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15 April 2023, Volume 42 Issue 4 Previous Issue    Next Issue

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Study on the thermal runaway characteristics of LFP lithium-ion batteries under overheating and overcharge Zhang Lei, Huang Hao, Zhang Yongfeng, Cao Liying 2023, 42 (4):  439-442.  Abstract ( 711 )   Thermal abuse and electrical abuse are the main reasons for triggering lithium-ion batteries into thermal runaway. In this paper, the thermal runaway experiments of LFP lithium-ion batteries were carried out by overheating using a plate and constant current overcharging with or without external sparks. The thermal runaway process and characteristic parameters such as temperature and voltage were collected and analyzed, the intrinsic thermal runaway characteristics of LFP battery cells and the combustion characteristics with external ignition source were elucidated. As the result shows, the tested LFP battery produced a lot of white smoke under overheating, with maximum temperature of 184 ℃. The LFP battery jet flame was observed ignited by external energy, and the maximum temperature was 740 ℃. The thermal runaway of the LFP battery under overcharge was more severe, and the maximum temperature was 450 ℃, but no flame was observed. The LFP battery jet flame was observed ignited by external energy, and the maximum temperature of the flame was about 1 000 ℃. The LFP battery fire ignited by the external ignition source was a B-type stable fire dominated by the electrolyte if it was not completely under thermal runaway. The violent jet flame was observed with the external heat or electricity adding again. Related Articles | Metrics

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Influence of SiO2/HFC-227ea explosion suppressor with different complex ratio on methane/air explosion characteristic Yang Ke, Wang Yuesheng, Xing Zhixiang, Wu Jie 2023, 42 (4):  443-447.  Abstract ( 523 )   In order to improve the explosion suppression effect of a single type of detonation inhibitor on methane, the synergistic inhibition effect of silica powder and heptafluoropropane gas on 9.5% methane/air explosion was studied based on the self-built experimental platform. By changing the mass concentration of silica powder and the gas volume fraction of heptafluoropropane, the effects of the two independent and synergistic effects on the methane/air explosion characteristic parameters were studied. The results showed that under the combined action of heptafluoropropane gas and nano-silica powder, the gas-solid two-phase detonation suppressor exhibits synergistic inhibition on the explosion pressure, flame propagation velocity and flame propagation characteristics of 9.5% methane/air premixed gas inhibition. When the concentration of nano-silica powder reaches 0.10 g/L, adding heptafluoropropane gas with different volume fractions can have a good inhibitory effect on the explosion of 9.5% methane/air premixed gas. Under the condition of silica without heptafluoropropane, the maximum flame velocity decreased by 78.5%, and the maximum explosion pressure of the flame decreased by 79.7%, and the inhibition effect was the best. As the control parameters continue to increase, the suppression effect decreases. The mechanism of synergistic explosion suppression of gas-solid mixture was studied. It provides technical guidance for the application of two-phase explosion suppression technology. Related Articles | Metrics

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Analysis of thermal effect of natural gas jet fire on adjacent oil pipeline Liao Kexi, Wang Yuwei, He Guoxi, Chen Di 2023, 42 (4):  448-453.  Abstract ( 470 )   Aiming at the gas pipeline jet fire accident, a three-pipe parallel bridge crossing pipeline is taken as the research object. This paper took Fluent to carry out numerical simulation of natural gas jet fire, and the combustion characteristics of jet fire is analyzed based on fire flame length, temperature and heat radiation distribution under different leakage diameters. And the thermal response of adjacent oil pipelines under different oil flow rates were studied. The results show that: the flame maximum temperature is about 1 980 ℃. When the leakage diameter increases from 6.4 mm to 101.6 mm, the flame length, personnel and equipment damage spheres increase to 8.09 times, 7.13 times, and 6.70 times, respectively. The maximum temperature position moves to 36.4% of flame length from 12.5%. The adjacent pipeline temperature and pipeline equivalent stress are positively correlated with the leakage diameters.When the thermal stress is the dominant factor, the equivalent stress decreases with the flow rate increases, while the equivalent stress increases with the flow rate increases. Considering the variation of the equivalent stress and yield strength, it is recommended that the adjacent pipelines operate at 1.35~1.40 m/s in case of an accident. Based on the results, the paper proposes practical measures on the emergency operation to provide a basis for the accident disposal. Related Articles | Metrics

