基于氢气充放试验及数值模拟的储氢气瓶安全评价

储氢气瓶是新能源汽车的重要储能设备,其可靠性直接关系到汽车的安全性。研究了不同环境温度下,35 MPa铝合金内胆车用储氢III型气瓶在充放气时的最终温度和应力分布情况,并对其安全性进行了评价。借助试验测试平台,在不同温度下进行了实际充放试验。试验过程中无漏气现象,且最终温度符合要求,表明储氢气瓶在试验条件下是安全的。由此,在获得了储氢气瓶充放时热响应规律的基础上,对不同温度下的氢气充放过程进行了数值模拟,得到其应力分布情况。结果表明,储氢气瓶复合层的应力远小于其材料抗拉强度,即内胆和复合层的强度均可视为满足要求。研究结果可为储氢气瓶的试验开展、安全评价、寿命预测提供依据。     

A new laboratory rig for evaluating helmets subject to oblique impacts

Current requirements and regulations governing motorcycle helmets around the world are based on test results of purely radial impacts, which are statistically rare in real accidents. This study presents a new impact rig for subjecting test helmets to oblique impacts, which therefore is able to test impacts of increased statistical relevance to real motorcycle accidents. A number of different head-helmet interfaces have been investigated. A test rig was constructed to produce oblique impacts to helmets simulating those occurring in real motorcycle accidents. A Hybrid III dummy head was fitted with accelerometers to measure the accelerations arising during impact testing. The equipment used for data collection was validated in both translational and rotational acceleration. In order to better resemble the human head, an artificial scalp was fitted to the hybrid dummy. The same test rig was used to investigate the performance of a number of different helmets. Impact velocities ranging from 7.3 to 9.9 m/s were tested using a number of different impact angles and impact areas. This study shows that the new test rig can be used to provide useful data at speeds of up to 50 km/h and with impact angles varying from purely tangential to purely radial. The rotational accelerations observed differ greatly depending on both helmet and scalp designs. For example, a helmet with a sliding outer shell placed on an experimental head fitted with an artificial scalp (made to resemble the human scalp) reduces rotational accelerations of the head by up to 56%, compared with those of an experimental head fitted with a fixed scalp and conventional helmet. The degree of slippage between the skull and the scalp, and between the scalp and the helmet, leads to considerable variation in the results. This innovative test rig appears to provide an accurate method for measuring accelerations in an oblique impact to a helmet. In order to obtain a good level of repeatability in oblique impact testing, it is crucial that the helmet be fixed to the head in the exact same way in each individual test. Both the position and the angle of impact must be reproduced identically in each test. The test rig used here has shown that this type of rig can be used to compare different helmet designs, and it therefore is able to contribute to achieving safer helmets.     

Comparative study on standardized ignition sources used for explosion testing

For the determination of safety characteristics of gases, vapors and dusts different types of ignition sources are used in international standards and guidelines. The paper presents test results of a comparative calorimetric and visual study between four different types of ignition sources. The ignition procedures were analyzed visually with a high-speed camera and electric recordings. In addition to that, the influence of the electrode-orientation, -distance as well as ignition energy on the reproducibility of the exploding wire igniter was tested.The exploding wire is already in use for standardized determination of safety characteristics of gases, first tests on the suitability of the exploding wire igniter for dust testing have been carried out but are not standardized yet. Using the exploding wire, the ignition energy can be varied from 2 J to 10 000 J (2 x 5000 J) and thus it could be used for gases, vapors, dusts and hybrid mixtures. Moreover it can be used at high initial pressures and it is the only ignition source with an easily measurable ignition energy release. Furthermore, it does not introduce another chemical reaction into the system.Finally, a proposal for a standard ignition source for explosion tests on hybrid mixtures is derived from the test results.     

