Yu. V. Polezhaev

Effect of particle concentration on fluctuating velocity of the disperse phase for turbulent pipe flow

We present the results of an experimental investigation of the fluctuation velocity distributions of solid particles when they move in the downward gas turbulent pipe flow. The glass particles (Stk L ≃ 1) having an average diameter of 50 μm were used as a disperse phase. The average particle mass concentration varied within the range of M = 0 to 1.2. The results obtained showed the particle fluctuation velocity to be strongly dependent on their mass loading. There has been observed an influence of the particle concentration on the significant increasing of their axial fluctuation velocity in the pipe wall region

A Universal Model of Heat Transfer in Systems with Penetration Cooling

Penetration cooling is one of the most intensive methods of regulation of heat transfer, which is explained by the highly developed contact (wetted) surface within a porous matrix and by the significant effect of heat flux reduction upon the injection of coolant into the boundary layer. However, there are serious difficulties in performing theoretical analysis of heat transfer within permeable matrices with filtration of coolant because of the absence of a universally accepted approach to the choice of geometric scale of pore channels and criterion relations for the calculation of the coefficient of internal heat transfer, as well as because of the indeterminacy of the boundary conditions on the internal and external surfaces for the coolant temperature. In this paper, all of these problems are coordinated from a unified standpoint, which enables one to formulate a universal model of heat transfer in permeable envelopes. The results of systematic calculations by the suggested mathematical model are used to reveal and optimize the most important parameters of the system of heat shielding designed for the blades of high-temperature rims of gas turbines.

Modern Problems of Thermal Protection

A brief review of the present state of works on the promising methods of thermal protection of thermally stressed units and assemblies in different branches of technology is given.

Heat Transfer in the Neighborhood of the Stagnation Point under Conditions of Hypersonic Heterogeneous Slip Flow past Bodies

This paper integrates extensive experimental and theoretical data on heat transfer on the surface of blunt bodies subjected to hypersonic heterogeneous flow. The value of the Mach number of the carrier gas flow is varied from 2.4 to 6, and those of the Reynolds number calculated by the diameter of the body subjected to flow, from 104to 106. The mass concentration of solid impurities in the flow does not exceed 3%. When the particle diameter varies from 0.15 to 160 μm, the rate of particle collisions with the body surface varies from zero to 1350 m/s. An analysis of the experimental data helps develop the phenomenological model of heat transfer on the surface of a blunt body in a hypersonic heterogeneous flow.

Influence of thermal conductivity of a material on an unsteady heat removal parameter

In preparing [1] the authors additionally studied the influence of the thermophysical properties of a material on its unsteady breakdown. They found that the unsteady heat removal parameter d0 depends logarithmically on the thermal conductivity.

Model of thermal destruction of material subjected to one-sided heating

The article presents a model of destruction establishing a correlation between the temperature field and the rate of destruction of the material.

Numerical study of the processes of resonance emergence in the experimental set-up of a pulse detonation engine

The results of calculations of the pressure, flow rate, and temperature in the combustion chamber of a pulse detonation engine (PDE) for the conditions realized in the experiment are presented. On the basis of the developed mathematical model, the multiparameter calculations are performed for physical processes occurring in the working path of a PDE. We studied the conditions for the occurrence of oscillations in the PDE combustion chamber. For certain values of the parameters of the set-up, the oscillations have constant amplitude and frequency. These results are in good agreement with the data of other authors. The conditions under which the detonation engine can operate in the pulse mode are also investigated in the paper.

Convective Heat Transfer in Combustors with a Circulating Fluidized Bed

Experimental data on heat transfer in full-scale and model combustors with a circulating fluidized bed are reviewed. A physical scheme and an algorithm are suggested for the calculation of the intensity of heat transfer to a vertical wall subjected to a dust-laden flow.

Effect of internal and surface processes of heat absorption on the heating and destruction of a material

The main factors of heat absorption causing the destruction of the surface of a material are considered. Conditions are investigated under which the maximal energy capacities of the internal and surface processes are achieved.

Evaluating the fracture energy of a material from its heat content

A relationship between the fracture energy of a material and its heat content is established from analysis of literature and experimental data. Simple relations are proposed for evaluating the heat of vaporization and rate of fracture of materials.