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15 October 2023, Volume 42 Issue 10 Previous Issue    Next Issue

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Suppression effect of liquid nitrogen on thermal runaway of lithium iron phosphate energy storage batteries Wang Zhi, Yin Bo, Yu Yong, Zhou Wei, Shi Bobo 2023, 42 (10):  1315-1321.  Abstract ( 313 )   To investigate the effect of liquid nitrogen （LN） on thermal runaway （TR） in lithium iron phosphate energy storage batteries, a TR suppression experimental platform was constructed. The effect of LN on TR was analyzed by varying the occasion and dose of LN injection. Prior to LN inhibition of TR, blank experiments were conducted to determine the TR characteristics of the battery used. The results demonstrate that LN effectively inhibits TR. Specifically, injecting 1.2 kg of LN before the safety valve opened can prevent TR. However, during the early stages of TR, the injection of 1.2 kg of LN only provides temporary temperature reduction and cannot inhibit TR. By increasing the LN injection dose to 6.7 kg, TR can be successfully inhibited. In the period of severe TR, injecting 7.2 kg of LN can effectively inhibit TR. Additionally, the cooling and inhibition effect of LN on TR increases with increasing LN dose. The cooling effect of 8 kg LN injection on TR of lithium?ion battery is about 5.8 times of 6.2 kg LN injection, and the cooling rate is about 4.95 times of injection of 6.2 kg LN. However, the effective utilization rate of LN did not increase with the increase in LN injection dose. Related Articles | Metrics

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Effect of nanofiber material on thermal runaway propagation of lithium battery Zhang Qingsong, Yang Kaibin, Zhao Yang, 2023, 42 (10):  1322-1327.  Abstract ( 153 )   The thermal runaway of lithium battery caused by bumping and external short circuit during transportation and use is very easy to induce the surrounding batteries to heat up, leading to the spread of thermal runaway. In order to control the thermal runaway propagation of lithium batteries, this paper uses nanofiber materials to inhibit heat propagation, and uses corrugated paper, ceramic fiber and glass fiber as spacer materials to carry out the thermal runaway test of lithium batteries, and evaluates the insulation materials in terms of heat insulation and fire resistance. The results show that although the thermal insulation performance of the nanofiber material will prompt the first battery to enter the thermal runaway state faster, the propagation of the thermal runaway of the lithium battery can be effectively suppressed due to its good thermal insulation performance. The heat flux density of the thermal insulation materials during the combustion explosion of the first battery is measured, and it is found that the peak heat flux of ceramic fiber paper is lower, and the thermal insulation performance of nanofiber materials is better than that of corrugated paper. At the same time, the fire resistance of the three materials was tested to determine the reliability of the materials during the battery explosion, and it was found that the corrugated paper was very easy to burn, while the nanofiber material had good thermal stability. The results demonstrate the feasibility of nanomaterials as transportation spacers for lithium batteries. Related Articles | Metrics

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Analysis and research on fire spread behavior and influencing factors of rooftop photovoltaic modules Wang Yue, Zhang Wang, Lv Dong, Yang Mingrui, 2023, 42 (10):  1328-1333.  Abstract ( 199 )   In this paper, the influence rules of different factors on the fire spread of photovoltaic modules are given through comparative analysis, and the theoretical analysis of the fire spread of photovoltaic modules is carried out by combining the physical experiment and simulation calculation. Through the analysis of fire spread heat flux of photovoltaic modules, it can be found that the installation of photovoltaic modules on the roof blocks and reflects the flame, expands the range of preheating zone and the maximum temperature, and thus promotes the fire spread of photovoltaic modules. The simulation results are verified through the physical experiment analysis. The influences of waterproof coil, photovoltaic module shielding, wind speed, roof slope and other individual factors are analyzed by FDS numerical simulation calculation. The waterproof coil provided the fuel in the preheating zone, the photovoltaic module promoted the heat deflection of the flame, and the wind speed and slope expanded the scope of the preheating zone and increased the non?uniformity of heat flow, thus promoting the spread of flame. The solid experiment results are basically consistent with the simulated calculation results, and the error is caused by uneven combustion. More different types of solid experiments can be carried out to verify and correct the simulated calculation results. Related Articles | Metrics

