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15 February 2024, Volume 43 Issue 2 Previous Issue    Next Issue

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Research on gas emergency assistance decision-making by integrating knowledge graph and case-based reasoning Hu Yuling, Wan Yurui, Li Zixuan, Qi Zichen 2024, 43 (2):  143-148.  Abstract ( 312 )   A gas emergency decision-making method that integrates knowledge graph and case-based reasoning is proposed to address the difficulty of emergency response personnel searching for emergency response plans based on text data to meet the needs of scientific and rapid response in the current occurrence of gas accidents. Store and represent existing text data of gas accident cases in the form of a knowledge graph, propose a weighted calculation method for attribute similarity and relationship similarity in case reasoning, and based on the comprehensive similarity between the accident target case and the source case, retrieve the best similar source case as an important reference for emergency response decisions of on-site disposal personnel. Store new cases and disposal measures in the gas emergency response knowledge graph database, updated knowledge on implementation of disposal measures. The rationality and effectiveness of our method were verified through experiments such as case similarity weight allocation, attribute weight allocation, selection of attribute similarity methods, and case validation. Related Articles | Metrics

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Flame characteristics of n-heptane in slope glide with different angles Li Longji, Huang Xin 2024, 43 (2):  149-155.  Abstract ( 562 )   In order to study the variation trend of n?heptane flame shape, flame brightness and flame temperature over time, the combustion experiments of n?heptane were carried out with the inclined plane devices of 25° and 40° respectively. The results show that under the two inclined planes, the inertia of the hot and cold air in the box is different due to the different density, which causes the uneven temperature distribution inside the box to produce pressure difference, and the flame tilts to the slide direction of the box under the action of pressure difference. Under the comprehensive influence of vertical and horizontal acceleration, the length, inclination and height of the flame are shortened, but the brightness is enhanced, and the increasing inclination of the inclined plane will have a greater impact on its shape and brightness. The flame shape parameter values at 40° inclined plane are 6.21%, 12.30% and 6.72% lower than those at 25° inclined plane, respectively. However, the flame brightness is 31.98% higher than that of 25° inclined plane. In addition, the temperature of the n?heptane flame decreased due to instability during the sliding process, and the flame temperature at 40° and 25° inclined plane decreased by 16.05% and 22.22%, respectively. However, the flame temperature at 40° inclined plane is higher than that at 25° inclined plane, which is related to the weakening of buoyancy effect caused by the decrease of vertical acceleration. Related Articles | Metrics

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Experimental study on the thermal runaway characteristics of 32650 lithium iron phosphate battery pack inhibited by liquid nitrogen Zhang Yuanyuan, Zhang Zhiwei, Zhao Ziming, Zhang Guowei 2024, 43 (2):  156-160.  Abstract ( 490 )   This study started from the thermal runaway hazard characteristics of lithium iron phosphate battery packs, experimentally study the thermal runaway characteristics of the 32650 LiFePO4 battery and its thermal runaway propagation process between battery packs. Explore the use of liquid nitrogen spraying to extinguish the thermal runaway propagation between battery packs, and analyze the fire prevention and extinguishing effectiveness of liquid nitrogen on lithium?ion batteries. The experimental results show that the thermal runaway stage of monomer lithium battery can be divided into five stages: passive heating stage, initial explosion stage, self?reaction stage, explosion stage and negative combustion stage. The temperature change curve of monomer battery is inverted "V" shape. Liquid nitrogen can effectively extinguish the thermal runaway propagation between battery packs and greatly reduce the peak temperature of the explosive battery. And the longer the spraying time, the more obvious to prevent the spread of thermal runaway battery group. With 30 s liquid nitrogen spraying, except for battery A1, no safety value pressure relief occured in other batteries. Related Articles | Metrics

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Experimental study on the combustion characteristics of small size oil pool fires in confined spaces in high plateaus Dai Shangpei, Jia Xuhong, Ding Sijie, Zhu Xinhua, 2024, 43 (2):  161-167.  Abstract ( 394 )   To study the combustion characteristics of small?scale oil pool fires of liquid fuels in confined spaces in high plateau areas of China, a test platform for oil pool fires in confined spaces was built under high plateau conditions at Kangding Airport. Three types of typical liquid fuels (aviation paraffin, aviation gasoline and n-heptane) were selected for combustion tests, and the changes in flame height, flame temperature and smoke composition were measured to study the behaviour of small?scale oil pool fires in confined spaces on high plateaus. The results show that: the average flame height model for the stable stage of n-heptane in the plateau region is derived: L/D=k+0.254Q(2/5)/D , the relationship between flame height and pressure is L/D~p(-2/9); the maximum flame temperature of all three fuels exceeds 600 ℃, the plume axis temperature rise and flame height is -5/3 exponential relationship; the ambient pressure dependence of smoke production rate is:v~p(-1/3). Related Articles | Metrics

