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A flat methane-air mixture flame was numerically simulated in a longitudinal electric field at various fuel-to-fuel ratios. A computational code developed in the OpenFOAM based on the reactingParcelFoam solver was used for numerical calculations. The results showed that the predicted value of the ion current correlates with the experimental data. The best agreement is achieved in the lean (φ ≤ 0.8) and rich (φ ≥ 1.3) flames. The greatest discrepancy is recorded for the regime of fuel-air equivalence ratio φ = 0.9. The maximum ion current is achieved at φ = 1.1, which corresponds to the experimental results. The obtained data demonstrate the adequacy of the developed code in predicting the flame current value. Calculation data indicate an increase in CH concentration by 20.5% and O concentration by 2.0% when exposed to an electric field; the interaction of these components is the initiating reaction in the formation of charged particles in hydrocarbon flames.

Stationary perturbations of equations of the boundary layer stability are studied for subsonic and supersonic flow past a plate. For two-dimensional perturbations, the results obtained are in good agreement with existing literature data. Three-dimensional perturbations resembling longitudinal structures are studied for the first time. It is established that the amplitude of boundary layer perturbations of longitudinal velocity and temperature has a bell-shaped form, whose maxima position in the Dorodnitsyn-Howarth variables is conservative with respect to changes in the Mach number, Reynolds number, and wave number along the lateral coordinate. Moreover, the intensity of perturbation attenuation along the longitudinal coordinate and the phase shift of the boundary layer perturbation increase with an increase in the above quantities. The largest phase changes are observed for the lateral velocity.

Percolation theory is widely used to study heat transfer and other kinetic processes in systems with disordered structures. This paper proposes a phenomenological approach combining methods of percolation theory and multifractal analysis to model a percolation cluster in a three-dimensional infinite medium with multifractal properties. Based on the developed model, unambiguous numerical values for topological critical indices and the critical conductivity index were obtained, previously unknown relationships between critical indices were revealed, threshold conditions that separate qualitatively different regimes of system behavior in the scales of correlation length were determined, and a relationship between the systems order parameter and the golden ratio was established, which indicates the universal nature of the identified dependences.

Experimental results on the temperature distribution in a jet of nitrogen flowing from a long pipe into a vacuum under laminar and turbulent flow conditions are presented. A temperature increase downstream was observed under turbulent flow conditions compared to laminar flow conditions. It is concluded that the temperature increase is associated with the turbulent energy relaxation.

Despite numerous studies, many aspects of ignition and propagation of combustion and detonation waves in combustible mixtures remain insufficiently understood, complicating the scientifically sound management of such processes. This paper presents new data on the various stages of ignition and flame front propagation in a flat (two-dimensional) channel of constant cross-section. The experimentally observed main flame instabilities (manifested in the significant non-uniformity and non-stationarity of the combustion front), the phenomenon of flame blowoff (disappearance of glow), and the effect of flame transition to a self-sustaining propagation mode are discussed. Attention is drawn to the problems of the emergence of new ignition sources in the flame front, including explosive micro-sources that facilitate the subsequent transition of combustion to detonation. A number of new features in the physics and dynamics of flame propagation are identified.

Despite extensive research, many aspects of ignition and propagation of combustion and detonation waves in combustible mixtures remain poorly understood, complicating scientifically sound control of such processes. The first part of this paper presented new experimental data on various stages of ignition and flame front propagation in a flat (two-dimensional) channel of constant cross-section. This paper presents results on the little-studied area of combustion wave behavior with changing channel geometric dimensions (so-called flame diffraction). Characteristic processes in the behavior of a turbulent flame as it transitions from a narrow channel to a wide one are established: from flame breakdown and loss of front glow with incomplete combustion of the mixture in a wide channel to the emergence of new explosive microcenters due to the development of expanding flame instabilities and collisions of turbulent flame tongues, leading to the generation of detonation-like waves.

The results of direct numerical modeling of combustion in a cone-shaped methane-air mixture flame directed at a flat, cold barrier are presented. Three cases with different distances between the burner nozzle and the barrier were considered. The study focused on analyzing nitrogen oxide formation in the wall region. It was found that when the barrier was positioned three calibers from the nozzle edge, a recirculation zone with an elevated concentration of nitrogen oxides (NO_x ) forms between the cone-shaped flame front and the cold wall. This increased NOx formation is offset in the downstream wall region.

Using a detailed kinetic mechanism of chemical interaction, the effect of adding ozone (or hydrogen peroxide) and helium as an inert diluent to a stoichiometric hydrogen-air mixture on the detonation wave parameters was numerically studied. It was found that the mole fractions of the additives can be selected such that the detonation wave cell size in the resulting mixture is close to the average cell size in the pure mixture, while the temperature of the detonation products is significantly reduced. It was shown that the introduction of hydrogen peroxide and helium reduces the stability of the detonation wave to disturbances caused by multiple obstacles (barriers) located in the channel, thereby contributing to the wave suppression. Conversely, detonation in a mixture with ozone and helium additives at selected concentrations is found to be more resistant to these disturbances than in the pure mixture.

A microscopic and diffraction study of detonation carbon in the products of benzotrifuroxane-based explosive compositions containing hexogen, octadecanoic acid, and TNT was conducted. Carbon species characteristic of pure benzotrifuroxane were observed in the detonation products of benzotrifuroxane-based compositions with individual benzotrifuroxane granules ranging in size from a few to tens of microns. No such species were detected in the submicron mixture of benzotrifuroxane and TNT.

Wide-range semiempirical equations of state for liquid and gaseous argon, krypton, and xenon are constructed, taking into account evaporation and thermal ionization, based on a modified van der Waals model for mixed substances. The empirical functions that specify the model have a simple form. They contain a small number of free parameters, selected based on the best possible description of the experimental data. A comparison of the model calculation results with experiment up to pressures of ≈1000 GPa and the results of calculations using other models at pressures above 1000 GPa is presented. In the limit of low density and high temperature, the model transforms into an equation of state for a mixture of ideal gases of atoms, ions of all multiplicities, and electrons with a concentration determined by the Saha system of equations.