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15 March 2022, Volume 41 Issue 3 Previous Issue    Next Issue

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Research on suppression of polypropylene dust explosion by melamine polyphosphate WANG Bao1,2, JIANG Bing-you1,2, SU Ming-qing3, YANG Bing-hui1,2 2022, 41 (3):  291-295.  Abstract ( 1828 )   The explosive characteristics of polypropylene (PP) dust and the restraining effect of melamine polyphosphates (MPP) on polypropylene dust explosion were studied by using a 20 L spherical explosive device. The results show that the explosive strength of polypropylene dust with the mass concentration of 300 g/m3 is the highest, the maximum explosive pressure is 0.746 MPa, the maximum explosive pressure rising rate is 60.508 MPa/s, and the maximum explosive index is 16.398 MPa·m/s. With the increase of the mass fraction of MPP powder, the maximum explosion pressure, the rate of increase of the maximum explosion pressure and the explosion index of polypropylene dust decreased continuously. When the mass fraction of MPP powder in the mixture is 70%, the explosion of polypropylene dust with a mass concentration of 300 g/m3 is completely inhibited. Thermogravimetric analysis showed that the addition of MPP powder increased the decomposition temperature and thermal stability of polypropylene. Combined with the test results of thermal analysis, the explosive suppression mechanism of MPP powder was discussed, and the analysis showed that MPP powder had physical and chemical inhibition effects. Related Articles | Metrics

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Experimental study on the effect of particle size on dust explosion characteristics of medium density fiberboard WU Jia-meng1，PANG Zi-zheng1，ZHU Shun-bing1,2，DUAN Yi1 2022, 41 (3):  296-299.  Abstract ( 1575 )   In order to explore the effect of particle size on dust explosion and related characteristics of medium density fiberboard, 20 L explosion ball, minimum ignition temperature device of dust cloud, cone calorimeter and Hartman tube device were used to study the lower explosion limit concentration, maximum explosion pressure, minimum ignition temperature, heat release rate and flame propagation law of dust with different particle sizes. The results show that with the decrease of dust particle size, the lower explosion limit concentration and minimum ignition temperature decrease, and the maximum explosion pressure increases gradually; The dust combustion process is divided into five stages: temperature rise, ignition, transition, intensification and extinction, and there are two peaks. The change time and heat absorption time of heat release rate increase with the decrease of particle size, and the peak value of heat release rate increases; With the decrease of particle size, the propagation of flame in the pipe first increases and then decreases, the shape of "fireball" outside the pipe is larger, the number of sparks decreases after the flame dissipates, and the tail end of the flame is more slender. Related Articles | Metrics

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Study on combustion characteristics of composite soft oil tank WANG Chun-hui, JIANG Xin-sheng, YU Bin-bin, CAI Yun-xiong 2022, 41 (3):  300-303.  Abstract ( 1548 )   In order to study the combustion characteristics of field combined soft oil tank under different radiation intensities, the combustion experiments of soft oil tank samples were carried out by cone calorimeter. Three typical heat radiation intensities of 25, 35 kW/m2 and 50 kW/m2 were selected, and the data of ignition time, heat release rate, specific extinction area, smoke generation rate and flame shape were obtained. The results show that when the thermal radiation intensity is 50 kW/m2, the ignition time is 38% and 53% that of 25 and 35 kW/m2, respectively; The maximum heat release rate is 1.4 times and 1.7 times that of 25 and 35 kW/m2 respectively, and the time to reach the peak is reduced by 15% and 40% respectively; The maximum flue gas generation rate of combustion is 1.4 and 1.8 times that of 25 and 35 kW/m2 respectively; After combustion, the mass of remaining carbon layer is reduced by 1/3 and 1/2 respectively. Related Articles | Metrics

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Ignition characteristics of finite thick PMMA exposed to thermal radiation ZHU Zhi-xuan, GONG Jun-hui 2022, 41 (3):  304-309.  Abstract ( 1579 )   Influence of sample thickness and four prescribed constant heat fluxes on surface temperature, mass loss rate, ignition time and critical temperature of clear PMMA (Polymethyl Methacrylate) was investigated. Inversing modelling was utilized incorporating experimental measurements to determine the thermodynamics and kinetics of PMMA, which were employed as inputs of the numerical model to simulate the other scenarios. Accuracy and reliability of the numerical model were verified by comparing with experimental results and analytical correlations. The results showed that the declining rate of the ignition time decelerates with increasing heat flux. When the thickness of PMMA was less than 3 mm, the surface temperature and mass loss rate decrease with increasing thickness. As the thickness gets larger than 3 mm, the average ignition temperature was （628±20） K, and no sensible dependency on thickness was detected, indicating that the ignition temperature can be employed as ignition criterion. Related Articles | Metrics

