Explosion Velocity Research Articles

Deriving High-Energy-Density Polymeric Nitrogen N10 from the Host–Guest ArN10 Compound

Discovering stable polymeric nitrogen phases and exploring their properties are crucial for energy storage and conversion, garnering significant attention. In this study, we investigate the formation possibility of a stable compound between Ar and N2 through ab initio calculations under low-pressure conditions (0–100 GPa). The novel super nitride, Imm2 ArN10, is designed to demonstrate robust thermodynamic stability under high pressures (91 GPa) and showcase the unique host–guest structure, in which guest atoms (Ar) are trapped inside the host polymeric N10. Significantly, given the weak interaction between Ar and N atoms and a channel parallel to the c-crystallographic axis in ArN10, we propose a novel method to stabilize the previously unknown polymeric nitrogen structure, Imm2-N10, by removing the guest argon atoms from the natural channels of ArN10. Imm2 ArN10 and N10 are thermodynamically and dynamically stable, with energy densities of 9.1 kJ g−1 and 12.3 kJ g−1, respectively—more than twice that of TNT. Additionally, ArN10 and N10 stand out as leading green energetic materials, boasting a superior explosion velocity of 17.56 km s−1 and a detonation pressure of 1712 kbar, surpassing that of TNT. These findings significantly impact on the creation of pure nitrogen frameworks through chemical reactions involving inert elements under high pressure.

Shock cooling emission from explosions of red supergiants: II. An analytic model of deviations from blackbody emission

ABSTRACT Light emission in the first hours and days following core-collapse supernovae (SNe) is dominated by the escape of photons from the expanding shock-heated envelope. In a preceding paper, Paper I, we provided a simple analytic description of the time-dependent luminosity, L, and colour temperature, Tcol, valid up to H recombination (T ≈ 0.7 eV), for explosions of red supergiants with convective polytropic envelopes without significant circumstellar medium (CSM). The analytic description was calibrated against ‘grey’ (frequency-independent) photon diffusion numeric calculations. Here, we present the results of a large set of 1D multigroup (frequency-dependent) calculations, for a wide range of progenitor parameters (mass, radius, core/envelope mass ratios, metalicity) and explosion energies, using opacity tables that we constructed (and made publicly available), including the contributions of bound–bound and bound–free transitions. We provide an analytic description of the small, ${\simeq}10\ \hbox{per cent}$ deviations of the spectrum from blackbody at low frequencies, hν < 3Tcol, and an improved (over Paper I) description of ‘line dampening’ for hν > 3Tcol. We show that the effects of deviations from initial polytropic density distribution are small, and so are the effects of ‘expansion opacity’ and deviations from LTE ionization and excitation (within our model assumptions). A recent study of a large set of type II SN observations finds that our model accounts well for the early multiband data of more than 50 per cent of observed SNe (the others are likely affected by thick CSM), enabling the inference of progenitor properties, explosion velocity, and relative extinction.

Study on the effect of venting conditions on methane-air explosion characteristics in full-scale mine tunnel

The overpressure and heat products generated by methane explosions seriously threaten human life. Therefore, studying the influence mechanism of venting conditions on methane explosion characteristics in full-scale tunnels is of great significance for preventing and controlling methane explosions in mines. This study takes the Lynn Lake experimental mine (LLEM#501) as a background case, and studies the changes in methane explosion characteristics under different sealing ratios in full-scale tunnel using the GASFLOW-MPI code. The study shows that the greater the sealing ratio, the larger the maximum overpressure, maximum fluid velocity, and reflection wave overpressure in the methane explosion area. As the sealing ratio increases, the coupling effect of gas expansion and reflected shock wave overpressure causes a decrease in both the negative pressure value and the negative pressure area in the explosion zone. When the area is completely sealed, there is no formation of negative pressure. High-temperature heat products and flame backflow by cavity structures is the main factor that causes local temperature anomalies to increase and oscillations. Heat loss is a crucial factor influencing methane explosions, with approximately 22.75 % to 25.77 % of the explosion energy being dissipated in the form of heat during the explosion process. As the sealing ratio increases, the heat loss during the explosion process shows an exponential decrease trend. By analyzing the methane explosion energy equation, it has been determined that the decrease in heat loss during the methane explosion process is the primary cause for the increase in methane explosion overpressure and velocity.