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Study on smoke backflow prevention strategy in traffic tunnel with slow lane Jiang Xuepeng, Zhu Pan, Liu Jiaping 2023, 42 (10):  1334-1338.  Abstract ( 95 )   In order to prevent the fire smoke from spreading to the tunnel entrance, it is poured into the adjacent non?accident tunnel under the action of environmental wind. In this paper, the characteristics of smoke backflow at the entrance of a traffic tunnel with a slow?moving road under different wind speeds are studied by numerical simulation. The results show that the intrusion rate of fire smoke increases with the increase of ambient wind when no smoke control measures are taken in the non?accident holes, and increases with the increase of environmental wind. The smoke?proof wind speed of the driveway to prevent the backflow of smoke increases with the increase of the ambient wind speed and changes linearly. The normal operating wind speed 0.5 m/s of the slow lane can prevent the back flow of smoke into the slow lane. It was found that when the opening rate of the natural smoke exhaust outlet of the closed sound barrier is set to 10%, the natural smoke extraction scheme with continuous opening and vertical wall is the best, and the penetration rate of fire smoke to non?accident holes is the lowest. Related Articles | Metrics

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Analysis of leakage diffusion and explosion of natural gas pipeline under urban main road Zhao Wei, Zhang Hai, Li Dan, Wang Dai 2023, 42 (10):  1339-1343.  Abstract ( 105 )   For the possible leakage and diffusion of existing natural gas pipelines under Tianjin urban main road and the risk of inducing explosion, combined with the climatic characteristics of the city, the leakage and diffusion characteristics of natural gas pipelines at the leakage point and the impact of explosion shock waves on nearby buildings were studied based on FLACS. The results show that the influence of wind speed on the leakage and diffusion of natural gas pipeline under the main road is obvious. The larger the wind speed is, the smaller the natural gas cloud in the explosion range is, which is more favorable for emergency rescue. However, the possible changes of wind speed and wind direction during the rescue process should be fully considered, when closing the natural gas valve and evacuating people in the downwind direction, the dangerous behavior within 5 m around the leakage point and 24 m from the ground height should be strictly controlled. The leakage and diffusion of natural gas pipeline under the main road has a great impact on the surrounding area. The horizontal diffusion distance of natural gas under the maximum wind speed of the city can reach 25 m. The area should be evacuated in time. The explosion overpressure of natural gas pipeline leakage under the main road decreases with the increase of the height above the ground. The maximum overpressure exceeds 1.5 kPa,the peak value of overpressure load is mainly concentrated within the range of 4~22 m above the ground so the anti?explosion protection should be considered. Related Articles | Metrics

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Experimental study on combustion inhibition of aviation kerosene by C6F12O based on OH-PLIF technology Wang Linsen, Che Qingfeng, Chen Guozhu, Zhou Quan 2023, 42 (10):  1344-1349.  Abstract ( 89 )   In order to make a profound study on the change rule of OH which was restrained by C6F12O in combustion process of aviation kerosene, a cup burner with optical windows was designed. Based on OH-PLIF (planar laser?induced fluorescence) technology, the "difference method" measurement which was used two different wavelengths, solved the problem that was caused by soot, kerosene and combustion cracking macromolecular compounds in combustion field of aviation kerosene. The OH distribution characteristic maps of twelve experimental conditions were obtained. The maps had important reference significance for studying the inhibition mechanism of  C6F12O, and they also provided basic dates for establishing theoreti-cal model of the inhibition mechanism. The experimental results showed that parameter H which meant the vertical height of OH distribution was stretched slowly if  C6F12O was low volume fraction (<3.91%). However, parameter H would decline rapidly then gradually gently if the concentration  C6F12Owas rising continuously. In addition, parameter D which meant the thickness of OH distribution zone and parameter S which meant the proportion of OH distribution area were showing obvious downward trend if the concentration of  C6F12Owas rising continuously. Related Articles | Metrics

