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15 May 2024, Volume 43 Issue 5 Previous Issue    Next Issue

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New energy fire prevention and control technology research progress Zhuo Ping, Zhang Wang, Zhang Liang, Chu Yuxi, Chen Ye, Zhang Jin, Wang Yue, Li Ziting, Chen Hongguang, 2024, 43 (5):  578-589.  Abstract ( 1037 )   This paper summarizes the research progress of new energy fire prevention and control technologies in recent years. By reviewing and analyzing the basic theoretical research and domestic and foreign technological status, it summarizes the main technological progress of fire prevention and control in the fields of wind power, photovoltaic power generation, lithium-ion battery energy storage, power batteries and hydrogen energy, sorting out the difficult and blocking fire prevention and control problems that still need to be solved, and clarifying the direction of future development, so as to provide guidance for fire prevention and control of China's new energy industry, and to provide assistance for the safe and healthy development of the industry. Related Articles | Metrics

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A review of thermal runaway monitoring parameters of lithium-ion batteries Wang Fang, Chen Wentao, Ma Biao, Liu Shiqiang, 2024, 43 (5):  590-596.  Abstract ( 200 )   Lithium ion battery is widely used in energy storage field because of its advantages of high energy density, low self discharge rate, long cycle life and large output power. However, due to its intrinsic instability, more and more accidents occur frequently in energy storage. From the point of view of thermal runaway and fire propagation, this paper explores the mechanism of thermal runaway. Based on the characteristics of thermal runaway such as gas generation composition and content, expansion force, surface temperature and voltage-drop, the existing early warning (external) methods are summarized. On this basis, the development idea of early warning (external) of battery thermal runaway in the future is proposed, which provides ideas for early monitoring and early warning of thermal runaway of lithium battery. Related Articles | Metrics

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Review of research progress on the battery thermal runaway induced by nail penetration Zhang Lei, Liu Yanhui, Ye Congliang, Zhou Yuxin, Huang Xinyan, 2024, 43 (5):  597-604.  Abstract ( 152 )   Nail penetration test is one of the most important methods to investigate the failure mechanisms and thermal runaway features of lithium-ion batteries. This paper summarizes the nail penetration testing methods commonly used by researchers and studies the influence of different variables, including penetration depth, velocity, location, needle material and diameter, on the short-circuiting and thermal runaway behaviour in batteries under nail penetration-induced damage. The results reveal a direct proportionality between the depth of nail penetration and the severity of thermal runaway behaviour in batteries. The speed of nail penetration has no significant impact on thermal runaway. When nail penetration occurs in regions with dense active materials or near the electrode, the thermal runaway in batteries becomes severer. As for the variables related to the nail itself, such as material and diameter, they exhibit a dual effect on thermal runaway behaviour in batteries, requiring separate analysis of heat generation and dissipation considering the actual conditions. Finally, by summarizing the influence of various factors on thermal runaway in batteries, new insights are proposed to mitigate lithium-ion battery thermal runaway and update safety testing procedures, which can provide guidance for subsequent innovative research work. Related Articles | Metrics

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Review on thermal runaway behaviors and fire hazards of lithium-ion batteries Zhou Zhizuan, Wang Boxuan, Song Lulu, Yang Lizhong 2024, 43 (5):  605-612.  Abstract ( 168 )   As an efficient and clean energy storage carrier, lithium-ion batteries play an important role in achieving the goal of carbon neutrality due to their advantages of high energy density, low self-discharge, fast charging and long cycle life. However, due to the activity of the materials and the flammability of the electrolyte, lithium-ion batteries fall into thermal runaway easily under abuse conditions, and the generation of a large amount of heat and flammable gases can cause fire and even explosion accidents. The potential safety issues and high fire risks of lithium-ion batteries have limited their large-scale application in electric vehicles and electrochemical energy storage systems. Aiming at the thermal runaway and fire issues of lithium-ion batteries, this paper reviews the relevant research on the characteristics of thermal runaway in lithium-ion batteries under thermal abuse, and summarizes the research progress from the thermal stabilities of battery materials to the behaviors of thermal runaway in the single battery, then to the evolution characteristics of TR propagation of the battery module. Furthermore, the prevention and inhibition technologies of thermal runaway and its propagation are analyzed, and the research suggestions and prospects are proposed in this paper. Related Articles | Metrics

