Combustion heat of the Al/B powder and its application in metallized explosives in underwater explosions

An underwater explosion test is used to determine the detonation properties of metallized explosives containing aluminum and boron powders. An oxygen bomb calorimeter (PARR 6200 calorimeter, Parr Instrument Company, USA) is used to obtain the heat of combustion of the metal mixtures. As the content of boron powders is increased, the heat of combustion of the metal mixtures increases, and the combustion efficiency of boron decreases. The highest value of the combustion heat is 38.2181 MJ/kg, with the boron content of 40%. All metallized explosive compositions (RDX/Al/B/AP) have higher detonation energy (including higher shock wave energy and bubble energy) in water than the TNT charge. The highest total useful energy is 6.821 MJ/kg, with the boron content of 10%. It is 3.4% higher than the total energy of the RDX/Al/AP composition, and it is 2.1 times higher than the TNT equivalent.     

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.     

Effect of Mixing Methods on the Thermal Stability and Detonation Characteristics of Ammonium Nitrate and Sodium Chloride Mixtures

A study has examined the effect of mixing methods on the thermal stability and detonation characteristics of ammonium nitrate (AN) and sodium chloride (NaCl) mixtures. NaCl was mixed with AN by two methods. The thermal stability, detonation velocity and structural properties were investigated by differential scanning calorimetry (DSC), measurement of detonation velocity and X‐ray diffraction (XRD). For the mechanical mixing method, in all tested scope of proportions of NaCl in the mixtures, activation energies increase when the proportion of NaCl increases; for solution mixing method, the activation energies decrease first and then start to increase as the proportion of NaCl increases. The detonation velocity of AN‐NaCl mixtures prepared by two mixing methods also showed different results. The results indicate that the mixing methods significantly affect the thermal stability and detonation characteristics of AN.     

Mathematical modeling of detonation suppression in a hydrogen-oxygen mixture by inert particles

The paper addresses the problem of searching for methods that can control, suppress, and attenuate explosive and detonation processes in homogeneous and heterogeneous media (mixtures of reactive gases and inert species). The analysis is performed by analytical and numerical methods. The problem of detonation suppression in a mixture of reactive gases and inert species (argon and sand particles) in a one-dimensional unsteady flow is formulated, and its solution is given. The effect of the particle diameter and concentration on the detonation velocity is determined; the parameters of the detonation wave in a stoichiometric hydrogen-oxygen mixture diluted by a chemically inert gas (argon) and particles is determined. The influence of the initial parameters of the mixture on the possibility of detonation suppression by inert particles is studied. It is shown that the detonation velocity substantially decreases with increasing volume fraction of particles. A decrease in the particle size with an unchanged volume fraction is also found to reduce the detonation velocity.     

Deflagration-to-detonation transition in isopropyl nitrate mist/air mixtures

The characteristics and stages of the deflagration-to-detonation transition (DDT) in isopropyl nitrate (IPN) mist/air mixtures are studied and analyzed. A self-sustained detonation wave forms, as is observed from the existence of a transverse wave and a spinning wave structure. The run-up distance of the DDT process and the pitch size of the self-sustained spinning detonation wave in IPN/air mixtures are analyzed. Moreover, a retonation wave forms during the DDT process. Two propagation modes, the high-speed deflagration mode and the self-sustained detonation mode, of the shock-reaction complex (SRC) in IPN mist/air mixtures are found and analyzed. The influence of the mist concentration on the SRC propagation mechanism is studied. The minimum and the optimum IPN mist concentrations for DDT occurrence in IPN mist/air mixtures are determined. The propagation velocity and overpressure of the self-sustained detonation wave in IPN mist/air mixtures are measured and calculated.     

