Steady Detonation in a Bubbly Medium

It is shown that the Iordanskii–Kogarko model contains a steady-state solution for a detonation wave in chemically active bubbly media under the following minimum requirements to the model: compressibility of the liquid and allowance for acoustic losses. The rule for choosing the velocity is formulated. The wave structure of the reaction zone and the velocity of steady bubble detonation are calculated. Key words: detonation, bubbly liquid, reacting gas bubbles, acoustic losses, soliton, solitary wave.     

Transmission of Bubble Detonation through a Layer of an Inert Liquid

The possibility of detonation transmission through a water plug from one column of a chemically active bubbly medium to another is experimentally verified. The critical length of the liquid plug is determined. The experiments are performed in a shock tube with bubbles of a stoichiometric acetylene–oxygen mixture in water. The character of peakpressure decay after detonationwave departure from the bubbly medium to the liquid is established. It is shown that the pressure profile retains similarity as the compression wave propagates over a discrete gas–iquid medium.     

Detonation in a Two-Layer Bubbly Medium

The formation dynamics and structural features of the two-dimensional reaction zone of a detonation wave propagating in a two-layer bubbly medium is numerically studied within the framework of the Iordanskii–Kogarko one-velocity model.     

Calculation of the Cellular Structure of Detonation of Sprays in an H2—O2 System

On the basis of the mathematical model of a two–phase two–velocity medium, detonation of a cryogenic mixture (gaseous hydrogen—drops of liquid oxygen) was studied numerically. The dynamics of formation and the special features of the structure of the two–dimensional reaction zone of the detonation wave are discussed. The cellular structure of detonation is modeled for the first time for a cryogenic hydrogen—oxygen spray.     

Detonation of Secondary Explosives in a Vacuum Suspension

The existence of self–sustaining detonation in an evacuated suspension of the particles of a secondary explosive is shown experimentally. The experiments with HMX were performed in a vertical shock tube of diameter 0.07 m and length 7 m in the range of volume–average particle concentrations 0.32—0.9 kg/m³. It is shown that the vacuum–detonation velocity does not almost depend on the volume–average concentration of particles and it is (1750±50) m/sec and that the pressure profile of a vacuum–detonation wave is smooth. The data on the electric conductivity of vacuum–detonation products and the length of the reaction zone are given.     

Dependence of the Shape of a Detonation Wave Front on the Detonation Wave Velocity upon Detonation of a Cylindrical Charge

The transition of a system of partial differential equations which describe the stationary flow behind the shock–wave front of a detonation complex upon detonation of a cylindrical charge to a system of ordinary differential equations is performed by means of the series expansion in terms of the radial variable. The necessary equations for determination of the derivatives of solutions with respect to the parameters and the initial conditions for them are formulated. Imposing the condition of continuous extendibility of the solutions leads to equations that allow one to determine the shape of a shock–wave front as a function of wave velocity.     

On the detonation velocity in a sensitive-explosive particle suspension in vacuum

In this paper we study the conditions of self-sustaining wave propagation upon combustion of a monofuel particle suspension in vacuum. We employ a two-velocity model of the flow of reaction products behind the detonation wave (DW). Essentially new conditions behind the DW front are obtained that ensure its propagation with a velocity higher than the velocity of ideal Chapman-Jouguet detonation in particle suspension in vacuum. The results agree qualitatively with the experimental data on the detonation velocity of lead azide in vacuum.Translated from Fizika Goreniya i Vzryva, Vol. 32, No. 1, pp. 71–74, January–February, 1996.     

Combustion modes and flame propagation criteria for an encumbered space

The topic is analyzed. Experiments have been performed with fuel—air mixtures in a porous medium. Measurements have been made on the velocity and pressure in the detonation and combustion waves, together with the critical initial parameters and the limits to the Peclet number. The mean detonation rate has been found to fall and the ignition has been found to be retarded in a porous medium when the wave passes through a free gap.Combustion and Flame Institute, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 4, pp. 52–60, July–August, 1994.     

Possibility of the formation of diamonds as a result of the detonation of picric acid

The dependences of the detonation velocity and electrical resistance on the initial density of picric acid were determined for developing the conclusions made earlier for TNT- and RDX-based comjpositions concerning the effect of diamond formation on the detonation velocity and resistance of detonation products. A discontinuity of the dependence of the detonation velocity on the initial density and an increase of the resistance of the detonation products in the region of this discontinuity, which are related to diamond formation in the detonation wave, were found. The relative position of the dependences of resistance on density and of the discontinuities of the dependences of the detonation velocity on the density for various explosives is discussed.Chernogolovka. Translated from Fizika Goreniya i Vzryva, Vol. 27, No. 4, pp. 117–121, July–August, 1991.     

