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15 October 2022, Volume 41 Issue 10 Previous Issue    Next Issue

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Progress in suppression and venting mechanism of dust explosion Gao Wei, Jiang Haipeng, Zhang Tianjiao, YANG Mingrui 2022, 41 (10):  1329-1335.  Abstract ( 1154 )   Abstract: Dust explosion protection is an important field to prevent and mitigation safety accidents. Focusing on the problems in low efficiency of dust explosion suppression, flame quenching of high temperature and pressure venting efficiency are difficult to balance, etc., the research on dust explosion suppression and venting technology is carried out. Preventing and mitigating the consequences of accidents has become a hot issue to be solved urgently today. This paper analyzes and summarizes the kinetic mechanism of dust suppression reaction, clarifies the suppression mechanism of suppressants on gas-phase reaction and surface reaction of dust explosion, and introduces the development of high-efficiency suppressants for dust explosion. An accurate prediction model of explosion venting pressure and flame dimension is established. Finally, the characteristics and deficiencies of flameless venting technology and equipment for dust explosion are discussed. This paper has important guiding significance for the efficient prevention and control of dust explosion. Related Articles | Metrics

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Deepen the reform of fire education and teaching and comprehensively improve the quality of personnel training Yan Shengli 2022, 41 (10):  1336-1338.  Abstract ( 1071 )   Abstract: Fire education has the leading, basic and strategic position in fire and rescue team construction. China Fire and Rescue Institute is the only specialized higher education institution for fire protection in China. Explore countermeasures and measures for deepening education and teaching reform, make the scale "stand up", make the students "busy", make the teachers "strong", make the classroom "live", and make the management "strict", comprehensively improve the quality of talent training, build and strengthen China Fire and Rescue Institute, so as to further improve the comprehensive quality, professional ability and combat effectiveness of the national comprehensive fire and rescue team. Related Articles | Metrics

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Prevention and control strategies of fires under extreme weather conditions: A case study of the fires in Sichuan and Chongqing Bai Ye, Cao Meng, Wu Yingda, Yang Shaobin, Du Qiuyang, 2022, 41 (10):  1339-1342.  Abstract ( 1056 )   Abstract: Sichuan and Chongqing region is located in the southwest of China： the Sichuan Basin and the east of Wushan. The vegetation is mainly subtropical evergreen broad-leaved forest, and the fire source is mainly caused by human activities. Affected by extreme heat and drought, the number and intensity of fires in Sichuan and Chongqing have continued to increase, causing serious ecological disasters and social crises. On the basis of summarizing the recent cases of mountain fires in Sichuan and Chongqing, this paper analyzes the main causes of the mountain fires from three aspects: oxygen, combustible materials and ignition sources, and analyzes the difficulties in fighting the fires from the terrain, climate and vegetation. Finally, it puts forward the corresponding prevention and control strategies from multiple perspectives. Related Articles | Metrics

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Analysis of the structure of Chinese autonomous emergency science and engineering knowledge system-new development of modern emergency management theory and method Qian Hongwei, Wang Mingyue, 2022, 41 (10):  1343-1346.  Abstract ( 1045 )   Abstract: It is necessary and urgent to construct Chinese own scientific and engineering knowledge system for emergency response, train the talents of organization, management and engineering technology, effectively deal with emergencies and support large countries' emergency response. Based on the demand of reality, policy transmission and discipline law, this study adopts knowledge production theory, and combines the related research on emerging emergency science and engineering knowledge system. The paper describes and classifies the content of each knowledge branch and the main body of the knowledge system of emergency science, and expounds the complex adaptive characteristics of the knowledge system, the structure of emergency science and engineering knowledge system is constructed, which is composed of three subsystems: knowledge subject subsystem, communication subsystem and application subsystem. The results show that this study can provide reference for the theoretical and applied research on the specific operations of emergency management, and help the emergency practioners to understand the whole process of emergency work systematically from the perspective of knowledge production, and further expand the construction of modern emergency management theories and methods. Related Articles | Metrics