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Study on the characteristics of external overpressure induced by vented hydrogen deflagrations CHEN Ye, LI Yi, LI Zi-ting, JI Chao 2022, 41 (3):  310-315.  Abstract ( 1664 )   The existing researches mainly focus on the development of internal pressures in the confined space during hydrogen explosions, and the studies about the distribution law and evolution mechanism of external overpressure during vented hydrogen explosions are still not enough. Therefore, a commercial FLACS was used to establish the numerical model of the chamber, the vent size was increased to 3.14 m2 and the maximum hydrogen concentration was increased to 30%, then numerous simulations were conducted to study the formation of the external explosion, the distribution rule of the external overpressure and the hazard scope. The effect of factors on the external overpressures during vented hydrogen deflagrations was also analyzed. The results show that when the vent size becomes relatively large, the vented hydrogen deflagration will lead to the formation of the external combustible gas cloud with a larger volume. Then the cloud is ignited by the emerging flame to produce an external explosion, and the whole formation process of the external explosion can be effectively simulated by FLACS. When the vent size is large, the maximum overpressures at different positions exhibit monotonic behavior as hydrogen concentrations increase, but a non-monotonic behavior of the change rate of overpressure between different positions near the vent opening as a function of hydrogen concentration is found. For the different ignition locations, maximum overpressures near the vent opening are distributed in different shapes of wedge, but the distribution modes of the hazard scope are totally different, the external overpressure and hazard scope with the back ignition are larger than those with the center ignition. Related Articles | Metrics

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Study on stable detonation tests of in-line flame arresters LI Hou-da1,2, HU Bo1,2, LAN Zheng-gui1,2, HE Chun-hong1,2 2022, 41 (3):  316-318.  Abstract ( 1597 )   In this paper, 20 groups of stable detonation flame arrest tests were carried out in accordance with the international standard ISO 16852:2016, 10 groups had no accelerated rings and 10 groups had accelerated rings. The results show that it is easier to form stable detonation when the accelerated ring is used as the flame accelerator, and the average flame velocity and pressure are relatively stable, and the repeatability is higher in a certain range. In stable detonation tests of in-line flame arresters, it is recommended to use the accelerated ring as the flame accelerator. Related Articles | Metrics

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Experimental study on fire suppression of ternary lithium-ion battery by water mist with additive WANG He1,2, ZHU Shun-bing1,2, ZHANG Yu-hang1,2 2022, 41 (3):  319-324.  Abstract ( 1753 )   Through self-built lithium-ion battery combustion and fire extinguishing platform, taking the ternary lithium nickel cobalt manganese oxide battery as the research object, the fire test of ternary lithium-ion battery by water mist with additive was carried out, the mechanism and effect of solution fire extinguishing were analyzed comprehensively from the aspects of solution surface tension, battery maximum temperature and cooling rate, etc. In the test, the heat abuse method was selected, and a heating furnace was used to heat the ternary lithium-ion battery to cause thermal runaway combustion, and a high-definition camera recorded the whole process. Six kinds of additives including sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, sodium chloride, potassium chloride, ammonium dihydrogen phosphate and carbonamide were selected for single and compound solution water mist fire extinguishing test. The surface tension of each solution was measured, and its change with the concentration of the solution and its influence on the fire extinguishing performance were analyzed. It was found that the surface active agent could reduce the surface tension of the solution, thereby improving the atomization effect of water mist.When the surfactant tends to be saturated, the surface tension of the solution remains basically stable. A K-type thermocouple was used to measure the temperature during the thermal runaway of the ternary lithium-ion battery and the water mist fire extinguishing process, and the measured characteristic parameters such as the highest temperature and cooling rate of the battery were compared and analyzed. The result shows that, compared with pure water mist, the fire extinguishing performance of the additive-containing water mist is improved greatly in atomization effect, diluted oxygen concentration, and blocking the combustion reaction chain, and the battery does not reignite.The best mass fraction of single additive water mist with sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, sodium chloride, potassium chloride, ammonium dihydrogen phosphate, and carbamide to suppress the fire of ternary lithium-ion battery is 1.5%, 1%, 8%, 10%, 10%, 0.3% respectively. Compounding on this basis, it was found that the single extinguishing effect of potassium chloride and ammonium dihydrogen phosphate was better than the combined solution, the fire extinguishing effects canceled each other out. Coordination of surfactants, alkali metal salts and three additives that are easily decomposed by heat can improve the fire extinguishing efficiency effectively, the mixed solution of sodium dodecyl benzene sulfonate (1.5%), potassium chloride (10%) and ammonium dihydrogen phosphate (10%) had the best fire-extinguishing effect. The compound solution works synergistically through various mechanisms such as reducing the surface tension of the solution, reducing the particle size of fine water mist droplets, and combining ionized metal ions with free radicals in the combustion chain, absorbing a large amount of heat, thereby obtaining better fire extinguishing effect.The article carried out relevant experiments on the suppression of thermal runaway fires in ternary lithium-ion batteries with fine water mist containing different additives. In future research, more additives of different types and concentrations can be selected for compounding experiments considering fully from the perspective of high efficiency and environmental protection, and the advantages and disadvantages of various fire extinguishing agents, to provide support for lithium-ion battery fire protection technology. Related Articles | Metrics

