Incident analysis of Bucheon LPG filling station pool fire and BLEVE

An LPG filling station incident in Korea has been studied. The direct cause of the incident was concluded to be faulty joining of the couplings of the hoses during the butane unloading process from a tank lorry into an underground storage tank. The faulty connection of a hose to the tank lorry resulted in a massive leak of gas followed by catastrophic explosions. The leaking source was verified by calculating the amount of released LPG and by analyzing captured photos recorded by the television news service. Two BLEVEs were also studied.     

基于MATLAB技术的LPG储罐重大事故动态模拟评价系统开发与应用

为提高人们对LPG储罐重大事故预测、预防水平和抗灾害能力,根据LPG储罐泄漏、扩散、着火、爆炸等事故的发生和发展,建立一套LPG储罐重大事故动态模拟评价方法,在此基础上进行软件系统的功能、模块和数据设计,应用VC与MATLAB可视化面向对象接口技术实现事故后果模拟评价及特征参数随时间、距离变化过程的可视化。该软件能够脱离MATLAB环境运行,实现了评价结果通过图形直观动态显示,可预测特定位置的破坏情况,评价事故影响范围和危害程度。工程应用表明,该评价系统软件用于LPG储罐重大事故的安全评价是可行的,并可用于其他具有着火和爆炸危险性、毒性的重气或液化气体的生产和贮存企业的安全评价。     

Effect of baffles on pressurization and thermal stratification in cryogenic tanks under micro-gravity

Researches on the impact of baffles on sloshing suppression of two-phase fluids in storage tanks have been widely conducted in literature, particularly at normal gravity. However, few studies focused on the effect of the baffles on self-pressurization and thermal stratification of the fluids in containers. This paper uses Volume of Fluid (VOF) method to simulate thermal behavior of cryogenics in tanks with different baffle structures in microgravity environment. Groups of gravity levels, fill levels and baffle configurations (distances, angles and gaps) are investigated. Up to 54% reduction in pressurization rate was observed by optimizing the baffle settings, which is an attractive improvement for missions of long term storage of cryogen on orbit.     

Modeling the performance of coated LPG tanks engulfed in fires

The improvement of passive fire protection of storage vessels is a key factor to enhance safety among the LPG distribution chain. A thermal and mechanical model based on finite elements simulations was developed to assess the behaviour of full size tanks used for LPG storage and transportation in fire engulfment scenarios. The model was validated by experimental results. A specific analysis of the performance of four different reference coating materials was then carried out, also defining specific key performance indicators (KPIs) to assess design safety margins in near-miss simulations. The results confirmed the wide influence of coating application on the expected vessel time to failure due to fire engulfment. A quite different performance of the alternative coating materials was evidenced. General correlations were developed among the vessel time to failure and the effective coating thickness in full engulfment scenarios, providing a preliminary assessment of the coating thickness required to prevent tank rupture for a given time lapse. The KPIs defined allowed the assessment of the available safety margins in the reference scenarios analyzed and of the robustness of thermal protection design.     

Numerical simulation of the thermal history of droplets during multi-stage atomization

Analyses are made on the characteristics of cooling and undercooled solidification of multi-stage atomized aluminum droplets. Models are established for Newtonian cooling, highly undercooled heterogeneous nucleation and steady-state continuous growth. They are used for numerical simulation of the thermal history of the droplets and the effects of the main atomization process parameters such as the extent of superheat and the speed of the rotating disk. Results show that large undercooling occurs mainly in the later stage of multi-stage atomization while recalescence and rapid quenching take place mainly in the forced cooling stage. The undercooling and cooling rates of the droplets are primarily dependent on the droplet diameter, and the main atomization parameters have little effect on the nucleation and solidification behavior of the droplets.     

Experimental and analytical investigation of thermal coating effectiveness for 3m(3) LPG tanks engulfed by fire

Two large-scale diesel pool fire engulfment tests were carried out on LPG tanks protected with intumescing materials to test the effectiveness of thermal coatings in the prevention of hot BLEVE accidental scenarios in the road and rail transport of LPG. A specific test protocol was defined to enhance reproducibility of experimental tests. The geometrical characteristics of the test tanks were selected in order to obtain shell stresses similar to those present in full-size road tankers complying to ADR standards. In order to better understand the stress distribution on the vessel and to identify underlying complicating phenomena, a finite element model was also developed to better analyze the experimental data. A non-homogeneous and time-dependent effectiveness of the fire protection given by the intumescing coating was evidenced both by finite element simulations and by the analysis of the coating after the tests. The results of the fire tests pointed out that the coating assured an effective protection of the tanks, consistently increasing the expected time to failure. The data obtained suggest that the introduction of fire protection coatings may be a viable route to improve the safety of the LPG distribution chain.     

