基于SLAB和AFTOX模型的LNG加气站大气环境风险评估

通过设定LNG加气站环境风险事故情景,分别采用SLAB和AFTOX模型模拟预测LNG加气站泄漏和火灾伴生/次生污染物CO的大气环境风险影响程度。结果表明:在风险事故情景下,下风向5 km范围内不同距离的甲烷和CO最大浓度未超过大气毒性终点浓度,甲烷最大浓度出现在下风向10m处,浓度值为32637.575 mg/m^(3);CO最大浓度出现在下风向5 km处,浓度值为1.746E-4 mg/m^(3)。考虑低温液态LNG的危险性和事故触发具有不确定性,LNG加气站在运营过程中仍需重点做好风险防范措施,编制企业突发环境事件应急预案,建立企业/区域环境风险防控体系,有效防控环境风险。

Study on the influence of fracture lengths and fracture angles on residual oil distribution based on the slab model

After fracturing in the pilot area,channeling occurs at a low fracture angle(15).Based on the resistance-water saturation relationship,three-dimensional physical simulation methods are used in the laboratory to study the effect of different fracture angles and lengths on the residual oil distribution during the displacement process.Meanwhile,recovery percent,displacement efficiency and expanding sweep co-efficient to the improvement of recovery percent are also discussed.The results show that the fracture angle and length are closely related to the oil saturation distribution in these models.As the fracture angle increases,the sweep coefficient decreases(0.2412→0.1463),and the recovery percent also in-creases(46.16→56.88%),but the extent of increase has been reduced(7.96→2.96%).The extension of the fracture length is more prone to have a cross-flow phenomenon;the sweep coefficient is reduced(0.2412→0.1463).Compared to the model with 1/2 oil-water well spacing,the recovery percent is decreased by 14.29%.In different fracture models,the increasable sweep coefficient has a greater impact on oil recovery than the increasable displacement efficiency(71.30→28.70%).

Surface turbulence in a physical model of a steel thin slab continuous caster

In the thin slab continuous casting （TSCC） of steel, the issue of optimum fluid flow is very important due to higher casting speeds and has direct influence on the formation of solidified shells and the quality of final products. In the current work, a full-scale physical mod- eling of a thin slab easter on the basis of dimensionless Reynolds and Froude similarity criteria was constructed. The flow pattern in the funnel shaped mold with a new tetra-furcated submerged entry nozzle （SEN） was investigated. To determinate optimum operational parameters, some experiments were carried out under various casting conditions. The results show that the tetra-furcated design of the nozzle leads to a special flow pattern in the mold cavity with three-dimensional recirculating flow. It is also shown that the increase of casting speed and gas injection results in surface turbulence. On the other hand, using a higher depth of SEN decreases the vortex in the free surface of the caster. To avoid surface turbulent and related casting problems, it is recommended to use 30-cm and 40-cm SEN depth at the casting speeds of 3.5 and 4.5 m/min, respectively.

Heat-transfer model on the improvement of continuous casting slab temperature

A heat transfer model on the solidification process has been established onthe basis of the technical conditions of the slab caster in No.3 steel works of Wuhan Iron & SteelCorporation, and the temperature field in the solidifying slab was calculated which was verified bythe measured slab surface temperature. The influences of the main operating factors includingcasting speed, spray cooling patterns, superheat of melt and slab size on the solidification processwere analyzed and the means of enhancing the slab temperature was brought forward. Raising thecasting speed to 1.3 m/min, controlling the flowrate of secondary cooling water and improving thecooling pattern at the lower segments of secondary cooling zone could improve the slab temperatureeffectively. And the increasing the superheat is adverse to the production of high temperature slab.

Physical modeling of gas-liquid interfacial fluctuation in a thick slab continuous casting mold with argon blowing

Combining with the physical model of level fluctuation in a thick slab continuous casting mold with the cross-section of 1500 mm×280 mm and argon blowing, the rationalities of estimating the level fluctuation by three traditional quantitative approaches were discussed, and the effects of gas flowrate, casting speed, and the immersion depth of submerged entry nozzle （SEN） on the level fluctuation were also investigated. As a result, it seems that three traditional quantitative approaches are not very suitable for estimating the level fluctuation in a mold with argon blowing, so a new approach for estimating level fluctuation in the mold with argon blowing was presented. The experimental results show that the level fluctuation is mainly in the region around the nozzle wall. When the casting speeds are larger than a certain value, there is the escape of large bubbles near the nozzle wall, which causes an obvious increase of level fluctuation. Furthermore, optimal process parameters, viz., the gas flowrate of 6 NL/min, the casting speed of 1.1 m/min, and the immersion depth of 170 mm, are presented to restrain the level fluctuation by a physical model.