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Experimental analysis of mechanical properties and microstructure of tunnel lining concrete after fire XU Jun-tao1, WANG Qiang1, ZHU Kai1, HUANG Ya-dong2 2022, 41 (3):  325-329.  Abstract ( 1531 )   In order to study the damage degree and performance characteristics of the tunnel lining structure after the fire, the compressive strength test and ultrasonic inspection of the tunnel lining concrete after the fire were carried out, and the residual resistance and the law of pressure intensity and speed of ultrasonic sound of the tunnel lining concrete under different fire time (2,3,4 h) was analyzed. The results show that: in the range of 200~800 ℃, under different fire time, the fire temperature and residual compressive strength, ultrasonic sound velocity and residual compressive strength have a good linear relationship, and with the increase of fire time, the ultrasonic sound velocity and compressive strength gradually decrease; Scanning electron microscopy-SEM shows that there is a good correlation between fire temperature, residual compressive strength and ultrasonic sound velocity. In addition, three calculation models of tunnel lining concrete compressive strength, fire temperature, and ultrasonic sound velocity in the range of 200~800 ℃ under different fire time have been established. Related Articles | Metrics

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Study on longitudinal temperature distribution of spill fire plumes along sloped facade wall of building fires ZHANG Xiao-chun1, CHENG Zhang-kun1, WU Bin-bin2, CHEN Qin-pei3 2022, 41 (3):  330-333.  Abstract ( 1603 )   Building fire is one of the most important research fields in fire science, and the temperature distribution of the spill plume along the facade is very important for the risk assessment and prevention design of the building. Although many scholars have studied the vertical temperature distribution of spill plumes on vertical facade, there are few studies on temperature distribution along sloped facade. This paper aims to reveal the characteristics of longitudinal temperature distribution of spill plumes along the sloped facade in building fire, and establishes a predicted correlation for the temperature distribution along sloped facade. Based on Froude similarity theory, a 1∶2 medium-scale-combustion chamber was built in the FDS to carry out numerical simulation research. The validation of the numerical model was confirmed through mesh sensitivity test and the comparison with experimental data. The dimensions of the combustion chamber were 3.78 m2.36 m1.6 m. A variable-angle concrete slab (2.36 m in length and 7.55 m in height) was installed above the opening of the combustion chamber to simulate the facade of the building. To investigate the temperature distribution of spill plumes along sloped facade wall, a total of 64 scenarios were considered with 4 different dimensions of rectangular openings(0.52 m0.65 m, 0.78 m0.52 m, 0.78 m0.65 m, 0.78 m0.78 m), 4 different facade wall angles (0°,10°,15°,20°) and 4 different heat release rates respectively. It is found that: (1) When the dimension of the openings and the heat release rates are constant, the temperature along the sloped facade (θ＞0°) is significantly higher than that along the vertical facade at the same measurement point (θ=0°). (2) When the angle of facade wall is set as 20°, the temperature at the same measurement point in the plume region is the highest among the four designed angles. (3) When the angle of facade wall is less than 20°, the temperature at the same measurement point gradually increases with the angle of the facade θ. (4) When the dimension of the openings and the angle of facade are the constant, with the increase of heat release rates, the maximum temperatures of the spill plume is almost constant. For further research on spill fire plume temperature distribution characteristics of sloped facade, the Z-Zn in classical theory is modified by 1+sinθ. It is found that the spill plume temperatures of the same opening dimension and heat release rate with different angles of facade wall collapse well. Based on these results, a predicted correlation of the temperature along the sloped facade is established, whose facade wall angles are in the range of 0<θ<20°.The results in this paper are based on the sloped angle between 0° and 20°. It needs to be further studied that whether the temperature distribution of spill plume conforms to this law when the sloped angle is greater than 20°. Related Articles | Metrics

