Stability of Calcium Chloride in the Air–Steam Gasification of Solid Fuel in Filtration Mode

The emission of HCl from calcium chloride during the air–steam gasification of solid fuel in the filtration combustion mode was studied. The limiting amounts of HCl released into the gas phase under real conditions of a shaft kiln gasifier were estimated. It was shown that the most important factors responsible for the stability of CaCl₂ are the humidity of an oxidant gas and the process temperature.     

Regimes of the Combustion of Organic Coal–Water Fuels

The results of an analysis of the combustion behavior of the drops of organic coal–water fuels (OCWFs) prepared based on the flotation products (cakes) of the enrichment the coal of five grades (longflame, gas, coking, low-caking, and lean coals) and two petroleum products (petroleum residue and spent turbine oil) are presented. The experiments were performed under the conditions of the stationary fastening of an OCWF drop on the junction of a quick-response thermocouple in a flow of heated (from 500 to 1000°C) air. The following three combustion regimes were revealed for all of the test OCWF compositions: stepwise regime with slow heating (smoldering), intense gas generation regime with the boiling of liquid fuel components (boiling), and regime with a distinct tear-off zone of gas flow (torch). It was shown that the occurrence of the above combustion behaviors substantially depends on the characteristics of the OCWF components: the ash content and the yield of volatile substances of coal cakes and the boiling points and the ignition and combustion temperatures of the petroleum products used. Based on the results of the experiments, the ranges of air temperature changes characteristic of each of the three combustion regimes of fuel suspensions were established.     

Analysis of Nitrogen‐Oxide Formation Mechanisms in Filtration Combustion of Methane–Air Mixtures

The kinetics of nitrogenoxide formation under conditions of filtration combustion of lean and rich methane–air mixtures is analyzed. Intense interphase heat exchange in the wave of filtration combustion of gases leads to a drastic decrease in the gas residence time in the hightemperature region and also to a decrease in the maximum temperatures in the reaction zone. As a result, the processes of filtration combustion of gases are characterized by reduced emission index of nitrogen oxides as compared to diffusion flames. Under these conditions, the thermal mechanism does not make any significant contribution to NO formation, and the dominating channels are the NNH channels for lean mixtures and the Fenimore mechanism for rich mixtures. Nitrogen oxides in lean mixtures are mainly represented by NO and N₂O, whereas nitrogencontaining components HCN and NH₃ are typical of rich mixtures. NO decomposition in rich mixtures occurs in afterburning reactions with participation of HCCO, CH₃, and CH₂ radicals.     

Combustion and Heat Properties of Lignin–Containing Fuels

Results of studying the combustion process of pellet fuels produced on the basis of obsolete gun powder and lignin are described. The temperatures of diffusion combustion of the flame and coke of pellet fuels and the linear velocities of flame and flame–free stages of combustion are determined. A model is proposed, and calculation results for the radiant component in the overall balance of combustion heat of lignin–containing fuels are presented.     

Mathematical Modeling of the Combustion of an Overfueled Aluminum–Air Mixture Based on the Nonequilibrium Thermodynamics of the Process

This paper presents the results of mathematical modeling of the combustion of flow of a multifractional suspension of an aluminum powder in air taking into account the nonequilibrium nature of the process. The calculations were performed for air-to-fuel ratios α = 0.1–0.5. Time dependences of thermodynamic parameters, the completeness of metal particle combustion, and the relative residence time of the fractions in the flow were obtained. The adequacy of the nonequilibrium model for describing thermodynamic processes was validated by comparing with the equilibrium model for time tending to ∞. The necessity of taking into account the formation of Al₂O suboxide present in the range of the air-to-fuel ratio is analyzed and proved. The need to include nitriding reactions in the mathematical modeling for 0.1 ≤ α < 0.4 is shown by comparing the results of calculations based on equilibrium and nonequilibrium thermodynamics.     

Filtration–Diffusion Combustion Limit of a Titanium Powder in Nitrogen upon Degassing

The propagation of the filtration—diffusion combustion front deep in a bulk of titanium powder in a nitrogen medium is studied experimentally. The dependence of the combustion–propagation depth on the height of a fill of titanium powder and the pressure of gaseous nitrogen, the effect of degassing impurities on the limit, and some specific features of combustion are revealed. A model of the process by means of which a formula for estimation of the burning–out depth of the fill is derived is proposed.     