Water modeling of mold powder entrapment in slab continuous casting mold

The optimal parameters were determined by the water modeling of slab casting. It was found that there are mainly three types of mold powder entrapment in slab continuous casting, i.e., the entrapment caused by the shearing flow near the narrow face of mold, the entrapment caused by vortexes around the submerged entry nozzle （SEN）, and the entrapment caused by the Ar bubbling. Both the velocity of the surface flow and the level fluctuation of the liquids are enlarged with increasing the casting speed, reducing the submersion depth of SEN, decreasing the downward angles of the nozzle outlets, and increasing the Ar flowrate, all of which increase the tendency of mold powder entrapment. Among the four above-mentioned factors, casting speed has the largest effect.

Numerical Evaluation of Two k-εTurbulence Model for Predicting Flow and Solidification in Continuous Casting Slab

A steady three-dimensional fluid flow and solidification model was built based on CFD software by high-Reynolds-number and Lam-Bremhorst low-Reynolds-number k-ε model.During the simulation,the fixed-grid enthalpy-porosity technique was used to represent the solidification,and Darcy law was adopted to simulate the flow in mushy region.The prediction for steel flow and solidification was evaluated by the comparison of two turbulence models.It is found that both Lam-Bremhorst low-Reynolds-number and high-Reynolds-number k-ε models predict the same trend of the steel flow and temperature distribution.However,due to the effect of turbulent flow on heat transfer,the low-Reynolds-number turbulence model predicts longer penetration depth of molten steel in sub-mold region,less shell growth and higher shell surface temperature at the narrow face compared with standard k-ε model.

A Model for Diagnosing the Formation of Internal Cracks in Continuously CastSlabs

The internal cracks in continuously cast slabs are attributed to the excessive tensile strain occurring at the solidifying frontduring the continuous casting process. Based on the understanding, a model for diagnosing the formation of the internal cracks was established, in which the strains at the solidifying front caused by' bulging, straightening or unbending, and roll misalignment were calculated and compared with a critical strain value to estimate whether the internal cracks form. Moreover, the established model was appliedto a real slab caster to reveal the distribution of the strains in casting direction and its effect on the internal cracks. It was proved that themodel was reliable and useful for optimizing the operation of continuous casting.

Model control technologies of dynamic secondary cooling and soft reduction for slab continuous casting

Dynamic model control technologies of secondary cooling and soft reduction of Baosteel are introduced. Model principle and control system architecture are summarized, as well as functions and features. Finally, applications of model technologies are discussed. The self-developed dynamic secondary cooling model and the dynamic soft reduction model have been applied on several casting machines inside and outside Baosteel, desired control effects were achieved with good stability and reliability. Temperature measurement results verified the correctness of model.

Experimental Study of Fluid Flow in Thin Slab Continuous Caster Mould with Water-Model

Model study is an efficient method for optimizing the siructure of the mould and the submerged entry nozzle (SEN). Based on the similarity criteria, a full-scale water model has been established in accordance with the mould of thin-slab caster of the CSP (Compact Strip Production) operation. The effects of SEN structure including outlet area, outflow angle, nozzle width, thick-ness and immersion depth have been studied under high speed casting by measuring the amplitude and the impetus of top waves. By the orthogonal experiment design, not only the influence of the faCtors was estimated, but also the optimum work condition was judged. The rules of the fluid flow phenomena were summarized. The principle for choosing a reasonable structure of SEN was discussed.

