A series of experiments was carried out using a 1:10 small-scale model tunnel to investigate the effect of different fire source elevations on the flame merging characteristics of dual fire sources under natural ventilation. CFD numerical simulation software was used to analyze the impact of fire source elevation on flame merging characteristics and air entrainment from the perspectives of lateral velocity, longitudinal velocity, vertical velocity and air entrainment rates. The effects of fire source spacing and heat release rate on the probability of flame merging and the height of the flame merging point under different fire source elevations were investigated. It is found that as the fire source spacing S increases, the flame tilt angle theta first increases and then stabilizes for the first time. With a further increase in S, theta increases again and stabilizes for the second time. The first stabilization is mainly controlled by the interaction between the fire sources, while the second stabilization is primarily influenced by natural ventilation from both ends of the tunnel. As the fire source elevation increases, the flame merging probability decreases with the addition of air entrainment between the fire sources. What is more, when the fire source elevation exceeds 8 cm, the effect of the fire source elevation on the flame merging probability is no longer obvious. The prediction model of flame merging probability under different fire source elevations is proposed. Meanwhile, the dimensionless fire source elevation h/D and the modified dimensionless heat release rate Q(DS)& lowast; are used to express the dimensionless height of flame merging point Z(m)/H-ef. The piecewise function of Z(m)/H-ef and Q(DS)& lowast; is obtained. WhenQ(DS)& lowast;<= 88,h/D <= 8, the relationship between Z(m)/H-ef and Q(DS)& lowast; could be described with exponential function and whenhD>0.8, the fire source elevation has little impact on Z(m)/H-ef. WhenQ(DS)& lowast;>8, Z(m)/H-ef is approximately constant and increases with fire source elevation.
Low-pressure water mist fire extinguishing systems are a cost-effective and highly reliable option for fire protection. However, they have not yet seen widespread use in urban underground utility tunnels. To validate the fire extinguishing effectiveness of the system in cable fires within urban utility tunnels and to identify the key factors influencing its efficiency, a scaled-down test platform for low-pressure water mist fire extinguishing in utility tunnels was constructed, and a series of fire extinguishing tests was conducted. The test results demonstrate that low-pressure water mist can rapidly and effectively extinguish cable fires in utility tunnels, with the quickest fire extinguishing time of 7 s. Within 50 s of activating the system, the internal temperature of the tunnel can be reduced from 650 °C to 40 °C. Among the influencing factors, the pressure and nozzle flow coefficient have a significant impact on the fire extinguishing efficiency, while nozzle spacing has a relatively smaller effect. Thus, when the nozzle spacing meets the requirement of “no dead zones”, priority should be given to increasing the pressure and nozzle flow coefficient.
Accurate monitoring of energy storage battery decay anomalies is the key to ensure the safe operation of battery energy storage systems. Based on the reconfigurable battery topology, a two-level diagnostic method for abnormal battery is proposed in the paper; the primary diagnosis adopts a least-squares support vector machine classification model trained on the full-case full-life simulation data set to screen out the suspected abnormal battery modules; the secondary diagnosis adopts a residual linkage and a gated cyclic unit-based health state estimation model to realize an accurate estimation of the health state of the battery to validate the results of the primary diagnostic. The secondary diagnosis uses a health state estimation model based on residual connection and gated cycle unit to realize accurate estimation of storage battery health state to verify the primary diagnosis results. The experimental results show that the method of this paper is accurate and effective.
