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Experiments about the influence of ultrafine water mist on the methane/air explosion were carried out in a fully sealed visual vessel with methane concentrations of 8%, 9.5%, 11% and 12.5%. Water mists were generated by two nozzle...
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Experiments about the influence of ultrafine water mist on the methane/air explosion were carried out in a fully sealed visual vessel with methane concentrations of 8%, 9.5%, 11% and 12.5%. Water mists were generated by two nozzles and the droplets' Sauter Mean Diameters (SMD) were 28.2 μm and 43.3 μm respectively which were measured by Phase Doppler Particle Anemometer (PDPA). A high speed camera was used to record the flame propagation processes. The results show that the maximum explosion overpressure, pressure rising rate and flame propagation velocity of methane explosions in various concentrations increased significantly after spraying. Furthermore, the brightness of explosion flame got much higher after spraying. Besides, the mist with a larger diameter had a stronger turbulent effect and could lead to a more violent explosion reaction.
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Polymer-based sandwich composites have found increasing applications in the marine industry, where they are at an ever-increasing risk of encountering high-intensity underwater (UNDEX) or in air (AIREX) explosive loading. This rev...
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Polymer-based sandwich composites have found increasing applications in the marine industry, where they are at an ever-increasing risk of encountering high-intensity underwater (UNDEX) or in air (AIREX) explosive loading. This review presents the current state of the art in achieving adequate blast mitigation, employing polymeric composites. An attempt has been made to highlight the differences in loading mechanisms between AIREX and UNDEX and segregate the mechanisms through which polymers can mitigate these two loading modes. This understanding facilitates the development of a tailored design approach to blast mitigation. Furthermore, recent blast mitigation research related to composite sandwich architecture is discussed in detail, focusing on various components' effect on mitigation performance. Finally, additively manufactured applications, auxetics, and other foam metamaterial constructions are also presented in relation to the mitigation effort. The recent interest in such materials for use as the core in polymeric sandwich construction against blast loading is covered cohesively with the rest of the discussion.
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The dispersion of the fuel due to the center high explosive, including several different physical stages, is analyzed by means of experimental results observed with a high speed motion analysis system, and the effect of center hig...
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The dispersion of the fuel due to the center high explosive, including several different physical stages, is analyzed by means of experimental results observed with a high speed motion analysis system, and the effect of center high explosive charge is suggested. The process of the fuel dispersion process can be divided into three main stages, acceleration, deceleration and turbulence. Within a certain scope, the radius of the final fuel cloud dispersed is independent of the center explosive charge mass in an FAE (fuel air explosive) device, while only dependent both on the duration of acceleration stage and on that of the deceleration. In these two stages, the dispersion of the fuel dust mainly occurs along the radial direction. There is a close relation between the fuel dispersion process and the center explosive charge mass. To describe the motion of fuel for different stages of dispersion, different mechanical models should be applied.
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The mitigation effect of ultrafine water fog on the methane/air explosions with methane concentrations of 6%, 9%, 11% and 13% were experimentally studied in an entire closed visual vessel. The ultrafine water fog was generated in ...
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The mitigation effect of ultrafine water fog on the methane/air explosions with methane concentrations of 6%, 9%, 11% and 13% were experimentally studied in an entire closed visual vessel. The ultrafine water fog was generated in the vessel directly by ultrasonic atomization method. A high speed camera was used to record the flame propagation processes. The explosion flame evolution processes were discussed. The experimental results indicate that the maximum explosion overpressure (ΔP_(max)), the pressure rising rate ((dP/dt)_(max)) and the flame propagation velocity decreased after adding water fog. The presentation of flame cellular structures after adding water fog and the stifling effect of water vapor caused the extinguishing of the flame in the burned zone and slowed down the flame propagation. The water fog could mitigate the methane explosion of low concentration (6%) absolutely. When applied at the high concentration conditions (9%, 11% and 13%), the water fog still presented a significant suppression effect. The maximum decreasements of ΔP_(max) under the three high concentration conditions with water fog were 21.1%, 26.7% and 22.9%, respectively, while the maximum decreasements of (dP/dt)_(max) were 71.7%, 77.1% and 52.0%, respectively.
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Fundamental hexane vapour-air explosion parameters were found by measuring the explosion pressure variation in closed chambers of 5.6 and 40 dm{sup}3 volume. Also the explosion pressure and rate of explosion pressure rise of hexan...
