Stochastic models of particle motion in a turbulent flow and their application for calculating internal flows

This paper considers issues connected with the construction and numerical realization of stochastic models of motion and scattering of condensed impurity particles in a turbulent flow based on the integration of a Langevin-type equation. The proposed model is used to calculate the turbulent flow of a low-concentration gas suspension in a channel with permeable walls. Calculations are performed for various values of the injection rate, sizes of particles, and the conditions of their introduction into the channel. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 3, pp. 136–147, May–June, 2007.     

Use of equations for transfer of particle pulsation characteristics for calculating two-phase flows in the stabilized section of a tube

A stationary isothermal system of equations defining the behavior of a two-phase rising flow in the region of steady motion of a gas suspension in an axially symmetric channel has been developed. The equation of motion of the carrying medium is closed using a one-parameter model of turbulence, and the equation of momentum transfer in the dispersed phase is closed with the use of the equations for the second, third, and fourth moments of the pulsation velocities of the particles. The main mechanisms of two-phase turbulent flows were numerically investigated. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 4, pp. 99–109, July–August, 2007.     

Unsteady wave flows of a gas suspension with account for phase changes

A system of equations of unsteady motion of a gas suspension with account for heat and mass transfer is presented. As a result of the computational experiment, the effect of the gas vibrations at the channel inlet on the motion of the gas suspension and the rate of heat and mass transfer is studied. Specifically, it is shown that, in the considered parametric region, the gas vibrations enhance the interphase heat and mass transfer. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 3, pp. 487–492, May–June, 2000.     

Investigation of the Hydraulic Resistance of a Combined Dust Collector

A new structure of a combined dust collector, in the unified energy field of which suspended particles are separated in interacting swirling flows, with subsequent aftercleaning of the gas by filtration has been developed. The hydraulic resistance of the combined dust collector has been investigated. The change in the pressure loss as a function of the total rate of flow of the gas in the apparatus and the flow-rate ratio has been determined. The dependence for calculation of the hydraulic resistance of this dust collector has been obtained. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 4, pp. 158–162, July–August, 2005.     

Gasdynamic stimulation of combustion of lean fuel mixtures. 1. experimental study

We studied combustion modes experimentally for a lean fuel mixture of propane-air, including combustion of a quiescent mixture, combustion with annular gas swirling, and combustion stimulated by the jets of a burning gas that are injected into the combustion chamber (pulsed jet combustion — PJC). It is shown that, in providing a maximum combustion rate, the PJC mode has an obvious advantage in initiation of combustion of extremely lean fuel mixtures over other gasdynamic combustion modes. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 2, pp. 302–308, March–April, 2000.     

Wave motion of porous particles in a pulsating gas flow in the presence of heat and mass transfer with deepening of the evaporation zone

Based on numerical solution of the dynamics equations of a monodisperse gas suspension with allowance for the interphase forces of aerodynamic drag, virtual masses, and the forces caused by nonstationary effects around particles, the influence of different forms of low-frequency harmonic and anharmonic oscillations of the gas on the motion of porous particles in the presence of heat and mass transfer accompanied by deepening of the evaporation zone has been investigated. The dependences of the solid-phase motion, kinetics of evaporation-zone deepening, and heat and mass transfer on the parameters of gas oscillations have been established. It is shown that on removal of free moisture, oscillations at certain parameters lead to enhancement of interphase heat and mass transfer. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 5, pp. 11–19, September–October 2006.     

Dynamics of magnetophoretic separation of a suspension of slightly magnetic microparticles in a high-gradient field of a magnetized rod

A macroscopic model of the process of magnetophoretic separation of slightly magnetic particles from a suspension under the action of a high-gradient magnetic field with account for the particle size is proposed. The mechanisms of separation of dia- and paramagnetic particles from a narrow fluid layer in an inhomogeneous field of a magnetized rod have been investigated. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 2, pp. 221–226, March–April, 2009.     

Hydrodynamic instability of a suspension of spherical particles through a branching network of circular tubes

A numerical method is presented for computing the unsteady flow of a monodisperse suspension of spherical particles through a branching network of circular tubes. The particle motion and interparticle spacing in each tube are computed by integrating in time a one-dimensional convection equation using a finite-difference method. The particle fraction entering a descendent tube at a divergent bifurcation is related to the local and instantaneous flow rates through a partitioning law proposed by Klitzman and Johnson involving a dimensionless exponent, q ≥ 1. When q = 1, the particle stream is divided in proportion to the flow rate; as q → ∞, the particles are channeled into the tube with the highest flow rate. The simulations reveal that when the network involves two or more generations, a supercritical Hopf bifurcation occurs at a critical value of q, yielding spontaneous, self-sustained oscillations in the segment flow rates, pressure drop across the network, and particle spacing in each tube. A phase diagram is presented to establish conditions for unsteady flow. As found recently for blood flow in a capillary network, oscillations can be induced for a given network tree order by decreasing the ratio of the tube diameter from one generation to the next or by decreasing the diameter of the terminal segments. The instability is more prominent for rigid than deformable particles, such as drops, bubbles, and cells, due to strong lubrication forces between the tightly fitting particles and tube walls. Variations in the local particle spacing, therefore, have a more significant effect on the effective viscosity of the suspension in each tube and pressure drop required to drive a specified flow rate.     

Effects of surface dispersion forces on the flow of a low-density gas in a thin capillary

The paper discusses the flow of a low-density gas in a thin circular capillary with allowance for the dispersion interactions of the gas molecules with the capillary walls. The gas flow rate at the exit is determined. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 53–56, March, 1998.     