This short comment highlights the importance of volatile ruthenium compounds in the nuclear fuel cycle and nuclear power generation. Focusing on its volatile properties, we elucidate its behavior in reprocessing and radiotherapy and explore its impact on safety and efficiency improvements. This study focuses on the partitioning behavior of ruthenium and europium in organic solvents under fire of reprocessing plants and their release behavior during organic solvent combustion, providing important data from a safety perspective. A thorough study of the chemistry of radioactive Ru was conducted, providing detailed information on its behavior and reactions. This study provides essential information for nuclear waste management and other nuclear-related fields. Concerning the behavior of Ru in nitric acid solutions during evaporation and drying, the influence of coexisting nitrates on the formation of ruthenium tetroxide (RuO4) is mentioned in detail. In addition, a staining method for transmission electron microscopy (TEM) using RuO4 is commonly used to observe the microstructure of polymeric materials. Furthermore, two crystal structures of RuO4 were discovered regardless of their volatile properties. The information collected here will contribute to the chemical knowledge of effective strategies for fire safety in power generation and waste treatment.
Char oxidation during the cooling period after a fire is one of the important factors in the self-extinguishment of a timber structural element because it involves a large amount of he at generation. In this study, the char oxidation rates of larch glue laminated timber were measured at various heating intensities, using a cone calorimeter. At a heating intensity of 12.4 kW/m2, char oxidation continued with a mass loss rate of 2.41 × 10-3 kg/m2s and a surface temperature of 501.8°C. At a heating intensity of 8.4 kW/m2, self-stopping of char oxidation occurred with a mass loss rate of 0.12 × 10-3 kg/m2s, which can be regarded as being close to zero. From all the measured values, it was concluded that the char oxidation ceases if the heating intensity is less than 8.4 kW/m2 and if the surface temperature is less than 286.2°C. We also developed a formula to describe the relationship between the mass loss rate and the surface temperature during char oxidation, using an Arrhenius equation. The heat of combustion of the char layer was 23.41MJ/kg in average. Using the conditions and equations obtained from our measurements, it is possible to predict the behaviour of char oxidation in response to temperature of timber structural element. In the future, these values could be applied to a heat conduction calculation programme, which would make it possible to predict the self-stopping of char oxidation by calculation.
This study presents an AI-based prediction model for assessing the likelihood of smoke re-circulation between ventilation shafts, using variables such as ventilation shaft size and height, air intake and exhaust directions, separation between air intake and exhaust openings, airflow rates, fire size, wind speed and wind direction. By providing guidance on ventilation shaft configuration during the initial design phase, this model aims to reduce the time and resources required for extensive computational fluid dynamics (CFD) simulations. Following the initial prediction, CFD simulations can then be conducted by designers to confirm that the proposed ventilation shaft layout will not result in smoke re-circulation. While this approach is not a replacement for CFD, its approach offers a more comprehensive design solution and significantly decreases the number of simulations to be performed.
In the year 2022, a large-scale fire occurred at a chemical factory in Tokyo, Japan. The news media disseminated extensive information about the situation at the scene and called attention to it. A few reports indicated that the chemical “sodium hydroxide”, which was speculated to be stored in large quantities at the factory, was dangerous owing to its ability to make soaps and detergents. After the fire was extinguished, we reviewed news reports to analyze the causes and countermeasures, which led to our findings about (1) the dangerous substance at the scene, (2) knowledge about its hazardous effects, and (3) precautions required in handling these substances. In addition, we realized that the provision of information, such as if evacuation is needed, was not straightforward. Even several months later, the details of the official cause of the fire, to our knowledge, remain undisclosed.
Fires can cause serious damage when widespread. This study focuses on two types of fires, forest and factory fires, and investigates how toxic substances released affect the environment. Forest fires, caused by anthropogenic factors such as arson and natural factors such as lightning strikes, are widespread and severely damage ecosystems. Factory fires, caused by malfunctioning electrical equipment, mishandling of chemicals, or carelessness with fire, cause serious damage to the neighborhoods and environment. In addition, fires may release chemical substances present in factories. Mercury release is a common phenomenon in both fires. Fires burn mercury-containing vegetation and organic matter, thereby releasing mercury into the atmosphere. The released mercury is deposited in the soil, rivers, and other water bodies, accumulates in ecosystems (bioaccumulation), and moves up the food chain to higher organisms. Mercury poisoning can adversely affect the nervous and immune systems, causing developmental problems and impaired learning abilities, particularly in fetuses and young children. To reduce the damage caused owing to mercury release, fire prevention, early response, prevention of mercury spillage, and the proper management and storage of mercury are important. Currently, the international community has started working on the proper handling of mercury among nations by concluding the Minamata Convention.
