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15 May 2020, Volume 39 Issue 5 Previous Issue    Next Issue

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Reliability analysis of shear capacity of reinforced concrete composite beams after high temperature CAI Bin, HAO Li-yan, XU Long-fei 2020, 39 (5):  579-585.  Abstract ( 1809 )   A reliability analysis method of the shear capacity of the oblique section and the combined interface of the reinforced concrete composite beams after high temperature is provided. Firstly, the thermal parameters of reinforced concrete (RC) beams were selected, and the heat conduction analysis was performed using ABAQUS. Based on the thermal analysis results and the calculation method of the shear capacity of RC composite beams after high temperature, the residual bearing capacity of the oblique section and the combined interface after fire was obtained. Finally, based on MATLAB, Monte Carlo method was used to analyze the reliability. The results show that the heating duration has a significant effect on the reliability. The reliability index increases with the increase of the concrete strength and the stirrup reinforcement ratio. It increases first and then changes little with the increase of the load ratio. The reliability of the oblique section bearing capacity of RC composite beams is greater than that of the combined interface at room temperature, but with the increase of heating time, the shear strength of combined interface is better than that of the oblique section. This method can be applied to the reliability analysis of the bearing capacity of RC composite beams after high temperature, and has high precision and accuracy. Related Articles | Metrics

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Acoustic emission signal characteristics of heat-treated concrete under uniaxial loading WANG Xue-ni, LI Zhong-hui, NIU Yue, KONG Yan-hui 2020, 39 (5):  585-590.  Abstract ( 1719 )   To study the change of mechanical properties of concrete and the precursory characteristics of structural instability after fire, the uniaxial compression experiments were carried out on concrete specimens after heat treated at 20, 100, 200, 300, 400 ℃ to monitor the acoustic and electrical response characteristics of the specimen under load failure, so as to identify the precursory features of structural instability. The results showed that the appearance color, internal structure and mechanical properties of concrete changes after heated. With the higher temperature, the more obvious color change and the more abundant crack development and the lower maximum stress, the higher maximum strain. AE signal and AP signal become more active with the increase of temperature and the response of the two signals is closely related to the crack growth, these two signals can reflect damage evolution process of the internal structure of the specimen. The AE signals and AP signals were statistically analyzed by variability coefficients. The results showed that the variability coefficient of AE signal is relatively stable during the loading process of the sample, and it has a rapid increase to peak as abnormal response before the sample is unstable, which can be used as a precursor to judge the structural stability of the sample. Compared with the AE signal, the variability characteristic of the AP signal is at a higher value at the initial stage of the sample loading, then decreases, and rapidly increases to a peak before the sample is destabilized. Related Articles | Metrics

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Ignition and spread characteristics of surface combustibles in Pinus armandi forest LONG Teng-teng, XIANG Lin-chuan, YAN Xiang-xiang, GAO Lei, WANG Qiu-hua, YE Biao, CHEN Qi-liang 2020, 39 (5):  590-592.  Abstract ( 1781 )   Sample plots were set in the continuous distribution area of Pinus armandi in Shiguan and Yuanbaoshan of Yunnan forest natural center. Ground fuel samples were selected from 6 quadrats of 2 m×2 m along the diagonal. The experiments were carried out in a 200 cm×120 cm×32 cm iron combustion bed with a slope of 10°. The ignition and spread characteristics of the combustibles were characterized by measuring the ignition time, continuous combustion time, flameless combustion time, thermal radiation characteristics and burn out rate of the combustibles. The results showed that the ignition time of surface combustibles was 1~3 s. It was easy to ignite. Shiguan's uphill fire continues for a relatively short time. It was about 150 s. The flameless burning of Yuanbaoshan downhill fire lasted for a long time with the maximum of 345 s.The fire rate on Yuanbao Mountain was higher than that on Shiguan. The highest rate of fire damage on the uphill fire was 88.29%, and the highest rate of fire damage on the downhill fire was 76.13%. Related Articles | Metrics

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Determination and precautionary measure of spontaneous ignition temperature of dust REN Chang-xing, MENG Shuang, ZHANG Yan, ZHANG Xin 2020, 39 (5):  593-596.  Abstract ( 1803 )   The related determination methods and standards of spontaneous ignition temperature were introduced, and the scope and hazardous classification were analyzed contrastively. Based on the thermal explosion theory on spontaneous ignition temperature, a device for measuring the spontaneous combustion temperature of different volume of dust by constant temperature oven was developed. Moreover, the experimental procedure, test condition and spontaneous ignition criterion were shown. Taking some lignite as example, the spontaneous ignition temperature characteristics of dust accumulations with different volumes were analyzed, and it was shown that there is an increase in induction time to oven temperature and temperature rise rate with the increase of volume. The precautionary measures were put forward, including dust temperature control, volatile matter detection, storage space and deep fire extinguishment. Related Articles | Metrics

