燃燒學(xué)的理論方法與應(yīng)用(船舶排放)

InternationalMaritimeOrganization(IMO)isanagencyoftheUnitedNationswhichhasbeenformedtopromotemaritimesafety.IMOshippollutionrulesarecontainedinthe“InternationalConventiononthePreventionofPollutionfromShips”,knownasMARPOL73/78.On27September1997,theMARPOLConventionhasbeenamendedbythe“1997Protocol”.AnnexIRegulationsforthePreventionofPollutionbyOilAnnexIIRegulationsfortheControlofPollutionbyNoxiousLiquidSubstancesinBulkAnnexIIIPreventionofPollutionbyHarmfulSubstancesCarriedbySeainPackagedFormAnnexIVPreventionofPollutionbySewagefromShipsAnnexVPreventionofPollutionbyGarbagefromShipsAnnexVIPreventionofAirPollutionfromShipsMARPOLAnnexVIsetslimitsonNOxandSOxemissionsfromshipexhausts,andprohibitsdeliberateemissionsofozonedepletingsubstances.wasadoptedSeptember1997andenteredintoforceon19May2005.第一頁，共115頁。國際海事組織IMO批準(zhǔn)了修訂的船舶廢氣排放規(guī)則:IMO第57屆海洋環(huán)境保護(hù)委員會于2008年3月31日–4月4日在倫敦召開。會上批準(zhǔn)了對MARPOL附則VI修正案，以減少船舶有害氣體的排放。硫氧化物（SOx）主要的變化是逐步減少船舶硫氧化物(SOx)的排放,燃油含硫量從當(dāng)前4.50%減少到3.50%從2012年1月1日生效，然后減少至0.50%從2020年1月1日起生效，并最晚不遲于2018年完成可行性評估計。硫排放控制區(qū)（SulphurEmissionControlArea-SECA）的適用標(biāo)準(zhǔn)將減少到1.00%（當(dāng)前為1.50%），從2010年1月1日起生效，并進(jìn)一步減少的0.10%，于2015年1月1日起生效。目前的附則VI，指定了兩個硫排放控制（SECA），也就是波羅地海（theBalticSea）和北海（theNorthSea），也包括英吉利海峽（theEnglishChannel）。第二頁，共115頁。

逐步減少發(fā)動機(jī)氮氧化物(NOx)排放的建議獲得通過。TierI

適用于2000年1月1日后2011年1月1日前安裝在船上的發(fā)動機(jī)，即氮氧化物的排放量為17g/kWh，已在現(xiàn)在的附則VI中有規(guī)定。

TierII將氮氧化物的排放量減少到14.4g/kWh，適用于2011年1月1日后建造或裝船的發(fā)動機(jī)。

TierIII將氮氧化物的排放量減少到3.4g/kWh，適用于2016年1月1日安裝在船上的發(fā)動機(jī)，但僅在排放控制區(qū)（EmissioncontrolArea）適用，在非排放控制區(qū)，等級II仍然適用。對1990年1月1日后2000年1月1日前安裝的輸出功率為5000kW，單缸排量為90L或超過90L的柴油發(fā)動機(jī)，海洋保護(hù)環(huán)境委員會（MEPC）同意用17.0g/kWh的氮氧化物排放標(biāo)準(zhǔn)。海洋環(huán)境保護(hù)委員會（MEPC）批準(zhǔn)了氮氧化物技術(shù)規(guī)則修訂草案，并在2008年出臺修訂的氮氧化物技術(shù)規(guī)則。新的技術(shù)規(guī)則包括新的第7章，對2000年前發(fā)動機(jī)氮氧化物排放進(jìn)行了規(guī)定，此外還包括對現(xiàn)有發(fā)動機(jī)的直接測量和進(jìn)行監(jiān)測的方法以及發(fā)證程序，以及對適用等級II和等級III的發(fā)動機(jī)的測試。氮氧化物(NOx)第三頁，共115頁。廢氣清洗系統(tǒng)(ExhaustGasCleaningSystems)

