Charge Diameter Research Articles

Study on optimization of jet forming of tandem shaped charge warhead

In order to greatly improve the length of shaped charge jet and optimize the jet forming performance, the forming process of a tandem shaped charge structure with reverse detonation mode was numerically simulated. The effects of the rear and front stage liner thickness on the jet length, jet head velocity, jet kinetic energy and energy conversion rate were analyzed respectively using LS-DYNA finite element analysis software. Then the optimal thickness of the front and rear stage liner of the tandem shaped charge structure was optimized, and the jet length was measured. Under the condition of charge diameter of 200 mm, when the liner thickness was 0.02CD (charge diameter) for K-charge and liner thickness was 0.25CD for the front stage warhead, the jet forming was stable and the length is the longest. After the two-stage warhead was detonated in reverse order (the initiation delay time was 220 μs), a tandem jet can be formed, and the effective jet length (excluding the pestle body) is 65 % higher than that of the later stage charge.

Numerical Study on the Relationship between the Dominant Frequency of Blasting Vibration and the Development of Plastic Zone in Cylindrical Charge

Blasting vibration is a widely studied harmful effect of rock blasting excavations. Many factors affect its dominant frequency, which makes analyzing, evaluating, and predicting it difficult. This study explored the factors influencing the dominant frequency of blasting vibrations in the case of a spherical charge. Based on symmetry, a theoretical analysis in terms of a spherical explosion source is generally sufficient to describe a cavity excited by a spherical explosion charge. The elastic cavity radius and the dominant frequency of vibration induced by the spherical blasting source are closely related. However, there is a lack of relevant research on cylindrical charges. Therefore, a calculation model for a single-hole cylindrical charge was established. There is a relationship between the corresponding dominant frequency and the range of the plastic zone. The results indicate that the dominant frequency of the blasting vibration for both cylindrical and spherical charges is closely related to the range of the plastic zone formed by the rock blasting. As the elastic cavity radius increases, both the zero-crossing and the dominant Fourier frequencies decrease, and the amplitude spectrum shifts to lower frequencies. However, increasing the cylindrical charge diameter causes more changes in the plastic zone in the direction perpendicular to the cylindrical explosive axis. Moreover, increasing the charge length causes more changes in the plastic zone along this axis. It is therefore difficult to identify a unique dimensional parameter that characterizes the range of the plastic zone formed by the blasting. Because the plastic zone around a cylindrical charge is less regular than around a spherical charge, the charge weight Q is a more favorable parameter than the elastic cavity radius a when used as the main influencing factor and in an attenuation analysis for the dominant frequency of cylindrical charge blasting.

Response behavior of double layer tungsten fragments under detonation loading

Under detonation loading, the prefabricated fragments in the warhead will be greatly deformed and even broken. In order to explore the model of deformation, the dynamic response of double-layer spherical tungsten fragments under detonation loading was studied. Firstly, a typical cylindrical warhead model was numerically simulated. The simulation model for the characteristic section only includes the quarter model for the double row fragments in the axial direction, in order to obtain the deformation response of the fragments under the detonation loading. The full-size 1/4 simulation model is designed to obtain the axial velocity distribution of the fragment. In the characteristic section, the charge diameter was used as the variable to simulate five charge sizes, and the fragment deformation law was obtained. In order to verify the correctness of the simulation, the warhead of 400 mm caliber was tested, and the flight speed of the fragment was measured. Some deformed fragments were obtained by soft recovery and their cross-section microstructure were analyzed by scanning electron microscope (SEM). The results show that the deformation of the inner layer of the double-layer spherical tungsten alloy fragment is more serious under the action of the internal explosion load, because it is squeezed by the internal explosion load and the outer layer fragment at the same time. The final dispersion velocities of the inner and outer fragments tend to be the same, and there is no significant difference in the distribution of fragments.

