Explosion Containment Research Articles

Investigation on the flammability limits of CH4/NH3 mixtures at different CH4/NH3 ratios, oxygen concentrations and initial temperatures

The flame stability and combustion characteristics of NH3 is changed by the addition of CH4, including the flammability limits. In this paper, a 5L spherical closed explosive container was constructed to determine the flammability limits of CH4/NH3 mixtures at different CH4/NH3 ratios. The experimental results show that as the NH3 concentration increases, both the upper flammability limits and lower flammability limits of the mixture increase, and the flammable range shifts upwards. A predictive model for the flammability limits of CH4/NH3 mixtures is established based on the limiting laminar burning velocity method, and the predictive model was found to be accurate and reliable by comparing the calculated data with the experimental results. Finally, the effects of CH4 addition, oxygen concentration, and initial temperature on the flammability limits are discussed with the predictive model. The results show that the increase in oxygen concentration significantly increases the upper flammability limits of the mixture and has little effect on the lower flammability limits. An increase in initial temperature raises the upper flammability limits and decreases the lower flammability limits of the mixture, resulting in a wider flammable range.

Influence of Water Cover on the Blast Resistance of Circular Plates

Abstract Explosion containment vessels (ECVs) can effectively limit the range of potential hazards, and improving their blast resistance is an important research topic. Placing ECVs underwater is an excellent and promising method. The effect of water covering on the blast resistance of circular plates was investigated experimentally and numerically in this paper. First, blast experiments of circular water-covered and bare plates were conducted, and strain responses were obtained. The effect of water on the maximum strain as well as the high-level strain crests was investigated based on experimental results. Then, numerical simulations were carried out using ansys/autodyn and validated by experimental results. The displacement and strain response at the center of the circular plate with different water cover heights were analyzed. The experimental and numerical results show that water can effectively reduce the peak dynamic response of the steel plate and increase the vibration period of the steel plate. The center of the circular plate is the most dangerous position under confined blast loading, regardless of whether the plate is covered with water or not. The results from numerical simulations also clearly show that the blast resistance of the steel plate will first be improved and then stable with the increase of the water cover height. The work in this paper can provide a useful reference for the design and protection of explosion containment vessels.

Shock Response of Water-Protected Spherical Explosion Containment Vessels

Abstract Explosion containment vessels (ECVs) are important equipment used for underwater explosion experiment research. In this paper, a method is proposed to improve the blast resistance of the ECV by placing it in the water medium. The shock response caused by the underwater explosion in a spherical ECV is studied. The single-layer thin-walled spherical vessel shell submerged in an infinite domain water medium is deduced and simplified as a single-degree-of-freedom elastic vibration system with viscous damping. The underwater explosion shock wave is simplified to an exponential shock loading, and the analytical solutions of the radial shock vibration of the spherical shell are obtained using Duhamel's integrals. Compared with the numerical simulation results, the accuracy of the theoretical model is verified. The study results show that the water medium radiates out vibration energy and plays an important role in eliminating vibration through damping. It is found that the vibration damping ratio can be controlled by adjusting the vessel radius and thickness, so that the vibration of the shell can be controlled within three periods and the impact fatigue can be reduced. In addition, the radiation damping of the water medium greatly reduces the maximum radial displacement of the spherical shell, which significantly improves the blast resistance of the spherical shell.

Simulation and Experimental Study on the Explosion Characteristics of Aluminum Dust in the 5-L Explosion Container

ABSTRACT The CFD software was applied to conduct numerical simulation of the aluminum powder explosion and the study focused on analyzing the pattern of dust diffusion in the 5-L column explosion model containing aluminum powder at a concentration of 700 g/m 3 , and then comparing the simulated pressure change over time with experimental data. The research also examined how different levels of aluminum dust concentration affect the pressure of explosions, the rate at which explosion pressure increases, and the speed of the flame reaching the wall. The findings indicate that, during the pressure time course, the simulation process yields explosion pressure and rate of rise in explosion pressure values for a specific concentration of aluminum dust that deviate by 2% to 19% from experimental results. This suggests that the model utilized in this study possesses a certain level of reliability and it is observed that the variation patterns of explosion pressure and rate of rise in explosion pressure for aluminum dust at different concentrations differ between simulation and experimentation. In the experimentation, at concentrations of 500 g/m 3 and 900 g/m 3 , the explosion pressure and rate of rise both reached their maximum values. Furthermore, the speed of the flame reaching the wall is directly related to the level of concentration.