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Experimental study on the spillage characteristics of continuously leaked liquid fuel and potential heat release rates in sloped tunnels Guo Qinghua, Zhang Shaoqi, Zhao Weigang, Yan Zhiguo 2022, 41 (10):  1347-1353.  Abstract ( 1014 )   Abstract: The paper focuses on the fire risk caused by the spilled liquid fuel in tunnels. The small-scale test platform with adjustable longitudinal and transverse slopes was established to study the spillage profile, spillage width and area. Meanwhile, the fire tests were carried out to investigate the impact of the fuel depth on the heat release rates. The results indicate that under the longitudinal slopes, the spillage width and area decreases as the slopes become great. When there are both longitudinal and transverse slopes, the liquid fuel spills towards the tunnel sidewall, and as a result, the spillage length and area decrease. In addition, the average depth spilled liquid investigated in this work is 2 mm, and the heat release rates of the fuel under this depth is 30%~50% of the theoretical values which are obtained by using a deep fuel. Based on the above achievement, the potential heat release rates caused by the spilled liquid fuel fires can be evaluated. The finding is that when the transverse slopes increase from 1% to 2% under a given longitudinal slope of a tunnel, the potential heat release rates of the fires caused by the spilled liquid fuel may be decreased by 1/2. Related Articles | Metrics

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A review on thermal runaway behavior ofLithium-ion phosphate battery Gong Zihan, Zhou Xiaohui, Sun Junli, Wang Huaibin 2022, 41 (10):  1354-1357.  Abstract ( 1392 )   Abstract: The influence of internal angle configuration on downward fire spread characteristics of polyurethane insulation material (FPU) is analyzed by small-scale experimental research, and the influence of different angle configurations on typical characteristic parameters of fire spread of FPU insulation material is studied and discussed, including flame shape, mass loss rate, near-field temperature and fire spread rate. The results show that, under the constraint condition of the side wall, the burning degree of the sample when the angle is 30° is obviously higher than that of 150°; For the confined space formed by the internal angle configuration, the burning degree of FPU sample under the small angle configuration is greater than that under the large angle configuration. Influenced by the limiting effect of the side wall, the mass loss rate and fire spreading rate of FPU both decrease at first and then increase with the increase of the included angle. Due to the stretching effect of stack effect, there are two temperature peaks, and the first temperature peak is higher than the second. Related Articles | Metrics

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Experimental study on combustion risk analysis of outdoor multiple fires Wang Pengfei, Li Yi 2022, 41 (10):  1358-1361.  Abstract ( 1009 )   Abstract: The ultra-long submarine tunnel has a special structure, so smoke exhaust and air supply are the key factors restricting the development of the ultra-long submarine tunnel. Based on Yanda Undersea tunnel, a new scheme of smoke exhaust and air supply without shaft in the sea is designed. It adopts centrifugal air compressor to pressurize fire smoke into seawater at high speed, and provides additional air supply through compressed air. FDS was used to simulate 56 groups of working conditions with different smoke exhaust volume and air supplement volume. By analyzing smoke layer thickness, smoke spread length, smoke exhaust efficiency and evacuation environment, the optimal smoke exhaust air supplement scheme was found. The results show that when the exhaust volume is 140-180 m3/s, and the air supplement volume is 190-210 m3/s, respectively, accounting for 50% and 70% of the exhaust volume, the system has the best exhaust effect. Among them, the smoke exhaust system of 180 m3/s, 50% air supplement volume and 200 m3/s, 70% air supplement volume has the best smoke exhaust effect, and the latter is better than the former. In practical engineering application, it can be considered that the design smoke exhaust volume is 200 m3/s and air supply volume is 140 m3/s. Related Articles | Metrics

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Study on early fire evolution characteristics and detection technology of cable interlayer in power plant Zhu Hui, Zhu Yaoyao, Lu Zhen, 2022, 41 (10):  1362-1366.  Abstract ( 966 )   Abstract: China requires the systematic protection, utilization and inheritance of historical and cultural heritage in urban and rural construction, and the activation and utilization of historical and cultural blocks and traditional villages to form a batch of replicable and popularized experience. However, in recent years, related fire accidents occurred frequently, and fire hazard remediation and fire-fighting capacity improvement activities continue. This paper summarizes the relevant standards and specifications at home and abroad. In view of the current situation that the fire protection design is difficult to comply with the current fire protection specifications in the process of activation and utilization of historical and cultural blocks and traditional villages, this paper summarizes and abstracts the ideas of targeted fire protection design, and puts forward fire protection design strategies from three levels of region, architecture and monitoring management. Related Articles | Metrics