本次會議同意將對廢氣清洗系統(tǒng)中間沖洗水的排放標(biāo)準(zhǔn)納入到修訂的廢氣清洗系統(tǒng)的導(dǎo)則中。揮發(fā)性有機(jī)物（VOCs）本次會議批準(zhǔn)了（VolatileOrganicCompounds）揮發(fā)性有機(jī)物管理計劃導(dǎo)則的草案。揮發(fā)性有機(jī)物管理計劃的目的是為了確保適用于附則VI第15條的液貨船，能防止或者將揮發(fā)性有機(jī)物的排放減少到可能的程度。附則VI第15條要求締約國向IMO遞交一個通報，該通報應(yīng)包括所控制的液貨艙尺寸、液貨所需蒸汽控制系統(tǒng)及所采取得控制措施生效的日期等信息。海洋環(huán)境保護(hù)委員會通知IMO秘書處邀請國際化標(biāo)準(zhǔn)組織(ISO)考慮燃油標(biāo)準(zhǔn)的制訂，重在強(qiáng)調(diào)空氣質(zhì)量、船舶安全，發(fā)動機(jī)性能以及船員健康并推薦給IMO考慮。

第四頁，共115頁。溫室氣體(GHG)

本次會議批準(zhǔn)了秘書長關(guān)于加快溫室氣體排放工作的建議，特別是二氧化碳CO2排放指數(shù)方案的制訂以及二氧化碳CO2排放基線調(diào)查的開展。溫室氣體排放工作組編寫了下一步實際工作計劃包括控制CO2排放的短期及長期措施，該計劃獲得了海環(huán)會批準(zhǔn)。

短期措施包括建議建立全球航運(yùn)燃油稅征收方案（globallevyscheme）以減少溫室氣體排放。根據(jù)該計劃，所有從事國際航運(yùn)的船舶將需繳納基于每噸定值的燃油稅。

GHG工作組確認(rèn)的長期的措施獲得了海環(huán)會的批準(zhǔn)并需進(jìn)一步研究，這些措施包括：船舶設(shè)計的技術(shù)措施；使用替代燃料；新船的CO2-設(shè)計指數(shù)；CO2運(yùn)行指數(shù)的外部查驗；統(tǒng)一的CO2運(yùn)行指數(shù)限制以及對不符合的懲罰；排放交易機(jī)制（EmissionsTradingScheme-ETS）和/或清潔發(fā)展機(jī)制(CDM),以及港口基建費(fèi)征收中的CO2排放因素。第五頁，共115頁。NOxEmissionStandardsNOxemissionlimitsaresetfordieselenginesdependingontheenginemaximumoperatingspeed(n,rpm),asshowninTable1andpresentedgraphicallyinFigure1.TierIandTierIIlimitsareglobal,whiletheTierIIIstandardsapplyonlyinNOxEmissionControlAreas.Table1.MARPOLAnnexVINOxEmissionLimitsTierDateNOxLimit,g/kWh

n<130130

≤

n

<

2000n≥2000

TierI200017.045·n-0.29.8

TierII201114.444·n-0.237.7

TierIII2016?3.49·n-0.21.96

?InNOxEmissionControlAreas(TierIIstandardsapplyoutsideECAs).