Adsorption Behavior of Trimethylolpropane-Dehydroabietic Acid Ester at the Air–water Interface

A novel amphipathic trimethylolpropane-dehydroabietic acid ester was successfully prepared with acyl chloride method. Various analytical techniques such as liquid chromatography–mass spectrometry, Fourier transform infrared spectrometry, proton and carbon nuclear magnetic resonance spectroscopy were employed to evaluate the chemical structure of the ester. The surface properties of the ester were investigated by surface tension and resonance light-scattering techniques. The surfactant molecules are adsorbed at the water–air interface in different adsorption states, i.e., state 1 and 2. The dynamic adsorption behavior was studied by combining experimental results and a reorientation model. The molar fraction of solvent decreased, while the molar fraction of surfactant molecules increased with increasing ester concentration at the surface layer. The adsorption value of state 1 presented a unimodal shape and the adsorption value of state 2 presented an s-shape with the increase in surface pressure. The free energy of adsorption is ?36.06 kJ mol^?1, more negative than the free energy of micellization (?29.69 kJ mol^?1), it is actually easier for surfactant molecules to adsorb on the air–water interface.     

Synthesis of the Ni–Al–C Composite with Multilayer Carbon Nanostructures by an Electrothermal Explosion under Pressure

Combustion, Explosion, and Shock Waves - A composite material based on the Ni–Al–C system is synthesized by the method of an electrothermal explosion at a pressure of 96 MPa. During the...     

Estimation of the Fireball Size in an Ethyne–Air Cloud Explosion

A gas explosion accident is often followed by a serious fire. In order to effectively prevent fire induced by a gas explosion accident, it is necessary to have some knowledge of the related explosion processes. The subject of the present study is to examine deflagration behaviors beyond the original cloud of the ethyne–air mixture and the fireball size in an ethyne–air explosion by means of numerical simulations. The explosion overpressure, flow velocity, and reaction rate distribution in an ethyne–air explosion are obtained. The peak explosion overpressure is found to reach its maximum beyond the original cloud for ethyne–air mixtures with ethyne concentrations greater than 13% (by volume). The explosion pressures beyond the original cloud may be higher than those within the cloud for these ethyne–air mixtures. The ratio of the combustion range to that of the original cloud is 1.4–2.7 in the radial direction on the ground and 1.5–4.0 along the axis of symmetry perpendicular to the ground.     

Effect of the Fuel Type on the Characteristics of Air‐Breathing Engines

Experimental studies of airbreathing engines operating on gaseous and liquid fuels are analyzed. It is shown that, for flight conditions with a Mach number 5 at the ground level, the results on operation and thrust–economic characteristics, which were obtained for hydrogenpowered engines, may be used directly in development of the ducts of hypersonic airbreathing engines operating on liquid organoborn fuels.     

Effect of the Molecular Structure on the Adsorption Properties of Cationic Surfactants at the Air–Water Interface

The surface activity and thermodynamic properties of adsorption at the air–water interface of two series of cationic surfactants based on isourea: the O-dodecyl-N,N′-diisopropylisourea hydrochloride, hydrobromide, and hydroiodide and the O-tridecafluorooctyl-N,N′-diisopropylisourea hydrochloride and hydrobromide were studied. The effect of structural parameters as the nature of the halide counter ion and the nature of the non-polar chain on the surface activity and thermodynamic properties of adsorption were investigated. The surface parameters, the maximum surface excess concentration (Γ _max), the minimum area per molecule (A _min) at the aqueous solution-air interface, effectiveness of surface tension reduction (π_CMC), and efficiency of surface tension reduction (pC ₂₀) were estimated. The standard Gibbs free energy of adsorption, (ΔG°_ads) change has been calculated at different temperatures.     

Calculation of the Filtration Coefficient and the Flow Resistance of a Fibrous Filtration Membrane in Terms of the Hausdorff–Besicovich Dimension

The filtration coefficient and the flow resistance are calculated for filtration membranes made from fibers whose length and diameter constitute an infinitely decreasing geometric progression. These parameters can be described in terms of the Hausdorff–Besicovich dimension and are optimum when the membrane has a fractal structure.     

