Lithium-ion battery thermal runaway (LIBTR) poses a serious explosion hazard in enclosed spaces such as warehouses, charging rooms, and energy storage facilities. Despite the increasing attention and regulation of explosion venting in battery storage systems, the current standards lack specific guidance for calculating venting areas in LIBTR environments. To address this issue, an experimental study was conducted in this study using an 8-liter cylindrical explosion tank equipped with five different diameters (10.5, 15, 21.2, 30 and 60 mm) and venting devices with adjustable static opening pressures. The gas released by the thermal runaway of ternary lithium-ion batteries was used as the experimental material. CO, H₂, CH₄, C₂H₄, and CO₂ were pre-mixed in actual proportions and used as a combustible mixture. At the same time, graphite dust with a D50 of 4 μm and a carbon purity of 99% was added to the hybrid explosion test to determine the effect of anode graphite dust on the explosion venting characteristics of lithium-ion batteries. High-energy ignition was used to simulate the worst-case scenario, igniting pure BVG (battery vent gas) and BVG-graphite dust mixtures under turbulent conditions. The pressure sensor monitored the real-time overpressure and recorded the maximum explosion relief pressure (p_red) as the critical output. The results showed that the p_red produced by pure BVG was always higher than that of the mixture containing graphite, indicating that graphite particles have a mitigating effect on the severity of the explosion, which may be due to heat absorption. Therefore, the influence of solid particles ejected by thermal runaway can be ignored when designing the explosion relief. p_red decays exponentially with the increase of the explosion relief diameter and grows logarithmically with the opening pressure p_stat of the explosion relief device. Based on the experimental data and combined with the specification GB50016, the calculation formula for the explosion relief area of lithium-ion battery structures was obtained, and the commonly used pressure relief ratio C is given as 0.11.

Magnesium powder, a commonly utilized metallic material, frequently gives rise to combustion and explosion incidents during its production. To identify efficient suppressants for magnesium dust explosions, six bimetallic supramolecular compounds were synthesized via co-precipitation, and their flame-suppression performance on magnesium dust flames was compared by means of flame morphology and flame-propagation velocity in a Hartmann tube; sodium bicarbonate, a traditional suppressant, served as the reference. In the tests, magnesium powder was premixed with each of the seven suppressants at a mass ratio of 1∶6 and then ignited in the Hartmann tube. The average flame-propagation velocity was derived from the tube length and the time required for the flame to reach the tube top, whereas the instantaneous flame-propagation velocity was obtained by recording flame height at successive instants. A higher average velocity and a faster flame-front propagation velocity signify a weaker suppressant efficacy. When the seven suppressants were ranked according to these two indicators, however, the orders were not fully consistent. For instance, MgAl-Cl yielded a lower average velocity than NaHCO₃, yet its maximum flame-propagation velocity exhibited the opposite trend. This discrepancy arises because certain suppressants only weakly inhibit the magnesium flame, allowing rapid flame acceleration near the tube outlet where oxygen is abundant. Integrating both the average and the maximum flame-propagation velocities, the suppressants can be arranged from the least to the most effective as follows: NaHCO₃, MgAl-Cl, ZnCr-CO₃, CaFe-Cl, MgAl-CO₃, CuAl-CO₃, CaFe-CO₃. Moreover, the percentage reductions in average velocity imparted by the four bimetallic supramolecular compounds (MgAl-Cl versus MgAl-CO₃, and CaFe-Cl versus CaFe-CO₃) were 17.95%, 27.30%, 23.82%, and 50.76%, respectively, evidencing that carbonate as the interlayer anion have a superior suppression effect on magnesium powder deflagration compared to those with chloride as the interlayer anion. Scanning electron microscopy and X-ray diffraction analyses of the reaction products, together with TG-DSC traces of the bimetallic supramolecular compounds, revealed that during the decomposition process, bimetallic supramolecular compounds lower the flame temperature via the desorption of interlayer water molecules and the heat absorption associated with the decomposition of the layered structure. Moreover, the inert gases and metal oxides generated during decomposition can block heat transfer and inhibit the volatilization of combustible gases from the surface of magnesium powder particles. Meanwhile, the metal ions and interlayer anions participate in the combustion reaction, consuming free radicals and interrupting the chain reaction, thereby achieving the explosion suppression effect.

Hydrogen energy, as a zero-carbon energy source, holds broad application prospects in critical defense systems because of its high energy density and zero carbon emissions. To enhance energy utilization efficiency and ensure operational safety, an integrated approach combining experimental and numerical simulations was adopted to systematically examine the effects of hydrogen concentration on explosion dynamics in a confined space. Experiments were carried out in a cylindrical chamber equipped with high-frequency pressure sensors and a high-speed camera to record transient overpressure and track flame propagation behavior. Complementing the experimental setup, computational fluid dynamics simulations were implemented using a detailed 19-step hydrogen/air chemical reaction mechanism to accurately reproduce the spatiotemporal evolution of flow field velocity during the premixed gas explosion process. Results indicate that the maximum explosion pressure occurred at a hydrogen volume fraction of 30%, peaking at 0.623 94 MPa. The peak flame area was largest at both 30% and 45%, exceeding results at 15% and 60% by 14.6% and 6.3%, respectively. The 30% condition also achieved the peak flame area in the shortest time, at 8.2 ms. Furthermore, geometric constraints at the junction of the cylindrical sidewall and the endwall led to accumulation of unburned hydrogen, causing localized increases in density and pressure and resulting in four clearly discernible high-velocity regions within the flow field. At 9 ms, the flow velocity profile along the centerline exhibited symmetry with a dual-peak structure appearing unilaterally. While the 45% condition showed an early transient velocity advantage due to intensified local heat release, the 30% condition demonstrated superior late-stage velocity recovery owing to more stable and sustained combustion near the stoichiometric ratio. These findings underscore the high combustion efficiency and stability achievable near stoichiometric conditions, providing a scientific foundation for the design and optimization of high-efficiency hydrogen combustion systems.

In order to study the influence of constraint conditions on the non-shock ignition reaction process of CL-20-based polymer bonded explosive (PBX) explosives, an ignition test device with adjustable mechanical constraints was used to study the reaction evolution behavior of PBX explosives under different constraints. Based on the high-speed camera image and the recovered shell wreckage, the influence of constraint conditions on the reaction rate and reaction intensity of the charge was analyzed respectively. The pressure change in the process of charge reaction was recorded by pressure sensor, and the evolution behavior of non-shock ignition reaction of explosive was analyzed. The overpressure time history of air shock wave at different positions was measured by overpressure sensor, and the detonation test of PBX was carried out. Based on the overpressure peak at the same position of the two types of tests, the relationship between constraint conditions and charge reactivity was further analyzed. The results show that weakening the mechanical constraint strength can reduce the reaction rate and the reaction intensity of the explosive. According to the pressure growth rate, the non-shock ignition reaction process under the constraint condition is divided into two stages. As the constraint strength increases, the distinction between the two reaction stages is gradually not obvious, and the first stage quickly transitions to the second stage. The parameters determined in the calculation formula of detonation overpressure peak of CL-20-based PBX explosive are A = 0.289, B = 1.041, and C = 2.224. The constraint conditions have a significant effect on the reactivity of the explosive charge. When the shell thickness is 6mm and the strength of the constraint plate is 2 MPa and 50 MPa, the reactivity of the explosive is 0.11 and 0.14, respectively. When the shell thickness is 20 mm and the strength of the constraint plate is 2 MPa, the charge reactivity is 0.31. It can be seen that the reaction intensity of CL-20-based PBX explosive can be effectively reduced by weakening the mechanical constraint strength.