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Thomas Carolus Fans Aerodynamic Design - Noise Reduction - Optimization Fans Thomas Carolus Fans Aerodynamic Design - Noise Reduction - Optimization ThomasCarolus (emeritus) AppliedFluidMechanicsand Turbomachinery InstituteforFluid-andThermodynamics UniversitySiegen Siegen,Germany ISBN978-3-658-37958-2 ISBN978-3-658-37959-9 (eBook) https://doi.org/10.1007/978-3-658-37959-9 Thetranslationwasdonewiththehelpofartificialintelligence(machinetranslationbytheserviceDeepL.com). Asubsequenthumanrevisionwasdoneprimarilyintermsofcontent. #SpringerFachmedienWiesbadenGmbH,partofSpringerNature2022 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartofthematerial is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproductiononmicrofilmsorinanyotherphysicalway,andtransmissionorinformationstorageandretrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. Theuseofgeneraldescriptivenames,registerednames,trademarks,servicemarks,etc.inthispublicationdoesnot imply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevantprotectivelaws andregulationsandthereforefreeforgeneraluse. Thepublisher,theauthors,andtheeditorsaresafetoassumethattheadviceandinformationinthisbookare believedtobetrueandaccurateatthedateofpublication.Neitherthepublishernortheauthorsortheeditorsgivea warranty,expressedorimplied,withrespecttothematerialcontainedhereinorforanyerrorsoromissionsthat mayhavebeenmade.Thepublisherremainsneutralwithregardtojurisdictionalclaimsinpublishedmapsand institutionalaffiliations. ThisSpringerViewegimprintispublishedbytheregisteredcompanySpringerFachmedienWiesbadenGmbH, partofSpringerNature. Theregisteredcompanyaddressis:Abraham-Lincoln-Str.46,65189Wiesbaden,Germany Preface The number of air and gas transporting machines in use today is uncountable. These machines enable key areas of our daily lives by providing air for heating and cooling, deliveringgasesinchemicalplantsandfoodprocessing,assistingingeneratingelectricity, propellingairplanes,andmanymore.Thisbookdealswithindustrialfans,thatis,withall typeoffanswiththeexceptionofthoseforaircraftengines. Inarecentarticle,S.Castegnaro(seethebibliographyattheendofChap.4)pointedout howtheaerodynamicdesignmethodsforfansdevelopedhistorically:Beforethebeginning of the twentieth century, only empirical knowledge was available. Then, mathematical- physicalanalyticaltheoriesbecameincreasinglyestablished.Theyarestillinusetodayin ever more refined variants. The development of the modern computer from the 1950s onwards,however,madeitpossibletosolvethefundamentalequationsoffluidmechanics with increasingly less simplifications. The key word is “computational fluid dynamics (CFD)”. Thus, numerical flow simulation has become the third pillar of fluid mechanics, together with the established experimental and analytical methods. Nowadays, CFD is oftenusedtopredicttheaerodynamicoperatingbehaviourofanewfanbeforeamodelor prototypeisevenbuilt.Alargenumberofdesignvariantscanbesimulated.Thispavesthe way for a real aerodynamic optimization, for instance of efficiency or fan power density. Optimizationmayyieldmorecomplexshapesthantheclassicdesignmethods,butmodern compositematerialsandadditivemanufacturingprocessesincreasinglycancopewiththat. Theaeroacousticsofturbomachineryingeneralisstillatopicofstrongcurrentresearch interest. While aerodynamic design methods can be considered proven and mature, the “acoustic design” of fans is much more challenging. Accurate fan noise prediction is difficult but essential for designing low noise fans. In addition to the mere mitigation of flow-inducedfannoise,theminimization ofannoyanceduetounavoidable fannoise and hencepsychoacousticsmetricsincreasinglybecomethefocusofattention. Thebookisarrangedinthreemajorsections.Thefirst(Chaps.1,2,3,and4)provides the selection of a fan for a given duty in a plant as well as classic aerodynamic design methodsforcentrifugalandaxialfans.Thesecond(Chaps.5,6,7,and8)focusesonfan noise,especiallyonitsgenerationandpropagation,onitsprediction,andonitsmitigation v vi Preface by special design features. The last section (Chap. 9) provides an introduction into experimentalandnumericalmethodsincludingoptimization. The German editions of this book have served as an educational text, but also as a professionalreferenceforengineerswhoareconcernedwiththedesignandapplicationof industrial fans. Many international readers and the publisher encouraged me to bring out thisfirstEnglishtranslationofthefourthGermanedition. Acknowledgements Many individuals and organizations have assisted me in working on this and the past editionsofthisbook.IamespeciallygratefultoallmyformerresearchassistantsandPh.D. students who were involved in turbomachinery research in my team: Dipl.