Fluid Mechanics and Thermodynamics of Turbomachinery Seventh Edition Fluid Mechanics and Thermodynamics of Turbomachinery Seventh Edition S. L. Dixon, B. Eng., Ph.D. Honorary Senior Fellow, Department of Engineering, University of Liverpool, UK C. A. Hall, Ph.D. University Senior Lecturer in Turbomachinery, University of Cambridge, UK AMSTERDAM(cid:129)BOSTON(cid:129)HEIDELBERG(cid:129)LONDON(cid:129)NEWYORK(cid:129)OXFORD(cid:129)PARIS SANDIEGO(cid:129)SANFRANCISCO(cid:129)SINGAPORE(cid:129)SYDNEY(cid:129)TOKYO Butterworth-HeinemannisanimprintofElsevier Butterworth-HeinemannisanimprintofElsevier TheBoulevard,LangfordLane,Kidlington,Oxford,OX51GB,UK 225WymanStreet,Waltham,MA02451,USA FirstpublishedbyPergamonPressLtd.1966 Secondedition1975 Thirdedition1978 Reprinted1979,1982(twice),1984,1986,1989,1992,1995 Fourthedition1998 Fifthedition2005(twice) Sixthedition2010 Seventhedition2014 Copyrightr2014S.L.DixonandC.A.Hall.PublishedbyElsevierInc.Allrightsreserved Nopartofthispublicationmaybereproducedortransmittedinanyformorbyanymeans,electronicormechanical, includingphotocopying,recording,oranyinformationstorageandretrievalsystem,withoutpermissioninwritingfrom thepublisher.Detailsonhowtoseekpermission,furtherinformationaboutthePublisher’spermissionspoliciesandour arrangementswithorganizationssuchastheCopyrightClearanceCenterandtheCopyrightLicensingAgency,canbe foundatourWebsite:www.elsevier.com/permissions ThisbookandtheindividualcontributionscontainedinitareprotectedundercopyrightbythePublisher(otherthanas maybenotedherein). 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LibraryofCongressCataloging-in-PublicationData AcatalogrecordforthisbookisavailablefromtheLibraryofcongress BritishLibraryCataloguing-in-PublicationData AcataloguerecordforthisbookisavailablefromtheBritishLibrary ISBN:978-0-12-415954-9 ForinformationonallButterworth-Heinemannpublications visitourWebsiteatwww.elsevierdirect.com TypesetbyMPSLimited,Chennai,India www.adi-mps.com PrintedintheUS 14 15 16 17 18 10 9 8 7 6 5 4 3 2 1 Dedication In memory of Avril (22years)andbaby Paul. Preface to the Seventh Edition This book was originally conceived as a text for students in their final year reading for an honors degree in engineering that included turbomachinery as a main subject. It was also found to be a useful support for students embarking on postgraduate courses at masters level. The book was writ- ten for engineers rather than for mathematicians, although some knowledge of mathematics will prove most useful. Also, it is assumed from the start that readers will have completed preliminary courses in fluid mechanics. The stress is placed on the actual physics of the flows and the use of specialized mathematical methods is kept toa minimum. Compared to the sixth edition, this new edition has had a large number of changes made in terms of presentation of ideas, new material, and additional examples. In Chapter 1, following the definition of a turbomachine, the fundamental laws of flow continuity, the energy and entropy equations are introduced as well as the all-important Euler work equation. In addition, the proper- ties of working fluids other than perfect gases are covered and a steam chart is included in the appendices. In Chapter 2, the main emphasis is given to the application of the “similarity laws,” to dimensional analysis of all types of turbomachine and their performance characteristics. Additional types of turbomachine are considered and examples of high-speed characteristics are presented. The important ideas of specific speed and specific diameter emerge from these concepts and their application is illustrated in the Cordier Diagram, which shows how to select the machine that will give the highest efficiency for a given duty. Also, in this chapter the basics of cavitation are exam- ined for pumps andhydraulic turbines. The measurement and understanding of cascade aerodynamics is the basis of modern axial tur- bomachine design and analysis. In Chapter 3, the subject of cascade aerodynamics is presented in preparation for the following chapters on axial turbines and compressors. This chapter was completely reorganized in the previous edition. In this edition, further emphasis is given to com- pressible flow and on understanding the physics that constrain the design of turbomachine blades and determine cascade performance. In addition, a completely new section on computational meth- ods for cascade design and analysis has been added, which presents the details of different numeri- cal approaches and their capabilities. Chapters 4 and 5 cover axial turbines and axial compressors, respectively. In Chapter 4, new material has been added to give better coverage of steam turbines. Sections explaining the numer- ous sources of loss within a turbine have been added and the relationships between loss and effi- ciency are further detailed. The examples and end-of-chapter problems have also been updated. Within this chapter, the merits of different styles of turbine design are considered including the implications for mechanical design such as centrifugal stress levels and cooling in high-speed and high temperature turbines. Through the use of some relatively simple correlations, the trends in tur- bine efficiency with the main turbine