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Study on combustion characteristics of glass fiber phenolic composite material for cargo compartment side panels of civil aircraft Liu Quanyi, Ma Kaiqing, Wei Chaoyue, Zhang Ben, 2023, 42 (4):  454-457.  Abstract ( 458 )   In order to explore the combustion characteristics of the side panel material of civil aircraft cargo hold, cone calorimeter was used to study its combustion characteristics under fire environments, and two evaluation indexes were used to evaluate the fire hazard of the material. The experimental results show that the heat release rate curve of the material has only one growth peak. When the heat radiation intensity increases from 20 kW/m2 to 50 kW/m2, the heat release rate peak of the material combustion increases from 98.64 kW/m2 to 201.46 kW/m2, and the mass loss increases with the increase of radiation intensity. CO and CO2 production increased with the increase of radiation intensity during combustion; through the combustion ignition model, the theoretical critical heat flux of the sidewall material is 10.20 kW/m2; the change of thermal radiation value has a great influence on the fire risk index of aircraft cargo compartment sidewall plate. Related Articles | Metrics

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Study on the influence of urban gas pipeline leakage and diffusion under high-rise buildings Xie Zhengyi, Jiang Hongye, Gou Jingyu, Liu Hongmei 2023, 42 (4):  458-463.  Abstract ( 469 )   In order to study the influence characteristics of leakage and diffusion of medium and high pressure gas pipelines in cities and towns near high-rise buildings, considering the wind acceleration effect caused by the gap between high-rise buildings and the influence of different leakage positions on gas diffusion, Fluent is used to numerically simulate the environmental wind field and gas leakage and diffusion. The results show that: For urban high-rise buildings, the diffusion direction and range of gas can be predicted by judging the steady-state wind field; The accelerating wind speed near the ground has little effect on the deviation of leakage jet, and the diffusion of gas presents a columnar distribution between buildings; The methane leakage on the windward side is lifted at the top of the windward side of the building, and the leakage on the leeward side tends to diffuse to the side without the building, and finally presents as a gas cloud close to the building and the ground; The smaller the distance between the leakage hole and the building, the greater the harmful area of methane attached to the building. The influence of building height should be considered when designing the distance between the gas pipeline and the building;The acceleration ratio is introduced to quantitatively characterize the acceleration effect between high-rise buildings, and the three-dimensional distribution of acceleration ratio between high-rise buildings is proposed. The research can provide a theoretical basis for the prediction of urban gas pipeline leakage accidents and the emergency evacuation of personnel. Related Articles | Metrics

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Study on the suppression of FOX-7 dust cloud explosion by metal mesh Liang Kaili, Hu Lishuang, Liu Yang, Hu Shuangqi 2023, 42 (4):  464-467.  Abstract ( 465 )   In order to reveal the suppression effect of metal mesh with different parameters on 1,1-diamino-2,2-dinitroethylene (FOX-7) dust explosion, high-speed photography, pressure acquisition system and visual experimental device were used to study the flame propagation characteristics and pressure variation of FOX-7 dust in the presence/absence of metal mesh. The results show that compared with other non-explosive dusts, FOX-7 has faster flame propagation speed and shorter detonation duration. Metal mesh can effectively absorb combustion reaction heat and reduce flame brightness. With the increase of mesh number, the flame propagation height decreases from 62.20 cm to 42.97 cm, the flame propagation velocity decreases from 123.89 m/s to 100.49 m/s, and the maximum explosion pressure decreases from 63.1 kPa to 41.2 kPa. The attenuation rate of explosion pressure of FOX-7 dust ranges from 22.3% to 41.9% with the increase of the number of layers of metal mesh. When the number of layers of metal mesh is 4, the flame in the upper part of the metal mesh completely extinguishes. The results also show that the metal mesh has a certain quenching and pressure-lowering effect, and the inhibition effect increases with the increase of the number of layers and meshes of the metal mesh. Related Articles | Metrics

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Experimental study on fire hazard of aviation coolant Wang Juan, Zhang Pei, Kong Xue, Wang Dan 2023, 42 (4):  468-470.  Abstract ( 419 )   Aviation coolant is a combustible liquid used in aircraft engine and electronic equipment at work. It usually used in the high temperature ambient, the fire hazard of aviation coolant is often neglected in the study of oil fire risk. Therefore, sequences of experiments were conducted to study fire hazard of aviation coolant in this paper. The flash point of coolant was tested by the flash point meter and the hazard was graded. The combustion characteristics of coolant were studied based on the cone calorimeter and the basic fire parameters is obtained. The ignition time of coolant is fitted by Janssens' model and the critical ignition heat flux was obtained. Based on the thermal hazard model proposed by PETRELLA R V et al, X parameter of coolant combustion was obtained and its thermal hazard was classified. Related Articles | Metrics

