CNG公交车立交桥下停车场泄漏扩散仿真研究

发布时间：2018-01-11 06:22

  本文关键词：CNG公交车立交桥下停车场泄漏扩散仿真研究　出处：《首都经济贸易大学》2016年硕士论文　论文类型：学位论文

  更多相关文章： CNG公交车 停车场 泄漏扩散 数值模拟

【摘要】：随着人类的进步与发展,天然气逐步成为城市能源的重要组成部分。作为以压缩天然气为燃料的CNG (Compressed Natural Gas)公交车也被大量投入使用,其供气工艺十分复杂,导致泄漏的点源较多,一旦发生泄漏将会对周围人员和财产安全造成威胁。与此同时,城市立交桥作为现代都市的产物应运而生,其桥下空间被大量使用作为停车场所,也包括大量CNG公交车的停放。天然气的密度比空气小,CNG公交车在立交桥下发生泄漏后将会造成天然气的积聚,并形成爆炸性环境。因此,对CNG公交车在立交桥下停车场发生泄漏扩散的情况进行研究和仿真模拟具有重要意义。本文首先对气体的扩散机理和过程进行了分析,了解到气体的扩散是一个繁复的过程。气体扩散是因为受到动力因素和热力因素的影响,其扩散过程一般分为三个步骤：介质的泄漏,流体气云的形成,气云的扩散。其次,基于国内外学者的研究成果,提出了影响气体扩散的主要因素,包括泄漏源、泄漏介质密度、地面条件和气象条件等。然后,以北京市新兴桥、远通桥、大北窑桥三种不同结构的立交桥为原型,采用Gambit软件建立了相应的几何模型,并进行了网格划分。最后,将网格文件导入Fluent进行了模拟计算,并分别讨论了风速、桥体结构、泄漏速率的影响下天然气质量浓度分布情况及爆炸区域的变化规律。对比得到的浓度分布云图可以看出,其他条件相同,当风速为4m/s时,两车之间会发生天然气的大量积聚,爆炸区域会比较大；对比三种立交桥下的泄漏扩散情况时,大北窑桥发生天然气泄漏时更容易形成大片的爆炸区域,远通桥更容易造成天然气较高浓度的积聚；当泄漏速率为20m/s时,桥下爆炸区域的分布范围相比较30m/s、40m/s、50m/s时更广。通过得到的浓度分布云图、爆炸区域分布图,以及不同时间桥下特殊点的浓度变化情况,可为立交桥下停车场的安全管理工作提出一定的指导建议,也可以为事故预警和事故分析等提供重要的依据。
[Abstract]:With the progress and development of mankind. Natural gas has gradually become an important part of urban energy. As a compressed Natural gas based on compressed natural gas (CNG). Buses are also used in large numbers. The gas supply technology is very complex, resulting in a large number of leakage point sources, once the leakage will pose a threat to the safety of people and property around. At the same time, the city overpass as a product of the modern city came into being. The space under the bridge is used as a parking place, including the parking of a large number of CNG buses. The density of natural gas is smaller than that of the air, which will cause the accumulation of natural gas after the leakage of the bus under the overpass. And create an explosive environment. It is of great significance to study and simulate the leakage and diffusion of CNG bus in the parking lot under the overpass. Firstly, the mechanism and process of gas diffusion are analyzed in this paper. It is understood that gas diffusion is a complicated process. Gas diffusion is affected by dynamic and thermodynamic factors. The diffusion process is generally divided into three steps: the leakage of medium and the formation of fluid gas cloud. Secondly, based on the research results of domestic and foreign scholars, the main factors affecting gas diffusion, including leakage source, leakage medium density, surface conditions and meteorological conditions, are put forward. Based on Beijing Xinxing Bridge, Yuantong Bridge and Dabei Kiln Bridge, the corresponding geometric model is established by using Gambit software. Finally, the mesh is divided. The grid file is imported into Fluent for simulation calculation, and the wind speed and bridge structure are discussed respectively. Under the influence of the leakage rate, the gas mass concentration distribution and the variation law of the explosion region are obtained. The comparison of the cloud diagram of the concentration distribution shows that the other conditions are the same, when the wind speed is 4 m / s. There will be a large accumulation of natural gas between the two vehicles, and the explosion area will be larger; Compared with the leakage and diffusion situation under the three kinds of overpass bridge, it is easier to form a large explosion area when the natural gas leak occurs in the Dabei kiln bridge, and the remote bridge is more likely to cause the accumulation of higher concentration of natural gas. When the leakage rate is 20 m / s, the distribution of the explosion area under the bridge is wider than that at 30 m / s, 40 m / s, 50 m / s. The variation of the concentration of special points under the bridge at different times can provide some guidance for the safety management of the parking lot under the overpass, as well as provide important basis for accident warning and accident analysis.
【学位授予单位】：首都经济贸易大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U492.8
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本文编号：1408470