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Influence of annular opening parameters on harmful gas and dust migration in large space circular coal storage dome Hou Yaohua, Chen Chao, Zhou Yu, Li Sicheng 2022, 41 (10):  1367-1371.  Abstract ( 1025 )   Abstract: Simulation models were developed for an aircraft fire extinguishing system using Amesim software. The influence of the parameters such as the filling pressure, the temperature of the fire extinguishing agent, the roughness of the pipe, the diameter of the nozzle, and the diameter of the branch pipe of the pipeline were studied. It is found that under the filling mass of 5.34 kg of fire-extinguishing agent, the spray mass curves of fire-extinguishing agent under the filling pressure of 4, 5, and 6 MPa are similar. The lower the temperature of the extinguishing agent, the slower the spray rate. The spray time of -50 ℃ fire extinguishing agent is about 2.5 times that of -10 ℃. Roughness also has a significant effect on the amount of fire extinguishing agent sprayed. The lower the roughness, the faster the spray amount. The quality curve of fire extinguishing agent under the roughness of 0.13 mm and 0.20 mm is similar. The nozzle diameters of 16 mm, 17 mm and 18 mm have little effect on the overall fire extinguishing agent spray quality of the system, but the flow distribution between the nozzles will be affected by the change of the nozzle diameter. When the diameter combination of the long branch pipe connecting 3 nozzles and the short branch pipe connecting 2 nozzles is (16, 14 mm) and (20, 12 mm), the ratio of the amount of fire extinguishing agent sprayed from the two branch pipes is close to 1. Related Articles | Metrics

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Protective effect of towels on indoor fire smoke and its mechanism Lu Lihong, Zhang Longlong, Guo Xin, Shi Kezhen 2022, 41 (10):  1372-1375.  Abstract ( 1043 )   Abstract: In order to study the effect of blocking on the fire extinguishing efficiency of liquid nitrogen in utility tunnel, this paper carried out an experimental study on the effect of blocking state on the fire extinguishing efficiency of liquid nitrogen. The research shows that the oxygen barrier suffocation of liquid nitrogen plays a dominant role, and the existence of blockage accelerates the suffocation process, thereby improving the liquid nitrogen fire extinguishing efficiency of the utility tunnel. The effect of lower blocking on nitrogen injection fire extinguishing is stronger than that of upper blocking, and the fire extinguishing efficiency is increased by 50.7% and 30.4% respectively compared with no blocking. The closer the fire blocking is to the fire source, the greater the blocking rate, and the more significant the promotion effect of liquid nitrogen oxygen isolation and asphyxiation. When the fire blocking is far away from the fire source, the fire extinguishing efficiency is 35.2% lower than that when the distance is short; the fire extinguishing efficiency with a blocking rate of 75% is up to 44.4% higher than that of 25%. Therefore, selecting reasonable blocking measures and optimizing sealing methods can maximize the effect of liquid nitrogen fire extinguishing. Related Articles | Metrics

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Study on toxicity evaluation of fire effluents based on bench-scale and middle-scale smoke generation model Deng Xiaobing, Li Xili, Zhu Jian 2022, 41 (10):  1376-1379.  Abstract ( 946 )   Abstract: To improve the applicability of fiber optic sensors in building fire warning, this study conducts high temperature experiments on single-mode and multi-mode fiber optic sensors based on fire temperature rise curve, and analyzes their temperature sensing performance, and then selects the sensor whose temperature sensing performance suits building fire better. Based on the experimental data, a temperature rise error correction model was established to improve the temperature measurement accuracy. The results show that the multimode fiber optic sensor is much better than the single-mode fiber optic sensor in terms of temperature measurement stability, and has more correction value. The temperature rise error correction model built can lower the temperature measurement mean absolute error to 13.12 ℃. Using distributed optical fiber to draw high-precision building fire map has become the technical key of fire monitoring and early warning, evacuation and rescue, and structural collapse prediction. Related Articles | Metrics

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Experimental investigation on suppression of wheat starch explosion by 4A zeolite Guan Wenling, Wang Huoqin, Dong Chengjie, Wang Hongwei 2022, 41 (10):  1380-1083.  Abstract ( 943 )   Abstract: The current fire image recognition methods rely primarily on large datasets, which will cause unreliable detection results when training samples are insufficient. In response to the problem of generally lack of fire image samples, a large-scale fire image dataset containing various application scenarios based on fire detection algorithm development and evaluation needs is proposed. This paper trains and develops fire detection algorithms based on the fire image dataset, and verifies the completeness and effectiveness of the fire image dataset. Experiments on the fire image dataset established in this paper show that the universality and effectiveness of fire detection algorithms, the experimental results show that this fire image dataset provides a basic platform for the research of image-type fire detection algorithms. Related Articles | Metrics

