LNG储罐泄漏工况下的可靠度分析

发布时间：2018-05-30 19:37

本文选题：大型储罐 + 动态泄漏　；参考：《天津大学》2014年硕士论文

【摘要】：LNG作为一种重要的清洁能源,在我国能源结构中的比重逐年增加,中国的沿海地区也投建了许多LNG项目。LNG储罐的的工作温度为-162°C,一旦储罐内的液体发生泄漏,LNG吸收外罐热量,可能出现闪蒸、翻腾等情况。液体极低的温度使得混凝土外罐壁产生较大的温度应力并且使得混凝土开裂,裂缝使更多的热量泄漏到罐内,更加大罐壁的温度应力。研究LNG储罐在超低温液体泄漏后罐壁的可靠性可以为储罐偶然荷载下的安全性评估提供一定参考。本文首先对ANSYS软件中可靠度分析的基本流程、变量分布和分析方法进行介绍;而后对结构体系可靠度、结构分析中的极限状态、极限状态方程、可靠概率和失效概率的基本知识进行简要介绍,并对结构体系可靠度失效路径的搜索方法和结构体系可靠度的计算方法进行叙述。本文借助于通用有限元计算软件ANSYS,建立储罐的四分之一模型进行应力分析。分析得知,泄漏完成时罐壁温度场并没有达到稳定;罐壁内侧受拉,外侧受压。可靠度分析时采用响应面方法进行仿真循环计算。对于储罐在超低温液体泄漏到环形空间中的破坏,认为储罐体系是由罐壁液位处的强度破坏和罐壁底部的强度破坏组成的串联系统;对于每种失效模式,则考虑是由沿罐壁方向内侧受拉和外侧受压的多个单元组成的并联系统失效。对于得到的拟合方程,采用JC法计算其可靠指标。得出可靠指标后,计算其线性化功能函数。根据内力重分布原理求解后续单元的响应面方程,进而计算其可靠指标、线性化功能函数。采用并联体系逐步等效线性求交法得到每种失效模式下可靠指标,利用界限估计方法得到体系可靠指标和失效概率的范围,其可靠指标范围为2.5063β2.5840,相应的失效概率范围为0.0049Pf0.0061,可靠指标小于规范数值,可通过提高外罐壁的混凝土强度来提高储罐在泄漏工况下的的安全性。
[Abstract]:As a kind of important clean energy, the proportion of LNG in the energy structure of our country increases year by year. The working temperature of LNG storage tank is -162 掳C in coastal areas of China. Once the liquid in the tank leaks, it absorbs the heat of external tank. There may be flash, flip, etc. The very low temperature of liquid makes the outer wall of concrete produce larger temperature stress and make the concrete crack. The cracks make more heat leak into the tank and increase the temperature stress of the tank wall. The research on the reliability of LNG tank wall after cryogenic liquid leakage can provide a certain reference for the safety evaluation of storage tank under accidental load. In this paper, the basic process, variable distribution and analysis method of reliability analysis in ANSYS software are introduced, and then the reliability of structure system, the limit state in structural analysis, the limit state equation, The basic knowledge of reliability probability and failure probability is briefly introduced, and the searching method of structural system reliability failure path and the calculation method of structural system reliability are described. In this paper, the 1/4 model of the storage tank is established with the aid of ANSYS, a general finite element software, for stress analysis. The analysis shows that the temperature field of the tank wall is not stable when the leakage is completed, and the inner side of the tank wall is pulled and the outer wall is under pressure. In reliability analysis, response surface method is used to calculate the simulation cycle. It is considered that the tank system is a series system consisting of the strength failure at the liquid level of the tank wall and the strength damage at the bottom of the tank wall, and for each failure mode, The failure of parallel system consisting of several elements which are pulled along the inner side and compressed outside the tank wall is considered. JC method is used to calculate the reliability of the fitting equation. After the reliability index is obtained, the linearization function is calculated. According to the principle of internal force redistribution, the response surface equation of the subsequent element is solved, and its reliability index is calculated, and the function is linearized. The equivalent linear intersection method of parallel system is used to obtain the reliability index of each failure mode, and the range of reliability index and failure probability of the system is obtained by using the boundary estimation method. The reliability index range is 2.5063 尾 2.5840, and the corresponding failure probability range is 0.0049 PF 0.0061. The reliability index is less than the standard value. The safety of the storage tank under the leakage condition can be improved by increasing the concrete strength of the outer tank wall.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU311.2

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