Low-velocity Detonation Research Articles

Theoretical calculation and analysis of the velocity of shaped charge jet with modified collapse velocity model

The application of perforating completion technology in oil and gas field development has gained widespread popularity. Enhancing the efficiency of oil and gas wells relies on increasing the penetration depth, which is influenced by the design of the perforation charge and the strength characteristics of the rock material. However, as a crucial objective function for optimizing perforating charge structures, jet velocity lacks a rapid and accurate calculating method. This article addresses this issue by proposing an improved collapse velocity model using the DP46RDX42-Y perforating charge as a case study. It presents a novel approach for calculating jet velocity based on the unsteady Pugh-Eichelberger-Rostoker (PER) theory. To validate the effectiveness of the proposed method and analyze the impact of different characteristic parameters on jet tip velocity, a series of numerical simulations were conducted using LS-DYNA software combined with Arbitrary Lagrange-Euler (ALE) techniques. Results indicate excellent agreement between the proposed method and the numerical results, demonstrating its superiority over the traditional Gurney formula with an impressive 34.15% increase in accuracy. Notably, this method is particularly suitable for perforating charges with low detonation velocity. Increasing the liner density and decreasing the liner thickness and cone angle is recommended to achieve higher jet tip velocity. Furthermore, the proposed method has the potential for broader application in other perforating charges with varying liner shapes. This study provides a comprehensive and efficient solution for calculating jet velocity, which facilitates optimizing perforating charge structures and calculating penetration depth.

Detonation Performance of Insensitive Nitrogen-Rich Nitroenamine Energetic Materials Predicted from First-Principles Reactive Molecular Dynamics Simulations.

Because of the excellent combination of high detonation and low sensitivity properties of the 1,1-diamino-2,2-dinitroethylene (FOX-7) energetic material (EM), it is useful to explore new energetic derivatives that start with the FOX-7 structure. However, most such derivatives are highly sensitive, making them unsuitable for EM applications. An exception is the new nitroenamine EM, 1,1-diamino-2-tetrazole-2-nitroethene (FOX-7-T) (synthesized by replacing a nitro group with a tetrazole ring), which exhibits good stability. Unfortunately, FOX-7-T shows an unexpected much lower detonation performance than FOX-7, despite its higher nitrogen content. To achieve an atomistic understanding of the insensitivity and detonation performance of FOX-7 and FOX-7-T, we carried out reactive molecular dynamics (RxMD) using the ReaxFF reactive force field and combined quantum mechanics MD (QM-MD). We found that the functional group plays a significant role in the initial decomposition reaction. For FOX-7, the initial decomposition involves only simple hydrogen transfer reactions at high temperature, whereas for FOX-7-T, the initial reaction begins at much lower temperature with a tetrazole ring breaking to form N2, followed by many subsequent reactions. Our first-principles-based simulations predicted that FOX-7-T has 34% lower CJ pressure, 15% lower detonation velocity, and 45% lower CJ temperature than FOX-7. This is partly because a larger portion of the FOX-7-T mass gets trapped into condensed phase carbon clusters at the CJ point, suppressing generation of gaseous CO2 and N2 final products, leading to reduced energy delivery. Our findings suggest that the oxygen balance is an important factor to be considered in the design of the next generation of high-nitrogen-containing EMs.

Experiment and instantaneous driving simulation of explosion dispersion process of central tube for submunition

In order to study the influence of explosion dispersion of submunition on the dispersion velocity and pressure characteristics of subunits, the experimental study of explosive dispersion of the central tube was carried out when the explosives with low detonation velocity were applied in central tube as the main charge. In addition, the explosion dispersion test process was recorded by high-speed photography. RDX-based aluminized explosive samples with low detonation velocity were prepared and tested, and the low detonation velocity performance changes under different charge diameters and densities were obtained. Based on the explosive dispersion test of the central tube of the submunition, the physical model and three-dimensional axisymmetric finite element model of the central tube, subunit and aluminium alloy shell with prefabricated grooves are established. The fluid-structure coupling calculation method is used to simulate the explosive dispersion process. The simulation results are compared with the test results, and the pressure distribution characteristics of the subunit and the variation law of the dispersion velocity are analyzed. The effectiveness of the engineering calculation method of JWL equation model parameters is verified. The results show that using RDX based aluminized low detonation velocity explosive as the main charge of the central tube structure can achieve the design goal of the explosive dispersion for submunition, and the explosion dispersion model of submunition can accurately describe the dispersion characteristics of the subunit. The research results can be used to guide the structural design of submunition warhead.