Experimental study on the effect of titanium hydride content on the detonation performance of emulsion explosives

AbstractIn order to improve the explosion characteristics of emulsion explosives, titanium hydride was added to emulsion explosives to produce a new type of hydrogen storage emulsion explosives. Charges with different contents of titanium hydride were evaluated through underwater explosion experiments and detonation velocity tests. The tests on underwater explosion and detonation velocity reveal that compared to pure emulsion explosives, the detonation parameters of emulsion explosives containing titanium hydride showed a trend of first increasing and then decreasing. When the mass ratio of titanium hydride in the emulsion explosive is 1 % to 3 %, all detonation parameters have been improved to a certain extent. When the mass ratio of titanium hydride in the emulsion explosive is 3 % to 10 %, only part of the detonation parameters (specific impulse, specific shock energy, specific total energy and volume energy density) has been improved. The maximum increase of specific impulse, specific shock energy, specific total energy and volume energy density of emulsion explosive containing titanium hydride is 7.06 %, 8.95 %, 3.97 % and 8.22 %, respectively. Based on the analysis, it is evident that though powdered TiH2 participates in the detonation reaction process of the emulsion explosive, the majority of TiH2′s energy is released during the secondary reaction occurring after the detonation wave front. Therefore, the detonation performance of emulsion explosives can be effectively improved by adding a certain mass ratio of titanium hydride.

Shock cooling emission from explosions of red supergiants – I. A numerically calibrated analytic model

ABSTRACT Supernova light curves are dominated at early time, hours to days, by photons escaping from the expanding shock heated envelope. We provide a simple analytic description of the time-dependent luminosity, L, and colour temperature, Tcol, for explosions of red supergiants (with convective polytropic envelopes), valid up to H recombination (T ≈ 0.7 eV). The analytic description interpolates between existing expressions valid at different (planar then spherical) stages of the expansion, and is calibrated against numerical hydrodynamic diffusion calculations for a wide range of progenitor parameters (mass, radius, core/envelope mass and radius ratios, and metalicity), and explosion energies. The numerically derived L and Tcol are described by the analytic expressions with $10{{\ \rm per\ cent}}$ and $5{{\ \rm per\ cent}}$ accuracy, respectively. Tcol is inferred from the hydrodynamic profiles using frequency independent opacity, based on tables we constructed for this purpose (and will be made publicly available) including bound–bound and bound–free contributions. In an accompanying paper (Paper II) we show − using a large set of multigroup photon diffusion calculations − that the spectral energy distribution is well described by a Planck spectrum with T = Tcol, except at ultraviolet (UV) frequencies, where the flux can be significantly suppressed due to strong line absorption. We defer the full discussion of the multigroup results to paper II, but provide here for completeness an analytic description also of the UV suppression. Our analytic results are a useful tool for inferring progenitor properties, explosion velocity, and also relative extinction based on early multiband shock cooling observations of supernovae.

On methodology and application of smoothed particle hydrodynamics in fluid, solid and biomechanics.

