Comparative analysis of physical mechanisms of detonation initiation in HMX and in a low-sensitive explosive (TATB)

Based on the concept of hot spots, the basic physical factors determining the macrokinetics of chemical reactions in heterogeneous crystalline explosives are estimated. The macrokinetics in plasticized TATB is shown to be basically determined by the velocity of combustion propagation from microscopic reaction spots (hot spots), whereas the macrokinetics in plasticized HMX is determined by the density of hot spots. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 1, pp. 89‐99, January–February, 2009.     

Physical model of low-velocity detonation in plasticized HMX

A physical model of low-velocity detonation in plasticized HMX is considered. In this model, a low-velocity detonation wave is a combination of a weak leading shock wave and a subsequent compression wave. This combination is formed by the simultaneous effects of energy release and spreading of the reacting medium. The main features of low-velocity detonation observed in experiments are reproduced in two-dimensional calculations. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 1, pp. 102–112, January–February, 2008.     

Calculation of the critical detonation diameter of explosive charges using data on their shock-wave initiation

This paper deals with the further development of the quantitative theory of critical detonation diameter that was earlier proposed by the author. According to this theory, to calculate the critical diameter, it is necessary to know the shock adiabat, detonation velocity, and the generalized kinetic characteristic of decomposition of a high-explosive (HE) charge under shock-wave compression. It is suggested that the generalized kinetic characteristic of decomposition of a HE can be found from an experimental dependence of the shock-wave amplitude on the distance the shock wave travels during shock-wave initiation of the HE charge. This approach allows one to calculate the critical detonation diameters of HE charges with sufficient accuracy. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 2, pp. 112–115, March–April, 2006.     

Radiographic study of interaction of shock and detonation waves in a high explosive

Collisions of shock and detonation waves in an HMX-based high explosive are experimentally studied with the use of flash radiography. Based on X-ray patterns, specific features of the wave-interaction process are identified, and qualitative differences are found in detonation formation and evolution in an explosive precompressed by a weak shock wave and in an undisturbed explosive. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 3, pp. 132–138, May–June, 2007.     

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.     

Conditions of detonation initiation by focusing shock waves in a combustible gas mixture

Based on experiments on focusing shock waves in hydrogen-air mixtures and available publications, the critical shock-wave Mach number at which detonation is initiated near the apex of a concave reflector is analyzed as a function of the reflector size and reactivity of the mixture. The effect of the reflector shape and size on the value of this Mach number is studied. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 6, pp. 84–89, November–December, 2007.     

薄环形装药起爆技术研究

设计和压制了一种薄型起爆药片及环形药柱,并对其隔爆和起爆能力、可靠性和同步性进行了测试研究。采用环形装药起爆可以有效地提高聚能装药的威力,而且其威力随着环形装药直径的增加而增加。研究结果对于传爆序列的可靠性和起爆技术的研究有重要的参考价值,可用于聚能装药的起爆,提高其作战能力。     

Effect of a nanosecond gas discharge on deflagration to detonation transition

The possibility of using a high-voltage nanosecond discharge to initiate gaseous detonation was shown experimentally. The experiments were performed with C₃H₈ + 5O₂ and C₃H₈/C₄H₁₀ + 5O₂ + xN₂ (x = 0–10) mixtures at an initial pressure of 0.15–0.6 atm. The discharge was initiated by a voltage pulse of duration ≈60 nsec and amplitude 4–70 kV; the energy input was 0.07–12 J. Under the conditions of the experiment, three flame propagation regimes were observed: slow combustion, transient detonation, and Chapman—Jouguet detonation. For the initiation of the C₃H₈+ 5O₂ mixture in a tube of diameter 140 mm, the length of the deflagration to detonation transition was 130 mm at an initial pressure of 0.3 atm and an initiation energy of 70 mJ. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 2, pp. 80–90, March–April, 2006.     

Reliability of kinetic data used for estimating multifront detonation parameters

A faster increase in the cell size and other important parameters of multifront detonation than that predicted by kinetic calculations is obtained for fuel-oxygen mixtures of hydrogen and typical hydrocarbons diluted by nitrogen. In a stoichiometric hydrogen-oxygen mixture diluted by an additional amount of oxygen or hydrogen, experimental and calculated data are also found to diverge with increasing concentration of the added species. This effect, however, is not observed if these mixtures are diluted by helium or argon. An assumption about the reason for this difference in data is put forward. A conclusion is made that kinetic data should be corrected as applied to detonation conditions. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 3, pp. 89–94, May–June, 2009.     

Parametric study of shock-wave formation in a spatially inhomogeneous self-igniting medium for arrhenius combustion kinetics

An approach to describing the formation and propagation of small gas-dynamic perturbations in a spatially inhomogeneous self-igniting medium for arbitrary chemical reaction kinetics was developed in a previous paper. In the present paper, the proposed approach is illustrated by studying the problem for a simple reaction with an Arrhenius reaction rate. A comparison of calculation results with the solution of the complete system of gas dynamics equations shows that the approach provides good accuracy of quantitative estimates. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 2, pp. 76–83, March–April, 2008.     

