基于三维离散元方法研究热点的位置和温度对奥克托今颗粒点火燃烧的影响

炸药的点火燃烧特性与炸药的安全和使用密切相关,其一直是研究者重点关注的问题之一.普遍认为,凝聚炸药起爆的关键是热点.基于此,本文采用三维离散元方法,以奥克托今(HMX)颗粒为研究对象,探究了HMX颗粒中不同位置和初始温度的热点对其燃烧过程的影响.结果发现,热点的不同初始温度和位置都会对HMX炸药颗粒的燃烧特性造成影响.由于处于炸药内部分散位置的热点表面积较大,其相比集中的热点更有利于HMX炸药颗粒的起爆.并且研究发现,并不是热点的温度越高越有利于炸药的起爆,这也取决于炸药颗粒的含量.本文的研究工作对炸药的实验研究以及军事应用提供了一定的参考.     

凝聚炸药爆轰波在高声速材料界面上的折射现象分析

凝聚炸药爆轰在边界高声速材料约束下传播时,爆轰波会在约束材料界面上产生复杂的折射现象.本文针对凝聚炸药爆轰波在高声速材料界面上的折射现象展开理论和数值模拟分析.首先通过建立在爆轰ZND模型上的改进爆轰波极曲线理论给出爆轰波折射类型,然后发展一种求解爆轰反应流动方程的基于特征理论的二阶单元中心型Lagrange计算方法来数值模拟典型的爆轰波折射过程.从改进爆轰波极曲线理论和二阶Lagrange方法数值模拟给出的结果看出,凝聚炸药爆轰波在高声速材料界面上的折射类型有四种:反射冲击波的正规折射、带束缚前驱波的非正规折射、带双Mach反射的非正规折射、带λ波结构的非正规折射.     

Aluminum oxidation in shock and detonation waves

Experimental data on the detonation velocity of aluminized explosives and the temperature of the material behind the shock wave front in condensed media, including aluminum-oxidizer mixtures were examined. It was demonstrated that the oxidation of aluminum to the highest oxide behind the front of shock and detonation waves is limited by the dissociation of aluminum oxides at temperatures above 3.5 kK.     

On the mechanism of the detonation of organic high explosives

This article presents a further analysis of isotopic labeling data on the mechanism of the detonation of TNT-, RDX-, and HMX-containing mixtures and on the release of free carbon from these mixtures. The distribution of carbon isotopes among the condensed explosion products and, for the first time, among the gaseous ones is considered in relation to the particle size of the mixed explosives. A sequence of main chemical reactions in the detonation wave is suggested to account for the experimental data discussed.     

气相/凝聚炸药爆轰合成的碳包铜纳米颗粒特征

采用凝聚炸药爆轰和气相爆轰分别制备碳包铜纳米颗粒,并利用XRD,Raman和TEM等方法对合成纳米产物进行对比分析。其中凝聚炸药爆轰法以柠檬酸铜干凝胶、油酸和黑索金为原料按照一定比例配成爆炸源,在氮气的保护氛围中引爆；而气相爆轰法以乙酰丙酮铜为原料,分别以H2和O2,H2和空气为爆炸源,在负氧条件下引爆。通过XRD,Raman和TEM分析结果表明,两类爆轰法均可得到分散性良好的碳包覆铜纳米颗粒,碳壳石墨化程度较高。气相爆轰可以合成10 nm以下的纳米晶粒,而凝聚炸药爆轰合成的晶粒尺寸在20~40 nm,且存在较多空壳结构；气相爆轰产物其碳壳尺寸在2~3 nm,凝聚炸药爆轰产物其碳壳尺寸在2~5 nm。     

