多源气体泄漏扩散的实验及数值模拟研究

发布时间：2018-08-12 17:41

【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。
[Abstract]:With the rapid development of modern petrochemical industry, there are a large number of inflammable and explosive, toxic and harmful gases in the process of production, use, transportation and storage, and serious accident leaks occur frequently, resulting in huge casualties, economic losses and environmental damage. It has important practical significance.
However, most of the previous studies focused on the single-source leakage and diffusion problems, and there is a serious lack of research on the multi-source leakage and diffusion. However, it is precisely in practice that multi-source gas leakage occurs, such as when suffering from accidents or destructive natural disasters may lead to multi-source gas leakage. The purpose of this study is to reveal the flow characteristics and evolution law of multi-source gas leakage and diffusion, predict its time-space distribution characteristics, and provide a powerful theoretical guidance for emergency rescue and evacuation decision-making.
In this paper, the near-field and far-field regions of leakage and diffusion of multi-source gases are studied systematically. For the near-field region, a small-scale experimental system is established based on the similarity theorem. Helium and carbon dioxide gases are taken as the typical representatives of light and heavy gases, respectively. Schlieren and high-speed camera systems are applied to single-source and multi-source gases. Experimental studies on the flow of light and heavy gas jets in free space with static hysteresis have been carried out to reveal the basic characteristics of the flow field.Meanwhile, a corresponding physical model has been established based on small-scale experiments.The dynamic process of the single-source and multi-source light and heavy gas jets with time has been studied by k-e turbulence steady simulation and large eddy simulation. The intrinsic mechanism of source-to-source interaction is simulated and analyzed by numerical simulation and theoretical analysis. In addition, the influencing mechanism of several factors, such as leakage rate, leakage angle, leakage source spacing and the number of leakage sources, is revealed by experiment, numerical simulation and theoretical analysis.
Based on the existing gas diffusion model, the multi-source gas diffusion model is modified and established for the far-field region. The time-space distribution characteristics and accident consequences of multi-source gas leakage and diffusion are predicted by numerical simulation.
In the light gas diffusion model, based on the most widely used Gauss model, the shortcomings of the Gauss model are corrected by introducing Briggs plume rise model and the definition of ground roughness. According to the gas toxicity standard, the influence area, the downwind direction, the maximum influence distance of the cross wind direction and the change of concentration with time at the fixed position are given. At the same time, the influence law and importance of various factors in the diffusion of light gas leakage are revealed through the analysis of factor influence and factor significance.
In the heavy gas diffusion model, the appropriate heavy gas diffusion model is selected by validation and statistical analysis. After comparing the simulation results of SLAB model with the results of field test, other heavy gas models and real accident cases, it is found that SLAB model has high accuracy and reliability. Based on the SLB model, a multi-source diffusion model was developed to simulate the leakage and diffusion of multi-source heavy gas.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：X937

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