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Results of numerical simulation of two-dimensional flows of cellular detonation in plane channels in gas suspensions of submicron aluminum particles (0.6 and 0.3   m) in oxygen are presented. Mixtures with homogeneous and heterogeneous concentrations are considered. A previously developed model of reduced kinetics verified on the basis of the detonation velocity dependence on the particle concentration and extended to heterogeneous mixtures is used. The size and character of detonation cells are found as functions of the particle size and concentration. Problems of detonation propagation in channels with transverse concentration gradients and intermittent distributions of concentration are considered.

Results of numerical simulations of mixing, ignition, and combustion of a cold supersonic (М _jet = 1.46) hydrogen jet injected coaxially into an annular supersonic (M _air = 1.86) jet of hot vitiated air expanding into a still space are reported. The simulations are performed within the framework of the ANSYS Fluent 2020 R1 software in a transient two-dimensional axisymmetric approach based on the Reynolds-averaged Navier-Stokes equations supplemented with the k-w SST turbulence model and a detailed mechanism of hydrogen combustion in air. The geometry and simulation parameters are chosen to be those of the experiment of Cohen and Guile (1969), whose data were used for verification of the numerical algorithm. The structure of the reacting jet is studied, and the hydrogen combustion efficiency is evaluated for various values of the jet pressure ratio. The instantaneous, mean, and RMS components of the main gas-dynamic quantities and species mass fractions in the reacting mixture are obtained.

This paper presents the results of a study carried out using numerical simulation of flame front dynamics in a gaseous reacting mixture, including those in the presence of a suspended phase of liquid microdroplets. It is shown that the local effect on the flame front is one of the leading factors determining the development of combustion. Thus, the local dynamic effect of relatively large droplets on the flame front contributes to its curvature, which, in turn, determines the corresponding local acceleration of individual sections of the front. Further unstable growth of such perturbations leads to an integral acceleration of the flame. At the same time, local stretching by the flow in depleted compositions can lead to combustion extinction.

A numerical model for heterogeneous combustion of axisymmetric porous objects has been proposed that allows one to simulate processes under both forced filtration natural convection. The influence of the location of the ignition zone on combustion in a cylindrical porous reactor has been investigated. It has been shown that under forced filtering, the process similar to plane case: the combustion wave moves upward and sideways from the ignition source, completely burning out the solid fuel, while the gas tends to bypass hot zones and flow through colder regions. Under natural convection conditions, as in the plane case, the oxidizer flow into the reaction zone is significantly affected by vortex gas flows that arise in the vicinity of the combustion center at the initial time. In this case, the direction propagation of combustion waves in the axisymmetric case can significantly differ from thatin the plane case.

A physical and mathematical model of spark ignition and combustion of boron powder suspension in a propane-air mixture is presented. Dependences of the critical energy of spark ignition on the radius and mass concentration of particles and propane content in the boron gas suspension are obtained. Dependences between the steady flame propagation velocity in a boron powder suspension in a propane-air mixture on particle radius and particle mass concentration are obtained, and the propane content in a boron gas suspension is determined. Quantitative correspondence of the computational and theoretical values of the flame propagation velocity in a boron powder suspension in a propane-air mixture with known experimental data has been obtained.

An improved mathematical model of gasification is proposed solid porous fuel when hot gases are filtered through it. On the example of polymethyl methacrylate, the gasification regimes were studied both at constant pressure drop at the inlet and outlet of the gasifier, and at constant velocity of the gas at its inlet. In the event of a constant drop pressure gasification of combustible material takes longer and the gas temperature at the outlet increases more slowly than in the case of a constant gas velocity at input under comparable conditions.

Qualitative transformation of a low-velocity laminar flow to a turbulent state (owing to natural or artificial instability) and formation of compression waves passing ahead have been studied in much detail. A disputable issue is the nature of the emergence of a reaction site in the region between the bow compression wave and the flame front moving at a certain distance behind this wave, as well as the dynamics of interaction of this site with the main structural elements. It is the type of this site (slow or explosive combustion) that defines its subsequent interaction with the compression wave front: shockless or shock-induced expansion capable of forming a detonation wave. As a method of transforming the reaction site to an explosion site, its amplification owing to the resonance of streamwise acoustic oscillations of hot reaction products with the initial combustible mixture induced by flame propagation is discussed. It is the resonance with its multiple enhancement of the amplitude of gas-dynamic parameters that can effectively initiate the deflagration-to-detonation transition. Various stages of this transition are discussed; the corresponding estimates are made and are found to be consistent with experiments.