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Effect of concentration on flame propagation of corn starch in vertical half-open pipe YANG Kai, CHEN Yan-bin, PANG Lei, ZHANG Zhi-wen, REN Jia-qi, LI Si-gang, LIU Wen-shuai 2020, 39 (5):  596-600.  Abstract ( 1743 )   Taking food grade corn starch after vacuum drying as example, particle shape and size were analyzed by laser particle size analyzer and SEM. High speed camera technology was used to study explosive flame propagation behavior of corn starch dust cloud in a 1.2 m long vertical half-open tube, and the influence of dust cloud concentration on flame propagation with or without obstacle was investigated. The results showed that the flame speed overall increases at first and then decreases. Both dust cloud concentration and obstacle have significant influence on the flame propagation pattern and flame speed of corn starch dust cloud. With the increase of dust cloud concentration, the dust combustion is not sufficient, resulting in the gradual decrease of the maximum flame speed and flame brightness and unclear flame contour and flame segment phenomenon. The turbulence effect of obstacles will accelerate the combustion of dust, increase the speed of dust flame propagation, improve the flame brightness and contour clarity. However, an increase in the concentration of dust clouds will reduce the accelerated effect of obstacles on flame propagation, and promote the maximum flame speed to increase at first and then decrease. Related Articles | Metrics

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Experimental study on the inhibitory effect of inert medium on aluminum powder GUAN Wen-ling, YANG Tian-can, DONG Cheng-jie, ZHAO Jian-zhang 2020, 39 (5):  601-603.  Abstract ( 1793 )   he inert effect and of three inert media (calcium carbonate, sodium bicarbonate and ammonium dihydrogen phosphate) and the synergistic inhibition effect between them were analyzed by 20 L-Siwek explosion test system. The results show the explosion character of aluminum powder whose concentration is 300 g/m3 is obviously inhibited after adding different inert substances, and the explosive intensity decreases with the addition of inert inhibitor; NH4H2PO4 is the best of the three inert media, followed by CaCO3. Co-inhibitory experiments indicate that the inhibition effect of composite medium is better than that of single medium. The compound inhibitor has the best anti-explosion performance when the ratio of CaCO3  and NH4H2PO4 is 1∶1. Related Articles | Metrics

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Study on temperature field distribution of linear fire source in different lateral positions in pipe gallery XU Gang, ZHU Guo-qing , CHU Tian-wei, 2020, 39 (5):  604-607.  Abstract ( 1745 )   In order to study the temperature distribution of the linear fire source in the pipe gallery at different lateral positions, this paper sets the linear fire source at the lateral positions of 0, 20, 40 and 60 cm from the center of the pipe gallery. The study found that the longitudinal temperature of each working condition increased first, then decreased and then increased with time. The highest temperature rise first decreases and then rises during the increase in the lateral distance of the linear fire source from the center, and the time to reach the highest temperature also increases first and then decreases. The arc-shaped tube wall has an influence on the fire source combustion. The angle in the vertical direction of each working condition at the cross section of 0 m from the center of the pipe gallery reached the highest temperature rise. In the cross section of 0.5 m transverse section, the angle corresponding to the highest temperature rise of each working condition is 15°. When the lateral distance between the fire source and the center of the pipe gallery increases, the temperature rise gap between −45° and 45° increases.  Related Articles | Metrics

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Study on the temperature profile of horizontally oriented jet fire impinging on the vertical plate DONG Bing-yan, WU Jin-xiang, HUANG You-bo 2020, 39 (5):  607-610.  Abstract ( 1759 )    In order to study the temperature profile of horizontally oriented jet fire impinging on the vertical plate, numerical simulation software was used to simulate the rectangular leakage port methane jet fire with different aspect ratios. The temperature distribution features on horizontal and vertical direction over obstruction surface were analyzed. Results show that the leakage velocity and aspect rate of orifice have a significant effect on the temperature distribution over obstruction surface. The larger the leakage velocity, the wider the temperature rise area, but the width of temperature rise area decreases as the aspect rate of orifice increasing. The temperature rise area increases at vertical and transverse direction with the increasing velocity.Meanwhile, the larger aspect rate of orifice results in the thicker temperature rise area and varies width of temperature rise area. Related Articles | Metrics

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Effect of fire barrier on the spread of cable fire in utility tunnel LI Zheng, ZHANG Guo-wei, JIA Bo-yan, ZHU Guo-qing, ZHANG Peng 2020, 39 (5):  611-614.  Abstract ( 1761 )   FDS full-scale fire numerical simulation model was established based on the standard section of the utility tunnel of Chengbei road in Suzhou. The fire development situation and temperature distribution law of the power cable compartment fire in the utility tunnel were simulated and analyzed. Four layers of cables were set on the left and right sides of the pipe gallery, the influence of the fire barrier on the fire development and temperature distribution was studied by 2 scenarios of with or without fire barrier. The results showed that when there is no fire barrier, the development direction of the fire in the utility tunnel is mainly transverse spread, and the top cable burns with the expansion of the fire and the heat transfer of smoke accumulation,and finally spreads to other areas of the utility tunnel. The vertical fire spread time was delayed by about 40%,and the maximum temperature in the utility tunnel was reduced by about 18% by setting the fire barrier. Related Articles | Metrics

