Modeling of low-speed combustion of a methane-air-coal dust suspension

A plane one-dimensional problem of the propagation of slow-speed combustion in methane-air-coal dust suspensions is solved. Methane contained originally in the gas is assumed to burn-up completely in the flame front. The front velocity relative to the gas is calculated from relations derived in analysis of the stationary problem using the theory of thermal explosion. The gas suspension is regarded as a two-temperature and two-velocity medium. Heterogeneous reactions of carbon (coke) combustion and carbon monoxide reduction, and the yield of volatile components and their gas-phase combustion together with carbon monoxide are taken into account. Based on numerical calculations, the coal dust is shown to affect unambiguously the flame velocity, with moderate content of the dust. In lean mixtures, with a moderate content of the dust the intensity of the combustion wave increases and decreases under conditions close to stoichiometric ones. Institute of Mechanics at Moscow State University, 119899 Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 4, pp. 46–54, July–August, 1997.     

Mathematical modeling of accidental gas explosions

Results are presented from mathematical modeling of the detonation of gas clouds in the form of cylinders with different ratios of height to radius. It is shown that the parameters of the resulting air shock wave depend significantly on the shape of the cloud. The trotyl equivalents of the explosion are obtained on the basis of maximum excess pressure and the impulse of excess pressure in the wave. This information can be used to analyze the consequences of accidents and substantiate standards on explosion-proofing. N. é. Bauman Moscow State Technical University, 107005 Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 6, pp. 155–165, November–December, 1995.     

Influence of high-intensity laser radiation on a shock wave

It is shown that a shock front vanishes rapidly when irradiated by a strong ionizing laser beam. The most interesting physical cases associated with different relations between characteristic frequencies of the problem are discussed. Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 5, pp. 81–85, September–October, 1993.     

Ignition of forests as a result of the explosion of the Tungusskii meteorite

Relying on the laws of the mechanics of multiphase reacting media, we construct a mathematical model of the ignition of forests by radiation emitted as a result of the explosion of the Tungusskii meteorite. The forest canopy is modelled by a multiphase porous reacting medium. The ignition regimes realized at different distances from the center of the explosion are analyzed. It has been established that the maximum radius of the ignition zone is 6–9 km for the forest canopy and 12–16 km for the ground cover, depending on the stock and moisture content of combustible forest materials. This corresponds to an explosion energy of 25·10¹⁶ J. V. V. Kuibyshev Tomsk State University, Tomsk. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 6, pp. 8–14, November–December, 1993.     

Optical methods of studying the explosion of shaped charges

This article describes a group of optical methods for studying the explosion of shaped charges, including modifications of established methods (slit photorecording, the luminous points method, laser probing) and two new methods — measurement of wave velocities with transducers based on optical fibers and laser visualization of the shaped-charge jet. Optical methods are used to study such jets under laboratory conditions. Characteristic distortions of the symmetry of the detonation front and their effect on the jet are discussed, the probable character of breakup of the jet is established, and the distribution of the jet particles with respect to size is determined along with the maximum values of average limiting tension for copper. Scientific-Research Institute of Machine Design, 125212 Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 6, pp. 147–154, November–December, 1995.     

Explosions in the lower and middle atmosphere: The spherically symmetrical stage

The laws of evolution of spherically symmetrical explosions with a high initial energy concentration in the atmosphere at heights from 0 to 90 km are investigated. The processes of initial energy release are ignored, and the explosion is assumed to be massless, i.e., the initial data are specified in the form of a uniformly heated sphere with a constant air density. The results are obtained by radiative gasdynamic numerical calculations in the range of explosive energies from 4.2·10¹² J to 4.2·10¹⁶. J. Institute of Geosphere Dynamics. Russian Academy of Sciences, Moscow 117979. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 5, pp. 129–142, September–October, 1994.     

Motion of a shaped-charge jet in a porous medium

The problem of the motion of a shaped-charge jet in a porous medium is equivalent to the problem of a blunt cylinder in a hypersonic flow whose velocity at infinity is equal to the jet velocity in the porous medium. The flow pattern of the medium is the same as in the case of propagation of a blast wave generated by a point explosion of a cylindrical charge. The approximate theory of a strong explosion is used to obtain the basic relations for the shock wave and the expanding cavity in the hypersonic flow of a porous medium around the blunt cylinder. A comparison with experiments on the motion of a copper shaped-charge jet in porous aluminum is performed. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 6, pp. 119–124, November–December 1999.     

Reactions of three-layer chambers as the result of detonation in them of extended explosive charges

Conclusions An experimental and numerical investigation was conducted, of the reaction of three-layer explosion chambers to internal explosive loading. It is shown that the use of concrete as an intermediate layer can significantly increase the supporting capacity of the chambers, because of the increase of the inert mass of the structure. Peculiarities of deformation of the concrete layer were recorded, consisting in the formation of blocks with constant thickness, equal to the initial thickness, moving relative to one another. A method is proposed for estimating the supporting capacity of chambers similar to those tested. Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 18, No. 4, pp. 88–93, July–August, 1982.     

Investigation of the flow inversion properties behind a block of small axisymmetric nozzles of a homogeneous gas-dynamic laser

Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 27, No. 5, pp. 94–101, September–October, 1991.     

Conditions of the Thermal Explosion under Forced Convection of a Reacting Mixture

Conditions of origination of the thermal explosion in a cylindrical chemical reactor equipped by a certain number of symmetrically located stirrers ensuring forced convection of the reacting mixture are considered in the approximation of an infinite Peclet number and under the assumption of laminar motion of the fluid. The critical value of the thermal explosion parameter (Frank-Kamenetskii parameter) is found as a function of the number of stirrers and the distance between the centerlines of the stirrers and reactor. As the number of stirrers increases, the calculations predict a lower probability of the thermal explosion, and the critical value of the parameter can severalfold exceed its classical value. It is found that the thermal explosion parameter substantially depends on the location of the stirrers, responsible for heat removal from the reactor. __________ Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 5, pp. 49–54, September–October, 2005.     

