Attenuation and Suppression of Detonation Waves in Reacting Gas Mixtures by Clouds of Inert Micro- and Nanoparticles

Combustion, Explosion, and Shock Waves - Physicomathematical models are proposed to describe the processes of detonation propagation, attenuation, and suppression in hydrogen–oxygen,...     

Simulation of Convective Detonation Waves in a Porous Medium by the Lattice Gas Method

Gas—film convective detonation in a rigid porous medium is considered. The motion of the gas phase is described by a discrete stochastic lattice gas model taking into account the real laws of friction and heat exchange between the phases. The reaction kinetics was specified so that the characteristic time of combustion corresponded to experiment. The model simulates the main characteristics of the phenomenon: a nonflat (irregular) wave front, smooth increase in the pressure averaged over the charge cross section, friction–dominated mean flow, slow cooling of combustion products after completion of the reaction.     

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.     

Mathematical Simulation of Detonation Processes in a Coal-Particle Suspension

A physicomathematical model is developed, which describes propagation of detonation waves in a suspension of coal-dust particles in air or oxygen within the framework of the concepts of one-velocity, two-temperature continuum mechanics. The model is verified by available experimental data on the dependence of the detonation velocity on the particle concentration, on ignition delays behind shock waves, and on characteristic times of pyrolysis and combustion processes. Stationary detonation structures are analyzed. Formation and stable propagation of stationary detonation waves are demonstrated by means of numerical simulation of shock-wave initiation. Key words: shock waves, detonation, gas suspension, coal-dust particles, mathematical simulation.     

Mach-Reflection of Detonation Waves in condensed high explosives

In a cylindrical arrangement as deviced by G. R. Fowles and W. M. Isbell for the generation of Mach-reflection of shock waves in solids Mach-reflection of detonation waves in condensed high explosives with different detonation velocities is investigated. The process is observed directly by flash x-ray radiography. By means of this arrangement it is possible to generate via Mach-reflection a plane detonation wave, the Mach-disk. Characteristics and applications of the Mach-disk are discussed.     

Synthesis of Carbon-Encapsulated Metal Nanoparticles by a Detonation Method

Carbon-encapsulated metal nanoparticles are synthesized by a detonation method using a home-made water-soluble composite explosive. The results of the study show that detonation products contain face-centered cubic cobalt/nickel nanocrystals approximately 10–25 nm in size, which are encapsulated by thin (3–5 nm) carbon layers. These spherical and ellipsoidal nanoparticles exhibit a good superparamagnetism state at 300 K.     

Current Waves Generated by Detonation of an Explosive in a Magnetic Field

The structure of the electromagnetic field in detonation of a condensed explosive in a magnetic field is analyzed qualitatively. Propagation of a detonation wave in a magnetic field leads to generation of an electric current in explosion products. The physical reason for current generation is the freezing of the magnetic field into the conducting substance at the detonation front and subsequent extension of the substance and the field in the unloading wave. The structure of the current layer depends on the character of the boundary magnetic fields and conditions on the surface of initiation of the explosive. Detonation of the explosive in an external magnetic field B₀ generates a system of two currents identical in magnitude but opposite in direction. The structure of the arising current and its absolute value are determined by the parameter R₁ = _{0 0}D²t (₀ is the magnetic permeability of vacuum, ₀ is the electrical conductivity of detonation products, D is the detonationfront velocity, and t is the time). The value of the current increases with the detonationwave motion, and the linear current density is limited from above by 2B₀/₀. For R₁ 1, the electric field in the conducting layer is significantly nonuniform; for detonation products with a polytropic equation of state, a region of a constantdensity current is adjacent to thedetonation front. The results of this analysis are important for interpretation of experiments performed and development of new methods for studying the state of the substance in the detonation wave.     

Modeling Hydrodynamic Behaviors in Detonation

A multistage reaction model developed for general use from initiation through detonation of heterogeneous high explosives is used to specifically simulate the interface vclocimetry and plate push experiments of a triamino-trinitrobenzene-based explosive in detonation. A simplification of the unified model leads to a rate relation that ineludes only two dominant stages: a fast one that represents the major portion of reaction dictated by propagation and decomposition, and a slow one that reflects probably the formation of large carbon molecules. The apparent more energetic behavior of the equation of state near the detonation front is actually due to the slow reaction process.     

