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Jan 14, 2020
Fluid Mechanics, Thermodynamics of
Fifth Edition, in SI/Metric units
S. L. Dixon, B.Eng., Ph.D. Senior Fellow at the University of Liverpool
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First published by Pergamon Press Ltd. 1966 Second edition 1975 Third editon 1978 Reprinted 1979, 1982 (twice), 1984, 1986 1989, 1992, 1995 Fourth edition 1998
© S.L. Dixon 1978, 1998
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Library of Congress Cataloging-in-Publication Data Dixon, S. L. (Sydney Lawrence)
Fluid mechanics and thermodynamics of turbomachinery. p. cm.
Includes bibliographical references. 1. Turbomachines—Fluid dynamics. I. Title. TJ267.D5 2005 621.406—dc22
British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library.
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Preface to the Fifth Edition
In the earlier editions of this book, open turbomachines, categorised as wind turbines, propellers and unshrouded fans, were deliberately excluded because of the conceptual obstacle of precisely defining the mass flow that interacts with the blades. However, having studied and taught the topic of Wind Turbines for a number of years at the University of Liverpool, as part of a course on Renewable Energy, it became apparent this was really only a matter of approach. In this book a new chapter on wind turbines has been added, which deals with the basic aerodynamics of the wind turbine rotor. This chapter offers the student a short basic course dealing with the essen- tial fluid mechanics of the machine, together with numerous worked examples at various levels of difficulty. Important aspects concerning the criteria 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 impor- tant as they, ultimately, can affect the development of wind turbines. It is a matter of some regret that many aspects of the nature of the wind, e.g. methodology of deter- mining the average wind speed, frequency distribution, power law and the effect of elevation (and location), cannot be included, as constraints on book length have to be considered.
The world is becoming increasingly concerned with the very major issues sur- rounding the use of various forms of energy. The ever-growing demand for oil and the undeniably diminishing amount of oil available, global warming seemingly linked to increased levels of CO2 and the related threat of rising sea levels are just a few of these issues. Governments, scientific and engineering organisations as well as large (and small) businesses are now striving to change the profile of energy usage in many coun- tries throughout the world by helping to build or adopt renewable energy sources for their power or heating needs. Almost everywhere there is evidence of the large-scale construction of wind turbine farms and plans for even more. Many countries (the UK, Denmark, Holland, Germany, India, etc.) are aiming to have between 10 and 20% of their installed power generated from renewable energy sources by around 2010. The main burden for this shift is expected to come from wind power. It is hoped that this new chapter will instruct the students faced with the task of understanding the techni- calities and science of wind turbines.
Renewable energy topics were added to the fourth edition of this book by way of the Wells turbine and a new chapter on hydraulic turbines. Some of the derivatives of the Wells turbine have now been added to the chapters on axial flow and radial flow tur- bines. It is likely that some of these new developments will flourish and become a major source of renewable energy once sufficient investment is given to the research.
The opportunity has been taken to add some new information about the fluid mechanics of turbomachinery where appropriate as well as including various corrections to the fourth edition, in particular to the section on backswept vanes of centrifugal compressors.
xii Preface to the Fifth Edition
Preface to the Fourth Edition
It is now 20 years since the third edition of this book was published and in that period many advances have been made to the art and science of turbomachinery design. Knowledge of the flow processes within turbomachines has increased dramatically resulting in the appearance of new and innovative designs. Some of the long-standing, apparently intractable, problems such as surge and rotating stall have begun to yield to new methods of control. New types of flow machine have made their appearance (e.g. the Wells turbine and the axi-fuge compressor) and some changes have been made to established design procedures. Much attention is now being given to blade and flow passage design using computational fluid dynamics (CFD) and this must eventually bring forth further design and flow efficiency improvements. However, the fundamen- tals do not change and this book is still concerned with the basics of the subject as well as looking at new ideas.
The book was originally perceived as a text for students taking an Honours degree in engineering which included turbomachines as well as assisting those undertaking more advanced postgraduate courses in the subject. The book was written for engineers rather than mathematicians. Much stress is laid on physical concepts rather than math- ematics and the use of specialised mathematical techniques is mostly kept to a minimum. The book should continue to be of use to engineers in industry and techno- logical establishments, especially as brief reviews are included on many important aspects of turbomachinery giving pointers to more advanced sources of information. For those looking towards the wider reaches of the subject area some interesting reading is contained in the bibliography. It might be of interest to know that the third edition was published in four languages.
A fairly large number of additions and extensions have been included in the book from the new material mentioned as well as “tidying up” various sections no longer to my liking. Additions include some details of a new method of fan blade design, the determination of the design point efficiency of a turbine stage, sections on centrifugal stresses in turbine blades and blade cooling, control of flow instabilities in axial-flow compressors, design of the Wells turbine, consideration of rothalpy conservation in impellers (and rotors), defining and calculating the optimum efficiency of inward flow turbines and comparison with the nominal design. A number of extensions of existing topics have been included such as updating and extending the treatment and applica- tion of diffuser research, effect of prerotation of the flow in centrifugal compressors and the use of backward swept vanes on their performance, also changes in the design philosophy concerning the blading of axial-flow compressors. The original chapter on radial flow turbines has been split into two chapters; one dealing with radial gas tur- bines with some new extensions and the other on hydraulic turbines. In a world striv- ing for a “greener” future it was felt that there would now be more than just a little interest in hydraulic turbines. It is a subject that is usually included in many mechan-
ical engineering courses. This chapter includes a few new ideas which could be of some interest.
A large number of illustrative examples have been included in the text and many new problems have been added at the end of most chapters (answers are given at the end of the book)! It is planned to publish a new supplementary text called Solutions Manual, hopefully, shortly after this present text book is due to appear, giving the com- plete and detailed solutions of the unsolved problems.
S. Lawrence Dixon
xiv Preface to the Fourth Edition
Preface to Third Edition
Several modifications have been incorporated into the text in the light of recent advances in some aspects of the subject. Further information on the interesting phe- nomenon of cavitation has been included and a new section on the optimum design of a pump inlet together with a worked example have been added which