Interaction of detonation products of a cylindrical high-explosive charge with a surrounding gas (original) (raw)
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Combustion, Explosion, and Shock Waves, 1985
The movement of detonation products and ambient gas after detonation of a linear explosive charge in the atmosphere is investigated. Main attention is devoted to flow at large distances from the detonation wave (much greater than the charge radius). Flow was investigated earlier in [1] with respect to the propagation of shock waves in the atmosphere during movement of meteorites, initiation of detonation in other media, and determination of the effect on the walls of an explosion chamber. In these works mainly movement of the shock wave in the atmosphere (in air) was studied and the movement of the detonation products themselves were ha=dly considered. The principal of energy similarity [i] was used for describing the dependence of the characteristics of the shock wave on the properties of the explosives. In the present work, which is a continuation of , experimental data are obtained on the movement of shock waves in anatmosphere of various gases (air, helium, argon) and at various pressures, and also on the movement of the detonation products themselves, in particular, their boundary. The jet analogy [4] is used for analyzing flow similarity, which makes it possible to establish the properties of flow similarity as a whole. The conclusions about flow similarity are illustrated by experimental data. The relation of flow similarity is discussed on the basis of the energy principle and jet analogy.
Gaseous detonations—A selective review
Progress in Energy and Combustion Science, 1991
lThis review confines itself to available information on gaseous detonations, including those in aerosols, clouds of flammable dusts and hybrid mixtures, from the standpoint of safety of chemical processing plant. In so doing, it examines recent extensions to work based on the concept of an ideal front with losses (non-ideal theory), showing how this may be applied to derive guidelines on the effects of tube diameter, of wall roughness and of initial pressure of the mixture on the velocity of a steady front. Further extension to the prediction of limits is considered for conditions likely to be experienced in actual plant, where walls are unlikely to be smooth and the presence of inert particles in the explosive medium is a possibility. However, the shortcomings of such an approach in dealing with the interactions of a real front with a complex component of plant is recognised. The experimental techniques which have been used to reveal the complex nature of real fronts are reviewed, prior to a description of studies of the structure of fronts which propagate transversely across the leading front and on how this structure is influenced by the properties of the explosive medium. Finally, experimental work on both non-reactive shocks and detonations in changing configurations of confinement is examined, in terms of possible measures for both reducing the destructive potential of a detonation and obtaining reliable design criteria for chemical plant. CONTENTS I. Introduction 328 2. Non-Ideal Detonations 2.1. Opening remarks 2.2. Detonation mechanisms in rough tubes 2.3. Theoretical considerations 2.4. Momentum and heat losses 2.5. Determination of momentum losses from shock attenuation 2.6. Detonations with homogeneous and boundary layer ignition 2.7. Influence of wall roughness on detonation velocity 2.8. Critical pipe diameter 2.9. Detonation in gaseous suspensions of inert particles 2.10. Detonation of gaseous mixtures in presence of evaporating particles 2.11. Comparison of experimental data with non-ideal unidimensional theory 2.12. Analysis of experimental data on dust clouds 3. Experimental Techniques 3.1. Opening remarks 3.2. Soot track method 3.3. Use of rings and gauges 3.4. Optical methods 3.5. Ionisation methods 4. Real Detonation Fronts 4.1. Opening remarks 4.2. Wave systems created by diffraction of shocks in inert media and their relationship to detonations 4.3. Uni-dimensional models of detonations 4.4. Initiation and the origin of structure 4.5. "Galloping' waves 5. Interactions of Wave Structure with Changes in Confinement 5.1. Opening remarks 5.2. Diffraction of a detonation at an abrupt increase in area 5.3. Methods of reducing and rendering more uniform local pressures 5.4. Reflection of detonation waves 6. Conclusions 364 Acknowledgements References 327
Blast Wave Experiments of High Explosives
Shock wave and high pressure phenomena, 2017
Applications of pyrotechnic materials cover an extensive area: protection of the life and security of the population, satellites, tactical and ballistic missiles, space launchers, aeronautics industry, automotive security (airbags), rail signal devices, perforation charges for petroleum industries, demolition in mines, quarries, buildings, etc. and a large variety of bombs for terrorist attacks. There is a large variety of high explosives which exist on various forms. The use of trinitrotoluene (TNT) as a reference explosive in properties of blast is universal. Hence, it is very important for experiments to have an absolutely reproducible reference. The difficulty is in the use of small charges. The initiator system and the booster occupy a nonnegligible mass. Hence, the expansion of detonation products and the driving mechanism for the blast wave may be affected. The literature of blast properties is well documented (see References) and the analysis conducted here is focused on small charges of TNT, C4 and composition B from experiments realised by the French-German Research Institute of Saint-Louis (ISL) and the French Alternative Energies and Atomic Energy Commission (CEA, Gramat). The properties of blast wave are analysed in terms of overpressure, arrival time, impulse, duration and compared with the abacus of UFC-3-340-2 (U.S. Army Corps of Engineers 2008). Fitted laws are given to calculate the overpressure and arrival time versus scaled distance expressed in terms of mass. The reverse laws are equally established.