第六頁，共115頁。Figure1.MARPOLAnnexVINOxEmissionLimits第七頁，共115頁。EmissionControlAreas.TwosetsofemissionandfuelqualityrequirementsaredefinedbyAnnexVI:(1)globalrequirements,and(2)morestringentrequirementsapplicabletoshipsinEmissionControlAreas(ECA).AnEmissionControlAreacanbedesignatedforSOxandPM,orNOx,orallthreetypesofemissionsfromships,subjecttoaproposalfromaPartytoAnnexVI.ExistingSOxEmissionControlAreasincludetheBalticSea(adopted:1997/enteredintoforce:2005)andtheNorthSea(2005/2006).FutureEmissionControlAreascouldalsoincludezonesaroundpollutionsensitiveports.第八頁，共115頁。TierIIstandardsareexpectedtobemetbycombustionprocessoptimization.Theparametersexaminedbyenginemanufacturersincludefuelinjectiontiming,pressure,andrate(rateshaping),fuelnozzleflowarea,exhaustvalvetiming,andcylindercompressionvolume.TierIIIstandardsareexpectedtorequirededicatedNOxemissioncontroltechnologiessuchasvariousformsofwaterinductionintothecombustionprocess(withfuel,scavengingair,orin-cylinder),exhaustgasrecirculation,orselectivecatalyticreduction.Pre-2000Engines.Underthe2008AnnexVIamendments,TierIstandardsbecomeapplicabletoexistingenginesinstalledonshipsbuiltbetween1stJanuary1990to31stDecember1999,withadisplacement≥90literspercylinderandratedoutput≥5000kW,subjecttoavailabilityofapprovedengineupgradekit.第九頁，共115頁。Testing.EngineemissionsaretestedonvariousISO8178cycles(E2,E3cyclesforvarioustypesofpropulsionengines,D2forconstantspeedauxiliaryengines,C1forvariablespeedandloadauxiliaryengines).Additionofnot-to-exceed(NTE)testingrequirementstotheTierIIIstandardsisbeingdebated.NTElimitswithamultiplierof1.5wouldbeapplicabletoNOxemissionsatanyindividualloadpointintheE2/E3cycle.Enginesaretestedusingdistillatedieselfuels,eventhoughresidualfuelsareusuallyusedinreallifeoperation.FurthertechnicaldetailspertainingtoNOxemissions,suchasemissioncontrolmethods,areincludedinthemandatory“NOxTechnicalCode”,whichhasbeenadoptedunderthecoverof“Resolution2”.第十頁，共115頁。SulfurContentofFuelAnnexVIregulationsincludecapsonsulfurcontentoffueloilasameasuretocontrolSOxemissionsand,indirectly,PMemissions(therearenoexplicitPMemissionlimits).SpecialfuelqualityprovisionsexistforSOxEmissionControlAreas(SOxECAorSECA).ThesulfurlimitsandimplementationdatesarelistedinTable2andillustratedinFigure2.Heavyfueloil(HFO)isallowedprovideditmeetstheapplicablesulfurlimit(i.e.,thereisnomandatetousedistillatefuels).Alternativemeasuresarealsoallowed(intheSOxECAsandglobally)toreducesulfuremissions,suchasthroughtheuseofscrubbers.Forexample,inlieuofusingthe1.5%SfuelinSOxECAs,shipscanfitanexhaustgascleaningsystemoruseanyothertechnologicalmethodtolimitSOxemissionsto≤6g/kWh(asSO2).第十一頁，共115頁。Table2.MARPOLAnnexVIFuelSulfurLimitsDateSulfurLimitinFuel(%m/m)

SOxECAGlobal

20001.5%4.5%

2010.071.0%

20123.5%

20150.1%

2020a0.5%

a-alternativedateis2025,tobedecidedbyareviewin2018

第十二頁，共115頁。Figure2.MARPOLAnnexVIFuelSulfurLimits第十三頁，共115頁。EUStandardsforNon-RoadEngines（April2004）StageIII/IVlimitsareharmonizedwiththeEPATier3/4standards.第十四頁，共115頁。

TheEnvironmentalProtectionAgencyoftheUnitedStateshasbeenprotectinghumanhealthand

theenvironmentsince1970.LiketheEU,theEPAhasadoptedtheregulationsissuedbytheIMO

buthasuseditasafoundationforamorestringentpolicyformarineemissions(fornon-road

engines).TheEPAregulationsystemisdividedintothreetiersthataremeanttoprogressivelyloweremissions.Tier1standardsareequivalenttotheMARPOLAnnexVINOxlimitsandwerevoluntarywhenfirstimplementedbutmandatoryby2004.TheTier2standardsforallenginesizes,whicharemorerestrictivethanTier1,aretobeinplaceby2007.Tier3standardsforenginesratedover37kW(50hp)willphase-infrom2006to2008.TheTier4standardsthatcurrentlyexistdonotapplytomarinedieselengines.However,Tier4criteriawereissuedalongwithan‘AdvanceNoticeofProposedRulemaking’,whichoutlinedtheintendedfutureemissionstandardsformarinedieselengines.EnvironmentalProtectionAgency(EPA)第十五頁，共115頁。EPATier2MarineEmissionStandard第十六頁，共115頁。OveralltheEPAregulations,likethoseoftheEU,aremorerestrictivethanIMOMARPOLAnnexVI.TheEPApolicyformarineenginesrequiresbetterenginecooling,electroniccontrolsandotherdesignmodifications.Also,aswiththeStagesoftheEUsystem,thestandardsoutlinedintheTiersystemlistspecificrestrictionsforanumberofairpollutants(e.g.PM,HC,COandNOx),whileIMOdoesnot.