Recent development of standardization of testing methods for dust explosion in Japan

The Dust Explosion Committee of the Association of Powder Process Industry and Engineering (APPIE) of Japan has acted to establish the standard for the member of the Association. Two testing methods have been authorized by the Association. The methods are established to evaluate sensitivity and severity for dust explosion.The ignition sensitivity is evaluated by the minimum explosive dust cloud concentration. Tapping sieve equipment and a strictly-specified Hartmann-type explosion tube have been selected as the testing apparatus. The tapping sieve equipment is applied to measure the minimum explosive concentration by forming a dust cloud supplied from a sieve on the top of the explosion chamber. The Hartmann-type tube is used to investigate roughly whether the test powder is explosive or not. A lot of explosion tests had been carried out to standardize the equipment and evaluate the sensitivity. This APPIE standard is being revised.Along with the ISO standard for explosion severity, Research Institute of Industrial Safety, the Ministry of Labour published a Guide to Test Method for Explosion Pressure and Rate of Pressure Rise for Combustible Dusts in 1994. Based on this Guide, The APPIE Committee has made the draft for the member.These standards and drafts are aimed to be the Japanese Industrial Standard (JIS). No other similar standard exists in Japan. In the present paper, technical data and explosion statistics which are the background of the APPIE standard for the ignition sensitivity are to be described.     

Testing of dust clouds for the electrostatic-spark ignition hazard in industry. Need for a modified approach?

Current standard test methods for electric-spark minimum ignition energies (MIEs) of dust clouds in air require that a series inductance of at least 1–2 mH be included in the electric-spark discharge circuit. The reason is to prolong the spark discharge duration and thus minimize the spark energy required for ignition. However, when assessing the minimum electrostatic energy ½CU² for dust cloud ignition by accidental electrostatic-spark discharges, current testing standards require that the series inductance of at least 1–2 mH be removed from the spark discharge circuit. No other changes of apparatus and test procedure are required. The present paper questions whether this simple approach is always adequate. The reason is that in practice in industry accidental electrostatic-spark discharge circuits may contain large ohmic resistances due to corrosion, poor electrical grounding connections, poorly electrically conducting construction materials etc. The result is increased spark discharge durations and reduced mechanical disturbance of the dust cloud by the blast wave emitted by the spark. Therefore, testing for minimum ½CU² for ignition by accidental electrostatic spark discharges may not only require removal of the series inductance of 1–2 mH from the standard MIE spark discharge circuit. Additional tests may be needed with one or more quite large series resistances R_s inserted into the spark discharge circuit. The present paper proposes a modified standard test procedure for measurement of the minimum electrostatic-spark ignition energy of dust clouds that accounts for these effects.     

点火位置对独头巷道中瓦斯爆炸超压的影响

运用AutoReaGas爆炸仿真模拟器研究了独头巷道中点火位置对瓦斯爆炸后果的影响。结果表明,在本计算条件下,爆炸静态超压随着距离的增加而减小,爆炸动压随着距离的增大而增大,点火位置对爆炸后果有重要影响,点火位置离封闭端越近,各个测点上所得到的超压越大。     

Electrostatic spark ignition of sensitive dust clouds of MIE<1 mJ

Accidental electrostatic sparks in industrial plant producing/handling powders/dusts occur whenever a non-earthed electrically conducting object has been charged tribo-electrically to a high voltage and suddenly discharges its energy to earth via an air gap of appropriate length. When assessing the electrostatic spark ignition hazard in an industrial plant, the parameters of prime concern are the capacitances C of electrically conducting plant items that may become charged tribo-electrically, the voltages U to which they may become charged, and the minimum electric spark ignition energies (MIE) of the dust clouds of concern. Whenever , there is a possibility of accidental electrostatic spark ignition.

Current standard apparatuses for determining MIE of dust clouds have a lower spark energy limit of 2–3 mJ. In an investigation by the present authors, discussed in detail elsewhere, a new spark generator capable of producing synchronized capacitive sparks of energies down to the order of 0.01 mJ was developed and used for testing a selection of ignition-sensitive powders for MIE. Several of the MIEs found were 1–2 orders of magnitude lower than the lower energy limit of current standard test apparatus. Other experiments by the present authors, also reported elsewhere, have shown that quite low MIEs can be found for some dusts even with a less optimal synchronization mechanism, which may occur accidentally in practice.

The main object of the present paper is to discuss possible practical concerns arising from the finding that clouds in air of some dusts can have very low MIEs. In such cases, one may have to pay attention to even minor C values, i.e. minor plant items. Alternatively, with larger C values, even quite low voltages may give rise to hazardous spark discharges.