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Materials for insulating lithium-ion battery thermal runaway: Review and prospect Zhou Yuxin, Liu Yanhui, Tang Liang, Ye Congliang, Zhang Lei, Hao Menglong, Huang Xinyan 2024, 43 (5):  613-619.  Abstract ( 800 )   Environmental and energy issues have increased the demand for advanced energy storage technologies, such as lithium-ion batteries, as a key component in this round of new energy revolution. However, lithium-ion batteries face safety issues, especially fire hazards caused by large-scale thermal runaway and its spread. This paper addresses these challenges and summarizes the methods of applying insulating materials to prevent thermal runaway and its propagation. It summaries the functions of different insulation materials in terms of heat absorption, heat insulation, and their combination. Moreover, it reviews the numerical models for studying battery thermal runaway and fire and its preventive measures at the system level. The aim of this paper is to clarify the research and development of insulating materials and provide ideas for future innovation. Related Articles | Metrics

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Research progress in thermal management system of lithium-ion battery on liquid cooling Wang Sheng, Li Xin, Jiang Wei, Li Jinbei 2024, 43 (5):  620-625.  Abstract ( 106 )   Lithium-ion battery is widely used in electric vehicles and energy storage because of its excellent electrochemical characteristics, but its performance is greatly affected by working temperature. Therefore, designing the reasonable and effective thermal management system is a key technology to promote the development of lithium-ion battery. This paper summarizes the common thermal management systems, including the research status, advantages and disadvantages of air cooling, phase change material cooling, heat pipe cooling and liquid cooling. Especially it introduces the current optimization methods of liquid cooling technology for the direct contact liquid cooling and indirect contact liquid cooling. For the limitations of a single thermal management system, it also analyzes the thermal management research status of liquid cooling combined with other methods from the perspective of coupled thermal management system. Finally, the direction of comprehensive optimization and intelligent control for liquid cooling management system is proposed, and the liquid cooling combining with the passive heat dissipation and linking of the battery management system has great development potential. Related Articles | Metrics

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Battery thermal runaway-thermal management integrated layout decision based on aerogel and phase change material sandwich structure Ding Yongxin, Ma Fei, Zhao Jun, Dai Chuanshan, 2024, 43 (5):  626-633.  Abstract ( 854 )   In order to improve the comprehensive effect of thermal runaway suppression and thermal management heat dissipation of battery modules, this study designed a thermal management system with phase change material aerogel sandwich structure between batteries and set up different thickness layout forms. The comprehensive benefits of each layout were obtained and compared by classifying the data and performing Min-Max normalization and giving different weights to accumulate. The results show that the pure aerogel is the best for restraining the uncontrolled heat transmission. Compared with air cooling, it can extend the time of the last battery in the module to generate heat out of control, but the heat dissipation effect of battery thermal management is significantly worse; For strengthening heat management and heat dissipation, pure phase change material arrangement has the best effect. Compared with air cooling, it can reduce the maximum temperature of battery in a discharge cycle by more than 20 ℃, but its suppression of heat runaway propagation is significantly weaker than pure aerogel arrangement; For the comprehensive benefits of thermal runaway and thermal management, the PCM-aerogel-PCM layout is more widely applicable than other layout forms. It ensures the effect of restraining thermal runaway of the battery while strengthening the heat dissipation of the battery during normal operation to maximize the overall benefits. Related Articles | Metrics

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Research on the explosive combustion process of thermal runaway combustible gas of lithium battery for energy storage Xu Yibo, Zhu Yanli, Yang Kai, Zhang Mingjie 2024, 43 (5):  634-640.  Abstract ( 104 )   In order to effectively prevent and control safety accidents in lithium iron phosphate battery energy storage power stations, it is of utmost importance to evaluate the explosion risk of gases escaping from lithium iron phosphate batteries after thermal runaway. Based on the preliminary experimental results, this article prepares premixed gases with different volume ratios of combustible gases and air released from thermal runaway of lithium iron phosphate batteries at different states of charge (SOC), and conducts research on the detonation process of premixed gases. The experimental results show that the explosion pressure of premixed gas shows a pattern of first increasing and then decreasing with the increase of combustible gas volume fraction, and has little correlation with SOC; The maximum pressure pmax of premixed gas deflagration increases with the increase of the proportion of combustible components such as H2, CO, and CH4 in the premixed gas; By conducting a 20 L ball explosion limit test, the explosion limits of premixed gases prepared for batteries with different states of charge were obtained; Comparing two numerical calculation methods for explosion limits, it is believed that the Le Chatelier formula is suitable for calculating the lower explosion limit, while the adiabatic flame temperature method is suitable for calculating the upper explosion limit; According to the explosion index Kg, it can be seen that the destructive effect caused by thermal runaway gas explosion accidents in lithium iron phosphate batteries increases with the increase of SOC, indicating that high SOC lithium iron phosphate batteries are highly prone to fire and explosion hazards. It is recommended to take measures such as installing combustible gas concentration monitoring devices to prevent and reduce the potential risks of the battery. Related Articles | Metrics

