The purpose of this study is to investigate the influence of bending angle and cross-sectional area on the combustion characteristics of suspended cables. A flat three-copper-core cross-linked insulated polyethylene cable with the same length was selected as the research object, and 20 groups of cable combustion tests were carried out. The effects of different bending angles and cross-sectional areas on the fire spread behavior of the cable were analyzed by measuring key parameters such as flame temperature, droplet temperature, cable fire spread time and fire spread speed. The results show that when the bending angle decreases, the flame spread velocity increases first and then decreases, and reaches the peak at θ=90°. The flame spread velocity at this peak state is about 1.6 times that at θ=180°. The cross-sectional area is negatively correlated with the flame spread speed. The flame spread speed of the cross-sectional area 2.5 mm2 cable is 1.9 times that of the 16.0 mm2 cable. At the same time, the smaller the bending angle, the larger the cross-sectional area, the more the number of droplets flowing on the attached cable, and the higher the droplet temperature. In addition, the maximum flame temperature at the bend increases with the decrease of the bending angle. When the cross-sectional area increases, the maximum flame temperature increases first and then decreases.

To investigate the factors influencing the leakage and diffusion of high-pressure hydrogen in a confined volumetric space, we analyzed the effects of ambient temperature, humidity, wind speed, leakage location, and leakage rate on hydrogen concentration distribution through numerical simulation. A high-pressure hydrogen concentration variation model was developed, and sensitivity analysis based on key parameters was conducted. The results indicate that hydrogen exhibits a distinct layered diffusion characteristic within a volumetric confined space. During the transition from vertical to horizontal momentum, the vorticity distribution evolves from an initial V-shaped structure to a later two-vortex core structure. Wind speed significantly impacts the diffusion process, with hydrogen volume fraction decreasing by 22.8% at 3 m/s. Different shapes of leakage holes result in notable variations in hydrogen diffusion behavior; when the leakage area is the same, the local hydrogen volume fraction in square leak holes is 22.94% higher than in round leak holes. The leakage rate (coefficient 0.864) and wind speed (coefficient -0.988) are identified as the primary factors affecting hydrogen diffusion.

Fires under high wind speed conditions are difficult to control and tend to cause more severe losses, but there is relatively little research on such fire scenarios. In this paper, combustion experiments of small-scale n-heptane square pool fires with a side length of 8 cm were carried out behind an obstacle under high wind speed conditions ranging from 10 m/s to 25 m/s in a combustion wind tunnel, and comparisons were made with scenarios of medium and low wind speeds from 1 m/s to 10 m/s. The results show that under medium and low wind speeds, the burning rate increases rapidly with the rise of wind speed in the initial stage, followed by a gradual decrease in the growth rate. When the wind speed exceeds 10 m/s, the burning rate exhibits a relatively stable linear growth with the increase of wind speed. The flame shape presents an arched form under low wind speeds; when the wind speed exceeds 10 m/s, the flame shape gradually transforms into an upward convex arc shape. Corresponding flame lengths and inclination angles were defined according to the different flame shapes under medium-low and high wind speeds. The total flame length decreases with the increase of wind speed, and the rate of decrease accelerates when the wind speed is higher than 10 m/s. The inclination angle of the lower flame segment increases with the rise of wind speed; while the inclination angle of the upper flame segment increases with wind speed under medium and low wind conditions, but decreases with wind speed under high wind conditions. Finally, empirical prediction formulas for the burning rate, flame length and inclination angle of small-scale n-heptane pool fires varying with wind speed were established respectively. The research results can provide theoretical support for fire prevention and control under high wind speed conditions.

Series arc faults in aircraft AC systems pose a critical threat to flight safety because the current amplitude does not exceed protection thresholds, signal distortion is subtle, the detection process is highly susceptible to environmental disturbances and under coupled vibration-humidity conditions, the difficulty of fault detection increases significantly. To address the challenge of robust identification in 115 V/400 Hz systems under multiple operating conditions, this study constructs a series arc fault experimental platform capable of simulating combined vibration and humid-thermal environments, covering representative resistive and resistive-inductive load scenarios. Time-domain statistical analysis, frequency-domain feature analysis, and db4 wavelet multi-scale decomposition are employed, combined with correlation-thresholding, F-value ranking, permutation importance validation, and PCA dimensionality reduction, to obtain a low-redundancy, multi-domain feature set. A grid-optimized RBF-SVM classification model is then applied for fault recognition. Results show that vibration increases the spectral peak of a 10 A series arc fault under resistive-inductive load from 1 767.92 to 9 120.03. Humidity exhibits a dual “suppression-sharpening” effect on transient arc behavior: although wavelet energy decreases by 47.7%, pulse factor and kurtosis increase, indicating enhanced intermittency of discharges. Vibration demonstrates a “promotion-dispersion” effect, raising reignition frequency but dispersing pulse intensity. When coupled, nonlinear competition occurs, leading to an extreme suppression of arc transients, with wavelet energy reduced to 284.69. The proposed multi-domain fusion model achieves an F1-macro score of 0.99, improving by 62.3% compared with time-domain features alone.