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Application of machine learning in prediction of coal dust explosion sensitivity Lei Youxue 2022, 41 (10):  1384-1389.  Abstract ( 934 )   Abstract: This article presented a full-scale UHVDC converter transformer fire model, which was developed on account of the characteristics of special fire accidents such as high-temperature oils and explosion shock of converter transformers, and the performance of the compressed air foam spraying system in firefighting was validated by carrying out the spill fire test. Due to the absence of fire branch pipes and sprinklers, the compressed air foam sprinkler system will not fail in blast shock. Under the application rate of 12.4 L/(min·m2), the fire was controlled at 28 s and extinguished at 181 s. During the fire test, re-ignition occurred first on the top fuel tank due to the higher temperature of the fuel in the top fuel tank. In addition, the fire plume tended to the direction of the valve hall firewall, and the "fireproof foam curtain" had the effect of thermal radiation protection, resulting in higher temperature of the valve hall firewall. Related Articles | Metrics

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Fire resistance of assembled subway station under post earthquake fire Cai Xinjiang, Li Xiaojie, Mao Xiaoyong, Tian Shizhu, 2022, 41 (10):  1390-1395.  Abstract ( 937 )   Abstract: The injection of high-pressure fluoropropanegas in a small hole of an enclosed chamber was modeled investigate their detail behaviors, which was compared with the corresponding experimental measurements. Based on the numerical simulations, the concentration, temperature and velocity during the injection of high-pressure fluoropropane were analyzed. The simulated results indicated that a flowback of the fluoropropane gas was shown near an obstacle, which resulted in the low concentration at the other side of the obstacle. The experimental measurements showed that the lowest temperature at the nozzle was as cold as -20 ℃ during the accidental leakage of high-pressure fluoropropane. However, the temperature decrease near the electrical equipment is acceptable if they are more than 1.75 m away from the leakage orifice. Related Articles | Metrics

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Study on lateral point smoke exhaust efficiency in double-deck shield road tunnel Yu Pei, Yuan Jianping, Fang Zheng, Tang Zhi 2022, 41 (10):  1396-1400.  Abstract ( 970 )   Abstract: Fluent software was used and the Euler multiphase flow model was used to simulate the along-path resistance, flow velocity and dry powder concentration distribution characteristics of ultra-fine dry powder fire extinguishing agent with a particle size of 18 μm sprayed in a horizontal straight pipe with a diameter of 8 cm. The results show that in the range of flow velocity 25~150 m/s and ultrafine dry powder volume fraction 5%~15%, the resistance along the horizontal straight pipe has a quadratic function relationship with the flow velocity, and a linear function relationship with the dry powder volume fraction. The range of resistance value is 0.003 28~0.259 81 MPa/m. Affected by the friction of the pipe wall, the flow velocity of the two-phase flow on the cross section of the pipe presents a distribution characteristic of fast in the middle and slow in the surrounding area, and the effect of the volume fraction of solid particles on the flow velocity can be ignored. The gas-phase drag force generated by the different velocity distributions on the cross-section leads to the annular distribution of the ultrafine dry powder volume fraction. The gas-phase drag force is related to the initial velocity and has nothing to do with the dry powder volume fraction. When the flow rate is lower than 70 m/s, the ultra-fine dry powder is distributed in a crescent shape, and the volume fraction of the ultra-fine dry powder is the highest at the lower part of the pipeline close to the pipe wall. The volume fraction is the lowest near the pipe wall, and the flow velocity is greater than 70 m/s, which can effectively inhibit the sedimentation of ultra-fine dry powder. Related Articles | Metrics

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Experimental study on the influence of internal angle configuration on fire spread of polyurethane insulation material Li Yibo, Wan Lulu 2022, 41 (10):  1401-1404.  Abstract ( 896 )   Abstract: Aiming at the fire accidents caused by overload, short circuit and equipment aging of indoor power transformer, the mechanism of transformer fire heat radiation and toxic gas diffusion is studied, and the effective method of power transformer fire suppression is sought. Taking 10 kV oil immersed power transformer as an example, a fire test platform was built to simulate the early fire scene of indoor power transformer. The gas concentrations of CO, NO, SO2 and O2 before and after the fire were collected. According to the test data, we analyzed the variation law of temperature and thermal radiation at different locations of the fire scene, and used perfluorohexanone fire extinguishing agent to suppress the fire of transformer at last. The test results show that perfluorohexanone extinguishing agent has fast fire extinguishing speed and has obvious effect of heat absorption and cooling. The cooling rate can reach 80 ℃/min. This test is not destructive to the electrical equipment of transformer in the fire of indoor power transformer. It realizes the controllability of indoor transformer fire and the improvement of fire extinguishing efficiency. It is a new idea for the research on fire suppression of power transmission and transformation system equipment. Related Articles | Metrics