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An investigation of the influencing factors on the thermal runaway propagation characteristics of lithium iron phosphate batteries Song Laifeng, Tian Jiamin, Liu Yong, Wang Qingsong 2024, 43 (5):  641-650.  Abstract ( 836 )   The main factors affecting the thermal runaway propagation of LiFePO4 batteries are studied experimentally, and the thermal runaway propagation experiments are carried out by designing battery modules with different states of charge, spacing and electrical connections. The influence of different factors on the thermal runaway propagation is analyzed according to the parameters of the battery surface temperature, the change of the battery voltage and the mass. The results show that the influence of different factors on thermal runaway propagation is in the following order: state of charge, cell spacing, and electrical connections. Meanwhile, it is also obtained that the main heat transfer mode leading to thermal runaway propagation is heat conduction, with heat transfer to the downstream battery as the main heat transfer path. Related Articles | Metrics

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The application of tactile sensing technology in early thermal runaway warning of lithium-ion batteries Tang Liang, Shang Wenyan, Zhang Shaoyu, Chen Zhaofan 2024, 43 (5):  651-655.  Abstract ( 926 )   This study focuses on the research of tactile sensing technology in the safety monitoring of thermal runaway in lithium-ion batteries for energy storage applications. A 52 Ah prismatic LFP (Lithium Iron Phosphate) battery is selected as the subject of investigation. Thermal runaway in individual cells and battery modules is triggered using a heating plate, and a combination of force, electrical, and thermal real-time monitoring methods is employed to thoroughly analyze the thermal runaway processes at both the single-cell and module levels. In the single-cell thermal runaway experiment, when the internal short circuit occurs due to the gradual increase in battery temperature caused by the heating plate, the swelling force sharply increases at 112 seconds, preceding noticeable changes in voltage and temperature by 8.9 min. Further extending to the module-level thermal runaway experiment, during the phase where heat propagation leads to thermal runaway in adjacent cells after triggering the end cell, the swelling force exhibits rapid growth even before any significant temperature and voltage characteristics appear, identifying signs of thermal runaway approximately 6.0 min earlier than voltage and temperature measurements. This effectively demonstrates the importance of incorporating force dimension data monitoring in enhancing the early warning capability for thermal runaway in energy storage lithium-ion batteries. Related Articles | Metrics

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Study on theoretical analysis method of thermal runaway liquid nitrogen cooling inerting of LPF batteries Wang Yue, Zhang Shaoyu, Chu Yuxi, Chen Ye, 2024, 43 (5):  656-662.  Abstract ( 92 )   The traditional commercial fire extinguishing agent is not effective in suppressing the thermal runaway fire and reignition of lithium ion battery. Liquid nitrogen is an efficient fire extinguishing agent, and its cooling effect on restraining thermal runaway of lithium-ion batteries has been verified by experiments of many research institutions. However, at present, there is a lack of theoretical analysis methods for the influence of liquid nitrogen fire extinguishing dosage and fire extinguishing efficiency. Based on the theoretical analysis of liquid nitrogen fire extinguishing mechanism, the theoretical analysis and calculation method of liquid nitrogen cooling and inerting are studied and determined. In the method, experimental studies on thermal runaway heat release, heat absorption of liquid nitrogen, and inert amount of liquid nitrogen were carried out, and the effectiveness of the method was verified by full-scale experiments. Taking the thermal runaway of 280 Ah lithium iron phosphate battery as an example, the minimum amount of liquid nitrogen for inerting explosion suppression and cooling is calculated according to the theoretical analysis method. After 83.39 kg of liquid nitrogen was applied to the explosion test chamber with an effective volume of 38.88 m3, the explosion occurred 48 times at a 24-hour interval. The effectiveness and rationality of the theoretical analysis method are effectively verified by practical cases, and the proposed theoretical analysis method provides evaluation means and methods for the design and effectiveness analysis of liquid nitrogen fire suppression and explosion suppression, so as to further effectively enhance the safety of lithium iron phosphate battery storage system. Related Articles | Metrics

