Table Of ContentCHEMISTRY
OF
ENGINE
COMBUSTION
DEPOSITS
CHEMISTRY
OF
ENGINE
COMBUSTION
DEPOSITS
Edited by
Lawrence B. Ebert
Exxon Corporate Research laboratories
Clinton. New Jersey
PLENUM PRESS • NEW YORK AND LONDON
library of Congress Cataloging in Publication Data
Main entry under title:
Chemistry of engine combustion deposits.
"Expanded version of the proceedings of a symposium on chemistry of
engine combustion deposits, held at the 181 st American Chemical Socie
ty meeting, March 30, 1981, in Atlanta, Georgia"-T.p. verso.
Bibliography: p.
Includes index.
1. Combustion deposits in engines-Congresses. I. Ebert, Lawrence, B. II.
American Chemical Society. Meeting. (181st: Atlanta, Georgia)
TJ756.C48 1985 621.43 85-3688
ISBN-13:978-1-4612-9498-6 e-ISBN-13:978-1-4613-2469-0
001:10.1007/978-1-4613-2469-0
Expanded version of the proceedings of a symposium on Chemistry of Engine
Combustion Deposits, held at the 181st American Chemical Society meeting,
March 30, 1981, in Atlanta, Georgia
© 1985 Plenum Press, New York
Softcover reprint of the hardcover 1st edition 1985
A Division of Plenum Publishing Corporation
233 Spring Street, New York, N.Y. 10013
All rights reserved
No part of this book may be reproduced, stored in a retrieval system, or transmitted,
in any form or by any means, electronic, mechanical, photocopying, microfilming,
recording, or otherwise, without written permission from the Publisher
PREFACE
On March 30, 1981, a symposium entitled "Chemistry of
Engine Combustion Deposits" was held at the 181st American
Chemical Society National Meeting in Atlanta, Georgia, under the
sponsorship of the Petroleum Division. This book is an out
growth of that symposium, including papers from all of the
At 1a nta presentors, as we 11 as from others who were i nvi ted to
contribute.
Research on engine deposits has not been as "glamorous" as
in the rel ated fossil fuel areas of petrol eum, coal, or oil
shale, and publications in the field have been largely confined
to combustion and automotive engineering journals. One objec
tive of this book is to bring a large body of work on the
chemistry of deposits into more general accessibility. We hope
to make people more familiar with what deposits are, with what
problems they cause, and with what present workers are doing to
solve these problems.
The creation of the book has involved many people.
Patricia M. Vann of Plenum Publishing Corporation gave guidance
in planning. We thank Claire Bromley, Ellen Gabriel, and Halina
Markowski for the preparation of many of the Exxon contribu
tions. Finally, we thank Joseph C. Scanlon for his useful
advice and encouragement.
Lawrence B. Ebert
Exxon Research and Engineering Company
Route 22 East
Annandale, New Jersey 08801
v
CONTENTS
Introduction • . 1
J.P. Longwell
Chemistry of Engine Combustion Deposits:
Literature Review . . • • • 3
L.B. Ebert
Effects of Combustion Chamber Deposit Location
and Composition 19
K. Adams and R. Baker
Fuel-Related Factors Affecting Engine
Octane Requirements • • • • 39
L.B. Graiff
On the Chemical Composition and Origin
of Engine Deposits • • • • • . • 53
W.O. Siegl and M. Zinbo
The Chemistry of Internal Combustion Engine Deposits --
I. Microanalysis, Thermogravimetric Analysis, and
Infrared Spectroscopy • . • . . . • . 71
L.B. Ebert, W.H. Davis, Jr., D.R. Mills
and J.D. Dennerlein
II. Extraction, Mass Spectroscopy and
Nuclear Magnetic Resonance • . • . • . • 101
W.H. Davis, Jr., L.B. Ebert, J.D. Dennerlein
and D.R. Mills
III. l3C Nuclear Magnetic Resonance Employing lH
Cross-Polarization and Magic
Angle Spinning • . . • • • • . . . . 119
L.B. Ebert, K.D. Rose and M.T. Melchior
Electron Spin Resonance Studies of
Internal Combustion Engine Deposits 145
L.A. Gebhard, R.S. Lunt and B.G. Silbernagel
The Effect of the Combustion Chamber Deposits
on Octane Requirement Increase and Fuel Economy 199
Y. Nakamura, Y. Yonekawa and N. Okamoto
Modelling the Effect of Engine Deposit
on Octane Requirements •••• 213
A. DeGregoria
Deposit Formation by Diffusion of Flame Intermediates
to a Cold Surface • • • • • • • • • . • • • 227
J.D. Bittner, S.M. Faist, J.B. Howard
and J.P. Longwell
Jet Aircraft Fuel System Deposits 245
R.N. Hazlett and J.M. Hall
Soot Reduction in Diesel Engines by Catalytic Effects 263
R. Sapienza, T. Butcher, C.R. Krishna
and J. Gaffney
Engine Deposits and the Determination of their
Origin by Atomic Emission Spectrometry • 273
E. Guinat
Evaluation of Engine Deposits in a Modified
Single-Cylinder Engine Test •• . • • 277
I.J. Spilners, J.F. Hedenburg and C.R. Spohn
Effect of Fuel and Lubricant Composition on
Engine Deposit Formation • • • 289
I.J. Spilners and J.F. Hedenburg
Reductive Chemistry of Aromatic Hydrocarbon Molecules 303
L.B. Ebert
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Index 377
viii
INTRODUCTION
John P. Longwell
Department of Chemical Engineering
Massachusetts Institute of Technology
Cambridge. MA 02139
The symposium reported in this book was held in early
1981 and is based on work performed during the preceding few years
when soari ng fuel pri ces and impendi ng shortages had st i mul ated
studies of all factors affecting the efficiency of fuel use and
manufacture. Deposits formed in the engine combustion chamber are
of major interest because they affect engine efficiency by
changing fuel octane number requirement and by changing heat loss
to the cooling system. Physical interference with piston ring and
gas flow through the valves can also occur. Also. the porous
nature of the deposits is believed to be responsible for cyclic
accumulation and release of hydrocarbons. thus increasing hydro
carbon emissions.
