Effect of Shell Material on the Detonation of an Explosive Charge

The effect of shell material (copper and silicon carbide) on the detonation of a cylindrical explosive charge was analyzed. The wave patterns in the detonation products and the shells are substantially different, which is due to different sound velocities and the rapid destruction of the ceramic under explosive loading. The wave pattern at the explosive/ceramic interface was found to be affected by desensitization of the explosive due to its loading by an advancing wave from the shell side, resulting in a decrease in pressure, blurring of the detonation front, and an increase in particle velocity. Throughout the process, there is a continuous increase in the time of explosive decomposition near the interface between the explosive and the ceramic shell. An extended region with a constant pressure close to the Chapman–Jouguet pressure was observed on the axis of symmetry behind the detonation front of the explosive charge in the ceramic shell.     

Investigation of shock detonation of TATB using proton radiography

The initiation of detonation of plasticized TATB by shock loading using an initiator pressure charge of an HMX based explosive was studied by radiography. In the experiments, the size of the initiator and the initial density of the TATB charge were varied. During initiation of TATB detonation, part of the material did not react, forming so-called dark zones. As the process goes on, the detonation wave bends around the dark zones, without initiating the material within them. The evolution of the area of dark zones was compared for samples of different initial density and initiators of different sizes. The characteristic boundaries and X−t diagrams of detonation front propagation under different loading conditions were constructed from images of the explosive process. Density distributions behind a divergent detonation wave front at different times were obtained and analyzed.     

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.     

Acceleration Profile of a Flat Flyer Driven by Detonation Isentrope

In the design of explosive devices, understanding of the behavior of explosively propelled matter is one of the important steps to optimize the performance of the device. In a typical flat, metallic flyer and explosives charge system, the flyer reaches its maximum velocity after a certain degree of expansion of the detonation gas. During this expansion, the flyer is deformed in an arced‐shape by the incoming rarefaction from nearby surfaces. In this work, an acceleration/deformation profile of an explosively propelled flat, metallic plate was studied based on the isentropic expansion of detonation gas and subsequent rarefaction intrusion to the center of the flyer. In order to properly describe the arced deformation of the flyer, a rather simplified new term of the pressure release ratio behind the flyer η is introduced based on the expansion of the detonation isentrope behind the flyer. A theoretical model was built to predict the behavior of an explosively driven flyer and the rarefaction intrusion into the center of the explosives charge. The results are compared to a hydrocode simulation and exhibit favorable agreement in a limited application.     

Effect of an inert high-modulus ceramic wall on detonation propagation in solid explosive charges

The effect of an intert high-modulus ceramic wall on detonation propagation in charges of a solid heterogeneous explosive was investigated experimentally and numerically. Subdetonation pressures occurred at the boundary between the wall and the explosive for the conditions investigated. Here the detonation velocity increased, and the mass velocity and the pressure at the detonation front decreased, which is explained by the indirect effect of an overtaking wave into the unreacted explosive and the chemical reaction zone. Transverse waves, which affect the detonation parameters, propagate perpendicular to the detonation front with a velocity of ∼6 km/sec. The initial decomposition rate of the explosive directly after the compression shock determines the degree of the transverse-wave effect. Novosibirsk State Technical University. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 5, pp. 107–114, September–October, 1994.     

Detonation Velocity of Emulsion Explosives Containing Cenospheres

The detonation velocity of an emulsion explosive containing hollow alumosilicate microspheres (cenospheres) as the sensitizer is measured. The size of the microspheres is 50–250 μm. The relations between the detonation velocity and the charge density and diameter are compared for emulsion explosives containing cenospheres or glass microballoons as the sensitizer. It is shown that for a 55 mm diameter charge, the maximum detonation velocity of the composition with cenospheres of size 70–100 μm is 5.5–5.6 km/sec, as well as for 3M glass microballoons. The critical diameter for the emulsion explosive with cenosphere is 1.5–2 times larger than that for the emulsion explosive with glass microballoons and is 35–40 mm. __________ Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 5, pp. 119–127, September–October, 2005.     

Detonation combustion of gas mixtures using a hypervelocity projectile

This paper considers, from a unified point of view, problems of initiation of detonation combustion of a gaseous mixture using a hypervelocity projectile (HVP), The consideration is based on the energy criterion forHVP-induced detonation initiation. Experimental results are given that support the correctness of the criterion in a wide range of diameters (5–250 mm),HVP velocities (800–3500m/sec), and compositions of explosive mixtures (from active fuel-oxygen to hard-to-detonate fuel-air mixtures). The processes ofHVP interaction with an explosive mixture are classified. The previously unknown effect of jet formation of a detonation wave from a ballistic wave (at velocities less than the detonation velocities) was discovered for anHVP with a plane bow. Lavrentśev Institute of Hydrodynamics, Siberian Division, of the Russian Academy of Sciences, Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 5, pp. 85–102, September–October, 1997.     