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Feasibility study of lithium-ion battery for energy storage in compulsory supervision Wang Xiaodong, Zhao Lixiang 2024, 43 (5):  663-666.  Abstract ( 61 )   Based on the significant increase in the proportion of lithium-ion batteries for energy storage in new energy storage and the frequent accidents of energy storage power stations caused by lithium-ion battery safety problems, in order to improve the safety access level of lithium-ion batteries for energy storage, we should strengthen industry management and implement reasonable regulatory measures. This paper describes the development status of the former lithium-ion battery industry for energy storage, relevant foreign standards and regulatory models, briefly analyzes the current regulatory models of lithium-ion batteries in other fields and the technical terms of mandatory standards for lithium-ion batteries for energy storage, and gives reasonable suggestions for subsequent mandatory supervision. Related Articles | Metrics

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Study on fire suppression performance of cellulose based hydrogel for lithium iron phosphate battery Zhang Haiwen, Xing Zhixiang, Wu Jie, Lu Wanzheng 2024, 43 (5):  667-673.  Abstract ( 791 )   In recent years, lithium-ion battery fire accidents have occurred frequently, and the consequences of fire accidents are also extremely serious. Developing high-efficiency fire extinguishing agents for lithium-ion batteries has become one of the research hotspots. In this paper, a kind of cellulose based flame-retardant hydrogel was synthesized by using polymer materials, crosslinking agent and flame retardant, and mixed with water in proportion to form a hydrogel fire extinguishing agent. The fire extinguishing experiment shows that, compared with pure water mist, this kind of hydrogel extinguishing agent can reduce the surface temperature of the battery more quickly and put out the open fire. At high temperature, it can cover the battery surface, play a role of continuous cooling, and effectively reduce the height of the second temperature peak. Moreover, the addition of flame retardants can further increase the cooling rate, which has a good fire extinguishing effect on lithium iron phosphate batteries and can be used for emergency fire extinguishing of lithium-ion batteries. Related Articles | Metrics

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A two-level diagnosis method for energy storage battery anomalies based on battery module reconfiguration Wang Tinghua, He Darui, Wu Jingyun, Yan Bo 2024, 43 (5):  674-679.  Abstract ( 61 )   Accurate monitoring of energy storage battery degradation anomalies is the key to ensure the safe operation of battery energy storage systems. The adoption of reconfigurable battery topology is a major trend for future battery energy storage systems, and existing data-driven battery health assessment methods primarily emphasize improvements at the algorithmic level, making it difficult to leverage the advantages of this framework. Aiming at this problem, this paper proposes a two-level diagnosis method for abnormal batteries; the primary diagnosis adopts a least-squares support vector machine classification model trained by full-condition full-life cycle simulation dataset to screen out the suspected abnormal battery modules; the secondary diagnosis adopts a health state estimation model based on residual connection and gated cyclic unit to realize the accurate estimation of the health state of the storage batteries and to verify the results of the primary diagnosis. The experimental results show that the diagnosis method proposed in this paper has a high accuracy rate in both diagnostic links, and realizes the accurate monitoring of energy storage battery attenuation anomalies on the basis of reconfigurable battery topology. Related Articles | Metrics

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Simulation study of variable cross-section channel liquid cooling based on reversible circulation Ou Fan, Li Xin, Jiang Wei, Li Jinpei, Dong Di 2024, 43 (5):  680-686.  Abstract ( 48 )   Taking 280 Ah square lithium iron phosphate battery as the research object, this paper designed a variable section symmetrical flow channel liquid cooling plate to conform the heat generation characteristics of the large-capacity battery pack, established a liquid cooling simulation model of lithium-ion battery pack, and adopted a reversible liquid cooling method. The cooling effect of the battery pack under different cooling methods, the influence of the inlet temperature of the coolant and the turning time of the reversible cycle on the heat dissipation performance of the battery pack were studied. The results show that the symmetrical flow channel with variable cross section can improve the heat dissipation performance of the battery located in the center of the battery pack, so as to balance the temperature inconsistency caused by different positions. The bidirectional reversible circulation mode reduces the maximum surface temperature of the battery pack by 17.8 ℃ compared with the condition of only natural convection. In addition, in the proposed liquid-cooled plate structure, the inlet temperature of the coolant mainly affects the maximum temperature of the battery pack surface, and the turning time of the reversible cycle mainly affects the temperature uniformity of the battery pack. Related Articles | Metrics

