Engine Testing - 4th Edition PDF
Preview Engine Testing - 4th Edition
Engine Testing The Design, Building, Modification and Use of Powertrain Test Facilities A. J. Martyr M. A. Plint AMSTERDAM l BOSTON l HEIDELBERG l LONDON NEW YORK l OXFORD l PARIS l SAN DIEGO SAN FRANISCO l SINGAPORE l SYDNEY l TOKYO Butterworth-Heinemann is an imprint of Elsevier Butterworth-Heinemann is an imprint of Elsevier The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, UK 225 Wyman Street, Waltham, MA 02451, USA 525 B Street, Suite 1900, San Diego, CA 92101-4495, USA First edition 1995 Second edition 1999 Third edition 2007 Fourth edition 2012 Copyright Ó 2012 Elsevier Ltd. All rights reserved. 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: About the Authors A. J. Martyr has held senior technical positions with several of the major test plant manufacturers and consultancy firms over the last 45 years. He is now Honorary Visiting Professor of Powertrain Engineering at Bradford University. M. A. Plint died in November 1998, four days after the publication of the second edition and after a long and distinguished career in engineering and authorship. xxi Foreword to the Fourth Edition The original intention of myself and my late co-author of the first two editions, Mike Plint, was to pass on to younger engineers our wide, but nonspecialist, knowledge of powertrain testing and the construction of the cells in which it takes place. I am a product of what is probably the last generation of mechanical engineers to have benefitted from a five-year apprenticeship with a UK-based engineering company who was able to give its trainees hands-on experience of almost every engineering trade, from hand-forging and pattern making, through machine-shop practice and fitting, to running and testing of steam and gas turbines and medium-speed diesel engines. After 50 years of involvement in the testing and commissioning engines and transmissions, of designing and project managing the construction of the test equipment and facilities required, this will be the last edition of this book in which I play a part. The specialist engineer of today is surrounded by sources of information on every subject he or she may be required to learn in the course of their career. Should they be asked to carry out, or report on the task, for example, of con- verting a diesel engine test cell to also run gasoline engines, the immediate reaction of many will be to sit in front of a computer and type the problem into a search engine. In less than one second they will be confronted with over four million search results, the majority of which will be irrelevant to their problem and a few will be dangerously misleading. It is my hope that occasionally those searches might find this book and that not only the section related to a problem will be read. My own research and reader feedback has led me to define three general types of readership. The first, and for any author the most rewarding, is the student engineers who have been given the book by their employers at the start of their career and who have read most of it, from start to finish, as it was written. To those readers I apologize for repeating myself on certain subjects; such repetition is to benefit those who only look at the book to gain specific, rather than general, knowl- edge. The least rewarding is those specialist engineers who, as an exercise in self-reassurance, read only those sections in which they have more expertise than myself and who might have found benefit in reading sections outside their specialization. Of the remaining readership the most irritating are those who obtain the book in order to resolve some operational or constructional problem xix xx Foreword to the Fourth Edition within a test facility, that would have been avoided had the relevant section been read before the work was done. The most frequent problems faced by the latter group, much to my irritation and their expense, are those dealing with some form of cell ventilation problem or those who “have always used this type of shaft and never had any problems before”. We all face the problems of working in an increasingly risk-averse world where many officials, representing some responsible authority, seem to consider the operation of an engine test cell to be a risk akin to some experi- mental explosives research institute, an opinion confirmed if they are allowed to witness a modern motor-sport engine running at full power before they drive away, safely, in their own cars. The subjects covered in this book now exceed the expertise of any one engineer and I have benefitted greatly from the knowledge and experience of many talented colleagues. Because of the risk of unforgivably forgetting someone, I hesitate to name all those who have unstintingly answered my questions and commented on some aspect of my work. However, I want to record my particular thanks to the following: To Stuart Brown, Craig Andrews, Colin Freeman, David Moore, and John Holden, with whom I have had the honor of working for some years and whose support has been invaluable, not only in the production of this book but in my working life. To Hugh Freeman for his cheerfully given help concerning modern automotive transmission testing and Ken Barnes for his guidance on the American view on the subjects covered. To George Gillespie and his team at MIRA, and to engineers from specialist companies (mentioned in the relevant chapters) who have responded to my requests for information or the use of graphics. My colleagues at the School of Engineering at the University of Bradford, Professor Ebrahimi and Byron Mason, have allowed me to keep up to date with engine research and the operation of the latest instrumentation. Of my past colleagues based in Graz special mention must be made of electrical engineer Gerhard Mu¨eller. Finally, particular thanks to Antonios Pezouvanis of the University of Bradford, who has supplied both assistance and illustrations. Writing a book is an act of arrogance, for which the author pays dearly by hours and hours of lonely typing. Thanks must be given to my neighbor and friend David Ballard for proofreading those chapters that had become so agonized over that I was incapable of judging their syntax. Finally, Hayley Salter and Charlotte Kent of Elsevier, who have been my “help of last resort”, and to my family for their tolerance concerning the hours spent locked away on “the bloody book”. Tony Martyr Inkberrow July 2011 Introduction This book is not intended to be exclusively of interest to automotive engi- neers, either in training or in post, although they have formed the majority of the readership of previous editions. It is intended to be of assistance to those involved not only with the actual testing of engines, powertrains and vehicles, but also with all aspects of projects that involve the design, planning, building, and