Traditional fire-fighting robots are limited by fire detection and location technology. The detection and location accuracy are greatly affected by the environment, resulting in poor performance, complex deployment and low intellectualization. In this work, a set of automatic fire location and tracking system is designed and implemented based on deep learning, which is also integrated with video image processing technology and open source computer vision library (OpenCV). The system uses a high-real-time deep learning model for fire detection, and it eliminates false alarms by calculating and comparing the structural similarity ratio of the images, as well as combined with the dynamic characteristics of the flame, thereby further improving the detection accuracy. Additionally, our work facilitates the deployment by taking advantage of the monocular camera to locate and track the fire source. Experimental results have demonstrated that the system delivers advantages such as high detection accuracy, good real-time performance, long monitoring distance, and fast response speed. These results also allow the proposed system to be a prime candidate for fire-fighting robots in various complex environments.
Flame-retardant waterborne polyurethane has long been studied as a flame-retardant, non-flammable, adhesive material for wood, for example. Since there are already many good review articles and specialized books, this chapter will review only the major studies of new flame-retardant aqueous polyurethanes reported in the last few years. In many cases, there is the synthesis of polymer materials, thermal analysis that proves flame retardancy alone or in combination with other materials, as well as FTIR, NMR, MS for structural confirmation, and SEM for aggregate state confirmation. The study may be carried out by several measurements such as EDX analysis. On the other hand, material flammability tests may include limiting oxygen index, vertical combustion, and cone calorimeter tests. This chapter focuses on methods of analytical measurement of flammability, the purpose of these methods, the correlation between flame retardancy and other structures/physical properties, and related experiments and discussions including composite/special measurements such as TGA-FTIR, and in situ FTIR. Additionally, the authors would like to summarize the relationship between analytical measurements such as thermal measurement with other applications such as macromolecules for photochromic and fluorescence.
This study describes the characteristics of chemical fires (fires in laboratories, oil factories, etc.,) caused by earthquakes. First, the relationship between earthquakes and fires (particularly chemical laboratory fires) in Japan is described; afterward, the relationship between chemical substances and the natural environment (particularly fires) is described. Next, we explain the relationship between fire and chemistry after explaining the two past major earthquakes in Japan, the great Hanshin-Awaji earthquake and the great East Japan earthquake, based on statistics and records. Finally, we describe the measures taken against chemical fires and future earthquakes.
为提高复杂环境下烟火识别的精度,提出一种基于3D卷积和时空注意力机制的双波段烟火识别方法,该方法融合近红外和可见光双波段图像数据,使用视频流中基于时间的动态特征和基于空间的静态特征降低漏报率、误报率.实验结果表明,该算法在双波段数据集上的烟火识别精度达到99.90％,优于其他基于3D卷积的烟火识别算法,同时,模型具有较小的参数量,能够满足实时推理需求.因此,使用双波段特征的同时,结合注意力机制充分利用视频的动态信息,可以有效提高烟火识别精度.
设计了压差导流冷却循环回路,并对其影响因素进行了研究.通过构建水泵冷却循环耦合换热数值模型,分析了导 流通道的倾斜角度、孔径大小和水泵转速等对散热的影响.结果表明:相比倾角15°,导流通道倾角55.的平均热交换系数增加了13.2％,在忽略流量损失的条件下,设计采用倾角为55°.随着导流通道半径的增大,固体温度下降趋势减缓,考虑到管径的扩大会增加结构成本和能量损失,取4.5 mm为设计半径值.冷却通道流量与水泵转速基本呈正比,满足不同转速下的散热需求.