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Research on strategies and effects of thermal runaway control after the rupture of lithium iron phosphate battery safety valves Chen Shuwen, Liu Kai, Song Zhenxuan, Lv Nawei, Jiang Xin, Jin Yang 2024, 43 (5):  687-692.  Abstract ( 98 )   In order to study the effect of thermal runaway suppression after the rupture of lithium iron phosphate battery safety valves, an experimental platform for detecting thermal runaway characteristics was constructed. Firstly, the thermal runaway jet of the battery was divided into stages, and then the influence of cutting off power supply at different times on the phenomenon characteristics, temperature, and combustible gas concentration characteristics of thermal runaway was compared and analyzed. The results show that after the safety valve of the lithium iron phosphate battery is opened, there are two jettings, with a time interval of about 10 s. When the safety valve opens, accompanied by a small amount of gas ejection, the power supply is immediately cut off, and the internal reaction stops accordingly, and there is no second ejection from the valve. After the second jetting, the battery enters a completely thermal runaway state. If the power is cut off immediately at this time, the surface temperature of the battery continues to rise for a long time, with the highest temperature reaching 93 °C. If the power is cut off again 2 minutes after the second jetting, the surface temperature of the battery continues to rise to 200 °C. Compared with cutting off the power during the second jetting, the maximum temperature difference is 107 °C, and the maximum differences in H2 and CO volume fraction reach 7.09×10-4 and 3.28×10-4, respectively. In response to the thermal runaway warning after the safety valve opens, effective warning and thermal runaway suppression methods should act between the first and second jettings, which can prevent the rapid rise of battery temperature, reduce the ejection of combustible gases, and reduce the risk of fire and explosion. Related Articles | Metrics

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Study on the risk of hydrogen leakage leading to explosion of FCV hydrogen storage system Zhang Lei, Ma Qiujv, Huang Hao, Zhang Yongfeng 2024, 43 (5):  693-697.  Abstract ( 81 )   The hydrogen leakage and ignition test bench of fuel cell vehicle（FCV） hydrogen storage system was built in this paper, and then high-pressure hydrogen leakage ignition experiments were carried out. The risk parameters of hydrogen jet flame morphology, flame length, and typical position temperature, thermal radiation flux were collected. In addition the numerical simulation of hydrogen leakage leading to explosion in the FCV passenger compartment was studied. As the result shows, The leakage time of 0.4 L/0.84 MPa high-pressure hydrogen gas through a circular hole with a diameter of 6 mm was only 80 ms. The hydrogen jet flame length was 1.4 m horizontally burning continuously only for 0.3 second. The highest hydrogen combustion intensity was at a distance of about 1.0 m from the leakage port, and the maximum thermal radiation flux collected was 0.27 kW/m2. The numerical simulation results show that after hydrogen leaking and catching fire in the passenger compartment, the entire cabin was ignited within only 28 ms. The highest temperature in the cabin exceeded to over 2 000 ℃ and the maximum pressure exceeded to over 0.5 MPa. The risk of hydrogen leakage of vehicle hydrogen storage system leading to combustion and explosion is extremely high which seriously endangering the safety of passengers. FCV safety design should be strengthened to avoid such accidents. Related Articles | Metrics

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Prediction of hydrogen jet diffusion based on physics-informed deep learning Zhang Xinqi, Shi Jihao, Chen Guoming 2024, 43 (5):  698-703.  Abstract ( 76 )   Hydrogen is one of the most flammable and explosive fuels. Once leaked, it can easily diffuse and potentially cause a fire. Real-time and accurate prediction of hydrogen diffusion is essential for predicting spatial concentration, which enables fire prevention of hydrogen facilities. In this study, a physics-informed deep learning model was proposed to effectively and accurately predict hydrogen concentration and velocity using sparse sensor data. The dependency between sensor data was learned by the graph neural network, and the physical differential equations of hydrogen diffusion were solved by graph nodes. The computed residuals were then used to optimize the parameters of the deep learning model. Public experimental data was applied to validate the performance of our proposed model. The results show that compared with the existing methods, the proposed method not only has real-time capability, but also predicts hydrogen concentration and velocity more accurately. This study provides accurate and real-time concentration and velocity prediction for hydrogen diffusion, facilitating hydrogen fire prevention. Related Articles | Metrics

