电站风机培训-基本概念

BasicConceptsClientname&titleCompanyNameDateFans-BasicConceptsAfanisusedtomovegaswhereasacompressorismoreconcernedwithincreasingthepressureofthegas.Arotatingmachinethatcontinuouslyprovidesaflowofgas(includingair)againstaresistancePerformanceCurveFanLawsQD3NPD2N2WD5N3Lw70logD+50logN+20logSpecificSpeedSpecificspeedisthespeedatwhichafanofindeterminatediameterwillrunattoproduceunitflowatunitpressure.Ns=Q0.5NP0.75Actualvalue(RPM)dependsonunitsusedSpecificSpeedChartFlowPressureHighLowNs=Q0.5NP0.75CaptionstobesetinArialBold12pt.Anothercolourcanbeintroducedtohighlighttheinformation.CaptionstobesetinArialBold12pt.Anothercolourcanbeintroducedtohighlighttheinformation.CaptionstobesetinArialBold12ptImpellerShapeMajorFanClassificationsCentrifugalFanImpellerAxialFlowFansMixedFlowCentrifugal-SingleInletCentrifugalFan-DoubleInletCentrifugalFan-TwoStageCentrifugalFanInletControlAxialFanArrangementsAxialFans-AutovariablePitchSpeedControlVariableSpeedCouplingVariableSpeedMotorComparisonofControlMethodsAbsorbedPowerVsLoadforVariousFanTpes02040608010012014016018035405060708090100110120%LoadMCR%AbsorbedPowerConstantSpeedCentrifugalTwoSpeedCentrifugalConstantSopeedAxialVariableSpeedCentrifugalParallelOperationParallelOperationParellelOperationFanPressureFanpressureisthedifferencebetweentotalpressureatthefanoutletandtotalpressureatthefaninlet.Pf=Pto-PtiPtiPtoTotalpressureisthesumofthestaticandvelocitypressuresatagivenpointFanStaticPressureFanstaticpressureisthedifferencebetweenstaticpressureatthefanoutletandtotalpressureatthefaninlet.Pf=Pso-PtiPtiPsoStaticPressureRiseStaticpressureriseisthedifferencebetweenstaticpressureatthefanoutletandstaticpressureatthefaninlet.Ps=Pso-PsiPsiPsoFanSelectionForthesamefan-staticpressureriseisnumericallylargerthanfanstaticpressureTherefore,iffanstaticpressureisspecified,andthefanisselectedassumingthatthisisstaticpressure,risethenthefanwillbetoosmall.SmallInletBoxesPtiPsoSmallerinletboxStaticpressurefallsVelocitypressurerisesTotalpressureisconstantSelectonthebasisofstaticpressureriseLowerstaticpressureatfanoutletSelectonthebasisoffanstaticpressureRequiredstaticpressureatfanoutletAdiabaticCompressionkp=(rx-1)wherex=-1x(r-1)Power=PQkpFanEfficiencyFanstaticefficiencys=PsfQkp=80.5%WFantotalefficiencyt=dPtfQkp=83.2%W'Static'efficiencys=dPsfQkp=84.6%W'Static'efficiencys=PsfQ=82.2%W'Total'efficiencyt=PtfQ=84.9%W'Static'efficiencys=dPsfQ=86.3%WSystemEffectsQuestions