Kinetics and Mechanism of Explosive Decomposition of Heavy Metal Azides

The explosive decomposition of heavy metal azides initiated by a laser pulse was studied experimentally over a broad range of action levels (from the threshold values to those exceeding the threshold ignition energy by a factor of 100) and in the time interval including the induction period, and rapid explosive decomposition, and the expansion of detonation products. The explosive glow and expansion dynamics of the decomposition products in air and vacuum were investigated, and the velocities of the explosive decomposition front, the compression pulse, and the expansion of the explosion products were measured. Based on the results obtained, the possibility of the occurrence of preexplosion phenomena is discussed and the mechanism of laser initiation of heavy metal azides is analyzed. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 1, pp. 106–119, January–February, 2006.     

Investigation of the reaction zone in heterogeneous explosives substances using an electrical conductivity method

A technique for measuring the electrical conductivity profile behind a detonation wave front with a resolution of about 0.1 mm was used to analyze the reaction zone in heterogeneous explosives. TNT-RDX mixtures, RDX with additives of water, NaCl, and a saturated aqueous solution of NaCl, and pure RDX of low density were studied. It was shown that the particle size of the explosive can have a significant effect on the structure of the reaction zone. The most narrow conducting zone (0.22 mm) was observed in fine RDX of density 1.2 g/cm³. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 2, pp. 109–115, March–April, 2008.     

Mathematical modeling of detonation of an aluminum dust in oxygen with allowance for velocity nonequilibrium of the particles

The problem of propagation of a plane detonation wave is studied on the basis of a mathematical model for the detonation of aluminum particles in oxygen with allowance for the difference in velocities and temperatures of components. A qualitative analysis of the final steady state is performed. The domains of existence of steady solutions and the manifold of solutions of various types are determined. Various types of flows are illustrated numerically. The special features of the flow structure behind the front are analyzed, depending on relaxation parameters. We have performed flow calculations taking into account the characteristic times versus the parameters behind the front and have shown agreement between the data obtained and the frozen and variable relaxation parameters. The data obtained are found to correspond to the known experimental results concerning the widths of the ignition and combustion zones. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 6, pp. 80–91, November–December, 1997.     

Detonation velocity in the transition zone of an explosive charge

Results of an experimental study of the detonation velocity in the transition zone of an acceptor explosive in a cylindrical charge consisting of two different explosives are given. An empirical relation between the length of the transition zone and the ratio of the steady detonation velocities of the donor and acceptor explosives in segmented charges is obtained. Department of the Geodynamics of Explosion of the Institute of Geophysics, Ukrainian National Academy of Sciences, Kiev 252054. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 5, pp. 118–121, September–October, 1997.     

Bubble detonation conditions

Initiation of bubble detonation in the system “inert liquid-explosive gas bubbles” by a detonation wave in a gas was studied experimentally. Compression-wave pressure profiles were determined as functions of the length of the initiation section and the initial pressure of the explosive gas mixture in it. It was shown that because of the effect of the explosive-gas volume between the diaphragm and the upper boundary of the bubble medium, the pressure in front of the initiating wave increased much more slowly than the initial pressure. The optimal length of the initiation section was found, and the critical (minimum) initiation pressure in it and at the shock-wave front were determined. It was found that for a fixed gas volume concentration in the bubble medium, the pressure in the initiation section increased insignificantly as the length of the section decreased. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 2, pp. 84–90, March–April, 2007.     

Detonation of a coal-air mixture with addition of hydrogen in plane-radial vortex chambers

Results of an experimental study of continuous and pulsed detonation of a coal-air mixture with addition of hydrogen in plane-radial vortex chambers 204 and 500 mm in diameter are presented. The tested substance is pulverized activated charcoal. A method of coal powder supply through narrow channels by means of adding the gas at the injector entrance is found. Stable regimes of continuous spin detonation with one or two transverse detonation waves moving with velocities of 1.8–1.6 km/sec are obtained for the first time in the combustor 204 mm in diameter. The frequency of pulsed detonation with radial waves is 4–4.8 kHz. The limits of continuous detonation in the combustor 500 mm in diameter are extended: regimes of continuous spin detonation with a large number (5–8) of transverse waves moving with velocities of 1.8–1.5 km/sec are obtained, the amount of hydrogen added to coal is reduced to 2.8%, and combustion of coarser fuel particles is ensured owing to an increased residence time of the mixture in the combustor. The wave structure and the flow in the vicinity of the waves are reconstructed in the combustor plane.     

JBO-9021炸药初始密度对爆轰波阵面曲率效应的影响

采用高速扫描相机及电探针,在室温环境下对不同初始密度(1.894~1.901g/cm3)、不同半径(5.0、7.5、15.0mm)的钝感炸药JBO-9021药柱开展了曲率效应实验,获取了拟定态爆轰波阵面形状及波速,分析了其随炸药柱密度及半径的变化。结果表明,随着炸药JBO-9021的初始密度由1.894g/cm3增至1.901g/cm3,3种不同半径JBO-9021药柱的爆轰波拟定态波速均增大,拟定态波阵面形状变得更为平坦,波阵面中心点与边界点之间的波到达时间差降低;在小曲率范围内(κ0.2mm-1),JBO-9021药柱爆轰波波阵面法向波速Dn与当地曲率κ的关系(Dn(κ)关系)不受药柱半径及密度的影响,当曲率κ0.2mm-1时,Dn(k)关系随药柱半径及炸药密度呈现离散趋势,药柱半径及初始密度共同影响爆轰波波阵面大曲率的Dn(κ)关系。     

