Engine Testing Theory and Practice P1

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The preface of this book is probably the least read section of all; however, it is the only part in which I can pay tribute to my friend and co-author of the first two editions, Dr Michael Plint, who died suddenly in November 1998, only four days after the publication of the second edition.

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Engine Testing
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Engine Testing Theory and Practice Third edition A.J. Martyr M.A. Plint AMSTERDAM • BOSTON • HEIDELBERG • LONDON • NEW YORK • OXFORD PARIS • SAN DIEGO • SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO Butterworth-Heinemann is an imprint of Elsevier
Butterworth-Heinemann is an imprint of Elsevier Linacre House, Jordan Hill, Oxford OX2 8DP 30 Corporate Drive, Suite 400, Burlington, MA 01803 First edition 1995 Reprinted 1996 (twice), 1997 (twice) Second edition 1999 Reprinted 2001, 2002 Third edition 2007 Copyright © 2007, A.J. Martyr and M.A. Plint. Published by Elsevier Ltd. All rights reserved The right of A.J. Martyr and M.A. Plint to be identified as the authors of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988 No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the publisher Permissions may be sought directly from Elsevier’s Science & Technology Rights Department in Oxford, UK: phone (+44) (0) 1865 843830; fax: (+44) (0) 1865 853333; email: permissions@elsevier.com. Alternatively you can submit your request online by visiting the Elsevier web site at http://elsevier.com/locate/permissions, and selecting Obtaining permission to use Elsevier material Notice No responsibility is assumed by the publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. Because of rapid advances in the medical sciences, in particular, independent verification of diagnoses and drug dosages should be made British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress ISBN-13: 978-0-7506-8439-2 For information on all Butterworth-Heinemann publications visit our web site at http://books.elsevier.com Printed and bound in the UK 07 08 09 10 10 9 8 7 6 5 4 3 2 1 Working together to grow libraries in developing countries www.elsevier.com | www.bookaid.org | www.sabre.org
Contents Preface vii Acknowledgements ix Introduction xi Units and conversion factors xv 1 Test facility specification, system integration and project organization 1 2 The test cell as a thermodynamic system 14 3 Vibration and noise 21 4 Test cell and control room design: an overall view 47 5 Ventilation and air conditioning 72 6 Test cell cooling water and exhaust gas systems 108 7 Fuel and oil storage, supply and treatment 129 8 Dynamometers and the measurement of torque 144 9 Coupling the engine to the dynamometer 170 10 Electrical design considerations 197 11 Test cell control and data acquisition 216 12 Measurement of fuel, combustion air and oil consumption 242 13 Thermal efficiency, measurement of heat and mechanical losses 263 14 The combustion process and combustion analysis 282 15 The test department organization, health and safety management, risk assessment correlation of results and design of experiments 308 16 Exhaust emissions 324 17 Tribology, fuel and lubrication testing 354 18 Chassis or rolling road dynamometers 368 19 Data collection, handling, post-test processing, engine calibration and mapping 395 20 The pursuit and definition of accuracy: statistical analysis of test results 408 Index 423
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Preface The preface of this book is probably the least read section of all; however, it is the only part in which I can pay tribute to my friend and co-author of the first two editions, Dr Michael Plint, who died suddenly in November 1998, only four days after the publication of the second edition. All the work done by Michael in the previous editions has stood up to the scrutiny of our readers and my own subsequent experience. In this edition, I have attempted to bring our work up to date by revising the content to cover the changing legislation, techniques and some of the new tools of our industry. In a new Chapter 1, I have also sought to suggest some good practices, based on my own 40 years of experience, aimed at minimizing the problems of project organization that are faced by all parties involved in the specification, modification, building and commissioning of engine test laboratories. The product of an engine test facility is data and byproduct is the experience gained by the staff and hopefully retained by the company. These data have to be relevant to the experiments being run, and every component of the test facility has to play its part, within an integrated whole, in ensuring that the test data are as valid and uncorrupted as possible, within the sensible limits of the facility’s role. It was our intention when producing the first edition to create an eclectic source of information that would assist any engineer faced with the many design and operational