Anti-explosion performance and dynamic response of an innovative multi-layer composite explosion containment vessel

An innovative multi-layer composite explosion containment vessel (CECV) utilizing a sliding steel plate-aluminum honeycomb-fiber cloth sandwich is put forward to improve the anti-explosion capacity of a conventional single-layer explosion containment vessel (SECV). Firstly, a series of experiments and finite element (FE) simulations of internal explosions are implemented to understand the basic anti-explosion characteristics of a SECV and the rationality of the computational models and methods is verified by the comparison between the experimental results and simulation results. Based on this, the CECV is designed in detail and a variety of FE simulations are carried out to investigate effects of the sandwich structure, the explosive quantity and the laying mode of the fiber cloth on anti-explosion performance and dynamic response of the CECV under internal explosions. Simulation results indicate that the end cover is the critical position for both the SECV and CECV. The maximum pressure of the explosion shock wave and the maximum strain of the CECV can be extremely declined compared to those of the SECV. As a result, the explosive quantity the CECV can sustain is up to 20 times of that the SECV can sustain. Besides, as the explosive quantity increases, the internal pressure of the CECV keeps growing and the plastic deformation and failure of the sandwich structure become more and more severe, yielding plastic strain of the CECV in addition to elastic strain. The results also reveal that the laying angles of the fiber cloth's five layers have an impact on the anti-explosion performance of the CECV. For example, the CECV with fiber cloth layered in 0°/45°/90°/45°/0° mode has the optimal anti-capacity, compared to 0°/0°/0°/0°/0° and 0°/30°/60°/30°/0° modes. Overall, owing to remarkable anti-explosion capacity, this CECV can be regarded as a promising candidate for explosion resistance.

Influence of steel connector in laser-welded sandwich panels subjected to low-frequency plane shock wave

Experimental study was performed to investigate the responses of laser-welded sandwich panels subjected to a low-frequency plane shock wave inside an explosion container. The square tube and H-beam with different thicknesses were selected as connectors for the sandwich panel. The damage mechanisms of the three specimens were investigated, including the cores and face sheets. Numerical simulation was also used to discuss the influence of different peak pressure. The results show that one of the two web plates of the core cell was obviously in tension and the other one was in compression impacted by the low-frequency plane shock wave. The sandwich panel with a connector has excellent anti-blast performance in effectively reducing deformation even if the mass of the connector and the cell core is approximately equal, and the square tube was a better choice as a connector than the H-beam. The damaged area of the sandwich panel with square tube is usually in the boundary along the transverse, and the structure can withstand the critical low frequency plane shock wave much more than the initial sandwich panel.

A study of explosive-induced fracture in polymethyl methacrylate (PMMA)

The fracture response of geologic materials is of interest for applications, including geothermal energy harnessing and containment of underground explosions. To better understand the explosively induced fracture response of geomaterials, polymethyl methacrylate (PMMA) was used as a transparent rock surrogate to allow imaging of internal shock propagation and fracture growth processes. Experiments were conducted using high-speed shadowgraphy and photon Doppler velocimetry (PDV), which were compared to numerical simulations. Experiments measured fractures produced in 304.8mm×304.8mm×304.8mm PMMA cubes with two simultaneously initiated detonators. The cubes were subjected to varying amounts and directions of externally applied uniaxial stresses, including no stress, 2 MPa stress, and 20 MPa stress. The fracture radius as a function of time was extracted from the high-speed videos. Post-test images of the PMMA cubes aided in the determination of three-dimensional effects not directly imaged by the cameras. The surface velocity history and the shock response captured in PDV and the high-speed videos were compared to the simulated explosive-induced shock response. The simulation results indicate that the shock drives the fracture for the first 20 μs corresponding to a fracture radius of approximately 15 mm in the experiments. The gas-driven fracture extent was estimated analytically using an equilibrium stress distribution calculated after the shock wave propagation through the sample. Reduction in the gas pressure due to the leakage of the explosive products through the crack as a function of time was accounted for. The estimated fracture lengths were in agreement with the experimentally observed fracture lengths.