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Experimental study on flame merging probability of double pool fires at different transverse positions in road tunnel Peng Wei, Xie Qi, Liu Xianhao, Zang Xue 2023, 42 (10):  1350-1355.  Abstract ( 123 )   To investigate the flame merging probability of dual fires in a naturally ventilated tunnel, a series of experiments were conducted using a 1∶10 scale model of the tunnel. The study focused on how the position and spacing of the fires affected the merging probability. The results showed that the merging of fires in different positions can be categorized into three stages: continuous merging, intermittent merging, and non-merging. In the continuous merging stage, the probability of flame merging is always 1. In the intermittent merging phase, the probability of flame merging decreases rapidly as the distance between the fires increases. In the non-merging phase, the probability of flame merging is always 0, and a greater distance between the fires is needed for the probability of flame merging at the wall-adhering position to reach 0. In the range of dimensionless fire source spacing between 0.27 and 0.80, when the dimensionless fire source lateral position is less than or equal to 0.06, the probability ratio of flame merging decreases linearly with the increase of non-dimensional lateral position of the fire source. When the non-dimensional lateral position of the fire source is greater than 0.06, the ratio of flame merging probability no longer changes significantly with the increase of non?dimensional lateral position of the fire source. Related Articles | Metrics

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Study on effect of pipe wall conduit on methane explosion flame discharge in pipeline Huang Yong, Deng Wenhui, Zhang Yun, Luo Zibiao 2023, 42 (10):  1356-1361.  Abstract ( 78 )   In order to improve the explosion release efficiency and protection level of combustible mixed gas in a narrow and long space, the methane explosion discharge test in square pipes with pipe wall conduits was carried out, and the influence of pipe wall conduit diameter and position factors on the gas flame propagation process and explosion overpressure in the pipeline was explored by changing the length diameter ratio and position of the pipe wall conduit. The results show that there is a slight lag in the time of the release effect of the pipe wall conduit on the flame. Compared with the working condition of conduit without pipe wall, when the pipe diameter of catheter is 60, 80 and 100 mm, the flame propagation time is extended by 15.4%, 35.8% and 61.0%, and the peak peak explosion overpressure is reduced by 24.5%, 30.5% and 40.4%, respectively. The same pipe diameter pipe wall conduit placed at the front end of the square pipe can effectively discharge part of the flame and pressure, reduce the lateral propagation power of explosion energy, and the explosion discharge effect is obviously better than that of the pipe wall conduit placed in the middle and back end of the pipeline. When the conduit was placed at the front end, middle and rear end, the flame propagation time was extended by 85.4%, 15.4% and 4.5%, and the peak peak explosion overpressure decreased by 40.6%, 24.5% and 18.6%, respectively. Therefore, the installation of pipe wall conduit can effectively reduce the speed of flame propagation and vent explosion overpressure. Related Articles | Metrics

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Research on fire evacuation path of exhibition hall based on improved ant colony algorithm Huang Ying, Zheng Xuelin, Zhao Xin 2023, 42 (10):  1362-1369.  Abstract ( 116 )   In order to minimize the casualties and losses caused by fire in the exhibition hall. This paper puts forward research on fire evacuation path of exhibition hall based on improved ant colony algorithm. Firstly, quantified fire products, angle and distance factors are used to improve the heuristic function. The pheromone update model conforming to the process of crowd evacuation was established. Thereby, the traditional ant clony algorithm was improved. Secondly, the dynamic evacuation model of personnel was established, with the shortest evacuation time and distance as the target function; the two-dimensional evacuation environment and the grid map are built, and then rises to the 3D environment model. Finally, taking an exhibition hall in Xi'an as an example to conduct research, the 3D grid environment of 30×25×3 was established in MATLAB, the parameters were optimally combined and configured. The improved ant colony algorithm was used to simulate fire scenes at different stages and the convergence was analyzed. Results show that the improved ant colony algorithm is suitable for 3D evacuation models. The algorithm has excellent convergence speed and search capabilities. Using this improved algorithm in large exhibition hall, the best evacuation route can be quickly found. It helps to improve the efficiency of personnel evacuation in exhibition hall. Related Articles | Metrics

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Research on evacuation and escape psychology and behavior of personnel in commercial complex fire scenarios based on VR technology Zhang Xiaochun, Han Shuyang, Xu Yuepeng, Chen Qinpei, 2023, 42 (10):  1370-1373.  Abstract ( 106 )   With the economic development, the number of commercial complexes in major cities is increasing, and shopping and entertainment in commercial complexes are favored by consumers. Due to the large building area and complex internal structure of the commercial complex, in case of fire, most people are not familiar with the safety exit path, which is not conducive to evacuation. In order to study the evacuation psychology and behavior of people in the event of a fire, this study used Blender and Unity 3D to construct a VR fire scene of a large commercial complex, combined with the monitoring of subjects' heart rate change, escape time and the correct escape, carried out K-means clustering analysis on the experimental data by machine learning. The purpose of this study is to classify and analyze the evacuation psychology and behavior of personnel, and at the same time to enhance the evacuation safety awareness of personnel and improve the safety education of fire evacuation ability. Related Articles | Metrics