钢筋混凝土板柱节点冲切性能研究进展

为提高板柱节点冲切性能从而促进其工程应用,比较了各类抗冲切元件的不同布置形式、形状尺寸、几何参数以及组合形式对节点抗冲切承载力的影响,概括了受损板柱节点修复与加固的研究现状,梳理了不同开洞尺寸、距离、数量、形状及偏心荷载作用下开洞板柱试件抗冲切性能的研究成果,归纳了有无抗冲切钢筋和配置型钢剪力架板柱节点的抗冲切承载力计算方法以及基于机器学习的板柱节点冲切承载力预测方法。结果表明:各类抗冲切元件可通过改变布置形式、形状尺寸、几何参数以及元件组合从而改善板柱节点的冲切性能;板件开洞的尺寸越大、距离越远、数量越多,对节点的抗冲切性能越不利;基于数值模拟和规范改进得出的冲切承载力计算公式仅对特定试验有较高的预测精度,尚未形成较为统一的承载力计算公式,而基于机器学习的冲切承载力预测模型是未来研究的重点;需进一步开展关于受损板柱节点修复与加固方法的研究,对完善板柱节点抗冲切性能研究理论体系具有重要意义。

基于轨道板振动加速度的钢轨振动加速度反演估计与现场验证

为研究高速铁路轨道板与钢轨之间的时空关联规律,提出变分模态-转换器(Variational Mode Decomposition-Transformer, VMD-T)反演模型,该模型通过分解轨道板振动加速度来反演估计钢轨振动加速度.首先,对数据进行预处理并利用双门限法检测振动端点,分离振动信号与静默信号、干扰信号,再将提取后的振动信号整合输入到VMD-T模型.其次,利用VMD模型将轨道板振动加速度数据分解成一系列不同的子模态,并网格遍历搜索与钢轨振动加速度相关系数最大的子模态,以降低原始数据的复杂度以及非平稳性,提升Transformer模型的特征抽取能力.然后,通过Transformer模型对搜索出的轨道板振动加速度子模态与钢轨振动加速度数据进行反演估计训练.最后,将该模型应用于某城际高速铁路轨道板与钢轨实测振动加速度数据反演估计试验.现场高铁试验结果表明:与单一Transformer模型相比,VMD-T模型均方根误差(RootMean Squared Error, RMSE)、绝对平均误差(Mean Absolute Error, MAE)及决定系数(R2_score)分别提升近20%、11%及48.1%,特征学习能力更强,反演估计效果更佳,初步实现钢轨垂向振动加速度幅值非接触式监测估计.

城市重气扩散模型SLAB_URBAN外场试验模拟验证

研究适用于模拟城市中危险化学品扩散的重气扩散模型SLAB_URBAN。模型中考虑了城市冠层内风的特征,即引入基于城市形态学的风速廓线计算方法。分别采用SLAB_URBAN模型和SLAB模型对2000年盐湖城的重气扩散试验进行模拟,主要验证下风方向不同观测距离的气体最大小时平均浓度与源释放速率的比值。结果表明,SLAB_URBAN模型的模拟结果比SLAB模型更接近观测值。从应急反应和安全角度上来说,SLAB_URBAN模型也符合实际工作的需求。

SLAB模型在某工厂液氨泄漏应急响应中的应用

以某工厂储存的液氨泄漏事故为研究对象,将SLAB模型运用到环境应急救援体系中。采用SLAB模型模拟了在冬季、低风速等较不利气象条件下液氨泄漏的IDLH(立即威胁生命和健康)浓度、短时间(15 min)容许接触浓度、居住区大气中有害物质的最高容许浓度的扩散范围。该模型的预测结果比较清晰地反映了环境事故发生后氨气可能扩散的危险区域:在泄漏时间为10 min时,泄漏源下风向0~435.8 m内地面浓度超过IDLH浓度;下风向435.8~797.1 m内地面浓度超过工作场所的短时间最高容许接触浓度;下风向797.1~1 031.6 m内地面浓度超过居住区大气中有害物质的最高容许浓度。根据以上预测结果,救援指挥者可以快速了解事故后果,及时做出正确的救援方案。

