Search Results (130)

To investigate the explosive characteristics of solid–liquid mixed fuels containing different types of metal powders—including hydrogen-storage metal powders—and volatile liquid fuels, explosion experiments and corresponding numerical simulations were conducted under unconstrained space conditions. The studied system consisted of Et₂O/Al/B/MgH₂ mixed fuels with varying composition ratios. Research has shown that the dispersion effect of solid–liquid mixed fuel containing metal dust under strong shock waves is higher than that of pure liquid fuel. And the explosion overpressure and temperature of solid–liquid mixed fuel are higher than that of pure liquid fuel. Under the same solid–liquid ratio, the explosive overpressure of Et₂O/Al/B/MgH₂ mixed fuel was the highest, which was 110.8% higher than that of pure liquid fuel at the 5 m position. For solid–liquid mixed fuels containing different metal powders, due to the high reaction threshold of boron powder, a high-activity MgH₂ reaction is required to drive the reaction. Therefore, the explosive strength of the mixed fuel systems follows the order Et₂O/Al/B/MgH₂ > Et₂O/Al/MgH₂ > Et₂O/Al > Et₂O/Al/B. Meanwhile, simulation models for pure liquid and solid–liquid fuel explosions were established. The discrepancy between the simulated results and the experimental data was within 10%, demonstrating that the proposed model provides an effective and reliable approach for predicting the explosive power and hazardous range of fuel–air explosions. Full article

This study investigates particle size distribution and fine dust generation from sanding six tropical wood species (Red Meranti, Iroko, Zebrano, Bubinga, Ipe, and Wenge) using sieve analysis and laser diffraction. The wood species produced different dust particles, primarily influenced by wood density. Bubinga, Zebrano, and Wenge generated the highest proportion of particles in the 125–250 μm range, while Ipe and Iroko produced more dust in the 63–125 μm fraction. Low-density Red Meranti formed the greatest share of coarse particles (10.54% over 549.5 μm), whereas high-density Ipe generated the largest proportion of respirable dust, including PM₁₀ (8.80%), PM_2.5 (2.93%), and PM₁ (0.88%). Statistical analysis confirmed a significant effect of density on both coarse and fine dust fractions, with finer particles increasing consistently as density increased. Laser diffraction showed ultrafine particles down to approximately 0.7 μm in all species except Red Meranti. Microscopy confirmed elongated fibrous fragments, particularly in Wenge and Red Meranti. Overall, denser tropical hardwoods exhibited greater potential to produce hazardous fine dust during sanding, posing health risks and explosion hazards. These findings emphasize the need for effective dust extraction and high-efficiency respiratory protection and contribute to improved understanding of dust formation mechanisms in tropical wood processing. Full article

This study investigated spruce wood (Picea abies Karst. L.) dust generated during sanding in a woodworking company, focusing on its health, explosion, and fire hazards. Microscopic analyses revealed that dust particles ranged from 2.38 μm × 1.69 μm to 499.71 μm × 403.30 μm, with an average size of 73.2 μm × 37.98 μm. Smaller particles exhibited a spherical morphology, while larger ones were elongated and fibrous. Sieve analysis confirmed that particles sized 63–75 μm formed the largest fraction (46.74%), with 71% of the total dust being airborne (<100 μm), including 5% PM₁₀ and 1% PM_2.5. Explosion tests identified a lower explosion limit (LEL) of 80 g·m⁻³, with dust classified as highly explosive (ST 2). Smaller particles were found to significantly reduce the LEL, increasing explosion susceptibility. These findings highlight the dual risk of inhalation exposure and explosion potential. Practical safety recommendations include ensuring efficient local dust extraction, mandatory use of respiratory protection, and restricted worker movement near sanders. Furthermore, organizational measures aligned with ATEX standards—such as daily cleaning, removal of settled dust layers, use of explosion-safe industrial vacuum cleaners, and installation of automatic explosion suppression systems in extraction units—are essential. Full article

