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.     

Solid-state detonation velocity limits

The ranges of solid-state detonation velocities are estimated, based on the volume velocity of sound in the reacting mixture (lower limit) and the wave velocity corresponding to the pressure of polymorphic transformation of the product with formation of a more dense phase (upper limit). The latter values are consistent with gas-dynamic estimates of detonation velocities and correlate with detonation velocities of typical high explosives. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 5, pp. 104–106, September–October, 2007.     

Detonation of a thin explosive layer in evacuated tubes

Detenation of thin layers of dispersed primary and secondary high explosives (HE) on the outer surface of glass and plastic tubes 0.6–3 mm in diameter was examined at an initial air pressure inside the tube of 0.1 MPa to 30 Pa. It is shown that, under these conditions, the air practically does not influence the detonation velocity, which for secondary explosives (PETN, RDX, and HMX), is lower than or approximately equal to the Chapman-Jouguet detonation velocityD _CJ for a homogeneous mixture of the same substances. Experiments with a primary HE (lead azide) revealed regimes with a wave velocity higher thanD _CJ and a varying reaction zone pattern. When tubes containing a layer of a secondary HE were filled with an explosive gas mixture, waves of a hybrid detonation with a velocity both higher and lower than that in the evacuated tubes was observed. In tubes with diameter 2–3 mm, detonation proceeded in a spinning regime over the entire range of the initial pressure and at a velocity higher thanD _CJ. It is concluded that in the evacuated tubes with a thin HE layer on the walls, ignition is transferred by the stream of hot detonation products moving at the head of the detonation wave. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 4, pp. 56–67, November–December 1998     

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 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.     

Gas detonation in a channel with transverse ribs

Results of experiments on detonation propagation in a rectangular horizontal channel with high ribs on the lower wall are presented. The experiments were performed with acetylene-oxygen mixtures. An interval of initial pressures is found, in which low-velocity detonation with a steady velocity of 0.38–0.55 of the Chapman-Jouguet velocity without losses exists. This detonation wave is a system consisting of a shock wave and a flame. Owing to gas outflow to the layer occupied by the ribs, the flame is maintained at a constant distance from the shock wave, which is approximately equal to the free transverse size of the channel. This distance weakly decreases with increasing initial pressure and is almost independent of the burning rate of the gas at standard temperature. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 5, pp. 82–86, September–October, 2007.     

Modeling of weakly nonideal detonation of condensed high explosives with a high content of carbon

A numerical model of weakly nonideal detonation of plastic-bounded TATB is proposed, which alleviates the requirements to the computational grid and necessary computational resources. The model is tested against the experimental results on the dependence of the detonation velocity on the charge diameter and detonation propagation in an annular charge. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 2, pp. 56–60, March–April, 2008.     

Theory of solid-state detonation

The Jouguet theory allows one to estimate the detonation velocity from the known shock adiabat of the product of a solid-state chemical reaction initiated by a shock wave. Using manganese and zinc chalcogenides as an example, it is shown that such estimates are close to experimental detonation velocities in these systems. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 2, pp. 108–110, March–April, 2007.     

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.     

Nonclassical steady-state detonation regimes in pressed TNETB

The reaction zones and the dependence of the velocity of steady-state detonation waves on the initial density of pressed TNETB are studied using a VISAR interferometer. It is shown that, in the range of initial densities of TNETB 1.56–1.77 g/cm³, the propagation of a steady-state detonation wave is possible without the range of elevated pressures (chemical spike) in the reaction zone predicted by the classical theory. The dependence of the detonation velocity on the initial density shows singularities which indicate that a steady-state underdriven regime can occur in this range of initial densities. Based on the well-known theoretical concepts of the hot-spot decomposition mechanism of heterogeneous explosives, it is shown that the possibility of the existence of a steady-state detonation wave without a chemical spike, in particular, underdriven detonation, and the effect of the internal structure of the charge on the detonation regime are explained by the decomposition of explosives at the shock-wave front. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 6, pp. 97–103, November–December, 2007.     

Measurement and calculation of the ideal detonation velocity for liquid nitrocompounds

Results of experimental measurements are presented for the dependence of the detonation velocity on the charge diameter for homogeneous nitromethane and propylene glycol dinitrate and for the ideal detonation velocities for allyl nitrate, diethlyene glycol dinitrate, methylene glycol dinitrate, and ethyl nitrate. Literature data on measurement of the dependence of the detonation velocity on the charge diameter for liquid TNT, nitroglycerin, glycol dinitrate, and methyl nitrate are collected. It is shown that measured values of the ideal detonation velocity are in good agreement with calculated values obtained by the SD method, which uses the equation of state of materials at a high pressure (see B. N. Kondrikov and A. I. Sumin, Fiz. Goreniya Vzryva, No. 1, 1987). A correlation between the ratio of the critical detonation velocity to the ideal velocity and the heat of explosion is obtained, which makes it possible to estimate the limiting value of the latter at which homogeneous liquid nitrocompounds lose detonatability. Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 5, pp. 111–117, September–October 1998.     

Mathematical model of continuous detonation in an annular combustor with a supersonic flow velocity

A two-dimensional unsteady mathematical model of a continuous spinning detonation wave in a supersonic incoming flow in an annular combustor is formulated. The wave dynamics in a combustor filled by a gaseous hydrogen-oxygen mixture is studied. The possibility of continuous spin detonation with a supersonic flow velocity at the diffuser entrance is demonstrated numerically for the first time; the structure of transverse detonation waves and the range of their existence depending on the Mach number are studied. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 6, pp. 83–91, November–December, 2008.     

