Effect of the Heating Scheme of Heterogeneous Droplets on the Characteristics of Micro-Explosion Fragmentation

Doklady Physics - According to experimental results, a comparison of sizes of child droplets after micro-explosion fragmentation of water–Diesel droplets is conducted. Convective, conductive,...     

Initiation of organic coal–water fuel droplet burning in a vortex combustion chamber

Using a test bench the main part of which is a vortex combustion chamber, characteristics describing the initiation of burning of solitary droplets of a typical organic coal–water fuel (OCWF) are established. The oxidizer temperature varied in the range of 600–850 K. The linear motion velocity of the oxidizer in the vortex chamber was about 3 m/s. The configuration of the chamber and parameters of the air flow provided a stable regime of floating for droplets with a size (radius) of about 0.5 mm. The analysis results show that the intensity of initiation of OCWF combustion under conditions of processes occurring in boiler furnaces is significantly (by a factor of 2–4) higher than for droplets that are immovably fixed or freely float in the heated air flow.     

The High-Temperature Evaporation of Water Droplets in a Gaseous Medium

Technical Physics - The results of experimental investigations of the processes of water droplet evaporation upon heating in a gaseous medium at temperatures of 500–1100 K have been...     

3D problem of heat and mass transfer at the ignition of a combustible liquid by a heated metal particle

A nonlinear nonstationary 3D problem of heat and mass transfer at gas phase ignition of a combustible liquid spread on the surface of a solid body by a metal particle heated to a high temperature is solved. This is done within the framework of a model taking into account the heat conduction and evaporation of the liquid, the diffusion and convection of the combustible vapors in the oxidizer medium, the crystallization of the ignition source, the kinetics of the processes of evaporation and ignition of liquids, the dependence of the thermophysical characteristics of the interacting substances on the temperature, and the moisture content of the oxidizer—air. The dependences of the ignition delay time of the liquid on the temperature and sizes of the heating source are established. Limiting values of the temperature and particle sizes at which the ignition conditions take place are determined. The influence of the air humidity on the inertia of the process being investigated is analyzed. A comparison of numerical values of typical parameters of the process under investigation for 2D and 3D models is performed.     

Mechanism of heat transfer in heterogeneous droplets of water under intense radiant heating

Thermocouple measurements of temperature have been performed at three main points of heterogeneous water droplet–high-temperature gases system: on the surface and in the depth of a solid inclusion, as well as on the free surface of the water droplet. Investigations have been carried out for water droplets of an initial volume of 5–15 μl with single inclusions of cubic graphite particles of a typical size of 1 mm. The gas temperature varied from 700 K to 1200 K, which corresponds to the main practical applications: thermal purification of water from solid and liquid impurities, fire extinguishing, treatment of heat-loaded surfaces of power equipment, etc. A hypothesis about the dominant role of radiant heat transfer in vaporization within heterogeneous water droplets has been grounded. It has been shown that in a short period (a few seconds), the surface temperature of an opaque solid inclusion within a droplet can reach the boiling point of water. A significant change in the optical properties of water with increasing temperature has been revealed, i.e., water became partially transparent to the infrared radiation. Presence of an opaque heterogeneous inclusion enhances this effect due to intensification of the heating of the water film. The heat and mass transfer characteristics obtained in the experiments were used for designing a model that takes into account the radiative properties of water film and adequately reproduces the results of thermocouplemeasurements. Based on the findings of the investigations, a conclusion has been formulated that models of high-temperature evaporation of water droplets should be developed with due account of changes in the optical properties of water and formation of a vapor buffer layer around inclusions.     

Effect of the nature of the support for copper-cerium oxide catalysts on selective oxidation of CO in hydrogen-rich mixtures

We have studied the catalytic properties of copper-cerium oxide catalysts, supported on zirconium, aluminum, titanium, and manganese oxides, in the reaction of selective oxidation of CO in hydrogen-rich mixtures. We have shown that the high activity and selectivity of catalysts supported on zirconium and aluminum oxides is connected with the presence of (in addition to divalent copper) higher amounts of copper in the (+1) oxidation state in the catalysts. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 2, pp. 119–124, March–April, 2006.     

Ways of increasing yield and flux stability for 14 MeV neutrons

Major physical processes are discussed for a target containing sorbed tritium. Recent research results are classified, and the state of the art is considered on increasing 14 MeV neutron yield and flux stability.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 17–31, May, 1988.     

Synthesis of 15- and 18-membered polythiamacrocylic ligands

Reaction of 1,8-dimercapto-3,6-dithioactane with oxa-, aza-, and thiadihaloderivatives under high dilution conditions in the presence of cesium carbonate, which acts as a template for the condensation reaction, produces 15- and 18-membered polythiamacrocyclic ligands in yields greater than 50%.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 660–662, May, 1989.     

The effect of the conditions for the preparation of iron oxide nanoparticles on their catalytic characteristics in the oxidation of CO

The catalytic characteristics of systems prepared by mechanically mixing iron oxide nanoparticles, produced in the thermolysis of carboxylate complexes at 300–750°C, with aluminum oxide in the oxidation of CO were studied. It was shown that increase in the size of the iron oxide nanoparticles leads to decrease in the catalytic activity of the samples as a result of their different structural and textural characteristics, which change in relation to the synthesis conditions. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 5, pp. 300–305, September–October, 2006.     

Method for estimating the largest Lyapunov exponent for the chaotic regime in chemical reactions

Based on the Belousov-Zhabotinskii reaction in CSFR we observe that the mixing rate decrease in the reaction volume of the mixture to the value ₀ leads to a qualitative change in the nature of the chaotic regime, similar to a second order phase transition. We show that the largest Lyapunov exponent for the system is directly proportional to ₀ ².Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 1, pp. 52–56, January–February, 1992.