parametersare presented. In Chapter 5, the analysis and preliminary design of all types of axial compressors are covered. Several new figures, examples, and end-of-chapter problems have been added. There is new cover- age of compressor loss sources and, in particular, shock wave losses within high-speed rotors are explored indetail. New material onoff-design operation and stage matching inmultistage compres- sors has been added, which enables the performance of large compressors to be quantified. xi xii Preface to the Seventh Edition Severalnewexamples andend-of-chapterproblems havealsobeenadded thatreflectthenewmate- rial on design,off-designoperation, andcompressible flow analysis ofhigh-speed compressors. Chapter 6 covers three-dimensional effects in axial turbomachinery and it possibly has the most new features relative to the sixth edition. There are extensive new sections on three-dimensional flows, three-dimensional design features, and three-dimensional computational methods. The sec- tion on through-flow methods has also been reworked and updated. Numerous explanatory figures have been added and there are new worked examples on vortex design and additional end- of-chapter problems. Radial turbomachinery remains hugely important for a vast number of applications, such as tur- bocharging for internal combustion engines, oil and gas transportation, and air liquefaction. As jet engine cores become more compact there is also the possibility of radial machines finding new uses within aerospace applications. The analysis and design principles for centrifugal compressors and radial inflow turbines are covered in Chapters 7 and 8. Improvements have been made relative to the fifth edition, including new examples, corrections to the material, and reorganization ofsome sections. Renewable energy topics were first added to the fourth edition of this book by way of the Wells turbineandanewchapteronhydraulicturbines.Inthefifthedition,anewchapteronwindturbines was added. Both of these chapters have been retained in this edition as the world remains increas- ingly concerned with the very major issues surrounding the use of various forms of energy. There is continuous pressure to obtain more power from renewable energy sources and hydroelectricity and wind power have a significant role to play. In this edition, hydraulic turbines are covered in Chapter 9, which includes coverage of the Wells turbine, a new section on tidal power generators, and several new example problems. Chapter 10 covers the essential fluid mechanics of wind tur- bines, together with numerous worked examples at various levels of difficulty. In this edition, the range of coverage of the wind itself has been increased in terms of probability theory. This allows forabetterunderstandingofhow muchenergyagivensizeofwindturbinecan capturefromanor- mally gusting wind. Instantaneous measurements of wind speeds made with anemometers are used to determine average velocities and the average wind power. Important aspects concerning the cri- teria of blade selection and blade manufacture, control methods for regulating power output and rotor speed, and performance testing are touched upon. Also included are some very brief notes concerning public and environmental issues, which are becoming increasingly important as they, ultimately, can affect the development ofwind turbines. To develop the understanding of students as they progress through the book, the expounded the- ories are illustrated by a selection of worked examples. As well as these examples, each chapter contains problems for solution, some easy, some hard. See what you make of them—answers are provided inAppendix F! Acknowledgments The authors are indebted to a large number of people in publishing, teaching, research, and manufacturing organizationsfor their help and support inthe preparationofthis volume. Inparticu- lar, thanks are given for the kind permission to use photographs and line diagrams appearing in this edition, aslisted below: ABB (BrownBoveri, Ltd.) American Wind Energy Association Bergey Windpower Company Dyson Ltd. Elsevier Science Hodder Education Institutionof Mechanical Engineers Kvaener Energy, Norway Marine CurrentTurbines Ltd., UK National Aeronautics and Space Administration (NASA) NREL Rolls-Royceplc TheRoyal Aeronautical Society and its Aeronautical Journal Siemens (Steam Division) SironaDental Sulzer Hydro of Zurich Sussex Steam Co., UK US Department ofEnergy Voith Hydro Inc., Pennsylvania TheWhittle Laboratory,Cambridge,UK I would like to give my belated thanks to the late Professor W.J. Kearton of the University of Liverpool and his influential book Steam Turbine Theory and Practice, who spent a great deal of timeandeffortteaching usaboutengineeringandinstilledinmeanincreasingandlife-longinterest in turbomachinery. This would not have been possible without the University of Liverpool’s award of the W.R. Pickup Foundation Scholarship supporting me as a university student, opening doors of opportunitythat changed mylife. Also, I give my most grateful thanks to Professor (now Sir) John H. Horlock for nurturing my interest in the wealth of mysteries concerning the flows through compressors and turbine blades during his tenure of the Harrison Chair of Mechanical Engineering at the