Effect of CO_2 on explosion limits of flammable gases in goafs

In order to reduce the number of accidents due to explosions of flammable gases in the goaf of coalmines,the conditions for explosion of flammable gases and their explosion limits,affected to a considerable extent by CO2,are explored.With the use of our experimental equipment suitable for the study of explosion of polybasic explosive gas mixtures,we investigated the effect of CH4/H2=10/1 and CH4/C2H4=10/1 gases mixed with CO2 on their explosion limits.The results indicate that after adding CO2,the explosion limit of the CH4/H2(or C2H4) =10/1 gas mixtures decreased markedly with increasing amounts of CO2.When the amount of CO2 exceeded 25%,the CH4/C2H4=10/1 flammable gas mixture did not lead to explosions.Similar results were obtained when the amount of CO2 exceeded 23% in the CH4/H2=10/1 flammable gas mixture.We also compared the explosion limits and the explosion suppression effect of N2 or CO2 on the explosion limits of the CH4+CO and CH4+C2H4 dual explosive gas mixtures.Along with the increases in the amounts of CO2 or N2,the area of the explosion limits of gas mixtures decreased.Under the same conditions,the explosion suppression effect of CO2 was greater than that of N2.CO2 has clearly the better suppression effect on the explosion of flammable gases in goafs.

Theoretical and Experimental Study of Explosion Limits and the Inhibition of Flammable Refrigerants

In this study, we analyze factors affecting the explosion limits of flammable refrigerants. We conclude that any method used for measuring flammable refrigerant explosion limits has its conditional restrictions. Flammable refrigerants in the atmosphere can also explode under certain conditions, when the concentration is approaching the explosion limits. An experimental study on the explosion limits of six kinds of flammable refrigerants is carried out with a mixture of refrigerant and combustible refrigerant, which has a similar effect to a flame retardant. An experimental apparatus was designed to test the explosion limits of mixtures made from three different nonflammable refrigerants and six different flammable refrigerants. Two practical models were developed to estimate the critical concentration for inhibiting explosion of refrigerant mixtures: one was made up of two flammable components with one nonflammable component, and the second was made up of one flammable component with two nonflammable components.

Design and Availability Research of a Flammable and Explosive Volatiles Monitoring and Early Warning System (FEVMEW) for the Bus Crowded Places

In order to reduce the arson or accidental fire losses, we developed a gas sensitive detector used for the rapid detection and early warning of flammables in crowded places such as buses. A MEMS (Micro-Electro-Mechanical System) based thin film semiconductor was fabricated as the gas sensor. To obtain the target gas selective response, the surface of the sensitive film was modified with highly active metal catalytic nano-particles. Thus the anti-interference ability was improved and the false alarm rate was effectively reduced. Furthermore, the modular embedded system for information acquisition and transmission was developed. Supported by the Airflow Precision control system (APs), the rapid warning of volatile gas of flammable substances was realized. Experiments showed that RAs has satisfied selectivity to volatiles of usual flammable liquid, such as the output voltage reaches 3 V (0 - 3.3 V). With simulation about the actual installation state in bus, MWs sounds an alarm at 2 minutes after splashing 50 mL 92# petrol to the floor. For the last two years, FEVMEW has been integrated into more than 4000 buses in Hefei. This design has been proved feasible according to the actual operation.

Research on Application of ZigBee Technology in Flammable and Explosive Environment

Wireless Sensor Network based on ZigBee technology is a wireless network which is composed of many nodes of ZigBee RF chips, sensors and MCUs, especially suitable for application of the remote monitoring system in flammable and explosive environments. This paper presents the characteristics and advantages of ZigBee technology, also discusses the system for hardware and software design. This system effectively fulfills the remote monitoring in flammable and explosive environments and posses high practical values.

A novel explosion-proof walking system: Twin dual-motor drive tracked units for coal mine rescue robots

A new explosion-proof walking system was designed for the coal mine rescue robot(CMRR) by optimizing the mechanical structure and control algorithm. The mechanical structure innovation lies mainly in the dual-motor drive tracked unit used, which showed high dynamic performance compared with the conventional tracked unit. The control algorithm, developed based on decision trees and neural networking, facilitates autonomous switching between "Velocity-driven Mode" and "Torquedriven Mode". To verify the feasibility and effectiveness of the control strategy, we built a self-designed test platform and used it to debug the control program; we then made a robot prototype and conducted further experiments on single-step, ramp, and rubble terrains. The results show that the proposed walking system has excellent dynamic performance and the control strategy is very efficient, suggesting that a robot with this type of explosion-proof walking system can be successfully applied in Chinese coal mines.