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Experimental studies on upward flame spread under limited distance effects GU Si-nian, BU Xue-min, ZHU Guo-qing 2020, 39 (5):  614-618.  Abstract ( 1751 )   Using 45 cm tall, 5.0 cm wide and 2.0 mm thick advertising canvas，the effects of limited distance with the range of 3.0~9.0 cm between wall and fuel surface on flame length, spread rate and ignition time are quantitatively analyzed. The major conclusions are summarized as follows: When the limited distance is 3.0~8.0 cm，the flame length on limited side is larger than that on unlimited side, whereas when limited distance is beyond 8.0 cm, the flame lengths on both sides are basically the same. Both the flame length and spread rate first increase and then decrease with limited distance, and finally reach a constant value, while the ignition time decreases first and then rises with limited distance, and ultimately achieves a stable value. The relationship between the heat flux received by virgin surface and ignition time is established. Moreover, the variation trend of the heat flux received by virgin surface with the limited distance is analyzed, which can be used to explain the cause of the non-monotonic trend in spread rate. Related Articles | Metrics

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Effect of wind speed on smoke diffusion of concave exterior wall fire in high-rise buildings YIN Yue, ZHOU Ru, HE Jia-peng, LI Si-cheng, MING Zhuang 2020, 39 (5):  618-623.  Abstract ( 1818 )   To study the influence of ambient wind on smoke diffusion at the bottom of concave exterior walls of high-rise residential buildings, the characteristics of smoke such as temperature, speed and concentration in concave walls of high-rise residential buildings were simulated numerically. Take the ratio of the length of the side wall and the distance between the side walls of the groove of the outer wall as the structural factor, different working conditions were set for comparative analysis. It is found that the temperature at different heights of the same structural factor is exponentially distributed under different wind speeds.The relationship model between critical wind speed of flue gas leaving the central wall of the building and the size of the structural factor was obtained to guide the dimension design of concave exterior wall of high-rise residential buildings. The rupture time of the bottom window is relatively the maximum when the structural factor is 1. Related Articles | Metrics

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Influence of cross section size on limit height of chimney effect LI Yu, FU Yu 2020, 39 (5):  624-627.  Abstract ( 1862 )   In order to study the effect of the change in the cross-section size of the shaft on the ultimate height of the tunnel chimney effect when a tunnel fire occurs, FDS was used to carry out numerical simulations of tunnel fires in 6 different cross-section sizes when the cross-section shape of the shaft is square.The change of flue gas velocity with time in different positions was analyzed. It is found that there is a limit height for the shaft chimney effect, and it increases with the shaft section size.According to the simulation data, a function expression was obtained and verified by simulation. It can be used to estimate the limit height of the shaft chimney effect when the shaft side length is not less than 0.4 m, but not greater than 3.0 m. Related Articles | Metrics

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Influence of patio width and depth on smoke movement of fire CHEN Long-fei, YUAN Man, CHEN Yan-qiu 2020, 39 (5):  628-632.  Abstract ( 1916 )   FDS fire numerical simulation method was used to analyze the influence of different width and depth of the patio on the pressure difference between the bottom and top of the patio, the temperature inside the patio and CO concentration in the corridor, to study the influence of the width and depth of the patio on the stack effect in high-rise residential buildings. Considering 3 kinds of fire source power, 4 kinds of open patio width and 4 kinds of open patio depth, 48 working conditions were set to carry out the analysis. It was found that the stack effect is weak due to the side connectivity in the open patio, and the width and depth of the patio have no obvious effect on the stack effect. The greater the width of the patio and the deeper the patio, the lower the temperature inside the patio and the CO concentration in the corridor. Related Articles | Metrics

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Performance-based fire protection design of a large public transportation hub LIU Qing-en 2020, 39 (5):  633-636.  Abstract ( 1752 )   The large-scale bus hubs installed in the building and underground have problems such as the fire protection area exceeding the requirements of the code due to the use of functions. This paper uses the principles and methods of fire safety engineering to perform a fire performance design for a large-scale bus hub. By setting the fire scenes, the smoke movement simulation and the evacuation safety analysis were carried to verify the feasibility of the enhanced measures, which could give references for the fire protection design of similar projects. Related Articles | Metrics

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Simulation analysis of smoke diffusion characteristics in the process of fire train braking YU Li, SUN Yuan, WANG Ming-nian, DAI Zhong-yu, LIU Yong-gang, TIAN Yuan 2020, 39 (5):  637-641.  Abstract ( 1698 )    In order to explore the smoke diffusion characteristics of fire train when braking to the underground station for rescue, theoretical analysis and numerical simulation were used to study the smoke diffusion law in the rail area and platform layer of the station when the fire train slowed down to stop under different smoke control measures, and the influence of the fire prevention and ventilation system of the station under this scenario was defined. The results show that the smoke distribution in the upper and lower reaches of the fire train is affected by the characteristics of moving fire source and piston wind. Although the shielding door can effectively prevent the smoke from spreading to the platform, it will increase the piston wind speed in the rail area and increase the smoke spreading speed, which is not conducive to the safe evacuation of passengers. The smoke discharge effect in rail area was limited by the influence of piston wind, and the total smoke discharge efficiency decreased by 14%,and the smoke exhaust valves in the lower reaches of fire are more efficient. Related Articles | Metrics