problems of both engine testing and engine test facilities. In the intervening years, the problems have become more difficult as the nature of the engine control has changed significantly, while the time and legislative pressures have increased. However, it is the laws of physics that rule supreme in our world and they can continue to cause problems in areas outside the specialization of many individual readers. I hope that this third edition helps the readers involved in some aspect of engine testing to gain a holistic view of the whole interactive package that makes up a test facility and to avoid, or solve, some of the problems that they may meet in our industry. Having spoken to a number of readers of the two proceeding editions of this book I have reorganized the contents of most of the chapters in order to reflect the way in which the book is used. Writing this edition has, at times, been a lonely and wearisome task that would not have been completed without the support of my wife Diana and my friends. Many people have assisted me with their expert advice in the task of writing this third edition. I have to thank all my present AVL colleagues in the UK and Austria, particularly Stuart Brown, David Moore and Colin Freeman who have shared many
viii Preface of my experiences in the test industry over the last 20 years, also Dave Rogers, Craig Andrews, Hans Erlach and finally Gerhard Müller for his invaluable help with the complexities of electrical distribution circuits. A.J. Martyr Inkberrow 22 September 2006
Acknowledgements Figures 3.6, 3.13, 3.15 and 3.16 Reprinted from Industrial Noise Control, Fader, by permission of John Wiley and Sons Ltd Figure 3.9 Reprinted from technical literature of Type TSC by courtesy of Christie and Grey Ltd, UK Figure 3.14 Reprinted from Encyclopaedia of Science and Technology, Vol. 12, 1987, by kind permission of McGraw-Hill Inc., New York Figure 5.3 Reprinted from CIBSE Guide C, section C4, by permission of the Char- tered Institution of Building Services Engineers Figure 5.10 Reprinted from I.H.V.E. Psychometric Chart, by permission of the Chartered Institution of Building Services Engineers Figure 7.1 Reprinted from BS799. Extracts from British Standards are reprinted with the permission of BSI. Complete copies can be obtained by post from BSI Sales, Linford Wood, Milton Keynes, MK14 6LE, UK Figure 7.2 Reprinted from The Storage and Handling of Petroleum Liquids, Hughes and Swindells, with the kind permission of Edward Arnold Publishers Figure 7.3 Reprinted from ‘Recommendations for pre-treatment and cleaning of heavy fuel oil’ with the kind permission of Alfa Laval Ltd Figure 8.3 Reprinted from Drawing no. GP10409 (Carl Shenck AG, Germany) Figures 8.4 and 8.5 Reprinted from Technical Documentation T 32 FN, with the kind permission of Hottinger Baldwin Messtechnik GmbH, Germany Figures 8.6 and 8.7 Illustration courtesy of Ricardo Test Automation Ltd Figures 8.9, 8.10 and 8.11 Reprinted with permission of Froude Consine, UK Figure 8.12 Reprinted from technical literature, Wichita Ltd Figure 9.4 Reprinted from Practical Solution of Torsional Vibration Problems, 3rd edition, W. Ker-Wilson, 1956 Figure 9.7 Reprinted from literature, with the kind permission of British Autoguard Ltd Figures 9.8 and 9.11 Reprinted from sales and technical literature, with the kind permission of Twilfex Ltd Figure 12.2 Reprinted from Paper ISATA, 1982, R.A. Haslett, with the kind permis- sion of Cussons Ltd Figure 12.4 Reprinted from Technology News with the kind permission of Petroleum Review Figure 14.7 Reprinted from SAE 920 462 (SAE International Ltd) Figure 17.1 From Schmiertechnik und Tribologie 29, H. 3, 1982, p. 91, Vincent Verlag Hannover (now: Tribologie und Schmierungstechnik)
x Acknowledgements Figures 17.2 and 17.3 Reprinted by permission of the Council of the Institution of Mechanical Engineers from ‘The effect of viscosity grade on piston ring wear’, S.L. Moore, Proc. I. Mech. E C184/87 Figure 18.2 Illustration courtesy of Ricardo Test Automation Ltd Figures 2.3, 5.4, 5.5, 5.6, 5.7, 6.8, 7.5, 7.6, 10.5 10.8, 14.9, 14.10, 14.11, 16.1, 16.2, 16.5, 16.7, 16.8 and 18.4 Reprinted by kind permission of AVL List GmbH
Introduction Over the working lifetime of the authors the subject of internal engine development and testing has changed, from being predominantly within the remit of mechanical engineers, into a task that is well beyond the remit of any one discipline that requires a team of specialists covering, in addition to mechanical engineering, electronics, power electrics, acoustics, software, computer sciences and chemical analysis, all supported by expertise in building services and diverse legislation. It follows that the engineer concerned with any aspect of engine testing, be it fundamental research, development, performance monitoring or routine production testing, must have at his fingertips a wide and ever-broadening range of knowledge and skills. A particular problem he must face is that, while he is required to master ever more advanced experimental techniques – such areas as emissions analysis and engine calibration come to mind – he cannot afford to neglect any of the more traditional aspects of the subject. Such basic matters as the mounting of the engine, coupling it to the dynamometer and leading away the exhaust gases can give rise to intractable problems, misleading results and even on occasion to disastrous accidents. More than one engineer has been killed as a result of faulty installation of engines on test beds. The sheer range of machines covered by the general term internal combustion engine broadens the range of necessary skills. At one extreme we may be concerned with an engine for a chain saw, a single cylinder of perhaps 50 c.c. capacity running at 15 000 rev/min on gasoline, with a running life of a few hours. Then we have the vast number of passenger vehicle engines, four, six or eight cylinder, capacities ranging from one litre to six, expected to develop full torque over speeds ranging from perhaps 1500 rev/min up to 7000 rev/min (the upper limit rising continually), and with an expected life of perhaps 6000 hours. The motor-sport industry continues to push the limits of both engine and test plant design with engines revving at speeds approaching 20 000 r.p.m. and, in rally cars, engine control systems having to cope with cars leaving the ground, then requiring full power when they land. At the other extreme is the cathedral type marine engine, a machine perhaps 10 m tall and weighing 1000 tonnes, running on the worst type of residual fuel, and expected to go on turning at 70 rev/min for more than 50 000 hours. The purpose of this book is to bring together the information on both the theory and practice of engine testing that any engineer responsible for work of this kind must have available. It is naturally not possible, in a volume of manageable size, to give all the information that may be required in the pursuit of specialized lines of development, but it is the intention of the authors to make readers aware of the many
xii Introduction tasks they may face and to give advice based on experience; a range of references for more advanced study has been included. Throughout the book accuracy will be a recurring theme. The purpose of engine testing is to produce information, and inaccurate information can be useless or worse. A feeling for accuracy is the most difficult and subtle of all the skills required of the test engineer. Chapter 19, dealing with this subject, is perhaps the most important in the book and the first that should be read. Experience in the collaboration with architects and structural engineers is par- ticularly necessary for engineers involved in test facility design. These professions follow design conventions and even draughting practices that differ from those of the mechanical engineer. To give an example, the test cell designer may specify a strong floor on which to bolt down engines and dynamometers that has an accuracy approaching that of a surface plate. To the structural engineer this will be a startling concept, not easily achieved. The internal combustion engine is perhaps the best mechanical device available for introducing the engineering student to the practical aspects of engineering. An engine is a comparatively complicated machine, sometimes noisy and alarming in its behaviour and capable of presenting many puzzling problems and mystifying faults. A few hours spent in the engine testing laboratory are perhaps the best possible introduction to the real world of engineering, which is remote from the world of the lecture theatre and the computer simulation in which, inevitably, the student spends much of his time. While it contains some material only of interest to the practising test engineer, much of this book is equally suitable as a student text, and this purpose has been kept very much in mind by the authors. In response to the author’s recent experience, the third edition has a new Chapter 1 dedicated to the problems involved in specifying and managing a test facility build project. A note of warning: the general management of engine tests What may be regarded as traditional internal combustion engines had in general very simple control systems. The spark ignition engine was fitted with a carburettor controlled by a single lever, the position of which, together with the resisting torque applied to the crankshaft, set all the parameters of engine operation. Similarly, the performance of a diesel engine was dictated by the position of the fuel pump rack, either controlled directly or by a relatively simple speed governor. The advent of engine control units (ECUs) containing ever more complex maps and taking signals from multiple vehicle transducers has entirely changed the sit- uation. The ECU monitors many aspects of powertrain performance and makes continuous adjustments. The effect of this is effectively to take the control of the test conditions out of the hands of the engineer conducting the test. Factors entirely extraneous to the investigation in hand may thus come into play.
