首页期刊导航|Fire safety journal: An international journal devoted to research on fire safety science and engineering
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Fire safety journal: An international journal devoted to research on fire safety science and engineering
Elsevier Science
Fire safety journal: An international journal devoted to research on fire safety science and engineering

Elsevier Science

0379-7112

Fire safety journal: An international journal devoted to research on fire safety science and engineering/Journal Fire safety journal: An international journal devoted to research on fire safety science and engineering
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    Modeling of the gravitational deposition of firebrands subject to a turbulent jet flow

    Damiani, PatrickMankame, AdityaShotorban, Babak
    1.1-1.15页
    查看更多>>摘要：The deposition of firebrands carried by horizontal round jet flow was investigated using Lagrangian tracking and large-eddy simulation with a version of FDS modified by our group to include new features for additional Lagrangian models (e.g., Mankame & Shotorban, 2021). The simulations were configured to replicate previous VUFP firebrand generator experiments (Wadhwani et al., 2017), where firebrands were carried by airflow through a pipe and the resulting jet flow, before deposited on the ground. Validation of jet flow simulation was performed by comparing jet spread rate and velocity decay constant against previous experimental and theoretical values for free jet flows. Firebrands were released from the jet exit. Both drag and gravitational forces were found to play significant roles in firebrand motion, with drag reversal observed when firebrands exited the jet flow-initially accelerating and later impeding forward motion. Quantitative analysis using particle time constants and terminal velocities indicated that small-scale turbulence had a negligible effect on the firebrand trajectories, explaining the observed smoothness of the trajectories. The firebrand simulations were assessed for the considered Lagrangian models by comparing the probability density functions of the deposited firebrands' coordinates against those reported in previous experimental and simulation studies (Wadhwani et al., 2017).
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    • NETL
    • NSTL
    • Elsevier

    Experimental observation of the quenching distance of flames propagating in a closed duct at different velocities and with different Lewis and Zeldovich numbers

    Lauermann, Carlos H.Cardoso, Guilherme R.Nzinga, Manuel A. K.Hayashi, Thamy C....
    1.1-1.9页
    查看更多>>摘要：Investigation of the quenching distance is important for the design of flame arresters. The quenching process is related to the coupled effects of heat and mass transfer in reactive flows. The aim of this work is to experimentally determine the quenching distance of flames propagating in a closed duct. The mixtures involve natural gas, hydrogen, helium and air to obtain Lewis and Zeldovich numbers from 0.6 to 1.36 and from 4.24 to 8.45, respectively. In addition, obstacles were placed inside the duct to evaluate the effect of flame propagation velocity on the quenching distance via the Peclet number. The quenching distance was measured as the distance between two horizontal plates that does not allow the flame to continue propagating. The results show that mixtures with Lewis numbers less than one and low values of Zeldovich have the smallest quenching distances. Conversely, mixtures with Lewis numbers greater than one or high Zeldovich values have higher quenching distances. When mass diffusion dominates over heat diffusion, the flame temperature is higher. In addition, the negative exponential dependence of the heat release is controlled by the Zeldovich number. This explains the experimental results. In the experiments where the flame velocity was increased by obstacles, the mixtures with high Zeldovich number increased their quenching distance, whereas the opposite was observed for mixtures with low Zeldovich. The Peclet numbers determined show that advection dominates over heat diffusion. The critical Peclet numbers calculated on the basis of laminar flame velocity were always less than 35.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    Geometric and radiative characteristics of different flame patterns in fire whirl using 3D flame reconstruction

    Liu, ZhihuiLei, JiaoHuang, PengchengYu, Hui...
    1.1-1.11页
    查看更多>>摘要：This paper presents an experimental study on the geometric and radiative characteristics of the different flame patterns in fire whirl within a wide range of the imposed circulations (F) based on the 3D visual hull reconstruction algorithm. The results showed that with increasing F, the mean flame volume decreases steadily for the weak and conical fire whirls, and increases significantly for the cylindrical fire whirl. In contrast to the weak and conical fire whirl, the centerline flame temperature and the external radiative heat flux of the cylindrical fire whirl decrease and increase steadily with F, respectively. The calculated mean flame emissivity and radiation fraction, based on 3D flame model, are found to decrease steadily with increasing F for the weak and conical fire whirls, and increase monotonically for the cylindrical fire whirls, with the maximum flame emissivity of 0.251 and the maximum radiation fraction of 0.703, 2.46 times and 2.79 times of the free buoyant flame, respectively. This indicates that the thermal hazard of cylindrical fire whirls is enhanced significantly compared to the other flame patterns. The variation of the soot volume fraction with F was elucidated physically according to the turbulent mixing concept.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    Evaluation of a fire protection network (FPN) model using open top combustible containers