Interaction of Aluminum with Detonation Products

A method of electrical conductivity and an analysis of recovered explosion products are used to study interaction of aluminum with detonation products of condensed high explosives. The electrical conductivity of HMX/Al and RDX/Al mixtures is inhomogeneous; a region with the maximum electrical conductivity is adjacent to the detonation front, whereas the electrical conductivity decreases with distance from the front. If the wave is incident onto a wall, the electrical resistance of the composite high explosive increases, which indicates that the high-conducting zone disappears. The electrical conductivity, resistance of the conducting zone, and the time of resistance growth are found as functions of the particle size of the additive. The results obtained confirm the reaction of the metal additive with detonation products in a microsecond range of time. An analysis of condensed explosion products shows that the reaction of aluminum with detonation products proceeds on the particle surface. The amount of reacted aluminum and the oxide-layer thickness are estimated. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 1, pp. 120–129, Jnuary–February, 2006.     

铝粉-空气混合物的燃烧转爆轰过程

利用自行设计的长29.6 m、内径199 mm配有40套喷粉扬尘装置的大型水平爆轰管,研究了细片状铝粉-空气混合物在40 J弱点火条件下火焰从发生到加速、最后实现爆轰转捩的全过程,探讨了铝粉浓度和点火延迟时间对爆轰参数的影响.结果表明,铝粉-空气混合物燃烧转爆轰(DDT)过程可分为慢速反应压缩阶段和快速反应冲击阶段.当点火延迟时间为370 ms,铝粉质量浓度为300 g/m~3时,在管道中距离点火位置83倍长径比处峰值超压为9.8 MPa,爆速为1 670 m/s,发生了DDT过程.在铝粉-空气混合物自持爆轰波的传播过程中,由于呈现螺旋爆轰波结构,爆速和峰值超压随着传播距离振荡.     

Initiation of a Porous Explosive by Overdriven Gas Detonation Products

This paper reports results of experiments on initiation and development of detonation in cylindrical charges of a porous explosive by overdriven detonation products of a gas mixture C₂H₂ + 2.5 O₂. Explosive charges with a bulk density of about 1 g/cm³ in fragile shells were studied. For PETN and RDX charges, the critical initial pressure of the gas mixture at which detonation initiation still occurs is determined and the pressures acting immediately on the charge are given. For PETN, critical initial pressures and initiation delays were measured for the first time for charges with particles of various diameters. The obtained dependence characterizes the following abnormal property of porous charges: there is an optimum particle size for which the explosive sensitivity is maximal. Streak records of selfluminosity for typical initiation modes are given. Mass velocity profiles in initiation waves at different depth of the charge are obtained using an electromagnetic procedure.     

爆炸法合成碳包裹铁和钴纳米颗粒

以苦味酸/二茂铁和苦味酸/乙酸钴为爆炸物,通过热引发方式使其在不锈钢耐高压容器中发生爆炸反应来制备碳包裹铁和碳包裹钴纳米颗粒.采用TEM,HRTEM和XRD等分析方法对包裹型颗粒的形貌、尺寸、微观结构及中心颗粒的物相结构进行表征.苦味酸/二茂铁的爆炸所得碳包裹铁纳米颗粒的粒径分布非常窄(5～20nm),被包裹的中心铁颗粒多为圆球形单质铁,呈体心立方结构.苦味酸/乙酸钴爆炸产生的碳包裹钴纳米颗粒的粒径在10～60 nm范围内,被包裹的中心钴颗粒星圆球形或圆锥形,为具有面心立方结构的单质钴.     

Use of Gas Detonation in a Controlled Frequency Mode (Review)

Research problems arising in the development of various devices with the use of detonation in a controlled frequency mode (pulsed detonation) are considered. The frequency of cycles can be varied by independent initiation of detonation by a controlled system of ignition. Problems of detonation initiation concerning the frequency mode are considered: direct initiation, deflagration-to-detonation transition, and transition of a detonation wave formed in a narrow channel into a wide channel. The possibility of using thermochemical conversion in devices with pulsed detonation is considered. Examples of practical applications of devices with pulsed detonation are given (pulsed detonation engine, using pulsed detonation for drilling and crushing of rocks, and removal of metal cord from rubber in worn tires).     

Studies of Detonation Characteristics of Aluminum Enriched RDX Compositions

Research on the effect of aluminum contents and of its particle size on detonation characteristics of RDX‐based compositions containing 15–60% aluminum was carried out. Measurements of detonation velocity for different charge diameters and confinements were performed. To measure the shock curvature of the detonation wave, X‐ray photography was applied. Unconfined charges and charges confined with a water envelope were tested. The radius of the detonation front curvature was determined. The cylinder test results were the basis for determination of the acceleration ability and energetic characteristics of the detonation products of the mixtures. The Gurney energy describing the acceleration ability was found. The detonation energy of the mixtures tested was also estimated from the cylinder test data.     