-Ing. Bernd Homrighausen, Dr.-Ing. Michael Beiler, Dr.-Ing. Thomas Fuest, Dr.-Ing. Bernhard Schulze-Dieckhoff, Dr.-Ing. Robert. Basile. Dr.-Ing. Michael Stremel, Dr.-Ing. Marc Schneider,Dr.-Ing.HaukeReese,Dr.-Ing.JulianWinkler,Dr.-Ing.DanielWolfram,Dr.- Ing. Michael Kohlhaas, Dr.-Ing. Stephan Pitsch, Dr.-Ing. Tom Gerhard, Dr.-Ing. Michal Sturm,Dr.-Ing.KonradBamberger,Dr.-Ing.SebastianKnirsch,Dr.-Ing.RalfStarzmann, Dr.-Ing. Christoph Moisel, Dr.-Ing. Tao Zhu, Dr.-Ing. Nico Kaufmann, Dr.-Ing. Kevin Volkmer, Dr.-Ing. Farhan Manegar, Dr.-Ing. Carolin Feldmann, Dr.-Ing. Leonard MackowskiandM.Sc.KathrinStahl.Theircontributionsanddiscussionswereindispens- able. In addition, I appreciate very much the early technical discussions with Dr.-Ing. J.Frankefromtheformer flowsimulationgroup attheUniversity SiegenandDr.-Ing. Ş. Çağlar from the Karlsruhe Institute of Technology. Prof. Dr.-Ing. P. Pelz from the Technical University Darmstadt contributed to the section on efficiency upgrading. The sectiononthepsychoacousticevaluationoffannoisewaswrittenwiththespecialcollabo- rationofDr.rer.nat.S.TöpkenfromtheCarlvonOssietzkyUniversityOldenburgandDr.- Ing.CarolinFeldmann.Dr.-Ing.KonradBambergerwasthemainauthorofthesectionon optimization.Mybasicknowledgeforthistextbook,however,isowedtomyownformer professors Dr.-Ing. H. Marcinowski, Dr.-Ing. Dr. techn. E.h. J. Zierep and Dr.-Ing. Dr. h.c. K.-O. Felsch during my time as a student at the Technische Hochschule Karlsruhe (now Karlsruhe Institute of Technology, KIT), Germany, as well as to Prof. AllanPierce,Ph.D.,whosestudentIhadtheprivilegeofbeingattheGeorgiaInstituteof TechnologyinAtlanta,USA. I am indebted also to many individual companies in the fan industries that have supported my research for nearly 40 years. Many challenging projects were initiated by theGermanForschungsvereinigungfürLuft-undTrocknungstechnik(FLT)e.V.(German Research Association for Air and Drying Technology) which connects industrial to academicresearchinanexcellentmanner. vii viii Acknowledgements TheFulbrightCommissionsupportedmytworesearchsabbaticalsintheDepartmentof AerospaceEngineeringatthePennsylvaniaStateUniversityinStateCollege,USA,which contributedtotheprogressofthebooktremendously. I want to thank the Department of Mechanical Engineering at the University Siegen, Germany, for providing me and my team with a laboratory and computer facilities for nearly30years. Specialthanks toallreaders ofthefirst threeeditions whogaveconstructive feedback andsuggestedadditionsandextensions. Finally,mygreat (literally andfiguratively)family hassupportedmeovermanyyears when I disappeared behind my desk or in the laboratory. I am most grateful for their understandingandcontinuousencouragement. Contents 1 Basics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 FanPerformanceParameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 SelectionoftheFan:DemandofthePlant. . . . . . . . . . . . . . . . . . . . 3 1.3 AerodynamicPerformanceCharacteristics. . . . . . . . . . . . . . . . . . . . 4 1.4 Non-dimensionalParameters,ModelLaws,TypesofFans. . . . . . . . 5 1.4.1 Non-dimensionalParameters. . . . . . . . . . . . . . . . . . . . . . . 5 1.4.2 ModelLaws. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.4.3 Scale-UpMethods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.4.4 SystematicsofFanTypes:TheCordier-Diagram. . . . . . . . . 9 1.5 PracticeProblems. . . . . .. . . . . . .. . . . . . .. . . . . .. . . . . . .. . . . . 11 1.5.1 PressureRiseRequirementofaPlantandFan Specification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.5.2 SelectionoftheTypeofFan. . . . . . . . . . . . . . . . . . . . . . . 