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Research on natural smoke exhaust in waiting hall of Chongqingdong railway station based on shop fire test Ding Dan, Song Yang, Geng Weichao, Yang Longlong, 2023, 42 (10):  1374-1379.  Abstract ( 92 )   In order to study the rationality of smoke control system design in waiting hall under the condition of the physical fire test, the fire test of the shop was carried out first. Flashover occurred in the shop at 814 s, and the maximum heat release rate was 12.9 MW at 993 s. This data was then input into FDS to conduct research on smoke exhaust in the waiting hall under four different window opening modes, and compared and analyzed the smoke spreading law, temperature, visibility and wind speed changes in the waiting hall. The results show that after the exhaust window is opened, the smoke layer and visibility interface are increased by 10 m and 8 m respectively, and the natural exhaust effect is obvious. The temperature at a height of 2 m above the interlayer ground in the four window opening modes within 1 800 s is less than 60 oC, the visibility is greater than 10 m, and the wind speed of the natural supplementary air outlet in the four directions is less than 3 m/s, which can ensure the safe evacuation of personnel. At the same time, the smoke exhaust efficiency of the roof window is much higher than that of the high side window. The difference between the smoke layer and the visibility interface of the high side window with a window ratio of 4% and the top window with a window ratio of 0.64% is only 1 m. The design of the smoke control system can meet the needs of safe evacuation of people under different window opening modes, but priority should be given to smoke exhaust from the roof window and increase the smoke exhaust area of the roof window. Related Articles | Metrics

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Study on the influence of smoke on adjacent room in high⁃rise buildings Liu Fei, Yu Zhaoyang, Li Wei, Zhao Haoyou 2023, 42 (10):  1380-1385.  Abstract ( 120 )   In order to study the impact of smoke from high-rise building fires on adjacent rooms, a 1:10 small?scale high-rise building fire experimental platform was built. By setting different ignition positions, fire source power, and analyzing the temperature rise of adjacent rooms, the impact of smoke on adjacent rooms was preliminarily determined. The results show that the higher the fire floor, the weaker the chimney effect, and a large amount of smoke accumulates in the horizontal space, resulting in a significant increase in adjacent room temperature. As the position of the fire room approaches the front chamber, the adjacent room temperature rise gradually decreases. In the early stage of combustion, the adjacent room temperature rise decreases as the distance from the ignition chamber increases. As the combustion time continues, the temperature rise in the room far from the fire room and near the end of the corridor increases. The greater the power of the fire source, the stronger the stack effect, which reduces the concentration of smoke in the remote room of the fire room. Therefore, when high?rise buildings catch fire on high floors, the smoke from fires in high floors and rooms far from vertical passages has a stronger impact on adjacent rooms. Related Articles | Metrics

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Guided evacuation path planning research based on the GDACO algorithm Wang Xin, Zhang Linxuan, Dong Fangfang 2023, 42 (10):  1386-1392.  Abstract ( 66 )   For the problems of blind, disorderly, and inefficient evacuation of personnel in teaching buildings, the Guided Double Layer Ant Colony Optimization Algorithm （GDACO） is proposed for guiding personnel evacuation. Firstly, the environmental grids are processed by adding dangerous grids to establish a staggered distribution of initial ant pheromones. Secondly, the double layer ant colony algorithm is introduced, where the guiding layer ants conduct global searches to find guiding paths while the evacuation layer ants optimize evacuation paths based on the guiding range. Finally, path optimization is performed by removing redundant nodes and smoothing turning points. Experimental results analysis shows that the proposed GDACO algorithm can reduce path turning points, avoid risky paths, meet the evacuation needs within teaching buildings, and plan paths that align with actual evacuation situations. Related Articles | Metrics