非均匀炸药冲击起爆和起爆后的行为

 介绍并分析了Campbell 等人及其他作者研究非均匀炸药冲击起爆和起爆后行为所获得的实验结果,但不涉及其冲击起爆条件。足够强的冲击波进入非均匀炸药后,爆轰将瞬时（指不经过感应时间）且直接（指不经过其他过程,如爆燃）被引发;非均匀炸药起爆后,其中传播的自始至终是一个不断增长的爆轰波,直至发展为正常爆轰,整个过程都是爆轰的增长（新定义）过程。不存在由反应冲击波不断增长并转变为爆轰波的所谓向爆轰的增长。所谓向爆轰的增长,实际上是爆轰的增长（按新定义）的初期;Craig原定义的爆轰的增长,实际上是爆轰的增长（按新定义）的后期;而所谓反应冲击波,实际上是增长中的初期爆轰波。爆轰的增长（按新定义）是所有猛炸药的特性,炸药反应不充分并逐渐趋于充分是爆轰的增长的化学机制。     

Nonequilibrium Zeldovich-von Neumann-Doring theory and reactive flow modeling of detonation

This paper discusses the Nonequilibrium Zeldovich-von Neumann-Doring (NEZND) theory of self-sustaining detonation waves and the Ignition and Growth reactive flow model of shock initiation and detonation wave propagation in solid explosives. The NEZND theory identified the nonequilibrium excitation processes that precede and follow the exothermic decomposition of a large high explosive molecule into several small reaction product molecules. The thermal energy deposited by the leading shock wave must be distributed to the vibrational modes of the explosive molecule before chemical reactions can occur. The induction time for the onset of the initial endothermic reactions can be calculated using high pressure-high temperature transition state theory. Since the chemical energy is released well behind the leading shock front of a detonation wave, a physical mechanism is required for this chemical energy to reinforce the leading shock front and maintain its overall constant velocity. This mechanism is the amplification of pressure wavelets in the reaction zone by the process of de-excitation of the initially highly vibrationally excited reaction product molecules. This process leads to the development of the three-dimensional structure of detonation waves observed for all explosives. For practical predictions of shock initiation and detonation in hydrodynamic codes, phenomenological reactive flow models have been developed. The Ignition and Growth reactive flow model of shock initiation and detonation in solid explosives has been very successful in describing the overall flow measured by embedded gauges and laser interferometry. This reactive flow model uses pressure and compression dependent reaction rates, because time-resolved experimental temperature data is not yet available. Since all chemical reaction rates are ultimately controlled by temperature, the next generation of reactive flow models will use temperature dependent reaction rates. Progress on a statistical hot spot ignition and growth reactive flow model with multistep Arrhenius chemical reaction pathways is discussed. The text was submitted by the authors in English.     

A Comparative Study for the Equation of State of Dense Fluid Hydrogen

Recent developments in shock-wave experimental techniques have allowed the 100 GPa range to be probed. Driven by a two-stage gas gun (Livermore, USA) or chemical explosives (Chernogolovka, Russia), the multiple shock-wave technique has been applied to determine the equation of state and the electrical conductivity of dense hydrogen and deuterium fluids. In single shock wave experiments driven by the NOVA laser, the principle Hugoniot curve of deuterium was determined. Interesting effects such as dissociation and the transition to metallic-like conductivities occur under these conditions. The equations of state applied so far to analyze the experimental data are compared and a new semi-empirical equation of state is given.     

含铝炸药水下爆炸性能的实验研究

对RS211、HL-1、HL-2这3种含铝炸药和TNT炸药进行了水下爆炸实验,测量了4种炸药水下爆炸冲击波压力剖面和气泡脉动周期,获得了4种炸药水下爆炸冲击波的峰值超压、冲量、能量和气泡能。实验结果表明,在所研究的范围内,与TNT炸药相比,含铝炸药的冲击波能量有明显增加,约为TNT炸药的1.20～1.35倍,气泡能有显著增加,约为TNT炸药的1.50～2.30倍,表明在炸药中加入铝粉对于提高炸药水中爆炸威力是有益的。     

Theoretical study of breaking and slipping processes for HMX/graphite interface

Interface dynamics is an important issue to understand the hot spot formation mechanism in high energy explosives. We have studied the interface between octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and graphite. The former is a good performance explosive but has high sensitivity. The latter is the desensitizer for the former. Two kinds of dynamic processes have been investigated: breaking and slipping. The structure evolution, energy variation, and breaking/slipping stresses were calculated. We found that different interface processes lead to different energy dissipation ways. For breaking, it is by surface relaxation. For slipping, it is by interface friction. Both the two ways contribute to the hot spot formation and shock sensitivity of explosives.     

