Fire Technology最新文献

Wildfire risk and the extent of burned areas have been increasing in the Mediterranean region over recent decades, driven by high temperatures, low humidity, and extreme weather conditions intensified by climate change. Especially Greece, due to the country's diverse natural environment, has recently faced increasingly intense wildfires which have challenged firefighting efforts. The prediction of smoke dispersion can provide crucial information for enhancing fire management operations. In this study, an integrated Air Quality and Fire Modeling System based on WRF-SFIRE-Chem model has been developed to predict the wildfire spread, smoke dispersion and the distribution of PM₁₀ and CO under specific weather conditions that significantly affect the fire by performing simulation scenarios on selected days—based on the Fire Weather Index (FWI) estimation—and specified fire ignition points. Two areas with specific interest were selected: i) the Samaria Gorge in Crete and ii) the cross-border forest area of Skopos in Western Macedonia. Results showed that the large-scale weather conditions and the local weather created by the fire, play a significant role in the pollutants’ dispersion and ground level concentrations. In the case of Samaria gorge, PM₁₀ can reach up 11,238 μg/m³ at Ksiloskalo and 4629 μg/m³ at Agia Roumeli, and the ignition locations of the fire, even if in close distances, can result in different fire behavior and further to dissimilar smoke dispersion in the wider area. In the case of cross border area of Western Macedonia, PM₁₀ can reach up to 2500μg/m³ at Skopos village and 3000μg/m³ at Agios Athanasios in the case of a wildfire event in the attached forest area. The developed fire and air quality modeling system, provides specialised understanding on the prevailing dispersion patterns of PM₁₀ and CO in the regions surrounding the areas of interest, for planning future fire risk management systems, designing efficiency cooperative prevention and evacuation strategies.

Graphical Abstract

Several technologies such as forced ventilation, active fire-fighting systems, and passive fire protection systems are used in current practice to mitigate fire-induced structural damage to concrete liners in roadway tunnels. This paper outlines a new decision-making approach to optimize these strategies by weighing their initial investment and life cycle costs against their relative impact for enhancing the tunnel’s resilience to fire (quantified in terms of post-fire downtime and cost as a function of the severity of fire-induced damage). First, a concrete liner damage assessment tool is developed to account for the presence or lack of active and passive fire protection, as well as realistic uncertainties in the thermal properties of the materials used. Second, both the cost of protection and the potential economic loss due to stochastic vehicle fire hazards are quantified for a single mitigation strategy or a combination of strategies. The economic losses include the direct repair cost and the functionality loss and detour distance due to the duration of tunnel closure, which is determined as a function of concrete liner damage severity and the corresponding repair procedures. Third, a genetic algorithm is used to perform a multi-objective optimization, resulting in a Pareto front as the reference for the decision-making process. The objectives and constraints of the algorithm can be readily modified based on practical engineering requirements. The proposed approach is then used to evaluate the sensitivity of fire protection selection to tunnel geometry, traffic volume and composition, and detour distance during closure.

Lithium-ion batteries (LIBs) overheating caused by fast charging extremely enhances the risk of battery thermal runaway and the resulting fire and explosion accidents, severely threating electric vehicle safety. To relief the temperature rise of batteries during fast charging, forced convection cooling is expected but improper cooling strategy may lead to lithium plating and thermal inhomogeneity. For investigating the LIB electrochemical and thermal characteristics under forced convection condition, a multi-dimensional electrochemical–thermal coupled model of 2.6Ah 18650 LIB is developed in this work, with which effects of charging rate and convection heat transfer coefficient are clarified. From the results, the critical charging rate of lithium plating is 4 C, and with further increased charging rate, nonlinear growth of abnormal electrochemical characteristics related to lithium plating indicating shorten lifetime and enhanced possibility of internal short circuit. At high charging rate, irreversible heat showing difference in different LIB components dominates the total heat generation, causing large temperature rise and uneven temperature distribution inside the LIB, extremely enhancing the risk of over-aging and thermal runaway. Adopting high convection heat transfer coefficient is proved to effectively alleviate the temperature rise at large charging rate, but the augmented levels of heat generation with large difference of thermal conductivity inside and outside the LIB induce a large temperature gradient, causing inhomogeneity in electrochemical characteristics and an enhancement of lithium plating. These findings will provide effective guidance for developing appropriate cooling strategy to achieve reliable fire protection while minimizing the adverse effects of cooling.