A STUDY ON HEAT PIPE RADIATOR USED FOR THE COOLING OF THE HIGH-POWER THYRISTOR IN EXPLOSION-PROOF SHELL

The cooling of the high-power thyristor (HPT) in explosion-proof sbcll (EPS) used inmining pit has been a difficult problem for a long time. It has some spectal demands. According toheat pipe’s working principle, this paper introduced a kind of newly devcloped beat pipe radiatorSeveral HPT in EPS can be cooled by one beat pipe. In order to obtain the cooling and forced convection cooling , two dimensionless equations were obtained. This paper also studicd the refation between the surface temperature of HPT and the working electric current. The corresponding curvewas given out. Experiments shown that the beat pipe radistor introdued in this paper could effectively cool the HPT in EPS. It becomes a practical and valuable new technique.

Application of Dual Throttling Air-Conditioning System to Explosion-Proof Frequency Converter

An explosion-proof dual throttling air-conditioning system was put forward to solve the heat dissipation and internal dewing problems of explosion-proof frequency converter in the underground coal mine. This study investigated the feasibility and benefits of explosion-proof dual throttling cooling and dehumidification air-conditioning system applied to the explosion-proof frequency converter. The physical model of dual throttling air-conditioning system was established and its performance parameter was described by mathematical method. The design calculation of the system has also been done. The experimental result showed that the system reached the steady state at the refrigeration mode after running 45 min, and the maximum internal temperature of the flame-proof cavity was 31.0 ℃. The system reached the steady state at the dehumidification mode after running 37 min. The maximum internal relative humidity and temperature of the flame-proof cavity were 33.4% and 36.3 ℃, respectively. Therefore, the proposed system had excellent ability of heat dissipation and avoided internal dewing. Compared with water cooling system, it was more energy-saving and economical. The airflow field of dual throttling air-conditioning system was also studied by CFD simulation. It was found that the result of CFD numerical simulation was highly consistent with the experimental data.

矿井无线电波防爆安全发射功率研究

5G,5.5G,WiFi6,WiFi7,UWB,ZigBee等矿井移动通信系统及人员和车辆定位系统等发射的大功率无线电波有点燃瓦斯和煤尘的风险。因此,需要合理设置防爆无线电设备发射的无线电波防爆安全功率阈值,限制防爆无线电设备发射的无线电波功率。欧洲标准CLC/TR 50427:2004《Assessment of inadvertent ignition of flammable atmospheres by radio-frequency radiation-Guide》规定了爆炸性气体环境中无线电波防爆安全接收点火功率阈值,但缺少无线电波防爆安全发射功率阈值的内容。国家标准GB/T 3836.1—2021《爆炸性环境第1部分:设备通用要求》和国际标准IEC 60079-0:2017《Explosive atmospheres-Part 0:Equipment-General requirements》虽然有无线电波防爆安全发射功率阈值的相关规定,但错误地将欧洲标准CLC/TR 50427:2004中的无线电波防爆安全接收点火功率阈值修改为无线电波防爆安全发射功率阈值,大大降低了爆炸性环境中无线电设备所能允许的最大发射功率。由于煤矿井下没有能作为接收天线的起重机这类细长结构物体,且现有矿井无线通信及定位系统工作频率均远大于30 MHz,所以,无线电波防爆安全接收点火功率阈值应为8 W,而不是国家标准GB/T 3836.1—2021和国际标准IEC 60079-0:2017规定的无线电波防爆安全发射功率阈值6 W。在发射天线发射的无线电波能量全部被等效天线吸收的最不利于无线电防爆的传输和耦合情况下,无线电设备工作频率为等效天线谐振频率时,接收点火功率达到最大,为等效天线接收的总功率的一半,即发射功率的一半。在实际工程中,无线传输效率和耦合效率均不会为1,因此,无线电波防爆安全发射功率阈值应是无线电波防爆安全接收点火功率阈值2倍以上。煤矿井下无线电波防爆安全接收点火功率阈值为8 W,因此,煤矿井下无线电波防爆安全发射功率阈值应大于16 W。