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A study of fire extinguishing performance of compressed air foam on rim seal fire for floating roof tanks YANG Zhen-ming, CHEN Tao, HU Cheng, BAO Zhi-ming 2020, 39 (5):  641-645.  Abstract ( 1719 )    In order to evaluate the technical feasibility of compressed air foam system for the rim seal fire of floating roof tanks, a series of full-scale fire extinguishing tests under different foam solution foam application rates and gas-liquid ratios were conducted to investigate the fire extinguishing performance of compressed air foam, and the suitable fire extinguishing application parameters were put forward.The results indicate that the rim seal fire for floating roof tanks was extinguished quickly and effectively by the rim seal discharge device of compressed air foam under the condition of the foam solution foam application rate being 3.4~8.0 L/(min·m2), and there was no re-ignition; the higher the foam solution foam application rateis, the faster the control and extinguishing speed is; the air/foam solution volume ratio has a slight effect on the fire control and extinguishing speed in the range of 8∶1 ~ 12∶1. It is suggested that the foam solution foam application rate is not less than 5 L/ (min·m2), the air/foam solution volume ratio is not less than 8∶1, and the apply duration of compressed air foam is no less than 15min in practical engineering. Related Articles | Metrics

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Comparison of the fire extinguishing performance of different types of compressed gas foam on class B fires CHEN Tao, HU Cheng, BAO Zhi-ming, FU Xue-cheng, WANG Rong-ji, XIA Jian-jun 2020, 39 (5):  645-648.  Abstract ( 1780 )   The fire extinguishing performance of compressed gas foam based on different types of gas on 120# solvent oil fires was compared by pool fire tests using a laboratory compressed gas foam system. The types of gas source and gas supply equipment suitable for ordinary class B fire were investigated. The results indicate that both compressed nitrogen foam and compressed air foam can extinguish 120# solvent oil standard fuel fires and have good anti-burning and anti-reburning performances under the condition of the foam solution foam application rate was 2.5 L/(min·m2). Compared with compressed air foam, compressed nitrogen foam has a slightly improved fire-fighting performance. However, the difference between them was not significant.For ordinary class B fire, it is recommended to directly use the existing nitrogen supply equipment as the gas supply source for places with nitrogen source in the actual project. Related Articles | Metrics

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Fire extinguishing effect of heptafluoropropane on lithium iron phosphate energy storage battery ZHANG Ming-jie, YANG Kai, ZHANG Jian, LIU Hao, GAO Fei, GENG Meng-meng 2020, 39 (5):  649-652.  Abstract ( 2481 )   Take Lithium iron phosphate energy storage battery as the experimental object, the fire extinguishing effect of heptafluoropropane on lithium iron phosphate battery was studied under the space condition of free expansion and limited expansion by splint. The change of temperature and voltage in the fire-extinguishing process of heptafluoropropane on lithium iron phosphate energy storage battery fire were studied and the fire-extinguishing effect of it was analyzed. The results showed that for free-expanding battery fires, heptafluoropropane can stop its thermal runaway reactioneffectively. For the battery with limited expansion, the thermal runaway process of the battery itself is more intense, and the temperature keeps rising for a longer time after extinguishing the fire. The second thermal runaway or even reburns of the battery happens. In practical application, safety and cost should be taken into consideration comprehensively to set up appropriate expansion space for the battery, and the fire-extinguishing agent of heptafluoropropane should be released as soon as possible. Related Articles | Metrics

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Research on active sprinkler system ZHANG Qiang, WANG Hao-xuan, ZHANG Lei, WANG Hai-juan, ZHAO Hong-zhe 2020, 39 (5):  652-654.  Abstract ( 1787 )   In view of the shortcomings of traditional automatic sprinkler system, such as long response time and large water loss, this paper proposes a research scheme of active automatic sprinkler system, which realizes the initiative and intelligence of automatic sprinkler system by new detection components, electric heating sprinkler, and algorithm programming. An experimental platform was built. Against corner fire, border fire and center fire, the system fire detection performance and sprinkler startup condition are analyzed. The experimental results show that the automatic sprinkler system can detect the location of the fire in the early stage, start the sprinkler head and its group in the corresponding position by active electric heating, put out the initial fire and reduce the water loss at the same time. Related Articles | Metrics