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Effectiveness of compressed air foam nozzle for extinguishing 20A wood crib fire in super high⁃rise building Chen Tao, Wang Yuwei, Zhang Peng, Qin Guoyang, 2023, 42 (10):  1393-1397.  Abstract ( 98 )   Compressed air foam fire extinguishing technology is an important development direction to solve the fire fighting problem in super high-rise buildings, but the fire extinguishing performance of compressed air foam after vertical long-distance transport is still to be further studied. In this paper, the foam nozzle actually configured in the super high-rise buildings was used to simulate the equivalent foam with the same performance as the actual working condition by adjusting the input parameters. And the ability of compressed air foam after vertical long-distance transport to extinguish Class A fire was verified by the standard 20A wood crib fire extinguishing test. The results showed that the flame can be completely extinguished for 141 s when the mixed liquid is 92 L/min and the gas-liquid ratio of the foam is 9.8：1.0, and there was no reignition within 10 min. Meanwhile, the flame can be completely extinguished for 54 s when the mixed liquid is 126 L/min and the gas?liquid ratio of the foam is 6.0:1.0, and there was no reignition within 10 min. Related Articles | Metrics

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Application of fire host with inside diameter 50 mm in building fire Yang Xue, Xu Zhiyong 2023, 42 (10):  1398-1402.  Abstract ( 115 )   This article discusses the application of 50 mm fire hoses in building fire fighting. Through calculations, comparisons, and measurements, the performance parameters of 50 mm and 65 mm hoses are compared. The advantages of using 50 mm hoses in terms of the number of personnel, fire water supply, fire extinguishing load, ease of operation, hose loss, and personnel safety are studied. Meanwhile, the weaknesses of 50 mm hoses in terms of impedance coefficient, water supply intensity, and vertical laying are analyzed. The conclusion points out that firefighting and rescue teams should use and popularize 50 mm hoses as the main branch hoses in extinguishing building fires to optimize firefighting and rescue operations and ensure safety. Related Articles | Metrics

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Experimental study of high⁃pressure fine water mist fire extinguishing system to suppress flashover ignition in ancient buildings Yu Pingwei, Wang Yixin, Tian Yating, Qiao Yiqiang 2023, 42 (10):  1403-1407.  Abstract ( 121 )   In order to investigate the effect of high-pressure fine water mist on the suppression of ancient building fires, this paper simulates and builds an experimental platform through Pyrosim software to determine the the self starting time of fire water mist under fire linkage alarm,temperature of the smoke layer of ancient building flashover under different spray intensities, the rate of heat release from the fire, combined with a comprehensive fire prediction method to analyse the occurrence of flashover in ancient buildings when the fine water mist is turned on. The results show that the fine water mist turned on 103 s after the fire occurred; the high-pressure water mist with a spray intensity of 1.3 L/（min·m2） can suppress the ancient building flashover, and the high-pressure water mist with a spray intensity of 2.0 L/（min·m2） can extinguish the ancient building flashover. High-pressure fine water mist can effectively inhibit the ancient building flashover, the study can provide reference for high-pressure fine water mist fire extinguishing system applied to the ancient building fire design. Related Articles | Metrics

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A trapped person detection and location model based on the image recognition technology Zhang Bo, Jiang Huiling, Sun Jing 2023, 42 (10):  1408-1412.  Abstract ( 115 )   The accurate acquisition of the location of trapped persons at various disaster scenes can provide decision support for the formulation of rescue plans and further enhance rescue efficiency. In order to obtain the location of people at disaster scenes more accurately, this paper explores an intelligent model for detect and locate the trapped person based on the analysis and summary of existing methods. The system is developed based on the image recognition can automatically analyses real-time video surveillance footage and recognizes whether a person is in a specific distress posture or trapped, so as to send the trapped location and relevant information to rescue personnel for assistance. After testing, the detection accuracy of the system on the personnel posture test set is 94%, and the detection accuracy on the personnel status test set is 90%. Related Articles | Metrics