Maximum power point tracking (MPPT) control is a key technology for increasing the power generation of photovoltaic arrays under varying light and temperature conditions. Traditional perturb and observe methods and incremental conductance methods can achieve good tracking performance for single-peak characteristics. However, under complex conditions such as partial shading or dust accumulation, the power-voltage curve of a photovoltaic array exhibits multi-peak characteristics. In such cases, traditional methods may get trapped in local optima, preventing the photovoltaic array from operating at the maximum power point. Swarm intelligence algorithms perform well when solving multi-extremum functions and can be used for MPPT control of photovoltaic arrays in complex environments. Therefore, this paper focuses on the fireworks algorithm (FWA). To improve the computational speed and global optimization capability of the FWA, the characteristics of each stage of the algorithm are analyzed, a comprehensive improved fireworks algorithm (CIFWA) is proposed, and it is applied to the MPPT control of photovoltaic systems. The improved algorithm introduces an adaptive resource allocation and selection strategy with community inheritance features and applies tent chaos mapping to the algorithm’s explosion behavior. Multiple sets of test functions are used to compare the performance metrics of the optimization algorithm, demonstrating improvements in computational speed and global search capability of CIFWA. Finally, a control strategy for the MPPT of photovoltaic arrays based on CIFWA is presented, and a simulation experimental platform is built to analyze and verify the control performance. Full article

Photogrammetry-based 3D reconstruction of the shape of fast-moving objects from image sequences presents a complex yet increasingly important challenge. The 3D reconstruction of a large number of fast-moving objects may, for instance, be of high importance in the study of dynamic phenomena such as impact experiments and explosions. In this context, analyzing the 3D shape, size, and motion trajectory of the resulting fragments provides valuable insights into the underlying physical processes, including energy dissipation and material failure. High-speed cameras are typically employed to capture the motion of the resulting fragments. The high cost, the complexity of synchronizing multiple units, and lab conditions often limit the number of high-speed cameras that can be practically deployed in experimental setups. In some cases, only a single high-speed camera will be available or can be used. Challenges such as overlapping fragments, shadows, and dust often complicate tracking and degrade reconstruction quality. These challenges highlight the need for advanced 3D reconstruction techniques capable of handling incomplete, noisy, and occluded data to enable accurate analysis under such extreme conditions. In this paper, we use a combination of photogrammetry, computer vision, and artificial intelligence techniques in order to improve feature detection of moving objects and to enable more robust trajectory and 3D shape reconstruction in complex, real-world scenarios. The focus of this paper is on achieving accurate 3D shape estimation and motion tracking of dynamic objects generated by impact loading using stereo- or monoscopic high-speed cameras. Depending on the object’s rotational behavior and the number of available cameras, two methods are presented, both enabling the successful 3D reconstruction of fragment shapes and motion. Full article

Dust explosion prevention and mitigation of the consequences thereof require measurement of dust explosion parameters. Testing methods are defined by European and American standards, producing results in explosion chambers of a 1 m³ standard volume and, alternatively, 20 L. However, the results are influenced by some processes that are neglected by the standards, perhaps because it is believed that their effect is small in a 1 m³ chamber. But their effect becomes significant in a smaller 20 L chamber. Preconditioning of the system caused by dust dispersion itself, as well as the ignitor flame, is one such problem. The aim of this work is to further investigate the physical and chemical processes caused by dust preheating after an ignitor’s action. Analytical methods, such as STA, GC/MS and FTIR, were used to analyse the composition of the atmosphere after exposure of lycopodium dust, a natural material, to certain temperatures up to 550 °C in air and nitrogen. In the second step, gas samples were taken from the 20 L chamber after dispersion of lycopodium and ignition by two 5 kJ pyrotechnical ignitors. Depending on the temperature and atmosphere, various concentrations of CO, CO₂, H₂O, NO_x and organic compounds were measured. It was observed that the dispersed dust decomposed into mostly CO and CO₂ in the area near the ignitors, even in an atmosphere in which the oxygen concentration was lower than 2% by volume. The concentrations of other organic compounds were very low and included mostly methane, ethylene and acetaldehyde. However, when incorporating CO, the overall concentration of flammables was high enough to generate a hybrid mixture. Full article