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Study on fire smoke spread characteristics of an indoor commercial pedestrian street HU Lang1, CHEN Jian2 ,WANG Hai-Yan1, ZHANG Bing-Sen1 2022, 41 (3):  334-338.  Abstract ( 1584 )   In order to study the fire smoke control effect of indoor commercial pedestrian street, taking an urban complex as an example, simulate the fire of indoor commercial pedestrian street, set a 1.5 MW alcohol fire source in the atrium, start the smoke exhaust facilities and manually start the natural smoke exhaust facilities respectively after ignition, observe the smoke spread in the indoor pedestrian street under two working conditions, and measure the temperature and other parameters in the test area. It was found that compared with the natural smoke exhaust at the top, under the mechanical smoke exhaust condition, the smoke settlement rate is 17% lower, the height of the smoke layer is 11% higher, the temperature field in the smoke plume is basically the same, the average temperature is about 61 ℃, the temperature of the top smoke layer is 4.7% higher, and the horizontal spread rate of the smoke is 41.6% faster under the suction of the fan. Related Articles | Metrics

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Research on the efficiency of smoke exhausting with diverse air make-up ways in atrium subway station DUANMU Xiang-ling， ZHAN Zi-na， LI Lei，SONG Yun-long 2022, 41 (3):  339-342.  Abstract ( 1600 )   In order to make the smoke exhausting efficiency of the atrium subway station higher, the influence of different air make-up ways was studied. In this paper, the numerical simulation analysis method is used to analyze the influence of different air make-up ways and volumes on the smoke exhausting efficiency under different scenarios as natural air supplement and mechanical air supplement in station hall or platform. The research shows that when the smoke exhausting volume in station hall is certain, the smoke exhausting efficiency is the highest by using the platform mechanical air make-up. And when the air supplement volume is between 30% and 50%, the best smoke exhausting effect can be achieved. Related Articles | Metrics

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Research on the efficiency of smoke exhausting DUANMU Xiang-ling， ZHAN Zi-na， LI Lei，SONG Yun-long 2022, 41 (3):  343-346.  Abstract ( 1628 )   In order to make the smoke exhausting efficiency of the atrium subway station higher, the influence of different air make-up ways was studied. In this paper, the numerical simulation analysis method is used to analyze the influence of different air make-up ways and volumes on the smoke exhausting efficiency under different scenarios as natural air supplement and mechanical air supplement in station hall or platform. The research shows that when the smoke exhausting volume in station hall is certain, the smoke exhausting efficiency is the highest by using the platform mechanical air make-up. And when the air supplement volume is between 30% and 50%, the best smoke exhausting effect can be achieved. Related Articles | Metrics

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Research on indoor fire path query method for multiple constraints QI Tong-hua, ZHOU Xiao-ping, WANG Jia 2022, 41 (3):  347-351.  Abstract ( 1580 )   In current studies, scholars usually only consider a single constraint condition of shortest path in the research of fire path planning, and do not consider the impact of multiple constraints on path query, which brings some limitations to the evacuation. This paper will study the indoor fire path query method based on a variety of constraints, that is, integrating distance constraints, number constraints of fire-fighting facilities and number constraints of dangerous areas. Extract the data and fire information in the indoor mixed road network through BIM technology, and build the comprehensive fire road network data; then through the design function, adjust the coefficients in the function, determine the fire comprehensive road network under the specific multiple constraints, and then call the Dijkstra algorithm to generate K paths satisfying multiple constraints, and provide more path selection for evacuation, so that the fire path is more humane and personalized. Finally, the feasibility and practicability of the proposed method are verified by experiments and three-dimensional display. Related Articles | Metrics

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Study on heat distribution of ship cabin fire under different ventilation conditions REN Jing-min1, ZHU Xiao-jun2, YAO Yuan1, LIN Hua1 2022, 41 (3):  352-355.  Abstract ( 1542 )   Based on a full-scale cabin fire test , according to the law of energy conservation, this paper quantitatively analyzes the specific gravity relationship of heat diffusion in the process of fire under different ventilation conditions, such as bulkhead temperature rise, heat transfer to surrounding compartments by radiation and convection, and heat transfer of high-temperature flue gas. The results show that under this test condition, the high-temperature flue gas diffusion and bulkhead temperature rise occupy the main part, while the maximum heat diffusion from the bulkhead to the adjacent compartment is less than 10%. Related Articles | Metrics