Synthesis of a New Modification of Aluminum Oxide, Gahnite, and Zincite in Detonation

Results of studying the products of explosion of aluminum and octogen charges enclosed by a brass shell under conditions of complete burning out in air are described. Gahnite ZnAl₂O₄, a new (metastable) modification of aluminum oxide, and small quantities of zinc oxide were identified in the condensed explosion products. The x-ray pattern of the aluminum oxide was indexed in a face-centered cubic lattice with the parameters a = 7.854(1) Å, V = 484.4(2) ų. The possible Fedorov groups are Fm3m, F432, and F43m.     

Numerical Simulation of Detonation Initiation with a Shock Wave Entering a Cloud of Aluminum Particles

Based on the mathematical model of a reacting two-phase medium in the two-velocity, two-temperature approximation, the process of planar shock wave entering a cloud of aluminum particles is numerically studied. The incident shock wave may have either a rectangular or a triangular profile, i.e., it may be accompanied by a rarefaction wave. An analysis of numerical data allowed us to determine conditions of possible establishment of a steady detonation regime in the cloud. Scenarios of initiation and types of detonation flows in the cloud are determined as functions of the amplitude of the incident shock wave and initiation energy. Criteria of detonation initiation for various fractions of particles are obtained, which express the dependence of the energy stored in the shock wave on its Mach number.     

Effects of Aluminum Content on TNT Detonation and Aluminum Combustion using Electrical Conductivity Measurements

To improve the understanding how aluminum contributes in non‐ideal explosive mixtures, cast‐cured formulations were analyzed in a series of electrical conductivity experiments. Five types of TNT‐based aluminized explosives, with aluminum mass fractions from 0 % to 20 % were considered in this study. The electrical conductivity of the detonation products in aluminized explosives was measured using an improved conductivity measurement method. The conductivity measurement results show that the detonation process of TNT‐based aluminized explosives can be divided into two stages: the first stage is the detonation reaction of TNT, and the second stage is the combustion reaction of aluminum with the detonation products. In the first stage, the duration of the TNT detonation increases with increased aluminum content; examination of the peak conductivities of the explosives with various aluminum contents indicated that a higher aluminum content is associated with a lower peak conductivity. Additionally, the ignition time of Al in the second stage is also determined. This work not only presents a means for studying the detonation process of aluminized explosives at 0–2.21 μs, but it also verified the relationship between the aluminum content and electrical conductivity in detonation products.     

TATB基和CL-20基PBX炸药爆轰波拐角性能的实验研究

为研究TATB基和CL-20基PBX爆轰波的拐角性能,采用蘑菇(Mushroom)试验计算了含95%TATB基(PBX-Ⅰ)、CL-20基(PBX-Ⅱ)及添加了铝粉的CL-20基(PBX-Ⅲ)炸药药柱在起爆直径10mm和6mm条件下的出射角、熄爆角及延迟时间,讨论了3种PBX炸药的爆轰传播特征和拐角性能。结果表明,起爆直径为10mm时,PBX-Ⅰ的出射角和熄爆角(22.7°和31.9°)明显小于PBX-Ⅱ的出射角和熄爆角(均为90°);起爆直径为10mm和6mm时,PBX-Ⅱ和PBX-Ⅲ的出射角和熄爆角均为90°,都能够传播为类似球形。对于CL-20基PBX,随着铝粉的加入和起爆直径的减小,其炸药半球均能够达到可靠传爆状态,具有较好的拐角性能。TATB基PBX炸药药柱的出射角和熄爆角均显著减小,表明TATB基PBX炸药药柱的拐角性能较差。3种PBX炸药的拐角性能优劣顺序为:PBX-ⅡPBX-ⅢPBX-Ⅰ。     

Corner Turning of Detonation Waves in an HMX‐based Paste Explosive

Detonation wave profiles have been determined for RX‐08‐HD (74% HMX paste) loaded in 3 mm square troughs after turning both acute 90° bends and bends with a 1.5 mm inner radius turn and a 4.5 mm outer radius. The explosive troughs were confined with either lucite or copper. We show that the shape of the detonation wavefront can be explained in terms of a Huygens' construction from the leading point to the outer radius. Turbulent behavior occurs between the leading point and the inner edge. The turbulence appears enhanced for the curved samples with copper confinement. The distance the detonation wave has to travel past the turn in order to regain its original symmetry was found to be governed by an exponential time constant of 0.6 µs. Analysis suggests that the leading point alone stays at the straight‐ahead detonation velocity throughout the turn.