The geometric symmetry of the pipeline constitutes a critical determinant in regulating the energy propagation dynamics during the explosion process. In the present study, a transparent plexiglass pipe experimental system incorporating a range of angles (30° to 150°) was meticulously constructed. Leveraging high-frequency pressure sensors in conjunction with high-speed camera technology, this investigation examines the influence of the pipe angle, which disrupts geometric symmetry, on the coupling explosion of gas and coal dust. The experimental findings illustrate that an increase in the pipeline turning angle significantly enhances the velocity of the explosion flame front (with the maximum velocity escalating from 97.92 m/s to 361.28 m/s) and concurrently reduces the total propagation time (from 71 ms to 56.5 ms). Moreover, there is a notable reduction in the duration of the explosion flame, decreasing from 240.5 ms to 64.17 ms at the coal dust deposition point. The peak overpressure of the shock wave exhibits a significant increase with the augmentation of the turning angle (rising from 7.07 kPa at 30° to 88.40 kPa at 150°). Furthermore, the overpressure in the fore section of the turning is amplified, attributable to the superimposition of reflected waves and turbulent effects. This study elucidates critical mechanisms including turbulence-enhanced combustion, secondary dust generation from coal dust, and energy dissipation resulting from abrupt alterations in pipeline geometry, thereby offering a theoretical framework for the prevention and effective emergency management of coal mine explosion disasters. Full article

The inevitable fate of massive stars in the initial mass range of ≈8–$30M_{\odot }$ in the red supergiant (RSG) phase is a core-collapse supernova (SN) explosion, although some stars may collapse directly to a black hole. We know that this is the case, since RSGs have been directly identified and characterized for a number of supernovae (SNe) in pre-explosion archival optical and infrared images. RSGs likely all have some amount of circumstellar matter (CSM), through nominal mass loss, although evidence exists that some RSGs must experience enhanced mass loss during their lifetimes. The SNe from RSGs are hydrogen-rich Type II-Plateau (II-P), and SNe II-P at the low end of the luminosity range tend to arise from low-luminosity RSGs. The typical spectral energy distribution (SED) for such RSGs can generally be fit with a cool photospheric model, whereas the more luminous RSG progenitors of more luminous SNe II-P tend to require a greater quantity of dust in their CSM to account for their SEDs. The SN II-P progenitor luminosity range is $log(L_{\mathrm{bol}}/L_{\odot })\sim 4.0$–5.2. The fact RSGs are known up to $log(L_{\mathrm{bol}}/L_{\odot })\sim 5.7$ leads to the so-called “RSG problem”, which may, in the end, be a result of small number of available statistics to date. Full article

This study investigated the inhibitory effect and mechanism of modified ultrafine ABC powder on the explosion of a methane (CH₄)/coal dust mixed system. Through experiments, it was found that the addition of ABC powder significantly weakened the deflagration characteristics of the CH₄/coal dust mixture system. During decomposition, heat was absorbed to generate ammonia and phosphoric acid. Inert gases such as CO₂ and water vapor produced during decomposition could dilute the oxygen concentration. Phosphate ions produced during the decomposition of ammonium phosphate would bind with free radicals during combustion, reducing their reactivity. The explosion reaction was suppressed through a dual mechanism of physical cooling and chemical consumption of free radicals. The experimental results showed that the weight loss rate of modified ABC powder was 49% at 800 °C, while the weight loss rate of unmodified ABC powder was 78%. The modified ABC powder had better thermal stability and could absorb more heat at high temperatures, further suppressing explosive reactions. This study provides a new modification scheme for explosion suppressants for coal mine safety, which has important theoretical and practical application value. Full article