Numerical modeling of charge diameter effect on detonation properties of emulsion explosives using Wood-Kirkwood detonation model

ABSTRACT Emulsion explosives exhibit strong nonideal detonation behavior, which provides a challenge for accurate numerical modeling. We present a nonideal detonation model based on the Wood–Kirkwood detonation theory and EXPLO5, capable of modeling the effect of the charge diameter on steady-state detonation velocity. The elements of the model are calibrated based on experimental data for four different emulsion explosives. It was demonstrated that both simple pressure-dependent and Kirby and Chan’s two-step reaction rate models can satisfactorily reproduce the detonation velocity–charge diameter data of unconfined charges. In addition, the reaction rate parameters are found to be a function of the density of explosives.

Shock Initiation and Detonation Parameters of Hexanitrohexaazaisowurtzitane (CL‐20)

AbstractExperimental studies of the reaction zone structure in hexanitrohexaazaisowurtzitane (CL‐20) at different initial densities with a multichannel VISAR laser interferometer have been carried out. It is shown that the flow in the reaction zone corresponds to the Zeldovich‐von Neumann‐ Döring theory with a characteristic reaction time of 50 ns. The dependence of the detonation velocity on the initial density is well approximated by a similar line for HMX with a charge diameter of 20 mm. With a decrease in diameter to 4 mm, a sharp drop in the detonation parameters of CL‐20 has been recorded. The initiation of detonation under shockwave action is investigated, and the comparison of data for CL‐20 and PETN has shown that their shockwave sensitivity is quite close. The experiments on the acceleration of thin steel plates by detonating CL‐20 charges have been performed, and it is found that its accelerating ability is higher than that of HMX and retarded RDX.

Formation characteristics and penetration performance of an underwater shaped charge jet

This study aims to investigate the formation characteristics and penetration performance of an underwater conical shaped charge jet. First, a new theoretical model for underwater jet formation is proposed by the virtual mass method. Based on the theoretical model and the ALE algorithm, the influences of standoff height, cone angle, liner thickness and initiation manner on the jet formation characteristics and penetration ability are analyzed. Then the experiments of underwater shaped charge jet are carried out to verify the theoretical and simulation results. Finally some instructive conclusions are drawn: (i) the theoretical model based on the virtual mass method can accurately predict the initial jet parameters and calculate the penetration depth, and the error between the theoretical and experimental results is less than 8%. (ii) The penetration depth initially increases and then decreases with increasing standoff height. The optimal standoff height is approximately 4–4.5 times the charge diameter. (iii) at the optimal standoff height, the penetration depth decreases with the increase of the cone angle, and the optimal cone angle is 40°–50°. (iv) The penetration depth decreases with increasing the liner thickness, and the jet shape and penetration depth formed by the ring initiation manner are better.

Effect of Confinement on Detonation Velocity and Plate Dent Test Results for ANFO Explosive

The detonation properties of nonideal explosives are highly dependent on charge diameter and existence and properties of confinement. In this study, the effect of different confinements on the detonation velocity of ANFO explosives was experimentally determined along with the results of the plate dent test. ANFO explosive was selected as one of the most commonly used nonideal explosives. Following the measurement results, we found that the detonation velocity increased with increasing wall thickness, and the velocity increase was different for different confinement materials. A strong correlation existed between the ratio of the mass of confiner and explosive (M/C) and the detonation velocity (R = 0.995), and between (M/C) and the depth of the dent (δ) (R = 0.975). The data presented in this paper represent preliminary findings in developing a confinement model required for reliable numerical modeling of nonideal explosives.

Open-source modelling of aerosol dynamics and computational fluid dynamics: Bipolar and unipolar diffusion charging and photoelectric charging

