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Multiphase reactive systems can exhibit highly dynamic combustion phenomena that could be better understood by using recently developed high-repetition-rate optical diagnostic and imaging approaches. Here, we present an overview of recent activities using high-speed (5 kHz) OH planar laser-induced fluorescence to visualize and make measurements in several multiphase reactive systems. This technique is used to visualize the dynamically changing OH concentration in the gas phase near the surface of solids, liquids, and gels. In addition to gas-phase OH imaging, condensed phases of various solid propellants, gels, and liquids are found to fluoresce when exposed to the laser radiation centered at 283.2 nm. Simultaneous imaging of condensed phases and gas-phase OH radical fluorescence has proven to be particularly useful for various measurements, and several examples are presented.

An important stage of the development of promising engine and propulsion systems is provision of an effective process of hydrocarbon fuel combustion. There are many publications with numerical and experimental data on combustion of various gaseous hydrocarbons under laboratory conditions, but there is a lack of data on effective combustion of hydrocarbons in short combustion chambers with a large number of injectors. Results of systematic experimental studies of natural gas (methane) combustion in a high-velocity subsonic air flow in an air-breathing model combustor with a rectangular cross section are presented in this paper.

The distribution of the dynamic and thermal parameters of a gas in the immediate vicinity of a flame stabilizer (behind a rib and a backward-facing step 3 mm high) are studied. Data on the longitudinal and transverse velocity components, velocity pulsations, and correlations of pulsations in the boundary layer with combustion and without combustion are obtained using the PIV equipment. Temperature is measured with a thermocouple. Flame is visualized in the visible and ultraviolet regions. It is shown that in the flow attachment region near the leading edge of the flame, the gas velocity is close to the normal burning velocity. Heat release is estimated from the results of measurements. The presence of regions of volume and frontal combustion and kinetic and diffusion reaction is established. With increasing distance from the stabilizer, the heat-release rate decreases by more than an order of magnitude.

The enthalpy distribution at the front of one-dimensional flames of homogeneous mixtures of hydrogen, propane, formaldehyde, and methanol with air was numerically investigated. It is shown that the enthalpy distribution is more complex than the classical concepts: the enthalpy can both increase and decrease relative to the initial value. The specific form of the distribution is determined, in particular, by intermediate components formed at the flame front as they are also carriers of chemical energy and transfer it due to diffusion.

The upper and lower flammability limits of silane-oxygen and silane-air mixtures at pressures of 0.05-1.1 atm and temperatures of 350-640 K are found on the basis of Westbrook's detailed chemical kinetics. It is demonstrated that the death of OH radicals has a minor effect on these limits (their stability) within the framework of the Arrhenius kinetic model. The effect of the silane-air mixture composition on the flammability limits is found. It is shown that the behavior of the ultimate temperature of ignition is nonmonotonic as the fraction of silane increases.

The problem of the combustion of a methane-air mixture in a slot burner with adiabatic outer walls is solved. The problem is investigated numerically in a one-dimensional formulation and dimensional variables. The range of existence of stable high-temperature combustion of the methane-air mixture is determined as a function of gas flow rate and methane content in the mixture. The mechanism of failure of stable combustion is determined. The effect of heat transfer of the gas insert with an inner insert on combustion stability is shown.

A model for the process of oxygen cutting of a metal plate is proposed which takes into account heating by external and internal heat sources, heat release from the cutting zone and reducing the thickness of the cutting geometry. The model was implemented numerically. It is shown that the model can describe different cutting modes: surface cutting, severing, and cutting in the kinetic and diffusion regimes. From the calculations results, the temperature field was constructed and the effect of the parameters on the thickness of the workpiece and the shape of the cutting edge was studied. The results are qualitatively consistent with experimental data.

This paper presents the numerical simulation of gasless combustion of a sample as a combination of thermally coupled flat layers consisting of two different chemical compounds, which represent the model of a chemical furnace. The critical combustion conditions are established, depending on the volume ratio of mixtures in the sample or the content of reaction products. The time, velocity, and combustion modes of the layer composition are determined, depending on the volume content of the mixtures, the thickness, and the number of layers. The combustion wave propagation in view of “homogenization” of the sample with layer thickness decreasing at a fixed concentration of the components is considered.

This paper presents the analysis of different hypotheses and models related to the physical nature of the negative erosion effect. The influence of various factors on the emergence of this effect is estimated, and the most significant of them are mentioned. A system of equations for the study of the negative erosion effect is proposed. The new useful properties of the Bulgakov-Lipanov number are found.

The molecular structure of 2-methyl-5-nitro-5-bromo-1,3,2-dioxaborinane and its complex with pyridine is determined by single crystal X-ray diffraction. The structure of the synthesized compounds in the solution is also confirmed by the NMR spectroscopy data, and the conformational preference of their molecules is confirmed by the calculations using hybrid density functional theory.