However, some types of fine metal powders of low MIEs will quite readily form electrically conductive layers on the solid surfaces with which they make contact. Hence, electrostatic spark ignition inside process equipment containing such dusts may be less probable than in the case of process equipment containing non-conducting dusts of correspondingly low MIEs.

There may be a need for a new standard test method for determination of MIEs of dust clouds in the <1 mJ range.     

含氧氢气钢瓶释放过程危险性分析及处置

针对一起空气误充入氢气钢瓶而导致使用时发生多起爆炸的事故,详细分析了氢氧混合气钢瓶在释放过程中的主要危险性,对释放过程中最可能存在的点火源即静电的产生机理及静电的放电条件进行了详细的论述,应用TNT当量法对可能发生的氢气钢瓶爆炸事故的破坏强度进行了估算。针对爆炸事故的高危险性,制定了以电机作为开阀动力的远距离放空方案,并提出了接地、洒水增湿等预防静电产生的有效措施,综合考虑冲击波超压伤害和人员操作的方便,确定了合理的安全操作距离,为防止爆炸产生的碎片对周围人员、建筑的伤害,在释放场所周围及人员操作场所设置了沙包墙作为防爆掩体。     

Flammability limit measurements for dusts in 20-L and 1-m3 vessels

Two types of flammability limits have been measured for various dusts in the Fike 1-m³ (1000-L) chamber and in the Pittsburgh Research Laboratory (PRL) 20-L chamber. The first limit is the minimum explosible concentration (MEC), which was measured at several ignition energies. In addition to the three dusts studied previously (bituminous coal, anthracite coal, and gilsonite), this work continues the effort by adding three additional dusts: RoRo93, lycopodium, and iron powder. These materials were chosen to extend the testing to non-coal materials as well as to a metallic dust. The new MEC data corroborate the previous observations that very strong ignitors can overdrive the ignition in the smaller 20-L chamber. Recommendations are given in regard to appropriate ignition energies to be used in the two chambers. The study also considered the other limiting component, oxygen. Limiting oxygen concentration (LOC) testing was performed in the same 20-L and 1-m³ vessels for gilsonite, bituminous coal, RoRo93, and aluminum dusts. The objective was to establish the protocol for testing at different volumes. A limited investigation was made into overdriving in the 20-L vessel. The LOC results tended to show slightly lower results for the smaller test volume. The results indicated that overdriving could occur and that ignition energies of 2.5 kJ in the 20-L vessel would yield comparable results to those in the 1-m³ vessel using 10.0 kJ. The studies also illustrate the importance of dust concentration on LOC determinations.     

Metal hydride fires and fire suppression agents

Most metal hydrides are pyrophoric and water-reactive. Summaries of metal hydride fire incidents are presented to illustrate ignition scenarios, threats to personnel and equipment, and fire suppression experiences. Met-L-X™, a sodium chloride-based, certified, Class D fire suppression agent, has successfully extinguished some metal hydride fires by coating the hydride and excluding air access. However, the still hot hydride is prone to re-ignition upon surface disturbance, such as may be necessary during disposal. Previously reported testing of various Class D agents and moist sand for sodium hydride fires is reviewed here along with certification and ad hoc testing of existing Class D agents and recent testing of a new candidate Class D agent. Hydride explosibility testing is also briefly summarized. Additional fire and explosibility tests, as well as suppression agent reactivity evaluations, are recommended.     

基于改进LEC法的危化企业静电点燃危险评价

危化企业爆炸性危险环境下由静电放电引发的火灾爆炸时有发生,针对这一问题分析了危化企业气体、液体、固体、粉体及人体在不同生产工艺过程中静电电荷来源以及可能的静电放电形式。综合考虑静电点燃源形成可能性、爆炸性环境形成可能性、监控与控制措施有效性以及静电事故后果严重度,构建了基于改进LEC法的静电点燃危险评价方法,该评价方法能实现对危化企业静电点燃源危害的量化评估与分级。应用该方法对某加油站进行静电点燃危险评价,并根据评价结果提出了预防改进措施。     