基于CESE方法的煤矿风井泄爆全过程模拟与消波增效研究

为揭示煤矿风井泄爆过程、探寻增强泄爆效果方法,针对现行泄爆方法和多种改进泄爆方法,建立了系列全尺寸三维仿真模型,利用LS−DYNA软件的CESE求解器,进行了全过程流固耦合模拟分析。结果表明:现行防爆门在泄爆过程中会引发较强烈的反射冲击波且不能快速有效地予以消弱,致使风硐中先后出现可对风机造成二次冲击的2道冲击波;去除防爆门立壁结构对提升泄爆效果作用不明显,但可使防爆门受到的冲击明显减弱;在一定范围内,减轻防爆门质量对提高泄爆效果的作用较为有限,且会使防爆门吸收的爆炸能量明显增加;在增量不大的情况下,增大防爆门到风井和风硐交岔点的距离即能有效改善泄爆效果;侧向和正向先行泄爆方法均能明显增强泄爆效果,并对防爆门有显著的减冲和保护作用,在算例条件下,最优可使反射波超压峰值下降49.4%和28.3%;防爆门开启时间、泄爆面积和防爆门到风井/风硐交岔点的距离是影响泄爆效果的重要因素;风井达到良好泄爆效果所需要的开启时间比现行防爆门要短得多;仅在井口设置防爆门存在不能消减风硐中第1道冲击波超压峰值的局限性。基于对风井泄爆过程、机理和方法的新认识,提出了以“两区域多通道”泄爆为特征的主辅防爆门协同泄爆方法,以系统提升风井泄爆效果和防爆水平。

隔爆型电磁铁力-行程特性的优化分析及验证

防爆阀是石油勘探等井下液压设备常用的核心控制元件。现有防爆阀常采用的隔爆型电磁铁体积相对较大,难以充分发挥液压元件及系统功重比大的优势。基于防爆阀可靠性的要求,在不增大矿用防爆阀外形尺寸的前提下,分别研究了衔铁高径比、隔磁环位置、上端隔磁角对隔爆型电磁铁力-行程特性的影响。基于L_(9)(3^(4))正交试验,采用极差分析法获得了试验因素影响程度大小以及选择范围内最佳的结构参数组合。结果表明:当隔爆型电磁铁结构参数衔铁高径比为2.03,隔磁环位置距参考点位置下移0.5 mm,上端隔磁角30°时电磁力-行程特性曲线最佳,为隔爆型电磁铁的结构参数优化提供了指导,并通过对比试验验证了隔爆型电磁铁结构设计的合理性和可行性。

无线电波发射功率防爆要求与检测方法

现行国家标准GB/T 3836.1—2021《爆炸性环境第1部分:设备通用要求》和国际标准IEC 60079-0:2017《Explosive atmospheres-Part 0:Equipment-General requirements》规定无线电发射器的阈功率为无线电发射器的有效输出功率与天线增益的乘积。在无线电波防爆安全发射功率阈值一定的条件下,天线增益越大,无线电发射器的有效输出功率就越小,这将限制通过增大天线增益,提高无线传输距离。因此,有必要对国家标准GB/T 3836.1—2021和国际标准IEC 60079-0:2017中规定的阈功率的正确性进行研究,提出合理的无线电波发射功率防爆要求与检测方法。提出了无线电波防爆安全发射功率与天线增益无关,国家标准GB/T 3836.1—2021和国际标准IEC 60079-0:2017规定的无线电发射器的阈功率是错误的。提出了煤矿井下无线电波防爆安全发射功率阈值应大于16 W,且与天线增益无关;国家标准GB/T 3836.1—2021和国际标准IEC 60079-0:2017规定阈功率不得大于6 W,且与天线增益相关,是错误的。提出了无线电波防爆安全性能检测方法——检测无线电发射器输出功率,这既可保证通过检测的防爆无线电设备的防爆安全,又简化了检测方法,更提高了防爆无线电设备的无线电波发射功率,解除了对天线增益的限制,将大大提高煤矿井下防爆无线电设备的无线传输距离。

防爆柴油机排气颗粒物的微观结构研究

为研究废气水洗箱和含氧燃料对防爆柴油机排气颗粒物微观结构随工况变化的影响,利用扫描电子显微镜(Scananing Elecron Microscope,SEM)对0#柴油(D100)和丁醇/柴油混合燃料(BD20)的排气颗粒物的微观形貌、分形特征和粒径分布进行研究。其中,丁醇的质量分数为20%。结果显示:经过废气水洗箱后,颗粒物内吸附质含量增多,密集程度升高,在多数工况下,颗粒物支链减少,且BD20有利于减少颗粒物碳烟粒子含量;颗粒物的计盒维数分布在1.70~1.85,且经过废气水洗箱的颗粒物结构更紧密,计盒维数更大,D100的计盒维数大于BD20的计盒维数;颗粒物基础碳粒子粒径分布在10~90 nm,废气水洗箱对颗粒物有沉降作用,使颗粒物平均粒径减小,BD20的平均粒径小于D100平均粒径。

