Deformation of a water shell during free fall in air

The basic regularities of the change in the shape and sizes (the initial volume is 0.05–0.5 L) of a water shell are singled out in its deformation during free fall in air from a height of 3 m. The 3D recording of the basic stages of deformation (flattening of the shell, nucleation, growth, and destruction of bubbles, formation of the droplet cloud) is carried out using high-speed (up to 10⁵ frames per second) Phantom V411 and Phantom Miro M310 video cameras and the program complex Tema Automotive (with the function of continuous tracking). The physical model of destruction of large water bodies is formulated at free fall with the formation of the droplet cloud.     

Effect of the thermophysical properties of the material of a local energy source on conditions and characteristics of ignition of metallized composite propellants

Solid-phase ignition of metallized composite propellants by a single particle heated to a high temperature under conditions of an ideal thermal contact has been numerically studied. The effect of the thermophysical properties of the material of a local energy source on the conditions and characteristics of ignition of composite propellants has been analyzed. It has been found that sources with a high heat storage capacity exhibit shorter ignition delay times for metallized propellants (by 10–60%) and lower initial temperatures required to initiate the combustion process (by 170 K). In addition, it has been found that the presence of particles of metals (boron, aluminum, magnesium, lithium) in the propellant composition leads to an increase in the effective thermal conductivity of the propellant. The cumulative effect of the thermophysical properties of the materials of the “particle heated to a high temperature–metallized composite propellant” system leads to an increase in the ignition delay times (by 25–65%) and the heat penetration depth of the near-surface layer of the propellant (by 25–40%) at the time of combustion initiation compared with metal-free compounds.     

Numerical study of ignition of a metallized condensed substance by a source embedded into the subsurface layer

A numerical simulation of the ignition of structurally heterogeneous condensed material by a small single particle heated to high temperature, a typical limited heat content source of is performed within the framework of a solid-phase ignition model. The effect of the depth of embedment of the heated particle into the subsurface layer of the metallized material on the integral characteristics of the ignition is examined.     

Activity of copper–cerium–zirconium catalysts in oxidation of hydrogen

We have studied the catalytic properties in oxidation of hydrogen for copper–cerium oxide systems deposited on supports obtained by calcination of yttrium-stabilized zirconium dioxide at 300–1000 °C. We have shown that the catalytic activity of the samples obtained depends on the specific surface area of the original supports and the amount of reduced copper within the composition of the catalyst. In samples whose support has high specific surface area, the content of reduced metallic copper is greater and the catalytic activity is higher.     

On the scale of “simultaneous” influence of several “hot” particles on the conditions of heat and mass transfer at ignition of liquid condensed substance

Processes of heat and mass transfer at igniting a film of a typical liquid burning substance—kerosene—by several small-size hot particles are investigated numerically. Characteristics of ignition by several particles are compared with similar parameters in a system of single hot particle-liquid fuel film-air. It is found out that a value of the interparticle distance affects characteristics of the process. Three possible regimes of ignition in a system of two hot particles-liquid fuel film-air, depending on the distance between the heat sources, are revealed.     

Heat and mass transfer at gas-phase ignition of grinded coal layer by several metal particles heated to a high temperature

Characteristics of gas-phase ignition of grinded brown coal (brand 2B, Shive-Ovoos deposit in Mongolia) layer by single and several metal particles heated to a high temperature (above 1000 K) have been investigated numerically. The developed mathematical model of the process takes into account the heating and thermal decomposition of coal at the expense of the heat supplied from local heat sources, release of volatiles, formation and heating of gas mixture and its ignition. The conditions of the joint effect of several hot particles on the main characteristic of the process–ignition delay time are determined. The relation of the ignition zone position in the vicinity of local heat sources and the intensity of combustible gas mixture warming has been elucidated. It has been found that when the distance between neighboring particles exceeds 1.5 hot particle size, an analysis of characteristics and regularities of coal ignition by several local heat sources can be carried out within the framework of the model of “single metal particle / grinded coal / air”. Besides, it has been shown with the use of this model that the increase in the hot particle height leads, along with the ignition delay time reduction, to a reduction of the source initial temperatures required for solid fuel ignition. At an imperfect thermal contact at the interface hot particle / grinded coal due to the natural porosity of the solid fuel structure, the intensity of ignition reduces due to a less significant effect of radiation in the area of pores on the heat transfer conditions compared to heat transfer by conduction in the near-surface coal layer without regard to its heterogeneous structure.     

The influence of radiation heat exchange on characteristics of liquid fuel ignition by a heated metal particle

A complex of interrelated heat-mass transfer processes at gas-phase ignition of a typical liquid fuel by a hot metal particle immersed partially into a liquid is investigated numerically. The scale of influence of the radiation heat exchange at particle—liquid fuel and particle—gas—vapor mixture interfaces is found. Conditions under which the impact of this factor can be neglected are determined.     

Comparative Analysis of Interaction Modes of Two Droplets and of a Large Population in an Aerosol Cloud

Doklady Physics - A comparative analysis of experimental results obtained by various investigators using two different experimental approaches is presented: the phenomenological approach (the...     

Characteristics of “Bounce” of Interacting Water Droplets

Technical Physics - We report on the results of experiments devoted to analysis of conditions and characteristics of “bounce” (approach and interaction through a gaseous buffer...