    Han, DongWhite, JamesXin, Yibing
    1.1-1.10页
    查看更多>>摘要：In many situations, large-scale fire tests are the only way to validate sprinkler protection design. However, testing capability may sometimes be hindered by laboratory limitations. To explore potential strategies to overcome these limitations, a fire protection network (FPN) model was developed to provide an alternative solution for the above situations, by supplementing limited test observations with model predictions to reach a conclusive result, without repeating the same test or requiring additional tests. The FPN model is a network model that treats various burning surfaces as different types of fuel nodes. Simplified fire spread sub-models are proposed using effective parameters, whose values are taken either from the literature or via optimization against fire tests. The FPN model shows a reasonable agreement against observations from a large-scale fire test, which demonstrates its potential to predict the sprinkler demand for scenarios beyond laboratory limitations.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    Nonlinear impacts of fuel load on rate of spread and residence time in forest surface fires

    Wang, HaiyanZhang, JunzhaoFan, ChengZhong, Hongbin...
    1.1-1.11页
    查看更多>>摘要：Frequent and extreme forest fires not only damage the environment but also pose a serious threat to firefighting personnel. Understanding the rate of spread (ROS) is crucial for developing effective firefighting strategies. Surface fuel load serves as the foundation for forest combustion, yet its effect on the ROS of surface fires remains contentious. To investigate the impact of fuel load on surface fire ROS, this study uses pine needles as the fuel material, simulating the accumulation of surface combustibles in forests by increasing fuel load, while also examining fuel depth and packing ratio under each load condition. Using an experimental system capable of measuring the ROS at multiple points along the fire line, we evaluated the ROS of surface fires within a fuel load range of 0.4-3.0 kg/m2. The effects of packing ratio and fuel depth on ROS under different load conditions were discussed, and the influence of fuel load on fire line residence time was also explored. The results indicate that increasing fuel load leads to higher packing ratios and greater fuel bed depth due to the compressibility and weight of the pine needles. Within the studied load range, ROS does not follow a simple linear trend; instead, it initially rises, then decreases, and finally shows a slow increase. This non-linear behavior arises from the combined, and at times opposing, effects of packing ratio and fuel depth on ROS. Additionally, as fuel load increases, the residence time of the fire line follows a pattern of slow increase, sharp rise, and gradual further increase. The growth in flame depth, driven by higher fuel loads, ultimately becomes the dominant factor in prolonging the residence time. These findings provide valuable experimental data to enhance the understanding of forest surface fire dynamics and fuel load effects.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    Residual load-bearing capacity of large-scale prestressed concrete roof slabs after fire exposure