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Application and analysis of a flame retardant treatment method for wood structure buildings ZHENG Jin1,2， ZHU Guo-qing1，TONG Yu3, MENG Fan-mao4 2022, 41 (3):  356-358.  Abstract ( 1591 )   This paper introduces the full scale fire test process of ordinary wooden structure room and wooden structure room treated by vacuum pressure impregnation flame retardant method, and obtains the test results of better fire resistance of wooden house treated by vacuum pressure impregnation flame retardant method. Based on the test results, this paper discusses the application of vacuum pressure impregnation flame retardant method in the construction of a new antique wood structure buildings project and the relevant protective surface practices, and obtains the conclusions that the flame retardant liquid has strong permeability to wood components and panels under the condition of vacuum pressure impregnation flame retardant method, and strict construction technology should be observed in the construction process, etc.. Related Articles | Metrics

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Comparative study on calculation of fire resistance of steel structure based on code and numerical simulation DONG Qing 2022, 41 (3):  359-362.  Abstract ( 1586 )   Key requirements of GB 51249-2017, Code for Fire Safety of Steel Structures in Buildings was interpreted, and comparative study on calculation of fire resistance of steel structure based on code and numerical simulation was conducted. The results showed that: code has good feasibility to steel members under fire with three or four sides in statically determinate structures; for steel members under fire with three or four sides in statically indeterminate structures, the applicability needs further study. Related Articles | Metrics

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Fire safety assessment for underground commercial complexes ZHANG Li-ning1, GOU Peng-fei2, AN Jing3, CUI Cai-yun1 2022, 41 (3):  363-366.  Abstract ( 1622 )   According to the characteristics of underground commercial complex fire, this study obtains and establishes a fire risk assessment index system of urban underground commercial complex, including 20 evaluation indexes by using the method of literature investigation. Then, aiming at the uncertainty of urban underground commercial complex fire, the uncertainty measurement theory is introduced, the urban underground commercial complex evaluation model based on uncertainty measurement is constructed, and the index weight of each evaluation index is determined by using entropy weight theory. Finally, taking the fire risk assessment of an urban underground commercial complex as an example, an empirical analysis is carried out. The results show that this method can be used to evaluate the fire safety level of urban underground commercial complex, and the research can provide new ideas for fire prevention and emergency management of urban underground commercial complex. Related Articles | Metrics

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Fire hazard evaluation of phenolic resin/glass fiber aircraft cargo lining composite material YANG Xiao-guang1, JIA Xu-hong1,2, XU Song-tao1, MA Jun-hao1 2022, 41 (3):  367-370.  Abstract ( 1638 )   Cone calorimeter and smoke density box were used to test and analyze the combustion characteristics of aircraft cargo compartment liners in different fire environments, and the fire hazard of glass fiber/phenolic resin composites was evaluated based on the experimental data of cone calorimeter. The results show that different heat radiation intensities have different effects on cargo tank linings. The greater the heat radiation intensity, the faster the thermal decomposition, the shorter the ignition time, and the greater the peak heat release rate. The maximum peak value is 98.5 kW/m2, and the maximum total heat release is 7.7 MJ/m2, and the maximum total smoke production is 0.8 m2, and the mass loss is greater. Under the same heat radiation intensity, the specific optical density of the A320 cargo tank lining composite material under flaming combustion is 2.39, and the maximum specific optical density is 16.06 in the case of flameless combustion. Combined with the CONE test data, four fire risk evaluation indicators, FGI, FPI, THRI and TSPI are calculated. FPI is inversely related to the thermal radiation intensity, and FGI, THRI and TSPI are all positive related to the thermal radiation intensity. Related Articles | Metrics

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Fire safety evaluation of warehouse based on Pythagoras-TOPSIS XUE Zhi-heng, CHEN Xin, LIU Ren-jie 2022, 41 (3):  371-374.  Abstract ( 1598 )   In order to evaluate the fire safety level of the warehouse more scientifically, this paper constructs the fire safety evaluation system of the warehouse, and uses the Pythagoras combined with TOPSIS safety evaluation method to analyze. DEMATEL method is used to determine the factors to determine the influence degree between each attribute weights. The processing for the Pythagorean fuzzy set is simplified by scoring function. Projection is used to determine the expert weights.After attributing weight and expert weight correction of data in combination with TOPSIS analysis, the fire safety level of each warehouse was evaluated. Through the instance, the feasibility of this method is verified. Related Articles | Metrics