Electric charging is one of the essential aerosol dynamic mechanisms and is harnessed for detection, capture and control of ultrafine aerosol particles in a range of devices. For simplicity, charging and transport mechanisms are commonly modelled with zero spatial dimensions (0-D) and averaged properties such as mean charge or mean particle diameter. These models often neglect localised effects of the flow distribution, diffusion, discrete charge states, and particle polydispersity, often proving inadequate to explain experimental data. This work aims to provide an open-source three-dimensional (3-D) aerosol charging and transport model including bipolar and unipolar diffusion charging, and photoelectric charging algorithms for use in detailed design and analyses of aerosol systems. The computational model consists of more than 200 particle transport equations for discrete charge states and polydisperse sizes coupled with ion conservation equations in the framework of OpenFOAM, an open-source computational fluid dynamics platform. Three test cases are introduced to verify implementation of three charging models by comparison with published literature: bipolar and unipolar diffusion charging, and photoelectric charging. Tutorial cases, which model three distinct aerosol sensors, are described and demonstrate the capabilities of the 3-D aerosol charging and transport models within the predetermined flow field. The aerosolChargingFoam code is available at https://openaerosol.sourceforge.io for widespread use and can be further modified under the GNU general public licence. Program summaryProgram title: aerosolChargingFoamCPC Library link to program files:https://doi.org/10.17632/4pf4n2vg9f.1Developer's repository link:https://openaerosol.sourceforge.io/Licensing provisions: GNU General Public License 3Programming language: C++Nature of problem: aerosolChargingFoam solves generalised aerosol electrical charging and transport equations coupled with computational fluid dynamics using the open-source computational platform, OpenFOAM [1]. The electric charging algorithm including unipolar diffusion charging, bipolar diffusion charging, and photoelectric charging is verified with zero-dimensional test cases [2-4] and generalized to three-dimensional monodisperse or polydisperse particle distributions for more than 50 particle charge states. aerosolChargingFoam can be straightforwardly coupled with other existing solvers, which enables computations of complex multi-physics aerosol charging processes in practical conditions.Solution method: aerosolChargingFoam employs an explicit time-stepping for the time-dependent source terms for generalised aerosol charging. The solution methods and schemes provided by OpenFOAM 9 are used for solving the spatial and time derivatives in the transport equations.

Reactive jet density distribution effect on its penetration behavior

In this paper, the penetration mechanism of reactive jet with non-uniform density distribution is studied. The simulations show that the density deficit occurs in the whole reactive jet, and the density increases from the jet tip to tail. The density of jet tip is approximately 1.5 g/cm3, which is lower than that of the reactive liner materials. The X-ray experiments show similar results with the simulations. The density decreasing effect of jet tip has a significant influence on the penetration behavior when the reactive jet impacts steel plate. According to the simulation results, this paper assumes that the density gradient in the jet section has linear distribution. Then, the deflagration pressure generated by each jet element at the bottom of crater is introduced into the Bernoulli equation. Based on the virtual origin model and Szendrei-Held equation, the analytical models for penetration depth and radial cratering of reactive jet with the density reduction are obtained. Moreover, to further prove the validity of analytical models, the penetration experiments of the reactive liner shaped charge against steel plate under different standoffs are carried out. There is a convergence between the analytical crater profiles and experimental results when reactive jets penetrate steel plates under different standoffs, especially at standoff of 1.5 and 2.0 charge diameters.

Full Silicon Tandem Solar Cells Based on Vertically Aligned Nanostructures

A three-dimensional computer simulation of flexible double-junction solar cells (SC) consisting of Si wires and p-i-n a-Si:H structures was carried out. The performance dependence on geometrical and electrical parameters was calculated. With an increase in the height of the Si wires, the open-circuit voltage ( V OC ) decreases monotonically for both the bottom Si and the top p-i-n a-Si:H junctions. The short-circuit current density ( J SC ) for the top p-i-n a-Si:H junction increases sharply with Si wire height, and then, it goes into saturation at a wire height of more than 10-15 μm. The absolute value of J SC increases (from 10.2 to 12.7 mA/cm2) with a decrease in the wire diameter (from 2 to 0.5 μm). For the bottom junction based on Si wires, the dependence of J SC on the wire height is determined by the charge carrier lifetime, doping level, and diameter, which can be associated with the effect of complete inversion of the Si wire conductivity type. For tandem SCs, the optimal wire height is 10 μm, at which efficiency of 14% can be achieved for structures based on Si wires with a diameter of 0.5 μm and a charge carrier lifetime of 10 μs. The practical implication of the developed design was experimentally demonstrated.