Detonation Wave Propagation of Double-Layer Shaped Charge and Its Driving Characteristics to the Liner

The double-layer charge can effectively improve the axial driving ability of explosives, which shows a considerable engineering application prospect in highly efficient damage warheads. Due to the complex wave structure produced by the overpressure detonation of a double-layer charge, a series of dynamic behaviors inside the shaped charge liner will be affected. By comparing the detonation wave shapes of single-layer charge and double-layer shaped charge structure and the jet shaping parameters of a double-layer shaped charge with different structural parameters, the evolution of detonation wave and the state parameters in the wave system are analyzed in this research. The research found that the double-layer charge with high detonation velocity in the outer layer and low detonation velocity in the inner layer can produce continuous overpressure detonation, which makes the overpressure detonation state be applied efficiently. Meanwhile, this study found that the overpressure detonation field formed by the double-layer charge changes the action law of the traditional single charge on the shaped charge liner. The detonation waveform of the entire charge is controlled by different detonation velocities and detonation energies, and a detonation waveform that matched well with the shaped charge liner is obtained. This study solves the matching relationship between the structure of the overpressure detonation wave system and the properties of a double-layer charge, which is of great value for improving the detonation-driving effect of condensed explosives on surrounding media. The double-layer charge can effectively enhance the potential of explosive charge. It is not only widely used in military fields such as improving the armor-breaking power of shaped charge penetrators and improving the muzzle velocity and concentration of fragments of directional warheads, but also can promote the development of industrial fields such as explosive processing.

Preparation and Performance of ANPyO/Emulsion Explosive Composite Energetic System

AbstractIndustrial explosives with a low detonation velocity serve as the core‐driven energy source for explosive cladding, but have a limited pressure output. A composite energetic system containing high‐energy explosives/emulsion explosives can overcome this limitation. Accordingly, the search for high‐energy explosives with intrinsic safety features is key to achieving such systems. Therefore, in this study, 2,6‐diamino‐3,5‐dinitropyridine‐1‐oxide (ANPyO) with high‐energy‐insensitivity characteristics was selected as the energetic agent to prepare a composite energetic system with an ANPyO/emulsion explosive, and its safety and energy release effects were systematically studied. The experimental results showed that the content of ANPyO had a “linear” relationship with the apparent density of the developed composite energetic system, and had little effect on its impact and friction safety (the explosion probability was less than 10 %). In addition, the introduction of ANPyO did not have a significant impact on the detonation velocity of the composite energetic system, with an average detonation velocity of 2650 m ⋅ s−1. However, it did effectively improve the pressure output of the composite system. The peak pressure increased by 23.69 % from 27.27 kPa to 33.73 kPa, while the boosting rate increased by 88.09 % from 1256.68 kPa ⋅ s−1 to 2363.70 kPa ⋅ s−1. The improvement in the pressure output endowed the ANPyO/emulsion explosive composite energetic system with excellent work capacity, enabling T2/Q235 to compound well during explosive cladding. The above studies prove that this system can effectively maintain the relationship between the safety and energy output, positively contributing toward the development of explosive cladding technology.

Prediction of concentration of toxic gases produced by detonation of commercial explosives by thermochemical equilibrium calculations

An adverse effect resulting from explosive mine blasts is the production of toxic nitrogen oxides (NO and NO2) and carbon monoxide (CO). The empirical measurements of the concentration of toxic gases showed that it depends not only on the composition of an explosive and properties of its ingredients but also on several other parameters, such as volume of blasting chamber, explosive charge mass and design, confinement characteristics, surrounding atmosphere, etc. That explains why measured concentrations of toxic gases reported in literature significantly differ.In this paper, we discuss the possibility of theoretical prediction of the concentration of toxic gases by thermochemical equilibrium calculation applying two models: ideal detonation model and deflagration model. It can be demonstrated that thermochemical calculations can provide a good estimation of the measured concentrations and reproduce experimentally obtained effects of additives on the production of toxic gases. It was also found that the ideal detonation model applies to heavily confined explosive charges, while the deflagration model is more suitable for low detonation velocity explosives with light confinement.