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Analysis and improvement of credit management system in field of fire safety Yao Yongzheng, Xia Ziyang, Liao Yaoqiang, Xu Xiaonan 2023, 42 (10):  1413-1417.  Abstract ( 124 )   By investigating the development of fire safety credit at home and abroad, the national policy, and the fire safety credit management regulations of various provinces and cities, we summarize the current fire safety credit management system and existing questions in China. Under the guidance of the latest national policy and relevant safety management regulations, we make a great modification for current system structure. Some suggestions and measures are put forward in the aspects of characteristic classification, scoring method optimization and credit information exchange and so on, and finally an optimal credit management system of fire safety is developed, which can improve the level of fire safety management to some extent and then reduce the number and consequence of fire accidents. Related Articles | Metrics

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Remote monitoring system for smoke control and prevention based on the Internet of Things Han Chong 2023, 42 (10):  1418-1422.  Abstract ( 121 )   In response to the fire safety hazards, information management and maintenance issues in urban building fire protection systems, this article focuses on the CHV32F103 chip and develops fire protection equipment such as a fire fan status information collector and a wind system status information collector. A remote smoke control and monitoring system based on the Internet of Things is proposed. The system consists of a remote control center and on?site monitoring equipment. Its main purpose is to remotely monitor urban building fire protection facilities and analyze and process real-time collected various fault and alarm information. On-site monitoring equipment sends real-time fire alarm signals, smoke exhaust valve action status, and smoke exhaust fan operation status information to the remote control center through Internet of Things communication networks such as NB IoT, ensuring accurate judgment in the event of a fire, achieving remote monitoring and management of the smoke exhaust system. Related Articles | Metrics

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Research on avoiding shelter of automatic fire monitor in large⁃scale closed coal storage yard Hu Chunguo, Xu Li 2023, 42 (10):  1423-1427.  Abstract ( 78 )   In the design of automatic fire monitor system in large?scale closed coal storage yards, the automatic fire monitors arranged on the horse road are mainly affected by coal stacking and roof, and the design maximum protection radius is suppressed. But the relevant standards and literature lack corresponding countermeasures. Taking an example of a closed coal storage yard with 200,000 t of reserves in a certain place in Inner Mongolia, the influences of coal stacking and roof on the automatic fire monitors and countermeasures were studied. Firstly, the viewing angles of fire source detector in automatic fire monitor and jet trajectory characteristics were utilized to select the optimal layout area and height range of the automatic fire monitors in the direction of building width. Then, according to the maximum protection radius of the automatic fire monitor, determined the best position in the direction of building length. After that, the actual protective range of the automatic fire monitors was reviewed with the jet trajectory sprayed at an angle of 0°. Finally , the influences of coal stacking and roof on the automatic fire monitors were eliminated. Related Articles | Metrics

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Flame retardant properties and mechanisms of cotton fabrics finished by MFA microsphere suspension⁃silica sol systems Zhou Chang, You Fei, Li Dan, 2023, 42 (10):  1428-1433.  Abstract ( 69 )   MFA microspheres were prepared by condensation reactions with melamine (MEL), formaldehyde (FM) and 5-adenosine monophosphate (AMP), and were immersed in a sodium alginate (SA, dispersant) solution to form a SA-MFA suspension. A SiO2 sol was prepared by dehydration polycondensations using tetraethyl orthosilicate (TEOS) as a precursor. The SA-MFA suspension and SiO2 sol were coated into cotton fabrics successively by dipping-drying method. The surface morphology and functional groups of treated cotton fabrics were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy(FTIR), respectively. Thermogravimetry (TG), limiting oxygen index(LOI), cone calorimeter (CC) and SEM techniques were used to characterize the pyrolysis characteristics, flammability levels, reaction-to-fire characteristics and surface microscopic morphologies of char residues after LOI tests of treated cotton fabrics. The results show that compared with the original cotton fabric, the flame retardant performance of SA-MFA-SiO2@COT is relatively optimal. Its char residue rate (46.39%) and LOI value (28.0%) values increase by 520.18% and 55.55%, peak heat release rate (PHRR, 114.67 kW/m2) and total heat release (THR, 5.09 MJ/m2) values decrease by 31.67% and 37.35%, respectively. During a combustion process, MFA microspheres and SA pyrolyze and promote the dehydration and carbonization processes of cotton fibers to release non?flammable gases like NH3, CO2 and H2O. Such processes can thus absorb heat and cool down, and dilute combustible gas concentrations. The SiO2 gel coating absorbs heat and further condenses, provides a physical barrier and structural support effect, blocks the transfer of heat, oxygen and gaseous products. The components show obvious synergistic flame retardant effects. Related Articles | Metrics