This study experimentally investigated the arc electrolysis characteristics and gas production behavior in transformers at different temperatures. The explosion process of the electrolysis gas in transformers was also simulated using Computational Fluid Dynamics (CFD). The results indicate that hydrogen constitutes the highest proportion among the gases produced from soybean-based natural ester, recycled oil-based natural ester, and mineral insulating oil. This high hydrogen content is attributed to the combination of H· radicals generated from C-H bond cleavage under high-voltage arc conditions and the electrolysis of water vapor in the air. Based on reaction kinetics simulations, the yield and temperature sensitivity of key free radicals involved in the oxidation of the electrolysis gases were analyzed under critical equivalence ratio conditions, revealing the main conversion pathway: H₂ →·H→·OH (·O) →H₂O. Numerical simulations clearly demonstrate the evolution of the explosion flame in the electrolytic gas mixture and accurately capture the distribution patterns of explosion pressure and flame temperature. The increased turbulence induced by obstacles is identified as the primary cause for the enhancement of flame speed and explosion pressure, reflecting a positive feedback mechanism driven by the coupling of pressure, flame, and turbulence.

There is a risk of radioactive sodium aerosol diffusion in severe sodium fire accidents, which needs to be controlled. As one of the aerosol control technologies, atomization fixation technology has the advantages of flexibility and efficiency, and has been successfully applied in the field of radioactive aerosol control in foreign nuclear facilities. To explore the feasibility of applying atomization fixation technology in sodium fire protection systems, sodium aerosol suppression experiments were conducted under different droplet size conditions of fixative. Experiments have shown that for sodium carbonate aerosols with a total particle concentration of 105 and a peak particle size of 1 μm, when using a fixed agent at a dosage of 250 mL/m3 and a viscosity of (143.4±3) cp, the settling rates of large (43.055 μm), medium (13.057 μm), and small (8.773 μm) fixed agent droplets pressing sodium aerosols within 30 minutes are 9.10%, 26.60% and 38.55%, respectively. The corresponding average decrease rates of aerosol particle number concentration are 1 099, 1 242 and 1 787 P/(cm3·min), respectively. This is consistent with the theoretical trend that the smaller the droplet of the fixative, the better the compression effect. By disturbing the fixed agent that has settled on the ground, it was determined that the droplet size of the fixed agent has no significant effect on the resuspension effect, and it was also verified that this technology can successfully adhere the aerosol to the ground.

By conducting combustion characteristic tests on LED unit modules in various configurations, the combustion characteristics and spread patterns of LED screens were investigated. Parameters such as the heat release rate, total heat release, and smoke production rate of unit modules in different configurations were measured. Additionally, parameters including the fire growth coefficient and peak heat release rate per unit area during screen combustion were analyzed. The experimental results indicate that when an LED screen catches fire, the flames primarily spread vertically along the screen surface, with negligible horizontal spread. The fire growth coefficient and peak heat release rate per unit area of the LED screen are influenced by factors such as screen height, module arrangement, and the involvement of circuit boards and electronic components on the back of display modules in combustion. During the initial stage of the fire, the fire growth coefficient falls between that of a medium-growth fire and a slow-growth fire. The combustion of LED screens produces significant amounts of dense smoke, accompanied by burning drips. To prevent the spread of fire, combustible materials should not be placed below LED screens, and smoke should be promptly vented in areas where such screens are installed.