Attenuation of gaseous detonations by porous media of fine microstructure

This article reports on numerical simulations of detonation propagation in channels that contain one or more porous obstructions. The porous media considered herein have high porosity and are of fine microstructure, i.e. the diameter of the fibres of the solid matrix is smaller than the characteristic chemical length scale. Our study is based on a thermo-mechanical model for flows in superposed porous and pure-fluid regions. According to it, the solid matrix is represented as a rigid continuum and its porosity is introduced as a distribution that varies in space. With regard to chemical kinetics, two different three-step chain-branching schemes are considered; their difference being in the termination reaction. Our simulations predict that, even at high porosity, the porous obstructions act as a highly efficient momentum sink, thereby causing the detonation to attenuate significantly. In the case of a single porous section, the detonation re-initiates downstream via chain-branching explosion. However, arrays of porous zones that span the entire cross section of the domain produce a decoupling of the reaction zone from the leading shock, thereby effectively suppressing the detonation. Also, our study reveals that in domains with arrays of porous blocks that only partially cover the cross section of the channel, the detonations do not quench. Instead, they propagate as low-velocity detonations, the properties of which are elaborated herein as well.

On the Disintegration of A1050/Ni201 Explosively Welded Clads Induced by Long-Term Annealing.

The paper presents the microstructure and phase composition of the interface zone formed in the explosive welding process between technically pure aluminum and nickel. Low and high detonation velocities of 2000 and 2800 m/s were applied to expose the differences of the welded zone directly after the joining as well as subsequent long-term annealing. The large amount of the melted areas was observed composed of a variety of Al-Ni type intermetallics; however, the morphology varied from nearly flat to wavy with increasing detonation velocity. The applied heat treatment at 500 °C has resulted in the formation of Al3Ni and Al3Ni2 layers, which in the first stages of growth preserved the initial interface morphology. Due to the large differences in Al and Ni diffusivities, the porosity formation occurred for both types of clads. Faster consumption of Al3Ni phase at the expense of the growing Al3Ni2 phase, characterized by strong crystallographic texture, has been observed only for the weld obtained at low detonation velocity. As a result of the extended annealing time, the disintegration of the bond occurred due to crack propagation located at the A1050/Al3Ni2 interface.

Mixed Fuel in the Low-Velocity Detonation Mode

Mixed Fuel in the Low-Velocity Detonation Mode

Transition of Convective Combustion into Low-Velocity Detonation in a Low Porous Stochiometric Mixture of Ammonium Perchlorate with Polymethyl Methacrylate in a Device with Mass Ejection

Transition of Convective Combustion into Low-Velocity Detonation in a Low Porous Stochiometric Mixture of Ammonium Perchlorate with Polymethyl Methacrylate in a Device with Mass Ejection

Effects of Isothermal Wall Boundary Conditions on Rotating Detonation Engine

ABSTRACT Three-dimensional numerical simulations of rotating detonation engines (RDEs) are reported with stoichiometric hydrogen/air mixtures using Navier-Stokes equations with non-slip walls. The effects of isothermal wall boundary conditions at 300 K, 600 K and 900 K are investigated and further compared with the simulation under adiabatic walls. With isothermal walls of 300 K, axial detonation is formed, which further leads to the quenching of detonation. With 600 K isothermal walls, the detonation wave has a similar stably propagating process as adiabatic walls. However, due to the wall heat loss, a lower detonation velocity is obtained in the simulation with isothermal walls. With 900 K isothermal walls, it is found that detonation quenches at first due to the high temperature of the walls, then re-initiates as a result of the collisions of shock waves. In addition, the temperature and heat flux distributions in the outer wall are analyzed. Both the peak temperature and heat flux are found to appear at the detonation wavefront. The averaged heat flux in the detonation region is about three times of the averaged heat flux evaluated in the outer wall. Moreover, the averaged temperature and heat flux remain nearly unchanged in the post-detonation region. Our results are in agreement with experimental studies and provide some insights for RDE thermal management.

Rotating Detonation: History, Results, Problems

Abstract Among of modern papers devoted to numerical modeling of rotated waves the greater part of papers are based on assumption that such wave propagates with velocity equals to the Chapman-Jouguet velocity of ideal detonation model with plane front. But the experimental velocities of rotated detonation waves, as a rule, are less (and even much less) the velocity of ideal Chapman-Jouguet detonation. Such regimes are named as low-velocity detonation or quasi-detonation and its characteristics are practically not investigated carefully. Moreover, similar to the spinning detonation, the strong connection of velocity of rotated transverse waves with the acoustic waves of reaction products was observed. So the new model with an allowance for the losses of impulse and energy must be used at numerical modeling of RDE and new experimental investigations of regimes with understated velocity must be carried out. In given paper some important aspects of rotated detonation waves and new experimental results are analyzed: the multifront system of rotated waves; correlation of rotation velocity of waves with acoustic characteristics of reaction products; streak-records trajectory of rotated waves on moving film; pressure and temperature profiles of rotating waves; velocity deficit and energy-release.