major modernization of engine and powertrain test facilities. We are today (2011) at a significant break in the continuity of automotive engine and powertrain development. Such is the degree of system integration within the modern vehicle, marine, and generating machinery installations that the word “engine” is now frequently replaced in the automotive industries by the more general term “powertrain”. So, while much of this book is concerned with the design, construction, and use of facilities that test internal combustion engines, the boundaries of what exactly constitutes the primary automotive IC power source is becoming increasingly indistinct as hybridization, integration of electrical drives, and fuel cell systems are developed. The unit under test (UUT) in most cells today, running automotive engines, has to either include actual or simulated vehicle parts and controllers, not previously thought of as engine components. This volume covers the testing of these evolving powertrain technologies, including transmission modules, in so far as they affect the design and use of automotive test facilities. Drivers’ perception of their vehicle’s performance and its drivability is now determined less by its mechanical properties and more by the various software models residing in control systems interposed between the driver and the vehicle’s actuating hardware. Most drivers are unaware of the degree to which their vehicles have become “drive by wire”, making them, the driver, more of a vehicle commander than a controller. In the latter role the human uses the vehicle controls, including the accelerator pedal, to communicate his or her intention, but it is the engine control unit (ECU), calibrated and mapped in the test cell, that determines how and if the intention is carried out. In the lifetime of this volume this trend will develop to the point, perhaps, where driver behavior is regionally constrained. Twenty years ago drivability attributes were largely the direct result of the mechanical configuration of the powertrain and vehicle. Drivability and performance would be tuned by changing that configuration, but today it is the test engineers and software developers that select and enforce, through control “maps”, the powertrain and vehicle characteristics. xxiii xxiv Introduction In all but motor sport applications the primary criteria for the selected performance maps are those of meeting the requirements of legislative tests, and only secondarily the needs of user profiles within their target market. Both US and European legislation is now requiring the installation, in new light vehicles, of vehicle stability systems that, in a predetermined set of circumstances, judge that the driver is about to lose control or, in conditions that are outside a pre-programmed norm, intervenes and, depending on one’s view, either takes over powertrain control and attempts to “correct” the driver’s actions, or assists the driver to keep a conventional model of vehicle control. A potential problem with these manufacturer-specific, driver assistance systems is their performance in abnormal conditions, such as deep snow or corrugated sand, when drivers, few of whom ever read the vehicle user manual, may be unaware of how or if the systems should be switched on or off. Similarly, on-board diagnostic (OBD) systems are becoming mandatory worldwide but their capabilities and roles are far exceeding the legislatively required OBD-11 monitoring of the performance of the exhaust emission control system. Such systems have the potential to cause considerable problems to the test engineer rigging and running any part of an automotive powertrain in the test cell (see Chapter 11). The task of powertrain and vehicle control system optimization known as powertrain and vehicle calibration has led to the development of a key new role of the engine test cell, a generation of specially trained engineers, test tech- niques, and specialized software tools. The task of the automotive calibration engineer is to optimize the perfor- mance of the engine and its transmission for a range of vehicle models and drivers, within the constraints of a range of legislation. While engines can be optimized against legislation in the test cell, provided they are fitted with their vehicle exhaust systems, vehicle optimization is not such a precise process. Vehicle optimization requires both human and terrain interfaces, which intro- duces another layer of integration to the powertrain engineer. The same “world engine” may need to satisfy the quite different requirements of, for example, a German in Bavaria and an American in Denver, which means much power- train calibration work is specific to a vehicle model defined by chosen national terrain and driver profiles. This raises the subject of drivability, how it is specified and tested. In this book the author has, rather too wordily, defined drivability as follows: For a vehicle to have good drivability requires that any driver and passengers, providing they are within the user group for which the vehicle was designed, should feel safe and confident, through all their physical senses, that the vehicle’s reactions to any driver input, during all driving situations, are commensurate to that input, immediate, yet sufficiently damped and, above all, predictable. Testing this drivability requirement in an engine or powertrain test bed is difficult, yet the development work done therein can greatly affect the character Introduction xxv of the resulting vehicle(s); therefore, the engine test engineer must not work in organizational or developmental isolation from the user groups. A proxy for drivability of IC engine-powered vehicles that is currently used is a set of constraints on the rate of change of state of engine actuators. Thus, within the vehicle’s regions of operation covered by emission legislation, “smoothness” of powertrain actuator operation may be equated with acceptable drivability. The coming generation of electric vehicles will have drivability charac- teristics almost entirely determined by their control systems and the storage capacity of their batteries. The whole responsibility for specification, devel- opment, and testing this “artificial” control and drivability model, for every combination of vehicle and driver type, will fall upon the automotive engineer. Most drivability testing known to the author is based on a combination of subjective judgment and/or statistically compiled software models based on data from instrumented vehicles; this area of modeling and testing will be an interesting and demanding area of development in the coming years. Fortunately for both the author and readers of this book, those laws of chemistry and thermodynamics relevant to the internal combustion engine and its associated plant have not been subject to change since the publication