This paper presents the results of an experimental-theoretical investigation of the evolution of a cloud of aerosol particles in a closed space obtained by the shock-wave method. It has been shown that the prevailing propagation mechanism of aerosol particles of diameter 1-7.5 μm is convective diffusion. For the considered class of aerosols, the effective value of the convective diffusion coeffi cient in a closed space has been determined.Introduction. The laws of aerosol cloud propagation in a closed space are of interest in solving many practically important problems. Among such problems are, for example, dust suppression in coal mines, fi re fi ghting in closed rooms by coolant spraying, air purifi cation and ozonization, photocatalytic neutralization of toxic gases emitted in accidents at enterprises of the chemical industry, as well as by terrorist acts with the use of toxic agents, etc. [1, 2].One effective method for generating an aerosol cloud is shock-wave spraying of a liquid by initiating a charge of a high-energy material (HEM) [3]. Unlike the known methods [4], shock-wave spraying has a number of specifi c features -a short time and a high initial fl ow velocity of the liquid, and the nonstationary and multistage character of the processes of formation and evolution of a cloud of particles.In the present paper, we present the results of the experimental-theoretical investigation and mathematical modeling of the evolution of a cloud of aerosol particles in a closed space obtained by the shock-wave method.Experimental. The shock-wave generator for spraying the liquid is schematically represented in Fig. 1. The generator consists of a case 1, a HEM charge located in the chamber 2, a vessel 3 with the sprayed liquid bounded by membranes 4, and a nozzle hole 6 in the upper cover 5 of the case. Upon initiation of a HEM charge in the chamber, a shock wave is formed and degenerates into a series of resonance acoustic waves, under the action of which cavitation of the liquid with the formation of vapor bubbles occurs. The droplet-bubble jet 7 fl ows out through the nozzle hole under the pressure created by the gaseous HEM combustion products. A primary cloud of particles is formed thereby.To measure the characteristics of the cloud of particles, we used the experimental facility schematically represented in Fig. 2.In the closed chamber 1 of size 2 × 1 × 1 m a shock-wave generator is installed. The structure of the spray cone and the concentration and dispersivity of particles of the sprayed liquid were determined with the use of contactless optical methods. Visualization of the cloud of particles was realized by the method of rapid video fi lming. The concentration and the size distribution function of particles were measured by the method of small angles of the scattering indicatrix and spectral transparency [5]. The radiation from the probing laser 3 through the mirror system 4 and optical windows 5 in the camera arrives, upon interacting with the aerosol cloud, at the radiation detectors 6 located at dista...

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Thermal decomposition of thermoprotective materials based on phenolformaldehyde resin and carbon cloth with different contents of components is studied. Physical and mathematical models for the process are proposed. It is shown that the mass loss in carbon fiber reinforced plastics is determined by thermal degradation of the components and can be described by a generic kinetic scheme with a given set of thermokinetic constants. The mass loss of materials can be predicted by solving a system of ordinary differential equations taking into account the mass ratio of the components in the composite material.Carbon-fiber-reinforced composites have found application in thermal protection of the side surface of landers moving in dense atmospheric layers from intense heat flows. By varying the mass fractions of the polymer binder and the refractory filler in the composites, one can affect the heating and mass-loss processes in the thermoprotective coating and, after an analysis and simulation of the processes in heated carbon fiber reinforced plastics (CFP), predict the inflow of gaseous decomposition products into the boundary layer. The latter seems to be of extreme importance because this inflow affects heat and mass transfer, friction coefficients, and stability characteristics of a flying vehicle following a ballistic trajectory with different angles of attack. Moreover, variation of mass fractions of the components in a composite affects the thermophysical parameters of materials and, hence, the thickness of the heated, reacting, and coke layers of the thermoprotective coating.The high cost of certification and full-scale tests for new materials necessitates generalization of experimental data aimed at developing a technology for production of composite materials with prescribed (predictable) properties. This would substantially reduce the development costs and allow rapid introduction of new compounds into industry.The properties of thermoprotective materials based on phenolformaldehyde resin and carbon cloth were examined in [1][2][3][4].Schneider et al.[1] derived temperature dependences of thermophysical properties of CFPs under static conditions and kinetic parameters of its thermal decomposition process (activation energy E = 81 kJ/mole and preexponent k 0 = 3.15·10 4 sec −1 ) determined from thermogravimetric data by the chemical kinetics equationwhere ρ s and ρ c are the current and final densities of the material, t is the time, T s is the temperature, and R is the universal gas constant. The carbon fiber reinforced plastic contained ≈35% (by weight) of phenolformaldehyde resin and ≈65% (by weight) of carbon cloth.