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Hydrogen jet fire accident consequences predicting method based on deep learning He Xu, Kong Depeng, Yang Guodong, Yu Xirui 2024, 43 (5):  704-708.  Abstract ( 74 )   As one of the most important supporting infrastructures for the hydrogen energy application industry, hydrogen refueling station (HRS) is characterized by the presence of large quantities of high-pressure hydrogen accompanied by significant leakage risks. Once the high-pressure hydrogen leaks, it is very easy to form a jet fire, which poses a serious threat to the structures in the HRS as well as to the safety of people's lives and properties. In order to realize the fast and accurate prediction of the consequences of hydrogen jet fire accidents, a neural network-based surrogate model accident consequence prediction method is proposed, which has a significant time-saving advantage over the traditional numerical simulation methods. The method constructs a hybrid surrogate model based on adversarial generative network and long and short-term memory neural network, and the training samples generated by numerical simulation are used to train the surrogate model, and the completed surrogate model can predict the temperature distribution after the jet fire accident caused by the high-pressure hydrogen leakage from HRS. The accuracy of the prediction results of the surrogate model was quantitatively analyzed using the fuzzy C-means and the Structure Similarity Index Measure, and the results showed that the surrogate model for predicting the consequences of hydrogen jet fires can greatly improve the efficiency of consequence prediction under the premise of guaranteeing the acceptable prediction accuracy, realizing the spatio-temporal and fast prediction of the consequences of hydrogen jet fires in HRS. Related Articles | Metrics

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Experimental study of hydrogen storage cylinder extrusion for fuel cell vehicles based on typical traffic accidents Chen Xiangyang, Zhang Peng, Huang Shulong, Hao Dong, 2024, 43 (5):  709-715.  Abstract ( 702 )   As one of the core subsystems of fuel cell vehicles, the on-board hydrogen system, once subjected to a large extrusion pressure in traffic accidents, may lead to the failure of key components, resulting in a large amount of hydrogen leakage, which may lead to more serious consequences, so the evaluation of the extrusion resistance of the on-board hydrogen storage cylinders is an important task to further improve the safety evaluation system of fuel cell vehicles. This paper establishes a squeeze evaluation method for on-board hydrogen storage cylinders, describes in detail the four aspects of the squeeze evaluation method, and carries out the squeeze test verification of on-board hydrogen storage cylinders, analyzes the impact of squeezing on the hydrogen storage cylinders through the test data, and quantitatively evaluates and analyzes the safety of the hydrogen storage cylinders after squeezing, so as to provide a reference for the safety evaluation of the on-board hydrogen system. Related Articles | Metrics

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Potential failure mode and cause analysis of onboard hydrogen system of fuel cell vehicle Dong Wenyan, Chen Xiangyang, Yang Zirong, Hao Dong, 2024, 43 (5):  716-721.  Abstract ( 524 )   The safety of onboard hydrogen systems is one of the core technical indicators of fuel cell vehicles (FCVs), and its safety guarantee is an important prerequisite for the large scale of commercialization of FCVs. Focusing on the safety of the onboard hydrogen system, this paper introduces the composition of the onboard hydrogen system and analyzes the failure modes and causes of the onboard hydrogen system and its components. This paper summarizes the failure consequences of the onboard hydrogen system and discusses the urgent need for the improvement in the fire safety of FCVs at this stage. The analysis shows that the potential failure modes and causes of onboard hydrogen systems mainly include sealing, vibration fatigue, mechanical shock, collision, rapid hydrogen charging and discharging fatigue, thermal damage, and control system function failure, and the main consequence of failure is hydrogen leakage. In extreme scenarios, "hydrogen leakage+confined / semi-confined space+ignition source" will cause fire or even explosion, which will seriously threaten the safety of public life and property. Therefore, it is recommended to improve the safety level of onboard hydrogen systems from many aspects, such as optimizing safety design and verification, improving hydrogen leakage monitoring and gas source control technology, carrying out quantitative evaluation of failure disaster hazards, and strengthening fire prevention and control technology. Related Articles | Metrics