Inhibition effect of NH4H2PO4 on explosion flame propagation of aluminum alloy dust cloud

To investigate the inhibitory effect of NH4H2PO4 on the flame propagation of aluminum alloy dust clouds, experiments were conducted in cylindrical vertical ducts. High-speed cameras were employed to capture the explosion flames of aluminum alloy dust clouds under the coupled effect of NH4H2PO4 with different concentrations and particle sizes. The flame propagation behavior of NH4H2PO4/aluminum alloy dust was analyzed, and mathematical models were developed to describe the maximum distance and maximum velocity of NH4H2PO4 inhibition on the flame propagation of aluminum alloy dust clouds. Additionally, the inhibition characteristics of NH4H2PO4 on aluminum alloy dust explosions were studied in a 20 L spherical explosion container, and the thermal decomposition properties of NH4H2PO4 and aluminum alloy particles were investigated using a simultaneous thermal analyzer. Furthermore, the inhibition process of NH4H2PO4 on aluminum alloy dust was explored. The results demonstrate that the concentration of NH4H2PO4 has a greater impact on the inhibition effect on aluminum alloy dust, while the particle size has a smaller influence. Generally, as the concentration of NH4H2PO4 increases, the flame propagation distance and flame development rate decrease, leading to an enhanced inhibitory effect. The addition of NH4H2PO4 slows down the peak pressure of aluminum alloy dust explosions, resulting in a longer duration and smaller peak values of the “double-peak” pressure structure. When the particle size of NH4H2PO4 decreases and the concentration increases, the possibility of the “double-peak” structure decreases, forming a single-peak structure with lower peak values and pressure rise rates. The decomposition temperature of NH4H2PO4 precedes the combustion temperature of aluminum alloy particles. NH4H2PO4 absorbs thermal energy from the reaction system, exerting an inhibitory effect on aluminum alloy dust. The research findings provide valuable references for optimizing explosion suppression parameters and improving powder explosion suppression techniques.

Evaluation of blast mitigation performance of cylindrical explosion containment vessels based on water containers

Using liquid materials with specific geometries can enhance the explosion-proof properties of confined structures. This approach is promising because bulk water has multiple blast mitigation mechanisms and adds almost no extra mass. In this study, a method of using water-filled containers to reduce both the peak and permanent deformation of cylindrical explosion containment vessels (CECVs) is investigated through experiments and numerical simulations. Several explosion experiments were performed to evaluate the blast mitigation of the empty containers and the bulk water with multiple thicknesses and heights in terms of dynamic deformation and afterburning suppression. The experimental results indicated that the bulk water with a larger thickness and a smaller height had better protective performance, which provided up to an 80.1% reduction in permanent deformation compared with no mitigant. Numerical models were established using LS-DYNA and verified by the deformation-time history curves measured in the experiments. The energy conversion process during the explosion was analyzed through the numerical simulations, and the results showed that water absorbed most of the detonation energy that should have been transferred to the steel shell, proving that momentum extraction of water was a significant mitigation mechanism for the internal blast in CECVs. Another significant mitigation mechanism was the shadowing effect of water, which changed the spatial distribution of the blast loading acting on the steel shell, especially for water containers with larger thickness and smaller height.

Research on evolution of shock wave of ground explosion in pit type explosion containment vessel

In order to explore the evolution of shock wave in a confined space, a pit type explosion containment vessel is designed in this paper, in which the ground explosion experiments are carried out. Four gauge points are set on the container cover to collect shock wave signals. By observing the pressure history, it was found that the shock wave experiences multiple reflections in the vessel and then tends to be stable gradually. As well as each pressure crest increases abruptly and then decays rapidly. Meanwhile, the finite element analysis program ANSYS/AUTODYN is adopted to simulate the charge is detonated in the explosion containment vessel by the 2D axisymmetric algorithm. Observing the variation of the pressure field inside the container, it is found that the propagation velocity of shock wave in sand is obviously lower than that in air. And the intensity of the shock wave is obviously increased after reflection and interaction. As the shock wave propagates upward along the side wall of the vessel, the incidence angle of the shock wave also increases gradually. When the incidence angel reaches 47.73°, Mach reflection occurs. Through analyzing the distribution of pressure field near the cover, it is found that the center and the edge of the cover suffer the impact strength and bear the serious damage risk.