Interaction of homogeneous and heterogeneous detonation waves in mixtures of aluminum in oxygen and hydrogen in oxygen with a cloud of water droplets is studied by methods of mechanics of multiphase media. The main interaction mechanisms are determined: propagation of an attenuated detonation wave with a velocity smaller than the Chapman-Jouguet velocity and detonation failure. Critical conditions of detonation propagation in water sheets are determined. These critical conditions are compared with the results of modeling detonation suppression with the use of clouds of inert particles.

The protective forests in Karelia are concentrated mainly (80 %) around water objects. More than 50 % of these forests are presented by Scotch pine ( Pinus sylvestris L.) stands. Modern practice of forestry prefers the simplified felling types oriented on use of natural renewal potential of pine forests because artifical regeneration on stony soils are very complex. On a site of the strip-shelterwood felling (intensity of 35 %) in an uneven-age pine stand of bilberry type in 9 years after the felling three transects consisting of plots of 5 × 5 m with a total length of 1150 m across the clear-cut strips were established for an assessment of natural renewal. Under forest canopy pine undergrowth is presented poorly. At the general frequency of 15 % and average height of 1.2 m its density is less than 0.2 thousand tress per ha, and its condition does not give a hope to expect of growth improvement. The condition of spruce ( Picea A. Dietr.) undergrowth is better: its frequency - 36 %, height - 2.4 m, and density - 0.32 thousand tress per ha. On the cutted strips the pine frequency are 31 %, density and frequency of spruce and birch ( Betula L.) remained almost without changes; the participation of an aspen ( Populus tremula L.) and willow ( Salix L.) are increased sharply. The strip-roads are covered by willow weed ( Chamaenerion angustifolium (L.) Scop.), under the influence of which density and frequency of the conifers is twice lower. On the whole, the frequency and average height of a pine in the middle and at the edges of cutted strips are close. The executed felling did not provide the renewal of coniferous species sufficient for formation of a new forest stand, though emergence in recent years of the small undergrowth of a pine allows to count on his further quantitative increase. The executed assessment of increase in a radial growth of trees on cores showed his insignificance. The obtained results and literary data convince of obligatory need of a scarification of the soil surface during the strip-shelterwood felling execution.

The problem of assessing the balance of accumulated and degraded woody biomass in forest communities, the budget of C, CO₂, H₂O, and Q (energy) in primary virgin forests of different ages of spruce formations in the taiga zone of European Russia is discussed. The studies were carried out in specific biogeocenoses of different dynamic characteristics in the subzones of the northern, middle and southern taiga. The purpose of the research is to study in quantitative and volumetric terms the structural elements of the age series of primary virgin spruce biogeocenoses of different ages of different successional positions, the dynamics of the formation of the stem fraction of wood waste (deadwood), pools and flows of components deposited in the wood of the stem fraction of phytocenoses and tree waste in a single succession series. biogeocenoses of various dynamic characteristics. A cycle of studies was carried out on the trial plots, which made it possible to obtain information about the age structures of forest stands, their dynamic indicators, the volume of trees in the age generations of forest stands, the current tree waste and fallen trees. All volume values of forest stands and wood waste are converted into phytomass. The volumes of C, CO₂, H₂O and Q (energy) deposited in wood and released during its decomposition by wood-destroying fungi were calculated using the formula for mycogenic wood xylolysis. On the example of the spruce biogeocenosis of the middle taiga subzone of the climax phase of dynamics, the mass of carbon, different fractions of wood, presented in a graphic image, was calculated. It has been determined that the volumes of pools and flows of wood components in forest stands and during the decomposition of wood by fungi - destructors are determined by the structural features of the age series of forest stands, the volumes of wood waste in gradations of decomposition stages. A joint analysis of the age structures of forest stands, the structures of current tree waste and deadwood by stages of decomposition helps in a more accurate determination of the dynamic position of forest biogeocenosis in the expanded space of its successional development. In the most stable (climax) virgin spruce forests of the taiga, the values of the balance ratios of accumulation and decomposition of biomass represent an optimal budget model and can be regarded as reference values in comparison with forests of different origin and structural characteristics.