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Study on maintenance frequency of coal chemical fire protection system based on Bayesian network analysis Wang Jun, , Fang Zheng, Xing Wang, Yu Shujian 2024, 43 (2):  168-172.  Abstract ( 102 )   Due to inadequate maintenance, the system can't function or even be paralyzed frequently. In this paper, the risk assessment method based on Bayesian network is used to analyze the causes of fire in coal gasification plant, and the risk assessment of syngas leakage and accident consequences is carried out. Combined with risk assessment, the maintenance frequency of fire fighting system is studied, and an evaluation algorithm determining the maintenance cycle of firefighting system suitable for the inherent risks of coal gasification plant is proposed, which can realize accident prevention and reduce disaster losses to a high degree. Related Articles | Metrics

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Explosion numerical simulation analysis of high⁃voltage oil⁃immersed transformer in offshore platform Sang Jun, Feng Yuan, Zhou Xingang 2024, 43 (2):  173-176.  Abstract ( 106 )   Power transformer is an important hub equipment in offshore platform, once the explosion occurs, it will seriously affect the normal production and operation of the platform, causing significant economic losses. Therefore, it is very important to ensure the transformer’s safe and reliable operation of the offshore platform. This paper takes the high voltage oil-immersed transformer of the first co construction offshore oil and gas platform in Asia as an example, FLACS software is used to model the platform in 3D, and the whole process of the primary explosion and secondary explosion is simulated. According to the calculation results, the maximum explosion over-pressure of the indoor room of the transformer is 0.073 MPa, and the maximum explosion over-pressure of the transformer door is 0.071 MPa, which may have some influence on the production facilities of the platform. In order to reduce the indoor explosion over-pressure, the paper optimizes the original design scheme by adding the explosion discharge area in the oil?immersed transformers rooms. According to the numerical simulation analysis, the explosion over-pressure is significantly reduced, which drops to 0.014 8 MPa. To further improve the overall safety performance of the offshore platform, the anti?explosion is designed, with the anti-explosion load of 0.015 MPa, which greatly reduced the impact of the explosion over-pressure on the surrounding oil and gas facilities. Related Articles | Metrics

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Experimental study on fire⁃resistance performance of full⁃scale load⁃bearing cross⁃laminated timber floors Peng Lei, Qiu Peifang, Ou Jiajia 2024, 43 (2):  177-182.  Abstract ( 595 )   Experimental tests were carried out to study the fire?resistance performance of cross?laminated timber floors with full?scale size in load?bearing conditions. The tested floor specimens were 175 mm in thickness, and loaded with averagely?distributed weight of 2.0 kN/m2. The two tested floors were made using heat?resistant PUR adhesive and ordinary PUR adhesive, and protected with one?layer of 15 mm?thick fire?resistant gypsum board and two?layers of 12 mm?thick fire?resistant gypsum boards. Test results show that, for the floor specimen using heat?resistant PUR adhesive and protected with one?layer of 15 mm?thick fire?resistant gypsum board, the gypsum board fell off at about 45~55 min, and no obvious char layer delamination was observed. For the floor using ordinary PUR adhesive and protected with two?layers of 12 mm?thick fire?resistant gypsum boards, the 1st layer of gypsum board fell off at about 30 min, and the 2nd layer fell off at about 60 min, and the char layer delaminated at about 85~110 minutes. At 121 minutes, the vertical displacements at the center of floor specimens were about -25 mm and -33 mm, respectively. The unexposed sides of the floors showed intact, and the temperature rise on the unexposed sides were less than 2 ℃ for the both specimens. The final results show that the fire resistance rating of two tested floors is not less than 2.00 h. Related Articles | Metrics