Dynamics of the detonation-wave front in solid explosives

The important role of the shape of the front during detonation wave propagation in gas mixtures was substantiated by K. I. Shchelkin during construction of the theory of spinning detonation. Subsequently, a unique relationship between the curvature of the front and detonation wave parameters has been repeatedly confirmed in experiments, including for condensed high explosives (HEs). The existence of this relationship formed the basis of the theory of the dynamics of the detonation front which had been developed by the end of the 20th century. This paper presents the results of a study of detonation front propagation in cylindrical samples of a low-sensitivity HE of different diameters with one-point and plane-wave initiation. A unique relationship between the detonation velocity and the curvature of the detonation wave front has been found. Ordinary differential equations describing two-dimensional steady-state detonation front profiles for HE charges in the form of a plate, a cylinder, and a ring were derived assuming that the detonation velocity depends on the curvature of the front. It was taken into account that the boundary angle between the normal to the front and the HE edge is unique for each combination of HE and liner material. It was found that the same detonation front profile corresponds to several combinations of liner material and the determining size of the charge (plate thickness, radius of the cylinder or the inner radius of the ring). A comparison of experimental front profiles near the edges of HE charges for these combinations provides data on the dependence of detonation velocity on the curvature of the front at low velocities corresponding to shock-induced detonation regimes. Analysis of previously obtained data for detonating ring charges of low-sensitivity HEs shows that as the detonation velocity decreases, the total front curvature tends to a limit of about 0.05 mm⁻¹, i.e., of the order of the inverse critical diameter. The limit of the front curvature allows predicting the critical detonation diameter.     

Continuous spin detonation of synthesis gas-air mixtures

Regimes of continuous detonation burning of synthesis gas-air mixtures in transverse (spinning) detonation waves are obtained for the first time in an annular cylindrical flow-type combustor. Carbon oxide-hydrogen mixtures with volume proportions of [CO]/[H₂] = 1/1, 1/2, and 1/3 are studied in a wide range of fuel-to-air equivalence ratios. The maximum detonation wave velocity equal to 1.57 km/s is observed for the mixture of CO + 3H₂ + air with a moderate (about 15%) excess of the fuel. The limits of existence of continuous detonation in terms of the equivalence ratio and the minimum specific flow rate of the mixture are determined. The range of detonation regimes obtained is constructed in the coordinates of the equivalence ratio-specific flow rate of the mixture.     

Structure of detonation waves in tetranitromethane and its mixtures with methanol

A VISAR laser interferometer was used to measure mass velocity profiles in steady-state detonation waves in tetranitromethane and its mixtures with methanol. In the experiments with tetranitromethane, the chemical-spike pressure was found to be 1.7 times higher than the Chapman-Jouguet pressure. In mixtures with nearly stoichiometric methanol concentrations, the detonation front remained stable, but the chemical-spike amplitude increased suddenly and the shock broadened, probably due to the decomposition of the explosive at the front. A 50% increase in methanol concentration led to instability of the detonation front manifested in oscillations in the mass velocity profiles. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 3, pp. 95–100, May–June, 2009.     

Detonation velocity of BTNEN/Al

The effect of the addition of Al on the detonation velocity of bis(2,2,2-trinitroethyl) nitramine (BTNEN) was studied experimentally. It is shown that the dependence of the detonation velocity of BTNEN on the initial density is nearly linear, and a 75/25 BTNEN/Al mixture is characterized by an increase in the slope of the dependence with increasing density. The addition of Al decreases the detonation velocity of BTNEN. The density range characterized by a maximum decrease in the detonation velocity is determined. A comparison of experimental detonation velocities of BTNEN/Al mixtures with literature data obtained by calculations taking into account a possible change in the phase state of Al₂O₃ showed that the thermodynamic model used in the calculations needs to be improved. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 4, pp. 125–130, July–August, 2006.     

The Critical Energy of Direct Initiation in Liquid Fuel‐Air and Liquid Fuel‐RDX Powder‐Air Mixtures in a Vertical Detonation Tube

Multiphase cloud detonation is an important but complex process, which has not been fully understood yet. Direct experimental data about the critical initiation energy (CIE) and pressure/velocity revolution of high explosive powder‐based multiphase cloud detonation is not available in the literature. In this paper, propylene oxide (PO), petroleum ether (PE), isopropyl nitrate (IPN), and a mixture of PE/IPN were individually dispersed to form a cloud in a 200 mm×5400 mm vertical detonation tube. Subsequently, this cloud was directly ignited by a high explosive. The critical initiation energy of various mist/air mixtures was measured by the up and down method. Meanwhile, the pressure history was recorded by six sensors along the detonation tube. RDX powder was added to the system and sprayed simultaneously with the liquid fuel to form a three‐phase gas‐liquid‐solid explosive cloud. The detonation pressure and velocity of all three‐phase cases significantly increased while the corresponding critical initiation energy decreased compared to the liquid‐air analogs. The CIE data were found to have a “U”‐shaped curve relationship to the fuel‐air ratio in two‐ and three‐phase systems, the minimum is always on the fuel‐rich side.     