防爆工业车辆的防爆检测要求

广泛应用于爆炸危险场所的防爆工业车辆在工作过程中的潜在点燃源主要有电气漏电、高温热表面、机械火花、静电等。为提升防爆工业车辆在复杂工况下运行的安全性,本文从我国防爆工业车辆发展现状出发,结合防爆工业车辆存在的潜在点燃源,对防爆工业车辆的防爆安全技术及检测要求提出思考。

智慧矿山系统工程及关键技术研究与实践

针对智慧矿山复杂巨系统建设过程中存在的问题,提出了智慧矿山建设的总体技术架构,并分别从智慧矿山系统模型构建、地下空间重构与模型动态更新、机器视觉测量技术、瓦斯环境射频防爆测试方法、矿山安全闭环管控体系、智慧矿山标准体系等方面进行了详细阐述。将智慧矿山分为信息感知支撑层、边缘计算层、云数据中心、多型网络、矿山智能生产管控平台、矿山智能生产系统、智慧矿山运维管理系统,构建了基于多系统深度融合的智慧矿山技术架构。基于智慧矿山知识图谱及信息抽取技术,构建了以数据创新为驱动、通信网络为基础、数据算力为核心的智慧矿山系统模型。构建了以机器视觉感知信息为主、其他感知信息为辅的矿山井下三维视觉空间模型,提出了矿山井下场景三维视觉与空间重建框架,实现了矿山井下三维空间重构与动态更新。开发了基于机器视觉技术的井下设备位姿与煤岩界面识别算法,实现了对井下综采装备群及煤岩分界面的同时空测量。探讨了井下瓦斯环境下现行防爆标准对5G基站功率的限制及存在的不足,设计开发了射频电磁能防爆专用试验装置,为提升井下5G基站功率阈值提供了方法借鉴。提出了融合灾害信息全面感知、防控方案自主决策、防控装备协同控制的矿井灾害闭环管控系统技术架构,实现井下灾害的超前预测预警与协同防控。构建了智能化煤矿标准体系框架,剖析了我国煤矿与金属矿山智能化建设典型案例,提出了智慧矿山建设发展趋势及建议。

串联战斗部级间隔爆结构的研究现状和发展趋势

串联战斗部作为反爆炸反应装甲的一个重要手段,已成为国内外兵器研究的热点。串联战斗部工作时,前级装药爆炸势必对后级装药产生影响。为削弱前级装药爆炸产生的爆轰波与碎片对后级装药的影响,需要在前后级装药之间设置隔爆结构。良好的隔爆结构对串联战斗部前后级稳定工作,提升战斗部性能有重要意义。综述了近年来串联战斗部级间隔爆体的研究进展,包括结构布局、材料选型与优化设计方法等方面,并结合目前隔爆体发展状况对隔爆体未来发展趋势进行展望,以期对串联战斗部隔爆体的设计和改进有所启示。

多组分天然气掺氢爆炸下限实验及模型研究

为评估掺氢天然气的燃爆风险,搭建天然气掺氢燃爆参数测试平台,通过开展不同初始压力及点火能量条件下天然气/氢气混合物的点火实验,研究多组分天然气爆炸下限的变化规律,建立混合物爆炸下限的预测模型。研究结果表明:初始压力由0.03 MPa增至0.1 MPa,体积分数4%的天然气起爆时所需最低掺氢量降低29.4%;点火能量由1 J增至50 J,体积分数4%的天然气起爆时所需最低掺氢量降低37.5%,本文提出的理论模型预测结果与实验数据相对误差低于16%。研究结果可为掺氢天然气的安全输送提供一定的科学参考。