第十七頁，共115頁。CombustioninHighSpeedDieselEnginesASI-AftertheStartofInjection第十八頁，共115頁。ConceptualdieselSprayCombustionModelFromSAEpaper1997-970873,SocietyofAutomotiveEngineers,Inc.)第十九頁，共115頁。第二十頁，共115頁。

1、柴油(約350K)噴入氣缸內(nèi)后，熱空氣(約950K)卷入并加熱燃油，油束破裂。當(dāng)燃油被熱空氣加熱至約650K時，在濃混合氣區(qū)(燃空當(dāng)量比約4.0，當(dāng)?shù)販囟燃s825K)出現(xiàn)預(yù)混合火焰，生成大量富油燃燒產(chǎn)物(CO、未燃HC、PM)當(dāng)?shù)販囟壬叩郊s1600K，此時的放熱量約為總放熱量的10%-15%。

2、在油束外圍出現(xiàn)擴(kuò)散火焰層，富油燃燒產(chǎn)物不斷進(jìn)入擴(kuò)散火焰層進(jìn)行擴(kuò)散燃燒，產(chǎn)生約2700K的高溫，使PM氧化，并生成CO2和水蒸汽。同時，擴(kuò)散火焰層的高溫使空氣中的N2和O2反應(yīng)，生成大量NOX。擴(kuò)散燃燒放熱量占總放熱量的85%-90%。第二十一頁，共115頁。

ThereareanumberofdifferentformationmechanismsresponsibleforNOxincombustionprocesses.Therelativeimportanceofthesedifferentmechanismsisstronglyaffectedbythetemperature,pressure,flameconditions,residencetimeandconcentrationsofkeyreactingspecies.ThereactingspeciescanpotentiallyproceedthroughanumberofdifferentchemicalmechanismsresultingintheformationofNOx.Atthetemperaturesgreaterthan2000Koxygencombineswithnitrogentoformoxidesofnitrogen.Initially,NOisformed,thenduringthegasexpansionprocessinthecylinderaportionoftheNOconvertstoformnitrousoxide(N2O)andnitrogendioxide(NO2).ThecombinationofNO,NO2andN2OisknownasNOx.NOxFormation第二十二頁，共115頁。生成NO主要化學(xué)反應(yīng)鏈見下圖，該反應(yīng)鏈已得到大多數(shù)研究人員的認(rèn)可。在燃燒過程中生成的氮氧化物主要源于燃燒空氣中的氮氣(N2)和燃料中的有機(jī)氮。在燃料中如有機(jī)氮的重量含量大于1％，NO的最終排放通常會增加10％~30％。在燃油的霧化過程中，這些有機(jī)氮會從燃料中釋放出來，并快速生成氫氰化物(HCN)和氨氣(NH3)。第二十三頁，共115頁。ThermalNOThethermalmechanism,alsoknownisthe"extendedZeldovichmechanism",isresponsibleforthemajorityofNOxemissionsfromdieselengineswhenpeakcombustiontemperaturesexceed2000K.Sincetemperaturesofthismagnitudearedesirabletomaximizeengineefficiency,thismechanismhasbeenstudiedextensivelyandisfairlywellunderstood.Thethreechemicalreactionsthatareimportantinthismechanismare:

O+N2=NO+N{1}N+O2=NO+O{2}N+OH=NO+H{3}Theoverallreactionrateforthismechanismisslowanditisverytemperaturesensitive.Asaconsequence,thermalNOonlyappearsinsignificantquantitiesinthepostcombustion.Also,theactualNOconcentrationfromthismechanismdeviatessignificantlyfromequilibriumconcentrations.Thisgivesthismechanismaverystrongtimedependencethatisimportantforlowspeedengines.第二十四頁，共115頁。ThermalNOTheforwardrateofreaction{1}andthereverseratesofreactions{2}and{3}havestrongtemperaturedependencies.Therefore,thismechanismisveryimportantathighertemperatureandatair/fuelmixturesthatareclosetostoichiometric.ItscontributiontoNOxemissionsisalmostinsignificantattemperaturesbelow1700K,butisstronglyacceleratedastemperatureincreasesabove2000K.Thetemperaturesensitivityofthismechanismalsomeansthatasthetemperatureinthecombustionchamberdropsduringtheexpansionstroke,theNOconcentrationfreezesshortlyaftertopdeadcentre.PostcombustionequilibriumconcentrationsofOandOHareveryimportantforthismechanism.FactorsthatincreaseordecreasetheconcentrationsoftheseradicalscanhaveasignificantimpactonNOfromthismechanism.第二十五頁，共115頁。PromptNOThepromptNOmechanism,alsoknownasthe"Fenimoremechanism",isveryrapidandresultsinNOformationinthecombustionzone.ThemostimportantpathwayforpromptNOisinitiatedbytherapidreactionofhydrocarbonradicalsfromthefuelwithmolecularnitrogen,leadingtotheformationofaminesorcyanocompoundsthatsubsequentlyreacttoformNO.ThemostimportantinitiationreactionforpromptNOis:

CH+N2=HCN+N{4}SubsequentrapidconversiontoNOisstronglyaffectedbyOandOH.PromptNOismostsignificantwhencombustionoccursatfuelconcentrationshigherthanstoichiometrywherethereisahighconcentrationofhydrocarbonradicalstoformHCNandtheconcentrationsofOandOHarestillhighenoughtocausetheHCNtoproceedtoNOthroughthefollowingreactionsequence:第二十六頁，共115頁。

HCN+O=NCO+H{5}NCO+H=NH+CO{6}NH+H=N+H2{7}N+OH=NO+H{8}Theratesofthesereactionsarenotverysensitivetotemperature.ReactionsarerapidandthesequenceresultsinNOformationintheflamezone.HightemperaturesdonotaffectedpromptNOtothesameextentasthermalNO.PromptNO第二十七頁，共115頁。

Zeldovichmechanism反應(yīng)鏈ThermalNO

對于反應(yīng)溫度是非常敏感的。通過計算流體動力學(xué)的仿真模擬計算和燃燒實驗發(fā)現(xiàn)：當(dāng)溫度低于1700K時，NO的生成速率比較緩慢；溫度上升，特別當(dāng)溫度大于2000K，NO的生成度，并在高溫時盡可能地減少供氧量，可以有效地降低NO的生成和排放。然而Fenimoremechanism反應(yīng)鏈PromptNO對于反應(yīng)溫度是非常不敏感。燃料中如有機(jī)氮在燃油霧化過程中將從燃料中釋放出來，會快速生成氫氰化物(HCN)并在較低的溫度下(小于1100K

)反映生成NO

。第二十八頁，共115頁。N2OPathwayAnotherNOformationmechanismimportantincombustionistheN2Opathway.Theinitialreactionforthispathwayisthethreebodyreaction:

O+N2+M=N2O+M{9}WhileN2OgenerallyrevertsbacktoN2,thisisnotalwaysthecase.Underconditionswheretheairfuelratioislean,NOcanformthrougheitherofthefollowingtworeactions:N2O+O=NO+NO{10}H+N2O=NO+NH{11}ThisNOformationrouteisfuelandpressuredependent.Athigherpressuresandlowertemperature,thethree-bodyinitiationbecomescompetitivewiththeO+N2reactioninthethermalmechanism.第二十九頁，共115頁。FuelNitrogenManyheavyfueloilscontainorganicnitrogenboundtothefuelmolecule.ThisnitrogencanreacttoformadditionalNO.TheextentoftheconversionoffuelnitrogentoNOisnearlyindependentoftheidentityofthemodelcompound,butisstronglydependentonthelocaltemperatureandstoichiometryandontheinitiallevelofnitrogencompoundinthefuel-airmixture.ThepathwaythatfuelnitrogenfollowstoformNOdependsonwhetherthenitrogenisboundtoanaromaticringoranamine.Ifthefuelnitrogenisboundtoanaromaticring,thenitrogeninthefuelformshydrogencyanide(HCN).Intheflame,equilibriumexistsforthereactionHCN+H=CN+H2andthenitrogenwouldformNOthroughamechanismthatisessentiallythatofpromptNO.第三十頁，共115頁。Ifhoweverthefuelnitrogenisboundtoanamine,ammonia(NH3)wouldformquicklyintheflamezone.Inlargeradicalpools,theNHcompoundsareinequilibrium:

NH3=NH2=NH=N{12}TheimportantreactionsforformingNOfromthisradicalpoolare:

NH2+O->NHO+H{13}NH2+O2->NHO+OH{14}HNO+X->NO+XH{15}HNO+M->NO+H+M{16}第三十一頁，共115頁。NOxinDieselFlames

ThecriticalflamezoneinDieselcombustionforNOformationisthediffusionflamethatsurroundsthejet.InnormalDieselcombustion,thefuelhydrocarbonradicalsarebrokendownintofuelfragments,H2andCOinthepartiallypremixedzonethecoreofthefueljet.WhileNOcanforminpartiallypremixedflames,thetemperatureofthiszoneinDieselenginesisgenerallytoolowtoresultinsignificantNOformation.Thefuelfragments,H2andCOfromthecoreofthejetarethefuelthatfeedstheouterdiffusionflame.第三十二頁，共115頁。NOxinDieselFlamesUnderdiffusionflameconditionsfedwithhydrocarbonfragments,H2andCO,theNOformationmechanismsmentionedcanallplayanimportantrole.ThermalNOisespeciallyimportantwhenpeaktemperaturesinconditionsexceed2000K.PromptNOwillalmostcertainlybeproducedfromhydrocarbonfuelfragmentsanditsrelativerolewouldtendtoincreaseasmeasuressuchaschangesincombustionphasingaretakentolowercombustiontemperaturestoreducethermalNO.TheimportanceoftheN2OmechanismunderDieselengineconditionshasalsobeenrecognized.Itsrelativeimportanceisincreasedunderconditionsofincreasedturbulence.ItisespeciallyimportanttoconsidertheNOformedfromorganicfuelnitrogeninenginesburningheavyfuels.Mostofthesefuelscontainsignificantamountsofnitrogen.TherelativeimportanceoffuelnitrogenwouldincreaseasothermeasuresaretakentoreduceNOxformedbyothermechanisms.第三十三頁，共115頁。NOxREDUCTION–GENERALOVERVIEWMethodstoreduceNOxemissionsmaybecategorizedaseitherPrimaryorSecondary.PrimarymethodsreduceNOxformationatthesourceintheengineandincludemethodssuchasenginetuning/modificationsandwaterbasedtechnologies.SecondarymethodsreduceNOxintheexhaustgasbydownstreamtreatment(reductionofNOxafterformationintheexhaust).Althoughsomesecondarymethodsareveryeffective,forexample,SelectiveCatalyticReduction(SCR)hasareductioncapabilityofupto95%,overallcostsaretypicallyhigher.Primarymethodstypicallyhavehigherinitialcosts,usuallyassociatedwiththemodificationstotheengine,buttheoverallexpenseisconsiderablyless.TheeffectivenessofdifferentNOxreductionmethodsvariesconsiderably.Dataisoften'manufacturerclaimed'andeffectivenesscanbedependentonthespecificengine,installationandloadconditions.第三十四頁，共115頁。NOxReductionMethods第三十五頁，共115頁。1.Intakeairhumidification/waterinjection2.Stratifiedfuelwaterinjection3.Directwaterinjection(DWI)witha“two-needletype”fuelandwaterinjectionnozzle4.DWIwitha“separatewaterinjectionnozzle”5.Fuel-wateremulsionWater-BasedEmissionControlTechnologiesTheeffectsofthisDWIatbothanearliertiming(EDWI)andalatertiming(LDWI)oncombustionwereclarifiedmainlybyhighspeedvisualstudiesofburningsprays.第三十六頁，共115頁。HumidAirMotor(HAM)(4-Stroke)DiagramofHAMprinciple1.Seawaterinjectionintothechargeairbyanadd.2.HAMvesselbetweenTCandchargeairmanifold3.HT-coolingwaterand/orexhaustgasheatusedforwaterpreheating3.CACbypassed4.NOxreduction:65%(withadditionalheat)第三十七頁，共115頁。NOx–Humidity–Trend第三十八頁，共115頁。EngineDesign:1.OperationwithHAMshiftturbochargertosurginglimit?TCrematchingandbypass2.CurrentchargeaircoolerbypassedEngineperformance:1.IncreasedboostpressureandTCspeed2.Exhaustgastemperatureandenginecomponentstemperaturesignificantlylower3.NoTCwashingrequired4.LimitedincreaseofSFOCabout1%,nodeviationovertime5.Enginederatingnecessary(1,050kW/cyl.insteadof1,200kW/cyl.for48/60B)EngineAdaptation第三十九頁，共115頁。ScavengeAirMoistening