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Study on fire spreading law of lithium-ion battery in storage shelf Jiang Ji, Liu Qiang, Wang Zhixing, Xie Xiaomin 2023, 42 (4):  471-476.  Abstract ( 643 )   The numerical simulation of lithium-ion battery fires in storage shelf was conducted using PyroSim software. The law of fire spread under different positions was analyzed, and corresponding fire prevention strategies were proposed. Firstly, the simulation model of the lithium-ion battery was established and verified, which was used to carry out the numerical investigation of the lithium-ion battery fires in storage shelf under different fire positions. The start time of spray, extinguishing time of fires, number of lithium-ion battery packs burned out, temperature and CO concentration were analyzed. Then, fire prevention strategies were developed based on the law of fire spread. The fire spread suppression effect of no flame baffle, flame baffles installed on the left and right sides of lithium battery pack and four sides of lithium battery pack were compared. The result showed that the lower the fire position in the four-layer shelf, the more lithium-ion battery packs burned out, and the higher the concentration of CO released in the fire. The duration of CO released was 54% more when the bottom of shelf was on fire than when the top of shelf was on fire. Among the different fire protection methods, the flame baffles installed on the left and right sides of the lithium battery pack had the best flame suppression effect. Related Articles | Metrics

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Study on the effectiveness of cryogenic cooling on the prevention and control of thermal runaway of ternary lithium-ion battery Zhang Peng, Su Jingang, Jia Boyan, Wei Liqiang 2023, 42 (4):  477-482.  Abstract ( 455 )   In order to solve the fire problem in the storage and transportation of lithium-ion batteries, a method of preventing thermal runaway of lithium-ion batteries by low temperature control was proposed, and the thermal runaway test of ternary lithium-ion batteries under low temperature cooling was carried out. The results show that low-temperature cooling can reduce the internal reaction activity of lithium-ion batteries, weaken the energy release after thermal runaway of lithium-ion batteries, and then block the chain propagation of thermal runaway between battery packs; The lower the temperature of the lithium-ion battery, the more difficult it is to have thermal runaway. When the temperature drops below -30 ℃, the directly punctured battery will not have thermal runaway; Due to the influence of low temperature, the internal material activity of the battery is reduced, the chemical reaction inside the battery is limited, and the mass loss and CO volume fraction of the battery after the test are also significantly reduced. Related Articles | Metrics

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Study on the leaking and diffusion behavior of combustible gas from oil storage tanks Chen Yanqiu, Nie Yifan, Li Tao, Chen Junmin 2023, 42 (4):  483-488.  Abstract ( 438 )   Different environmental conditions are set and the diffusion law of combustible gas for different oil types in different tank structures is studied by numerical simulation. The results show that the maximum leakage of light oil reaches 65.8 times and 48.2 times of heavy oil in fixed-roof and external floating-roof tanks, respectively. For light oil, the leakiness of fixed-top tank is much larger than that of floating-roof tank structure, and compared with fixed-top tank, the leakiness of internal floating-roof tank and external floating-roof tank is reduced by about 98% and 35% respectively.The storage safety of all three tank structures for heavy oil is relatively high. The higher the temperature is, the faster the combustible gas diffusion is, and the amount of combustible gas leakage increases by 10%, 23% and 28% at 0, 20 and 40 ℃, respectively, compared with -20 ℃. Ambient wind affects the rate of combustible gas volatilization and dilution, the greater the wind speed, the more obvious the effect, and the strongest effect of positive wind on the volatilization and dilution of combustible gas. Related Articles | Metrics