The papers. presented here. highlight the complex nature
of sources of deposits and their effects on engine performance.
Recent changes in lubricant and fuel composition as well
as engi ne design have forced re-eva 1u at i on of the nature of the
problem. and the classic engine and fleet testing remain an im
portant component of an overall program. Confi rmi ng 01 der work.
deposits in the end gas zone are held responsible for octane
requi rement increase. Both fuel and 1u bri cant can contri buteo
Oil consumption is important since oil can contribute inorganic
components and react i ve mol ecu 1e s. The re 1a t i ve cont ri but i on of
fuel and lubricant depends strongly on their composition and on
engine design and condition. Inorganic fuel components are
becoming less important with the drastic reduction in lead tetra
ethyl content. but the accompanying increase in aromatics tends to
increase deposit formation. A new observation is the reported
large increase in fuel economy resulting from reduced heat loss to
cooling water when the combustion chamber is insulated on the
inside by combustion deposits or by a teflon coating. The impli
cations of this observation obviously require further study since
deposits in the end zone are probably deleterious because of ORI,
while the insulating effect of deposits elsewhere may be
desirable.
A highlight of the symposium is the application of
modern analytical and computer modeling methods to advance toward
a more detail ed understandi ng of the chemi stry and physi cs of
depos its and thei r effect of ORIon performance. A computer
model, taking into account the cyclic heat transfer through an
insulating layer of deposit, shows the effect of increasing end
gas temperature (and, therefore, knocking tendency), the effect of
lowered heat loss on effi c i ency and the sma 11 effect of depos it
volume on compression ratio. While in their early stages, such
models are an important tool for quantitative testing of various
hypotheses for explanation of observed effects.
Relatively little work has been done on the chemistry of
the polymerization process by which deposits are formed. Studies
of composition have, however, advanced by adding 13C NMR to the
array of tools being applied to this problem. The bulk of carbon
in deposits from both engines and a laboratory flame was found to
be aromatic in nature. This correlates with the observation that
aromatic compounds in fuel or lubricant greatly increase deposit
formation. Studies using a laboratory laminar flame produced
deposits from benzene fuel, but none from an aliphatic fuel.
Formaldehyde and acetylene diffused to the cold surface for both
flames; however, phenol was a major diffusing species for the
depos i t formi ng benzene and is imp 1; cated as a cont ri butor to
deposit formation.
Resea rch on the spa rk i gn it ion engi ne depos i t prob 1e m
has diminished with the current decrease in concern over fuel
price and supply; however, the economic problem of continuing high
cost for fuel to the consumer, and international competition for
improved engi ne performance call s for continued effort to under
stand and solve deposit related problems.
2
CHEMISTRY OF ENGINE COMBUSTION DEPOSITS: LITERATURE REVIEW
Lawrence B. Ebert
Corporate Research-Science Laboratories
Exxon Research and Engineering Company
P. O.Box 45
Linden, NJ 07036
I. INTRODUCTION
As an autombile engine runs, its fuel quality requirements,
as measured by the octane number of the fuel needed to i nhi bit
knocking, may change in time. Historically, this phenomenon is
referred to as the "ORI" problem, standing for octane require
ment increase.
Octane requi rement increase can be quant ifi ed. Knock can
be perceived, by either people or instruments, by an audible
"pinging" sound emanating from the engine, caused by an approxi
mately 5000 Hz vibration of the engine structure induced by gas
pressure waves within the combustion chamber. These waves are
created by "auto ignition" of the gas ahead of the normal flame
front. By using a variety of test fuels, of known octane
rat i ng, one determi nes the octane requi rement of the engi ne as
that octane for which knock is "borderline". The octane
requirement increase is simply the difference between the final
octane requirement and the initial octane requirement of an
engine. Figure 1 illustrates actual examples of the "ORI"
problem.
The single most important operational variable affecting
"ORI" is the presence of combustion chamber deposits. As the
flame front progresses across the chamber, it never actually
touches the relatively cool wall, and carbonaceous materials
coat the inside surfaces of the combustion volume, illustrated
in Figure 2. Modification or elimination of these deposits can
have a beneficial impact on the octane requirement increase
problem.
3
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Figure 1. Examples of "octane requirement i ncrease" for
automobile engines.
4