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Optimization of smoke exhaust and air supply without shaft in ultra-long submarine tunnel Li Yu, Guo Xinxin, Pan Ke 2022, 41 (10):  1405-1408.  Abstract ( 1002 )   Abstract: With the global climate change, especially the obvious warming trend and the increase of human disturbance activities, the possibility of disastrous forest fires in the main distribution areas of the world's forests continues to increase. This paper introduces the concept of disastrous forest fires at home and abroad, and compares the research contents and main research methods of disastrous forest fires. The results show that the pattern and scale of existing disastrous forest fire research are small, mainly focusing on the occurrence and development of summer forest fires, and less research on the mechanism of major forest fires in higher altitude mountain forests. Future research should integrate remote sensing and geographic information system and other large-scale methods, focuses on long-term and dynamic study on the vegetation and weather characteristics of disastrous forest fires in large and mesoscale patterns. In-depth research should be carried out on the fire behavior, fire loss and long-term effects of disastrous forest fires, so as to provide the basis for forest fire prevention and control. Related Articles | Metrics

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Research on fire protection design of activation and utilization of historical and cultural blocks and traditional villages Zhuo Ping, Guo Wei, Lu Shichang, 2022, 41 (10):  1409-1413.  Abstract ( 1001 )   Abstract: The study on the combustibility of tree species is the basis of forest fuel treatments. The cone calorimeter was used to measure the combustibility of dead branch of 2~4 mm, 5~8 mm and 9~12 mm diameters of 9 tree species and Eupatorium adenophorum in central Yunnan. The single combustibility was analyzed, and the results were as follows: Time to ignition, combustion duration, time to peak heat release rate and time to peak effective heat combustion increase with the increase of the diameter of branches. Peak heat release rate and peak mass loss rate of every tree species decrease with the increase of branch diameter. When the diameter of branch was smaller, peak heat release rate and peak mass loss rate were more obvious, and with the increase of diameter, peak heat release rate and peak mass loss rate became less obvious. Peak effective heat combustion and peak specific extinction area have little correlation with the diameter of dead branches. Time to peak mass loss rate of different tree species increases with the increase of branch diameter. Time to peak specific extinction area of Eucalyptus robusta decreases with the increase of branch diameter，but other tree species increases with the increase of branch diameter. Compared with 9 tree species, the time to ignition, duration of combustion, time to peak heat release rate, time to peak effective heat combustion, time to peak mass loss rate and time to peak specific extinction area of Eupatorium adenophorum are the lowest，and it is easy to burn and to lead to crown fire. The peak heat release rate of Sabina chinensis and Cupressus torulosa were high, while the ignition time and peak heat release rate of Pinus armandii and Pinus yunnanensis were small. These 4 tree species have high flammability and are easy to cause continuous crown fire, and the fire intensity is large and easy to cause large losses. In the process of forest fuel treatments, the dead branches, especially those with small diameter, should be cleaned up in time. Related Articles | Metrics

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Simulation of Halon 1301 flow in aircraft fire extinguishing pipes Xuan Yang, Yuan Changyu, Lu Song 2022, 41 (10):  1414-1418.  Abstract ( 943 )   Abstract: In order to systematically grasp the research progress in the field of non-coal dust explosion suppression, China Knowledge Network (CNKI) was used as the data source to analyze the digital characteristics of 108 documents in the field of non-coal dust explosion suppression using the bibliometric method, and the VOSviewer software was used to draw the knowledge map to explore the research evolution, hot spots and frontiers. The results show that: The number of research papers in the field of non-coal dust explosion suppression shows a trend of steady growth, and the research process can be divided into three stages; The selected 108 papers mainly focus on safety science and disaster prevention, mining engineering, organic chemical engineering and other disciplines; The research focuses mainly on combustible dust explosion, detonation suppressor, detonation suppression system, detonation characteristics and suppression mechanism, etc. It is the trend that the research in this field changes from the study of macroscopic measures to the study of microcosmic mechanism. Related Articles | Metrics