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Thermal response behavior of carbon fiber epoxy laminates at high temperature Wang Danyue, Xu Yanying, Wang Zhi, Qu fang, 2023, 42 (4):  489-494.  Abstract ( 419 )   This paper takes carbon fibre/epoxy laminate as the research object, and uses ABAQUS finite element analysis software to numerically simulate the thermal response process of carbon fibre/epoxy laminate under high temperature environment, combined with the experimental analysis of the thermal response behaviour of the material with different layer thickness, to verify the feasibility of the simulation. It is found that as the thickness increases, the time to reach the steady-state temperature is delayed and the steady-state temperature decreases, and the temperature rise rate inside the material decreases with the increase of depth from the heated surface, and the decreasing trend decreases with the increase of depth; the steady-state temperature and the steady-state thermal conductivity are greater when the heat flow direction is distributed along parallel to the carbon fibre layer than along vertical, and the distribution of carbon fibre along parallel to the heat flow transfer direction is more beneficial to heat transfer. Related Articles | Metrics

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Study on hydrogen production law of aluminum alloy processing waste when wet Liu Congcong, Xu Kaili, Wang Xue, Zheng Tingfang 2023, 42 (4):  495-498.  Abstract ( 754 )   The waste produced in the process of aluminum alloy processing has a certain risk of fire and explosion when encountering humid environment. In order to control the risk of fire and explosion during storage and transportation of alloy waste, it is necessary to study its hydrogen production characteristics. The hydrogen production of aluminum chips, oily aluminum sludge, aluminum grinding dust and aluminum-magnesium alloy grinding dust with different mass and moisture content and the influence of iron on hydrogen production of waste aluminum powder were analyzed by gas component analyzer. The results show that aluminum chips, oily sludge, aluminum polishing dust and aluminum-magnesium alloy polishing dust all have certain hydrogen production capacity in humid environment, and the smaller the particles and thinner the surface oxide layer, the easier it is to produce hydrogen. The quality and moisture content of waste are directly proportional to the hydrogen production rate; Scrap iron does not react with water to produce hydrogen at room temperature and humidity, but because of galvanic corrosion of iron, iron can promote the hydrogen production rate of aluminum processing waste, and the higher the iron content, the more obvious the promotion effect. Related Articles | Metrics

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Study on the effect of fire source positions on the smoke exhaust effect of tunnel with lateral smoke exhaust Ming Yuyang, Zhu Guoqing, Peng Min, Ding Jinhu 2023, 42 (4):  499-502.  Abstract ( 462 )   In a lateral smoke exhaust tunnel, the temperature and smoke flow are different because of the relative distance of fire location and the vents. Thus, FDS software was used to analyze the characteristics of temperature and smoke flow in the lateral smoke exhaust tunnel by changing the longitudinal location of fire sources. According to the results, the lateral vent has a cooling effect within a certain area, and the larger the smoke exhaust rate, the more obvious the cooling effect is; The farther the lateral vent from the fire, the more likely it is to be plug-holing; Increasing the smoke exhaust rate of the lateral vents can significantly reduce the longitudinal spreading distance of the smoke; Compared with the smoke exhaust rate, the fire source position has little impact on the total smoke exhaust efficiency, and only has an obvious impact on the smoke exhaust efficiency of the near vents. Related Articles | Metrics

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Experimental study on fire behaviour of stainless steel umbrella structure Shen Danyue, Zong Jinhui, Peng Lei 2023, 42 (4):  503-507.  Abstract ( 450 )   In order to study the overall response of the stainless steel umbrella structure to actual fire, two localized fire tests were carried out using a 1∶4 scale model with n-heptane pool fires at two different fire locations. The smoke temperature, the temperature and the displacement of the stainless steel members at the key positions of the model were measured. The experimental results show that the temperature field of space structure presents uneven distribution during both fire tests, and the peak smoke temperature decreases gradually from the center line of the fire source, showing an obvious gradience. The temperature rising of stainless steel member is limited and does not exceed 50 ℃, except for the joints of rods directly above and around the fire source. In the course of the two fire tests, the beams on the fire side show upward displacement, and the beams on the other side from the fire show downward displacement symmetrically, and therefore the whole umbrella frame structure tilts to the side away from the fire; Stainless steel columns are not heated uniformly, and the difference of vertical expansion displacement between fire-exposed side and unexposed side is 0.56 mm; Structural deformation affected by the location of fire sources is not significant, and the maximum displacements in the two fire scenarios are very closed. The structural deformation was basically recovered after the tests, and no permanent deformation affecting the macroscopic bearing performance of the structure was observed. Related Articles | Metrics