Explosive Mixtures Detonating at Low Velocity

Same explosive mixtures detonating at a low velocity and not containing high explosives were experimentally investigated. As a system providing detonation capability, a mixture of ammonium nitrate and powdered aluminium was employed. Glass or urea‐formaldehyde resin beads or lead oxides were used to reduce detonation parameters. Detonation velocity and critical diameter were measured for mixtures differentiated in composition and density. As a result of the investigation, a number of explosives were worked out which are characterized by the capability of stable detonation at a very low velocity (below 1000 m/s) and simultaneously, some of them have a relatively high density (even over 2 g/cm³). An attempt of physical and chemical interpretation of the results obtained is also included.     

EAK基熔铸分子间炸药的能量和撞击感度

通过水下爆炸试验研究了RDX和HMX对EAK基熔铸分子间炸药水下能量的影响。结果表明,RDX和HMX对EAK基混合炸药起到明显的增能作用,但对含铝和非含铝体系有不同的作用效果。爆速和撞击感度测定表明,EAK—RDX混合炸药爆轰的理想化程度和稳定性及撞击感度随RDX含量的增加而增加。从能量和撞击感度两个方面综合考虑,RDX的较佳加入量应为20％～30％。     

Effect of AP distribution on energy release characteristics and functional force of HMX/AP/Al explosives

In order to understand the reaction kinetics of HMX/AP/Al ternary system, the different distribution of AP in HMX/AP/Al explosives was realized by two different preparation techniques. Detonation test results show that the detonation velocity, explosion heat and detonation pressure of HAP samples are higher than those of HAl samples, but the extent of improvement is not high, not more than 5 %. The results of scanning electron microscopy showed that AP in HAP samples was distributed on the surface of HMX crystal. AP were dispersed around HMX crystals in HAl samples. The experimental results of explosive fireball performance show that the fireball expansion speed of HAP samples is better than that of HAl samples, demonstrating a good fireball effect. Underwater test results show that the shock wave peak pressure and bubble pulsation period of HAP samples increase by 3.06 % and 7.95 % respectively, and shock wave energy and bubble energy increase by 9.8 % and 25.42 % compared with bubble energy. The experimental results show that HAP samples are superior to HAl samples in accelerating ability of Al flies. The dispersion of AP on the HMX crystal surface promotes the energy release of HMX/AP/Al explosives more.     

Relative Explosive Strength of Some Explosive Mixtures Containing Urea and/or Peroxides

Several mixtures, based on urea derivatives and some inorganic oxidants, including also alumina, were studied by means of ballistic mortar techniques with TNT as the reference standard. The detonation pressure(P), detonation velocity(D), detonation energy(Q), and volume of gaseous product at standard temperature and pressure (STP), V, were calculated using EXPLO5 V6.3 thermochemical code. The performance of the mixtures studied was discussed in relation to their thermal reactivity, determined by means of differential thermal analysis (DTA). It is shown that the presence of hydrogen peroxide in the form of its complex with urea (i.e. as UHP) has a positive influence on the explosive strength of the corresponding mixtures which is linked to the hydroxy-radical formation in the mixtures during their initiation reaction. These radicals might initiate (at least partially) powdered aluminum into oxidation in the CJ plane of the detonation wave. Mixtures containing UHP and magnesium are dangerous because of potential auto-ignition.     

Steady-State Detonation Wave Parameters in a FEFO/Nitrobenzene Solution

This paper gives the results of experimental studies of the reaction zone structure during steady detonation in bis-(2-fluoro-2,2-dinitroethyl)-formal (FEFO, C₅H₆N₄O₁₀F₂) and its mixtures with nitrobenzene (NB). For pure FEFO, the pressure and particle velocity at the Chapman—Jouguet point and the characteristic reaction time were measured. For FEFO/NB, the dependence of the detonation parameters of the mixture on the NB concentration was determined, and the detonation front was shown to be unstable in pure and in mixtures containing more than 30% NB.     