Evaluation of Blast Mitigation Effects of Cylindrical Explosion Containment Vessels Based on Foam

Evaluation of Blast Mitigation Effects of Cylindrical Explosion Containment Vessels Based on Foam

Improved theory of the elastic-plastic response of spherical containment vessels subjected to internal blast loading and its application

Baker built the displacement equations of motion for a thin spherical shell to spherically symmetric internal blast loading, and further provided the analytical solution of the elastic-plastic response under a triangular decaying pressure, neglecting shell thinning and radius variation [1], which was widely used in the fields of analysis and design of explosion containment vessels. However, it appears that some improvements and corrections are needed when we revisit this classic problem. In this paper, the elastic-plastic response of thin spherical shells is investigated mathematically. The complete equations of motion for three models are developed. Then the main ideas of the analytical and numerical methods are presented, as well as some important procedures and results by using Laplace transform techniques, which are convenient to use and generalize. Three typical examples are solved to exhibit differences between our improved theory and Baker’s [1]. Furthermore, our models are employed to gain some insights into response regularities, including the effect of various degrees of strain-hardening on maximum displacements under impulsive loading, and the effect of loading duration on the shell displacement for a perfectly plastic material.

Energy Performance of HMX‐Based Aluminized Explosives Containing Polytetrafluoroethylene (PTFE)

AbstractInvestigation of the energy performance of HMX‐based aluminized explosives added with polytetrafluoroethylene (PTFE) oxidizer was undertaken and compared with the PTFE‐free aluminized explosive of similar formulation. Firstly, the heat of explosion was measured in a calorimetric bomb, next the underwater explosion was conducted, then the cylinder expansion test was performed, and finally, the detonation reaction zone parameters were determined by the interface particle velocity experiment. Compared with the PTFE‐free aluminized explosive, the addition of PTFE into aluminized explosives increases the heat of explosion significantly from the calorimetric data. The PTFE‐containing aluminized explosive also yields the longer first bubble oscillation time in the underwater explosion than the PTFE‐free and ammonium perchlorate‐containing counterparts. From the cylinder test data, the wall velocity and Gurney energy were determined. The aluminized HMX containing PTFE shows an inferior acceleration ability to PTFE‐free aluminized HMX, but exhibits a stronger afterburning potential. The addition of PTFE to aluminized HMX decreases detonation velocity and CJ pressure and increases the detonation reaction zone time and length. It has reasons to believe that the PTFE partially decomposes in detonation reaction zone. Conclusions on the potential use and suggestion for future research of PTFE as an oxidizer in aluminized explosives are drawn.

Dynamic response of laser-welded corrugated sandwich panels subjected to plane blast wave

A plane blast wave with long-time effect was achieved inside an explosion container by experiment, and was applied to laser-welded corrugated sandwich panels to study the dynamic response characteristics. The deformation model of the panels was investigated, including the cores and faceplates. The results indicate that the deformation between the top and bottom face is not consistent in different directions, and the impact accelerations and deformation are not similar in relative variation with core height. Numerical simulations were applied to reproduce the experimental phenomenon. The consensus was reached that the simulation results were convincing. Based on the numerical simulation technique, a simplified analysis method using equivalence theory and three stages analysis under the plane blast wave was proposed. After comparing the calculated results, the applicable scope of the simplified method in the core height and pressure peak was also determined.

The Choice of Optical Flame Detectors for Automatic Explosion Containment Systems Based on the Results of Explosion Radiation Analysis of Methane- and Dust-Air Mixtures

A review of the existing optoelectron monitoring devices revealed that the design of optoelectron detectors of the mine atmosphere does not sufficiently take into account the factor of external optical interference. This includes any extraneous source of thermal emission: a source of artificial lighting or enterprises. As a consequence, the optoelectron detectors -based safety systems currently installed at mining sites are not able to ensure properly the detection of the ignition source in the presence of optical interference. Thus, it is necessary to determine the working spectral wavelength ranges from methane and coal dust explosions. The article presents the results of experimental research devoted to the methane-air mixture and coal dust explosion spectral analysis by means of the photoelectric method. The ignition of a methane-air mixture of stoichiometric concentration (9.5%) and coal dust of size characterized by the dispersion of 63–94 microns and concentration of 200 g/m3 was carried out in a 20 L spherical chamber with an initial temperature in the setup of 18–22 °C at atmospheric pressure. Then, photometry of the explosion light flux was conducted on a photoelectric unit. Operating spectral wavelength ranges from methane and coal dust explosions were determined. For the methane-air mixture, it is advisable to use the spectral regions at the maximum emission of 390 and 900 nm. The spectrum section at the maximum emission of 620 nm was sufficient for dust-air mixture. It enabled us to select the wavelength ranges for automatic explosion suppression systems’ launching references. This will exclude false triggering of the explosion suppression system from other radiation sources. The research results will help to improve the decision-making credibility of the device in its direct design. The results will be used in further research to design noise-resistant optical flame detection sensors with a high response rate.