    Fu, ChuanguoWang, YunxingHe, GuoxiWang, Gaojian...
    1.1-1.34页
    查看更多>>摘要：Large-scale prestressed concrete (PC) roof-slabs are fundamental structural components extensively used in industrial construction. These slabs have large spans and thin profiles, rendering them susceptible to substantial degradation in load-bearing capacity when exposed to high-temperature fires. Currently, there is a lack of experimental research data on the performance deterioration of such large-scale slabs under high-temperature fire conditions. This highlights the significance of conducting experimental investigations into the fire resistance properties of large-scale PC slabs from theoretical and practical perspectives. In this study, 11 large-scale PC slab specimens were manufactured, with three slabs designated as reference specimens for comparison at ambient temperature. Leveraging a large-scale fire simulation test system, the remaining eight PC slabs were subjected to post-fire residual load-bearing performance tests, considering variations in fire exposure duration and cooling methods. The temperature field distribution during the heating and cooling processes, the deflection deformation characteristics, and the crack distribution patterns after cooling of the PC slabs were observed and analyzed. Furthermore, a comparative analysis was conducted to assess the impact of different fire exposure durations and cooling methods on the degradation of the overall load-bearing performance of slabs. Post-fire static loading tests showed that the slabs retained good overall load-bearing performance after fire exposure. The slabs exhibited the structural characteristics of integrated slab and rib behavior, with the primary rib remaining the key load-bearing component. The overall load-bearing capacity of the slabs after a fire primarily depends on the residual load-bearing capacity of the primary and secondary ribs. Compared to slabs under ambient conditions, the overall flexural stiffness and ultimate load-bearing capacity of the fire-exposed slabs showed varying degrees of reduction. The slabs subjected to natural cooling after different fire exposure durations (30, 45, 60 and 75 min) experienced reductions in ultimate load-bearing capacity by 1.5, 2.3, 4.4, and 15 %, respectively, compared to ambient-condition slabs. For slabs cooled with water, the reductions were 2.8, 6.0, 7.4, and 12.4 %, respectively. The flexural stiffness of slabs cooled naturally after fire exposure was lower than that of slabs cooled with water. The experimental results indicated that large-scale PC slabs exposed to fire for equivalent standard heating times of 24, 39, and 50 min experienced less than 8 % reduction in overall post-fire load-bearing capacity. Therefore, from a load-bearing capacity perspective, large-scale slabs of this type exposed to standard heating for up to 50 min still maintain good load-bearing performance. The findings of this study provide valuable reference data for fire-resistant design, post-fire assessment, and reinforcement of large-scale PC slabs.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    Structural behavior of timber columns in wood crib compartment fire tests

    Renard, SilvioRobert, FabienneFranssen, Jean-MarcZehfuss, Jochen...
    1.1-1.14页
    查看更多>>摘要：Timber framing is increasingly used as a load-bearing structural system in mid-rise and high-rise buildings. While extensive data exists from standard furnace tests, there is a lack of data on the fire performance of loaded timber members in full-scale compartment fires. Compartment fire tests are crucial to investigate a structure's performance under conditions where the fire is let to grow naturally with the fuel and oxygen present in the room and then let to cool down as the fuel burns out. This paper presents the findings from six fire tests performed on glue laminated timber columns in a custom-built compartment. Wood cribs are used as fuel. The columns, 3680 mm long with a 280 x 280 mm2 section, are subjected to constant axial loading during the whole fire duration. Column design and loading are based on a 60-min fire resistance. The tests vary in opening factor, fire load, and wood crib size. Column failure was observed in the six tests, with failure times ranging from 35 to 71 min. In four of the tests, failure occurred after the gas temperature had started to cool down. Comparisons with tests on similar columns made in a fire resistance furnace allow comparing charring rates observed in standard conditions and in natural fires.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    Upward flame spread of flame-retardant cables with different ATH contents: Ignition, swelling, melting and flowing

    Fang, QianLiu, XiongjunYang, YeHan, Xiao...
    1.1-1.9页
    查看更多>>摘要：To investigate the specific ignition and upward burning behaviors of flame retardant (FR) cables, series of experiments were conducted for FR-cables with mass fractions of aluminum hydroxide (ATH) of 58 %, 61 %, 64 %, 67 %, 70 % and 73 %, respectively. The results show that all studied FR-cables can be ignited by a coil heater delivering a heat flux of approximately 29 kW/m2, with the longest ignition delays for the samples containing the highest ATH content. Compared to FR-cables with 67 % and 70 % ATH contents, the melting and downward flowing are more pronounced for the samples of 58 %, 61 % and 64 % ATH, resulting in stronger burning with longer flame length and width. The upward flame spread velocities for all FR-cable samples are in the range of 1.2-1.6 mm/s and slightly smaller for cables with higher ATH contents. Specifically, the strong downward flowing of the melting liquid in the burning zone obviously slows down their upward flame spread. Dimensionless pyrolysis depth and flowing length are introduced to quantitatively describe the unique burning behaviors of FR-cables and a corresponding new flame spread model is developed based on energy conservation. The good agreement between the experimental and calculated data suggests its effectiveness and reasonability.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    Influences of typical forest vegetation combustion processes on breakdown characteristics and mechanisms of wire-wire air gaps