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Research and improvement of fire detection method for historical buildings based on FireNet Chen Qingdian, Zhong Chen, Liu Hui, Wang Xiaohui 2024, 43 (2):  183-188.  Abstract ( 131 )   In response to the need for fast, accurate, and real-time fire detection of historical buildings, this paper builds a dataset specifically for historical building fire detection, which is used for deep learning in historical building fire detection for the first time. By fusing the CBAM attention mechanism and combining it with multi-scale feature fusion, we improve and propose the FireNet-AMF network based on the FireNet network. The fire detection capability of the FireNet-AMF network is verified on the FireNet dataset and the historical building fire detection dataset. The FireNet-AMF network achieves an accuracy of 95.08% for fire detection with the FireNet dataset, an improvement of 1.17% compared to the FireNet network, and an accuracy of 95.62% for experiments on the historical building fire detection dataset we built, which is an improvement of 1.62% compared to the FireNet network. The network ensures a light weight while guaranteeing a high level of historical building fire detection accuracy. Related Articles | Metrics

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Study on the smoke control performance and smoke exhaust efficiency of the point extraction system in tunnel fires Shen Zhewei, Guo Qinghua, Li Xingli 2024, 43 (2):  189-196.  Abstract ( 128 )   Numerical simulation was implemented to study the smoke spread distance, temperature distribution, smoke exhaust velocity and exhaust efficiency by considering the variation of the heat release rate（HRR）, interval of the adjacent exhaust vents, exhaust volume, exhaust vent dimension and tunnel height. The results indicate that the under a given HRR fire?induced smoke spread distance in the point extraction system is shortened as the smoke extraction volume increases, and the ceiling gas temperatures decrease. Besides, under a certain smoke extraction volume, a larger aspect ratio of the smoke vent can control the smoke within a shorter distance. It is also found that the interval of adjacent vent has slight effect on the smoke exhaust efficiency. Based on the results obtained in this work, the suggested values of the smoke exhaust volume and arrangement of the exhaust vent for the fire of 5 MW and 20 MW are given. Related Articles | Metrics

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Analysis of evacuation behavior tendency of people in open public places Hu Cheng, Liu Shaohua, Mao Tianlu 2024, 43 (2):  197-202.  Abstract ( 96 )   The risk of crowd gathering in open public places is prominent, and conventional evacuation measures cannot effectively alleviate the risk situation of crowd gathering inside and outside the place. It is of great significance to master the characteristics of evacuation behavior of people in emergencies. Shenzhen Dongmen Pedestrian Street was selected as the research area to carry out a questionnaire survey on evacuation behavior, and three evacuation behavior tendency scenarios were developed according to the crowd gathering state, namely, obedience of personnel, gathering congestion response and emergency evacuation response. SPSS 25.0 Chi?square test was used to analyze the correlation between basic characteristics such as gender, age，group and evacuation behavior tendency. The results show that: （1） there are old and young groups, carrying packages and low environmental familiarity in pedestrian street, which affect evacuation efficiency. （2） a small number of people may continue to stay and take photos, wait for a long time, watch after encountering gathering congestion, or watch or even return after being evacuated to a safe area, which may lead to the internal gathering of the site can not be effectively alleviated, and form a new risk point of crowd gathering in the periphery. （3） the three groups of "male, large group and short?term tourists" have poor evacuation behavior, and the proportion of gathering, staying and returning is higher, especially the large group with 4 or more people are more likely to take the harmful behavior of crowding forward. Related Articles | Metrics

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Study on fire propagation characteristics of gas film reinforced concrete structure grain silo Ma Chunbao, Xue Fei, Zhang Wenhua, Liu Zhenfei 2024, 43 (2):  203-209.  Abstract ( 384 )   The gas film reinforced concrete structure dome grain silo （hereinafter referred to as "gas film grain silo"） has been applied in China due to its advantages of high safety, strong airtightness, good thermal insulation, and energy conservation and environmental protection. However, there is no consensus on the fire safety and reliability research of gas film granaries. Therefore, this study constructed a simulated fire scenario to analyze the possibility and causes of fire in an gas film grain silo, and studied the characteristics of fire spread on the outer wall of the silo. The experimental results indicate that the outer PVDF layer and polyurethane insulation layer of the gas film granary can be ignited and spread by a fire source. The maximum heat flux at a distance of 2.5 meters from the wall is less than 1.0 kW/m2, which does not reach the heat flux required to ignite ordinary combustibles. In addition, the temperature 2.5 m away from the wall does not exceed 100 ℃, and does not reach the ignition temperature of 270 ℃ for flexible polyurethane foam. Considering a certain safety margin, it is recommended that the fire separation distance should not be less than 3.0 meters. At the same time, this article also proposes fire protection measures suitable for gas film granaries. Related Articles | Metrics