Smoothed particle hydrodynamics (SPH), as one of the earliest meshfree methods, has broad prospects in modeling a wide range of problems in engineering and science, including extremely large deformation problems such as explosion and high velocity impact. This paper aims to provide a comprehensive overview on the recent advances of SPH method in the fields of fluid, solid, and biomechanics. First, the theory of SPH is described, and improved algorithms of SPH with high accuracy are summarized, such as the finite particle method (FPM). Techniques used in SPH method for simulating fluid, solid and biomechanics problems are discussed. The δ-SPH method and Godunov SPH (GSPH) based on the Riemann model are described for handling instability issues in fluid dynamics. Next, the interface contact algorithm for fluid-structure interaction is also discussed. The common algorithms for improving the tensile instability and the framework of total Lagrangian SPH are examined for challenging tasks in solid mechanics. In terms of biomechanics, the governing equations and the coupling forces based on SPH method are exemplified. Then, various typical engineering applications and recent advances are elaborated. The application of fluid mainly depicts the interaction between fluid and rigid body as well as elastomer, while some complicated fluid-structure interaction ocean engineering problems are also presented. In the aspect of solid dynamics, galaxy, geotechnical mechanics, explosion and impact, and additive manufacturing are summarized. Furthermore, the recent advancements of SPH method in biomechanics, such as hemodynamically and gut health, are discussed in general. In addition, to overcome the limitations of computational efficiency and computational scale, the multiscale adaptive resolution, the parallel algorithm and the automated mesh generation are addressed. The development of SPH software in China and abroad is also summarized. Finally, the challenging task of SPH method in the future is summarized. In future research work, the establishment of multi-scale coupled SPH model and deep learning technology in solid and biodynamics will be the focus of expanding the engineering applications of SPH methods.

Experimental study on the radial vibration characteristics of a coal briquette in each stage of its life cycle under the action of CO2 gas explosion

CO2 gas explosion is an important technology for coal seam permeability enhancement and fracturing, but the stage division of its life cycle is unclear, and research on the use of radial vibration characteristic parameters for stage division is lacking. To more accurately divide each stage of the life cycle and analyse the characteristics of each stage, a radial vibration mechanical model of CO2 gas explosion was constructed. A novel radial vibration laboratory test of a briquette under CO2 gas explosion was designed and conducted, and the characteristic parameters, such as the explosion radial vibration signal waveform, peak acceleration, velocity, and peak energy, were quantitatively analysed. The results show that there were three stages in the life cycle of a coal briquette under the action of a CO2 gas explosion. The first stage, from 0 to 1.507 ms, was the stress wave action stage, in which the peak acceleration and peak energy around the blasthole were 25.460 g and 9.480 × 1012 (m/s)2, respectively. The second stage, from 1.507 ms to 9.282 ms, was the CO2 gas explosion energy storage stage, in which the peak acceleration and peak energy around the blasthole were 1.478 g and 5.524 × 107 (m/s)2, respectively. The third stage, from 9.282 ms to 12.606 ms, was the CO2 splitting stage, in which the peak acceleration and peak energy around the blasthole were 6.527 g and 1.470 × 109 (m/s)2, respectively. The research results analysed after the CO2 gas explosion verify the promotion of gas splitting in the second and third stages, explain the evolution mechanism of radial vibration in each stage of CO2 explosion, and provide a theoretical basis for the optimal design of CO2 explosion technology.

Chemical study of fused ring tetrazine derivatives as possible high energy density materials (HEDMs).

Using density functional theory (DFT), enthalpy of formation (HOF), thermodynamic properties, and detonation properties of a series of tetrazine fused ring derivatives are calculated. The results show that the introduction of coordinated oxygen is beneficial to increase the HOF value. The effects of different substituents on HOF are as follows: -C(NO2)3 > -N3 > -CH(NO2)2 > -NHNO2 > -NO2 > -NHNH2 > -H > -OH. Introduction of -H, -NH2, and -NHNH2 on the parent is not conducive to improving the detonation performance, while the introduction of -C(NO2)3 is conducive to improving the detonation performance of the designed compound. The explosion velocity of the newly designed compounds varies between 8.96 and 10.48km·s-1. The explosion pressure varies between 35.97 and 51.80 GPa, and the density varies between 1.83 and 2.00g·cm-3. Considering the thermal stability, density, and detonation properties, most of these compounds designed this time can be used as potential candidates for high energy density compounds.

Role of wire diameter size in the high voltage pulse wire explosion: Insights from molecular dynamics simulations

We performed molecular dynamics simulations of the high voltage pulse explosion of single aluminum wires with the energy ratio of 0.6 in vacuum and studied the role of wire radial dimension. Simulation results show that large-diameter wires having a large material depth and a small specific surface can maintain a higher deposition energy density and effectively reduce the influence of the radial difference in thermodynamic parameters, leading to higher explosion velocity and a lower vaporization rate in the large-diameter wire. The most significant effect is that the larger diameter wire has a longer explosion development time. In addition, the propagation and reflection of the rarefaction waves in the wire result in two explosion regimes: the spinodal decomposition propagating inward from the surface and the cavitation boiling from the center to the surface. Increasing the diameter will increase the domination range of the spinodal decomposition mechanism.