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Research on CAFS pipe network transmission characteristics of a converter transformer WANG Guan-jian, SHI Xiang-jian, HAN Jiao, WEN Pei, ZHAO Sen-lin, XIONG Mu-wen, ZHANG Jia-qing, GAO Xu-hui, WANG Yue-yong 2020, 39 (5):  655-658.  Abstract ( 1711 )    In order to thoroughly understand the characteristics of multiphase fluid transportation in the compressed air foam fire extinguishing system (CAFS) pipe network, simulation of the entire pipeline transportation process of a compressed air foam fire extinguishing system used for converter transformer protection was performed using Fluent software. On the basis of verifying the accuracy of numerical simulation, the apparent viscosity and pressure changes of fluids in typical areas such as straight pipe sections, elbows, and tees in the pipe network were analyzed. It is found through research that the compressed air foam fluid flowing in the pipe network will change due to its own parameters during the flow process. Therefore, the pressure drop of the pipe network and other results show complex characteristics that are affected by multiple factors such as expansion rate of foam and flow rate. Related Articles | Metrics

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Building 3D emergency decision making system based on UAV technology for fire rescue assistance YAN Su, ZHANG Guo-wei., ZHU Guo-qing., PAN Rong-liang 2020, 39 (5):  659-662.  Abstract ( 1803 )   To achieve the highly efficient, scientific, precise firefighting and rescue, this paper proposes to use the drone to quickly construct the geographic information and three-dimensional model of the fire area, and to monitor the fire deterioration factors in real time to detect the spatial and temporal distribution of disaster factors during the fire development such as airflow, temperature field and toxic and harmful gases. Using the low-latency 5G network and fire development theory, the firefighting decision cloud center is established, and the real-time data collected by the drone is mathematical modeled and calculated based on cloud fire data center, to predict the fire possible evolution path and disaster development processes, to form dynamically adjustable fire rescue decision-making plan based on real-time disaster information. Finally, the 5G communication is used again to transmit the disaster information data perceived by the drone and dynamic rescue decision-making plan to firefighters in real time. The method can improve the firefighting and rescue efficiency, and avoid loss caused by disasters turning violent.  Related Articles | Metrics

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Research on the multi-rotor UAV multi-task assignment based on discrete particle swarm optimization algorithm WU Li-zhi, CUI Yan-chen, ZHU Hong-wei, CUI Jun-guang 2020, 39 (5):  662-665.  Abstract ( 1760 )   Discrete particle swarm algorithm was used to solve the problem of multi-task assignment of UAV for the team of fire and rescue. Through analyzing the conditions of on site task assignment, the problems such as drone endurance, detection width, detection gas type, task timing and task sequence constraints, and so on were considered in the evaluation index design, and the reverse operator is introduced to optimize the algorithm of discrete particle swarm. The simulation results demonstrate that the optimized PSO has better performance and convergence than the genetic algorithm. The research above can provide some algorithm support for mission assignment of UAVs in fire and rescue site. Related Articles | Metrics

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Design and research on intelligent fire detection and monitoring four rotor aircraft LIU Yong-tao, JIANG Di, LIU Jia, LI Guan 2020, 39 (5):  666-670.  Abstract ( 1709 )   The flight control principle of four-axis vehicle was studied and the quaternion kinematics differential equation was established. Through the first-order RungeKutta method, the equation was solved. The real-time quaternion reversal Euler angle was used to represent the flight attitude information, so the attitude process could be controlled easily.The real-time attitude data was collected by the inertial sensor MPU9250, and the actual flight attitude was obtained by Mahony complementary filtering algorithm fusion.The flight control of micro four-axis vehicle was realized by cascade PID control algorithm. Finally, the simulation parameters of the cascade PID were adjusted by MATLAB software, and the actual debugging on the inner diagonal velocity loop and outer Euler angle loop of the main control aircraft was carried out on STM32F411. By equipped with intelligent flame recognition camera, the aircraft can automatically lock the key fire areas during area search and monitoring, and improve the detection efficiency. Related Articles | Metrics

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An optimal calculation method for telescopic pipe of fire fighting vehicle BAI Bing, XU Lei, ZHANG Jun 2020, 39 (5):  670-675.  Abstract ( 1758 )   In this paper,the calculation of the pressure loss of the telescopic pipe used in the firefighting vehicle was analyzed and studied, and a calculation flow of pipeline optimization was proposed. By using this method, the pressure loss characteristics of stainless steel pipeline and aluminum alloy pipeline were analyzed respectively. Through this calculation, the goal of pipeline weight reduction and pressure loss reduction was realized. Finally, the impact of the boom deformation on the optimization results was analyzed in detail to ensure the safety demand during the usage of high-rise aerial platform fire fighting vehicle. Related Articles | Metrics

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Research and application on fire source tracking and active disturbance rejection algorithm for fire-fighting robot GUO Ting-ting, BAO Ming-song, CHI Rong-hu, LI Juan 2020, 39 (5):  675-678.  Abstract ( 1799 )   For realizing the rapid tracking of fire source through the fire-fighting robot by using a thermal imager, a dynamic model of the two-dimensional(2D) pan-tilt head in the horizontal slewing and vertical pitch directions was carried out in this paper. The tracking control simulation experiment was carried out by using the Active Disturbance Rejection Control (ADRC). In addition, the parameters of the ADRC were tuned in the simulation experiments. Based on the simulation experiments, a physical comparison verification between the traditional PID and ADRC algorithms were performed on the auto-tracking system for 2D pan-tilt. The experimental results showed that the developed auto-tracking based on ADRC algorithm has advantages such as small overshoot, short adjustment time and strong anti-disturbance performance. Moreover, the proposed method provides a basis research for fire-fighting robot to extinguishing the fire automatically. Related Articles | Metrics