    Chen, GuoweiYou, FeiChen, SiyiZhang, Yun...
    1.1-1.17页
    查看更多>>摘要：Worldwide, high voltage transmission lines have been suffering from frequent tripping accidents caused by wildfires. To further investigates the impacts of wildfire on breakdown characteristics and mechanisms of wirewire air gaps, three typical forest vegetation samples were used as simulated fire sources in this work. Two segments of aluminum conductors steel reinforced (ACSR) were used as electrodes. The main flame characteristics, mass loss rate (MLR), and heat release rate (HRR) of the vegetation, main discharge breakdown characteristics of the wire-wire gap distances (5.0-25.0 cm) with fire, and the arc evolution processes under flame conditions were measured and analyzed. Results show that fir has the highest combustion intensity. In both flame zones, the wire-wire air gaps of fir are all the most prone to discharge breakdowns, except for a 5 cm gap in oscillating flame zone. Eucalyptus always shows a medium difficulty. The mean breakdown field strengths of eucalyptus, thatch and fir in continuous and oscillating flame zones decrease sequentially by 78.02 %-84.67 % and 46.51 %-53.67 % respectively compared to that in pure air. Mechanism analyses indicate that high temperatures, ionized particles, thermal convection, radiation, flame zones and electric field interactions are the primary driving forces, reducing gap insulation, and ultimately leading to breakdown.
      原文链接:
    • NETL
    • NSTL
    • Elsevier

    CFD analysis of performance-based explosion protection design for battery energy storage systems (BESS)

    Olugbemide, DamilareRyder, Noah
    1.1-1.17页
    查看更多>>摘要：This study evaluates three explosion protection designs for a Battery Energy Storage System (BESS) unit as part of a Hazard Mitigation Analysis (HMA). This is done in accordance with the requirements for explosion protection in NFPA 855, Standard for the Installation of Stationary Energy Storage Systems. The BESS unit is a lithium-ion-based stationary energy storage system with nominal internal dimensions of 3.1 m (L) x 2.1 m (W) x 2.4 m (H) and a free air volume of 6.1 m3. It has four racks composed of eight modules each. Two commercially available cells-EVE and CATL-are used in the analysis to highlight the differences between cell compositions and the implications for explosion pressure and flame propagation. The analysis is performed using the FLACS (Flame Acceleration Simulator) computational fluid dynamics (CFD) tool developed by Gexcon. The three designs considered are natural ventilation, combustible concentration reduction, and standard deflagration venting. For the natural ventilation method, the installed ventilation panel is designed to open at 60o (to the horizontal plane) on activation by a gas sensor located in the BESS unit. The sensor triggers the ventilation panel actuator when the concentration of the released gas inside the unit has reached a predetermined level. The analysis determines whether the natural ventilation provided by the vent opening is sufficient to maintain the gas concentration within the unit at or below 25 % of the lower flammability limit (LFL), thereby preventing an explosion in the unit. The combustible concentration reduction method is one of the standard methods of deflagration prevention for equipment handling combustible materials discussed in NFPA 69, Standard on Explosion Prevention System. NFPA 69 requires that the mechanical ventilation provided for the unit should be sufficient to maintain the gas concentration within it at or below 25 % of the LFL. The third and final design is standard deflagration venting as specified in NFPA 68, Standard Explosion Protection by Deflagration Venting. A single vent panel is provided to relieve explosion pressure in the unit. It is designed to activate at a static pressure (Pstat) of 0.05 bar-g. The analysis determines whether the vent size is adequate to safely vent the unit and prevent its structural failure in the event of a deflagration. Results of large-scale testing show that for typical BESS units, panels, fasteners, and other components may begin to fail at about 0.07-0.14 bar-g. Thus, this pressure range is used as the performance criterion for this analysis. The results of this analysis show that the second design option (the combustible concentration reduction method) provides the best outcome for explosion protection of the BESS unit. The other designs provide modest degrees of pressure relief, depending on several factors. Consequently, these design approaches can be considered individually or combined as an innovative performance-based design approach to protect BESS installations.
      原文链接:
    • NETL
    • NSTL
    • Elsevier