Effect of Al2O3 particle size reduction on aluminium dust explosion

To investigate the effect of Al2O3 particle size on an aluminum explosion, the overpressure and flame velocity in a vertical duct were evaluated. The results show that the inhibitory effect of submicron Al2O3 is best, while the inhibitory effect increases with increasing inerting ratio. However, the inhibitory effect of micron Al2O3 does not increase significantly after the inerting ratio exceeds 40%. For high-concentration aluminum powder, 0.8 μm Al2O3 with an inerting ratio less than 20% promotes aluminum explosion. As the inerting ratio increases beyond 20%, however, the overpressure decreases. Furthermore, Al2O3 inhibits the formation of the intermediate product AlO and decreases the flame brightness. As the inerting ratio of 0.8 μm Al2O3 reaches 50%, the white patches in the flame image disappear. The results of scanning electron microscopy showed that the explosion products agglomerate and some dot-like protrusions appear on the surface of the unburned aluminum particles. The inhibition mechanism was qualitatively investigated. Physical heat absorption is proven to play a limited role. Thermal radiation and chemical inhibition play a key role. The chemical effect mainly influences the surface reaction energy source.

Performances and direct writing of CL-20 based ultraviolet curing explosive ink

A new type of explosive ink formulation that can be quickly cured was prepared with unsaturated polyester as binder, styrene as active monomer, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide as photoinitiator, and hexanitrohexaazaisowurtzitane (CL-20) as the main explosive. Then the explosive ink direct writing technology was used to charge the micro-sized energetic devices, the curing mechanism of the explosive ink was discussed, and the microstructure, safety performance and explosive transfer performance of the explosive ink molded samples were tested and analyzed. Results indicate that the composite material has a fast curing molding speed, its hardness can reach 2H within 8 min. The crystal form of CL-20 in the molded sample is still ε type. The CL-20 based UV-curing explosive ink formulation has good compatibility, its apparent activation energy is increased by about 3.5 kJ/mol. The composite presents a significant reduction in impact sensitivity and its characteristic drop height can reach 39.8 cm, which is about 3 times higher than the raw material. When the line width of charge is 1.0 mm, the critical thickness of the explosion can reach 0.015 mm, and the explosion velocity is 7129 m/s when the charge density is 1.612 g/cm3.

Dynamic and whipping response of the surface ship subjected to underwater explosion: experiment and simulation

ABSTRACT The dynamic and the whipping phenomena through an underwater explosion (UNDEX) experiments and simulations were verified. Furthermore, the comparison of the simulation and experimental results were conducted. The experiment was conducted at a reservoir and the MegaMEX was used as an explosive. The simulation was performed by combining the DAA-based USA code with the LS-Dyna which is a finite element analysis code, and for the gas bubble, the second-generation Geers–Hunter model was used. For the experiment, the natural frequency analysis of the structure was carried out to establish the explosion condition and four underwater explosion tests were carried out. Acceleration, velocity, strain and underwater pressures were measured by underwater explosion experiments, and acceleration, velocity and strain were compared. In this research, the whipping phenomenon by underwater explosion was confirmed through experiments and simulation. The results of this study are expected to contribute to the improvement of UNDEX simulation technique.

Explosion energy of methane/deposited coal dust and inert effects of rock dust

In order to study the processes of lifting, dispersing and igniting of a dust layer behind the local gas explosion as well as their suppression, premixed methane local explosion igniting deposited coal/inert rock dust at the bottom of a tube are simulated. The two-phase combustion mechanism is obtained that the deposited dust is kicked up by the leading pressure wave, developing an uneven dust cloud filling in the tube, and then the gas flame ignites the dust cloud to form the composite flame. The rock dust lain on the tunnel ground has a significant suppression effect on the explosion overpressure, flame temperature and velocity of methane with coal dust. When the rock dust proportion in coal dust is 90%, the peak values of overpressure, flame temperature and flame velocity of the hybrid coal dust/rock dust/methane explosion are 0.6, 0.78 and 0.55 times of those of coal dust/methane explosion, respectively. The rock dust with the particles of smaller size has a remarkable suppression effect on explosion flame. When the rock dust proportion in the coal dust is 70%, the peak explosion overpressure and the flame velocity under suppression of the 12 µm rock dust are 10% and 11% lower than those of the 31 µm rock dust, respectively.