Limits of detonation propagation in a suspension of propellant particles in vacuum in a tube

The problem of stationary detonation in vacuum with monopropellant particles propagating in a tube is formulated and analyzed numerically. It is shown that friction and heat removal onto the tube walls affect the structure of a disperse wave. The dependences of the detonation velocity on the tube diameter, the size of the propellant particles, and on their mass concentration have been determined, and the limits of detonation propagation have been found.Lavrent'ev Institute of Hydrodynamics, Russian Academy of Sciences, 630090 Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 2, pp. 76–84, March–April, 1994.     

Detonation of a highly diluted explosive

Detonation of mixtures of PETN with quartz sand with a 10–30% content of the explosive was investigated experimentally. Such systems are characterized by a low pressure and detonation velocity. The mass velocities of the solid filler and gas of the detonation products were measured by the electromagnetic method. With an explosive content of more than 15% the process is carried out by the leading shock wave and on the whole is single-velocity. The effects of a two-phase state are substantial with a low explosive content.Lavrent'ev Institute of Hydrodynamics. Siberian Branch, Russian Academy of Sciences, 630090 Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 3, pp. 124–130, May–June, 1994.     

The Use of Utilizable Explosives to Increase the Efficiency of an Explosion

The possibility of using the utilizable explosives to increase the efficiency of an explosion of industrial high–explosive (HE) charges is studied under laboratory and working conditions. To do this, the explosive charges were used as linear initiators of the elongated charges of industrial HE. It is shown that the placing of an NB–40 ballistite powder rod of diameter 10 mm in a bulk–density TNT charge of diameter 40 mm increases the velocity of acceleration of an aluminum shell by 14% (the ratio between the detonation velocities of the powder and TNT is 1.8 : 1.0). The use of ShZ–1 TNT–based and ShZ–2 RDX–based hose charges in well charges of industrial HE, such as 79/21 Grammonit (79% granular ammonium nitrate/21% scale–shaped TNT), 30/70 Grammonit (30% granular ammonium nitrate/70% granular TNT), and ammonium nitrate, as linear initiators leads to a decrease in the output of bulky rock by 15—20% and allows one to increase the grid of the wells of diameters 160 and 220 mm by 20—25% with preservation of the rock output. The ratio of the detonation velocities of ShZ–1 and ShZ–2 and industrial HE charges is within 1.5—1.7 in the case of 79/21 Grammonit and 2.2—2.6 in the case of ammonium nitrate. The results obtained are explained by the fact that the detonation of a linear initiator from utilizable materials changes the form of the detonation wave front of the basic charge; as a result, it arrives at the surface of an ambient medium at a large angle and a more intense shock wave enters the medium compared to the case without a linear initiator.     

Problem of detonation suppression by means of blankets and foams

The subject of investigation was the effect of an injection of water vapor on the detonation of fuel-air mixtures. It is shown that the injection of mass into the detonation wave reaction zone leads to a lowering of the velocity and to a disruption of detonation. The possibility of a suppression of detonation with moderate water-mechanical foams density was investigated experimentally.Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 27, No. 6, pp. 116–124, November–December, 1991.     

Plane initiation of a detonation

The conditions for exciting a plane detonation wave were experimentally observed to be independent of the initial [gas] pressure. The explanation is based on the concept that impacts of transverse waves play a leading role in initiating and propagating the detonation. The dimension of the effective zone which is responsible for initiating the detonation is close to the dimension of the chemical [energy] peak. Formulas are presented for estimating the energy equivalent of the initiator, based on the concept of transforming the plane detonation wave into a spherical, cylindrical, or plane detonation by diffracting the initial wave by convex angle. The basic analytical conclusions of the concept are confirmed by experiment.Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 3, pp. 164–170, May–June, 1993.     