Calculation Model of the Axial Dispersion Distribution of Cylindrical-Warhead Fragments

The dispersion distribution characteristics of prefabricated fragments from an improvised explosive device (IED) are essential in defense technology development. To improve warhead design, it is essential to predict a fragment’s velocity and dispersion distribution accurately. This paper investigates a fragment’s flying angle from a detonated warhead with a cylindrical charge under a one-end central detonation. A modified formula for calculating the fragment dispersion distribution at each axial position of the warhead was obtained based on experimental data and model analysis. The impacts of the following parameters on the flying angle were considered in the formula: ratio of charge mass to shell mass, charge diameter, axial sparse effect, and relative axial shell position. The formula was verified by experimentation to be suitable for wide applications using different validation samples. Theoretical calculations with the formula show good accuracy in predicting the flying angle of cylindrical-shell fragments, agreeing with experimental data. The proposed model meets the error requirements of engineering applications. This work provides a theoretical foundation for subsequent research on damage effectiveness and IED damage assessment.

DETERMINATION OF DETONATION FRONT CURVATURE RADIUS OF ANFO EXPLOSIVES AND ITS IMPORTANCE IN NUMERICAL MODELLING OF DETONATION WITH THE WOOD-KIRKWOOD MODEL

Nitratebased commercial explosives, such as ANFO (ammonium nitrate/fuel oil mixture) and emulsion explosives, are characterized by a curved detonation front. The curvature is directly related to the rate of radial expansion of detonation products in the detonation driving zone and the rate of chemical reactions, and it is one of the characteristics of nonideal explosives. The detonation theories used to model the nonideal behaviour of explosives require both reaction rate and rate of radial expansion to be known/specified as input data. Unfortunately, neither can be measured and what is mostly used is a link between these rates and parameters which can be more easily measured. In this paper, the Wood-Kirkwood approach of determination of radial expansion through the radius of detonation front curvature and the electro-optical technique for experimental determination of detonation front curvature of ANFO explosives is applied. It was shown that an experimentally determined radius of detonation front curvature vs charge diameter, incorporated in the Wood-Kirkwood detonation theory, can satisfactorily reproduce experimental detonation velocity-charge diameter data for ANFO explosives, especially when the pressure-based reaction rate law is also calibrated (D=1.3 and k=0.06 1/(μs/GPaD)).

Modelling non-ideal detonations in commercial explosives

Highly non-ideal explosives usually react expressively below their ideal velocities of detonation. In these cases, dimensional effects and product heterogeneities become important to proper model their respective detonation state. Although Direct Numerical Simulation (DNS) techniques can provide a complete and exact solution for this problem, their actual computation cost are still not practical for industrial applications. In order to minimize these constrains, a simplified two-dimensional steady non-ideal detonation model for cylindrical stick explosives is presented. Based on an ellipsoidal shock shape approach (ESSA), the proposed model combines the quasione-dimensional theory for the axial flow solution with the unconfined sonic post-flow conditions at the edge of the explosive. Once calibrated, the model offers the possibility to predict the non-ideal detonation state for any charge diameter, resulting in a full mapping of the diameter-effect curve of the explosive. In addition, the effect of the inert confiner on the detonation flow is calculated by coupling a mechanistic confinement approach with the ESSA model. Thus, the proposed engineering approach is used to model the main properties of one of the most common ammonium nitrate-based explosive used in mining and quarrying industries, including the complete axial flow solution.

Blast wave characteristics of multi-layer composite charge: Theoretical analysis, numerical simulation, and experimental validation

This article investigates the characteristics of shock wave overpressure generated by multi-layer composite charge under different detonation modes. Combining dimensional analysis and the explosion mechanism of the charge, a peak overpressure prediction model for the composite charge under single-point detonation and simultaneous detonation was established. The effects of the charge structure and initiation method on the overpressure field characteristics were investigated in AUTODYN simulation. The accuracy of the prediction model and the reliability of the numerical simulation method were subsequently verified in a series of static explosion experiments. The results reveal that the mass of the inner charge was the key factor determining the peak overpressure of the composite charge under single-point detonation. The peak overpressure in the radial direction improved apparently with an increase in the aspect ratio of the charge. The overpressure curves in the axial direction exhibited a multi-peak phenomenon, and the secondary peak overpressure even exceeded the primary peak at distances of 30D and 40D (where D is the charge diameter). The difference in peak overpressure among azimuth angles of 0–90° gradually decreased with an increase in the propagation distance of the shock wave. The coupled effect of the detonation energy of the inner and outer charge under simultaneous detonation improved the overpressure in both radial and axial directions. The difference in peak overpressure obtained from model prediction and experimental measurements was less than 16.4%.