Explosion symmetry improvement of polyimide-coated tungsten wire in vacuum on negative discharge facility

Tungsten wire explosion is very asymmetric when fast current rate and insulated coatings are both applied on negative discharge facility using a 24-mm-diameter cathode geometry, which is commonly used on mega-ampere facilities. It is inferred, based on an analytical treatment of the guiding center drift and COMSOL simulations, that the large negative radial electric field causes early voltage breakdown and terminates energy deposition into the wire core on the anode side of the wire. After the anode side is short circuited, the radial electric field along the wire surface on the cathode side will change its polarity and thus leading to additional energy deposition into the wire core. This change causes ∼10 times larger energy deposition and ∼14 times faster explosion velocity in the cathode side than the anode side. In order to reduce this asymmetry, a hollow cylindrical cathode geometry was used to reverse the polarity of radial electric field and was optimized to use on multi-MA facilities. In this case, fully vaporized polyimide-coated tungsten wire with great symmetry improvement was achieved with energy deposition of ∼8.8 eV/atom. The atomic and electronic density distributions for the two different load geometries were obtained by the double-wavelength measurement.

Exploring the Efficacy and Limitations of Shock-cooling Models: New Analysis of Type II Supernovae Observed by the Kepler Mission

Abstract Modern transient surveys have begun discovering and following supernovae (SNe) shortly after first light—providing systematic measurements of the rise of Type II SNe. We explore how analytic models of early shock-cooling emission from core-collapse SNe can constrain the progenitor’s radius, explosion velocity, and local host extinction. We simulate synthetic photometry in several realistic observing scenarios; assuming the models describe the typical explosions well, we find that ultraviolet observations can constrain the progenitor’s radius to a statistical uncertainty of ±10%–15%, with a systematic uncertainty of ±20%. With these observations the local host extinction (A V ) can be constrained to a factor of two and the shock velocity to ±5% with a systematic uncertainty of ±10%. We also reanalyze the SN light curves presented by Garnavich et al. (2016) and find that KSN 2011a can be fit by a blue supergiant model with a progenitor radius of , while KSN 2011d can be fit with a red supergiant model with a progenitor radius of . Our results do not agree with those of Garnavich et al. Moreover, we re-evaluate their claims and find that there is no statistically significant evidence for a shock-breakout flare in the light curve of KSN 2011d.

Nghiên cứu ảnh hưởng của bột nhôm đến một số tính chất của thuốc nổ nhũ tương

The article studies the effect of aluminum powder (with different content and particle size) on some significant properties of emulsion explosive such as density, water resistance, detonation velocity and heat of explosion. The calculated data and experimental results show that the density, heat of explosion and detonation velocity of the emulsion explosive with aluminum powder as an energy additive which is less than 10% of the content are higher than those without aluminum powder, while its water resistance decreases. It is proved that aluminum powder can be completely used to impove the detonation energy of emulsion explosive with paying attention to its low water resistance when conduct underwater blasting.

Landing point location algorithm based on asynchronous time difference of arrival (ATDOA) method

This paper analyzes the acoustic and micro seism signal feature of the projectile launching, flight and landing explosion in range test, and puts forward a Landing Point Location method which based on the asynchronous time difference of arrival (ATDOA) method. This method can effectively filter away the signals in launching and flight process, meanwhile get the acoustic and micro seism signal of projectile explosion accurately, and then the explosion location and velocity can be obtained by iterative equations. Comparing with the existing projectile point positioning method, this method can find the arrival time of explosion signal accurately, and establish the composition equations by iterative calculation equation of the respective location without precise synchronization of each sensor. Accordingly, the complexity of the application system is reduced, and positioning precision is improved effectively.