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Study on fire prevention measures in the middle joint area of cable tunnel based on physical test Pu Ziheng, Quan Lang, Guo Wei, Zhou Shiyi 2023, 42 (4):  508-513.  Abstract ( 458 )   In order to test the effect of fire prevention measures in the middle joint area of the actual tunnel, and further optimize the configuration, a cable tunnel to be put into operation was used to conduct physical fire test. The ignition device and data acquisition system were designed and applied in this paper. The fire development in the intermediate joint area was analyzed by monitoring images and data. Then the fire prevention and extinguishment effects under different configurations were tested and analyzed. The results show that the combustion of the simulated intermediate joint under the breakdown and fracture fault has high temperature and is easy to produce dripping melt. Under the existing protective measures, the cables around the faulty connector may still be damaged. The optimized configuration measures are as follows: The upper and lower layers of the intermediate joint area shall be equipped with fire barriers; A 4 kg superfine dry powder fire extinguishing device shall be installed at the top support where the intermediate connector is located and 1 m from both sides of the cable connector centerline; Wrap the cable within 4 meters on both sides of the cable intermediate joint with fireproof tape, which can effectively prevent the fire in the intermediate joint area. Related Articles | Metrics

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Full-scale fire experimental and evacuation simulation study of camping train Chen Hua, Xia Ying, Shu Ya, Zhang Jieyu 2023, 42 (4):  514-517.  Abstract ( 423 )   Full-scale fire experiment and evacuation simulations of camping train were carried out. Not only thermocouples were adapted to measure temperatures in both camping train and aisle, but also monitoring system was used to analyze the smoke filling process during the fire period. The temperature of fire room at 2.5 m exceeded 901.7 ℃. Based on the experimental date, STEPS was used to simulate one-direction and critical scenarios under the full occupant load of camping train. Related Articles | Metrics

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Solution of staircase on the first floor of commercial complex not directly leading to outdoor Li Xuelei, Ma Guining, Zhang Xiaojun 2023, 42 (4):  518-521.  Abstract ( 585 )   In view of the problem that the evacuation staircases on the first floor of large commercial complexes that cannot directly lead to the outdoors, this paper proposes solutions such as adopting the pedestrian street mode, setting up refuge walkways and setting up enlarged front rooms based on engineering practice. Taking a large commercial complex as an example, the problem that the evacuation staircase on the first floor that cannot directly lead to the outside is analyzed and researched, an optimization scheme is proposed, and the feasibility of the scheme is judged by numerical simulation software. This paper provides reasonable suggestions for the architectural design of large commercial complexes, and also provides references for the fire protection design of similar projects. Related Articles | Metrics

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Study on smoke flow characteristics of rectangular tunnel under train blocking Liu Jianchun, Xiao Niqi, 2023, 42 (4):  522-525.  Abstract ( 424 )   In order to study the smoke movement characteristics under the condition of metro train obstruction in rectangular tunnel, this paper uses FDS to analyze the smoke spread, temperature distribution and critical velocity change in rectangular tunnel under the two working conditions. The results show that when there is no train blockage, the distance between the fire source and the tunnel ceiling is large, the effect of space height on flame combustion is not obvious, and the plume affected by buoyancy appears; When there is train blockage, there will be linear plumes on both sides blocked by the car roof. When there is no train blockage, the maximum smoke temperature is located above the fire source, and the two sides of the fire source decrease in turn; When the train is blocked, the high temperature zone is always located on both sides of the tunnel roof, and the temperature on the left side of the tunnel roof is slightly higher than the temperature on the right side of the tunnel roof due to the arc structure. When the heat release rate is not greater than 7.5 MW, the critical wind speed is positively correlated with it; When the heat release rate is greater than 7.5 MW, the influence of the critical wind speed on the heat release rate gradually decreases; The critical wind speed will decrease with the increase of blocking ratio. Therefore, the best effect can be achieved by accurately detecting the train stop position and optimizing the ventilation and smoke exhaust mode. Related Articles | Metrics

