英文资料.docx

英文资料.docx

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英文资料

Thisarticleisaboutlocomotivesthatrunonrails.Forthetypeofheavy-haulagetractionengine,seeRoadlocomotive（disambiguation）.FortheRussianfootballclub,seeFCLokomotivMoscow.

Threebodystylesofdiesellocomotive:

cabunit,hoodunitandboxcab.TheselocomotivesareoperatedbyPacificNationalinAustralia.

RclasssteamlocomotivenumberR707asoperatedbytheVictorianRailwaysofAustralia.

AGreenCargoRC4classelectriclocomotiverepaintedinitsoriginalliveryfortheSwedish150-yearrailwayanniversaryin2006.

Alocomotiveisarailwayvehiclethatprovidesthemotivepowerforatrain.ThewordoriginatesfromtheLatinloco–"fromaplace",ablativeoflocus,"place"+MedievalLatinmotivus,"causingmotion",andisashortenedformofthetermlocomotiveengine,[1]firstusedintheearly19thcenturytodistinguishbetweenmobileandstationarysteamengines.

Alocomotivehasnopayloadcapacityofitsown,anditssolepurposeistomovethetrainalongthetracks.Incontrast,sometrainshaveself-propelledpayload-carryingvehicles.Thesearenotnormallyconsideredlocomotives,andmaybereferredtoasmultipleunits,motorcoachesorrailcars.Theuseoftheseself-propelledvehiclesisincreasinglycommonforpassengertrains,butrareforfreight（seeCargoSprinter）.Vehicleswhichprovidemotivepowertohaulanunpoweredtrain,butarenotgenerallyconsideredlocomotivesbecausetheyhavepayloadspaceorarerarelydetachedfromtheirtrains,areknownaspowercars.

Traditionally,locomotivespulltrainsfromthefront.Increasinglycommonispush-pulloperation,wherealocomotivepullsthetraininonedirectionandpushesitintheother,andcanbecontrolledfromacontrolcabattheotherendofthetrain.

Origins

Seealso:

Historyofrailtransport andCategory:

Earlysteamlocomotives

Firstpassengerrailway,L&MR

ThefirstsuccessfullocomotiveswerebuiltbyCornishinventorRichardTrevithick.In1804hisunnamedsteamlocomotivehauledatrainalongthetramwayofthePenydarrenironworks,nearMerthyrTydfilinWales.Althoughthelocomotivehauledatrainof10tonsofironand70passengersinfivewagonsoverninemiles（14 km）,itwastooheavyforthecastironrailsusedatthetime.Thelocomotiveonlyranthreetripsbeforeitwasabandoned.TrevithickbuiltaseriesoflocomotivesafterthePenydarrenexperiment,includingonewhichranatacollieryinTynesideinnorthernEngland,whereitwasseenbytheyoungGeorgeStephenson.[2]

ThefirstcommerciallysuccessfulsteamlocomotivewasMatthewMurray'sracklocomotive,Salamanca,builtforthenarrowgaugeMiddletonRailwayin1812.Thiswasfollowedin1813bythePuffingBillybuiltbyChristopherBlackettandWilliamHedleyfortheWylamCollieryRailway,thefirstsuccessfullocomotiverunningbyadhesiononly.PuffingBillyisnowondisplayintheScienceMuseuminLondon,theoldestlocomotiveinexistence.[3]

In1814GeorgeStephenson,inspiredbytheearlylocomotivesofTrevithickandHedleypersuadedthemanageroftheKillingworthcollierywhereheworkedtoallowhimtobuildasteam-poweredmachine.HebuilttheBlücher,oneofthefirstsuccessfulflanged-wheeladhesionlocomotives.Stephensonplayedapivotalroleinthedevelopmentandwidespreadadoptionofsteamlocomotives.Hisdesignsimprovedontheworkofthepioneers.In1825hebuilttheLocomotionfortheStocktonandDarlingtonRailway,northeastEngland,whichbecamethefirstpublicsteamrailway.In1829hebuiltTheRocketwhichwasenteredinandwontheRainhillTrials.ThissuccessledtoStephensonestablishinghiscompanyasthepre-eminentbuilderofsteamlocomotivesusedonrailwaysintheUnitedKingdom,theUnitedStatesandmuchofEurope.[4]Thefirstintercitypassengerrailway,LiverpoolandManchesterRailway,openedin1830,makingexclusiveuseofsteampowerforbothpassengerandfreighttrains.

Locomotivesvs.multipleunits

Advantagesoflocomotives

Therearemanyreasonswhythemotivepowerfortrainshasbeentraditionallyisolatedinalocomotive,ratherthaninself-propelledvehicles.[5]

Ease 

Shouldthelocomotivefail,itiseasytoreplaceitwithanother.Failureormaintenanceofthemotivepowerunitdoesnotrequiretakingtheentiretrainoutofservice.

Maximumutilizationofpowercars 

Idletrainswastecostlymotivepowerresources.Separatelocomotivesenablecostlymotivepowerassetstobemovedaroundasneeded.

Flexibility 

Largelocomotivescanbesubstitutedforsmalllocomotiveswherethegradesaresteeperandmorepowerisneeded.A'passenger'locomotivecanalsobeusedforfreightdutiesifneeded,andviceversa.

Obsolescencecycles 

Separatingthemotivepowerfrompayload-haulingcarsenablesonetobereplacedwithoutaffectingtheother.Attimeslocomotiveshavebecomeobsoletewhentheircarswerenot,andviceversa.