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Research on the effect of water⁃based fire detection tubes fire suppression technology on extinguishing lithium⁃ion battery fire Chen Xiaoyu, Wang Xiao, Wang Tao, Li Le 2024, 43 (2):  210-216.  Abstract ( 357 )   In order to quickly extinguish lithium?ion battery fires in the early stage, based on the fire detection tube material, water was selected as the extinguishing agent and a small fire extinguishing system of water based fire detection tube was set up. The effectiveness of the fire detection tube material in extinguishing lithium?ion battery fires was studied, and lithium?ion battery fire suppression experiments were conducted under different water consumption and driving pressure. The results show that the fire detection tube material can respond quickly after the battery thermal runaway is triggered, release extinguishing agents, suppress the gas production and combustion of the battery thermal runaway, and quickly cool the battery; The cooling capacity of the system is positively correlated with water consumption. As the water consumption increases, the maximum surface temperature and duration of high temperature of the battery greatly decrease. When the water consumption was 100 mL, a pressure of 0.5 MPa failed to ensure timely response of the system, resulting in an open flame in the battery after thermal runaway; As the driving pressure gradually increases, the droplets released by the system exhibit a significant sputtering phenomenon, which has a negative impact on the cooling efficiency of the system. When the driving pressure is 1 MPa, the cooling performance of the system is optimal. For fires caused by thermal runaway of battery modules, the fire detection tube material can quickly respond, release extinguishing agents to extinguish initial battery fires, and prevent the spread of thermal runaway of battery modules. Related Articles | Metrics

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Simulation test research on failure condition of automatic sprinkler system Tian Liwei, Chen Hongguang, Liu Lianxi, Li Yi, Liu Xin, 2024, 43 (2):  217-220.  Abstract ( 92 )   Through experimental methods, obtain the actual performance of automatic sprinkler fire extinguishing systems under three simulated failure conditions, analyze and compare the expected fire extinguishing effectiveness under the system design conditions, and summarize the impact of different failure conditions on fire extinguishing effectiveness. The experimental results show：the sprinkler deflector failure will cause uneven water distribution and less effective control of early stage fire, so that the number of actuated sprinklers will increase to meet the fire control requirements, and the failure can result in about 40% reduction in fire extinguishing efficiency. The malfunction of the thermal sensitive element will lead to higher sprinkler operation temperature and longer response time, during which the fire develops too rapidly to be effectively controlled in the short term after the sprinkler actuation, and the malfunction can result in about 25% reduction in fire extinguishing efficiency. Furthermore insufficient working pressure will cause the most serious impact , which reduces the fire extinguishing efficiency by about 60%. Related Articles | Metrics

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Influence of secondary pressurization on the powder spraying effect of heavy-duty powder elevating fire trucks Xiao Qiaowei, Wan Litian, Zhang Jing, Yan Long 2024, 43 (2):  221-226.  Abstract ( 64 )   In view of the problem of insufficient powder spraying distance of heavy-duty powder fire trucks, it is proposed to use secondary pressurization to improve the spraying distance of heavy-duty powder, and the influence of the position of secondary pressurization, the number of pressurized ports and the pressure on the spraying effect of powder in fire trucks is analyzed through theoretical analysis, numerical simulation and experimental study. Research indicates that, compared with directly raising the pressure of the main driving gas source, the secondary pressurization through the transportation pipeline can more effectively reduce the pressure loss of gas-solid two-phase flow to enhance the exit velocity and range of the powder. The position of the pressurized port has a greater impact on the powder injection range, and the powder injection effect of secondary pressurization in the middle of the boom is better than that of pressurization at both ends of the boom. The powder injection distance increases with the increase of pressurization pressure, and the secondary pressurization at 0.15 MPa in the middle of the boom can increase the maximum exit velocity and effective powder coverage by 61.8% and 28.4%, respectively, showing the best injection effect. Related Articles | Metrics