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Numerical modeling of firefighting foam spread over horizontal solid surface Bao Youquan, Wang Lu, Zhi Huiqiang, Du Xia, 2023, 42 (4):  526-530.  Abstract ( 426 )   The mathematical model and numerical method of firefighting foam spread over horizontal solid surface were established, and the transient process of firefighting foam spread over horizontal solid surface and the influence of initial boundary conditions and foam rheology on the foam spreading process were analyzed. The results show that, as the foam layer spreads downstream, the advancing speed of the foam front decreases, and the attenuation amplitude decreases gradually. The rheological behavior of firefighting foam directly determine the vertical position of the yield surface in the foam cover and the shear rate in the yield area, which in turn affects the foam spreading process. The lower yield stress, higher consistency coefficient, and larger flow behavior index of firefighting foam are favorable for foam spreading, resulting in an increase in the spreading distance of the foam layer in a given time, a decrease in the distribution gradient of the foam layer thickness along the horizontal direction, and an increase in the yield area within the foam layer. Related Articles | Metrics

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Study on calculation model of pipeline pressure drop for carbon dioxide fire extinguishing system Wu Pengzhi, Liu Changchun, Wen hu, Yan Jie 2023, 42 (4):  531-536.  Abstract ( 474 )   Against the problem of current GB 50193-93, Code for Design of Carbon Dioxide Fire Extinguishing System only calculate the pressure drop of high pressure (5.17 MPa) and low pressure (2.07 MPa) system pipelines, and the influence of heat transfer on the pipe wall is not considered, this paper builds a one-dimensional homogeneous flow calculation model for the pipeline pressure drop of carbon dioxide fire extinguishing system, establishes the calculation formula of Y and Z coefficients under different system pressure conditions, and VBA code was use to realize the rapid calculation of pipeline pressure drop under different system pressure conditions. The accuracy of the model was verified by comparing with the national standard calculation results and experimental measurement results. The new model was used to quantitatively analyze the effects of frictional resistance coefficient, mass flow rate, elevation difference, and ambient temperature on the pressure drop. It was found that the lower the system initial pressure, the bigger the influence of the frictional resistance coefficient, mass flow rate and elevation difference, and the change of temperature has little effect on the pressure drop and can be basically ignored. Related Articles | Metrics

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Research on atomization characteristics of marine fire fighting pressure swirl nozzle Hu Yahui, Zhang Xian, Hu Xucai, Li Jun 2023, 42 (4):  537-541.  Abstract ( 409 )   In order to improve the fire safety of ships during navigation, the theoretical model of pressure swirl nozzle was established according to its structural type and working principle. The external droplet atomization characteristics were analyzed by the combination of experiment and numerical simulation, and the effects of inlet pressure, nozzle outlet diameter and swirl chamber length on atomization particle size and atomization cone angle were analyzed. The results showed that the atomization particle size decreased with the increase of the inlet pressure and the length of the swirl chamber, and increased with the increase of the outlet diameter; the atomization cone angle became larger with the increase of the inlet pressure and the outlet diameter, and decreased with the increase of the swirl chamber length. Box-Behnken test was designed and CFD simulation was performed to obtain the influence law of atomization cone angle and atomization particle size by response surface method. Related Articles | Metrics

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Design and implementation of psychological adaptability training system based on VR technology Tang Huaqing, Xin Bocheng, Zhao Jindao, Du Yusong 2023, 42 (4):  542-545.  Abstract ( 430 )   In order to improve the psychological quality of emergency rescue personnel, the psychological adaptability training contents under the conditions of high altitude, fire, earthquake and other scenes are set up, and the overall design of the system is analyzed from the perspective of the overall structure, functional modules and implementation process design of the system. At the same time, taking the high altitude psychological adaptability training course as an object, the process of system development and implementation using unity, Revit 2020 and other technologies is described from the aspects of development environment selection, scene design and introduction, key technology implementation, training assessment, system release, etc. This training method can effectively make up for the shortage of psychological training for emergency rescue personnel, and also provide a reference for the further application of VR technology in the field of emergency rescue training. Related Articles | Metrics

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Research on smart fire helmet system based on Kalman filter Zhao Mengxuan, Zhao Qi, Lv Zhanbo, Liu Guoning 2023, 42 (4):  546-549.  Abstract ( 459 )   In order for firefighters to accurately understand the fire situation, we design a smart helmet system based on kalman filter which has integrated the microcontroller system, gas sensors, temperature sensors, wireless communication module, anomaly wearing detection module and alarm module, and the system design consists of the design of software system and hardware system. The hardware system takes the STM32 microprocessor as the core, and wireless GPS module is adopted together with inertial navigation module for the purpose of higher positioning owing to their compensation effects. And it also includes an environmental information acquisition sensor. On the software, the Kalman filtering algorithm is applied to process the collected data, which reduces the influence of sensor delay and noise on the system measurement, so as to achieve accurate prediction of the system state，and the monitoring system software was verified. At the same time, the attitude detection algorithm realizes the accuracy of the firefighter state identify. This paper also conducts an ergonomic analysis of the intelligent fire helmet, and integrates the various components on the helmet. After testing, the system runs stably and has high accuracy. Related Articles | Metrics