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Evaluation and layout optimization of combustible gas detector coverage in a tank farm MU Yun-tao1,2, ZHANG Jie-dong1,2, WANG Ya-zhen1,2, KANG Ze-tian1,2 2022, 41 (3):  375-378.  Abstract ( 1582 )   Liquefied hydrocarbon is a Class A fire hazard liquid. Once it leaks, it will cause serious consequences when encountering the ignition source. In order to effectively prevent the gas leakage of liquefied hydrocarbon storage tanks, this paper takes a petrochemical liquefied hydrocarbon tank farm as an example, using FLACS software to simulate the leakage of liquefied hydrocarbon and the distribution of flammable vapor clouds. The gas detector layout plan is evaluated, and an optimized plan is proposed. The results show that the coverage rate of combustible gas detectors under the original layout plan is 46.88%, the optimized arrangement of combustible gas detectors for liquefied hydrocarbon tank farms has a 1ooN coverage rate of 96.87%, which can provide technical support for early warning of leakage accidents. Related Articles | Metrics

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Study on model experiment and numerical WU Qian-yun, XU Shu-hui, MA Bo-yang,XU Rong-ji 2022, 41 (3):  379-384.  Abstract ( 1549 )   In order to study the accumulation of gas near the fire door and the mezzanine of tunnel when gas leaks in the utility tunnel, an experimental study was carried out on the model test bench with neon gas instead of gas. Numerical simulations were also used to verify the feasibility of neon gas instead of gas. It is proposed to add fire-proof air outlets at the highest point of the utility tunnel firewall and to install inducing fans on the mezzanine of tunnel. And the improvement effect of gas accumulation under this method was simulated. The results show that when the leak is located on the upstream side of the fire door, gas accumulation occurs in the upper part of the upstream and downstream near the fire door. The increase in the diameter of the leak aggravates the accumulation of gas. The higher the gas pipeline pressure is, the higher the gas leakage concentration and diffusion fluctuation is. Gas accumulation also forms at the dead corners of the utility tunnel mezzanine. The addition of fire-proof air outlets above the fire door and inducing fans in the mezzanine of the utility tunnel can effectively reduce the gas accumulation near the fire door and in the interlayer. Related Articles | Metrics

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Experimental study on fire extinguishing of pneumatic conveying cement powder device in wood crib fire YAN Long, WANG Ning, XU Zhi-sheng 2022, 41 (3):  385-388.  Abstract ( 1538 )   In order to study the feasibility of extinguishing wood crib fire by cement powder, the fire extinguishing experiment of wood crib fire was carried out through a self-designed pneumatic conveying device of cement powder. The temperature acquisition device and camera were used to test the change law of wood crib fire before and after extinguishing by cement powder. The results show that the pneumatic conveying cement powder fire-extinguishing device can suppress the fire effectively on the surface of wood stack and reduce the combustion temperature of wood stack fire significantly. Cement powder is used to extinguish fire by covering effect, and excessive wood stack height and porosity weaken the extinguishing effect of cement powder. The fire extinguishing effect of cement powder varies significantly with the spray angle and spray height of cement powder. When the spray angle is 90° and the spray height is 1.5 m, the fire extinguishing effect is the best. Related Articles | Metrics

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Research on training system of firefighters' CPR skills TAO Peng-yu，SONG Wen-qi，NIU Kun，MI Li-pei 2022, 41 (3):  389-393.  Abstract ( 1579 )   This paper expounds the importance of firefighters mastering CPR technology at the scene of disaster and accident rescue, analyzes the current situation and existing problems of CPR skill training for firefighters, briefly introduces the advantages of applying hybrid reality technology to CPR training for firefighters, and designs a kind of CPR skill training system for firefighters. This study is of great significance to enhance firefighters' mastery of cardiopulmonary resuscitation skills, improve firefighters' emergency treatment ability, and improve the survival rate of the wounded at the scene of disaster accidents. Related Articles | Metrics

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Application of optimized neural network in multi-sensor fire detection ZHONG Rui1,2, LU Shou-xiang1 2022, 41 (3):  394-397.  Abstract ( 1579 )   On the problems of BP neural network in the process of fitting, such as low detection precision, easy to fall into local optimum, an optimized BP neural network model based on genetic algorithm(GA) and simulated annealing algorithm(SA) was developed. The model can significantly improve the recognition accuracy, while avoid the network over fitting phenomenon, and make the forecast results jump out of local optimal so as to achieve the global optimal. Firstly, the hidden layer structure was improved by GA, and then the connection weight was improved by SA. Finally, the optimized GA-SA-BP model was used for information fusion of fire experimental data to realize fire detection. Experimental results show that compared with the single BP neural network, the BP neural network improved by GA and SA can effectively improve the fitting ability of the network, and improve the accuracy of fire detection to 98.91%. Related Articles | Metrics