Influence of the addition of hydrogen and of a synthesis gas on the characteristics of the process of combustion of gasoline-air mixtures under conditions typical of internal combustion engines

The influence of the addition of hydrogen and of a synthesis gas on the basic parameters of combustion of gasoline-air fuel mixtures is investigated theoretically. The possibility of feeding gasoline internal combustion engines with lean fuel mixtures with a concentration of 5–10 vol.% hydrogen is shown; this will greatly improve their ecological purity. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 4, pp. 23–28, July–August, 2006.     

Separation curves of a flow classification apparatus of finite length

A simplified model of operation of a flow classification apparatus of finite length for the case of a low-concentrated suspension has been analyzed. An analytical and numerical analysis of the behavior of the separation function has been made. Particular emphasis has been placed on such characteristics of classification as the size and sharpness of separation. A self-similar solution for the concentration of particles in each phase has been obtained and compared to the numerical solution. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 3, pp. 171–178, May–June, 2006.     

Experimental investigation of peat ignition and combustion regimes

A new (flame) regime of peat combustion in an air flow has been experimentally investigated. It has been established that the rate of combustion of a peat depends on its density and moisture content, which makes it possible to refine the mathematical model of a peat fire. The mechanism of catalytic peat combustion was determined. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 6, pp. 86–89, November–December, 2007.     

Unit for automatic calibration of gas flow rate controllers

A unit is described for automatic calibration of gas flow controllers, within which there is a reference flowmeter device ERU-0.5, making it possible to measure gas working medium flow rates of 0.01–0.5 cm³/sec with a total error of ± (0.3–0.7)%. The operating principle of the construction, a procedure for determining gas mass flow rate, the main parameters of the flow rate device, and measurement errors are considered.     

Statement of boundary and conjugation conditions for problems of heat transfer in granular beds on the basis of a two-temperature model

Physically justified boundary and conjugation conditions for problems of heat transfer in infiltrated granular beds have been formulated within the framework of the two-temperature model that takes into account the absence of interphase interaction at the boundaries. It is shown that the classical Danckwerts conditions are applicable to a gas. The problem of filtration cooling of a heat-generating granular bed over which there is an inert bed (pile-up) has been solved in a new statement. The dependence of the pressure drop in a granular bed on the mass flow rate of the gas is established. A formula to calculate the maximum temperature of particles is obtained. The region of applicability of the one-temperature model is determined. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 6, pp. 98–106, November–December, 2006.     

Mathematical modeling of turbulent combustion of hydrogen in a boundary layer

Turbulent flow in a boundary layer with injection of hydrogen through a permeable plate into an external air flow is modeled. To calculate turbulence characteristics the Lam-Bremhorst modification of the k-ε model is employed. Calculations are made both with and without account for the non-unity of the Lewis number. In determining the concentrations of the intermediate and end combustion products and the temperature the assumption of chemical equilibrium is made. The obtained distribution of turbulent pulsations allows the conclusion of flow laminarization under combustion conditions to be made. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 1, pp. 86–91, January–February, 1998.     

Gas flow through a porous heat-releasing medium with allowance for the temperature dependence of gas viscosity

The gas flow through a porous heat-releasing medium is considered. It has been noted that account for the temperature dependence of the gas viscosity strongly influences the solution: the gas flow rate markedly decreases and a stronger heating occurs. Analysis of the flow of a gas with a temperature-dependent viscosity by the Sutherland formula has revealed two steady-state cooling regimes — stable and unstable ones. It has been shown that the possibility of the steady-state regime is determined not only by the problem parameters but by the initial conditions as well. The transient process from the state of rest in the absence of heat release to the state of the regime of induced filtration upon instantaneous switching-on of heat input is described. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 1, pp. 35–40, January–February, 2006.     

Instability of plane Couette flow of two-phase liquids

The stability of plane Couette flow of a disperse liquid (gaseous or liquid suspension) is investigated. It is shown that in contrast to the flow of a pure liquid (gas), above a certain threshold particle mass density, this flow begins to become unstable to infinitesimal perturbations. Pis’ma Zh. Tekh. Fiz. 24, 76–80 (March 12, 1998)     

Increase in processing flue gas flow rate while maintaining the fluidization state and filtration performance in a low-temperature continuous regeneration filter using a fluidized bed

To increase the processing gas flow rate in a fluidized bed filter, the effects of superficial velocity and fluidization state on PM filtration and combustion were examined by experiments using large bed particles (710 μm). The fluidization state at 710 μm was measured by image analysis and recurrence plot, and the superficial velocities as experimental conditions were determined to obtain almost the same fluidization state and filtration efficiency as those for small bed particles (420 μm) in previous studies. The BET-surface area of 710 μm is slightly larger than that of 420 μm, and the amount of potassium catalyst doped on large bed particles is comparable to that at 420 μm. The gas phase velocity is increased by increasing the processing gas flow rate, and the contact probability between PM and oxidizer increases. The PM combustion reaction is significantly promoted owing to the effects of the potassium catalyst and the increase in the gas phase velocity, and the minimum continuous regeneration temperature is 30 °C lower than that at 420 μm. As a result, fluidized bed filters using large bed particles can be operated in continuous regeneration mode at a bed temperature of 320 °C while maintaining a filtration efficiency of 100%.     

Investigation of the process of diamagnetic particle separation in a high-gradient ordered-structure magnetic field

On the basis of the model of a flow-type magnetic filter with a transversely magnetized ordered system of long ferromagnetic rods of rectangular cross section, the process of high-gradient magnetic separation of microscopic diamagnetic particles (potato starch granules of sizes 8–30 μm) from a liquid suspension has been investigated. The registered laws of change in the concentration and size distribution of particles at the suspension outlet from the filter agree with the theoretical conclusions obtained from the analysis of the magnetic field structure and thecharacter of the particle motion in the filter volume.