夏季高温下支承层斜裂缝诱发纵连板上拱规律研究

在夏季高温作用下,支承层斜裂贯通缝可能导致结构上拱变形,衍生次生病害。基于内聚力和塑性损伤理论建立CRTSⅡ型板式无砟轨道结构有限元模型并与现场实测结果对比验证模型的有效性,分析夏季高温作用下支承层斜裂缝导致的结构上拱变形、离缝、受力和伤损规律。结果表明,温度荷载作用下,斜裂缝一旦贯通,轨道结构变形急剧增大。随温度升高,支承层相互错动,CA砂浆层与支承层先离缝,随后轨道板与CA砂浆层离缝,轨道结构上拱变形。结构性能随温度演化过程可分为0~20℃的缓慢发展阶段、20~30℃的加速发展阶段和大于30℃的飞速破坏阶段。贯通斜裂缝位于板中,角度30°时,轨道结构变形达到最大值26 mm。建议温度大于30℃时,检修重点关注角度不大于45°的板中斜裂贯通缝。

土-承台动力相互作用对砂土场地桩基桥梁地震反应的影响

在桩基桥梁的地震反应分析中,桩-土动力相互作用是个重要的问题,而对于采用低桩承台基础的桥梁,承台埋在土面以下,还存在土与承台之间的动力相互作用。目前,地震反应分析中一般不考虑土-承台动力相互作用的影响,相关研究也很少。为此,利用OpenSees有限元分析程序,基于p-y曲线建立了土-结构一体化桩基单墩模型,选择40条实际岩石场地地震记录作为输入,开展了考虑土-承台动力相互作用的桩基桥梁地震反应分析。结果表明,考虑土-承台动力相互作用后,结构的基本周期会减小,墩底曲率会明显增大,桩顶曲率会大幅减小,但墩顶位移的减小可以忽略。

异钢种连铸混浇模型及试验研究

针对连铸异钢种混浇过程化学成分变化及混浇坯长度预测的问题,基于某厂实际钢液混浇过程,建立了异钢种混浇模型,并结合工业试验研究了连铸工艺条件对混浇坯长度的影响。结果表明:该混浇模型预测的铸坯化学元素含量偏差在±2%以内,可用于混浇坯的化学元素含量预测及长度判定。铸机通钢量保持34.6 m^(3)/h不变,中间包剩余钢液质量从38 t减少至30 t,混浇坯长度从7.13 m减小至5.70 m;中间包剩余钢液质量34 t,通钢量从26.9 m^(3)/h增至42.3 m^(3)/h,混浇坯长度从10.45 m减小至5.70 m;中间包剩余钢液质量34 t,通钢量为34.6 m^(3)/h时,新钢液注入流量从50.0 m^(3)/h增至73.1 m^(3)/h,混浇坯长度均约8.71 m,新钢液注入流量对混浇坯长度的影响可以忽略。以炉次分割线为基准可以实现混浇坯和正常坯的精确判定。

带钢暗梁的板柱结构边节点抗弯性能研究

板柱结构以其传力途径简捷、布置灵活等优势,在工程中得到了广泛的应用,但其也存在容易发生冲切破坏等不足。目前的研究主要集中在板柱结构中柱节点,关于边节点的研究则相对较少,但边柱对结构安全同样至关重要。首先建立了带钢暗梁的钢筋混凝土空心楼盖-钢管混凝土柱边节点有限元模型,并与其他学者的试验结果进行对比,验证了有限元模型的准确性。采用验证过的有限元模型,分析了混凝土楼板厚度、楼板混凝土强度、钢暗梁翼缘宽度等参数对节点抗弯性能的影响。研究结果表明:参数变化对正、负弯矩区的影响不同,楼板厚度、钢暗梁翼缘厚度、强度和高度的增大可以提高节点的抗弯承载力,但是过厚的楼板和楼板混凝土强度的提升会降低节点变形能力;方钢管厚度和轴压比的变化对节点抗弯性能影响不大。

SLAB View软件在含硫天然气井井喷泄漏扩散模拟中的应用

介绍了SLAB重气泄漏扩散模型,并运用SLAB View软件模拟了某含硫气井发生井喷事故H2S云团的扩散过程和危害区域,得出了H2S云团在指定浓度平均时间下的影响范围,以及指定浓度H2S云团出现在最远距离的时间和最远下风向扩散距离。结果表明,SLAB View软件能方便、快速地模拟平坦地形下含硫天然气井喷泄漏扩散过程,预测事故泄漏扩散后果和影响范围。