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Three light integrated accurate wildfire ZHOU Kai, ZHANG Rui-zhe, REN Zhi-gang, 2022, 41 (3):  398-401.  Abstract ( 1532 )   This paper described the hardware composition of the wildfire detect instrument, explained the automatic identification algorithm and high accuracy positioning function by flame and smoke. A real wildfire caused by actual circle malfunction disorder and historical wildfire smoke images verified the performance of this instrument. Experimental data indicated that, the instrument insects the automatic identification function and high accuracy positioning function into normal infrared camera,can effectively identify the fire at initial phase, and has practical significance for the wildfire prevention of power line. Related Articles | Metrics

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Research on the application of large flow liquid nitrogen foam fire extinguishing system at chemical parks LANG Xu-qing, MU Xiao-dong, SHANG ZU-zheng, WU Jing-feng 2022, 41 (3):  402-405.  Abstract ( 1575 )   The mechanism of liquid nitrogen foam fire extinguishing system was introduced and foam expansion, drainage time, micro image of liquid nitrogen foam were studied. Long distance pipe system was established to study the transportation of liquid nitrogen foam. Multi-scale tank fire tests were conducted to test the fire extinguishment of the foam. The results showed that the even diameter of liquid nitrogen foam bubbles was 20 ~ 50 μm and the foam bubbles were even. Foam expansion was about 7 to 8 and the 25% drainage time was about 3 to 5 minutes. The liquid nitrogen foam can be transported to 1 000 meters without foam layer drainage, and the performance of the foam remains the same. The fire extinguishment capability of liquid nitrogen foam was about 1.6 times of that of compressed air foam and 2.5 times of that of aspirating foam. The large flow liquid nitrogen foam system can be widely applied for large tank fires, floor pool fires, flowing fires and some large equipment fires. Related Articles | Metrics

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Realization of a movable automatic gas compensation device WANG Zhao-yang，LIN Yun-xin 2022, 41 (3):  406-408.  Abstract ( 1545 )   The movable gas volume automatic compensation device is a new type of fire rescue equipment focusing on flood disaster rescue. Its working principle is to adopt the gas volume automatic compensation method, so that the gas filling device in the rescue process can always maintain a relatively stable rated working pressure, ensure the best efficiency of the device, and effectively make up for the air leakage accident caused by sharp objects. It can improve the effectiveness of combat training and reduce the potential safety hazards of combat training. Related Articles | Metrics

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Countermeasures assessment of the explosion and combustion of electric vehicles in elevators and design of blocking system GUO Yan, HE Tong-jian, LUO Dan, ZHANG Bin 2022, 41 (3):  409-412.  Abstract ( 1580 )   According to TRIZ theory and analytic hierarchy process(AHP), the cause of explosion and combustion of the electric vehicle in the elevator was analyzed, and various safety countermeasures were put forward, and then a new evaluation model for the quality score assessment of each solution was established. A new car blocking system was proposed and introduced. It was found that the quality evaluation of the proposed safety countermeasures can be completed by using the evaluation model. The new type of intelligent car blocking system proposed can provide a reliable basis for elevator safety decision-making. Related Articles | Metrics

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Study on the combustion stability of gas generant based on flame area analysis ZHANG Cheng-chen， ZHU Chen-guang， YAN Chen-guang， DUANMU Fan-shun 2022, 41 (3):  413-416.  Abstract ( 1493 )   Intermittent explosion spray is a common problem when using dry powder fire extinguishing device. This problem is related to the formulation, uniformity and structure of the gas generating agent while the combustion stability is a direct manifestation of the combustion effect of the gas generating agent. In this paper, a kind of gas generating agent was prepared by mechanical mixing and freeze-drying, and the combustion stability of the gas generating agent is analyzed by high-speed camera. The scanning electron microscopy (SEM) was used to characterize the morphology of gas generating agent. The SEM images showed that the freeze-drying method was significantly better than mechanical mixing in the uniformity of samples. The combustion flame area is quantified by Matlab, and the results indicate that when comparing the ratio of the stable combustion time to the total combustion time, the average value of the mechanical mixing agent is only 13% while the freeze-drying agent reaches to 35.19%; when comparing the standard deviation of average flame area in the stable combustion stage, the mechanical mixing agent is 9.263 while the freeze-drying agent is 5.924. Related Articles | Metrics