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Degradation and treatment of protein foam extinguishing agents XU Ping, CHEN Ru-dan, WANG Zi-chen 2020, 39 (5):  679-681.  Abstract ( 1805 )   In view of the effect of widely used protein foam extinguishing agent on the natural environment after scrapping, the main components and contents of their pollutants of different protein foam extinguishing agents were analyzed, and their biodegradability was discussed.Considering the fluorine foam extinguishing agent which is hard to degrade, corresponding technical countermeasures and methods were put forward. The research status of new environmental friendly fluorocarbon surfactants was analyzed and the research prospect was put forward. Related Articles | Metrics

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Design and properties of polypyrrole modified carbon nanotubes LI Zhen-hua, WANG Shi-jun 2020, 39 (5):  681-684.  Abstract ( 1735 )   Through the two-step modification of carbon nanotubes (CNT), the P, N-rich organic-inorganic hybrid structure (HPCNT) was obtained by grafting polypyrrole onto the P, N-rich phosphoronitrile unit, which was added into PP matrix as filler. Compared with pure CNT, the inclusion layer on the surface of hybrid structure has stronger interface force and interface compatibility with the matrix, so it presents a good dispersion state, and then it can effectively form a physical barrier network. At the same time, its rich P, N elements will provide a certain degree of flame retardant, and can promote the formation of carbon. When 3% HPCNT was added, PHRR and THR changed to 987 kW/m2 and 111 MJ/m2 respectively, which decreased by 31.6% and 15.3% respectively. PCOY and PCO2Y decreased by 20.8% and 31.7%, respectively, to 0.57 mg/m3 and 11.44%. Related Articles | Metrics

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Study on flame retardant epoxy resin with phytic acid-melamine salt SONG Kai-li, NING Kai, ZHANG Cong-yun 2020, 39 (5):  685-688.  Abstract ( 1953 )   The bio-based flame retardants phytic acid-melamine salt (MPA) was used to improve the flame retardant properties of modified epoxy resin (EP) and its performance was studied. Infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the chemical structure of MPA. Thermogravimetric analyzer (TGA), limiting oxygen index tester (LOI), vertical combustion tester (UL-94) and cone calorimeter (CC) were used to study the thermal stability and flame retardancy for EP. TGA results showed that the residue char for MPA is 25.6% at 800 ℃, which enhanced thermal stability of EP in high temperature zone. EP with 15% MPA can pass UL-94 V-0 rating, indicating that MPA shows good flame retardant effect for EP. Cone calorimetry results revealed that the introduction of MPA reduced the heat release rate and total heat release of EPsignificantly, and it exhibited excellent smoke suppression performance. Related Articles | Metrics

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Discussion on reconstruction of fighting force system of fire rescue team WANG Yong-ming 2020, 39 (5):  689-691.  Abstract ( 2050 )   This paper analyzes the elements and current situation of the combat effectiveness of the fire rescue team in China, puts forward the goal and path of the reconstruction of the combat strength system of the fire rescue team, and gradually forms a new joint combat force system with the elite professional force as the main body based on the two realistic struggles of natural disaster and accident disaster. Related Articles | Metrics

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Analysis of internal temperature distribution characteristics in combustion training room SUN Nan-nan, LIU Jian-min, XU Hui, LIANG Qiang 2020, 39 (5):  692-696.  Abstract ( 1706 )   Six combustion experiments of different fire source sizes, opening and closing conditions were carried out in the container combustion training room. The internal temperature distributions were studied to give reference for firefighters to make training plan and to carry out actual combat training. The experimental results showed that the phenomenon of transient combustion occurred under closed-door combustion condition. When the door was opened, the heating rate of ignition source increased and the highest temperature appeared at the ceiling. When the door was closed, the maximum temperatures of small, medium and large fires were 331, 463 and 752 ℃, respectively. With the increase of horizontal distance from the fire source, the temperature decreased rapidly at first and then raised slightly. The temperature at the 1.2 m height ranged from 100 ℃ to 180 ℃. In the comparison experiments of medium large fires under closing door and opening door conditions, it was found that high temperature duration increased, and the temperature at monitoring sites except fire source decreased significantly with the increase of the area of opening door. The average highest temperature at the 1.2 m height was about 70 ℃. Related Articles | Metrics

