Table Of ContentDissociation of noise sources for
aeronautical fans
Guillaume Renaud
KTH Aeronautical and Vehicle Engineering
This dissertation is submitted for the degree of
Master of Science in Engineering
KTH June 2017
Acknowledgements
Iwant tothank allthe peoplethatsupervised meduring mymaster thesis whichtook place
inexcellentconditionsandwithapleasantsocialclimate. Ithankparticularly:
• M. Patrice Caule who followed me for six months, for its receptiveness, his precious
knowledgeinacousticandhispedagogy.
• M.FlorentChallasandM.ThierryFontalbat,aerodynamicsengineers,fortheirrecep-
tivenessandtheirknowledgeinaerodynamics.
IthankalsoallthepeoplethatinterveneintheintegrationpaththatIfollowedinthebeginning
of mymaster thesis. Thispath enablesme to meetthe actorsworkingin variousdepartments
andtohaveaglobalvisionofthecompanyenablingmetoworkingoodconditions.
I finally thank my examinator Ciarán O’Reilly for offering me this opportunity and
offeringmethechancetodevelopmyknowledgeinacoustics.
Abstract
To ensure health and hearing comfort, acoustics becomes more and more essential in the
design offans. 3D numericalcalculations (mechanical, aerodynamicand magnetic) areused
to ensure the compliance of fans before production test prototypes. However, numerical
modellingislongandcostlytothecompany; theuseofanalyticalsoftwarecalculationsisan
alternativefordesigners. Ananalyticalchainallowslessprecisebutwayfastercalculations
enabling to link earlier in the design, the aerodynamic, mechanical and magnetic with the
acousticpart.
Themaster thesisis splitin twosteps. First,the reliabilitybetweenthe aerodynamicand
the acoustic datais enhanced for abetter estimation of theaerodynamic noise. Thisis done
byusinganextractiontooloftheaerodynamicandgeometricdata,inputsofananalytical
softwareOPTIBRUIthatestimatestheaeroacousticnoise. Anautomaticchainonasetof
Technofan fansis alsoused in orderto validate andoptimize theOPTIBRUIconfiguration in
relationtotestmeasurements. Inadditiontothisanalyticalchain,linksbetweenCFDdataand
measurementshavebeencreated. Theselinksareusedtocomparethedatafromanalytical
and numerical calculations with the measurements in order to establish the suitability of
theresults. Theresultsobtainedareveryencouragingastheypredictthenoiselevelwithin
3dB. The master thesis ends with the dissociation of the three noise sources occurring in
fans(aerodynamic,mechanicalandmagnetic)knowingthecharacteristicfrequenciesofthe
mechanicalandmagneticnoisemechanisms. Withthisdissociation,itispossibletoknow
rapidly from measurements the parts of the fan that are noise dominant and to guide the
working times on the jobs treating the zones where the noise is predominant (aerodynamic
engineer,electricmotorengineerormechanicalengineer).
Table of contents
Listoffigures xi
Listoftables xv
1 Introductionandobjectives 1
1.1 Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Theoreticalbackground 7
2.1 Generalpointsonfan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.1 Architectureandfunctioning . . . . . . . . . . . . . . . . . . . . . 7
2.1.2 Typesoffan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1.3 Fanaerodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.4 Electricmotors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2 Fannoise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2.1 Typesofsources . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2.2 Aerodynamicnoisesources . . . . . . . . . . . . . . . . . . . . . 12
2.2.3 Mechanicalnoisesources . . . . . . . . . . . . . . . . . . . . . . 16
2.2.4 Magneticnoisesources . . . . . . . . . . . . . . . . . . . . . . . . 16
2.2.5 Summaryofthenoisesourcemechanisms . . . . . . . . . . . . . . 18
3 ExtractionoftheCFDdata 21
3.1 Extractionofthegeometry . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.2 Extractionoftheaerodynamicdata . . . . . . . . . . . . . . . . . . . . . . 23
3.3 Wakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.4 Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
viii Tableofcontents
4 DescriptionofOPTIBRUI 27
4.1 Presentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.2 Modelsused . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.2.1 Tonalnoisewithin-ductpropagation . . . . . . . . . . . . . . . . . 28
4.2.2 Broadbandnoisewithfree-fieldpropagation . . . . . . . . . . . . . 31
5 Validationofthemodels 35
5.1 Automaton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.2 Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.3 Modelscomparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
6 Dissociationofthethreenoisesources 41
6.1 Characteristicfrequenciesofmechanicalsources . . . . . . . . . . . . . . 41
6.2 Characteristicfrequenciesofmagneticsources . . . . . . . . . . . . . . . . 42
6.2.1 Permeance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
6.2.2 Magnetomotiveforce . . . . . . . . . . . . . . . . . . . . . . . . . 44
6.2.3 Resonances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
6.3 Sourcesdetectionmethod . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
6.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
6.5 Classificationoffans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
6.6 Futurework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
7 Conclusion 55
References 57
AppendixA Magneticnoisefrequencies 61
AppendixB Modelcomparisonmodels 65
B.1 Distortionnoise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
B.2 Wakenoise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
B.3 Trailingedgenoise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
B.4 AntaresvsNUMECAextractions . . . . . . . . . . . . . . . . . . . . . . 68
AppendixC ComparisonofOPTIBRUIandtestspectra 71
Tableofcontents ix
AppendixD OPTIBRUI,automatoninterfaceandtestfacilities 81
D.1 OPTIBRUI,automatoninterfaces . . . . . . . . . . . . . . . . . . . . . . . 81
D.2 Testfacilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
Description:Theoretical background. Fig. 2.4 Velocity triangles of an axial compressor stage. The figure above presents the velocity triangles used in the aerodynamic pre design of fans. The impeller or rotor is in rotation at the angular velocity ω in rad/s and the rotation speed is noted ⃗U. Knowing the r