Coal resources still occupy a dominant position in the energy consumption structure, and the prevention and control of coal dust explosion has become an important measure to ensure the safe production of coal. To this end, a new type of environmentally friendly, economical, and efficient composite powder explosion suppressant has been developed. CMS@C₁₂H₂₂O₁₄Fe was prepared by an anti-solvent crystallization method using Chinese Maifan stone (CMS) as the carrier and ferrous gluconate (C₁₂H₂₂O₁₄Fe) as the active component. The physicochemical properties of the explosion suppressant were analyzed using characterization techniques such as SEM and FT-IR. At the same time, the Hartmann tube experimental device was utilized to study the inhibition effect of the detonation suppressor on the coal powder flame, and to determine the optimal loading amount of the active component and the addition amount of the detonation suppressor. The results show that the composite powder synthesized by the anti-solvent crystallization method has a uniform particle size and good structure. The flame was almost completely suppressed when the active component loading was 50 wt.% and the additive amount of the detonation suppressant was 30 wt.%. Finally, a physicochemical synergistic inhibition mechanism of CMS@C₁₂H₂₂O₁₄Fe for coal dust explosion is proposed. Full article

This study investigates the correlations between the wear conditions of conical pick cutters and key variables such as the physical properties (shape, aspect ratio, roughness), explosive potential, health and safety implications, and particle size distribution of coal dust and larger fragments using the linear cutting machine (LCM). This research was conducted within the framework of recent regulatory developments, notably implementing the new silica rule in the mining and construction sectors and climate change consideration. This study reveals critical insights into optimizing operational processes while adhering to stringent health and safety regulations. The findings indicate that as cutting tools wear, there is a significant increase in generated fine particles, including respirable crystalline silica (RCS), which elevates the risk of respiratory diseases and, in the case of coal dust, a higher potential for explosions. The results show that the silica content in respirable dust is a function of rock mineralogy; however, the results showed that the absolute amount of silica-containing dust increased with bit wear in rocks containing pertinent minerals. For the larger fragments, the new bit produced a 1699 fragment count, while the completely worn-out bit produced a 5608 count. The results of the dust concentration show that the new bit produces 89.2 mg/m³ (17.84%); the moderate bit produces 165.1 mg/m³ (33.03%), and the worn-out bit produces 245.6 mg/m³ (49.13%). Moreover, this study highlights the impact of bit wear on the production of larger fragments, which decreases with tool degradation, further contributing to dust generation. These results suggest the necessity for proactive equipment maintenance, enhanced dust control measures, and continuous monitoring of cutting tool wear to ensure compliance with regulatory standards and to protect workers’ health and safety. Full article

Coal mining frequently sees explosions caused by methane/coal dust mixtures, resulting in significant harm to people and property damage. This study utilized the Hartmann pipe experiment to investigate the inhibition mechanisms of ultrafine water mist (UWM) containing phosphorus-based sodium inhibitors (sodium dihydrogen phosphate (NaH₂PO₄) and sodium phytate (C₆H₆Na₁₂O₂₄P₆)) on methane/coal dust hybrid explosions. The results indicate that UWM containing NaH₂PO₄ and C₆H₆Na₁₂O₂₄P₆ significantly reduces flame propagation velocity, flame height, and flame temperature, thereby effectively inhibiting the development of methane/coal dust hybrid explosion flames. UWM containing C₆H₆Na₁₂O₂₄P₆ exhibited superior inhibition performance, reducing the flame temperature to 157.6 °C, the peak flame propagation velocity by 2.26 m/s, and the flame height by 5.66 mm. The inhibition mechanism of UWM containing phosphorus-based sodium inhibitors primarily involves physical heat absorption and chemical inhibition. The evaporation of UWM absorbs heat, thereby reducing the temperature in the reaction zone. Simultaneously, it generates a large amount of water vapor, which dilutes the fuel concentration per unit volume and reduces the collision frequency between fuel molecules and oxygen. The active free radicals (such as sodium oxygen radical (NaO), metaphosphoric acid (HPO₂), HOPO (peroxyphosphate radical), etc.) produced by the decomposition of NaH₂PO₄ and C₆H₆Na₁₂O₂₄P₆ react with free radicals (O, H, and OH), effectively reducing the concentration of free radicals, interrupting the chain reaction, and weakening the explosive severity. The decomposition products of the phosphorus-sodium components increase the heat capacity of the combustion products, dilute and isolate the combustion zone, and further reduce the explosive severity. These findings provide significant scientific and engineering support for the safe management of coal mines. Full article