Dependence of detonation velocity on charge density for foamed alumotol (Al/TNT) and TNT mixtures

Experimental data are presented on the dependence of the critical diameter and detonation velocity of cast and liquid porous TNT and TA-15 alumotol (Al/TNT) on charge density. The results of the detonation velocity measurements are compared with calculations. Based on this comparison, it is proposed that the reaction during detonation of alumotol is substantially heterogeneous and this is confirmed by plotting the detonation velocity as a function of density for model mixtures of TNT with various amounts of aluminum and an inert component. Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 4, pp 88–93, July–August 1998.     

Detonation characteristics of ammonium nitrate and activated fertilizer mixtures

To better understand the detonation characteristics of ammonium nitrate (AN) and activated additives mixtures, potassium chloride (KCl) and monoammonium phosphate (MAP) are mixed with AN by different mixing methods. The UN gap test and scanning electron microscopy are applied to study AN and AN-additive mixtures. For the mechanical mixing method, the detonation velocity of AN-additives decreases with increasing the additive proportion, while the detonation velocity of modified AN prepared by the solution mixing method shows the opposite tendency. It is proved that the sensitivity to shock waves increases as the size of AN particles decreases. The type of additives, the mixing methods, and the particle size distribution are important parameters that affect the detonation characteristics of AN.     

Nanometric Aluminum in Explosives

Aluminum nanopowders, because of their larger surface area, can increase the burning rate of propellants. It has been suggested that the powders could also enhance the detonation properties of certain explosives. For these reasons, an experimental study was undertaken to compare the performance of nanometric and micrometric aluminum in various explosives. No enhancement of performance was found in plastic‐bonded explosives. In fact, a reduction of the detonation velocity was found in plastic‐bonded explosives that are based on an energetic binder system. No increase of the detonation velocity was found in mixtures of aluminum and either Composition B or Ammonium Nitrate Fuel Oil, but a small increase in the heat of detonation was measured. The mixture of TNT and nano‐aluminum demonstrated higher detonation velocities and heats of detonation. The increase was higher at small charge diameters. Nanometric aluminum was shown to reduce the critical diameter of such mixtures, and it is concluded that the nano‐aluminum reacts faster than regular micron‐size particles in TNT/Al compositions.     

Detonation characteristics of diluted liquid explosives: Mixtures of nitromethane with methanol

Detonation in mixtures of nitromethane with methanol as an inert (nonexplosive) diluent is studied. Ignition experiments with mixtures in steel tubes of various diameters provided information on the effect of the degree of dilution on detonability. Mass velocity profiles with a chemical spike characteristic of detonation waves were recorded at the unsteady detonation front in all mixtures studied. This made it possible to distinguish the Chapman-Jouguet state and obtain a fairly complete set of detonation parameters. The dependence of the pressure in the detonation products on the methanol concentration is determined, which is required, in particular, to find the true (absolute) limit of detonation propagation for the concentration of diluted liquid explosives using the method proposed and validated by A. N. Dremin. Some results were found to be inconsistent with one-dimensional detonation theory.     

Detonation Performance of TATP/AN‐Based Explosives

The detonation velocity and performance were determined for four mixtures of triacetone triperoxide (3,3,6,6,9,9‐hexamethyl‐1,2,4,5,7,8‐hexoxonane, TATP), ammonium nitrate (AN) and water (W) by cylinder expansion tests. The composition of these mixtures varied in the following ranges: 21–31% TATP, 37–54% AN and 19–32% W. The obtained results were compared with those of powdery 2,4,6‐trinitrotoluene (TNT), AN‐fuel oil explosive (ANFO) and emulsion explosive. It was found that the tested TATP/AN/W mixtures represent typical non‐ideal explosives with relatively low critical diameter and with high sensitivity to initiation despite the high content of water due to the presence of the primary explosive (TATP). The detonation velocity is comparable to that of powdery TNT (at similar density). However, the acceleration ability is significantly lower than that of powdery TNT.