Determination of nonideal self-sustained detonation regimes of aluminum particles in air

A two-velocity two-temperature model of detonation of aluminum particles suspended in oxygen is employed to study the problem of interaction of a plane detonation wave with an adjacent nonequilibrium rarefaction wave formed with instantaneous removal of the sustaining piston. It is confirmed that the Chapman-Jouguet regimes and weak regimes with a supersonic (with respect to the frozen sound velocity) final state are self-sustained. Stable propagation of the structure is shown for the weak regimes with subsonic (with respect to the frozen sound velocity) and supersonic (with respect to the equilibrium sound velocity) final states (which are unstable in a single-velocity approximation). Interaction of an overcompression wave with a rarefaction wave for relaxation-parameter values that fall into the region of existence of Chapman-Jouguet regimes, results in entry into a Chapman-Jouguet regime. A self-sustained regime of weak detonation that corresponds to the given relaxation parameters is realized outside this region. Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 5, pp. 95–102, September–October 1998.     

Detonation waves in interstellar gas

In astronomy there is a large amount of observational data on the phenomenon of sequential star formation from a single molecular cloud. In this process, a cluster of stars of the same generation creates favorable conditions for the formation of stars of the next generation. A star-forming wave whose velocity is estimated to be10–30 km/sec travels over a molecular cloud of interstellar gas. In the present paper, the self-sustained star-formation phenomenon is claimed to have all features of a detonation process and the star-forming wave is treated as a detonation one. The velocities of the detonation and star-forming waves are estimated to be (∼27 km/sec) and (∼13 km/sec), respectively. Lavrent’ev Institute of Hydrodynamics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 1, pp. 88–93, January–February, 1997     

Continuous spin detonation of hydrogen-oxygen mixtures. 1. Annular cylindrical combustors

A comprehensive numerical and experimental study of continuous spin detonation of a hydrogen-oxygen mixture in annular combustors with the components supplied through injectors is performed. In an annular combustor 4 cm in diameter, burning of a hydrogen-oxygen gas mixture in the regime of continuous spin detonation is obtained. The flow structure is considered for varied flow rates of the components of the mixture and the combustor length and shape. The dynamics of the transverse detonation wave is numerically studied in a two-dimensional unsteady statement of the problem with the geometric parameters of the combustors consistent with experimental ones. A comparison with experiments reveals reasonable agreement in terms of the detonation velocity and pressure in the combustor. The calculated size and shape of detonation fronts are substantially different from the experimental data. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 2, pp. 32–45, March–April, 2008.     

Detonation properties of ammonium nitrate

A published equation for determining the detonation parameters of mixed explosive compositions is used to compute the detonation characteristics. When this equation was used to analyze the detonation parameters of 6ZhV ammonite, the detonation characteristics of the TNT and ammonite in this composition were taken from published data and the parameters of the ammonium nitrate were determined from the equation for the mixture. The results of large-scale experiments on a mixture of no more than 3% TNT with ammonium nitrate are presented. The detonation velocity of ammonium nitrate is found to be 5 km/sec. The equation for the mixture is used to determine the pressure and adiabatic exponent of the explosion products of ammonium nitrate when the size of the explosion exceeds the limiting diameter. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 2, pp. 102–104, March–April 1999     

Continuous spin detonation of hydrogen-oxygen mixtures. 2. Combustor with an expanding annular channel

A comprehensive numerical and experimental study of continuous spin detonation of a hydrogen-oxygen mixture in an annular combustor with the components supplied through injectors is performed. The hydrogen-oxygen mixture is burned in the regime of continuous spin detonation in an annular combustor 4 cm in diameter with subsequent channel expansion. The flow structure is considered for varied flow rates of the components of the mixture and the counterpressure of the ambient medium. The dynamics of the transverse detonation wave is numerically studied in a two-dimensional unsteady gas-dynamic statement of the problem with the geometric parameters of the combustor consistent with experimental ones. Reasonable agreement with experiments is reached in terms of the shape of detonation fronts, detonation velocity, and height of the wave front. The optimal point of channel expansion beginning is chosen, which ensures the maximum specific impulse in the spin detonation regime. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 3, pp. 95–108, May–June, 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.     

Density dependence of detonation velocity for some explosives

The nonmonotonic dependence of the detonation velocity of a cylindrical charge on density for explosives of the 2nd type is due to the effect of the finite charge diameter and is related to an increase in the width of the reaction zone with a reduction in the porosity of the explosive. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 4, pp. 116–124, July–August, 2006.     

Detonation waves in a reactive supersonic flow

A supersonic hydrogen—air flow is studied in detail, in particular, the fields of gas-dynamic parameters and chemical homogeneity of the mixture in various cross sections of the duct. The processes of excitation and propagation of a detonation wave in the downstream and upstream directions are considered. The detonation-wave velocity with respect to the mixture flow is found to differ from the nominal Chapman—Jouguet velocity for a quiescent mixture: the detonation-wave velocity is higher if the wave moves upstream and lower if the wave moves downstream. Some hypotheses on the reasons for these deviations of the experimentally measured velocity from the nominal value are given. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 5, pp. 85–100, September–October, 2006.