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The effects of ceramic fillers on properties of silicone rubber composites JIANG Hui-jing1, WANG Jun-sheng2,ZHU Hai-bo1, YANG Jin-jun1 2022, 41 (3):  417-420.  Abstract ( 1623 )   Ceramicizable silicone rubber composites are prepared with glass powder and mica powder as ceramic fillers. The effects of 80 parts of ceramic fillers and the ratio of glass powder and mica powder on the mechanical properties, flame retardancy, thermal stability and ceramic properties of silicone rubber were. The results show that the ceramic filler has a great influence on the mechanical properties of silicone rubber composites. The maximum tensile strength of composites is 5.96 MPa and the elongation at break is 421.3% with the loading of 30 phr glass powder and 50 phr mica powder. The flame retardancy of composites are improved with the addition of ceramic fillers. The maximum LOI value of composites is 28.4 while 20 phr glass powder and 60 phr mica powder are added. The addition of ceramic fillers significantly reduced the initial and maximum thermal decomposition temperatures of the composites while increased the residues at high temperature. The ceramic properties of the composites are significantly improved at high temperature. The ratio of glass powder to mica powder has a few effects on the mechanical properties, flame retardancy and thermal stability of the composites. As the increase of the loading of glass powder, the structure of the ceramics are more compact, the three-point bending strength of ceramics also increase and the maximum value is 15.53 MPa. Related Articles | Metrics

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Application status and development trend of forest fire extinguishing technology in China YU Wei， LU Qiang 2022, 41 (3):  421-424.  Abstract ( 1956 )   In order to further improve the level of forest fire disposal technology in China, the application status of forest fire extinguishing technologies are summarized based on field survey, attending forum and literature analysis. This paper analyzes the main types, development history and practical application effects of forest fire extinguishing agents, introduces the current situation and main problems of fire extinguishing bomb, individual fire extinguishing equipment and forest fire truck, and points out the important role of aviation fire extinguishing in forest fire fighting. Furtherly comparing with the overall situation of foreign forest fire extinguishing technology, this paper points out the shortcomings of the current forest fire extinguishing technology in China in standard formulation, new product scientific research and application. Some suggestions are then given on the follow-up development direction of strengthening scientific research investment and paying attention to environmental protection performance, which provides a scientific reference for the prevention and control of forest fire. Related Articles | Metrics

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Thoughts on the development of emergency management and rescue from the typical building static collapse accidents YIN Liang, LI Jin, JIANG Nan 2022, 41 (3):  425-427.  Abstract ( 1560 )   Information was collected and analyzed on the "collapse of a high-rise apartment in Miami-Dade County, Florida, USA" as a representative of static collapse accidents. The existing buildings in China have entered the "middle-aged" period. It is suggested that the policy framework, technology innovation, equipment R&D and configuration should systematically improve the whole-life safety of the buildings in service, in order to prevent and solve the risk of building collapse and improve the ability to deal with collapse accidents. Related Articles | Metrics

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Investigation and revelation of an electrostatic lightning accident in a petrochemical enterprise SHEN Li-xin1，GUAN Jie2，WANG Liang2 2022, 41 (3):  428-430.  Abstract ( 1614 )   This paper briefly introduces the investigation situation of flash explosion accident in the ethylene plant of Lanzhou Petrochemical Company, and comprehensively analyzes the main points and judgment basis of electrostatic accident identification through on-site investigation, investigation visit, collection monitoring, technical analysis and other methods, so as to provide reference for the investigation and determination of electrostatic flash accident in similar places. Related Articles | Metrics

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Video analysis and field experiment in a fire accident investigation JIA Jun 2022, 41 (3):  431-434.  Abstract ( 1797 )   In a typical electrical fire accident investigation process, the investigators used the "Fire Inspection" video analysis software to analyze the key information in the video, determined the investigation direction of the electrical fire based on the arc characteristics, and used the fire video quantitative data method to calculate the fire video. The projection angle of the arc light, using the reverse extension line of the light projection to delimit the arc generation range. Through the experiment of light and shadow contour lines at different locations on the scene, the scope of investigation was narrowed as much as possible, and the conclusions of fire video analysis were verified by combining trace material evidence and witness testimony, so as to accurately determine the time, cause and location of the fire. Finally, the fire video analysis method, field experiment application, investigation and evidence collection measures are summarized and summarized. Related Articles | Metrics