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Research on the effect of blocking state on the fire-extinguishing efficiency of liquid nitrogen in utility tunnel Jia Boyan, Zhang Peng, Wei Liqiang, Su Jingang 2022, 41 (10):  1419-1424.  Abstract ( 930 )   Abstract: In review of the collected data on fire and rescue in Guangdong Province between 2016 to 2021, this research studied statistical change trend, characteristics of regional distribution, various category distribution, and the distribution of alarm time. An analysis model was developed using spatial analysis method. Based on 3 factors, including the current urban construction land usage, data on fire and rescue frequencies and urban development?boundary, analysis on the optimizing of fire and rescue station planning layout was conducted, which provides valuable statistical evidence to support the development of the designated fire and rescue station. Practical implications and recommendations on future fire and rescue services are presented based on statistical analysis and conclusions. Related Articles | Metrics

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Analysis and correction of temperature sensing performance of optical fiber sensor Wang Lan, Meng Hongrong, Qu Guanhua, Ren Lei, 2022, 41 (10):  1425-1429.  Abstract ( 932 )   Abstract: Based on the current emergencies in the field of firefighting and rescue, an intelligent matching algorithm for firefighting and rescue expertise is proposed. The algorithm calculates the semantic relationship between case description and firefighting knowledge based on natural language processing and attention mechanism, realizing the matching of related firefighting and rescue knowledge. First learn semantic information at sentence granularity level based on natural language processing, then learns semantic information at word granularity level based on the attention mechanism, and finally, based on the interaction of two levels of semantic information, the relationship between sentences is inferred based on the local differences of the information. Experimental results show that the algorithm has excellent performance. At the same time, it can understand sentences more accurately from the two granularities of words and sentences, realize intelligent matching of firefighting and rescue professional knowledge based on case descriptions. Related Articles | Metrics

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Establish a large-scale fire image dataset Li Pu, Zhang Miao, Yang Yi 2022, 41 (10):  1430-1434.  Abstract ( 1101 )   Abstract: Lithium iron phosphate(LiFePO4) batteries has advantages such as low risk, low cost, smooth discharge voltage and long life. It is especially suitable for large, high-power Lithium-ion battery systems. However, reports of thermal runaway accidents according to LiFePO4 batteries have gradually increased in recent years. The safety of LiFePO4 batteries has become a focus of attention. This paper presents an analytical review of LiFePO4 battery thermal runaway mechanism, material thermal stability and thermal behaviour during the runaway process, hoping to raise awareness of the safety of LiFePO4 batteries. The improvement of its safety performance is prospected. Related Articles | Metrics

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Experimental study on extinguishing full-level oil spill fire of UHVDC converter transformer by compressed air foam Chen Tao, Zhang Jiaqing, Jing Lishuai, Hong Qingquan 2022, 41 (10):  1435-1439.  Abstract ( 950 )   Abstract: The combustion experiments of outdoor multiple fires and single pool fire were carried out under different pool diameter (1.0, 1.4, 1.7 m) and different pool spacing (1.5D, 1.75D, 2D). In the experiment, camera, electronic balance andthermocouples were used to monitor the flame height, the burning rate and the flame temperature respectively. Results show that the burning rate of each fire in the multiple-fire experiments is higher than that of a single pool fire with the same diameter, and when the flame mergence occurs at the distance of 1.5D, the merging flame height is higher than single pool fire flame height with the same diameter, indicating that the combustion risk of multiple-fire is greater. In addition, after the four flames mergence, the exponential changes of flame temperature at the geometric central axis with height are 0.13, [-1.02] and [-1.46], which is basically consistent with the recognized central axis temperature change of common buoyant pool fire, which indicates that multiple flames merge into a common buoyant pool fire. Related Articles | Metrics

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Study of injection characteristics of high-pressure fluoropropane and local damage by sudden cooling in enclosed room Yuan Yanhua, Lu Qizhao, Xie Qiyuan 2022, 41 (10):  1440-1444.  Abstract ( 990 )   Abstract: The early (smoldering and initial) fire detection experiments of cable interlayer are carried out through the full-scale cable interlayer experimental platform. The temperature field and CO gas propagation characteristics are studied. Based on the combination of experimental research and numerical simulation, the effectiveness of point-type temperature detector, point-type smoke detector, cable-type temperature detector, and suction-type smoke detector with different response time thresholds is analyzed. The results show that: The temperature field attenuation of smoldering and initial fire presents an exponential function. The average velocity of CO gas propagation in smoldering fire is basically the same when the distance from the fire source increases, but decreases with the increase of the distance from the fire source in the initial fire. The alarm time of cable-type temperature detector is 69% earlier than that of suction-type smoke detector, and 82% earlier than that of point-type smoke detector. Compared with smoldering fire, the initial fire response time of each detector is 56% earlier on average. Under the condition of smoldering fire, the point-type temperature detector fails to report. The response time of fire detector with high alarm threshold is 10% ~ 20% later than that of low threshold detector. Related Articles | Metrics