To clarify the relationship between longitudinal wind speed and smoke exhaust wind speed under the new one-way large-spacing point-type coordinated smoke exhaust mode in tunnels, this paper defines the safe distance of smoke spread, and discusses the effects of longitudinal wind speed and smoke exhaust wind speed on smoke spread distance under the new smoke exhaust mode. Combined with numerical simulation and scaled-down model tests, the relational expression of smoke exhaust wind speed and longitudinal wind speed satisfying the safe distance of smoke spread is derived, and the correlation between smoke spread distance and the Froude number (Fr) is obtained. The results of the combined analysis of the upstream smoke counterflow length Lup ≤ 30 m and the downstream smoke overflow length Ldown ≤ 4H show that, Lup decreases with the increase of longitudinal wind speed, while the influence law on Ldown is not obvious; the variation of Lup with smoke exhaust wind speed is not significant, whereas Ldown decreases gradually with the increase of smoke exhaust wind speed. When Fr≤0.45 at 30 m upstream of the fire source and Fr≤1.5 at 4H downstream of the smoke vent, the smoke spread is within the safe distance; the dimensionless smoke exhaust wind speed has an exponential relationship with the dimensionless longitudinal wind speed. The scaled-down model tests fully verify the reliability of the numerical simulation and the dimensionless relational expressions.

This study investigates the impact of exterior building fires on both the internal automatic sprinkler system and fire-resistant glass. An experimental platform was developed, and 24 tests were conducted to assess the influence of water on the integrity of fire-resistant glass under simulated outdoor fire conditions. The findings reveal that in all 24 tests, the automatic sprinkler system was activated, and the fire-resistant glass's integrity was compromised. The temperature sensing elements ruptured at temperatures ranging from 84~87 ℃, significantly exceeding their nominal activation temperature of 68 ℃. The study also observed distinct rupture behaviors based on glass thickness: 5, 6, 8, and 10 mm glass panes shattered and detached upon rupture, whereas 12 mm and 15 mm glass panes remained intact as the rupture did not penetrate the glasses. To ensure the fire integrity of building external windows, it is necessary to comprehensively consider the layout of sprinkler heads in automatic sprinkler systems, the testing methods of temperature sensing components, and the selection of fire-resistant glass.

Luggage fires and store fires most likely to occur in railway station buildings were selected for full-scale experiments. Based on the actual conditions of the test site, the minimum width of the fire isolation zone was calculated through theoretical methods. The natural smoke exhaust openings in the large space accounted for 3.5% of the total area, while the openings directly above the fire isolation zone accounted for 20%. The fire separation effectiveness of the isolation zone was studied in terms of smoke spread, toxic components in the smoke, temperature, and thermal radiation intensity. The results showed that the calculated minimum width of the fire isolation zone under the actual conditions of the test site was 6 m. In both luggage fire and store fire experiments, most of the smoke was exhausted outdoors through the smoke vents. The temperature on the side of the fire isolation zone away from the fire source remained close to ambient, and the thermal radiation intensity was nearly 0 kW/m². The fire isolation zone effectively served its purpose of fire separation. The findings of this study can provide a theoretical basis for the design of fire isolation zones in railway station buildings.

Based on the structural features and fire risks of the underground transformer room, a full-scale fire numerical model of a 220 kV transformer was constructed, taking into account the influence of ventilation valves and evacuation doors on airflow. The study investigated the full-surface fire combustion characteristics of the transformer room's emergency oil sump. The results indicate that, regardless of whether the ventilation valves and evacuation doors are open or closed, the combustion in the emergency oil sump is air supply-limited and belongs to ventilation-controlled fires. When both the ventilation valves and evacuation doors are open, the peak heat release rate of the fire source reaches 12 MW; when the ventilation valves are closed and the evacuation doors are open, the peak heat release rate of the fire source is 5 MW. Both values fall short of the theoretical peak heat release rate of the designed fire source. The temperature decreases from the indoor ceiling downward, with the highest temperature on the side walls exceeding 700 °C. When the ventilation valves are open, the peak thermal radiation can exceed 300 kW/m², and the average ceiling temperature can exceed 470 °C, both of which are higher than the values when the valves are closed.