Measurement and computation of shock wave attenuation in a rough pipe

Conclusion The performed investigations have shown that there exists a possibility of a purposeful variation of the gas detonation velocity by means of the appropriate geometrical roughness characteristics. It is very important that in doing so, it is possible to use data on the hydraulic resistance in channels with different obstruction types under steady flow conditions. This widens significantly the scope of the projected solutions in the development of protective facilities, designed for the suppression, or attenuation of the detonation wave. Moreover, optimal dimensions for the roughness of the chosen type exist, for which the suppression effect is maximized. For example, using a protective baffle consisting of ring inserts in the pipe, which is subject to detonation hazard, the ring placement is most effective when s/k=5–10.Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 26, No. 3, pp. 91–95, May–June, 1990.     

Interactions of Impact Shock Waves in a Thin-Walled Explosive Container. I. Impact by a Flat-Ended Projectile

Interaction of impact shock waves that could detonate an explosive (Composition B) confined in a thin-walled container impacted by a cylindrical projectile is numerically studied, based on the Forest Fire explosive reaction rate model. After the impact, rarefaction waves from projectile periphery and front cover–explosive interface catch up the forward-moving shock fronts in the explosive as well as in the projectile. At a high impact velocity, the transmitted shock front induces detonation at the front cover–explosive interface. At an intermediate velocity, the rate of energy release from the shock-compressed volume in the explosive is such that the associated effects prevail over the effects caused by rarefaction waves, leading to detonation after the shock wave travels a certain distance in the explosive. There is a range of minimum impact velocities at which the effect of rarefaction waves prevails over the energy release; hence, the detonation is excited not behind the shock-wave front moving over the explosive but only after shock-wave reflection from the high-impedance back plate. It is suggested that, in interpreting the detonation behavior of an explosive confined by a high-impedance container, one should take into account the effects of shock-wave interaction with container walls.     

Radio wave method for study of physical phenomena and chemical conversions in heterogeneous explosives under shock wave action

A method is described for determination of shock wave parameters (wave and mass velocity) in heterogeneous explosives. The example of exciting explosion in an octogene composition by weak shock waves is used to demonstrate the possibility of reliable measurement of the velocity of the initiating shock wave, the depth at which detonation develops, and the extent of the predetonation zone, as well as the character of the change in shock wave velocity upon propagation through the specimen.Chelyabinsk. Translated from Fizika Goreniya i Vzryva, Vol. 27, No. 6, pp. 107–109, November–December, 1991.     

Energy limits for the existence of detonation waves in bubbly media

The detonation waves in single- and multicomponent bubbly media were investigated experimentally. Data were obtained on the critical conditions for the initiation, the structure and properties of the detonation waves. Energy limits were established and the existence regions were determined for the detonation waves in the investigated systems.M. A. Lavrent'ev Hydrodynamics Institute, Siberian Section, Russian Academy of Science, 630090 Novosibirsk. Translated from Fizika Goreniya Vzryva, Vol. 30, No. 1, pp. 86–91, January–February, 1994.     

Detonation wave structure in a vacuum with unitary fuel particles

The structure of steady state detonation in a vacuum with unitary fuel particles is studied. It is shown that the detonation structure lacks a shock wave frozen in the gas, and that the detonation wave zone consists of a contact discontinuity with jump in gas temperature and continuous pressure, a compression relaxation wave with contact discontinuity in the ignition plane and adjacent combustion zone. Parameters of the two-phase flow in the reaction zone are calculated.Novosibirsk. Translated from Fizika goreniya i Vzryva, Vol. 27, No. 6, pp. 109–115, November–December, 1991.     

Determination of Critical Conditions for Detonation Initiation in a Finite Volume by a Converging Shock Wave

Direct initiation of spherical and cylindrical detonation in a stoichiometric hydrogen–air mixture under normal conditions by a collapsing low-pressure region (cavity) in a space bounded by a rigid shell is considered. The study of the flow with allowance for the actual mechanism of chemical reactions was performed using the finite-difference method based on the Godunov scheme, with a moving computational grid and explicit capturing of the leading shock wave and contact surface. It is established that, for a fixed pressure in the collapsing region and for its radius equal to or exceeding the known critical radius for an unbounded space, there exists a minimum (critical) shell radius, on exceeding which a detonation wave emerges in the flow field under study. In the case of spherical symmetry, the excess internal energy of the spherical layer between the shell and the low-pressure region to be spent on initiation of detonation burning attains a minimum value that far exceeds the critical energy for detonation initiation by a TNT charge in an unbounded space. Key words: discontinuity decay, hydrogen–air mixture, detonation, shock wave, critical initiation energy.