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Research on intelligent electrical fire monitoring based on residual current waveform characteristics Men Maochen, Du Yujia, Xu Mingming, Wu Huanzhao 2023, 42 (4):  550-555.  Abstract ( 431 )   The fixed residual current effective value is used by the residual current electrical fire monitoring system as the early warning criterion of electrical fire, and there are great safety risks because of frequent false alarms in the process of using it. In this paper we built an electrical fire experiment platform to extract the residual current waveforms of normal operation and earth fault under different loads, and proposed a method by using the characteristic quantity of residual current waveforms to warn electrical fire. Wavelet transform is used to filter the original residual current signal and extract the low-frequency component. The fault feature vector is formed from the time-domain characteristics and waveform characteristics of the low-frequency component, and it's used to train BP neural network. Through intelligent algorithms automatically identify faults, the accuracy of residual current fire warning is improved. Related Articles | Metrics

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Analysis and optimization of fire extinguishing performance of drainage type forest fire robot Yang Chunmei, Liu Tongbin, Wang Cheng, Liu Jiuqing 2023, 42 (4):  556-562.  Abstract ( 431 )   A drainage type forest fire fighting robot was designed for the problem that fire extinguishing equipment cannot be fully adapted to the forest fire extinguishing conditions in China. It was modeled in three dimensions by Solidworks, and the fluid simulation of the diversion duct was carried out by Fluent to analyze the influence of the diameter D3 of its third fire extinguishing wind cylinder, the nozzle position S0 and the convergence angle θ1 of the convergence chamber on the fire extinguishing performance; the influence of the interaction of the three on the fire extinguishing performance was further analyzed by ANSYS and MATLAB software, and performance comparison test was conducted between the prototype and the 6MF-32 portable wind-operated fire fighting robot. The results show that the optimal solution of wind cylinder size is S0=-20 mm, D3=110 mm and θ1=15°, and the fire extinguishing efficiency of this design is higher compared with 6MF-32 under the optimal structure parameters, which helps forest firefighting better. Related Articles | Metrics

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Study on potential surface fire behavior and transition ratio to crown fire of Platycladus orientalis stands in Beijing Xishan Bai Haifeng, Niu Shukui, Liu Xiaodong 2023, 42 (4):  563-567.  Abstract ( 443 )   Taking Platycladus orientalis stands in the farm as research object, the characteristics of selected stands were investigated, and the physical and chemical properties of fuels were measured by tests; the plots were classified into several major types by systematic clustering; the BehavePlus software was used to customize fuel model, and then the effect of different wind speed, slope and fuel moisture on surface fire behavior characteristics of Platycladus orientalis stands and the transition ratio of different types of sample plots were investigated. The results showed that through systematic clustering, the Platycladus orientalis stands were divided into three types, and the stand factors of different types differed greatly; surface fire spread rate, fireline intensity and flame length were significantly positively correlated with 10 m wind speed and slope, and negatively correlated with fuel moisture, and heat productivity per unit area was negatively correlated with fuel moisture; the transition ratio and 10 m wind speed were significantly positively correlated, while negatively correlated with fuel moisture. In this paper, the potential surface fire behavior and transition ratio from surface fire to crown fire of different types of Platycladus orientalisstands differed greatly, which could provide a scientific basis for forest fire prevention and suppression and effective allocation of fire prevention resources in the study area. Related Articles | Metrics

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Three-dimensional combustibility study of eight tree species in central Liaoning Yang Hanwei, Xu Yanying, Wang Zhi, Li Zhonghao, 2023, 42 (4):  568-572.  Abstract ( 421 )   In this paper, the leaves and twigs of eight typical tree species in central Liaoning were selected as the research objects. The electric blast drying oven and cone calorimeter were used to measure 11 indexes affecting their combustibility. The indexes were classified from three characteristic dimensions of ignitability, intensity and persistence, and the three-dimensional combustibility evaluation was carried out by grey correlation analysis. The results showed that the water loss efficiency of the combustible materials of leaves and twigs increased with the heating time. The heat required for igniting leaves was much greater than that of twigs. The moisture content of coniferous species was larger, and the leaves were more flammable than twigs. The intensity and persistence of the eight trees were positively correlated, and the correlation between ignitability and intensity was weak. The comprehensive combustion activity of Pinus tabulaeformis, Betula betula, Quercus mongolica, Pinus huasanensis, Cottonwood, Ash, Cotinus and Ginkgo was weakened successively. Related Articles | Metrics