Safety 

Incaseofanaccident,thelocomotivemayactasbufferzonefortherestofthetrain.Ifanobstacleisencounteredontheline,theheaviermassofalocomotiveislesslikelytobedeviatedfromitsnormalcourse.Alsoitmaybesaferintheeventoffireespeciallywithdiesellocomotives.

Noise 

Asinglesourceoftractivepower,whichmeansonlymotorsinoneplace,meansthatthetrainwillbequieterthanwithmultipleunitoperation,whereoneormoremotorsarelocatedundereverycarriage.Thenoiseproblemisparticularlypresentindieselmultipleunits.

Advantagesofmultipleunits

Thereareseveraladvantagesofmultipleunit（MU）trainscomparedtolocomotives.

Energyefficiency 

Multipleunitsaremoreenergyefficientthanlocomotive-hauledtrainsandmorenimble,especiallyongrades,asmuchmoreofthetrain'sweight（sometimesallofit）isplacedondrivenwheels,ratherthansufferthedeadweightofunpoweredcoaches.

Noneedtoturnlocomotive 

Manymultipleunitshavecabsatbothends,thetrainmaybereversedwithoutuncoupling/re-couplingthelocomotive,givingquickerturnaroundtimes,reducingcrewcosts,andenhancingsafety.Inpractice,thedevelopmentofdrivingvantrailersandcabcarshasremovedtheneedforlocomotivestorun-around,givingeasybi-directionalworkingandremovingthisMUadvantage.

Reliability 

Asmultipleunittrainshavemultipleengines,thefailureofoneenginedoesnotpreventthetrainfromcontinuingitsjourney.Alocomotivedrawnpassengertraintypicallyonlyhasonepowerunit,meaningthefailureofthiscausesthetraintobedisabled.However,somelocomotivehauledpassengertrainsmayutilizemorethanonelocomotive,asdomanylocomotivehauledfreighttrains,andsoareabletocontinueatreducedspeedafterthefailureofonelocomotive.

Safety 

Multipleunitsnormallyhavecompletelyindependentbrakingsystemsonallcars,meaningthefailureofthebrakesononecardoesnotpreventthebrakesthroughoutthetrainfromoperatingsafely.

Locomotiveclassifications

Motivepower

Locomotivesmaygeneratetheirpowerfromfuel（wood,coal,petroleumornaturalgas）,ortheymaytakepowerfromanoutsidesourceofelectricity.Itiscommontoclassifylocomotivesbytheirsourceofenergy.Thecommononesinclude:

Steam

Inthe19thcenturythefirstrailwaylocomotiveswerepoweredbysteam,usuallygeneratedbyburningcoal.Becausesteamlocomotivesincludedoneormoresteamengines,theyaresometimesreferredtoas"steamengines".ThesteamlocomotiveremainedbyfarthemostcommontypeoflocomotiveuntilafterWorldWarII.[6]

ThefirststeamlocomotivewasbuiltbyRichardTrevithick;itfirstranon21February1804,althoughitwassomeyearsbeforesteamlocomotivedesignbecameeconomicallypractical.[2].ThefirstcommercialuseofasteamlocomotivewasTheSalamancaonthenarrowgaugeMiddletonRailwayinLeedsin1812.ThelocomotiveFairyQueen,builtin1855runsbetweenDelhiandAlwarinIndiaandistheoldeststeamlocomotiveinregular（albeittourist-only）serviceintheworld,andtheoldeststeamlocomotiveoperatingonamainline.[7][8]

Theall-timespeedrecordforsteamtrainsisheldbyanLNERClassA44-6-2PacificlocomotiveoftheLNERintheUnitedKingdom,number4468Mallard,whichpullingsixcarriages（plusadynamometercar）reached126 mph（203 km/h）onaslightdownhillgradientdownStokeBankon3July1938.[9]AerodynamicpassengerlocomotivesinGermanyattainedspeedsveryclosetothisandduetothedifficultiesofadequatelybalancingandlubricatingtherunninggear,thisisgenerallythoughttobeclosetothepracticablelimitforadirect-coupledsteamlocomotive.[10]

Beforethemiddleofthe20thcentury,electricanddiesel-electriclocomotivesbeganreplacingsteamlocomotives.Steamlocomotivesarelessefficientthantheirmoremoderndieselandelectriccounterpartsandrequiremuchgreatermanpowertooperateandservice.[11]BritishRailfiguresshowedthecostofcrewingandfuellingasteamlocomotivewassometwoandahalftimesthatofdieselpower,andthedailymileageachievablewasfarlower.Aslabourcostsrose,particularlyafterthesecondworldwar,non-steamtechnologiesbecamemuchmorecost-efficient.[citationneeded]Bytheendofthe1960s-1970s,mostwesterncountrieshadcompletelyreplacedsteamlocomotivesinpassengerservice.Freightlocomotivesgenerallywerereplacedlater.Otherdesigns,suchaslocomotivespoweredbygasturbines,havebeenexperimentedwith,buthaveseenlittleuse,mainlyduetohighfuelcosts.

Bytheendofthe20thcentury,almosttheonlysteampowerstillinregularuseinNorthAmericaandWesternEuropeancountrieswasonheritagerailwayslargelyaimedattouristsand/orrailroadhobbyists,knownas'railfans'or'rai