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Design of integrated communication link based on the "emergency rescue digital battlefield" platform Ming Zhaohui, Shi Yang, Xie Chenyang, Yuan Shuai 2024, 43 (2):  227-230.  Abstract ( 100 )   In order to cope with increasingly frequent and complex disasters, a digital battlefield platform for emergency rescue has emerged, which integrates communication systems, image analysis systems, command and dispatch systems, and more. This article analyzes the communication security issues that exist in actual rescue operations, proposes solutions based on existing fire rescue related laws, regulations, and norms, and combines communication technology to develop integrated communication system link installation plans. It verifies the feasibility and effectiveness of emergency communication security practical exercises. By integrating communication system links through hierarchical division, guidance is provided for fire rescue teams to quickly build communication networks at disaster sites, achieving real?time transmission and analysis of multi?source information based on platforms, resource sharing and intensification among units at all levels, and scientific and rapid command and judgment, rescue operations, and disaster response. Related Articles | Metrics

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Application of multi-point surveillance videos analysis in fire process reconstruction Wang Xiaojun, Miao Xinyong, Han Chong, Wang Xin, 2024, 43 (2):  231-236.  Abstract ( 89 )   Taking a large warehouse fire accident investigation as an example, this article introduces the application of multi-point surveillance videos analysis in fire process reconstruction. The videos containing valid information are screened out through primary screening of the points, and the time error between points is eliminated through relative time calibration. Then the ignition time is determined according to the comprehensive analysis of video images of each point, and the ignition area and fire behavior are determined based on the cross-location and mutual confirmation of the light and shadow at each point, thus reconstructing the fire process. On this basis, the precautions for extracting multi-point surveillance videos in fire investigation are analyzed, and the principles and methods of multi-point surveillance videos analysis are summarized. Related Articles | Metrics

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Optimization of heat pump drying fire hose with variable temperature strategy Liu Cuiyu, Liu Long, Hu Zhangpeng, Lei Xinyu 2024, 43 (2):  237-243.  Abstract ( 56 )   As an important fire prevention and control tool, the maintenance of fire hose is particularly important. Timely drying of the hose can extend the service life of the hose and ensure that it is always in good working condition. To reduce the drying energy consumption of fire hose and optimize the drying performance of heat pump, the heat pump drying treatment of fire hose is performed with variable temperature strategy. The effects of initial drying temperature, moment of changing temperature, and variable temperature on the performance of heat pump (specific moisture extraction rate, moisture extraction rate, coefficient of performance) were analyzed by single factor test. Experiments were designed using the response surface method, the mathematical model was fitted to the test data, and the reliability of the model was verified by variance analysis. The multi-objective joint solution of the regression equation was carried out, and the optimal process parameters of the heat pump variable temperature drying fire hose were obtained as follows: initial drying temperature was 42.2 ℃ , the moment of changing temperature was 80 min, and the variable temperature was 33.8 ℃.Parallel experiments show that the average error between the predicted value and the experimental value is 3.92%, indicating the high reliability of the model. Related Articles | Metrics

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A computer aided building fire risk assessment method based on BIM Liu Tao, Wang Weixing 2024, 43 (2):  244-248.  Abstract ( 82 )   In order to determine whether there are deviations in the fire safety of buildings and whether supporting fire protection measures are in place, this study uses Revit software to establish a highly interactive BIM model. Through FRAME method, combined with potential fire risk factors, probability of fire occurrence, and degree of damage caused, a rapid and accurate fire risk situation assessment of buildings is carried out with the goal of "acceptable risk". Finally, an example of cold storage was used for validation. Related Articles | Metrics

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Polyurea elastomer with aluminum hypophosphite: flame retardancy and aging resistance He Yunfei, Yue Changshan, Wang Baozhu, Zhao Bin 2024, 43 (2):  249-254.  Abstract ( 392 )   In order to improve the flame retardancy of polyurea elastomer (PUA), aluminum hypophosphate (AHP) was used to prepare flame retardant PUA. The thermal performance, flame retardancy, mechanical properties, and flame retardancy mechanism of flame retardant polyurea were systematically studied through a series of tests such as thermogravimetric analysis, ultimate oxygen index, vertical combustion, cone calorimetry, scanning electron microscopy, thermogravimetric infrared spectroscopy, stretching, and tearing. The results indicate that AHP has a high flame retardant efficiency on PUA. At a 20% addition, PUA exhibits self extinguishing properties in vertical combustion tests, and the droplet phenomenon disappears, passing the UL-94 V-0 rating. At the same time, the peak heat release rate, total heat release, total smoke release and other fire safety behavior parameters have significantly decreased. The microstructure and gas phase pyrolysis product analysis of residual carbon indicate that a denser and compact carbon layer is formed on the surface of flame-retardant PUA after combustion, effectively suppressing the generation of hydrocarbons, CO2, CO and other substances in the pyrolysis PUA substrate. The mechanical performance test results show that the addition of AHP has an acceptable loss in tensile strength, elongation at break, and tear strength of PUA. Flame retardant PUA still shows high mechanical properties after 168 hours of thermal oxygen aging treatment. Related Articles | Metrics