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Study on combustion characteristics of ternary lithium battery-electric bicycle fires He Xuechao, Liu Zhenfei, He Jin 2024, 43 (5):  722-725.  Abstract ( 71 )   The development and spreading process of electric bike fire is studied by carrying out physical combustion test on a ternary lithium battery-electric bicycle，and typical features such as combustion phenomenon, temperature and smoke change are analyzed. The test results show that the e-bike fire develops rapidly, and the combustion process is accompanied by jet fire and explosion phenomena. The fire plume temperature measured at 1 m above the ground could reach up to 730 ℃, which corresponds to a maximum heat release rate of 1 290 kW. By evaluating the toxicity of the smoke, an effective dose percentage (FED) value of 1.8 is calculated, which indicates that about half of the people in this fire environment would be killed due to smoke toxicity hazards. In addition, the generated smoke contains a large amount of flammable and explosive gases, among which H2 content is highest at 2 300 μL/L. Related Articles | Metrics

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Research on fire risk and prevention strategies of sinking well type mechanical three-dimensional parking garage Zhou Guanglian 2024, 43 (5):  726-729.  Abstract ( 75 )   On the basis of thorough research, combined with the case of electric vehicle fires and the research results of others, this study conducted a detailed analysis of the fire protection design of a sunken well type mechanical parking garage in use. It was found that there are main risks such as the inability to separate fire protection units, inaccurate fire linkage, uncertain fire extinguishing efficiency, and difficulty in accident disposal. Through theoretical research and comparative data analysis, early warning detection, fire separation, graded response, structural fire resistance, and fire rescue are proposed. This study provides a basic idea for the next step of conducting relevant physical experiments, fire protection design, and specification revision. Related Articles | Metrics

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Research on fire causes analysis technology of shared electric bike based on cloud data analysis Chen Ke, Huang Meng, Zhang Ruoheng, Zhang Bin, Song Jianxun, He Bing 2024, 43 (5):  730-736.  Abstract ( 852 )   Shared electric bikes are equipped with operation data collection and cloud recording functions, and revealing the laws of how this cloud data changes with the fire location and ignition mode can provide new evidence for the identification of fire cause and product quality management. In this paper, the characteristics and variation rules of V-t curve of the cloud data during the combustion process of shared electric bikes are studied through experiments involving open flame ignition, thermal runaway of the power battery, and electrical circuit short-circuit faults. The results show that: Open flame and short-circuit first cause the data transmission line to be disconnected, and the vehicle's voltage data drops to zero rapidly after diving, with a rate of voltage decline exceeding 500.56 mV/s; After thermal runaway of the power battery, the vehicle's voltage data drops slowly after diving, with a voltage decline rate of 20.02 mV/s, and a short-term voltage rebound phenomenon occurs during the decline; When conducting fire investigation on shared electric bikes, clues for the identification of the cause of fire can be provided by retrieving cloud data and analyzing the V-t curve characteristics. Related Articles | Metrics

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Research on bottom collision safety assessment technology for new energy vehicles Yan Pengfei, He Xing, Gao Yan, Liu Yifan, 2024, 43 (5):  737-742.  Abstract ( 736 )   This article analyzes complex bottom collision scenarios and builds a bottom protection safety evaluation technology scheme based on bottom collision conditions, combined with experimental and simulation methods, revealing the mechanism of bottom collision obstacles and battery systems. Based on the linkage analysis of experiments and simulations, an optimal evaluation plan covering multiple damage factors for structural design optimization was created, which provides important support for the reasonable extraction of complex scene working conditions and effective characterization of bottom collision safety issues in new energy vehicles. Related Articles | Metrics

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Research on early warning prevention and control technology of vehicle power battery pack storage process Xu Lei, Zheng Wei, Zhao Bing 2024, 43 (5):  743-749.  Abstract ( 64 )   In order to study the thermal runaway fire process of the vehicle power battery pack storage device, which is along with early-warning and prevention ability. The significance of the early warning signal sequence of thermal runaway fire was analyzed through real tests and simulation of the vehicle power battery pack, and the temperature distribution near the spread and spread of the battery pack fire was studied. The results show that: The FDS simulation method can effectively simulate the thermal runaway fire in the storage of vehicle power battery pack. The heat release rate and the smoke spreading process are similar to the test process. Through the simulation of the temperature field distribution in the modular thermal runaway scenario, the fire can be controlled in the compartment of the box through effective separation measures and will not affect other spaces and cause serious disasters. The response of different sensors was tested. The 32.8 kHz ultrasonic sensor still collected the thermal runaway state of the battery earlier, significantly earlier than the image and smoke sensors, and the ultrasonic sensor had a more significant detection effect in a relatively closed space. Related Articles | Metrics