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Study on the synergistic fire extinguishing performance of octafluorocyclobutane and typical fire extinguishing gases Li Shukai, Chang Zhenxiang, Tan Chaoyang 2023, 42 (10):  1434-1438.  Abstract ( 91 )   Based on the flame height, flame temperature and flame morphology data of octafluorocyclobutane with N2, HFC-125 and HFC-227ea mixtures obtained from the combustion cup experiment, the synergistic effects and their proportional relationships were investigated. The results showed that octafluorocyclobutane showed negative synergy with N2 and HFC-125, and positive synergy with HFC-227ea. The best positive synergy was shown when the flow rate of octafluorocyclobutane was set at 13:5 with HFC-227ea, and the extinguishing volume fraaction was 7.02%, which was lower than the minimum extinguishing volume fraction of octafluorocyclobutane and HFC-227ea. Related Articles | Metrics

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Preparation of SiO2 aerogel thermal insulation material and study on its thermal insulation and fire resistance performance Liu Yang, Wang Lingjuan 2023, 42 (10):  1439-1443.  Abstract ( 139 )   In this paper, silica aerogel with different amounts of CTAB surfactant were prepared by acid base two-step method using tetraethyl orthosilicate as silicon source and hexadecyl trimethyl ammonium bromide as surfactant. The effects of surfactant on the microscopic morphology, lattice structure, thermal insulation and fire resistance of aerogel were studied. The results show that the SiO2 aerogel prepared by the acid base two-step method is a typical amorphous silica. The aerogel is formed by the accumulation of nanoparticles, and the particle size is between 30~80 nm. The addition of CTAB reduces the particle size of the SiO2 aerogel, and the skeleton is condensed. The compression strength of the aerogel is improved. The compression strength of the SiO2 aerogel with 0.1 mol of CTAB reaches the maximum value of 1.216 MPa. At 800 ℃, the maximum carbon residue of SiO2 aerogel with 0.1 mol CTAB content is 81.4%, the minimum thermal conductivity is 0.019 W/（m·K）, and the thermal insulation performance is the best. The shortest vertical combustion time of SiO2 aerogel with 0.1 mol CTAB was 8.1 s, the maximum LOI value was 34.8%, and the vertical combustion grade reached V1. The combustion rate of aerogel in the combustion process weakened, and the flame retardancy was significantly improved. Related Articles | Metrics

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Wildfire hazard susceptibility assessment based on coupled information value⁃machine learning Yue Weiting, Ren Chao, Liang Yueji, 2023, 42 (10):  1444-1452.  Abstract ( 118 )   In order to give full play to the advantages of statistics and machine learning model in the analysis and evaluation of wildfire disaster susceptibility, Guilin, which is rich in forest resources and deeply troubled by wildfire disaster, was taken as the research area, and 16 evaluation factors were selected from the aspects of climate, topography, hydrology and humanities. Based on the information value （IV） model, 4 machine learning （ML） models, including logistic regression （LR）, artificial neural network （ANN）, random forest （RF）, and extreme gradient boosting （XGBoost）, were coupled to evaluate the susceptibility of wildfire hazards in Guilin City. The results indicate that the IV-XGBoost model achieved an AUC of 0.957 and an accuracy of 0.921, demonstrating its superior predictive performance. It can effectively assess the susceptibility of wildfire disasters and provide valuable insights for local wildfire prevention and control. Related Articles | Metrics

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Research of quality certification and supervision system for forest fire fighting equipment product Zhang Xiaoying, Jiang Hua, Hu Qunming, Xia Jianjun, 2023, 42 (10):  1453-1456.  Abstract ( 105 )   The General Office of CCCPC and the General Office of the State Council jointly issued a document stating the need to build type spectrum and certification system in the field of forest firefighting equipment manufacturing industry at the national level. In points of key factors affecting the system construction， this article analyzes the current situation of manufacturing industry, the standardization and conformity assessment status and the present quality supervision system structure, then gives a quality certification and supervision management system structure. at last, proposes suggestions for how to establish a quality certification and supervision system,which is suitable to the current situation of our country， to provide reference for relevant national industry departments to establish a quality certification and super vision management system. Related Articles | Metrics