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Fundamental hexane vapour-air explosion parameters were found by measuring the explosion pressure variation in closed chambers of 5.6 and 40 dm{sup}3 volume. Also the explosion pressure and rate of explosion pressure rise of hexane droplets-air mixtures close to upper explosion limit were obtained for chambers of 5.6, 40, 150 and 1250 dm{sup}3. It was found that the upper explosion limit for hexane droplets-air mixture is in the range of 1.8-5.5 kg/m3 and is about 30-40 times higher than the stoichiometric concentration and 3-9 times higher than that for hexane vapours-air mixtures. It was stated, that rich explosion limit is increasing along with an increase of the droplets mean diameter and also along with the chamber size. 3D and large eddy simulation of the investigated process with using computer code FLUENT 6.0 was also made.
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Explosive energy utilization for desired level of fragmentation is the key to success of any blasting operation visa-vis cost of blasting, and overall mining cost. In order to achieve this goal institutions engaged in blasting stu...
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Explosive energy utilization for desired level of fragmentation is the key to success of any blasting operation visa-vis cost of blasting, and overall mining cost. In order to achieve this goal institutions engaged in blasting studies, explosive manufacturers, and mines have adopted innovative approaches globally. Devising cost effective means to develop explosive use methodologies have been enumerated in this paper. This paper presents an innovative blasting method to reduce the explosive requirement simultaneously improving the fragmentation. Two trials were conducted in an iron ore mine where the explosive consumption could be reduced substantially. The fragmentations achieved were also observed, monitored and it can be concluded that the innovative approach had been quite different from the conventional blasting practices of the mine.
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An explosive mixture of cyclotrimethylenetrinitramine (RDX) and titanium hydride (TiH2) is introduced. To investigate the explosion characteristics of the composite explosive, charges with various contents of the TiH2 powder are p...
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An explosive mixture of cyclotrimethylenetrinitramine (RDX) and titanium hydride (TiH2) is introduced. To investigate the explosion characteristics of the composite explosive, charges with various contents of the TiH2 powder are prepared and tested in air explosion experiments. Results show that the peak overpressure, positive duration, and positive specific impulse increase as the content of TiH2 increases from 10 to 20%, as compared to passivated RDX. The peak overpressure, duration, and specific impulse have the largest increase of 6, 9, and 23%, respectively, as compared to passivated RDX, when the TiH2 content is 20%. The effect of the TiH2 particle size is also considered. The charge containing the TiH2 powder with a mean particle size of 4.6 mu m shows higher values of the three parameters than that containing 45-mu m TiH2 particles under the condition of the same content of TiH2. However, the relationship between the detonation velocity and TiH2 content is a linear inverse proportion, and the particle size of TiH2 has a minor effect on it. Solid explosion products of the TiH2/RDX composite explosive are analyzed by x-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray spectroscopy (EDX). TiO2 is found in explosion products, which is believed to form due to TiH2 oxidation.
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Methane/coal dust/air explosions under strong ignition conditions have been studied in a 199 mm inner diameter and 30.8 m long horizontal tube. A fuel gas/air manifold assembly was used to introduce methane and air into the experi...
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Methane/coal dust/air explosions under strong ignition conditions have been studied in a 199 mm inner diameter and 30.8 m long horizontal tube. A fuel gas/air manifold assembly was used to introduce methane and air into the experimental tube, and an array of 44 equally spaced dust dispersion units was used to disperse coal dust particles into the tube. The methane/coal dust/air mixture was ignited by a 7 m long epoxypropane mist cloud explosion. A deflagration-to-detonation transition (DDT) was observed, and a self-sustained detonation wave characterized by the existence of a transverse wave was propagated in the methane/coal dust/air mixtures. The suppressing effects on methane/coal dust/air mixture explosions of three solid particle suppressing agents have been studied. Coal dust and the suppressing agent were injected into the experimental tube by the dust dispersion units. The length of the suppression was 14 m. The suppression agents examined in this study comprised ABC powder, SiO_2 powder, and rock dust powder (CaCO_3). Methane/coal dust/air explosions can be efficiently suppressed by the suppression agents characterized by the rapid decrease in overpressure and propagating velocity of the explosion waves.
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Results of experimental and numerical studies on the influence of water droplets on premixed gaseous flame propagation are presented. Experimental data were obtained in the vertical standard tube of 1.2 m length and of 0.05 x 0.05...
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Results of experimental and numerical studies on the influence of water droplets on premixed gaseous flame propagation are presented. Experimental data were obtained in the vertical standard tube of 1.2 m length and of 0.05 x 0.05 m2 cross-section. The research was focused on the mechanism of a flame acceleration caused by water droplets action. For better understanding of these processes, the neutral sand particles were also used. Pictures documenting flame acceleration caused by water droplets are presented. The simulations of a flame acceleration process resulting from the presence of neutral particles were made by using FLUENT 6.0 computer code.
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