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Research on flow characteristics of ultra-fine dry powder gas-solid two-phase flow in horizontal straight pipe Ji Jingwei, Cai Weiming, Tian Zhijian, Kou Jiang, 2022, 41 (10):  1445-1450.  Abstract ( 953 )   Abstract: According to the ventilation safety theory and the CFD method based on the component transport model, the ventilation safety characteristics and appropriate performance evaluation indices of the circular coal dome are discussed. Taking the circular coal dome with a diameter of 100 m as an example, the effects of the opening mode, position and geometric size of the circular vent on the distribution, transport characteristics and removal efficiency of coal dust and gas are studied, and the optimal vent design parameters are obtained. The research results show that in the case of single annular opening, the vent is changed from horizontal to lateral, which can improve the internal environment and improve the removal efficiency of pulverized coal dust and harmful gas. The recommended height of the lateral annular vent is 2 m. Adding an annular opening in the middle of the dome can effectively reduce the concentration of suspended pollutants at the height of 30-35 m above the coal dome. The optimal positions of the double ring openings are 15 and 31 m respectively, which can make the dust mass concentration in most areas of the coal dome lower than 10 mg/m3; The mass concentration of CO2 gas is lower than 30 mg/m3; The highest sewage discharge efficiency is nearly 80%. The research results can provide reference for ventilation safety design of super large space circular coal dome. Related Articles | Metrics

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Experimental study on fire extinguishing of Perfluorohexanone in 10 kV indoor transformer fire Liu Guoqiang, Li Guochun, Hao Yanan, Xue Ying 2022, 41 (10):  1451-1454.  Abstract ( 982 )   Abstract: In order to study the filtering effect and protective mechanism of different towels on indoor fire smoke, a thermal decomposition and smoke production platform with protective testing function was built. PVC materials was used as smoke-producing materials because it is widely used in interior decoration. The 3 common materials of cotton, gauze and microfiber towels on the market were selected to study the protective filtering effects of different towels on PVC fire smoke in wet and dry conditions respectively. And the protection and filtration mechanism of the wet and dry towels for the indoor fire smoke was analyzed combining with the surface morphology of the towels before and after the smoke filtration. The result shows that, 3 kinds of towels have certain protective and filtering effect on PVC material fire smoke. No matter in dry or wet state, the 3 kinds of towels have the same degree of pros and cons for the protection and filtering effect of smoke, i.e. pure cotton towel ＞gauze towel ＞microfiber towel. The protective filtering effect of wet towel on CO, NOx and HCl gas is better than that of dry towel. Compared with dry towels, the protective filtering effect of wet towels on CO gas and HCl gas is greatly improved, and the protective filtering effect of HCl gas is nearly doubled. Related Articles | Metrics

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Research progress of major forest fires at home and abroad Wang Qiuhua, Wang Jin, Wang Yarong, Xing Fuji 2022, 41 (10):  1455-1459.  Abstract ( 1336 )   Abstract: Bench-scale dynamic tube furnace experiment and middle-scale single burning item experiment within the current burning behavior classification framework were used as the smoke generation model, typical flame retardant and non-flame retardant materials were selected to carry out the experiments mentioned above, gas analysis technology such as FTIR was used to measure the gas composition data in real time, calculation model such as effective dose fraction (FED) was used to quantify the fire effluents toxicity. The results show that the FED1 of smoke generated from dynamic tubular furnace is about 4 - 17 times as much as the FED3max of smoke from the single burning item experiment , the FED values obtained from the single combustion experiment of flame-retardant materials are usually less than 0.15, while the FED values obtained from easily-flammable materials are as high as 0.65; Based on the bench-scale dynamic tubular furnace and the single burning item experiment as the smoke generation model, the toxic component calculation models FED1 and FED3 should be used to make a representative, effective and convenient evaluation of the smoke toxicity of materials in the non-flaming stage (oxidation pyrolysis) and the well ventilated flaming fire stage. Related Articles | Metrics