Initiation of detonation in flows of fuel-air mixtures

Regimes of self-ignition of the fuel mixture obtained by controlled separate injection of hydrogen and air into a plane-radial vortex chamber with a rapid (0.2 msec) transition to detonation have been realized for the first time. Self-ignition occurs in the stoichiometric region with a slightly higher (up to 6–30%) content of hydrogen and, normally, in a subsonic flow. The energy of guaranteed detonation initiation is determined for combustors of different geometries and different ratios of fuel components by using a thermal pulse produced by blasting a wire by electric current. Detonation initiation is ensured by using energy of 0.1 J. It is found that the main contribution of energy into the flow of the mixture occurs at the stage of evaporation (ionization) of copper of the blasted wire. The continuous spin detonation regime is found to decay as the exit cross section of the combustor is reduced. In the regime of combustion, both detonation and conventional turbulent combustion, the pressure at the periphery of the plane-radial vortex chamber is lower and the pressure at the edge of the exit orifice is higher than that in the case of exhaustion of cold fuel components. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 3, pp. 110–120, May–June, 2007.     

含铝典型炸药爆轰参数计算研究

用途不同,对炸药的爆速、爆压、爆热要求不一样。准确、快速计算炸药的爆轰参数对于设计指定性能新型炸药和炸药的应用研究具有十分重要的意义。本文用不同的方法对含铝炸药的爆轰参数进行了计算,采用含铝炸药经验公式计算含铝炸药的爆速、ω-Г公式方法计算的爆压、盖斯定律计算爆热,较其他计算方法计算结果相对误差小。     

用电磁粒子速度计实验研究一种TATB基钝感炸药的冲击响应

针对一种新的TATB基钝感炸药(Tx),应用组合式电磁粒子速度计(EMV)测试技术,测量了炸药直接加载、增加有机玻璃隔板以及炸药驱动飞片3种加载状态下炸药内部的粒子速度历程和冲击波轨迹。根据测试结果,分析了不同加载压力下炸药的冲击响应过程。结果表明,炸药直接加载时,加载压力最高,Tx钝感炸药很快达到爆轰状态,到爆轰距离约为1.5mm;在增加有机玻璃隔板、加载压力为14.2GPa时,与直接加载时炸药粒子速度一致,Tx钝感炸药的到爆轰距离明显增加,约为5mm;在炸药驱动飞片、加载压力为9.5GPa时,Tx钝感炸药的粒子速度逐渐降低,存在一定钝化现象,到爆轰距离达到20mm以上。     

Numerical simulation of shock-wave initiation of heterogeneous detonation in aerosuspensions of aluminum particles

Numerical simulations of flows of reacting two-phase media in a two-velocity, twotemperature approximation are used to study the shock-wave initiation of detonation in aerosuspensions of aluminum particles in oxygen. The conditions in a high pressure chamber under which detonation can develop after rupture of a diaphragm are determined. Two initiation scenarios are established that depend on the localization of the initiation source. It is shown that initiation brings on a self-sustained detonation regime (Chapman-Jouguet or incompletely compressed, depending on the relaxation parameters). The required initiation energy is estimated and ignition criteria are formulated. The possibility of detonation initiation when insufficiently strong shock waves are reflected from a rigid wall is discussed. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 3, pp. 81–88, May–June 1999.     

Relation between the critical detonation diameter of explosive charges with characteristics of their shock-wave sensitivity

Correlation dependences between the critical diameter of high explosive (HE) charges and characteristics of their shock-wave sensitivity are theoretically justified. Relations for the critical radius of curvature of the detonation-wave front and for the critical detonation diameter are derived on the basis of the author’s theory of the critical diameter and the generalized kinetic characteristic of HE decomposition determined from the experimental dependence of the distance of transition of the initiating shock wave to the detonation wave on the wave amplitude. A qualitative analysis of these relations reveals good agreement with available experimental data. Key words: detonation, critical diameter, sensitivity, shock-wave initiation of detonation, HE decomposition kinetics. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 3, pp. 101–105, May–June, 2009.     

Measuring the brightness temperature of a detonation front in a porous explosive

The detonation temperature of pressed PETN grains with a relative volumetric concentration of air pores of 0.0047–0.147 was measured using an optical fiber pyrometer at wavelengths of 678 and 487 nm. The nonequilibrium nature of the radiation of the detonation front was shown to be due to the presence of two radiation sources with different temperatures. One source was the explosion products and the other was the strongly compressed air pores, in which air was heated to a temperature above 10⁴ K. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 4, pp. 108–110, July–August, 2007.     

Modified detonation macrokinetics model of a tatb-based explosive

A one-stage detonation macrokinetics model of a low-sensitivity heterogeneous explosive is considered. Within the framework of the model, we have managed to describe uniformly a wide class of experiments on initiation of aTATB-based plasticized explosive, including the initiation from the impact by a metallic plate and compact metallic fragments. Institute of Technical Physics, Snezhinsk 456770. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 1, pp. 94–97, January–February, 1997.     

Energy aspects of initiation of domestic gases

Calculated and experimental data are presented on the most important parameters of combustion and detonation of ethane, propane, and butane in mixtures with oxygen and air, diluted by inert gases, with variations in the initial pressure. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 1, pp. 96–101, January–February, 2008.     

TATB基含铝炸药作功能力的试验研究

为评价TATB基含铝炸药的作功能力,通过ANSYS-LSDYNS软件,采用Lee-Tarver点火增长三项式模型模拟含铝炸药的圆筒试验,获得了含铝炸药的JWL状态方程及反应速率参数。利用激光位移干涉仪研究了不同铝粉尺寸的含铝炸药加速铜飞片的能力,用数值计算验证了标定的圆筒试验参数。结果表明,粒径较小的铝粉能够使铜飞片获得更大的自由面速度,加速铜飞片的时间缩短,表现为粒径2μm铝粉的含铝炸药反应时间比粒径10μm铝粉的含铝炸药缩短13.6%。计算值与试验结果吻合较好,表明圆筒试验得到的爆轰产物参数是有效的。