(SAM)System(2-Stroke)1.Firststageseawater,followingstagesfreshwaterinjectionintochargeair2.InstalledinsidetheCACcasing3.Onlydesignedfor2-stroke(stillunderdevelopment)4.NOxreduction:40%第四十頁，共115頁。ScavengingAirMoistening(SAM)systemforNOxreduction第四十一頁，共115頁。SAMSystem8S60MC-100%Engineload第四十二頁，共115頁。SAMSystemInstallationofparts第四十三頁，共115頁。HumidifiedAirSystems:HAM,CASSandTDCSystems第四十四頁，共115頁。TheHAMprocessdesignedbyMuntersEuroformGmbHwasfirstbenchtestedonaMANB&W3V40/50prototype4strokemediumspeeddieselengineintheresearchanddevelopmentfacilitiesofS.E.M.T.Pielstickin-serviceverificationwascarriedoutinco-operationwithVikingLineononeengine(12PC2.6,5,750kW)onboardtheRoRoferry"Mariella”operatingintheBalticSea.TheHAMsystemwasinstalledonmainengineNo.1inthesummerof1999.NOxreductionsof60%wereclaimedwithafinalcertificationvalueof4.4g/kWhNOx.Thehumidificationvesselis4mlong,1.4mindiameterandhas3humidifierstageswhichhumidifyandcooltheairfromapproximately160oCattheoutletofthecompressordowntoapproximately65-70oC.Theairreachesabout98%relativehumiditywhichcorrespondstoanabsolutehumidityintherangeof60to80gwater/kgdryair.Seawaterisusedandre-circulateduntilthesaltcontentincreasesbyabout6%.第四十五頁，共115頁。Duringtheyear2000,Marioff,adeveloperofwatermistsystemsforfiresuppression,startedtodeveloptheCombustionAirSaturationSystem(CASS).Thekeytothissystemdevelopmentisthespraynozzleandcontrolsystem.Airandwaterinvaryingratiosaresuppliedtothenozzleprovidingwaterdropletsizesaround50to200μmandW/Fratiosfrom0.5to2.5.Theair/waterratiosuppliedtothenozzleisvariedsothatthewaterdropletsizeisafunctionofengineloadwiththesmallestdropletsizesproducedwhentheengineloadislowandgoodevaporationismoredifficult.Earlyin2001,apressreleasewasissuedthatstatedthatMarioffandW?rtsil?hadformedapartnership.During2001andearly2002,full-scaleenginetestswerecarriedoutatW?rtsil?inFinland.ReductionofNOxtolessthan3g/kWhwasclaimedatthetimeforstartingvaluesof10-15g/kWh.Currentclaimsare~50%NOxreductionatW/F~2.0andsaturatedairat50-90oC.第四十六頁，共115頁。PrototypeintakeairwaterinjectionsystemshavebeendevelopedbyM.A.TurboandtheTransportationDevelopmentCentre(TDC).ReadersaredirectedtoSection8ofthisreportfordetailsonthesesystemsandtestdatasets.Bothsystemsareintendedforretrofittoexistingengines.UnlikeHAMandCASSwhicharesophisticateddesignsintendedtoinputgaseouswater(vapour)intothecylinder,theM.A.TurboandTDCsystemsintroduceatomizedliquidwaterintotheintakeairsupply(whichmayormaynotbevapourizedwhenenteringthecylinder).Thepurposeofcomparisonissimplytohighlightdifferences(NOxreductionandthesystemparameterswherethisreductionachieved)betweenintakeairwaterinjection(TDCmultipointsystem)andintakeairhumidification(CASS,HAM)systems.第四十七頁，共115頁。UnliketheMunters’HAMsystemwhichclaimsaself-regulatingbehaviour,theW?rtsil?approachrequirescarefulcontrolofthewaterflowtoachievetheproperhumidification.TheW?rtsil?approachalsousesmultiplestagesofhumidificationwithheatingorcoolinginbetweenthestagesasneeded;humidificationofairafterthecompressor.Thesystemrequiresmeasurementofintakemanifoldtemperature,humidityandinsomecases,pressure.Thesystemalsorequirespurewater;seawaterwouldneedtobetreatedfirstbeforeitcouldbeused.第四十八頁，共115頁。NOxREDUCTION-DIRECTIN-CYLINDERINJECTIONW?rtsil?hasbeendevelopingthedirectwaterinjection(DWI)technologysincetheearly1980s.Thistechnologywaschosenforanumberofreasons.Inthebeginningitwasrecognizedthattherewerelimitedadverseeffectsoninjectionequipmentreliability,thesetupwasfairlysimpleandthesystemwascomparativelycheap.W?rtsil?pursuedthistechnologyandthroughouttheyearstherehasbeenextensiveresearchanddevelopmentactivity,whichhasincludedaconsiderableamountoffieldtesting.CurrentDWIsystemsbyW?rtsil?boastNOxemissionreductionof50-60%(withoutadverselyeffectingpoweroutput),whichtranslatesto4-6g/kWhofNOx(forMarineDieselOil)and5-7g/kWh(forHeavyFuelOil).ThesystemtypicallyoperatesataW/Fratioof0.40to0.70.TheW?rtsil?techniqueforDWIalsoallowsforwatershut-off,asthewatersystemiscontrolledseparatelyfromthefuel,sothattheenginecanbeoperatedwithorwithoutwaterinjection.W?rtsil?claimsthatbothinvestmentandoperationalcostsarelowandthatspacerequirementsforthesystemisminimal,allowingforeasyinstallation.W?rtsil?enginesthatincorporateDWItechnologythatarecurrentlycommercia-llyavailableare:W?rtsil?46,W?rtsil?Vasa32,W?rtsil?38,W?rtsil?32,SulzerZA40第四十九頁，共115頁。W?rtsil?combinedwaterandfuelnozzleformediumspeedengines