Combustion synthesis of TiC–NiAl composite by induction heating

The aim of this work was to develop a new process for the synthesis of TiC and NiAl/TiC composite in which the combustion reaction was ignited using a high frequency induction heater. High density, two-layer TiC–NiAl composites were also produced using this process. Temperature profiles during synthesis were measured with an IR thermometer and a high resolution thermal image camera was used to monitor the reaction process. Phase transformation was investigated using XRD and SEM was used to characterize the microstructure of the synthesized composites. The mechanical properties of the products were evaluated by measuring hardness. The results show that the reaction was complete and that stoichiometric products of NiAl and TiC were produced. The properties of NiAl/TiC composites were found to be functions of composition and processing parameters. The reaction mechanism was analyzed using temperature monitoring, thermodynamic analysis and microstructure investigation.     

Experimental Study of the Disperse Composition of Condensed Products of Aluminum‐Particle Combustion in Air

The particle shape and structure and also the disperse composition of condensed products of combustion of ASD1, ASD4 and ASD6 aluminumbased powders in air with oxidizertofuel ratios of 0.12–0.4 and initial pressures of 0.05–0.30 MPa are examined. The mass of submicron particles of aluminum oxide amounts to 90% of the total mass of condensed combustion products. The mean mass diameter of particles is 0.15–0.18 m and increases with increasing pressure. Under atmospheric pressure, the initial disperse composition of aluminum powders and the proportion between the components in the combustor volume have little or no effect on the disperse composition of the condensed phase. A comparative analysis is performed of the disperse composition of condensed phase particles formed due to aluminum combustion in various propellant mixtures and various combustors. It is shown that the main factors affecting the disperse composition are the type of the propellant mixture, the gasdynamic combustion process, and the conditions determining the interaction of aluminum particles with each other and with the gas phase.     

Transformation of the Thermal Structure of the Combustion Wave and Morphology of the Combustion Products of the SiO2–Al(Zr)–C System near the Extinction Limit

The combustion of the SiO₂–Al(Zr)–C system is studied near the extinction limit. Temperature distribution over the combustion zone is obtained using the thermocouple procedure. It is shown that in combustion of samples with diameter not exceeding 8 mm, thermal losses give rise to a temperature gradient over a section of the sample, which transforms the thermal structure of the combustion wave and leads to inhomogeneity of the end product. New data on the formation mechanism of the reaction products are given.     

Spatial Structure of a Reacting Turbulent Swirling Jet Flow with Combustion of a Propane–Air Mixture

Results of an experimental study of the spatial structure of a reacting flow during combustion of a propane–air mixture in a turbulent swirling jet escaping into atmospheric air are presented. The fuel-to-air equivalence ratio is φ = 0.7, and the Reynolds number of the jet is Re = 5 · 10³. The time-averaged spatial distributions of velocity, local density, and concentrations of the main species of the gas mixture are measured in low-swirl and high-swirl flows. In both cases, the flame front is stabilized in the internal mixing layer formed by the axial region of jet retardation, where hot combustion products are concentrated. In a high-swirl flow, the temperature distributions in the cross section y/d = 0.5 show that the region with the maximum temperature of the gas is located at the periphery of the central recirculation zone. Moreover, in the case of a high-swirl flow, there exists a recirculation zone at the axis, and the CO₂ concentration is twice higher than in a low-swirl jet. The opposite situation is observed for O₂.     

Ignition and Combustion of Aluminum–Air Suspensions in a Reactor for High-Temperature Synthesis of Alumina Powder

A method for flame stabilization in a reactor for synthesis of metal oxides is developed by analyzing combustion of dispersions of metal powders. An experimental reactor designed to implement this method is described. Ignition and combustion of commercial aluminum powders (ASD-1 and ASD-4) in air were studied, and their reliable ignition and stable combustion in the reactor combustion chamber were confirmed. It is shown that efficient combustion of an aluminum–air mixture depends on powder dispersity, flow mixing conditions, and combustion chamber pressure. Key words: aluminum, powder, suspension, flame, stabilization, combustion, synthesis, oxide.