大规模液氢泄漏扩散的数值模拟与影响因素分析

发布时间：2018-02-10 11:02

本文关键词： 液氢泄漏数值模拟参数分析　出处：《浙江大学》2017年硕士论文　论文类型：学位论文

【摘要】：氢作为一种重要的清洁能源,在化工、清洁能源以及航天推进等诸多领域得到了广泛的应用。对于氢的大规模储存、运输和应用,以低温液氢的形态比能量密度较低的常温气氢更为经济可行,有望得到快速发展。然而,一旦储存的液氢发生泄漏,可能会在周围地面形成低温液池,而快速蒸发形成的氢气会发生积聚而形成易爆混合气体,这对周围人群和环境构成巨大的潜在威胁,特别像在作为航天推进剂使用时的大规模液氢储罐,其后果尤为严重。就大规模液氢的泄漏扩散过程开展数值模拟研究,对于掌握大规模液氢的泄漏扩散机制、.制定应急预案、划定紧急疏散区域、评估事故危害后果等都有非常重要的现实意义。本文在综合分析国内外相关研究成果的基础上,建立了基于CFD软件FLUENT的大规模液氢泄漏扩散过程的数值模型。由于风对于氢气在大气中的漂移和扩散有着重要影响,有必要对液氢泄漏源附近的风场先进行模拟与分析。因此,相关模拟研究分成两个阶段进行,第一阶段是对大气边界层内的风场进行稳态的数值模拟,得到大空间范围内风场的模拟数据,第二阶段则利用第一阶段的数值模拟结果作为初始条件,对大规模液氢的泄漏过程进行非稳态的数值模拟。在风场模型的建立过程中,通过分析风的基本特性和脉动风的主要属性,确定平均风剖面的数学表达形式以及风的湍流参数,并利用用户自定义程序对风的参数进行定义。在确定模型的计算流域并对计算流域进行网格划分之后,选择Realizablek-ε模型作为风场的湍流模型,对大空间范围内的风场进行了模拟。以风场的模拟结果作为初始条件,继而进行大规模液氢泄漏和扩散过程的数值模拟。采用Mixture模型作为多相流模型,结合实验中的地面情况,按照砂石的物理性质确定下表面为恒温的地面条件,对液氢的泄漏和扩散过程进行非稳态模拟。通过与NASA的实验结果之间的对比,对模型的准确性进行验证,模拟结果对氢气扩散的动态变化过程进行形象的展示。基于已经构建的大规模液氢泄漏扩散模型,着重对风温、风速、地面温度、地面粗糙度、液氢泄漏速率、泄漏出口的空化率等六个因素的改变对于大规模液氢泄漏扩散行为的影响进行分析。本文的研究结果对于探究建立更精确的大规模液氢泛溢后续行为特征的计算模型,以及建立大规模液氢泄漏扩散的后续补救和防护措施具有指导意义。
[Abstract]:Hydrogen, as an important clean energy, has been widely used in many fields, such as chemical industry, clean energy and space propulsion. The form of cryogenic liquid hydrogen is more economical and feasible than that of atmospheric hydrogen with lower energy density, and it is expected to develop rapidly. However, once the stored liquid hydrogen leaks, a cryogenic liquid tank may be formed on the surrounding ground. Hydrogen, which is rapidly evaporating, accumulates and forms explosive mixtures, posing a huge potential threat to the population and the environment, especially in large-scale liquid hydrogen storage tanks used as space propellant. The consequences are especially serious. A numerical simulation study on the leakage and diffusion process of large-scale liquid hydrogen is carried out. In order to master the mechanism of leakage and diffusion of large-scale liquid hydrogen, to formulate emergency plans and delineate emergency evacuation areas, It is of great practical significance to evaluate the consequences of accidents. Based on the comprehensive analysis of relevant research results at home and abroad, A numerical model of large-scale liquid hydrogen leakage diffusion process based on CFD software FLUENT is established. Since wind has an important effect on the drift and diffusion of hydrogen in the atmosphere, it is necessary to simulate and analyze the wind field near the liquid hydrogen leakage source. The related simulation research is divided into two stages. The first stage is the steady numerical simulation of the wind field in the atmospheric boundary layer, and the simulation data of the wind field in a large space range are obtained. In the second stage, the numerical simulation results of the first stage are used as the initial conditions to simulate the large-scale liquid hydrogen leakage process. By analyzing the basic characteristics of the wind and the main properties of the pulsating wind, the mathematical expression of the mean wind profile and the turbulence parameters of the wind are determined. The parameters of wind are defined by user-defined program. After determining the calculated watershed of the model and meshing the calculated watershed, the realizablek- 蔚 model is chosen as the turbulence model of wind field. The wind field in large space is simulated. The simulation results of wind field are taken as the initial condition, and then the numerical simulation of large-scale liquid hydrogen leakage and diffusion process is carried out. The Mixture model is used as the multiphase flow model, and the ground condition in the experiment is combined. According to the physical properties of sand and gravel, the unsteady state simulation of liquid hydrogen leakage and diffusion is carried out under the condition that the lower surface is at constant temperature. The veracity of the model is verified by comparing with the experimental results of NASA. The simulation results show the dynamic process of hydrogen diffusion. Based on the large scale liquid hydrogen leakage diffusion model, we focus on wind temperature, wind speed, ground temperature, ground roughness, liquid hydrogen leakage rate. The influence of six factors, such as cavitation rate of leakage outlet, on the behavior of large-scale liquid hydrogen leakage and diffusion is analyzed. The results of this paper are helpful to establish a more accurate computational model for the characteristics of the subsequent behavior of large-scale liquid hydrogen spills. And the establishment of a large-scale liquid hydrogen leakage and diffusion of follow-up remedial and protective measures have guiding significance.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ116.27

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