Structural dynamical characteristics induced by vented hydrogen explosion
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摘要: 氢能因具有环保高效等优点,被公认为21世纪最具发展前景的清洁能源,缺点是在使用过程中极易发生爆炸事故。泄爆作为爆炸防护的重要手段,可以有效提高结构在爆炸过程中的安全性和可靠性。为获得结构在氢气泄爆作用下的动力响应特性,本文从实验和数值模拟两个方面展开研究。在12 m×2.5 m×2.5 m的大尺度ISO标准容器中开展了一系列氢气泄爆实验,主要考虑氢气体积分数、点火位置、障碍物布置等参数的影响,并对结构内部超压荷载特征和动力响应演化规律进行了分析。结果表明,结构位移由首个超压峰值主导,并在该阶段与方舱内超压趋势保持一致,且两者峰值之间保持线性关系;加速度则由不稳定燃烧引起的超压高频振荡主导。在实验范围内,位移峰值受氢气体积分数影响显著,且随着氢气体积分数增大而增大。加速度峰值则还受到点火位置的影响,中心点火的情景要大于后端点火的情景。障碍物数量对结构动力响应的影响并非单调关系。此外,基于现场环境振动测试结果,建立了该结构的基准有限元模型。数值模拟及实验结果吻合良好,因此该基准有限元模型可进一步用于不同工况下氢气泄爆荷载作用下结构动力响应的预测和分析。Abstract: Hydrogen is recognized as one of the most promising energies in the 21st century due to the nature of no pollution and high efficiency, unfortunately, it is likely to suffer from explosion in the process of usage. As one of the important ways of disaster, venting can effectively improve the safety and reliability of the structure under hydrogen explosion. In order to study the dynamical characteristics of the structure under vented hydrogen explosion, experimental and numerical studies were conducted in this paper. On the one hand, a number of scenarios were carried out for vented hydrogen explosion in a large-scale ISO container of 12 m×2.5 m×2.5 m to investigate the effects of hydrogen volume fraction, the position of ignition as well as the arrangement of obstacles on the structural dynamics. The characteristics of internal overpressure load and the evolution mechanism of dynamic response were analyzed. Results indicate that the structural displacements are dominated by the first overpressure peak. The trend of displacement agrees well with that of the overpressure, and there is a linear relationship between their peaks. The acceleration is dominated by high-frequency oscillations of the overpressure caused by unstable combustion. Furthermore, the peak of the displacement is significantly affected by hydrogen volume fraction and increases with the increase of hydrogen volume fraction. The peak acceleration is also affected by the ignition position, and the peak acceleration of central ignition is larger than that of back ignition. Additionally, the effects of the number of obstacles on structural dynamic response are not monotonic. On the other hand, a baseline finite element model of the structure is established based on the ambient vibration testing. The numerical simulation results agree well with those of the experimental results. Therefore, the model can be used to predict structural dynamic responses under vented hydrogen explosion.
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表 1 实验工况
Table 1. Test cases
工况 实验 点火位置 障碍物 氢气体积分数/% 1 1~4 BI 0 12、16、20、24 2 5~8 CI 0 12、16、20、24 3 9~12 BI 1 12、16、20、24 4 13~16 CI 1 12、16、20、24 5 17~20 BI 2 12、16、20、24 6 21~24 CI 2 12、16、20、24 表 2 修正前后有限元模型计算结果和实测结果比较
Table 2. Comparisons of natural frequencies between the simulation and test results before and after model updating
阶数 实测频率/Hz 修正前 修正后 频率/Hz 相对误差/% 频率/Hz 相对误差/% 1 17.34 19.06 9.92 17.96 3.58 2 17.93 19.75 10.15 18.61 3.79 3 22.85 23.04 0.83 21.71 −4.99 4 23.91 25.18 5.31 23.77 −0.59 5 24.26 26.91 10.92 25.32 4.37 6 25.43 28.28 11.21 26.49 4.17 -
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