthevaraionaltchniqueoptimalcontrolory8.Theformalismyieldstheequationofmotionofthepisonasfourthordersetofnonlineardierntiaquaions.Tsersolvednumericly.TheresulingmotionishowniFig.1fortherecyclTasymmtrishapeofthepistonmotiontpowerstokearisefromtheradeoffbetwenfriconndheatleklose.Ahebeginningofthehegaahot,cpableofyildinghigheficncy,ndtratofatlossihigh.Iistrefordvantgeoustomakethevelocityhionthispasroke.Aworkiextacd,tsecoolandherteofatekagediminiherelativetofictonaloss.ConsquentlyheoptimlpathmovesolowrltesatpowrsprocedsThesolutionswrobtinedfitwihunlimtdacelrationndtnwithlimtsonacelrationnddecelation.Thelaersuatonyieldssulfmlriothercontextundenameofturnpikesolution9.Thesystmtritoopeateslongasposiblatisoptimalforardbackwardveloctes,byacelangnddeclrtingbetentheeveoctesthemximumtes.Inhiwy,tsystmspendsasmuchmeasposiblmovingalongisbetorturnpikepath.RESULTParmetrsforthecomputationswertakenfromref.10or,inthecaseofthefrictoncoefint,adjusedtogivefrctionalosseofthemagnitudedinrf.10.ThoseparametrsrgiveniTable1.TherultclulionsofsometypicalsargiveninTbl2,wheetyrcompardihonventionalOtocyclnginehavingthesmecompresionraiobutastndanearsnusoidalmoton.Theeftivesεtheraioofworkdoneteveriblework,locledthesecondlawcncyilightlyhigherfortheoptimzednginehospistonaraionlimtdto5x103m/sec2，tmaximumofconventionaleofthefirow.Iftpissalowedthave4timshe