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Research on fire breaking simulation training device of anti-theft door ZHANG Lei, RUAN Zhen, HONG Ying-zheng 2020, 39 (5):  696-699.  Abstract ( 1769 )   Against problems of the fire rescue and breaking simulation training device of anti-theft door such as the single function and insufficient effect, through the research of multi-functional scene interactive simulation technology and practical application technology, a fire rescue simulation training device of anti-theft door is designed and manufactured. The device components were introduced, including anti-theft door base, lock breaking module, door breaking module, smoke releasing module, temperature sensing module, combustible gas simulation module and timing module. Explained how to perform anti-theft door fire breaking training using the device, and the breaking and rescue procedure under different types of fire. It can simulate the real scene environment of different kinds of anti-theft door breaking and rescue, and each breaking module is replaceable. It can be used for firefighters to carry out a variety of anti-theft door breaking operation training. Related Articles | Metrics

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Research and practical application of actual mechanical advantage of hauling system in rope rescue SU Yu, LIU Li-wen 2020, 39 (5):  700-703.  Abstract ( 1819 )   In rope rescue, the actual mechanical advantage of hauling system is less than the theoretical mechanical advantage, resulting in an overestimation of the rescue capability. Experiments are designed to test the efficiency of various types of pulleys， the effect of progress capture device (PCD) on pulley efficiency， and the efficiency of carabiner and I'D instead of pulley. Through the T-Method ，calculated mechanical advantage of the hauling system by substituting the test result of pulley efficiency. To provide data support for accurately evaluating the actual mechanical advantage of hauling system in rope rescue，and improving rescue effciency. Related Articles | Metrics

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Characteristics of gases emission during lithium-ion batteries thermal runaway at high plateau LIU Yi, ZOU Xiao-long, CHEN Xian-tao, HE Yuan-hua, SUN Qiang 2020, 39 (5):  704-709.  Abstract ( 1769 )    In order to investigate the effectiveness of low-pressure and low-oxygen environment in high altitude airport on the parameters of jet flame temperature, heat release rate and flue gas composition in the thermal runaway behavior of lithium-ion batteries, the low-pressure test platform of lithium-ion battery was established to simulate the thermal runaway in high altitude airport (50 kPa) and plain airport (90 kPa) respectively. Four 18650 lithium-ion batteries were used as the experimental objects. The results showed that under the condition of 50 kPa, the damage degree of the cell, the heat release rate and the temperature of the jet flame decreases, among which the peak temperature of the jet flame reduces by about 241.3 ℃. Under the condition of 50 kPa, the concentration offlammable gases like CxHy and CO in the pyrolysis flue gas is higher, the highest concentration can reach 3 134.50×10-6 and 0.860% respectively, which increases with the increase of heat release rate.Under the condition of 90 kPa, the concentration of CxHy and CO decreases, which decreases with the increase of heat release rate. The combustion and explosion of the batteries is more violent under the condition of 90 kPa. The concentration of CO2 gas is the proof of the complete combustion of the substance. The highest concentration of CO2 gas under 90 kPa can reach 1.510 7% and it is higher than that under 50 kPa. Related Articles | Metrics

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Study on the change regulation of ac impedance in the thermal runaway process of lithium ion battery ZHAO Qi-chen, ZHANG Qing-song 2020, 39 (5):  709-712.  Abstract ( 1729 )   Through the self-designed ac impedance monitoring platform for thermal runaway of lithium ion battery, the impedance change rule in the process of thermal abuse of lithium ion battery was studied. Based on ac impedance technology and thermal runaway mechanism of lithium ion battery, the changes of impedance, phase Angle, ohmic resistance, polarization resistance and voltage with the surface temperature of lithium ion battery during thermal abuse were analyzed. The results show that in the process of heat abuse, the impedance of the lithium ion battery first decreases and then increases rapidly several minutes before the battery is disconnected, and the battery voltage remains stable until the battery is disconnected. The phase angle is going to decrease in the heat and then it's going to be stable. The impedance of 18650 lithium ion battery is mainly affected by ohmic resistance. The polarization resistance of lithium ion battery is stable before the battery breaks, which proves that there is no chemical reaction in the positive electrode material at this stage. Related Articles | Metrics

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Thermal safety analysis on ternary lithium ion battery under overcharge conditions ZHANG Qing-song, ZHAO Zi-heng, BAI Wei 2020, 39 (5):  713-717.  Abstract ( 1784 )   To explore the thermal safety issues of lithium ion battery under the condition of overcharge, 18650 type ternary lithium ion battery was used as the research object, and the thermal safety comparative experiment of batteries with different SOC of single and cyclic overcharged under the same conditions was conducted. The thermal stability and the severity of the consequences of the single and cyclic overcharged battery were analyzed by the time of battery to reach the initial burst and thermal runaway, the surface temperature of two nodes, and the battery surface temperature peak. The research was to provide evaluation indicators for evaluating the thermal safety of lithium ion batteries under overcharge conditions, and provide technical support for the inspection management of equipment using lithium ion batteries in civil air transportation and the standardized development of the industry. The result showed that, compared with cyclic overcharged batteries, the initial burst time of single overcharged batteries is 20% earlier and the temperature rises by 8%, and thermal runaway time is 15% ahead. After comprehensive analysis of battery thermal runaway phenomenon, maximum temperature and mass loss, it is concluded that the thermal stability of lithium ion battery after cyclic overcharged is better than that of single overcharged battery, but the consequences of thermal runaway are more serious. Related Articles | Metrics