In coal mines, the mixture of coal dust and gas is more ignitable than gas alone, posing a high explosion risk to workers. Using the explosion tube, this study examines the explosion propagation characteristics and flame temperature of low-concentration gas and coal dust mixtures with various particle sizes. The CPD model and Chemkin-Pro 19.2 simulate the reaction kinetics of these explosions. Findings show that when the gas concentration is below its explosive limit, coal dust addition lowers the gas’s explosive threshold, potentially causing an explosion. Coal particle size significantly affects explosion propagation dynamics, with smaller particles producing faster flame velocities and higher temperatures. Due to their larger surface area, smaller particles absorb heat faster and undergo thermal decomposition, releasing combustible gases that intensify the explosion flame. The predicted yield of light gases from both coal types exceeds 40 wt% daf, raising combustible gas concentrations in the system. When accumulated reaction heat elevates the gas concentration to its explosive limit, an explosion occurs. These results are crucial for preventing gas and coal dust explosion accidents in coal mines. Full article

This article presents the results of analysis of the hazards posed by coal mine dust and methane in the coal preparation plants of hard coal mines in Poland. It was shown how the number of workplaces in plants at risk of coal dust explosion and the highest permissible dust concentration changed in the period from 2003 to 2022 when compared with coal production. The methodology of assessing mine dust hazards was based on hazard ratios related to one million tons of hard coal enriched in preparation plants. As a result of the analysis, it was found that the explosion hazard index with zone 20 showed an increasing trend in the analyzed period, while the explosion hazard indices with zones 21 and 22 analyzed together and the maximum permissible dust concentration showed decreasing trends following a decrease in hard coal production. In the case of methane, no zone 0 explosion hazards were found, and there were only a few instances of zone 1 explosion hazards. However, it was determined that the explosion hazard index for zone 2 showed an increasing trend during the analyzed period, which is directly proportional to the coal produced and is a result of increasing depth of mining. Full article

In this paper, an improved 100 CMM regenerative thermal oxidizer (RTO) is implemented for low-emission combustion. The existing RTO system is a cylindrical drum structure that cyclically introduces and discharges VOC gas into and from the rotating disk, and which achieves excellent energy efficiency with a heat recovery rate of more than 95%. However, the drive shaft designed under the RTO combustion chamber increases wear around the rotating shaft due to the load of the combustion chamber and there is a problem that the untreated gas is simultaneously released through the outlet due to the channeling phenomenon of the combustion chamber and the drive shaft. In addition, the combustion chamber, used at a high temperature of 800 °C, may cause serious problems such as rotation stop or explosion due to pollutants, dust accumulation, and thermal expansion in the chamber. Particularly when treating VOCs harmful gasses, RTO performance may be degraded due to the burner’s non-uniform temperature control and unstable combustion function. To solve this problem, first, the design of the combustion chamber rotating plate driving device is improved. Second, when treating high concentration VOC gas, the design of combustion chamber considers a temperature increase of up to 920 °C or more. For this, the diameter of the gas burner is 125 mm and the outlet dimension is set to 650 mm × 650 mm to effectively discharge high-temperature waste heat. Third, the heat storage material in the combustion chamber is composed of a ceramic block with a thickness of 250 mm, and the outer diameter and height of the combustion chamber are set to, 2530 mm and 1875 mm, respectively, to optimize gas residence time and heat insulation thickness. Fourth, we supplement safe operation by applying the trip control algorithm of the programmable logic controller (PLC) panel for failure prediction of RTO and the Edge-IoT-based intelligent algorithm for this. Finally, we evaluate the economic performance of 100 CMM RTO by conducting empirical experiments to analyze changes in VOCs removal efficiency, nitrogen oxide emission concentration, and total hydrocarbon (THC) concentration through 10 CMM design and implementation. Full article