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Effect of oxygen concentration on pyrolytic and combustion characteristics of flame⁃retardant EPDM Rubber Yue Hailing, Guo Zidong 2024, 43 (2):  255-260.  Abstract ( 338 )   Fire?resistant EPDM rubber is widely used in public buildings, transport and other areas where the oxygen concentration changes during a fire. In order to study such materials in real fires, this paper uses a flame?retardant EPDM flooring rubber as a sample and experiments are carried out using a FPA and TG?DTG?DSC analyzer under different oxygen volume fraction to study the effect of oxygen concentration on pyrolysis and combustion behavior. The results show that the rate of weight loss, heat release and activation energy decrease when the oxygen concentration decreases in an aerobic atmosphere, but the reaction model remains unchanged. The oxygen volume fraction of the sample that can cause open flame combustion ranges from 15% to 18%. In the presence of open flame combustion, the decrease in oxygen concentration resulted in a lower flame, a decrease in the amount of irritating black smoke, a decrease in the amount of greyish-white areas and cracks on the surface of the residue, and a shallower fissure; an increase in the critical heat radiation flux, equivalent convective heat transfer coefficient, and ignition temperature, and a decrease in the first peak of the HRR curve and in the rate of fire propagation; the second peak in the CO production rate, and an increase in the CO/CO2 value. In the case of combustion without open flame, the samples released a large amount of grey smoke, the middle of the residue was raised, the middle of the surface was grey?black, metallic, with yellow-brown viscous liquid at the bottom, and the CO and CO2 yields were much lower than those of flaming combustion. Related Articles | Metrics

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Application of polyaniline⁃silicon carbide composites in intumescent flame⁃retardant coatings Wang Xiaoming, Zhu Gengzeng, Jia Dan, Jin Yijie 2024, 43 (2):  261-264.  Abstract ( 87 )   Intumescent flame?retardant coatings are effective in blocking the rapid warming of the substrate. In this experiment, polyaniline?silicon carbide （PANI?SiC） composites were synthesized, and the morphology, composition and structure of the composites were analyzed by means of SEM, FTIR and XRD, and the effects of the type of one?component intumescent flame?retardant coatings emulsions and the content of the composites on the fire resistance performance of the coatings were investigated. The results show that vinyl acetate?ethylene （VAE） emulsion can better improve the expansion ratio and flame resistance of the coating compared with phenylpropylene and acrylic emulsion With the increase of PANI?SiC content, the expansion ratio of the coating increases and the backside temperature decreases, and the fireproof coatings with 10% content of composites show excellent flame resistance. Related Articles | Metrics

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Study on the potential fire behavior of surface fuels in coniferous forests in Haizhai forestry, east Yunnan region Ma Cheng, Wang Jin, Han Zhengbao, Wang Qiuhua, 2024, 43 (2):  265-270.  Abstract ( 75 )   Sample plots were set up within the coniferous forests of Haizhai forestry, field surveys were conducted, surface litter was collected, and indoor combustion simulations and laboratory physical and chemical property analyses were performed, and SPSS 26.0 software was used to analyze the data to explore the characteristics of surface combustibles and potential fire behavior of the coniferous forests in Haizhai Forestry. Lanceolata had the worst combustibility as it had an absolute moisture content of (9.4±0.65)% and the lowest calorific value (19 878.9±48.63) kJ/kg, and also had the smallest fire intensity and rate of spread of (259.64±19.73) kW/m and (0.33±0.14) m/min, respectively. Pure forest of Pinus yunnanensis has a load of (0.27±0.12) kg/m2, a calorific value of (21 390.88±73.39) kJ/kg, a low fire intensity (307.26±15.83) kW/m, and an actual burn rate of only (55.32±15.02)%. Pure forest of Pinus yunnanensis has the highest calorific value and ignites easily, but the load is too low to sustain a normal burn. The calorific value of pure forest of Pinus huasanensis was lower than that of Pinus yunnanensis, and the fire intensity and burn rate were lower than those of mixed forest of Pinus yunnanensis-Pinus huasanensis. The spread rate and fire intensity of mixed forest of Pinus yunnanensis-Pinus huasanensis were (0.82±0.31) m/min and (564.14±13.53) kW/m, which were much higher than the other three species, and had the highest potential fire risk class. From the above potential fire behaviors, the risk level (from high to low) of the four types of coniferous forests in Haizhai Forestry to start a fire is mixed forest of Pinus yunnanensis-Pinus huasanensis, pure forest of Pinus huasanensis, pure forest of Pinus yunnanensis and lanceolata. Related Articles | Metrics