Multi-agent combined foam fire extinguishing technology is an important development direction to solve the challenges of extinguishing flammable liquid fires, which are characterized by high difficulty and easy reignition. However, efficient and environmentally friendly multi-agent combined fire extinguishing technology still requires further research. In this study, a standard positive-pressure multi-agent foam generating device and compressed air foam extinguishant were employed to conduct 1 m² simulated oil tank fire extinguishing tests. The aim was to investigate the fire extinguishing capability of combined technology utilizing compressed air foam with bromotrifluoropropene (BTP) and perfluorohexanone (1230) for 120# solvent oil as standard fuel. The test results demonstrate that under conditions of a gas-to-liquid ratio of 5：1 and a foam mixture supply intensity of 5 L/(min·m²), compressed air foam can effectively extinguish a 1 m² 120# solvent oil tank fire, with a fire control time of 54 s and a complete extinguishment time of 59 s. No reignition occurred after foam supply cessation. Under conditions of a gas-to-liquid ratio of 3：1 and the same foam mixture supply intensity of 5 L/(min·m²), when 0.17 L/min of BTP was injected through positive-pressure spraying, the BTP-containing compressed air foam achieved a fire control time of only 30 s and an extinguishment time of only 33 s for the 1 m² 120# solvent oil tank fire. When 0.19 L/min of 1230 was injected through positive-pressure spraying, the 1230-containing compressed air foam resulted in a fire control time of 54 s and an extinguishment time of 58 s for the same fire scenario.

This paper discusses the application of lightweight attack hoses in internal attack firefighting operations. Through comparative tests, the performances of lightweight hoses with diameters of ϕ40, ϕ45, ϕ50 and the ϕ65 hose were analyzed in terms of water-filled dragging, water supply, and pressure loss, so as to evaluate whether they meet the requirements of internal attack firefighting. The results show that lightweight hoses have good maneuverability and can satisfy the water supply intensity demand in internal attack firefighting. Meanwhile, this paper summarizes the limitations of lightweight hoses in practical application, such as large pressure loss and easy kinking. In addition, suggestions including the unification of connectors, adoption of double-layer hoses, and priority selection of ϕ45 hoses are put forward, aiming to improve the operational efficiency of lightweight attack hoses in internal attack firefighting.

Aiming at the rapid burning and wide range of forest and grassland surface fires, and the difficult problem of navigation and fire source localization of fire-fighting robots in complex environments, a forest and grassland pneumatic fire-fighting robotic system based on robot operating system（ROS） is designed. The hardware part of the system consists of a tracked robot chassis, fan system, wind turbine control mechanism, and a combination of inertial guidance, camera and LIDAR and other sensors, using GPS satellite positioning information and AMCL algorithm fusion to achieve the robot's localization. Proposing a fuzzy logic-based dynamic weighted A* algorithm to generate the environmental complexity index through fuzzy reasoning on the density of the obstacles and the distribution of the discrete degree in the 25% obstacle density of 30×30 raster map simulation experiments, compared with the traditional A* algorithm, the number of search nodes decreased by about 82.1%, the planning time was shortened by about 52.8%, and the total generation value was reduced by about 1.8%; in the 45% obstacle density of 30×30 raster map simulation experiments, compared with the traditional A* algorithm, the number of search nodes was reduced by about 24.4%, and the total generation value was reduced by about 3.4%, the The planning time is reduced by about 22.3%. The dynamic obstacle influence factor is introduced into the DWA evaluation function, which can accurately reach the target point in a shorter time compared with other algorithms under the premise of guaranteeing the safety; and the blower angle control strategy with flame height feedback is established, which can accurately locate the fire source and adjust the angle of the blower to extinguish the fire. The results show that the system is able to achieve autonomous obstacle avoidance and target positioning in the complex woodland environment, and can meet the demand for fire extinguishing in the complex environment of forest and grassland.

All buildings are mandatorily required to install insulation measures between the exterior wall structural layer and the decorative layer. The exterior wall insulation layer can effectively reduce building energy consumption. To enhance the thermal resistance performance of inorganic fireproof insulation mortar, this study, based on previous research findings, further introduced AOS foaming agent and gelatin to develop a novel foam insulation mortar. While conducting research on the foaming process, the fire resistance of the mortar was also tested. The results indicate that: the optimal foaming effect is achieved when the stirring time is between 5~6 minutes; when the AOS volume fraction in the foaming solution is approximately 1.5%, the generated foam exhibits the highest stability. A gelatin volume fraction of 1.5% in the foaming solution provides better foam stabilization effect, significantly enhancing foam stability. After optimization, the optimal dosages of foaming agent and stabilizing agent were determined to be 1.75% and 1.00%, respectively. The incorporation of foaming agent and gelatin can introduce independent closed-cell pore structures into the insulation mortar, thereby significantly reducing the dry density and thermal conductivity of the mortar. However, it will also have a negative impact on the mechanical properties of the mortar, with particularly significant weakening of the bonding strength.