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Design and application of smart inventories management system for emergency supplies JIA Yin, KONG Sheng-li, CHEN Bei, SONG Yu-qing 2020, 39 (5):  717-721.  Abstract ( 1811 )   Shanghai Chemical Industry Park was taken as an example. Based on the requirements of emergency response, combining with the development of smart park, the overall structure of the inventories management system was designed and the principle, target, function, database structure, reserve model was interpreted. Based on the receiving and handling platform, a management program was developed, using database, GPS, GIS and other technical means, to realize the dynamic management of emergency supplies, maintenance inspection, emergency procurement, transportation monitoring, and other functions. The research has strengthened the emergency inventories controlling position of chemical industry park emergency response center, made a contribution to the character of smart inventory management and scientific emergency response and also has positive promotion on developing modern emergency response. Related Articles | Metrics

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On the construction practice of "Four Unifications" of government full-time fire brigade CHEN Zhi-hong, YAO Wen-sheng, ZHANG Hu-lin 2020, 39 (5):  721-723.  Abstract ( 1864 )   In order to give full play to the full-time fire brigade of local government to supplement and assist the national comprehensive fire rescue team, promote the construction of a comprehensive coverage, overall development, practical and efficient urban and rural fire rescue system to meet the needs of "all kinds of disasters" and "major emergency". Taking the construction and management of full-time fire brigade of Zhangjiakou Municipal government as a sample, this paper puts forward the "four unified" management system of unified recruitment, unified distribution, unified guarantee and unified management, so as to promote the construction and management of full-time fire brigade of Zhangjiakou Municipal government. Related Articles | Metrics

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Influence of typical wood products on gasoline analysis and identification TIAN Jin-yang, LIU Shu-jun, WANG Ying, JI Bo-rui 2020, 39 (5):  724-726.  Abstract ( 1713 )   With more than 10 kinds of wood products such as oak floor and wood table as the research objects, SPME-GC /MS and SPME-GC×GC/MS were used to analyze the body samples of wood products and explore their influence on the analysis and identification of combustion-supporting agent gasoline at the scene of arson. The results showed that C2, C3, C4 alkyl benzene and alkyl naphthalene compounds, which were exactly the same as those in gasoline, were detected by SPME-GC/MS in the real wood table body samples. SPME-GC×GC/MS technique was used to analyze the solid wood table body samples with large gasoline interference, and the results of comparative analysis were given, which eliminated the interference of such samples on the gasoline analysis with high accuracy. Related Articles | Metrics

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Research on smoke trace characteristics of corner fire in single room WANG Xin-yu, WANG Yun, ZHANG Jin-zhuan, LI Yang, MENG Wei 2020, 39 (5):  727-730.  Abstract ( 1760 )   In order to study the smoke trace characteristics of corner fire in single room, this paper adopts one third size fire experiment to restore the corner fire in the room, measures the temperature of different points on the wall surface and the velocity of smoke spread, and studies the smoke trace characteristics when the fire source was in different positions. PyroSim is used to simulate the smoke spreading process. Results shows that, when the fire source is at the center of the room, a circle trace forms on the ceiling; when the fire source is at the corner, trace forms on both side wall and ceiling corner; the temperature and smoke spreading speed of the corner fire are higher than that of the fire at the center of the room; the experiment and simulation are consistent. The experiment conclusions can provide theoretical and experimental basis for the fire investigation of the corner fire. Related Articles | Metrics

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Investigation of vehicle fire caused by engine wading ZHANG Liang, ZHANG De-sheng, WANG Xin, LI jian 2020, 39 (5):  730-733.  Abstract ( 1743 )   Fire investigation of vehicle fires caused by engine wading, including passenger car fire and special car fire are introduced. It is analyzed that, the direct fire cause is engine block damage, and the leaked oil is burnt, while the basic reason is intake cylinder after engine water intake, and high temperature vaporized water accumulated in the top space of piston causing bending and fracture of connecting rod, and breaking the cylinder block. Based on the analysis, the characteristics and investigation methods of wading vehicle fires are summarized.  Related Articles | Metrics

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Technical analysis of LPG gas explosion accident in dining places WANG Zhi-wen 2020, 39 (5):  734-738.  Abstract ( 1791 )   Catering places are crowded places, and the current status of the use of liquefied petroleum gas in restaurant places is related to public safety. In order to prevent liquefied petroleum gas explosion accidents in such places, reduce accident losses, this article conducts an on-site survey of a liquefied petroleum gas leak and explosion accident in a restaurant, the accident has been technically analyzed by means of on-site analysis of explosion accidents, equivalent energy analysis, gas diffusion scene analysis, ignition source analysis, etc.， the cause and course of the accident is identified, and similar accident prevention suggestions are put forward. Related Articles | Metrics