Introduction xiii The introduction of exhaust gas recirculation (EGR) under the control of the ECU is a typical example. The only way open to the test engineer to regain control of his test is to devise means of bypassing the ECU, either mechanically or by intervention in the programming of the control unit. A note on references and further information It would clearly not be possible to give all the information necessary for the practice of engine testing and the design of test facilities in a book of this length. References suitable for further study are given at the end of most chapters. These are of two different kinds: • a selection of fundamental texts or key papers • relevant British Standards and other reference standard specifications. The default source of many students is now the world wide web which contains vast quantities of information related to engines and engine testing, much of which is written by and for the automotive after-market where a rigorous approach to experimental accuracy is not always evident; for this reason and due to the transient nature of many websites, there are very few web-based references.
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Units and conversion factors Throughout this book use is made of the metric system of units, variously described as: The MKS (metre-kilogram-second) System SI (Système International) Units These units have the great advantage of logical consistency but the disadvantages of still a certain degree of unfamiliarity and in some cases of inconvenient numerical values. Fundamental Units Mass kilogram (kg) 1 kg = 2.205 lb Length metre (m) 1 m = 39.37 in Force newton (N) 1 N = 0.2248 lbf Derived Units Area square metre (m2 ) 1 m2 = 10.764 ft2 Volume cubic metre (m3 ), litre (l) 1 m3 = 10001 = 35.3 ft3 Velocity metre per second (m/s) 1 m/s = 3.281 ft/s Work, Energy joule (J) 1 J = 1 Nm = 0.7376 ft-lbf Power watt (W) 1 W = 1 J/s 1 horsepower (hp) = 745.7 W Torque newton metre 1 Nm = 0.7376 lbf-ft The old metric unit of energy was the calorie (cal), the heat to raise the temperature of 1 gram of water by 1 C. 1 cal = 4.1868 J. 1 kilocalorie (kcal) = 4.1868 kJ. Temperature degree Celsius C Absolute temperature kelvin K T T = + 273 15 Pressure pascal (Pa) 2 1 Pa = 1 N/m = 1.450 × 10−4 lbf/in2 1 MPa = 106 Pa = 145 lbf/in2
xvi Units and conversion factors This unit is commonly used to denominate stress. Throughout this book the bar is used to denominate pressures: 1 bar (bar) = 105 Pa = 14.5 lbf/in3 Standard test conditions for i.c. engines as defined in BS 5514/ISO 30461 specify: Standard atmospheric pressure = 1 bar = 14.5 lbf/in2 Note: ‘Standard atmosphere’ as defined by the physicist2 is specified as a barometric pressure of 760 millimetres of mercury (mmHg) at 0 C. 1 standard atmosphere = 1.01325 bar = 14.69 lbf/in2 The difference between these two standard pressures is a little over 1 per cent. This can cause confusion. Throughout this book 1 bar is regarded as standard atmospheric pressure. The torr is occasionally encountered in vacuum engineering. 1 torr = 1 mmHg = 133.32 Pa In measurements of air flow use is often made of water manometers. 1 mm of water (mmH2 O) = 9.81 Pa References 1. BS 5514 Reciprocating Internal Combustion Engines: Performance. 2. Kaye, G.W.C. and Laby, T.H. (1973) Tables of Physical and Chemical Constants, Longmans, London. Further reading BS 350 Pt 1 Conversion factors and tables BS 5555 Specification for SI units and recommendations for the use of their multiples and of certain other units
1 Test facility speciﬁcation, system integration and project organization Introduction An engine test facility is a complex of machinery, instrumentation and support services, housed in a building adapted or built for its purpose. For such a facility to function correctly and cost-effectively, its many parts must be matched to each other while meeting the operational requirements of the user and being compliant with various regulations. Engine and vehicle developers now need to measure improvements in engine per- formance that are frequently so small as to require the best available instrumentation in order for fine comparative changes in performance to be observed. This level of measurement requires that instrumentation is integrated within the total facility such that their performance and data are not compromised by the environment in which they operate and services to which they are connected. Engine test facilities vary considerably in power rating and performance; in addi- tion there are many cells designed for specialist interests, such as production test or study of engine noise, lubrication oils or exhaust emissions. The common product of all these cells is data that will be used to identify, modify, homologate or develop performance criteria of all or part of the tested engine. All post-test work will rely on the relevance and veracity of the test data, which in turn will rely on the instrumentation chosen to produce it and the system within which the instruments work. To build or substantially modify a modern engine test facility requires co- ordination of a wide range of specialized engineering skills; many technical managers have found it to be an unexpectedly complex task. The skills required for the task of putting together test cell systems from their many component parts have given rise, particularly in the USA, to a specialized industrial role known as system integration. In this industrial model, a company or more rarely a consultant, having one of the core skills required, takes contractual responsibility for the integration of all of the test facility components from various sources. Commonly, the integrator role has been carried out by the supplier of test cell control systems and the role has been restricted to the integration of the dynamometer and control room instrumentation.
