Vulis – Fundamentals of the Theory of the Gas Torch
Vulis’s book, “Fundamentals of Gas Flame Theory,” presents the fundamentals of aerodynamic theory and calculation methods for straight-jet gas flames. It covers flow structure and turbulent combustion of unmixed gases, as well as flame thermal regimes (combustion stability, extinction, etc.). It also examines some special problems in flame theory, such as calculating high-speed combustion and flame interaction with an electromagnetic field.
Vulis’s book, “Fundamentals of Gas Flame Theory,” is intended for engineers—thermal physicists, power engineers, and mechanics—working in the research, design, and commissioning of combustion devices and related fields. It may be useful for graduate and undergraduate students in thermophysical and heat engineering specialties.
Many years ago, in a conversation with his students (including the author of these lines) about the then-new theory of turbulent jets, Georgy Fedorovich Knorre described it as a good basis for studying flames. In later years, he returned to this topic repeatedly, stating that he saw a reliable path to developing flame theory in combining methods of jet theory and combustion thermal regimes.
This monograph by Vulis, “Fundamentals of Gas Flame Theory,” is a modest step along this path. The task is still far from complete. Perhaps therefore, it is to be hoped that this attempt to present theoretical and experimental material from a unified perspective will contribute to the development of one of the most important questions in combustion theory and will prove useful to researchers, engineers, and students.
This book, “Fundamentals of Gas Flame Theory,” by Vulis, is devoted to the development of aerodynamic theory and the straight-jet gas flame. The research method adopted and some of its results are more general in nature and are likely of interest for combustion theory and precision combustion in general.
Aerodynamic combustion theory is the name given to a line of research that emphasizes the study of the laws of motion of a burning flow and the corresponding processes of momentum, matter, and energy transfer, among others. The limiting model, in which the rate of chemical reactions is assumed to be infinite, best suits combustion aerodynamics in its purest form. In this approximation, it is possible, for relatively simple cases, to calculate a detailed picture of the distribution of key aerodynamic quantities in the flow—flow velocity, temperature, concentrations of reactants, etc. Issues of combustion stability, stabilization, ignition, and breakdown are naturally not considered in this formulation of the problem. Moreover, the assumption of perfect mixing practically excludes complete combustion from the calculation parameters.
A more detailed study of the flame becomes possible by combining the concepts of Stock’s aerodynamics and the thermal combustion regime. Obtaining sufficiently general and illustrative results in this way is associated with a strong schematization of the laws of chemical kinetics and consideration of only the most specific properties of exothermic reactions [11. 21; 27; 47; 56; 89]. In this case, and primarily by taking into account the sharp temperature dependence of the reaction rate, it becomes possible, along with identifying the aerodynamic structure of the flow, to find the limits of the existence of stable combustion, determine the completeness of combustion, the critical conditions of ignition and extinction, etc.
Both approaches to the study of the combustion process – at an infinitely high or finite reaction rate – are applied in this book to the study of the gas flame. Its choice as an object of study is explained, on the one hand, by the practical significance of the gas flame in itself and as the basis for the flame method of burning any fuel. On the other hand, the commonality The aerodynamic structure of the flame and gas jets 1 and the transport processes within them allows for the effective use of methods and results from the theory of turbulent jets—one of the most developed areas of applied gas dynamics—in flame research [L. I; 10; 221]. This applies to the so-called diffusion flame (combustion of unmixed gases) as well as to the homogeneous flame (combustion of a homogeneous mixture).
In both cases, during intense, high-intensity combustion, the region in which combustion of the main proportion of combustible components occurs occupies a relatively small portion of the flame. In the limit, the combustion zone is so narrow that it can be replaced by the flame front surface. This representation, common for combustion with an infinitely high reaction rate, can be retained, with a certain approximation, for reactions with a finite rate. As a result, with a quasi-heterogeneous process scheme, combustion is considered localized on the flame front surface. The assumption of the absence of chemical reactions throughout the flame volume This significantly simplifies the mathematical description of the process. In some cases, an analytical solution to the problem becomes possible, the final results of which accurately reflect all the most important physical properties of the phenomenon.
We also note other assumptions made in the book. It is primarily focused on the study of an intense free, straight-jet gas flame as applied to the combustion of hydrocarbon fuels in air—in power plants, i.e., at moderate temperatures. This eliminates the need to consider kinetic combustion (or more precisely, oxidation), which is characterized by relatively slow reactions throughout the entire volume of the flame, and to ignore radiation, the influence…
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