At present, there is a lack of fire risk assessment models and effective fire prevention measures for wooden components in historical buildings that are susceptible to fires. This paper combines the physical principles of fire spread and the basic principles of directed graphs to propose the directed graphical combined breadth-first search (DG-BFS) model, which can infer the real-time fire spread situation accurately and quickly. With the assistance of the DG-BFS model, historical building fire risk assessments are conducted using generated spread matrices, taking into account static metrics related to building parameters and dynamic factors associated with environmental conditions. Additionally, it employs node importance metrics, such as in-degree and out-degree, to evaluate the fire risk level of building nodes. In order to prevent and control the spread of the fire under the existing building, the directed graphical model employs a node deletion measure to assess the feasibility of reducing fire risk through the insulation of individual buildings. Through simulations of fire spread in actual villages in Guizhou province, the results demonstrate that the application of the aforementioned methods, combined with fire safety reinforcement of a small number of high-risk buildings, can significantly reduce the number of buildings ignited after a fire. These findings provide a method for improving fire risk assessment in historical wooden building clusters, particularly in cases with limited data, offering valuable guidance for research and practice in related fields.

Occupant evacuation is a critical aspect of fire safety in buildings. Most evacuation strategies and design principles are based on data from adults, leaving gaps in understanding the unique evacuation behaviours of children. This study examines the movement characteristics of kindergarten children (ages 4–7) during evacuation drills in a primary school. Speed and flow were analysed in corridors and through exit doors of varying widths using video recordings. The findings reveal distinct behaviours, such as the absence of personal space and group-based movement, which differ significantly from adults. Correlations were observed between exit door width, density, and flow rates, highlighting that density alone does not fully explain evacuation dynamics. These insights emphasize the need for evacuation models tailored to children, addressing their unique behaviours and the effects of escape route design.

Smoldering fire of forest duff releases substantial amounts of gases, with emissions significantly influenced by fuel properties and combustion conditions. This study investigates the transient emissions of four main gas species (CO₂, CO, CH₄, and NH₃) from smoldering forest duff with four distinct particle size ranges (2 < d₁ ≤ 4 mm, 1 < d₂ ≤ 2 mm, 0.425 < d₃ ≤ 1 mm, and d₄ ≤ 0.425 mm) under controlled laboratory conditions. Based on the real-time mass loss rate (MLR), the combustion process was categorized into three stages: ignition, spread (decline and growth), and burn out. During the relatively steady spread (growth) stage, the geometric mean mass flux of CO₂ and CO for the largest particle size (d₁) was relatively higher than that for the smallest particle size (d₄), while NH₃ and CH₄ from d₁ remained lower. Within the spread (growth) stage, the geometric mean emission factor (EF) calculated by MLR (EF_m) was higher than the EF calculated by the carbon balance approach (EF_b) across all particle sizes, with the discrepancy more pronounced in low carbon content particles (d₁ and d₄). The EF(CO₂)/EF(CH₄) ratios can differentiate the various smoldering stages. For the first time, the transient carbon emission factor (CEF) was calculated using two methods, with CEF_m being found to provide more detailed insights into smoldering combustion dynamics. This study enhances the understanding of the gaseous emissions of forest duff across different particle sizes and examines the discrepancies between EF calculation methods.