12 1.5.3 FromModel-toFull-Scale. . . . . . . . . . . . . . . . . . . . . . . . . 12 References. . . . . .. . . . . . .. . . . . .. . . . . .. . . . . .. . . . . . .. . . . . .. . . . . 12 2 BladePerformanceParameters,CascadesofBlades,Kinematics, LossesandEfficiencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.1 BladeWork,BladeVolumeFlowRate. . . . . . . . . . . . . . . . . . . . . . 15 2.2 FlowKinematics(VelocityTriangles). . . . . . . . . . . . . . . . . . . . . . . 16 2.2.1 CascadeofRadialBlades. . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.2.2 CascadeofAxialBlades. . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.3 LossesandEfficiencies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.3.1 LossesintheImpellerandEfficiencies. . . . . . . . . . . . . . . . 21 2.3.2 LossesintheCasingandGuideVanes,Efficiencies. . . . . . . 23 References. . . . . .. . . . . . .. . . . . .. . . . . .. . . . . .. . . . . . .. . . . . .. . . . . 26 3 DesignofCentrifugalFans. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.1 BladeDesign. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.1.1 SlipofFlow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 ix x Contents 3.1.2 TheSlipFactor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 3.1.3 SelectionoftheNumberofBlades. . . . . . . . . . . . . . . . . . . 34 3.1.4 BlockageoftheInletandOutletDuetotheFinite ThicknessoftheBlade.. . . .. . . .. . . .. . . .. . . .. . . .. . . 35 3.1.5 Summary:BladeDesignforCentrifugalImpellers. . . . . . . . 38 3.1.6 FurtherEmpiricalGeometryParametersofthe CentrifugalImpeller. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 3.2 LayoutofaVoluteCasing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 3.2.1 One-DimensionalStreamlineTheory. . . . . . . . . . . . . . . . . 45 3.2.2 FurtherEmpiricalGeometricalParametersoftheSimple VoluteCasing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.3 PracticeProblems. . . . . .. . . . . . .. . . . . . .. . . . . .. . . . . . .. . . . . 48 3.3.1 DesignofaCentrifugalFanImpeller. . . . . . . . . . . . . . . . . 48 3.3.2 DesignofaVolute. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 References. . . . . .. . . . . . .. . . . . .. . . . . .. . . . . .. . . . . . .. . . . . .. . . . . 49 4 DesignofAxialFans. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 4.1 FlowKinematicsintheAxialImpeller:RadialEquilibrium. . . . . . . . 52 4.1.1 IsoenergeticLoadingDistribution. . . . . . . . . . . . . . . . . . . . 55 4.1.2 Radius-DependentLoadingDistribution. . . . . . . . . . . . . . . 58 4.1.3 SummaryofSwirlDistributions. . . . . . . . . . . . . . . . . . . . . 60 4.2 Segmentation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 4.3 TheBladeElementMomentum(BEM)MethodforLow-Pressure AxialFans. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4.3.1 DerivationoftheKeyEquation. . . . . . . . . . . . . . . . . . . . . 62 4.3.2 Summary:BladeDesignforLow-SolidityAxialImpellers withtheBEMMethod. . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4.3.3 BladeSkew. . . . .. . . .. . . . .. . . .. . . . .. . . .. . . . .. . . . 68 4.4 TheLiebleinMethodforHigh-PressureAxialFans. . . . . . . . . . . . . 70 4.4.1 BladeElementInletAngle. . . . . . . . . . . . . . . . . . . . . . . . . 71 4.4.2 BladeExitAngle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 4.4.3 CamberandMeanLine. . . . . . . . . . . . . . . . . . . . . . . . . . . 73 4.4.4 Summary:BladeDesignforHigh-SolidityAxial Impellers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 4.5 DesignCriteria. .. . . . . .. . . . .. . . . . .. . . . .. . . . . .. . . . .. . . . . 75 4.5.1 DeHaller-Criterion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 4.5.2 CriterionofStrscheletzky. . . . . . . . . . . . . . . . . . . . . . . . . . 75 4.5.3 DiffusionCoefficientAccordingtoLieblein. . . . . . . . . . . . 77 4.5.4 FurtherLimitations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 4.6 PracticeProblems. . . . . .. . . . . . .. . . . . . .. . . . . .. . . . . . .. . . . . 78 4.6.1 DesignofaLow-PressureAxialFan. . . . . . . . . . . . . . . . . . 78