本文選題：大型儲罐 + 動態(tài)泄漏��； 參考：《天津大學(xué)》2014年碩士論文

【摘要】：LNG作為一種重要的清潔能源,在我國能源結(jié)構(gòu)中的比重逐年增加,中國的沿海地區(qū)也投建了許多LNG項(xiàng)目。LNG儲罐的的工作溫度為-162°C,一旦儲罐內(nèi)的液體發(fā)生泄漏,LNG吸收外罐熱量,可能出現(xiàn)閃蒸、翻騰等情況。液體極低的溫度使得混凝土外罐壁產(chǎn)生較大的溫度應(yīng)力并且使得混凝土開裂,裂縫使更多的熱量泄漏到罐內(nèi),更加大罐壁的溫度應(yīng)力。研究LNG儲罐在超低溫液體泄漏后罐壁的可靠性可以為儲罐偶然荷載下的安全性評估提供一定參考。本文首先對ANSYS軟件中可靠度分析的基本流程、變量分布和分析方法進(jìn)行介紹;而后對結(jié)構(gòu)體系可靠度、結(jié)構(gòu)分析中的極限狀態(tài)、極限狀態(tài)方程、可靠概率和失效概率的基本知識進(jìn)行簡要介紹,并對結(jié)構(gòu)體系可靠度失效路徑的搜索方法和結(jié)構(gòu)體系可靠度的計(jì)算方法進(jìn)行敘述。本文借助于通用有限元計(jì)算軟件ANSYS,建立儲罐的四分之一模型進(jìn)行應(yīng)力分析。分析得知,泄漏完成時(shí)罐壁溫度場并沒有達(dá)到穩(wěn)定;罐壁內(nèi)側(cè)受拉,外側(cè)受壓�？煽慷确治鰰r(shí)采用響應(yīng)面方法進(jìn)行仿真循環(huán)計(jì)算。對于儲罐在超低溫液體泄漏到環(huán)形空間中的破壞,認(rèn)為儲罐體系是由罐壁液位處的強(qiáng)度破壞和罐壁底部的強(qiáng)度破壞組成的串聯(lián)系統(tǒng);對于每種失效模式,則考慮是由沿罐壁方向內(nèi)側(cè)受拉和外側(cè)受壓的多個(gè)單元組成的并聯(lián)系統(tǒng)失效。對于得到的擬合方程,采用JC法計(jì)算其可靠指標(biāo)。得出可靠指標(biāo)后,計(jì)算其線性化功能函數(shù)。根據(jù)內(nèi)力重分布原理求解后續(xù)單元的響應(yīng)面方程,進(jìn)而計(jì)算其可靠指標(biāo)、線性化功能函數(shù)。采用并聯(lián)體系逐步等效線性求交法得到每種失效模式下可靠指標(biāo),利用界限估計(jì)方法得到體系可靠指標(biāo)和失效概率的范圍,其可靠指標(biāo)范圍為2.5063β2.5840,相應(yīng)的失效概率范圍為0.0049Pf0.0061,可靠指標(biāo)小于規(guī)范數(shù)值,可通過提高外罐壁的混凝土強(qiáng)度來提高儲罐在泄漏工況下的的安全性。
[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 擄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.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU311.2

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