Tunnel fires and smoke spread can pose significant risks to individuals trapped within. Traditional tunnel ventilation systems often demand high energy consumption, posing challenges for sustainable carbon reduction. This paper develops a 1:15 scale tunnel model to assess how shaft distance with unpowered ventilation caps influences back-layering length and downstream smoke stratification during a fire. The smoke back-layering length gradually increases with the distance between the double shafts. A theoretical model is derived to determine the distance of smoke spread upstream and the critical wind speed required to control the smoke. The smaller the distance between the double shafts, the more intense the mixing of air and smoke at the smoke thermal stratification interface downstream in a tunnel. This study provides a valuable reference for the use of unpowered ventilation caps to improve building ventilation structures and achieve tunnel smoke control.

Shading shacks are commonly installed in highway tunnels to alleviate sudden lighting variations at portal connections and decrease illumination energy demands. Nevertheless, their effects on longitudinal smoke propagation in adjacent tunnel networks during fire incidents remain poorly understood. This study investigates how shading shacks influence inter-tunnel pollutant transfer and develops a novel Shading Shack Smoke Control System (SSSCS) combining overhead smoke barriers with coordinated exhaust ventilation. Experimental-numerical analyses of 100 m spaced twin tunnels reveal that conventional shading shacks restrict smoke diffusion in tunnel connectors while intensifying cross-tunnel contamination, with CO transfer ratios reaching 48%. The SSSCS demonstrates operational efficacy by improving visual clarity, suppressing CO transfer to 17%, and elevating evacuation safety indices. This systematic solution advances fire smoke management protocols for clustered tunnels equipped with shading infrastructure.

Ceramifiable polyolefin composites have a great application prospect in high temperature-resistant wires and cables. Inorganic fillers play an important role in ceramifiable property during the ceramization process. In this paper, we successfully reported the synthesis of ceramifiable composites by using silicon aluminum glass powder as an inorganic filler. The effects of silicon aluminum glass powder on the microstructure, thermal conductivity, bulk density, densification and mechanical properties were compared with wollastonite fibers and silica powder at different temperatures. The result showed that the mechanical behavior and densification of the composites were the highest when the silicon aluminum glass powder was used as the filler. Especially, the PZAH sample composed of 40% polyethylene, 20% zinc borate, 25% ammonium polyphosphate, 15% silicon aluminum glass powder shows exhibited the highest mechanical properties at 1000 °C. At these conditions, the bulk density of composite was 2.15 g/cm³, and flexural strength was over 19 MPa. With the increase of temperature, the reaction of ammonium polyphosphate and zinc borate led to the formation of orthophosphate glass melt. The melt binds the fillers together and ultimately forms ceramics with excellent mechanical properties. The findings in this work provided a feasible strategy for the preparation of good thermal insulation and high flexural strength PE composites.

During wildland fire spread both slope and wind act together to modify fire dynamics, commonly accelerating the rate of fire spread. To investigate this coupling effect, flow field measurements were conducted on stationary gaseous fires produced over a tilt table in a wind tunnel, with fireline intensities ranging from 41 to 123 kW/m. The angle of inclination (θ) and the wind speed (V) were varied from 0 to 30° and 0.30 to 1.27 m/s, respectively. The surface gas velocity of the fire at various downstream locations was measured using temperature-correlation velocimetry (TCV), which was enabled using streamwise temperature signals from an array of micro-thermocouples. The effect of the slope was converted to an equivalent surface velocity, (:{U}_{slope}), following the concept of fire-induced flow over an inclined surface. A momentum analysis was conducted to isolate the coupling effect of slope and wind based on (:{U}_{slope}), V, and the mean measured surface gas velocity within the attached flame region, (:{U}_{attach}). Finally, a relationship was proposed to predict the mean velocity of the downstream flow using the upstream wind velocity, flame geometry, and the angle of inclination. The proposed relationship enables estimation of downstream heat transfer from a flame to unburnt fuel ahead of the fire, providing a generalized method to evaluate the combined slope and wind effect on heating which drives forward fire spread.