High electrical conductivity of trotyl detonation products

A new measurement scheme makes it possible to study the conductivity of detonation products of condensed explosives with a time resolution of about 10 ns. Experiments with cast trotyl show that conduction under detonation is a complex phenomenon associated with the chemical reaction zone and the expansion of the reaction products. The time variation of the electrical conductivity has a sharp peak (≈250 Ω⁻¹ cm⁻¹) and a plateau (≈35 Ω⁻¹ cm⁻¹). The peak corresponds to the highest conductivity value that has been ever observed for the products of chemical explosive detonation. The results support the validity of the contact method for measuring the detonation conductivity of trotyl.     

Macrokinetics of the retention of condensed carbon and detonation diamond in a hermetic explosion chamber

The effect of the thermophysical parameters of a cooling medium on the macrokinetics of secondary physicochemical processes that occur in a hermetic chamber after the explosion of a solid explosive charge is studied. The yields of condensed carbon and the content of the diamond phase in it are mainly determined by the temperature of the medium in the chamber after explosion. The maximum yield of detonation diamond synthesized from a trinitrotoluene-hexogen TG50/50 alloy is equal to ～10% of the initial explosive mass and is achieved when the steady-state temperature of the medium in the chamber does not exceed T_m=550±50 K. As this temperature increases, the yield of detonation diamond decreases approximately in inverse proportion to the temperature, and, at T_m>2800 K, there is virtually no diamond phase in the explosion products. The conversion of condensed carbon due to the presence of the oxygen-containing components of the explosion products (CO₂, H₂O) begins at a temperature of the medium of above 1550±150 K. The decrease in the final energy release that is experimentally detected in calorimetric studies in the case of an explosion of solid explosives with a negative oxygen balance in an inert gaseous medium or in the case where explosives are surrounded by massive shells results from the endothermic conversion of condensed carbon, which absorbs a significant portion of the explosion energy.     

CTVD格式数值计算非均质炸药爆轰问题

将高分辨率激波捕捉格式CTVD格式拓展应用到非均质炸药爆轰的数值模拟问题.增加了化学反应率控制方程,引入Lee-Tarver点火成长模型,未反应的固体炸药和化学反应气体产物都使用JWL形式状态方程.数值模拟了非均质固体炸药PBX-9404和TATB的冲击起爆问题.获得了较高的爆轰波分辨率和光滑解区的数值精度,对具有复杂物态方程形式的固体炸药爆轰问题,CTVD格式具有简单实用、高效和高分辨的特点.     

High-order numerical simulation and modelling of the interaction of energetic and inert materials

We present an integrated algorithm on a Eulerian grid, for multimaterial simulations of energetic and inert materials modelled by non-ideal equations of state. We employ high-resolution shock capturing numerical algorithms for each material inside its domain and use an overlap domain method across the interface, maintained by a recently developed, hybrid, level-set algorithm. For applications to condensed explosives we implement a non-ideal, wide-ranging equation of state and reaction rate law. For inert materials, like plastic, metal, water, etc., we implement a (linear in the pressure) Mie–Grüneisen, (U _p ?U _s ), equation of state. We present a series of verifications of the integrated multimaterial code and show validations against experiment. We show examples of simulations of various experiments associated with real or planned experiments, some of which contain energetic materials (specifically the condensed explosives PBX-9502 and PBX-9501).     

Effect of the Al/O ratio on the Al reaction of aluminized RDX-based explosives

Aluminum(Al) powders are used in composite explosives as a typical reducing agent for improving explosion performance. To understand energy release of aluminum in aluminized RDX-based explosives, a series of thermal measurements and underwater explosion(UNDEX) experiments were conducted. Lithium fluoride(LiF) was added in RDX-based explosives, as a replacement of aluminum, and used in constant temperature calorimeter experiments and UNDEXs. The influence of aluminum powder on explosion heat(Qv) was measured. A rich supply of data about aluminum energy release rate was gained. There are other oxides(CO_2, CO, and H_2O) in detonation products besides alumina when the content of RDX is maintained at the same levels. Aluminum cannot fully combine with oxygen in the detonation products. To study the relationship between the explosive formulation and energy release, pressure and impulse signals in underwater experiments were recorded and analyzed after charges were initiated underwater. The shock wave energy(Esk), bubble energy(Eb), and total energy(Et) monotony increase with the Al/O ratio, while the growth rates of the shock wave energy,bubble energy, and total energy become slow.     