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Research on method to measure internal pressure of lithium-ion battery during thermal runaway Liu Enhong, Huang Wensheng, Xu Chengshan, Feng Xuning 2024, 43 (5):  750-755.  Abstract ( 853 )   As the core component of strategic industries like new energy vehicle, lithium-ion battery has received widespread attention for its safety. Battery safety incidents often begin with thermal runaway, which means chain reactions occurred with production of heat and flammable gas. A test for internal pressure of lithium-ion battery during thermal runaway is proposed, based on which experiments are conducted. On the basis of accurate data from the test, process of thermal runaway is depicted in detail, finding that gas production can quickly change internal pressure, and the gas of 1 000 ℃ and 0.25~0.50 MPa show distinctive impact on heat transfer and dissipation. Meanwhile, the change of internal pressure is earlier than that of the voltage and the temperature. This test plays an important part in researches on thermal runaway mechanism and improving battery safety technologies like thermal runaway early warning and venting valve. Related Articles | Metrics

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Discussion on hazard assessment scheme for thermal runaway of electric vehicle Zhang Liang, Zhao Zhiwei, Zhang Desheng, Huang Meng, Zhou Sida, Yang Shichun, Liu Guofang 2024, 43 (5):  756-761.  Abstract ( 710 )   With the increase in the number of electric vehicles, fire accidents caused by thermal runaway of power batteries have occurred from time to time. Evaluating the risk of thermal runaway is one of the important means to improve the safety performance of electric vehicles, but there is no quantitative evaluation method in the industry. In response to the above issues, an electric vehicle combustion test platform has been established, and a large number of thermal runaway induced electric vehicle fire simulation tests have been conducted. The following reference indicators and some potential indicators that can be used for evaluating the harmfulness of electric vehicle thermal runaway have been extracted: the time interval from the start of the test to the thermal runaway of the power battery can be used as an effective indicator for battery failure warning; The time interval from thermal runaway to vehicle fire and the temperature inside the vehicle can be used as safety indicators for passenger evacuation; The time when the volume fraction of smoke exceeds the standard and its relationship with the time of ignition can be used as a hazard indicator for toxic gases in the cab; The volume fraction of combustible gases inside the vehicle and the intensity of thermal radiation outside the vehicle can be used as indicators to evaluate the risk of explosion and ignition of adjacent vehicles. By proposing the above evaluation indicators, reference can be provided for the subsequent formation of quantitative evaluation methods and related standards. Related Articles | Metrics

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Safety analysis of electric shock during fire suppression activities involving photovoltaic system Wang Yue, Zhang Wang, Lv Dong, 2024, 43 (5):  762-766.  Abstract ( 85 )   Because the photovoltaic power generation system will continue to generate electricity in the presence of light, it can not cut off the power supply, and the use of traditional fire extinguishing agents will cause electric shock accidents. In order to analyze the electric shock risk of high voltage DC side of photovoltaic power generation system with live extinguishing agent, a test platform and test method are proposed. Through the test, it can be found that: foam, water-based fire extinguishing agent, carbon dioxide and other fire extinguishing agent in the DC side of 300~1 500 V high voltage, due to the insulation of the fire extinguishing agent, it cannot form a circuit and therefore lacks conductivity. Fire hydrant water gun and multi-functional water gun live rescue process gun head with DC voltage, the gun head voltage changes with the flow and distance, because the center of the water column of the multi-functional water gun is air, significantly reduce the conductivity of the water column, multi-functional water gun than fire hydrant water gun is more suitable for fighting the photovoltaic power generation system live fire. The calculation method of water conductivity of multi-functional water gun in the process of electricized rescue is obtained, and the safety distance of primary and secondary electricized rescue of water gun is calculated and determined. In the live rescue process, the rescue distance must be strictly greater than the first-level safety rescue distance, and corresponding protective measures must be taken to prevent electric shock within the second-level rescue distance. Related Articles | Metrics