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Analysis and experimental study on the causes of forest fires under 10 kV lines Yang Bowen, Chen Tianxiang, Wei Yuwen, Zeng Chaoxu 2024, 43 (2):  271-277.  Abstract ( 94 )   In recent years, forest fires caused by tree-line failures have occurred frequently both domestically and internationally. Forest fires have been triggered by external social factors, leading to frequent incidents of power transmission and distribution line tripping. This article focuses on the forest fire accident below a 10 kV distribution line. From the perspectives of social factors causing forest fires and tree-line failures causing forest fires, the impact of various extreme environments such as pure flames, tree line discharge, and post discharge fires on the surface traces of conductors is considered. Through a distribution network fault simulation true type test platform, the surface morphology changes of conductors under extreme environments are experimentally studied, and the fire traces, first and second traces of tree wire discharge are obtained. Based on macroscopic, microscopic, and image feature extraction methods, the characteristics of various types of traces were analyzed, and a method for identifying single discharge traces of tree lines was found. The research results indicate that the discharge marks are on the one hand, the tree line arc directly erodes the wire, and on the other hand, the arc indirectly transfers carbon slag to the surface of the wire to form carbon black marks. When the tree-line failure did not cause a forest fire in the early stage, there was only first discharge trace on the surface of the wire. Under the same conditions, the discharge from the pine tree caused the most significant change in the weight of the wire, which could increase by 0.59 g. After the forest fire caused by the last stage tree-line failures, the burn marks will cover the discharge marks and form secondary traces. After wiping the surface traces, it was found that the grayscale surfaces of the first and second traces are similar, and the difference in fractal dimensions is less than 0.03. Related Articles | Metrics

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Practice and exploration of building a modern grassroots fire safety governance system Chen Shuo, Pan Li, Liu Jian 2024, 43 (2):  278-281.  Abstract ( 138 )   With the deepening of the modernization construction of grassroots governance system and governance capacity, as well as the deepening implementation of the national rural revitalization strategy, the people have new expectations and demands for the safety guarantee elements of a better life. This article starts from connecting the overall economic and social development, adapting to the new requirements of modernization construction of national governance system and governance capacity, and based on the situation in Sichuan Province, dialectically analyzes the current situation of grassroots fire safety work, benchmarking the objective problems and shortcomings, strategies and methods for building a modern grassroots fire safety governance system were proposed from improving the legal and policy system, enriching fire prevention forces, improving fire protection foundation, enriching governance measures, and improving publicity and education. Related Articles | Metrics

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Analysis and discussion on the construction of Chinese and American civil aircraft water rescue system Jia Jingyun, Chen Xiantao 2024, 43 (2):  282-287.  Abstract ( 101 )   Aviation emergency management system is the lifeline of civil aviation development, and the construction of aircraft water rescue system is an important part of aviation emergency management system. Based on the current situation of the civil aircraft water rescue system construction in China and the United States, this paper objectively analyzes the problems existing in the four dimensions of the civil aircraft water rescue system in China, such as standard system, emergency response, rescue equipment and professional training. This paper argues that we can further improve the construction and development of China's civil aircraft water rescue system by perfecting the standard system of civil aviation water rescue, constructing the rescue coordination mechanism of regional departments, strengthening the research and development of special rescue equipment, establishing the national comprehensive information guarantee platform, and rationally arranging the water rescue training bases. Related Articles | Metrics