【摘要】：在汽車保有量高速增長、世界能源格局變化和環(huán)保要求日益提高的背景下,具有良好經(jīng)濟和環(huán)保效益的天然氣(CNG)汽車得到大力推廣和普及,CNG氣瓶使用量隨之增加,其中CNG鋼瓶占據(jù)CNG氣瓶比例的90%以上。CNG鋼瓶使用過程中出現(xiàn)的燃燒、爆炸事故往往引發(fā)災(zāi)難性后果。由于火災(zāi)試驗耗資大、危險性高、結(jié)果重復(fù)性差等原因,數(shù)值模擬研究受到越來越廣泛的重視。本文對火災(zāi)環(huán)境下車用CNG鋼瓶的熱及力學(xué)響應(yīng)進行了數(shù)值模擬研究、失效機理分析、失效時間預(yù)測和提出安全消防策略,具有一定的理論價值和現(xiàn)實意義。本文主要內(nèi)容如下： (1)火災(zāi)環(huán)境下車用CNG鋼瓶的熱響應(yīng)數(shù)值模擬研究�；诜謪^(qū)求解、邊界耦合數(shù)值解法和流固耦合傳熱理論,按真實的火災(zāi)試驗?zāi)Ｐ秃秃侠淼募僭O(shè),分別建立火災(zāi)環(huán)境和CNG鋼瓶的物理數(shù)學(xué)模型；然后利用大型流體動力學(xué)分析軟件FLUENT對無風(fēng)和有風(fēng)火災(zāi)環(huán)境進行三維數(shù)值模擬,計算得到火焰的流場、溫度場和鋼瓶外壁的熱流密度分布,證明無風(fēng)環(huán)境下能提供相對均勻和充足的熱量。無風(fēng)火災(zāi)環(huán)境下得到的鋼瓶外壁的熱流密度分布作為鋼瓶模型的熱邊界；同樣運用FLUENT軟件對鋼瓶進行三維瞬態(tài)熱響應(yīng)過程進行數(shù)值模擬,計算得到在420秒內(nèi)瓶內(nèi)介質(zhì)溫度、壓力及氣瓶壁溫度隨時間的變化規(guī)律。 (2)火災(zāi)環(huán)境下車用CNG鋼瓶的力學(xué)響應(yīng)數(shù)值模擬研究。根據(jù)順序熱-結(jié)構(gòu)耦合思想和彈塑性力學(xué)理論,運用ANSYS workbench13.0集成流體力學(xué)分析模塊FLUENT和熱-結(jié)構(gòu)靜力模塊ANSYS Mechanical,首先驗證了有限元模型具有良好的計算精度,然后對處在不同溫度場和壓力場共同作用下的氣瓶壁進行有限元應(yīng)力分析,并進行強度校核,證明了鋼瓶在420秒前滿足強度要求。 (3)火災(zāi)環(huán)境下車用CNG鋼瓶的失效機理初步研究、失效預(yù)測和預(yù)防。通過失效機理分析,提出了意外火災(zāi)環(huán)境下鋼瓶爆破失效時間點與爆破失效壓力的理論預(yù)測方法。首先對鋼瓶進行失效機理分析,提出失效準則,根據(jù)極限載荷有限元分析法得到不同溫度和性能條件下氣瓶爆破壓力的三次多項式擬合曲線,繼而根據(jù)FLUENT計算氣瓶內(nèi)壓變化的熱響應(yīng)曲線,通過二曲線交匯點準確預(yù)測意外火災(zāi)環(huán)境下氣瓶爆破失效時間點與爆破失效壓力,CNG鋼瓶氣瓶的失效時間在火燒420秒左右；根據(jù)失效機理分析,提出了氣瓶安全消防對策。
[Abstract]:Under the background of the rapid growth of automobile ownership, the change of world energy pattern and the increasing requirement of environmental protection, natural gas (CNG) vehicles with good economic and environmental benefits have been vigorously promoted and popularized, and the use of CNG cylinders has increased. CNG cylinders account for more than 90% of CNG cylinders. The combustion of CNG cylinders often leads to catastrophic consequences. Because of the high cost, high risk and poor repeatability of fire test, numerical simulation has been paid more and more attention. In this paper, the thermal and mechanical responses of CNG cylinders in fire environment are numerically simulated, the failure mechanism is analyzed, the failure time is predicted and the fire safety strategy is put forward, which has certain theoretical value and practical significance. The main contents of this paper are as follows: (1) numerical simulation of thermal response of CNG cylinder in fire environment. Based on the partition solution, boundary coupling numerical solution and fluid-solid coupled heat transfer theory, according to the real fire test model and reasonable assumptions, the physical mathematical models of fire environment and CNG cylinder are established respectively. Then using the large-scale fluid dynamics analysis software FLUENT to carry on the three-dimensional numerical simulation to the no-wind and the wind-free fire environment, calculates the flame flow field, the temperature field and the cylinder outer wall heat flux distribution. It is proved that relatively uniform and sufficient heat can be provided in windless environment. The heat flux distribution of the outer wall of the cylinder is used as the thermal boundary of the cylinder model. The three-dimensional transient thermal response process of the cylinder was also simulated by using FLUENT software. The variation of medium temperature, pressure and cylinder wall temperature with time in 420 seconds was calculated. (2) numerical simulation of mechanical response of CNG cylinder in fire environment. According to the theory of sequential thermal-structural coupling and elastoplastic mechanics, the ANSYS workbench13.0 integrated hydrodynamic analysis module FLUENT and the thermal-structural static module ANSYS Mechanical, are used to verify that the finite element model has good calculation accuracy. Then the finite element stress analysis of the cylinder wall under the action of different temperature field and pressure field is carried out and the strength check is carried out. It is proved that the cylinder meets the strength requirement 420 seconds ago. (3) the failure mechanism, failure prediction and prevention of CNG cylinder used in fire environment. Based on the analysis of failure mechanism, the theoretical prediction method of cylinder blasting failure time point and blasting failure pressure under accidental fire environment is put forward. Firstly, the failure mechanism of cylinder is analyzed, and the failure criterion is put forward. According to the finite element analysis of limit load, the cubic polynomial fitting curve of cylinder blasting pressure under different temperature and performance is obtained. Then the thermal response curve of cylinder internal pressure change is calculated according to FLUENT. The blasting failure time point and blasting failure pressure of gas cylinder under accidental fire environment are accurately predicted by the intersection point of two curves. The failure time of CNG cylinder is about 420 seconds after burning. According to the failure mechanism analysis, put forward the gas cylinder safety fire protection countermeasure.
【學(xué)位授予單位】：南昌大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2012
【分類號】：TH49

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