Ignition tests for electrical and mechanical equipment subjected to hot surfaces

This paper reports some experimental work on hot surface ignition temperatures of dust deposits. Dust layers up to 75 mm in depth were ignited using a modified version of the standard 5 mm layer apparatus. The measured ignition temperatures show good agreement with predictions using the method given in EN 50281-2-1. Ignition temperatures of conical dust deposits over an electrically heated box were not predictable, but were not too dissimilar from the ignition temperatures of the thick layers. Both tests gave adequate reproducibility in round robin tests. Rotating steel wheels in contact, immersed in a dust deposit produce the frictional hot surfaces. A relation between the power lost by friction and the surface temperature developed has been derived. The surface temperatures leading to ignition were close to the ignition temperatures for the conical deposits on the heated box. The similarities between the ignition temperatures of dust deposits in several configurations indicate that a simple test for ignition temperature measurement could have wide application in dusty environments.     

A sneak peek into the phenomenology of fuel mist explosions: The key role of vapor fractions

The modern world depends greatly on hydrocarbons, which are ubiquitous, indispensable fuels used in nearly every existing industry. Although important, their use may trigger dangerous incidents, whether in their production, handling, storage, or transporting phase, especially when aerosolized. In light of proposing a standard procedure to assess the flammability and explosivity of fuel mists, a new test method was established based on the EN 14034 standards series. For the previous purposes, a gravity-fed mist generation system was designed and employed in a modified 20 L explosion vessel. This test method allowed the determination of the ignition sensitivity of several fuels. In addition, their explosion severity was represented by the explosion overpressure P_ex, and the rate of pressure rise dP/dt_ex, two thermo-kinetic parameters determined with a specifically developed control system and custom software. Nonetheless, a noticeable difference in the ignition sensitivity and the explosion severity was perceived when changing suppliers or petroleum cuts of some fuels. Moreover, sensitivity studies showed that both the droplet size distribution and the temperature of the droplets play a significant role in fuel mist explosion. These parameters can be directly related to the vapor fraction surrounding a droplet during its ignition. Consequently, this study focuses on the influence of varying the composition of three well-known and abundantly used fuels. Different petroleum cuts were introduced in different fractions into isooctane, Jet A1 aviation fuel, and diesel fuel mixtures, which were then aerosolized into a uniformly distributed turbulent mist cloud and ignited using spark ignitors of 100 J. Subsequently, complementary tests were executed in a vertical flame propagation tube coupled with a high-speed video camera allowing the visualization of the flame and the determination of the spatial flame velocity, and a tentative estimation of the laminar burning velocity. The latter was also estimated from the pressure-time evolution in the 20 L sphere using existing correlations. Indeed, the determination of the laminar burning velocity can be useful in modeling such accidents. Finally, highlighting the essential role of the mist and vapor fraction during their ignition has led to a better understanding of their explosion mechanisms.     

航空活塞发动机点火强度均衡性测试及防火研究

针对磁电机故障和点火电嘴故障会使发动机失去动力引起飞行事故,高压导线破损放电可能导致动力系统起火并引发飞机火灾等安全隐患,利用紫外探测技术和虚拟仪器技术设计了航空活塞发动机点火强度均衡性测试系统,利用该测试系统完成航空活塞发动机点火系统的安全隐患检测。以四缸活塞发动机正常点火、高压导线破损、点火电嘴积碳等三种点火系统作为测试对象,测试发动机在不同转速下各气缸点火电火花紫外辐射强度,用以表征点火能量强度。实测得到,在不同转速下点火电嘴积碳故障都会导致点火强度降低;高压导线破损漏电会同时导致点火能量损失与点火强度不均衡,并且与转速呈正相关。测试结果可为航空活塞发动机点火系统故障排除及发现可能存在的高压导线破损放电电气火灾隐患点提供技术依据。     

Towards an alternative criterion for the shipping safety of activated carbons: Part 4. The role of times to ignition

To the previously developed and implemented new criterion for the shipping safety of activated carbons is added a consideration of ignition times. It is shown that there is considerable support for the view that in the past shipments of such materials deemed on the basis of the IMCO/ISO test procedures to be subcritical have actually been supercritical, but that the long ignition times, exceeding voyage times, have prevented fire from developing.     

