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ID:34294225
大小:687.00 KB
页数:9页
时间:2019-03-04
《salford-ventilation-noisedoc索尔福德noisedoc通风》由会员上传分享,免费在线阅读,更多相关内容在应用文档-天天文库。
1、NOISEINVENTILATIONDUCTSSoundinductsTheprimarysourceofnoiseisthefan.Itwillradiatetonalsoundatfrequenciesrelatedtothemotor,rotational,frequencyandthebladefrequency.Itwillalsoradiatebroadbandsoundduetoanyturbulentairflowofftheblades.Thesoundpowerisconstrainedwithintheduc
2、ting.Thesoundpowerpropagatingalongtheductwillreduceonlywhereenergyhasbeen:·absorbedbytheductwalls(andpossiblythenradiatedoutsidetheduct)·reflectedbackuptheductbyasharpbend·dividedbetweenductswherebranchesdiverge·reflectedbackuptheductduetochangesinthecross-sectionalar
3、eaoftheductInthesimplestpossiblecaseofalongstraightductwithveryrigidwalls,thepowerwillbethesameatallpointsalongtheduct.FanNoiseNoiseenergygeneratedbythefanrotationisdependentonthediameterandtherotationalspeedofthefan,typicallyproportionaltothefifthorsixthpowerofthelin
4、earvelocityatthetipofthefanblades.Generallyalargediameterfanatlowrotationalspeedproduceslowfrequencyandcomparativelylownoiselevel.Thesamevolumeflowratecanbeachievedbyincreasingtherotationalspeedandreducingthediameter.Inthiscasethefrequencyandthelevelofthenoisearehighe
5、rbutthehigherfrequencynoisecanbemoreeffectivelyattenuatedbyliningtheductwithsoundabsorbingmaterials.IngeneraltheSWLoffansvariesgreatlywithtypes,sizes,andspeeds.Itshouldbechosencarefullytoensurelownoiselevels.Manufacturer’sdataonthesourceSWLofafanshouldalwaysbesought.F
6、lowgeneratednoise:·Inemptystraightductsnoisefromturbulenceisgenerallyverysmallcomparedwithotherfactors,especiallywithvelocty,u<10m/s.·Bends,Branches,JunctionsandTurnscauseabruptchangesinflowconditions.Noiselevelincreasesapproximately15(power%u5)to20(power%u7)dBperdoub
7、lingofflowspeeddependingheavilyontheductsizeandconfigurations.Noisecanbereducedbyroundingthebendsorintroducingstreamlinedturningvanes.·InteractionwithObstacles,e.g.silencersetccausesturbulencewakes.Noiselevelagaindependsapproximatelyonu5,andalsoonthesizeandgeometryoft
8、heobstacle.Shapesthatcreateabruptchangesintheflowarebesttobeavoided.·Inlet/OutletGrilles,(air)Diffusersanddampers.Similarnoi
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