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1、外文文献IntakeandExhaustTunedintakemanifoldFirstintroducedbyMercedes300SLin1954,tunedintakemanifoldisnotexactlyanewtechnology.Itisdiscussedherejustbecauseitsprincipleisusefultoourfurtherstudyofvariableintakemanifold.Before1950s,engineersbelievedshortintakem
2、anifoldswerethebesttoenginebreathing.Thentheydiscoveredthatundersomeconditionslongintakemanifoldscouldactuallyimproveoutput,thankstoaso-called"superchargingeffect11.Howisthatdone?Let'sseethefollowingillustration:Whenfreshairissuckedintocombustionchamber
3、;itgathersspeedandmomentumintheintakeman讦old.Assoonastheinletvalveisclosed,thefast-movingairhitsthevalveandcompresses,generatinghighpressure・Withnowheretogo,thishighpressurebouncesback,travelsalongtheintakemanifold,hitstheplenumattheothersideandbouncesb
4、ackagain.Inthisway,thehighpressurebouncesbackandforthalongtheintakemardfolduntiltheinletvalveopensagain,creatingpressurewaves.Nowtheinterestingthingis:iftheinletvalveopensagainexactlywhenthepressurewavecomesback,thepressurewavewillhelpchargingthecombust
5、ionchamberduetoitshighpressure・Thisisnotunlikechargingthecombustionchamberwithalightsupercharger;thuswecallthissuperchargingeffect・Inordertomatchthetimingofvalveopening,thefrequencyofpressurewaveshallsynchronizewithenginerev,obviously.Thisfrequencyisdep
6、endentonthelengthoftheintakemanifold(Linthefigure).TheIongerthelength,thelongerthetimepressurewavetakestobouncebackthusthelowerfrequencyofpressurewaveisattained.Asaresult,aIongerintakemanifoldleadstosuperchargingeffectatlowerenginerev.Ashortermanifoldle
7、adstosuperchargingeffectathigherrev.Byselectingasuitablemanifoldlength,wecanobtainthedesiredpowercharacteristic.Calculationsfoundinordertoachieveusefulsuperchargingeffect,theintakemanifoldshallbeunusuallylong・Ifitistooshort,thepressurewavewillbounceback
8、andforthtoomanytimesinthemanifoldbeforethevalveopensagain,bythenthehighpressureislargelydiminished・Thereforeatunedintakemanifoldshallbelong.Unfortunately,tunedintakemanifoldworksonlyacrossanarrowrevband.Iftheenginerevsbeyondthatb