Aluminum-to-Steel Cladding by Explosive Welding

The production of aluminum-carbon steel and aluminum-stainless steel clads is challenging, and explosive welding is one of the most suitable processes to achieve them. The present work aims to investigate the coupled effect of two strategies for optimizing the production of these clads by explosive welding: the use of a low-density interlayer and the use of a low-density and low-detonation velocity explosive mixture. A broad range of techniques was used to characterize the microstructural and the mechanical properties of the welds, specifically, optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, electron backscatter diffraction, microhardness and tensile-shear testing with digital image correlation analysis. Although aluminum-carbon steel and aluminum-stainless steel have different weldabilities, clads with sound microstructure and good mechanical behavior were achieved for both combinations. These results were associated with the low values of collision point and impact velocities provided by the tested explosive mixture, which made the weldability difference between these combinations less significant. The successful testing of this explosive mixture indicates that it is suitable to be used for welding very thin flyers and/or dissimilar materials that easily form intermetallic phases.

Research on the interfacial microstructure of three-layered stainless steel/Ti/low-carbon steel composite prepared by explosive welding

ABSTRACT The stainless steel/Ti/low-carbon steel trimetallic composite plate was successfully fabricated by the explosive welding technique using honeycomb aluminum structure low detonation velocity emulsion explosive. The interfacial microstructure characterizations, elemental distribution, phase transformation and hardness were characterized using optical microscopy (OM), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and micro-hardness tester. The results indicated that the trimetallic sheet of stainless steel/Ti/low-carbon steel was successfully welded without visible defects and have an excellent bonding quality. The Ti/;ow-carbon steel joining interface had a typical wavy structure and formed about 3 µm thick transition layer. The stainless steel/Ti joining interface had an almost flat structure; meanwhile, the phase transformation of Fe and Ti and the texture occurred at the joining interfaces. The hardness increased near the welding interface and sharply increased in the melted zones.

Specific Features of the Initiation and Propagation of Low-Velocity Detonation in the High-Density Charges Based on Ammonium Perchlorate Mixtures with Combustible Additives

The propagation features and critical conditions of low-velocity detonation (LVD) in the high-density charges of finely dispersed ammonium perchlorate (APC) mixtures with combustible and explosive additives are studied. The effect of the relative charge density, the combustible component type, and the ratio of mixture components, including the mixtures strongly enriched with a combustible agent, on the propagation of detonation is considered. It is shown that the dependence of the detonation velocity on the relative charge density in the case of APC mixtures with combustible additives has a plateau-like region, in which the detonation velocity is at a level of 2000 m/s and is practically independent of the density and nature of the combustible component. Moreover, the critical charge density, above which the failure of LVD is observed, is revealed. In the case of ternary mixtures with a liquid explosive (nitromethane) additive, there is no similar dependence, and the detonation velocity monotonically grows with an increase in the relative density. The critical initiation pressures of compositions are also determined within the density range, where the density has no effect on the detonation velocity. The performed studies make it possible to refine the composition and characteristics of high-density mixtures, for which the application of LVD regimes can ensure the creation of efficient explosion-proof impulse devices.

Dependence of Detonation Velocity of Explosives on Effective Atomic Number and Effective Electron Density of the Explosives

Detonation velocity is one of the most important characteristics of explosives. For solid hydro carbon-based explosives it is generally greater than 4000 m/s. Detonation velocity depends to some extent upon the particle size of the explosives, increased charge diameter and increased confinement of the explosive. There is no report indicating the dependence of detonation velocity on the effective atomic number and effective electron density of the explosive. In the present work, we have arbitrarily chosen eight explosives. Four of these have detonation velocity between 9400 and 10100 m/s, and the other four has detonation velocity between 4500 and 5300 m/s. Direct method was used to calculate effective atomic number and effective electron densities various explosives. On calculating effective atomic number and effective electron density, it was found that detonation velocity of explosives does depend upon these two parameters. For explosives with high detonation velocity, effective atomic number is high and effective electron density is low while for low detonation velocity explosives it is reverse. It was also found that the variation of effective atomic number and effective electron density as a function of gamma ray energy can be explained on the basis of three different gamma ray inter action mechanism of gamma rays with matter.