矿用防爆柴油机四元组合式尾气后处理系统设计及性能试验

防爆柴油机是矿井辅助运输车辆使用最为广泛的动力源之一,受防爆改造以及井下恶劣环境的影响,导致其尾气污染问题严重,有悖于绿色矿山发展战略。煤矿井下自2020年12月开始实施非道路国III排放标准,但现阶段矿用防爆柴油机尾气净化多采用机内前处理技术,无法满足非道路国IV及更高标准的排放要求。针对防爆柴油机尾气污染严重及净化技术滞后的问题,设计了一种新型四元组合式尾气后处理系统,并通过仿真和台架试验开展了关键部件结构参数优化及尾气污染物净化性能研究。首先,按照煤矿井下防爆要求,超前面向非道路国IV尾气排放标准,设计了一种由氧化催化剂(DOC)、颗粒捕集器(DPF)、选择性催化还原器(SCR)和防爆温控装置(EPTC)组成的防爆柴油机四元组合式尾气后处理系统;采用STAR-CCM+仿真软件对防爆温控装置结构进行传热分析,结果表明:管壁面温度均小于150℃,可满足煤矿安全规程防爆要求。其次,以某型60 kW防爆柴油机为研究对象,基于GT-Power软件分别搭建了DOC、SCR和DPF后处理部件的仿真模型,并对其关键结构参数及净化性能开展正交试验进行优化,确定了尾气后处理系统关键部件的最优结构参数,得到如下规律:污染物的净化效率随DOC和SCR的载体直径、载体长度和通道密度的增大而提高;载体长度和载体直径对DPF捕集效率与DOC和SCR规律一致,而DPF因其特殊的壁流式载体结构,随着通道密度增加,PM颗粒物的捕集效率可始终维持在96%附近。在此基础上,建立了防爆柴油机和后处理系统的耦合模型,开展了防爆柴油机尾气排放污染物净化效率、动力性与经济性仿真试验。最后,研制了四元组合式尾气后处理系统样机并开展台架试验,将试验数据与仿真数据对比分析,结果表明:尾气后处理系统对CO、NO、HC与颗粒物的净化效率分别大于95%、90%、83%以及95%,可满足非道路国IV排放要求;加装尾气后处理系统的防爆柴油机整体输出扭矩平均下降4.83%,整体燃油消耗率平均增加1.19%,对防爆柴油机的动力性与经济性的实际影响较小。

国产化5G防爆手持终端研发及其在石化企业的应用

随着5G技术在工业领域应用的快速发展,在炼化企业巡检、人员定位、融合通信等业务领域,为了提高现场便捷应用的效率和质量,降低操作人员的劳动强度,研发5G国产化、轻量化、多功能的一体化防爆手持终端成为迫切需要。文章旨在探讨国产化5G防爆手持终端的技术创新思路及应用场景,以助推石化企业的数字化转型,促进传统生产向智慧生产转型升级。

压接型IGBT器件短路失效管壳爆炸特性及防护方法

压接型绝缘栅双极性晶体管(insulated gate bipolar transistor,IGBT)作为现有柔性直流输电设备的核心部件,在实际应用中,由于承受高电压、大电流的工作环境,容易发生短路过流失效,进而造成的结构爆炸现象。为研究这一爆炸现象的破坏效应及其防护,该文结合多组模拟模块化多电平工况实验,得到IGBT器件短路过流失效爆炸后外壳结构的变形特征。结合电气能量特性的分析和实际爆炸失效形貌特点,建立该IGBT器件结构的数值仿真模型,初步确定实际爆炸过程中的等效TNT爆炸当量。在此基础上,从提高结构自身抗爆能力、增加能量外泄通道、替换结构材料等角度开展IGBT器件的结构优化设计,并进行相关试验验证。结果表明,将管壳的陶瓷材料替换为纤维增强复合材料可有效提高结构的防爆性能,降低器件的破坏程度。

基于蒙特卡罗法的高校易燃易爆实验室不安全因素风险评估

为了减少高校实验室火灾爆炸事故,参考“2-4”模型理论,以实验开展流程对2001年来发生的46起火灾爆炸事故进行分析,基于蒙特卡罗法构建了不安全因素风险评估模型。对实验前准备、实验操作过程、实验后整理、实验材料、仪器设备5个环节的不安全因素风险后果值进行累计概率分布,通过敏感度分析得出各不安全因素对风险值的影响。结果表明,实验材料、实验操作过程2个环节的风险值最高;“未熟知实验危险有害因素”“废弃物处理不当”“实验试剂材料违规购买、存放或使用”“危险实验未防护”及“试剂材料选取方式不符合规定或更改设备操作顺序”5个不安全因素的敏感度值大于30%,对风险值的影响较大。在此基础上对各环节及重点不安全因素的提出事故预防措施。