A. SOKOLIK, Combustion and Detonation in Gases, GTTI, Moscow–Leningrad, 1934.

The broad development of the automobile and aviation industries in our country has been accompanied by the appearance of numerous monographs, textbooks, and popular books describing the design of engines, their assembly, and various processes.

Only one area has been unlucky in this respect: the basic process during which the necessary energy is released, converted later at a crucial moment of the engine’s motion—combustion—has until recently not been treated seriously in a single book. True, in recent times almost every work dealing with the design and operation of the motor devotes a few lines to the conditions of combustion and detonation, but for the most part the information presented is so fanciful and unreliable that it would have been better not to include it at all.

In the past year there has been a sharp turning point in this field: one can note the appearance of several monographs devoted exclusively to questions of combustion and detonation; moreover, these questions are treated chiefly from the standpoint of the operation of the internal-combustion engine, but in some books an attempt is made to illuminate the question more broadly and even to emphasize that exclusive attention to one problem, even if sufficiently important, has an unfavorable effect on the development of the general theory of combustion. Such conditions, together with enormous experimental successes in this field, lead to stagnation and to the absence of generalizations in the theoretical part, and this is why, to this day, the experimental material is in many cases almost inaccessible to anyone wishing to use it. Therefore, as a touchstone in evaluating any book on combustion and detonation, it is necessary to demand a definite approach to the facts presented and a grouping of them on the basis of a definite idea. Unfortunately, the majority of books that have appeared recently do not meet this last requirement: thus, in the collection Aviation Fuels there are placed works without any definite arrangement; these do not embrace not only any problem as a whole, but not even a part of one. The editors of the collection do not at all mention what principle guided them in selecting one article or another.

The little book by engineer Maslennikov has a somewhat more valuable character, but here too we see only a presentation of very rich material, quite carefully collected and listed one after another, without any attempt to find any connection or transition between the separate elements of combustion. The very content of the material included and the literature listed indicate, for the most part, the absence in the author of any point of view on this question: alongside obsolete and long-disproved data there are no references to many important works and to conclusions based upon them.

Engineer Elyansky’s book belongs to the type of writings that continue, to a considerable extent, to litter our market. The author has a very vague understanding of what should and should not be written, but at times he attempts to introduce something of his own. These attempts are always of very doubtful quality, and are sometimes altogether incorrect.

The most successful book on the question under consideration is A. Sokolik’s work, published by GTTI in 1934. The external presentation and the freshness of the material included make a very pleasant impression. The chief distinction of this booklet, in contrast to the works discussed above, consists in the author’s attempt to take the enormous material available, place it within definite limits, and indicate the connection between its separate aspects. The author sees the principal task of the contemporary stage in the study of combustion in the synthesis of the two main directions along which research in this field has developed: combustion in time and combustion in space. In spite of the rigor and the twofold simplicity displayed almost everywhere in the evaluation and interpretation of facts, the book is not one-sided, with all the points inconvenient for the author glossed over; on the contrary,

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Very often the disagreement of this or that experiment with the explanation which the author tries to give it is emphasized. Thus the book may be recognized as sufficiently objective and at the same time written with a definite attitude.

To what extent was it possible to achieve the task set in the preface and to unite “normal” and detonation combustion in spatio-temporal relations? Unfortunately, it must be admitted that such a synthesis is far from being carried out completely and not always with equal success. But here one must rather recognize the very slight reliability of many data, the absence of visible connections in some phenomena that are undoubtedly related, and, finally, the unusually deep intuition which is required of a person wishing to penetrate into the most intimate connection of individual scattered facts. Stating, therefore, that the task set has not been solved in the most general form, it is nevertheless necessary to note that a number of separate chapters and passages are written very successfully and interestingly. To such sections one may refer, for example, the characterization of the pre-detonation period, the study of the conditions for the emergence and propagation of the shock wave, the analysis of the concept of detonation as a constant characterizing a definite combustible mixture, the criticism of various theories explaining the onset of detonation in the engine, etc. Some definitions of rather important concepts are given in the book in overly general expressions or are entirely omitted, which cannot but be regretted, since some of them are now applied without sufficiently critical evaluation in the most appropriate and inappropriate cases. Among such very important concepts belong, for example, the shock wave, which the author defines only in the most general features, although it qualitatively differs from the pressure waves that arise during flame propagation. The very complex and tangled question of the reflection and interference of pressure waves from the gas layer and from the walls of the tube is touched upon by the author only very superficially.

The mechanism of the transfer of activation to individual molecules of the still unburned layer from the flame zone or by means of a shock wave is set forth by the author on the basis of Berthelot’s thermal theory, modified by Lewis. Pointing to the arbitrariness of the assumptions admitted in one case and the other, and to the fitting of results by the choice of the most improbable combinations and mechanisms, the author nevertheless does not try to replace these theories of the mechanism of combustion transfer, which are unquestionably vital in their essence, by any considerations of his own, and does not even cite certain facts from other fields that make it possible to illuminate this obscure question, such as, for example, the recoil of a molecule when it emits a single quantum of light energy. In setting forth the dependence of the detonation rate on the temperature of a gas mixture, only the theoretical assumptions of Kruiskop and the experiments of Dumanois are cited, without going deeply into the original conclusion which the latter investigator draws on this point.

The influence of the structure of hydrocarbons on their detonation qualities is examined, chiefly from a purely formal point of view. That precious material which is contained in the experiments of Wheeler and Boyd still awaits its interpreter. On the other hand, in the field of physico-chemical properties, and especially in deriving an estimate of detonation by “heat density,” interesting material has been collected, allowing one, with a considerable degree of probability, to foresee the occurrence of a detonation wave according to this parameter. Here, however, there remains completely open the widespread conviction that it is possible to judge the ease of the onset of detonation from the autoignition temperature.

Mentioning a number of merits of the book and interesting approaches to the solution of several very obscure and controversial problems, where the author is not afraid to express his opinion and to various theories, I cannot fail to point out that some aspects of normal and detonation combustion have been treated insufficiently fully. It was already indicated above that such a circumstance was observed also with respect to some basic concepts,

here one must point out the still more vexing absence of analysis, and even of mention, of extremely important facts that characterize this phenomenon. Thus, the question of the completeness of combustion during detonation and during “normal” combustion is not touched upon at all. The problem of the influence of preliminary alteration of the fuel during compression in the engine is barely mentioned, as are a whole series of other very important questions.

Turning to the description of the character of combustion in the engine, it must be admitted that the author—though not a specialist in internal-combustion engines—has nevertheless proved here to be far more competent and far-sighted than many persons who have devoted themselves specifically to the study of engines. The analysis of the character of combustion and of the influence upon it of such specific features as the change in the ignition-timing angle, elaborated with sufficient completeness. From this point of view, the author, as well as the compiler of the present note, maintains that knock in the engine is caused by the occurrence of a true detonation wave, and not by repeated reflection of the compression wave, rapid acceleration of flame propagation, and other circumstances which many investigators take as the primary causes of the occurrence of impacts in the engine.

The chapter devoted to the action of catalysts in the combustion process, and to the different role of tetraethyl lead when it is introduced into the engine and when it is tested in bombs, is only sparsely illuminated. The explanation of Finch, which the author considers sufficiently plausible, in reality seems highly strained and speculatively constructed.

In conclusion, one must welcome the publication of the present book, and moreover without significant delay, since all persons wishing to acquaint themselves with the phenomenon of combustion detonation can find in it a sufficiently clear and well-considered introduction to this interesting field.

P. Paniutin