AEE-active conjugated polymers based on di(naphthalen-2-yl)-1,2-diphenylethene for sensitive fluorescence detection of picric acid

Picric acid (PA) is an archetypal explosive material that possesses low safety coefficient and high detonation velocity. The development of reliable and effective sensors for PA using PL spectroscopy methods is practically significant. Among various PL sensors, conjugated polymers have emerged as a class of fascinating candidates for the detection of PA due to the “molecular wire” sensing mechanism. In this work, we synthesized and characterized two new di (naphthalen-2-yl)-1,2-diphenylethene (DNDPE)-based conjugated polymers with different conjugation degree and hydrophilicity. They show good solubility, aggregation-enhanced emission (AEE) feature and high photostability. Both polymers exhibit sensitive fluorescence quenching by PA, and the KSV at the initial stage of the Stern–Volmer plots is up to 9.8 × 105 M−1. In addition, after exposure to UV light, these polymers still could effectively detect the PA in water. They also could on-site detect PA with high sensitivity by preparing the polymer-immobilized fluorescent test strips. The results demonstrate that these new DNDPE-based conjugated polymeric sensors could be good candidates for the sensitive detection of PA.

Study on Overdriven Detonation of Double‐Layer Shaped Charge

AbstractOverdriven detonation(ODD) means that the detonation process of explosives no longer follows the C−J detonation process and its detonation parameters are larger than the C−J values. ODD is an unstable detonation process. With the increasing of propagation distance, detonation parameters tend to C−J value gradually. The double‐layer shaped charge (DLSC) with high detonation velocity explosive (HE) in the outer layer and low detonation velocity explosive (LE) in the inner layer can keep the axis of shaped charge in the ODD state all the time. The paper derived formulas for calculating the parameters of overdriven detonation when the HE detonates the LE. Based on the conservation of momentum, mass and energy, the functional relationship between the intensity of Mach wave and the incident angle of the detonation wave in the shaped charge is deduced. Study on the propagation law of detonation waves in DLSC with the wave shaper by numerical simulation. The results show that the peak value of Mach wave pressure in DLSC is not increased compared with that in ordinary shaped charge (OSC), but the attenuation speed of Mach wave pressure can be delayed and ultimately in the ODD state. The final parameters of the ODD state are determined by the detonation velocity and the polytropic exponent of the explosive. The results of numerical simulation are consistent with theoretical calculation, which confirms the accuracy of the formulas.

Behavior of Low-Velocity Detonation in Stoichiometric Mixture of Ammonium Perchlorate and Polymethyl Methacrylate

Low-velocity detonation in mixtures of ammonium perchlorate and fuel additives in high relative density charges is an interesting subject for the scientific research, with potential for practical applications in pulse nozzle and projective setups. However, information about the process is scanty and mainly concerns the measurements of the wave propagation velocities. This paper describes the results of a research aimed at obtaining the data base on properties and behavior of low-velocity detonation (LVD) in pressed charges of the mixture of ammonium perchlorate and 15% polymethyl methacrylate. The firings have been fulfilled at the pulse laboratory projectile setup and the strong steel confinements equipped with the nozzle block or a projectile with the process initiated by a booster produced from RDX or the TNT/RDX 30/70 mixture. The thrust impulse, trajectory of the projectile, pressure, and LVD wave front trajectory have been recorded. According to the measurement results, the muzzle velocity, the pressure at the projectile, and the burning completeness of the mixture have been calculated. In the experiments, the relative charge density has varied from 0.85 to 0.96, the ammonium perchlorate particle size has been from 20 to 200 μm, and the charge length and the projectile mass have varied as well. The experiments were supplemented with numerical simulation. Emphasis was lain on the interaction of a low-velocity detonation wave with end rarefaction waves. The conditions under which the high completeness of chemical conversion of the mixture can be reached with the acceptable level of the maximum pressure (1–1.5 GPa) are considered.

Influence of base material properties on copper and aluminium–copper explosive welds

ABSTRACTThe influence of base material properties on the interfacial phenomena in copper and aluminium–copper explosive welds was studied. Two explosive mixtures with different detonation velocities were tested. Sound aluminium–copper joints with effective bonding were achieved by using an explosive mixture with a lower detonation velocity. High energy explosives led to extensive interfacial melting, preventing the production of consistent dissimilar welds. Unlike to the similar copper joints, the aluminium–copper welds presented very asymmetrical interfacial waves, rich in intermetallic phases and displaying a curled morphology. The interaction of the materials in dissimilar welding was found to be completely different depending on the positioning of each alloy in the joint, i.e. positioned as the flyer or as the baseplate.