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Study on the single combustibility of main tree species in central Yunnan Zhang Yunsheng, Shu Lifu, Zhai Chunjie, Liu Kezhen 2022, 41 (10):  1460-1463.  Abstract ( 946 )   Abstract: In order to study suppression effect of 4A zeolite on dust explosion of wheat starch, based on the optimum mass concentration of wheat starch, experiments of mixed dust explosion of wheat starch/4A zeolite were conducted by using closed Siwek 20-L sphere, and the variation law of pmax and (dp/dt)max of mixed dust with the increase of the mass of 4A zeolite was analyzed. The experimental results show that 4A zeolite can reduce the explosion intensity of wheat starch and inhibit the propagation of explosion flame.In 10 g of wheat starch, the addition of 4A zeolite can continuously reduce (dp/dt)max of wheat starch, and when its mass fraction is over 9.09%, it can greatly reduce pmax of wheat starch and mixed dust cannot explode. 4A zeolite can weaken dust explosion of wheat starch, and inhibit the propagation of explosion flame through physical and chemical suppression effect, including heat absorption, dilution and free radical adsorption. Related Articles | Metrics

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Bibliometric analysis in the field of non-coal dust explosion suppression Lu Jifeng1,2，Li Fang2,3，Liu Jiqing3 2022, 41 (10):  1464-1467.  Abstract ( 898 )   Abstract: To investigate the feasibility of machine learning in predicting the minimum ignition temperature of pulverized coal clouds, based on the minimum ignition temperature (MITc) of coal dust clouds and the influence factors obtained from previous tests using Godbert-Greenwal furnace, analyzed the correlation of the influence factors. The prediction effectiveness of the three machine learning models in terms of both the minimum ignition temperature of coal dust clouds and the incidence of ignition was evaluated and analysed using the AUC/ROC, Kappa coefficient, sensitivity, specificity, MAE and RMSE metrics. The results showed that the RSM model has the worst prediction effect; the RF model has the best accuracy and stability in predicting the MITc and ignition probability of pulverized coal clouds, and with the Bagging model, the AUC values are greater than 0.85 in predicting the ignition incidence, but the effect of predicting MITc is poor. The results provide a new research idea on prediction of coal dust cloud ignition sensitivity. Related Articles | Metrics

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Research on optimizing the planning layout of fire and rescue station based on analysis of fire and rescue data Wu Hejun 2022, 41 (10):  1468-1471.  Abstract ( 985 )   Abstract: Prefabrication and assembly is an important development direction of subway station, and the research on its post-earthquake fire performance is relatively few at present. In this paper, the three-dimensional finite element model of single-layer double span assembled subway station is established. The deformation of the station under three working conditions of earthquake, fire and fire after earthquake is compared and analyzed by using the far boundary and HC standard temperature rise curve and considering the location of fire source. The results show that the subway station is damaged in "M" shape under earthquake, and the center column of subway station is bent and deformed under fire and post-earthquake fire; under the action of fire, compared with the roof and side wall, the temperature rise of the middle column is the fastest. When a single span is under fire, the relative displacement between the top and bottom of the middle column increases rapidly and then tends to be stable. When a full span is under fire, the deformation of the middle column initially develops slowly and then increases suddenly; the deflection development trend of roof under single fire and post-earthquake fire is similar, and the initial deformation development of side wall is similar; the development law of internal force response under separate fire is similar to that after earthquake. Considering the earthquake damage, the internal force of each component changes more obviously. Related Articles | Metrics

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Intelligent matching algorithm for firefighting and rescue professional knowledge Zhang Yi 2022, 41 (10):  1472-1476.  Abstract ( 957 )   Abstract: The FDS was used to simulate the lateral point smoke exhaust system in a double-deck shield road tunnel, and the influence of smoke outlet area, space, smoke outlet opening scheme and longitudinal ventilation on the smoke exhaust system is studied. The results show that without longitudinal ventilation, the area within 3 m2 to 5 m2 and space between 60 m and 100 m of smoke outlets have little effect on the effectiveness of smoke exhaust after the fire has stabilized. As the longitudinal ventilation velocity increases and more upstream smoke outlets opens, the smoke exhaust efficiency decreases significantly. The smoke exhaust efficiency for the upper and lower exhaust outlets of the double-deck tunnel is basically the same, and the total smoke exhaust efficiency of the lower tunnel is slightly higher than that of the upper tunnel. It is proposed that in the event of a 20 MW fire in this double-decker tunnel, smoke exhaust is most effective when the longitudinal ventilation velocity is 2 m/s, the smoke outlet space is 60 m, the smoke outlet area is 4 m2, and two upstream and four downstream smoke outlets are opened. Related Articles | Metrics