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In order to study the flame retardant performance of corrugated flame arrester core on the explosion characteristics of 9.5% hydrogen/methane/air premixed gas, a self-built experimental platform was used to study the explosive characteristics and propagation rules and the impact of varying thicknesses and different volumes of hydrogen. The results indicated that the corrugated flame arrester core on the explosion flame of premixed gas was observed with two scenarios, quenching and penetration. The flame is dominated by reverse vortex flow after quenching, reversing the axial direction of flame propagation. However, the flame penetration leads to more intense burning reactions as φ increases. And the increase in thickness changes the flame structure forms a spherical flame to a mushroom-shaped flame and finally form a turbulent flame. The velocity of flame decreased significantly when L = 60 mm with φ = 10% and 20% respectively. The quenching effect is more obvious in P2 with hydrogen added, and its better performance with increasing thickness, with 9.76% and 3.70% decrease when L = 40 mm with φ = 10% and 20%, respectively, and with 57.05% and 48.55% decrease when L = 60 mm with φ = 10% and 20%, respectively. [ABSTRACT FROM AUTHOR]

A large number of gas explosion accidents have shown that secondary explosions are more dangerous and destructive than the primary. Based on the self-designed sliding experiment platform, the influence of sliding device on the evolution behavior of fuel enriched and lean flame fronts be compared. The study shown that adjusting the initial sliding position of porous media to 40 cm and using an appropriate spring coefficient can effectively extinguish methane flame in both fuel enriched and fuel lean combustion states. This method can reduce the range of flame diffusion, burning time and intensity compared with using fixed porous media, and also the maximum explosion overpressure. When using a sliding device in methane lean combustion, it can achieve significant reductions in the duration of the reverse diffusion flame (up to 64.02%), the quenching time of the flame (up to 44.21%), and the explosion overpressure inside the tube (up to 24.2%). During rich methane combustion, using sliding device can result in a reduction of up to 62.26% in the duration of the reverse diffusion flame, up to 46.81% in the quenching time of the flame, and up to 44.12% in the explosion overpressure inside the tube. Additionally, the inhibitory effect of the sliding device and the increase in elastic coefficient follow a pattern of initially increasing and then decreasing. In general, the sliding device is more effective in suppressing methane flames and overpressure during both enriched and lean fuel combustion than fixed device. The results can provide valuable insights for the development of secondary explosion prevention technology, which is crucial for preventing and managing methane explosion accidents. [ABSTRACT FROM AUTHOR]

The integration of visual data obtained from unmanned aerial vehicles (UAVs) has ushered in an era of computer vision, greatly expanding the possibilities for object tracking applications. Nevertheless, existing UAV datasets predominantly focus on large-scale objects characterized by distinct contours, overlooking single tiny objects encountered in real-world flight scenarios. Extracting appearance information from these diminutive objects poses a considerable challenge for object tracking. To rectify this imbalance in data distribution, we proposed a UAV dataset called Overhead Look Of Drones (OLOD), encompassing 70 sequences meticulously designed to address tiny object tracking. It contains over 55k frames and provides supplementary information about altitude and flight attitude. Additionally, we incorporated 11 challenging attributes to enhance the complexity of the scenes, thereby establishing a comprehensive benchmark for single object tracking. OLOD serves as a valuable tool for evaluating the tracking capabilities of various algorithms when it comes to tiny objects. Subsequently, through experimental results, we shed light on the limitations of existing methods for tracking tiny objects on this benchmark, underscoring the necessity for further research in this field. Our dataset and evaluation code will be released at . [ABSTRACT FROM AUTHOR]

The interaction between flame, shock wave and obstacle is an important content in the study of fuel combustion and safety. In this paper, the performance difference between flexible and rigid obstacles in the process of explosion flame propagation was studied. Five barriers with different blocking rates（BR） were tested in the pipeline for methane premixed explosion. The high-speed photography system collects the flame image, the flame front velocity is calculated, and the dynamic pressure changes in the upstream and downstream pipelines during flame propagation are recorded by the high-frequency pressure acquisition system. The results show that the obstacle affects the unburned flow field and generates compression waves and shear layers. The explosion promotion degree of the two obstacles presents different trends, and the peak pressure decreases. At the same time, obstacles reflect pressure waves, causing instability in the front of the flame. With the increase of plugging rate, the difference of peak pressure rises to 30% at BR = 0.4. The flame velocity of flexible obstacles is also more flat, and the peak velocity at BR = 0.2 and BR = 0.4 is close to 43 m/s. During the study, it was found that the flexible material can effectively absorb the reflected wave, and the pressure oscillation is absorbed. The average amplitude of the rigid oscillation rises from 4 kPa to 10 kPa, and the flexible oscillation decreases to nearly zero. The difference of barrier materials makes the impact of shock wave on flame and primary explosive injury (PBI) lighter, which is more conducive to assessing the explosion risk of combustible gas. [ABSTRACT FROM AUTHOR]