Effect of the refrigerant charge, expansion restriction, and compressor speed interactions on the energy performance of household refrigerators

This work is aimed at investigating the effects of the refrigerant charge, expansion device restriction, compressor speed, and their interactions on the performance of a household refrigerator. To this end, a micrometric valve was installed in series with the capillary tube of a frost-free refrigerator to vary the expansion restriction within a range equivalent to capillary tubes with inner diameters spanning from 0.55 to 0.85 mm. The refrigerant charge was manually changed from 35 to 65 g whereas the compressor speed was adjusted between 2500 and 4500 rpm. In total, 294 steady-state energy consumption tests were conducted, being 147 at a surrounding temperature of 32 °C, and the rest at 16 °C. It was noticed that low energy consumptions can be achieved for several combination of refrigerant charge and expansion restriction, albeit the minimal energy consumption figures were always achieved for the highest charges and restrictions. It was also verified that the refrigerator operates in a sub-optimum region so that increasing the charge from 42 g to 52 g while decreasing the capillary tube diameter from 0.64 mm to 0.60 mm led to a 3% decrease on the energy consumption. It was also found that a single combination of refrigerant charge and equivalent diameter provided satisfactory performance levels regardless of the compressor speed. Finally, a method to reduce the number of tests was proposed, in such a way that only 9 datapoints are required to generate a full energy consumption map for a given compressor speed and surrounding temperature.

Influences of the Random Stacking and Charge's Diameter on Compression and Fracture Process of Propellant Charge

AbstractAfter decades of unremitting research on the launch safety of propellant charge at home and abroad, it is gradually recognized that the fractured propellant charge generated by the compression process of propellant particles is the leading cause of chamber explosion. The large numbers of particles in propellant charge inevitably bring out the complexity in describing the fracture process under impact load in description. The discrete element method is applied to study the influences of the random stacking configurations of propellant charge and the charge diameter on the compression and fracture process of propellant charge in this paper. The results show that the random stacking of propellant bed influences little on the fracture process under the same impact load. When the diameter of propellant charge is larger than a certain value, the charge's diameter has little influence on the fracture process.

Polysulfone/Polyetherimide Ultrafiltration composite membranes constructed on a three-component Nylon-fiberglass-Nylon support for azo dyes removal: Experimental and molecular dynamics simulations

Dyeing wastewater from textile industries is often contaminated with chemical pollutants, which causes severe water pollution problems that are challenging to treat. Herein, we report the development of laminated membranes consisted of polysulfone (PSf)/polyetherimide (PEI) layers coated on Nylon-fiberglass-Nylon support by spin/spray-coating technique for the removal of reactive black 5 (RB5) and basic red 18 (BR18) from aqueous solutions via membrane Ultrafiltration (UF). In addition to a pristine polysulfone (PSf) membrane, composite membranes were prepared with 25 wt% (CM25), 30 wt% (CM30), and 35 wt% (CM35) of PEI, and characterized in terms of morphological, wetting, mechanical, and water transport properties along with surface charge and mean pore diameter. Morphological characterization by SEM showed homogeneous and uniform distribution of PSf/PEI membrane layer on the Nylon-fiberglass-Nylon support. Moreover, mechanical tests showed that the stress and strain at the breaking point of membranes were remarkably changed after coating it with Nylon-fiberglass-Nylon support. The addition of PEI had a significant influence on the hydrophilic character of prepared membranes. Filtration results indicated that the incorporation of PEI in composite membranes improved the pure water permeability (PWF) up to 79.11 L m -2 h -1 bar -1 compared to that of PSf alone (29.36 L m -2 h -1 bar -1 ). The combined effect of Nylon-fiberglass-Nylon support and the PSf/PEI membrane layer has certainly enhanced the filtration performance, making prepared UF membranes potential candidates for scale-up industrial applications.