Probing off-Hugoniot states in Ta, Cu, and Al to 1000 GPa compression with magnetically driven liner implosions

We report on a new technique for obtaining off-Hugoniot pressure vs. density data for solid metals compressed to extreme pressure by a magnetically driven liner implosion on the Z-machine (Z) at Sandia National Laboratories. In our experiments, the liner comprises inner and outer metal tubes. The inner tube is composed of a sample material (e.g., Ta and Cu) whose compressed state is to be inferred. The outer tube is composed of Al and serves as the current carrying cathode. Another aluminum liner at much larger radius serves as the anode. A shaped current pulse quasi-isentropically compresses the sample as it implodes. The iterative method used to infer pressure vs. density requires two velocity measurements. Photonic Doppler velocimetry probes measure the implosion velocity of the free (inner) surface of the sample material and the explosion velocity of the anode free (outer) surface. These two velocities are used in conjunction with magnetohydrodynamic simulation and mathematical optimization to obtain the current driving the liner implosion, and to infer pressure and density in the sample through maximum compression. This new equation of state calibration technique is illustrated using a simulated experiment with a Cu sample. Monte Carlo uncertainty quantification of synthetic data establishes convergence criteria for experiments. Results are presented from experiments with Al/Ta, Al/Cu, and Al liners. Symmetric liner implosion with quasi-isentropic compression to peak pressure ∼1000 GPa is achieved in all cases. These experiments exhibit unexpectedly softer behavior above 200 GPa, which we conjecture is related to differences in the actual and modeled properties of aluminum.

Strombolian surface activity regimes at Yasur volcano, Vanuatu, as observed by Doppler radar, infrared camera and infrasound

In late 2008 we recorded a continuous multi-parameter data set including Doppler radar, infrared and infrasound data at Yasur volcano, Vanuatu. Our recordings cover a transition in explosive style from ash-rich to ash-free explosions followed again by a phase of high ash discharge. To assess the present paradigm of Strombolian behavior in this study we investigate the geophysical signature of these different explosive episodes and compare our results to observations at Stromboli volcano, Italy. To this end we characterize Yasur's surface activity in terms of material movement, temperature and excess pressure. The joint temporal trend in these data reveals smooth variations of surface activity and regime-like persistence of individual explosion forms over days. Analysis of all data types shows ash-free and ash-rich explosive styles similar to those found at Stromboli volcano. During ash-free activity low echo powers, high explosion velocities and high temperatures result from the movement of isolated hot ballistic clasts. In contrast, ash-rich episodes exhibit high echo powers, low explosion velocities and low temperatures linked to the presence of colder ash-rich plumes. Furthermore ash-free explosions cause high excess pressure signals exhibiting high frequencies opposed to low-amplitude, low-frequency signals accompanying ash-rich activity. To corroborate these findings we compare fifteen representative explosions of each explosive episode. Explosion onset velocities derived from Doppler radar and infrared camera data are in excellent agreement and consistent with overall observations in each regime. Examination of infrasound recordings likewise confirms our observations, although a weak coupling between explosion velocity and excess pressure indicates changes in wave propagation. The overall trend in explosion velocity and excess pressure however demonstrates a general correlation between explosive style and explosion intensity, and points to stability of the uppermost conduit on timescales shorter than at Stromboli volcano.

Response of Fiber Reinforced Composite Structures to Ballistic Loads

Explosion and high velocity impact are typical ballistic loads of structures. This paper describes the problem of wave propagation in solid rocket booster part. Such waves originate by acting of explosion waves or by high velocity impact of solid parts on the structure. Computational simulations are applied to the problem of propagation of shock waves in a composite material reinforced by carbon fibres which are supposed to be much stiffer than the matrix. The shock wave in such material is influenced by reflexion and refraction on the interface between fibres and the matrix and by the interaction of then waves. The shock wave is strongly damped in such composites in this way. In the present study, the response of composite laminates under velocity impact loading will be investigated using MATLAB and ABAQUS software.