Many gas explosion accidents show that gas explosion can easily cause a large number of casualties and huge property losses in coal mines. Therefore, the sliding device is established to study its explosion suppression effect, and the influence of the initial position of the sliding device on the explosion is analyzed. The results show that when the sliding device is close to the ignition source, due to the strong reverse action of the spring, the sliding baffle has a reverse secondary acceleration movement, thus forming a crescent-shaped forward compression flame, forming a reverse acceleration inhibition effect and rapidly extinguishing, and this rapid reverse movement is the key technology of accelerating chain breaking and wall collision effect in methanation reaction. Generally speaking, the sliding device can effectively control the overpressure and can make the flame extinguish quickly. At the same time, the possibility of secondary fire and explosion caused by the spread of explosion in other areas is prevented. Thus, the sliding device has a good effect of explosion-proof and suppression in coal mines. [ABSTRACT FROM AUTHOR]

In order to suppress the overpressure and flame damage caused by the explosion of premixed methane-air, a self-built duct with a 10 × 10 × 100 cm was used to conduct an experimental study on the explosive characteristics and propagation rules of 9.5% methane under the effect of different porous materials at a fixed position. The methods of suppressing methane-air explosion in confined space are optimized. By analyzing the effect of porosity and distance of the porous material on the explosion, the overpressure and flame propagation characteristics after the methane-air explosion and under the influence of the dual factors are studied. It provides data support to explain the mechanism of blocking and suppressing premixed methane-air explosion when porous materials with different porosity and different positions. Studies have shown that the different porosity of porous materials and the position from the explosion source have significant and different effects on the propagation of overpressure and flame. The 10 PPI porous material has a strong promoting effect on the overpressure and flame propagation after the explosion, it accelerates the overpressure rising rate and increases the overpressure peak, and enhances the turbulence intensity of the explosion flame and accelerates the flame propagation rate. The 20 PPI porous material failed to suppress the explosion during the acceleration phase, but had certain suppression on the explosion flame in other phases. The effect of 30 PPI porous material to suppress explosion overpressure and flame depends on where it is placed. Both 20 PPI and 30 PPI porous materials can quench the flame and block the propagation of high-temperature carbonaceous products. This research results have theoretical value and guiding significance for the prevention and emergency treatment of methane explosion accidents. [ABSTRACT FROM AUTHOR]

In this paper, the influence of hydrogen volume fraction, pore size and layer number of foam copper on the explosion characteristics of hydrogen/methane premixed gas is discussed with the help of a self-built premixed gas explosion experimental platform. The volume fraction of hydrogen in the fuel is delineated as 0, 20%, 40%, 60%, and 80%. The pore diameters (Pd) of copper foam are Pd≈2.0 mm, Pd≈1.0 mm, and Pd≈0.5 mm, respectively, with three layers of foam copper for each pore diameter and a total of 45 sets of experiments are conducted. The experimental results show that the copper foam material has a significant hindering effect on the propagation of premixed hydrocarbon flame. As the hydrogen volume fraction gradually increases, the hindering effect of copper foam on the premixed flame gradually attenuates and can even promote flame development. The pore diameters of copper foam play a dominant role in the stability of flame behavior. The flame that can be halted during the propagation process is also mainly determined by the copper foam pore diameters. The number of copper foam layers does not determine the propagation state of the flame but only produces a greater degree of suppression or promotion of the flame once the propagation state has changed. [ABSTRACT FROM AUTHOR]

Many methane explosion cases show that the explosion can make serious consequences. So, a new type of sliding airtight device was established to study the explosion characteristics of methane. From the perspective of overpressure, the sliding airtight device may increase the mechanical damage of explosion to a certain extent. From the perspective of flame, the flame can be extinguished quickly in a very short distance and a very short time. The sliding airtight device can suppress the flame well, and control the explosion within a limited range without secondary fire and explosion. The sliding device has the best effect on suppressing the explosion flame of 9.5% gas within 116 ms, the second is 11.5% gas within 126 ms, and the last is 7.5% gas within 136 ms. The flame extinction time in all cases is obviously lower than that in the case of no device. It has a good effect on isolation and suppression for methane explosions. [ABSTRACT FROM AUTHOR]