抗事故包装箱热防护结构的设计及其性能分析

对抗事故包装箱的火灾环境条件进行了研究 ,初步确定了抗事故包装箱的设计模型 ,提出了一种可用于分析评价抗事故包装箱防火 (或高温 )性能的理论模型 ,并对影响结构热响应的几个关键因素进行了有限元数值模拟     

The assessment of the damage probability of storage tanks in domino events triggered by fire

An approach aimed to the quantitative assessment of the risk caused by escalation scenarios triggered by fire was developed. Simplified models for the estimation of the vessel time to failure (ttf) with respect to the radiation intensity on the vessel shell were obtained using a multi-level approach to the analysis of vessel wall failure under different fire conditions. Each vessel “time to failure” calculated by this approach for the specific fire scenario of concern was compared to a reference time required for effective mitigation actions and related to the escalation probability. The failure probability of each vessel was correlated to the probability of scenarios involving multiple vessel failure as a consequence of the primary fire, thus allowing a comprehensive assessment of domino scenarios triggered by fire. The application of the methodology to the analysis of several case-studies allowed the estimation of the quantitative contribution of escalation events triggered by fire to the overall individual and societal risk indexes.     

自然通风对室内环境的影响

本文阐述了自然通风的成因，特点及其产生机理，并对建筑内的自然通风热环境进行了数值模拟分析，改善了因建筑结构设计不合理导致室内通风效果较差的情况。     

Thermal behaviour of autoclaved aerated concrete exposed to fire

The reaction to fire of autoclaved aerated concrete (AAC) has been investigated at multiple dimensional scales. Changes in the chemical composition were detected and analysed by means of thermal analysis methods. Then, the thermal conductivity after different heat treatments was measured at different temperatures ranging from 120 °C to 720 °C. Finally, the evolution of temperature in an AAC wall exposed to the standard fire of ISO 834 has been monitored by built-in temperature sensors. The results hereof were used as input for a transient and non-linear numerical model which has been set up to predict temperatures at different depths of the wall. Measured and calculated results have been compared and discussed.     

Thermal properties of automotive polymers III – Thermal characteristics and flammability of fire retardant polymers

Thermal properties and flammability behavior of two grades of fire retardant polypropylene and nylon 66, and their base resins were determined. A nylon 6 base polymer and a nano-composite based on that polymer were also analyzed. Thermal gravimetric analysis showed more complex degradation patterns for the fire retardant grades as compared to the base resin. This was attributed to decomposition of ingredients present in the fire retardant. Degradation of polypropylene in air started at about 100°C lower temperature than degradation in nitrogen. For nylon, the degradation in both atmospheres occurred at approximately the same temperature. Modulated Differential Scanning Calorimetry (MDSC) measurements were used to determine melting and glass transition temperatures, heats of fusion, heat capacity and thermal conductivity. Both phosphorus-based and halogen-based fire retardants modified the ignition, propagation, and melt-dripping behavior of nylon and polypropylene during burning. Incorporation of a nano-filler was found to be ineffective in imparting fire retardancy to nylon 6. Performance of these materials will have to be evaluated in actual vehicle applications and fire exposures before use on a broad scale basis. Received: 25 August 2000 / Reviewed and accepted: 28 August 2000     

A modified model of pyrolysis for charring materials in fire

A modified model of pyrolysis for charring materials in fire has been proposed in this paper. In this model some special factors which show the effect on pyrolysis are considered, i.e., heat loss by convection and radiation caused by surface temperature rise and shrinkage of char surface are considered. Experimental device is designed specially for validating the reliability of the model. Effects of density of materials and heat radiation on pyrolysis of materials have also been investigated.     

A coupled numerical analysis of shield temperatures, heat losses and residual gas pressures in an evacuated super-insulation using thermal and fluid networks: Part I: Stationary conditions

This paper describes numerical simulations, using thermal networks, of shield temperatures and radiative and conductive heat losses of a super-insulated cryogenic storage tank operating at 77 K. Interactions between radiation and conductive heat transfer modes in the shields are investigated, by calculation of local shield temperatures. As a new method, fluid networks are introduced for calculation of stationary residual gas pressure distribution in the evacuated multilayer super-insulation. Output from the fluid network is coupled to the iterative thermal network calculations. Parameter tests concern thickness and emissivity of shields, degree of perforation, residual gas sources like desorption from radiation shields, spacers and container walls, and permeation from the inner container to the evacuated insulation space. Variations of either a conductive (thickness of Al-film on Mylar) or a radiative parameter (thermal emissivity) exert crosswise influences on the radiative or conductive heat losses of the tank, respectively.     