Modification of the Detonation Parameters of Mining Explosives Containing Hydrogen Peroxide and Aluminium Powder

Modification of the Detonation Parameters of Mining Explosives Containing Hydrogen Peroxide and Aluminium Powder

Dynamic instability of fiber composite cylindrical shell with metal liner subjected to internal pulse loading

Thin-walled cylindrical shells are commonly used structures in explosion containment vessels. When subjected to internal blast loading, these cylindrical shells are prone to dynamic buckling failure.In this work the dynamic stability of cylindrical fiber composite shells with metal liner subjected to uniform internal pressure pulse was investigated through both finite element simulations and theoretical modelling. In particular, pulse buckling of the inner metal liner and vibrational buckling of the outer fiber composite shell were observed and studied. Dynamic, Implicit analysis in ABAQUS Standard considering the initial geometric imperfections were conducted to study the mechanisms for the dynamic buckling of the inner metal liner and outer fiber composite shell. The simulated buckled shape using a simplified two-dimensional model could successfully reproduce the previous experimental results. The dynamic pulse buckling of the metal liner was found to occur during the plastic compression process. The effect of the buckling amplitude of the inner metal liner on the dynamic stability of the outer fiber composite shell was also revealed using numerical simulations. Instead of preventing the outer fiber composite shell from buckling instability, severely buckled metal liner with large buckling amplitude may even accelerate the growth of unstable mode of the fiber composite shell. The theoretical solution for the radial deformation of the metal liner was established by modelling the growth of the buckling mode as the amplification of the initial geometric or velocity imperfection. The most amplified mode and corresponding amplification were determined by the derived amplification function. The solutions for the radial deformation of the outer fiber composite shell were represented by a set of Mathieu differential equations. The dynamic instability of the fiber composite shells was determined from the Mathieu stability charts. The dependence of the dynamic instability of the bilayer composite shells on various parameters such as composite layup, thickness-to-radius ratio and impulse of pressure pulse loading was theoretically predicted and compared with the finite element simulation results.

Study on transient reaction mechanism and explosion intensity parameters of micron-sized flake aluminum dust in air

Micron-sized flake aluminum dust has great potential in rocket propellants and advanced thermobaric weapons because of its large specific surface area. A 20 L near-spherical explosion system and a 2D simulation model are established to study the explosion intensity parameters and transient reaction details of flake aluminum dust/air two-phase explosion. The transient reaction rate of flake aluminum dust/air is mainly determined by the oxygen diffusion rate and chemical kinetic rate. Nano-sized Al2O3 products have two distribution states: some particles are dissociated in the explosion container and gradually collide and agglomerate to form a pure product block; others adhere to the surface of flake aluminum dust, which hinders the further contact between aluminum dust and air. The maximum explosion overpressure (9.16 bar) occurs when the aluminum dust concentration is about 400 g/m3, and the maximum pressure rise rate of flake aluminum dust explosion can reach 1560 bar/s. A colorimetric thermometer is used to record the flame temperature of the gas/dust two-phase explosion and the highest flame temperature is about 3500 K. This work will provide reference for explosion protection and efficient utilization of flake aluminum dust.

Research on the Vibration Response of Cylindrical Vessel under Explosion Shock Wave in Confined Space

The experimental research is carried out on the shock wave vibration response of the cylindrical explosive container under the explosion at the center point. First, a horizontal flat-head cylindrical explosion vessel was designed and the shock wave vibration test placement was carried out; secondly, the explosion shock wave vibration test in a confined space was carried out under different charges; then the vibration conditions at several typical locations were carried out Comparative measurement and analysis of its vibration frequency characteristics. The test results show that the shell vibration acceleration value at the measuring point is related to the charge amount and the distance from the explosion center; the shell vibration frequency close to the middle ring is dominated by the natural fundamental frequency, and as the shell moves away from the center to the ends, The low-frequency vibration gradually increases, and the vibration frequency component of the container head is single, and its main frequency is determined by the natural frequency of the head.

Detonation of an Explosive Containing Nano-Sized Inclusions

Detonation of an Explosive Containing Nano-Sized Inclusions