To address the frequent fires in the transportation and storage of silica mud in recent years, and the lack of effective fire extinguishing methods, this study employed a laboratory-level silica mud stack fire extinguishing test model to evaluate the feasibility of using water to extinguish silica mud stack fires, investigate the effects of extinguishing water with different pH values on the fire-fighting efficiency of silica mud stack fires, and compare the effects of water and foam extinguishing agents on silica mud stack fire-fighting effectiveness. The results show that it is technically feasible to use acidic and neutral water to extinguish silica mud stack fires, while using alkaline water to extinguish fires will lead to a sharp increase in the stack fire, which poses high risk; the lower the pH value of the fire extinguishing water, the better the cooling and fire extinguishing effects; AFFF foam has a good cooling and fire extinguishing effect on the surface of the stack, but has a poor cooling effect on the inside of the stack.

The PEDOT-modified thermoelectric graphene nanosheets (TEG) and adhesive (P(DPOP-Si)) are used as the raw materials to construct fire-retardant nano-coating with fire warning function on the surface of wood by the method of “coating-drying”, to study its fire warning performance and fire-retardant properties and to explore the fire-retardant warning mechanism of the coated wood. The objective of this study is to provide wood with efficient flame retardant properties and early fire warning function at low loading, so as to expand the application fields of wood and wood products. The results showed that the coated wood (WOOD-3) achieved a limiting oxygen index of 37.9%, and the peak heat release rate and total heat release were reduced by 49.3% and 47.3%, respectively, compared with pure wood. In case of fire, the nano-coating triggers the fire alarm within 7 s, which has both better fire warning performance and certain flame retardant properties.

To enhance the efficiency and accuracy of fire rescue missions in complex dynamic environments, this study integrates the equivalent of path congestion as time cost and the equivalent of blockage situations as capacity loss. It also comprehensively considers the impact of spatial turn types and quantities on the cognition and speed of rescue personnel. A Cost Evaluation Model for Transportation (CEMT) is proposed for path planning. Building upon this, a method for calculating passage costs in three-dimensional space and complex environments has been constructed, achieving a more comprehensive and scientific quantification of passage costs. The study explores the impact of various factors on path planning and validates the effectiveness and practicality of the model in evaluating passage costs.

Faced with a large number of firefighting aircraft, safe and scientific allocation of firefighting tasks has become the key to improve the efficiency of firefighting. In this paper, we present a mixed-integer programming model for the firefighting aircraft scheduling problem in large-scale wildfires and develop a branch-and-cut algorithm to solve it. The model has been developed to address the diverse firefighting requirements of different regions at different times. And it ensure that the sum of the target water deficits in each region is minimized to slow down the spread of the fire. In this paper, we combine the flight characteristics and mission constraints of a variety of firefighting aircraft and accelerate the solution process by introducing effective inequalities, and validate the performance of the algorithms on experimental data of different sizes. The results show that the model can be used in complex air resource allocation problems to maximize firefighting efficiency while ensuring safety.

In order to explore effective methods for determining the fire origin through video light and shadow analysis, this paper selects typical cases of fire video light and shadow analysis, extracts the principles of general light and shadow analysis models such as symmetric reflection, three-dimensional occlusion, and geometric calculation of light and shadow dividing lines. A real-scene verification experiment is designed, and its effectiveness in determining the fire origin is verified by combining with real cases. A three-dimensional reconstruction light and shadow analysis simulation experiment is designed. Unreal Engine 5 is used to perform three-dimensional reconstruction of the fire scene, and simulation tests are carried out by using the model auxiliary line method or the simulated light source position trial-and-error method to verify its effectiveness in determining the fire origin. The study can provide practical reference for grass-roots fire investigators, helping to improve the efficiency and accuracy of fire investigation.

This paper focuses on a combustion and explosion incident that occurred in a lithium battery formation workshop. By employing fire investigation methods such as on-site inspection, investigative inquiries, and video analysis, the direct causes of the accident and the factors contributing to the disaster are dissected. Over ten drop tests were conducted on ternary lithium batteries across five categories to summarize the correlation between external short circuits and the occurrence of thermal runaway in lithium batteries under different conditions. The study aims to provide an in-depth analysis of fire incidents at the production end of lithium batteries, discuss corresponding prevention and handling recommendations, reduce the probability of fire accidents in lithium battery factories, and ensure the safe and stable operation of the facilities.