复杂腔体本征电磁场空间分布的统计方法

 利用半经典近似方法分析了电大复杂腔体内电磁波传播的混沌特征,从而引入了3维矢量本征函数的随机平面波假设。根据电磁波传播的随机极化特征,利用统计方法推导出基于该假设本征电磁场空间分布的统计模型。应用数值方法对3维Sinai微波腔体进行模拟计算,其计算结果与统计模型符合较好。这些统计模型与腔体的具体细节特征无关。     

Potential interference mechanism for the detection of explosives via laser-based standoff techniques

A variety of laser-based standoff techniques are currently being developed for the detection of explosives. Many approaches focus on the detection of NO as an indicator for the presence of nitro-based explosives. One of these approaches uses lasers to vaporize the explosive molecules residing at or near a surface, photo-dissociate the molecules resulting in vibrationally hot NO, and then perform laser-induced fluorescence on the vibrationally hot NO. Most related reports have focused on using 236 nm or 247–248 nm for the laser excitation of vibrationally hot NO. In addition, a recent report suggests the use of 532 nm to desorb, vaporize, and photo-fragment explosive samples. We report here on energy transfer from laser-excited N₂ to NO and its consequences for the detection of nitro-based explosives. A potential interference mechanism was found for using 532 nm and 236 nm. The interference mechanism is based upon multi-photon excitation (532 nm) or two-photon excitation (236 nm) into excited states of molecular nitrogen and subsequent energy transfer from nitrogen to NO, followed by NO luminescence. Such interference mechanisms highlight the complexity of the explosive detection problem and the need for complementary approaches to improve the detection capabilities.     

Influence of the particle size of the components on the mechanical sensitivity of metallized high explosives

The results of experimental studies of the mechanical initiation of compositions of explosives (HMX, RDX) with aluminum powder at various component and granulometric compositions are presented. It is shown that nanocomposites and mechanical mixtures of explosives with nanoscale aluminum are characterized by extremely high sensitivity in comparison with compositions containing micron-sized aluminum powder. The results are explained based on the assumption that an increase in the sensitivity is caused by an additional heat release in the course of chemical interaction of components at mechanically induced hot spots. Data on the effect of passivating coating and aging of the particles of nanoscale aluminum on the sensitivity of binary compositions are obtained and analyzed.     

Explanation of critical angular velocities of the vortex formation in a stirred Bose-Einstein condensate

The problem of explaining the critical angular velocity Ω_c when the formation of a vortex in the stirred Bose-Einstein condensate becomes energetically possible is considered in the framework of the variational approach. The origin of smallness of the calculated Ω_c in comparison with the measured values, which takes place for a pure quantum state with the unit angular momentum per condensed particle, is uncovered. The agreement with the measured Ω_c is achieved upon admitting a small admixture of the zero angular-momentum state in the wave function of the one-vortex quantum state prepared after stirring. A portion of this admixture amounts to 1–13% of the total condensed atoms. A possible test of this hypothesis is proposed.     

CO2-CO分子间等效作用势与液态CO冲击压缩特性研究

二氧化碳(CO2)和一氧化碳(CO)是高含碳凝聚态炸药爆轰混合产物中两种重要成分,因此,在研究爆轰反应平衡问题以及爆轰产物状态方程时,必然要涉及到CO2-CO分子间等效作用势的确定问题.本文从反应体系化学平衡的角度,采用分子流体的微扰变分理论(MCR)以及分子混合物的范德瓦耳斯单相流体模型(vdW-1f),对过去和最近发表的液态CO的冲击压缩实验数据进行了详细分析,重新优化了CO2-CO分子间exp-6型势函数中的参数值.讨论了本文确定的CO2-CO分子间等效作用势与过去所采用的势函数之间存在的差别.