Effective diameter and compactness of glass fibres as a function of the twisting characteristics

The effective diameter of glass fibres is determined with twisting data and their compactness is determined in the form of a compactness coefficient. The experimental curves of the effective diameters and corresponding compactness coefficients are reported for glass fibres of varying structures. Moscow State Textile Academy. Translated fromKhimicheskie Volokna, No. 3, pp. 54–55, May–June, 1999.     

In the theory of blast waves

The behavior of the blast wave from an exploding spherical volume is investigated mathematically over the entire range of blast-wave propagation. The computational method uses analytical results for a similar problem for a point explosion with counter pressure and the theory of an asymptotically equivalent point explosion. The asymptotic solution of the gas-dynamic equations away from the explosion site is matched to the initial conditions of blast-wave formation due to the disintegration of the detonation shock upon its arrival at the boundary of the exploding volume. The spatial distribution of the blast-front pressure is found for combustible gaseous systems and solid explosives. The theoretical results obtained agree quantitatively with available experimental measurements. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 4, pp. 93–99, July–August, 2006.     

Determination of recombination and attachment rate constants from ballistic experiments

We present measurements of the electron concentration in wakes behind aluminum spherical models flying in air with velocity 3.4–5.7 km/sec at a pressure of 10–80 torr. We have calculated the heating and entrainment of aluminum from the surface of the models as they move within the flight range. We show that condensation of Al vapor may occur at distances of more than 100 diameters of the body and pressure ≳80 torr. We pose and solve the inverse problem of determining (from experimental data) the effective attachment coefficient for attachment to air molecules and the attachment rate constants for AlO+e→AlO⁻, AlO₂+e→AlO₂ ⁻. Scientific-Research Institute of Mechanics, Moscow State University, Moscow 119899. Translated from Fizika Goreniya i Vzryva, Vol. 31, No. 5, pp. 70–82, September–October, 1995.     

Composition of the condensed detonation products of mixed explosives

It is shown experimentally that in the explosion of mixed explosives that have nitrogen-containing components and a combustible (aluminum, boron, and titanium), conditions under which the condensed explosion products contain mainly nitrides in the form of powders of dispersity 0.1–1.0 μm that are stable when stored in air can occur. The possibility of formation of lower volatile suboxides is shown. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 4, pp. 92–94, July–August 1999.     

Two-dimensional numerical simulation of deflagration-to-detonation transition for a porous explosive using a model of a multivelocity heterogeneous medium

The model of a multivelocity heterogeneous medium is used for one- and two-dimensional numerical calculations of the deflagration-to-detonation transition for charges of a porous explosive enclosed in a casing. Calculation results are compared with experimental data. Depending on the charge diameter, different explosion regimes — detonation and low-velocity explosive transformation — are registered in both the two-dimensional calculations and experiments. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 3, pp. 97–106, May–June, 2000.     

Heterogeneous diffusive combustion of condensed propellant in weightlessness

A self-similar solution has been obtained for the nonstationary plane one-dimensional problem of diffusive combustion of the propellant surface in the heterogeneous regime in the case where the propellant is the condensed phase and the oxidizer and combustion products are the gaseous phase. The laws of conservation of mass and energy flows through the interface surface, on which the burning results in energy release, allow us to close the system of differential equations for the gaseous and condensed and to obtain the exact solution of the problem in a homobaric approximation. The solution obtained determines the time dependence of the rate of surface burn-out, the temperature profiles in the gaseous and condensed phases, and the profiles of concentration of the gaseous reactant, and allows us to study the main characteristics of the process versus the values of the external determining parameters. Moscow State University, Moscow 119899. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 5, pp. 33–40, September–October, 1994.     

Autoregression method for determining the decrement and frequency of the natural oscillations of a gas in a combustion chamber

Conclusions A new method for determining the decrement and frequency of the natural oscillations of the gas from the intrachamber noise for stable combustion regimes has been developed. The accuracy of estimates of the decrement and frequency of oscillations obtained by the given method has been analyzed, and rules for processing of realizations of random oscillations of the gas have been determined which provide the required accuracy of the estimates of the decrement in the range 0.01–0.4. The proposed approach for the construction of an algorithm for the processing of experimental data reduces the problem to a linear one and allows the application of mini- and micro-computers to its solution. The method possesses low sensitivity to the presence of additive noise in the recorded signal and provides the required accuracy for the determination of small values of the decrement. For the choice of a filter which ensures a signal/noise ratio of 16 or greater, application of the method is not required if simulators are employed in the calibration of the analytic procedure. The proposed method can be implemented in all branches of technology where the mechanism of generation of processes to be analyzed can be represented as the response of a linear, oscillatory system to a wide-band random input. Moscow. Translated from Fizika Gorenia i Vzryva, Vol. 23, No. 6, pp. 33–40, November–December, 1987.     

Experimental investigation of the change of the shockwave sensitivity of explosives due to weak precursor waves

Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 28, No. 6, pp. 70–73, November–December, 1992.     

Experimental ignition time determination for a particle formed during metal disintegration in oxygen

Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 27, No. 5, pp. 10–16, September–October, 1991.     

Motion of a plate thrown by a glancing detonation wave

A method is described for computing the motion of a thrown plate in terms of its specified maximum turning angle and a known polytropic index for the explosion products for use in the explosion working of materials. This method makes it possible to determine the throwing profile, with fair accuracy, over a relatively wide range of the ratio of the masses of the explosive and plate. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 1, pp. 122–126, January–February 1999.