DWIunitsforpressurizingwater

W?rtsil?DirectWaterInjectionTechnology第五十頁，共115頁。W?rtsil?

waterandfuelvalveneedleliftformediumspeedengines第五十一頁，共115頁。DWIinstallation–W46第五十二頁，共115頁。第五十三頁，共115頁。CFDsimulationofthecombustionprocesswithdirectwaterinjection(DWI)indicatesthelevelsofNOX.Thesepicturesshowthatthewaterissprayed(left)directlyintotheareaofhighestNOXconcentration.TheNOXconcentrationsarecalculatedfor12degreescrankangleafterthestartoffuelinjection.第五十四頁，共115頁。AlthoughDWIcanbeappliedalone,itmightbemoreinterestingtoapplyitincombinationwithinternalexhaustgasrecirculation(EGR),asinWaCoReG(watercooledresidualgas)bywhichweexpecttoobtainupto70percentreductioninNOXemissionsbelowtheIMOlimit.ThiswouldbringNOXemissionsdowntoabout5g/kWh.ExhaustgasrecirculationreducesNOXformationatsourcebyreducingtheoxygenavailableintheenginecylinderandincreasingtheheatcapacityofthecylindercharge.Incontrasttofour-strokeenginesinwhichitiscommonpracticetorecirculateexhaustgasesthroughexternalmanifolds,inlow-speedtwo-strokeenginesweprefertoadapttheenginescavengingprocesstodecreasethepurityofgasinthecylinderatthestartofcompression.Thisisachievedbyreducingtheheightofscavengeportstoreducethescavengeairquantityflowingthroughthecylinder.Onebenefitisthatsmallerturbochargersarerequiredforthereducedgasflows.Thelowerscavengeportsalsohavethebenefitofallowinggreaterexpansioninthecylinderandthusimprovingfuelconsumption.Thereducedgasflowshavethefurtherbenefitthatexhaustgastemperaturesareraisedwhichishelpfulforheatrecoverysystems.第五十五頁，共115頁。PrincipleoftheWaCoReGprocessinwhichNOXformationisrestrictedpartlybydegradingthepurityofthecylinderchargebyincreasingtheresidualgascontent,andpartlybydirectwaterinjection.Thewaterisinjectedearlyinthecompressionstroketocoolthecylindercharge.CombiningWater