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Analysis and research on influencing factors of monthly distribution of fire alarm frequency in super large cities Chen Yongsheng, Qian Gurong, Shi Nan, Zhong Zhaoning 2023, 42 (4):  573-576.  Abstract ( 442 )   Based on the monthly fire alarm data of super large cities, combined with the relevant data of climate, economy and so on, this paper constructs the influencing factor model of the monthly distribution of the number of fires, and analyzes the explanatory power of climate and economic variables on the occurrence of fires through the negative binomial regression of counting data. The results show that on the premise of controlling calendar factors, the combination of independent variables of rainfall days and total industrial output value has a good explanatory power for the monthly fire alarm times, and the data of temperature, electricity consumption and so on are less important for the fire alarm number. Under the condition that other variables remain unchanged, the fire alarm decreases by 2.1% for each additional day of rainfall; For every 100 million yuan increase in the total industrial output value, the fire alarm will increase by 0.033%; For every increase in the number of holiday, the fire alarm will increase by 2.4%. Related Articles | Metrics

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Database construction and application of hazardous chemical explosion and fire accidents Li Guangyao, Sun Zhenwen, Zhu Jun, Zhang Guannan 2023, 42 (4):  577-581.  Abstract ( 518 )   In order to study the laws of hazardous chemical explosion and fire accidents, we built the database frame based on material information. About 600 explosion and fire accidents of hazardous chemicals from were collected, based on which, a MySQL structured database was established to manage seven aspects of information, such as material information, hazardous substances, process equipment, space-time information, accident performance types, accident occurrence links and accident hazards. The temporal and spatial information law, link distribution law, high-frequency accident equipment and high-frequency hazardous substances of dangerous chemical explosion and fire accidents have be analyzed. It’s found that dangerous chemical explosion and fire accidents occur frequently and even increase, especially reaching a high point in the period from 2014 to 2015, and then began to decline. The accident occurred mainly in the eastern coastal area, of which Shandong and Jiangsu provinces were the most serious. The number of accidents and casualties in the production of hazardous chemicals are the most significant, which should be paid attention to. The frequency of dangerous substances is the highest among oil and gas, explosives and nitrobenzene, and the dangerous substances have obvious regional differences. Related Articles | Metrics

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Exploring the fire safety management by fire investigation of "small fire causing death" Jin Wei 2023, 42 (4):  582-584.  Abstract ( 493 )   Through the investigation of three residential "small fire causing death" accident, this paper carried out the analysis of fire inducements accurately, analyzed the problems exposed by the "small fire causing death" accident systematically, accurately study and analyze the fire characteristics of the "small fire causing death" accident and the shortcomings of grass-roots fire protection work. Put forward work suggestions, and explored the deep control of fire safety management. In points of fire investigation, extended survey, fire cause analysis and countermeasures, suggestions on improving the fire safety management were put forward, and the construction of grass-roots fire control system was explored. Related Articles | Metrics

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Research and application of fire rescue intelligence text summarization based on BERT Li Jibao, Dong Tingting, Guan Siqi, Wan Zijing, 2023, 42 (4):  585-588.  Abstract ( 431 )   For solving the problems of the current fire information system, such as the complexity of information sources and the dependence of classification and interpretation on expert experience, this paper presented an automatic text summarization method to realize the auxiliary analysis of fire rescue text. On the basis of optimizing the fire rescue information dataset, the method contained an adopted pre-training BERT_WWM model, for extracting the word vector representation with context semantics, and used the Transformer to extract the summary sentence, so as to further improve the effect of fire information summary extraction. Through experiments in ROUGE-1, ROUGE-2 and ROUGE-L, our BERT_WWM + Transformer method was slightly improved comparing with other existed methods. Even the subjective evaluation could partially prove the purpose of extracting key information from texts, and showed that our method supported an available automation tools for intelligence analysis. Related Articles | Metrics