Experimental investigation of dry powder coating processing parameters on the polystyrene particle's distribution on the surface of carbon fibers

Powder technology has been used to coat fibers with polymeric particles to manufacture composites. The material parameters such as particle size and fiber diameter and process parameters such as the particle charge and the particle velocity will influence the powder coating process. In this work, we present an experimental setup in which we characterize the coating of micron size particles on a fiber and examine the role of process parameters on the coating density. Monodispersed Polystyrene (PS) particles (2.8 ± 0.4 μm in diameter) were used to coat a carbon fiber (CF) 7 μm in diameter. A model setup was designed and fabricated in which the PS particles were charged with an ozone charging system, while the CF was maintained at the grounded state at all times. The setup consisted of two parts namely, a cyclone and a coating chamber. The distance between the PS particles was measured and the density of coating was examined using a microscope as a function of the processing parameters used in the setup. The measured average distance between the PS particles on the CF was used in our developed numerical model to estimate the friction coefficient between the charged PS particle and the grounded CF and the fiber volume fraction. The proposed methodology can be extended to any particle size, particle charge, and fiber diameter to estimate the friction coefficient and the fiber volume fraction at the microscale level.

Research on the effect of the charge diameter on the slow cook-off performance of HMX base explosive

In order to study the effect of the charge diameter on the slow cook-off (SCO) performance of HMX (cyclotetramerthylenetetranitramine) based explosives, a typical cyclotetramerthylenetetranitramine based explosive was used as the research object, and the effect of the different charge diameters on the slow cook-off performance was studied. The research results show that: the charge diameter has no significant effect on the response level of the cyclotetramerthylenetetranitramine based explosives. The reaction time and ambient temperature increase with the increase of the charge diameter, and the center temperature decreases with the increase of the charge diameter. The ambient temperature and the center temperature change regularly with the increase of the charge diameter.

The comparative study of linear shaped charges

The fireground tests are the best method for verifying the operation effectiveness of the entire shooting device or its component parts in real conditions. The purpose of the fireground tests presented herein was the physical verification of linear shaped charge (LSC) ability to perforate multi-layered target, reflecting the material and geometrical conditions of a borehole. The series of shooting tests included tests of three types of linear shaped charges selected for use in perfo-fracturing devices. The following shaped charges were tested: LSC in lead enclosure, having φ = 40 mm circular cross-section with shaped recess; LSC with copper liner in 20/30 mm steel trapezoid enclosure; LSC with liner made of solid copper, in 20/40 mm steel trapezoidal enclosure.During testing, the cumulative jet velocity was recorded using voltage type probes, arranged between the individual layers of a target composed of steel and concrete materials. The research method adapted for the project purposes was aimed at verification of the following thesis: whether the proposed shaped charges fulfil the technical and performance conditions for their effective application in the oil industry. The criterion adopted was the ability – or lack of ability – to perforate the multi-layered barrier in the form of two steel plates and concrete casting. The testing stand, single-use by its nature, was each time composed of concrete block having 400 mm ´ 250 mm ´ 150 mm dimensions and 20 MPa static compressive strength, on which two steel plates were placed parallel to each other with 20 mm spacing. The thickness of the plates was 5 mm and 10 mm respectively. The tested shaped charge was placed on the top steel plate at a distance of one calibre – that is the distance equal to the opening of the trapezoidal shaped charge and full diameter of circular cross-section charge. Furthermore, within media interface planes (steel/air, air/steel; steel/concrete), the set of voltage-type measuring probes was installed, in the form of single electric wires (φ = 0.25 mm). At an instant when they break (circuit break) as a result of cumulative jet operation, voltage drop in the subsequent measuring probes will act as a logical gate of start-stop type, or in other words the zero-one (0–1) type gate. The readings of individual probes breakage times allowed in addition to determine the velocity of the cumulative jet and to estimate its braking dynamics while passing through the subsequent elements of multi-layered target.