University of Liverpool. At an early stage of the sixth edition some deep and helpful discussions of possible additions to the new edition took place with Emeritus Professor John P. Gostelow (a former undergraduate student of mine). There are also many members of staff in the Department of Mechanical Engineering dur- ing mycareer who helped andinstructed me for whichI am grateful. Also, I am most grateful for the help given to me by the staff of the Harold Cohen Library, University ofLiverpool, inmyfrequent searches for new materialneeded for the seventhedition. xiii xiv Acknowledgments Last, but by no means least, to my wife Rosaleen, whose patient support and occasional sugges- tions enabled me tofind the energyto complete thisnew edition. S.Larry Dixon I would like to thank the University of Cambridge, Department of Engineering, where I have been a student, researcher, and now lecturer. Many people there have contributed to my develop- ment as an academic and engineer. Of particular importance is Professor John Young who initiated my enthusiasm for thermofluids through his excellent teaching of the subject. I am also very grate- fultoRolls-Royceplc,whereIworkedforseveralyears.Ilearnedahugeamountaboutcompressor and turbine aerodynamics from my colleagues there and they continue to support me in my research activities. Almost all the contributions I made to this new edition were written in my office at King’s College, Cambridge, during a sabbatical. As well as providing accommodation and food, King’s is full of exceptional and friendly people who I would like to thank for their companionship and help during the preparation of thisbook. As a lecturer in turbomachinery, there is no better place to be based than the Whittle Laboratory. I would like to thank the members of the laboratory, past and present, for their support and all they have taught me. I would like to make a special mention of Dr. Tom Hynes, my Ph.D. supervisor, for encouraging my return to academia from industry and for handing over the teaching of a turbomachinery course to me when I started as a lecturer. During my time in the laboratory, Dr. Rob Miller has been a great friend and colleague and I would like to thank him for the sound advicehehasgivenonmanytechnical,professional,andpersonalmatters.Severallaboratorymem- bers have also helped inthe preparation of suitable figures for this book. These include Dr. Graham Pullan, Dr. Liping Xu, Dr Martin Goodhand, Vicente Jerez-Fidalgo, Ewan Gunn, and Peter O’Brien. Finally, special personal thanks go to my parents, Hazel and Alan, for all they have done for me. I would liketodedicate mywork on thisbookto mywife Gisella andmy sonSebastian. Cesare A. Hall List of Symbols A area a sonic velocity a;a0 axial-flow induction factor, tangentialflow induction factor b axial chord length, passage width, maximumcamber Cc,Cf chordwise and tangentialforcecoefficients CL,CD lift and drag coefficients CF capacity factor ð5P =P Þ W R C specific heat at constant pressure, pressure coefficient,pressure risecoefficient p C specific heat at constant volume v C ,C axial and tangential force coefficients X Y c absolutevelocity c spouting velocity o d internal diameter of pipe D drag force,diameter Dh hydraulicmeandiameter Ds specific diameter DF diffusion factor E,e energy, specificenergy F force, Prandtl correction factor Fc centrifugalforceinblade f friction factor, frequency, acceleration g gravitational acceleration H blade height, head HE effective head Hf head loss due tofriction HG gross head HS net positivesuction head (NPSH) h specific enthalpy I rothalpy i incidenceangle J wind turbine tip(cid:2)speed ratio j wind turbine local blade-speed ratio K,k constants L lift force, length ofdiffuserwall l blade chord length,pipe length M Mach number m mass, molecularmass N rotationalspeed, axial lengthofdiffuser n number ofstages, polytropic index o throat width P power xv xvi List of Symbols P rated powerof wind turbine R P average windturbine power W p pressure pa atmospheric pressure pv vapor pressure q quality ofsteam Q heat transfer, volume flowrate R reaction, specific gas constant, diffuser radius, stream tube radius Re Reynoldsnumber RH reheat factor R universalgas constant o r radius S entropy, power ratio s blade pitch, specificentropy T temperature t time, thickness U blade speed, internal energy u specific internal energy V,v volume, specificvolume W work transfer, diffuser width ΔW specific work transfer W shaft work x w relative velocity X axial force x,y dryness fraction, wetness fraction x,y,z Cartesian coordinate directions Y tangentialforce Y stagnation pressure loss coefficient p Z number ofblades,Zweifelblade loading coefficient α absoluteflow angle β relative flowangle, pitch angle ofblade Γ circulation γ ratio ofspecificheats δ deviation angle ε fluid deflectionangle, cooling effectiveness, drag(cid:2)lift ratio in wind turbines ζ enthalpyloss coefficient, incompressible stagnation pressure loss coefficient η efficiency θ blade camber angle,wakemomentum thickness, diffuser half angle κ angle subtended by logspiral vane λ profile loss coefficient,blade loading coefficient,incidencefactor μ dynamic viscosity ν kinematicviscosity,hub(cid:2)tip ratio, velocity ratio ξ blade stagger angle ρ density