2 Engine Testing In Europe, the model is somewhat different because of the long-term development of a dynamometry industry that has given rise to a very few large test plant contracting companies. However, the concept of systems integrator is useful to define that role, within a project, that takes the responsibility for the final functionality of a test facility; so the term will be used, where appropriate, in the following text. This chapter covers the vital importance of good user specification and the various organizational structures required to complete a successful test facility project. Test facility speciﬁcation Without a clear and unambiguous specification no complex project should be allowed to proceed. This book suggests the use of three levels of specification: 1. Operational specification: describing ‘what it is for’, created by the user prior to any contract to design or build a test facility. 2. Functional specification: describing ‘what it consists of and where it goes’, created either by the user group having the necessary skills, as part of a feasibility study by a third party, or by the main contractor as part of the first phase of a contract. 3. Detailed functional specification: describing ‘how it all works’ created by the project design authority within the supply contract. Creation of an operational speciﬁcation This chapter will tend to concentrate on the operational specification which is a user- generated document, leaving some aspects of the more detailed levels of functional specification to subsequent chapters covering the design process. The operational spec- ification should contain a clear description of the task for which the facility is being created. It need not specify in detail the instruments required, nor does it have to be based on a particular site. The operational specification is produced by the end user; its first role will normally be to support the application for budgetary support and out- line planning; subsequently, it remains the core document on which all other detailed specifications are based. It is sensible to include a brief description of envisaged facility acceptance tests within the document since there is no better means of developing and communicating the user’s requirement than to describe the results to be expected from described work tasks. • It is always sound policy to find out what is available on the market at an early stage, and to reconsider carefully any part of the specification that makes demands that exceed what is commonly offered. • A general cost consciousness at this stage can have a permanent effect on capital and subsequent running costs.
Test facility speciﬁcation, system integration and project organization 3 Because of the range of skills required in the design and commissioning of a ‘green field’ test laboratory it is remarkably difficult to produce a succinct specification that is entirely satisfactory, or even mutually comprehensible, to all specialist participants. The difficulty is compounded by the need for some of the building design details that determine the final shape, such as roof penetrations or floor loadings, to be deter- mined before the detailed design of internal plant has been finalized. It is appropriate that the operational specification document contains statements concerning the gen- eral ‘look and feel’ and any such pre-existing conditions or imposed restrictions that may impact on the facility layout. It should list any prescribed or existing equipment that has to be integrated, the level of staffing and any special industrial standards the facility is required to meet. In summary, it should at least address the following questions: • What are the primary and secondary purposes for which the facility is intended and can these functions be condensed into a sensible set of acceptance procedures to prove the purposes that may be achieved? • What is the realistic range of units under test (UUT)? • How are test data (the product of the facility) to be displayed, distributed, stored and post-processed? • What possible extension of specification or further purposes should be provided for in the initial design and to what extent would such ‘future proofing’ distort the project phase costs? • May there be a future requirement to install additional equipment and how will this affect space requirement? • Where will the UUT be prepared for test? • How often will the UUT be changed and what arrangements will be made for transport into and from the cells? • How many different fuels are required and must arrangements be made for quantities of special or reference fuels? • What up-rating, if any, will be required of the site electrical supply and distribution system? • To what degree must engine vibration and exhaust noise be attenuated within the building and at the property border? • Have all local regulations (fire, safety, environment, working practices, etc.) been studied and considered within the specification? Feasibility studies and outline planning permission The work required to produce a site-specific operational specification, or statement of intent, may produce a number of alternative layouts each with possible first- cost or operational problems. In all cases an environmental impact report should be produced covering both the facility’s impact of its surroundings and, in the case of low emission measuring laboratories, the locality’s impact on the facility.