大型低温液体贮槽绝热系统设计

简介大型低温液体贮槽绝热系统的绝热材料及其主要性能指标;叙述了绝热系统的结构设计、氮封系统设计和基础设计,并分析了目前大型低温液体贮槽在订货、设计和使用中可能存在的几个问题和解决方法。     

地源热泵岩土导热系数测试影响因素分析

建立了地源热泵岩土导热系数现场测试系统的三维数值模型,基于所建数值模型分析了测试时间、舍弃初始小时数、钻孔半径、岩土体初始温度、加热器输入功率等因素对岩土导热系数测试结果的影响。研究结果表明:热响应测试时间应大于70h;对于柱热源模型,随着钻孔尺寸的增大,辨识得到的导热系数逐渐减小;岩土初始温度对岩土导热系数辨识结果没有影响,但采用参数估计法作为辨识方法时,岩土初始温度的测试精度对辨识结果有较大影响;对于纯导热模型,加热器输入功率对岩土导热系数辨识结果没有影响。     

Spalling of concrete cover of fiber-reinforced polymer reinforced concrete under thermal loads

A finite element method using a proposed mesoscopic thermoelastic damage model (MTED) is verified for simulating the cracking process of a concrete section reinforced with fibre-reinforced polymer (FRP) bars. The cracking was due to the significant difference in thermal expansion properties between the concrete and the FRP materials at elevated temperatures. The numerical study reveals that although a conventional elastic analytical method can provide good estimates of the critical temperature increment of concrete cover failure of a cylindrical concrete section that is reinforced with a single bar, it gives too conservative predictions for typical rectangular sections with multiple bars. The study also shows that the concrete cover and the horizontal bar spacing have more influence than the vertical bar spacing on the determination of the critical temperature increments. Horizontal lapping of bars significantly lowers the critical temperature increment.     

Effect of environmental humidity on rate of thermal outgassing

This investigation presents a super-dry venting system that allows the rate of thermal outgassing of an aluminum chamber (length 2 m) to return rapidly to 1 × 10⁻¹³ mbar L s⁻¹ cm⁻² in 4 h without baking. A glove box and an air shower, which provided dehumidified environments with water vapor concentrations of 0.1 ppm and 5 ppm respectively, were utilized to assess the effect of environmental humidity on the rate of thermal outgassing. With super-dry nitrogen venting inside and exposure to the glove box, a thermal outgassing rate of q₁ ∼ 1 × 10⁻¹¹ mbar L s⁻¹ cm⁻² was achieved.     

A study on the numerical simulation of thermal stress during the solidification of shaped castings

In order to study the development of thermal stress and to predict the hot tearing and residual stress of shaped casting, two models were used to carry out the stress analysis of the two stages of solidification. The rheological model [H]–[H|N]–[N|S] was used for the quasi-solid zone while the thermo-elasto-plastic model was used for the period after solidification. Coupling the thermal analysis based on the finite different method with the stress analysis based on the finite element method, a FDM/FEM integrated system of thermal stresses analysis during the solidification process was developed. After experimental verification, the system was put into practical application. The analysis results during the quasi-solid zone show that the visco-plastic strain is an important factor for the occurrence of hot tearing. The hot tearing of a case steel casting and the residual stresses and deformation of a hydro-turbine blade steel casting were analyzed and predicted using the system. The simulation and the practical results were basically in agreement.     

含硫油品储罐自燃灾源温度场的数值模拟

目前在役储罐的温度场难以准确的描述,对安全作业造成隐患。基于国内外储罐自燃机理研究,建立了含自燃灾源的储罐物理模型和数学模型,利用ANSYS有限元平台分析了自燃灾源、保温层厚度、环境温度及空气对流系数对含硫油品储罐温度场的影响.数值模拟结果表明,随着自燃灾源的持续氧化,外壁温度场异常区域逐渐明显;增加保温层厚度,外壁异常区域温差减小的趋势由大变小,当厚度达到30mm时,最大温差降至0.4℃;升高环境温度,外壁异常区域温差均匀降低,当环境温度达到35℃时,外壁温度基本趋于环境温度;增加空气对流系数,外壁异常区域温差快速减小,当空气对流系数达到100W/(m·℃)时,外壁温度接近环境温度,且外壁温差基本趋于一致.