CFD simulation study to investigate the risk from hydrogen vehicles in tunnels
CFD simulation study to investigate the risk from hydrogen vehicles in tunnels
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DOI：
10.1016/j.ijhydene.2009.02.004
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发表时间：
2009-07-01
影响因子：
7.2
通讯作者：
Hansen, Olav R.
中科院分区：
文献类型：
--
作者：
Middha, Prankul;Hansen, Olav R.
在引入氢燃料汽车时，应对风险水平的潜在变化进行评估。人们普遍认为，室外单辆车辆意外释放的氢气会很快消散，不会导致任何重大爆炸危险。对于停车场、车间或隧道等更狭窄的情况，情况可能有所不同。实验和计算机建模对于更好地理解情况都很重要。本文报道了一项模拟研究，旨在检查隧道中氢燃料汽车的爆炸风险（如果有）。其目的是进一步了解有关公路隧道内氢气释放和燃烧的现象，并进一步展示为海上工业开发的风险评估方法如何应用于当前任务。这项工作正在为欧盟第六框架（卓越网络）项目 HySafe 做出贡献，有助于从以前的研究、新实验和其他建模活动中收集的整体理解。对两种不同隧道布局和一系列纵向通风条件下的氢气汽车（包含向上或向下释放的 700 巴气罐或仅向上释放的液氢罐）和公共汽车（包含向上释放的 350 巴气罐）的释放进行了研究。模拟的最大释放量是 50 秒内从一辆公共汽车的四个气缸（通过一个通风口）释放 20 kg H(2)，初始释放速率约为 1000 g/s。还与天然气 (CNG) 燃料车辆进行了比较。该研究表明，对于氢动力车辆，假设全部气体库存按化学计量均匀混合的典型最坏情况风险评估方法可能会导致严重的爆炸载荷。然而，更广泛的研究和更现实的释放场景显着降低了预测的危险。对于某些情况，可燃气体云的尺寸仍然很大，但如果考虑到预测云的实际反应性，则预测最坏情况的爆炸压力适中。作为风险评估方法的最后一步，进行概率 QRA 研究，其中将概率分配给不同的场景，应用时间相关的点火模型，并使用等效的化学计量气体云来转换分散的非均质云的反应性。概率风险评估研究基于使用商用工具 FLACS 进行的 200 多项扩散和爆炸 CFD 计算。风险评估建议研究中使用的压力传感器的最大可能压力水平为 0.1-0.3 barg。由于反射（例如车辆下方），其他地方会出现较高的压力。研究中还发现了其他一些有趣的观察结果。例如，该研究表明，对于氢气释放，纵向隧道通风水平对预测风险仅产生边际影响，因为氢气释放的动量和浮力主导着混合和稀释过程。 (C) 2009 年国际氢能协会。由爱思唯尔有限公司出版。保留所有权利。
When introducing hydrogen-fuelled vehicles, an evaluation of the potential change in risk level should be performed. It is widely accepted that outdoor accidental releases of hydrogen from single vehicles will disperse quickly, and not lead to any significant explosion hazard. The situation may be different for more confined situations such as parking garages, workshops, or tunnels. Experiments and computer modelling are both important for understanding the situation better. This article reports a simulation study to examine what, if any, is the explosion risk associated with hydrogen vehicles in tunnels. Its aim was to further our understanding of the phenomena surrounding hydrogen releases and combustion inside road tunnels, and furthermore to demonstrate how a risk assessment methodology developed for the offshore industry could be applied to the current task. This work is contributing to the EU Sixth Framework (Network of Excellence) project HySafe, aiding the overall understanding that is also being collected from previous studies, new experiments and other modelling activities.Releases from hydrogen cars (containing 700 bar gas tanks releasing either upwards or downwards or liquid hydrogen tanks releasing only upwards) and buses (containing 350 bar gas tanks releasing upwards) for two different tunnel layouts and a range of longitudinal ventilation conditions have been studied. The largest release modelled was 20 kg H(2) from four cylinders in a bus (via one vent) in 50 s, with an initial release rate around 1000 g/s. Comparisons with natural gas (CNG) fuelled vehicles have also been performed.The study suggests that for hydrogen vehicles a typical worst-case risk assessment approach assuming the full gas inventory being mixed homogeneously at stoichiometry could lead to severe explosion loads. However, a more extensive study with more realistic release scenarios reduced the predicted hazard significantly. The flammable gas cloud sizes were still large for some of the scenarios, but if the actual reactivity of the predicted clouds is taken into account, moderate worst-case explosion pressures are predicted. As a final step of the risk assessment approach, a probabilistic QRA study is performed in which probabilities are assigned to different scenarios, time dependent ignition modelling is applied, and equivalent stoichiometric gas clouds are used to translate reactivity of dispersed non-homogeneous clouds. The probabilistic risk assessment study is based on over 200 dispersion and explosion CFD calculations using the commercially available tool FLACS. The risk assessment suggested a maximum likely pressure level of 0.1-0.3 barg at the pressure sensors that were used in the study. Somewhat higher pressures are seen elsewhere due to reflections (e.g. under the vehicles). Several other interesting observations were found in the study. For example, the study suggests that for hydrogen releases the level of longitudinal tunnel ventilation has only a marginal impact on the predicted risk, since the momentum of the releases and buoyancy of hydrogen dominates the mixing and dilution processes. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.