Heat fluxes to combustor walls during continuous spin detonation of fuel-air mixtures

Pioneering measurements of heat fluxes to the walls of flow-type combustors of different geometries were performed in regimes of continuous spin detonation of fuel-air mixtures under unsteady heating. These heat fluxes are compared with those observed in the regime of conventional turbulent combustion in the same combustor. Air is used as an oxidizer, and acetylene or hydrogen is used as a fuel. For identical flow rates of the fuel, the heat fluxes to the combustor walls in regimes of continuous spin detonation and conventional combustion are close to each other; their mean steady values are ≈1 MW/m² (≈0.5% of the enthalpy flux of the products over the channel cross section). In both detonation and combustion regimes, the maximum heat fluxes penetrate into the walls in the mixing region (where the heat release occurs). In the case of detonation, regenerative cooling of the combustor walls by the flow of the fresh mixture occurs in the heat-release region (region of propagation of the detonation-wave front). The regeneration becomes less effective in the downstream direction because of the shorter time of contact between the walls and the cold mixture and a longer time of contact between the walls and the hot products. More intense heating persists downstream of the front, where the regeneration ceases, but the temperature of the products is high. The character of heating of the wall in the region of rotation of the front of spin detonation waves depends on the number of these waves: the zone of the maximum heat release becomes narrower with increasing number of waves. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 1, pp. 80–88, January–February, 2009.     

Detonation of pressed HMX charges

The pressure-profile measurement results obtained in the shock-wave front in bromoform upon detonation of HMX charges of diameter 40 mm and length 22–110 mm are reported. The initial density of the charges was 1.81 g/cm³. In all the experiments, a monotonic decrease in pressure occurred, and a chemical peak was not observed. With increase in the charge length, the maximum pressure values first increase and then decrease. An analysis of the pressure measurement results shows that, for the given charge size and the initiation system used, the process of HMX detonation occurs in a nonstationary regime. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 4, pp. 83–86, July–August, 2000. This work was supported by the Russian Foundation for Fundamental Research (Grant No. 97-03-32000).     

Detonation of nitrobenzene and propargyl alcohol

Detonation of mononitrobenzene and propargyl alcohol at reduced pressure is recorded for the first time in 10-mm-diameter steel tubes with a wall thickness of 13 mm with high-power initiation. The detonation velocities of nitrobenzene equal 25–50% of the ideal value obtained from thermodynamic calculations. The conditions for stationary detonation propagation are examined and the critical porosities for these materials are computed based on calculations of the fraction of material that is heated and burnt up during detonation. The computations are in good agreement with experiment. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 1, pp. 89–97, January–February 1999.     

Initiation of explosive processes in hydrogen-containing gas mixtures by a multijet flow of detonation products

Explosive regimes initiated by interaction of a detonation wave with a permeable screen are studied experimentally. Possible explosive regimes that may form behind the screen are found to be detonation, deflagration-to-detonation transition, quasisteady system consisting of the shock wave and the flame front, and decaying shock wave with the flame lagging behind it. The effect of the mixture sensitivity and screen parameters on the possibility of realization of a particular explosive regime is determined; the dynamics of the explosive regimes near the screen is considered. It is demonstrated that the interaction of the system consisting of the shock wave and the flame front with the screen can lead to initiation of detonation behind the screen.     

Flyer Plate Motion by Thin Sheet of Explosive

Acceleration of a metal plate by explosive energy at low value of charge to metal mass ratio has been studied by employing a new theoretical model based on uniform pressure and density of detonation products behind the flyer plate. Theoretical velocities of flyer plates have been compared with those measured by radiographic technique and found in good agreement. Comparing the relations for plate velocity, obtained from the present model and earlier Gurney model at low C/M values, an analytical expression for Gurney energy has been obtained in terms of detonation velocity of the explosive and adiabatic exponent of the detonation products.     

Detonation of PETN single crystals initiated by an electron beam

Luminescence in the volume of PETN (tetranitropentaerytrite) single crystals exposed to an electron beam (duration 20 nsec) with an energy density of 15 J/cm², which exceeds the threshold of explosive decomposition, was investigated in real time. Exposure to the ionizing pulse causes radioluminescence and emission related to the critical electron emission from a dielectric which is transformed to a vacuum discharge. The emission zone propagates from the surface into the vacuum at a speed of 5000–6500 m/sec. The absorption of electron beam energy in the irradiated layer (0.25 mm) causes the formation and propagation of a shock wave enhanced by the chemical reaction in the crystal. When the shock wave is reflected from the target on the rear side of the sample, its amplitude increases. This leads to detonation accompanied by emission which propagates from the backside to the irradiated surface of the sample at a speed of 7500–8500 m/sec with the subsequent expansion of the explosive decomposition products into the vacuum.