【作者】 朱红亚；

【导师】 孙金华； 王青松；

【作者基本信息】 中国科学技术大学 ， 安全科学与工程， 2013， 博士

【摘要】 随着现代石油化工行业的快速发展,在生产、使用、运输、贮存过程中存在大量易燃易爆、有毒有害气体,重大事故性泄漏频繁发生,造成了巨大的人员伤亡、经济损失和环境破坏。因此气体泄漏扩散问题始终是国内外学者关心和研究的焦点,具有重要的现实意义。然而,前人的研究多集中在单源泄漏扩散问题,而对于多源泄漏扩散的研究存在着严重的缺失。而恰恰在实际中多源气体泄漏却时有发生,如当遭受意外事故或破坏性自然灾害时都有可能导致多源气体泄漏。因此本文针对多源气体泄漏扩散问题进行研究,旨在揭示多源气体泄漏扩散的流动特性及其演变规律,预测它的时间空间分布特性,从而为应急救援和疏散决策制定提供有力的理论指导。本文较系统地从多源气体泄漏扩散的近场区域和远场区域两个方面分别展开研究。对于近场区域,基于相似性定理建立了小尺寸实验系统,以氦气和二氧化碳气体分别作为轻气和重气的典型代表,应用纹影和高速摄像系统对单源和多源轻气、重气射流在静滞自由空间中的流动开展了实验研究,从而揭示了流场的基本特性。同时,结合小尺寸实验建立了相应的物理模型,通过k-ε湍流定常模拟和大涡模拟的方法对单源和多源轻气、重气射流随时间演变的动力学过程,多源间相互作用的内在机理等进行了数值模拟和理论分析。此外,通过实验、数值模拟和理论分析方法三者相结合揭示了泄漏速率、泄漏角度、泄漏源间距以及泄漏源数目等若干因素的影响机制。对于远场区域,在现有气体扩散模型的基础上,修正并建立了多源气体扩散模型,主要通过数值模拟计算的方法对多源气体泄漏扩散后的浓度随时间空间的分布特性及其事故后果进行了预测。在轻气扩散模型中,以应用最为广泛的高斯模型为基础,针对高斯模型中的不足,通过引入Briggs的羽流上升模型和地面粗糙度的定义对其进行了修正。应用修正的高斯模型模拟预测了单源轻气连续泄漏和瞬时泄漏扩散浓度随时间空间的分布情况,结合气体毒性标准给出了不同毒性水平下的影响区域范围,下风向、侧风向的最大影响距离及固定位置处浓度随时间的变化情况等。基于修正的高斯模型发展建立了多源轻气扩散模型,实现了对多源轻气泄漏扩散的模拟计算。同时通过因素影响分析和因素显著性分析还揭示了轻气泄漏扩散中各因素的影响规律和重要性。在重气扩散模型中,通过有效性验证和统计学分析方法选择合适的重气扩散模型。在将SLAB模型的模拟预测结果与现场试验、其它重气模型以及真实事故案例中的结果进行对比后,研究发现SLAB模型具有高度准确性和可靠性。因此对SLAB模型展开了深入研究,揭示了重气扩散中的影响因素及规律,同时在SLAB模型的基础上发展了多源重气扩散模型,实现了对多源重气泄漏扩散的模拟计算。更多还原

【Abstract】 With the rapid development of modern petrochemical industry, there are a lot of inflammable, explosive, toxic and hazardous gases in the production, use, transportation and storage process. And significant accidental leakages from these gases occur frequently, causing enormous casualties, economic losses and environmental pollution. Thus, both of the domestic and foreign scholars focus on the gas leakage and dispersion, which have practical significance.However, previous studies were mostly related to the gas leakage from single source, and there was a serious lack for the research of multi-source gas leakage. In reality, the multi-source gas leakage occurred occasionally, such as when suffered from accidents or natural disaster. Therefore, the research about gas leakage and dispersion from multi-source was conducted in this paper, aiming to reveal its flow characteristics and evolution rules over time, and to predict the temporal and spatial concentration distribution, so as to provide strong theoretical guidance for emergency rescue and evacuation decision-making.In this article, both of the near-field and far-field regions of multi-source gas leakage were studied systematically. For the near-field region, a small-scale experiment system was established based on the similarity theory. Helium and carbon were selected to be the typical representative of light and heavy gas, respectively, The experimental studies on the flow of these two gases released from single and multi-source in stagnant free space were conducted. And the basic characteristics of flow field was revealed, through the Schlieren and high-speed imaging system. Meanwhile, the corresponding physical model were founded with the combination of small-scale experiments. Both of the k-s turbulence unsteady simulation and large eddy simulation have been made to study the dynamics process of light gas and heavy gas, the internal mechanism of multi-source interaction with the theoretical analysis. In addition, according to the results of experiments, numerical simulations and theoretical analysis, the influence mechanism of the factors of leakage rate, leakage angle, distance between multi-source and source number were revealed.For the far-field region, the established gas dispersion models were modified and developed to be that of multi-source. Then, the temporal and spatial concentration distribution characteristics as well as the accident consequences of multi-source gas leaskage could be predicted by numerical simulation.In the dispersion model of light gas, although Gaussian model was most widely used, there were still some deficiency in it. So the Briggs plume rise model and the definition of ground roughness were chested in the Gaussian model. Based on the this modified Gaussian model, the dispersion of single continuous and instantaneous leakage from light gas were both simulated to predict the concentration distribution in the space over time. Combining the toxicity criteria, the influenced area, the maximum downwind and crosswind distance as well as the concentration evolution at a fixed position were all calculated. Furthermore, a multi-source dispersion model of light gas on the basis of this modified Gaussian model was founded. The influencing analysis and significance analysis of involved factors were made to reveal the rules and importance.In various dispersion models of heavy gas, an appropriate one was selected by the methods of validity verification and statistical analysis. It was founded that the SLAB model was quite reliable and accurate by comparing its prediction results with that of field tests, other heavy gas model and real accident case. Therefore, an intensive study of SLAB model was conducted and the impact factors and regularity in the dispersion of heavy gas were revealed. Meanwhile, a multi-source dispersion model of heavy gas based on the SLAB model was developed.更多还原