Home – Home – Jornals – Advanced Search

The effect of thermal expansion on the minimum energy of gas spark ignition is studied using a mathematical model of spark ignition. It is shown that the thermodiffusion model of gas spark ignition underestimates the minimum spark energy by more than a factor of two. The dependence of the minimum spark ignition energy on the Damköhler number is studied, which characterizes the ratio of the flame propagation velocity to the speed of sound in a gas.
Key words: fuel gas, spark, thermal expansion, minimum spark energy.

The effect of vortex formation and the role of mixture flow rate in the excitation and sustenance of the self-oscillatory combustion regime of a kinetic singeing flame was studied experimentally. Using holographic interferometry and the Mies dispersion method, it is found that in the boundary layer at the burner exit, vortices arise periodically, which interact with the flame front to change the flame surface area and the heat release rate. It is shown that the main feedback mechanism is periodic vortex formation, and the occurrence of concentration regions of excitation and silence is related to the change in the number of waves falling on the flame height. It is found that in combustion of oxygen-rich fuel-air mixtures, acoustic oscillations arise at higher harmonics. .

A review of literature data is presented on experimental and theoretical investigations of carbon and solid-fuel gasification in various gas media at high temperatures (up to 1373 K). Methods of experimental and theoretical investigations are described. A theoretical formulation of the problem of nonstationary gasification of carbon is presented. The value of the real kinetic constant of carbon gasification by carbon dioxide is given.
Key words: carbon, carbon dioxide, active areas, nonstationary gasification, kinetic constant.

An approximate mathematical model is constructed and characteristics are calculated of ignition of a reactive plane infinite obstacle by a high-temperature nonstationary axisymmetric supersonic jet of combustion products escaping from the igniter. The approximate model data are compared with the results of numerical calculations using the system of equations of motion of an ideal gas, nonstationary equations of heat conduction and chemical kinetics, and conditions of conjugate heat exchange at the "gas

It is shown that the qualitative behavior of combustible porous substances under conditions of forced filtration can be principally different: self-accelerating explosionlike increase in temperature (ignition) or smooth increase in heating without noticeable specific features. Sets of parameters determining the type of behavior are determined. The critical flow rate of the gas is calculated as a function of the layer thickness. Induction periods are determined.
Key words: ignition, filtration combustion, induction period, mathematical simulation.

An experimental method for studying the combustion of porous specimens under non-one-dimensional filtration of a gaseous reagent is proposed. Propagation of a surface-combustion moving normally to the gas-permeable lateral surface of a specimen was observed in situ for the first time. When the surface fronts meet at the center of the specimen, the temperature increases, which explains previous experimental results.

Investigation was performed of the effect of sample density and the diameter of a coaxial hole in Ti + B based cylindrical samples on combustion rate, relative elongation, and the macrostructure of the products formed. The mechanism of samples fracture due to excess pressure of impurity gases is proposed. It is shown that on parametric diagrams "density

The paper reports a solution of the inverse and direct problems of high-temperature synthesis of intermetallide Ni₃Al by thermal shock. The results obtained are necessary for predicting the kinetics of high-temperature synthesis of intermetallide Ni₃Al and its melts.

Mathematical simulation of the structure of metallized heterogeneous condensed mixtures is performed. Evolution of a system of aluminum particles is studied in the case a heat wave passes over the mixture. It is shown that rapid heating of a heterogeneous condensed mixture forms a system of "clusters" of contacting aluminum particles, which may sinter to form a porous system that melts and disperses into individual droplets with further heating under the action of surface-tension forces. After coalescence, these droplets form agglomerates. The structure of "clusters" of contacting particles is studied, and the mean-mass size of metal particles is determined as a function of dispersion of the components and their concentration in the heterogeneous condensed mixture. It is shown that contacting aluminum particles in the heterogeneous condensed mixture form fractal-like structures, which may play a significant role in the course of combustion of the mixture.

The reaction mechanism and kinetics of self-propagating high-temperature synthesis in a Ti₅Si₃ system are experimentally studied. The Langmuir probe and optical spectroscopy are used to determine the composition and degree of ionization of the gas phase formed due to the combustion-induced degassing of impurities. The propagation of the combustion wave is shown to be accompanied by ionization of released gases, both the ion concentrations and electron temperatures being determined. Through a comparison between the data obtained and spectroscopic data, the ion species are identified.