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Design & Performance
Mixed Flow: Axial/Centrifugal Hybrid
Amixedflowwheelisahybridbetweenanaxialpropelleranda
centrifugalwheel.Theresultisadesignthatcombinesthebestaxial
andcentrifugalproperties:highlyefficientairmovement,increased
pressurecapabilities,extremelylowsoundlevels,andasteepfan
performancecurve.Tofurtherenhancethefan’sperformance,
straighteningvanesareincorporatedinthehousing.Theseserve
toconvertswirlingairflowintoastraightaxialflowwitharesulting
staticpressureriseandenergysavings.
60
70
80
90
100
62 125 250 500 1000 2000 4000 8000
Frequency, Hz
Sound Power, dB
30
40
50
60
70
80
14000 16000 18000 20000 22000 24000
CFM
SE
QEI
Typical Vane Axial
Typical Centrifugal
QEI-L, QEI-I/II
Typical Vane Axial
Typical Tubular Centrifugal
Typical Typical QEI-L
Tubular Centrifugal Vane Axial QEI-I/II
Sound power levels shown at each frequency:
Static Pressure
CFM
Centrifugal
Mixed Flow
Axial
Lower Sound Power, Better Sound Quality
Thesoundqualityofthebelt-drivenmixedflowfanlineis
asbeneficialtolowsounddesignasisthereducedoverall
soundpower.Thesoundchartcomparesunitsofsimilar
outertubediametersatanoperatingpointof20,000cfmwith
1.5incheswgofstaticpressure(Ps).Tubularcentrifugals
(green)havedominanttonesinthe63Hzthrough250Hz
octavebands,whilevaneaxials(red)havemoremidtohigh
frequencysound.Themixedflowfan(blue)doesnothavea
dominanttone.Abystanderwouldhearamoreblandsound
thatisquieterthanatubularcentrifugalorvaneaxial.
Sound and Efficiency
Soundpowerlevelsandfanefficiencyaretwoveryimportantfactorswhenselectingafan.Thereisanoticeable
differencebetweenimpellertypes.Thetableandchartbelowcomparethesoundpower(L
w
A)andthestatic
efficiencyofthebelt-drivenmixedflowfanwheelversustubularcentrifugalandvaneaxialinlinefans.Overa
widerangeofoperatingpoints,themixedflowfanprovidesthequietestandmostefficientselection.
Modelcomparisonsbasedonsimilaroutertubediameters.
Performance
Mixed Flow
Fan Size
Sound Power (L
w
A) Static Efficiency
MixedFlow
(QEI-L,QEI-I/II)
Inline
Centrifugal
VaneAxial
MixedFlow
(QEI-L,QEI-I/II)
Inline
Centrifugal
VaneAxial
15,000cfm
@1.0in.wg
24 90dB 100dB 103dB 43% 17% 34%
25,000cfm
@2.0in.wg
36 86dB 93dB 102dB 68% 45% 56%
50,000cfm
@4.0in.wg
49 92dB 98dB 111dB 71% 60% 59%
AxialFans:Straightthrough
nearlylinearairflow.
CentrifugalFans:Two90°
deflections,beforeairflow
exitsthefan.
MixedFlowFans:Slight
airflowdeflectionfrom
straightthrough.
Airflow Profiles
Axial Centrifugal Mixed Flow