of the first edition over 17 years ago. This means that, with the exception of clarifi- cations based on reader feedback, the text within chapters dealing with the basic physics of test facility design has remained little changed since the third edition. Unfortunately for us all, the laws made by man have not remained unchanging over the lifetime of any one of the previous editions. The evolution of these laws continues to modify both the physical layout of automotive test cells and the working life of many automotive test engineers. Where possible, this volume gives references or links to sources of up-to-date information concerning worldwide legislation. Legislation both drives and distorts development. This is as true of tax legislation as it is for safety or exhaust emission legislation. A concentration on CO2 emission, enforced via tax in the UK, has distorted both the development of engines and their test regimes. Legislation avoidance strategies tend to be developed, such as those that allow vehicles to meet “drive-by” noise tests at legislative dictated accelerations but to automatically bypass some silencing (muffling) components at higher accelerations. From many site visits and discussions with managers and engineers, it has been noticeable to the author that the latest generation of both test facility users and the commissioning staff of the test instrumentation tend to be specialists, trained and highly competent in the digital technologies. In this increasingly software-dependent world of automotive engineering, this expertise is vital, but it can be lacking in an appreciation of the mechanics, physics, and established best practices of powertrain test processes and facility requirements. Narrowing specialization, in the author’s recent experience, xxvi Introduction has led to operational problems in both specification and operation of test facilities, so no apology is offered for repeating in this edition some funda- mental advice based on experience. Many of the recommendations based on experience within this book have stories behind them worthy of a quite different type of volume. All test engineers live in a world that is increasingly dominated by digital technology and legal, objective, audited “box-ticking” requirements, yet the outcome of most automotive testing remains stubbornly analog and subjective. A typical requirement placed upon a powertrain test department could be: Carry out such testing that allows us to guarantee that the unit or component will work without failure for 150,000 miles (240,000 km). Such a task may be formalized through the use of a “development sign-off form”. If and when the prescribed test stages are concluded and without failure, such a procedure allows that the required box be ticked to acknowledge that the specified requirement can be guaranteed. But the true response is that we have simply increased our confidence in the unit being sufficiently durable to survive its design life. This not so subtle difference in approach to test results appears to the author to be one of the defining differences between the present generation, brought up in a world dominated by digital states and numbers, and a, usually older, generation whose world view is much more analogdsuccessful test operations will have a well-managed mixture of both approaches. In designing and running tests it is a fundamental requirement to ensure that the test life so far as is possible represents real life. Powertrain test cells had to become physically larger in order to accom- modate the various full vehicle exhaust systems, without which the total engine performance cannot be tested. Similarly, cell roof and corridor space has had to be expanded to house exhaust gas emission analyzers and their support systems (Chapter 16), combustion air treatment equipment, large electrical drives, and battery simulator cabinets (Chapter 5). Completely new types of test facilities have been developed, in parallel with the development of legislative requirements, to test the electromagnetic emission and vulnerability of whole vehicles, their embedded modules, wiring harnesses, and transducers (Chapter 18). The testers of medium-speed and large diesels have not been entirely forgotten in this edition and information covering their special area of work is referenced in the index. The final testers of a powertrain, and the vehicle system in which it is installed, are the drivers, the operators, and the owners. The commercial success of the engine manufacturer depends on meeting the range of expec- tations of this user group while running a huge variety of journeys; therefore, it has always been, and still remains, a fundamental part of the engine test Introduction xxvii engineer’s role to anticipate, find, and ensure correction of any performance faults before the user group finds them. The owner/driver of the latest generation of vehicles may consider that the majority of the new additions to the powertrain and vehicle are secondary to its prime function as a reliable means of locomotion. It can be argued that the increased complexity may reduce vehicle reliability and increase the cost of fault-finding and after-market repair; OBD systems need to become a great deal smarter and more akin to “expert systems”. The author cannot be alone in wondering about the long-term viability of this new generation of vehicles in the developing world, where rugged simplicity and tolerance to every sort of abuse is the true test of suitability. Thus, new problems related to the function, interaction, reliability, vulnerability, and predictability of an increasingly complex “sum of the parts” arise to test the automotive test engineer and developer. Unfortunately it is often the end user that discovers the vulnerability of the technologies embedded in the latest, legislatively approved, vehicles to “misuse”. This may be because the test engineer may, consciously or unconsciously, avoid test conditions that could cause malfunction; indeed, the first indication of such conditions represent the operational boundaries in a device’s control map during its development. The ever increasing time pressure on vehicle development has for many years forced testing of powertrain and vehicle modules to be done in parallel rather than in series. In modern systems this has necessitated increased module testing using hardware-in-the-loop (HIL) and software-in-the-loop (SIL) techniques, all of which rely on the use of software-based models of the missing components. Using modeling when the device being modeled is available, cheaper and easier to calibrate than the model generator is just one of the developments that raise some fundamental questions about the role of the test engineer, the test sequences used, and the criteria used to judge good results from poor ones.
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