Assessing the influence of real releases on explosions: Selected results from large-scale experiments

The research activities in the project Assessing the Influence of Real Releases on Explosions (AIRRE) included a unique series of large-scale explosion experiments with high-momentum jet releases directed into congested geometries with subsequent ignition. The primary objective for the AIRRE project was to gain improved understanding of the effect that realistic releases and turbulent flow conditions have on the consequences of accidental gas explosions in the petroleum industry. A secondary objective was to develop a methodology that can facilitate safe and optimal design of process facilities. This paper presents selected results from experiments involving ignition of a highly turbulent gas cloud, generated by a large-scale, pressurised release of natural gas. The paper gives an overview of the effect on maximum explosion overpressures of varying the ignition position relative to the release point of the jet and a congested region placed inside the flammable cloud, with either a high or a medium level of congestion. For two of the tests, involving a jet release and the medium congestion rig, the maximum overpressures significantly exceeded those obtained in a quiescent reference test. The paper presents detailed results for selected tests and discusses the effect of the initial flow field generated by realistic releases – including turbulence, net flow and concentration gradients – on relevant explosion phenomena.     

安全带整体静负荷试验机的研制及应用

安全带是有效地预防高处作业人员因意外坠落而受到身体伤害的必要防护装备。本文根据GB6095—2009《安全带》、GB／T6096—2009《安全带测试方法》标准中安全带整体静态负荷试验的要求,对安全带整体静负荷试验机的研制与应用开展一些调研和探讨,希望对从事安全带检验的机构和安全带生产的企业中的科研、检验人员提供一些感性的认知和帮助。     

在役石油钻机安全检测检验体系的建立

针对我国在役石油钻机安全检测的现状,分析了现有国内外检测标准存在的主要问题。从安全生产检测检验工作的实际需要出发,构建了在役石油钻机安全检测体系,确定了检验对象,给出_『检验依据、检验周期和准则,并制定出厂相应的检验细则。     

玻璃隔墙冷却专用喷头的设计及其应用效果研究

用水喷淋冷却是提高玻璃隔墙耐火极限的有效途径。首先确定了玻璃隔墙冷却专用喷头的设计目标,基于溅水盘的布水原理,通过溅水盘底部和背部的形状设计,确定了新型喷头的整体结构。然后搭建冷态试验平台进行布水规律试验。以钢化玻璃为冷却对象,在水压为0.05 MPa(表压)下,观察喷头距玻璃隔墙水平距离分别为0.1 m、0.3 m和0.5 m时,喷头在玻璃隔墙表面的布水现象,记录喷水密集和稀疏的区域,从喷洒半径、不同布水区域覆盖面积、水的利用率及水膜厚度等方面分析了布水规律,并与常用工程喷头的布水效果进行了比较。最后进行点火试验,在玻璃表面布置贴片热电偶,以汽油作为燃料,预燃60 s后,启动喷淋系统,分别测定了喷淋启动前后玻璃表面的温度,并选取玻璃迎火面布水密集区的一点计算冷却速率。结果表明:新型喷头的布水效果较好,与直立边墙型喷头相比,水量密集区域的覆盖面积增大了13.9%~19.5%,基本实现了玻璃隔墙表面的全覆盖;喷头冷却速率为1.1,冷却效果较好。     

某山坡露天矿边坡稳定性的FLAC3D研究

某山坡露天矿,原设计的最终边坡角约为46°。为了探索最终边坡角的合理性,应用快速拉格朗日有限差分法FLAC3D在摩尔-库伦准则下搜索该岩质山坡露天边坡的潜在受拉区,判定其稳定性。结果表明:经济合理的最终边坡角是50°38';应用8 m长的锚索加固局部台阶可减小其潜在受拉区中的拉应力;并段将减小边坡的稳定性;爆破开挖时的同段最大装药量与爆距对边坡稳定性影响明显。该方法确定最终边坡角技术可行,它适用于研究岩质边坡的稳定性,克服了用极限平衡法研究边坡稳定性必须事先假定滑动面的弱点。