The evolution of a detonation wave in a variable cross-sectional chamber
Shock Waves, 2008
A two-dimensional numerical simulation has been performed to study the interaction of a gaseous detonation wave with obliquely inclined surfaces in a variable crosssectional chamber. The weighted essentially non-oscillatory (WENO) numerical scheme with a relatively low resolution grid is employed. A detailed elementary chemical reaction model with 9 species and 19 elementary reactions is used for a stoichiometric oxy-hydrogen mixture diluted with argon. In this work, we study the effect of area expansion and contraction on the main/gross features of the detonation cellular structures in the presence of detonation reflection, diffraction and localized explosion. The result shows that there exists a transition region as the detonation wave propagates through the converging/diverging chamber. Within the transition region, the initial regular detonation cells become distorted and irregular before they re-obtain their regularity. While the ultimate regular cell size and the length of the transition region are strongly affected by the converging/diverging angle, the width/length ratio of the cells is fairly independent of it. A localized explosion near the wall is found as the detonation wave propagates in the diverging chamber.
Combustion and Flame, 2021
The dynamics of detonation transmission from a straight channel into a curved chamber was investigated numerically and experimentally as a function of initial pressure (10 kPa ≤ p 0 ≤ 26 kPa) in an argon diluted stoichiometric H 2-O 2 mixture. Numerical simulations considered the two-dimensional reactive Euler equations with detailed chemistry; hi-speed schlieren and OH* chemiluminescense were used for flow visualization. Results show a rotating Mach detonation along the outer wall of the chamber and the highly transient sequence of events (i.e. detonation diffraction, re-initiation attempts and wave reflections) that precedes its formation. An increase in pressure, from 15 kPa to 26 kPa, expectedly resulted in detonations that are less sensitive to diffraction. The decoupling location of the reaction zone and the leading shock along the inner wall determined where transition from regular reflection to a rather complex wave structure occurred along the outer wall. This complex wave structure includes a rotating Mach detonation (stem), an
Shock Waves, 2017
This paper overviews a complete method for the characterization of the explosive energy output from a standard detonator. Measurements of the output of explosives are commonly based upon the detonation parameters of the chemical energy content of the explosive. These quantities provide a correct understanding of the energy stored in an explosive, but they do not provide a direct measure of the different modes in which the energy is released. This optically based technique combines high-speed and ultra-high-speed imaging to characterize the casing fragmentation and the detonator-driven shock load. The procedure presented here could be used as an alternative to current indirect methodssuch as the Trauzl lead block test-because of its simplicity, high data accuracy, and minimum demand for test repetition. This technique was applied to experimentally measure air shock expansion versus time and calculating the blast wave energy from the detonation of the high explosive charge inside the detonator. Direct measurements of the shock front geometry provide insight into the physics of the initiation buildup. Because of their geometry, standard detonators show an initial ellipsoidal shock expansion that degenerates into a final spherical wave. This non-uniform shape creates variable blast parameters along the primary blast wave. Additionally, optical measurements are validated using piezoelectric Communicated by A. Higgins.
Analytical Study of the Oblique Ree ection of Detonation Waves
The governing equations relating the ow properties across an oblique detonation wave were reconsidered and modi ed by accounting for different heat capacity ratios on both side of the detonation wave. Using these equations, modi ed two-and three-shock-theory-based models were developed and applied to the re ection of detonation waves. The present model makes it possible to investigate the behavior of detonation wave re ections near and at the Chapman-Jouguet (CJ) point. It was shown that the properties of detonation waves near the CJ point are very sensitive to the value of the overdrive. The analytical results were compared with experimental and numerical results from various laboratories, and in general, good agreement was obtained. Nomenclature a = sound speed c v ; c p = speci c heat capacities at constant volume and at constant pressure h = enthalpy M = Mach number of detonation or shock wave P = pressure q = heat of reaction R = speci c gas constant T = temperature U D = velocity of the detonation wave u = ow velocity V = speci c volume ® = overdrive°= speci c heat capacities ratio µ = ow de ection angle µ w ; ± = wedge angle ½ = density Á = angle of incidence  = angle of triple point trajectory Subscripts and Superscripts CJ = Chapman-Jouguet detonation D = detonation wave det = detachment point i = incident detonation wave inert = inert ow j = numbers of ow region, 0, 1, 2, 3 m = Mach stem reactive = reactive ow S = shock wave tr = regular re ection to Mach re ection transition
An experimental investigation of the direct initiation of cylindrical detonations
Journal of Fluid Mechanics, 2003
The direct initiation of gaseous detonation is investigated experimentally in the cylindrical geometry. By using a long source of energy deposition along a line (i.e. pentaerythritoltetranitrate (PETN) detonating cord), undesirable charge initiation and confinement effects are eliminated. This permitted the different flow fields of direct initiation of detonation to be studied unambiguously. Although the detonation velocity in the detonating cord is finite, it was sufficiently large compared to the acoustic velocity in the surrounding gas to permit the different flow fields to be investigated within the hypersonic analogy framework, by which the detonating cord synchronizes a continuous series of cylindrical initiation events along its length. The hypersonic approximation was validated in experiments conducted in a non-reactive medium (air). In the supercritical regime of initiation in combustible gas, stable oblique detonations were observed, confirming their existence and stability. In the critical regime, the onset of detonation was observed to occur consistently from stochastic detonative centres. These centres appeared during the initial decay of the blast wave to sub-Chapman-Jouguet (CJ) velocities. The photographic evidence revealed the three-dimensional details of the detonation kernels' amplification. The present results in the cylindrical geometry are further used to discuss criteria for direct initiation of detonations. In conjunction with previous experiments in the spherical and planar geometries, a criterion for direct initiation is found to involve a critical decay rate of the reacting blast wave. In light of the experimental evidence of the inherent three-dimensional effects during the initiation phase, the strict one-dimensionality of current theoretical models is discussed.