Explosion limits for combustible gases

Combustible gases in coal mines are composed of methane, hydrogen, some multi-carbon alkane gases and other gases. Based on a numerical calculation, the explosion limits of combustible gases were studied, showing that these limits are related to the concentrations of different components in the mixture. With an increase of C4H10 and C6H14, the Lower ExplosionLimit (LEL) and Upper Explosion-Limit (UEL) of a combustible gas mixture will decrease clearly. For every 0.1% increase in C4H10 and C6H14, the LEL decreases by about 0.19% and the UEL by about 0.3%. The results also prove that, by increasing the amount of H2, the UEL of a combustible gas mixture will increase considerably. If the level of H2 increases by 0.1%, the UEL will increase by about 0.3%. However, H2 has only a small effect on the LEL of the combustible gas mixture. Our study provides a theoretical foundation for judging the explosion risk of an explosive gas mixture in mines.     

膜吸附生物反应器(MABR)用于饮用水去除有机物

为更加有效地制备优质饮用水,考察了膜吸附生物反应器(MABR)强化去除水中有机污染物的效能.结果表明,当粉末活性炭(PAC)投加量为8mg/L时,MABR对进水中TOC、CODMn、DOC、UV254以及BDOC和AOC的去除率分别达41.3%,59.4%,36.7%,53.5%,67.9%和44.0%.在MABR中,膜的物理截留作用、生物降解作用以及PAC的吸附作用协同完成对溶解性有机污染物的去除;就DOC而言,3种作用的贡献分别为11.1%,7.6%和18.0%.微观分析结果表明,MABR中膜表面的动态污泥层能强化膜对混合液中溶解性有机物的截留.考虑到0.5h的短水力停留时间,MABR无论是从技术上还是从经济上考虑都有着很好的应用前景.     

Interactions of Impact Shock Waves in a Thin-Walled Explosive Container. II. Impact by a Cone-Nosed Projectile

Interaction of impact shock waves that could detonate an explosive (Composition B) confined in a thin-walled container impacted by a cone-nosed projectile is numerically studied, based on the Forest Fire explosive reaction rate model. The normal impact on the container by a small projectile with a conical nose is considered. Depending on the cone angle of the nose part of the projectile, the zone of interaction of initiating shock waves can be remote from the central axis of the impact. The off-the-central-axis detonation is interpreted from the viewpoint of different interaction modes in the explosive container, which are reflected from the cassette wall, change their directions, and superimpose onto each other, leading to explosive detonation.     

载银活性炭/超滤组合技术去除溶解性有机物

为了强化水中溶解性有机物的去除效果,采用载银粉末活性炭与超滤( ultrafiltraction,UF)组合工艺处理微污染原水,研究了溶解性有机炭( dissolved organic carbon,DOC)和紫外吸光度( ultraviolet absorbance,UV254)的去除效果、三维荧光特性、影响因素以及膜污染控制的影响.研究结果表明：与常规粉末活性炭相比,载银活性炭对DOC和UV254的去除效果有较显著改善;在载银量0.10%、0.50%、1.00%和投炭量50、60、80、100 mg/L的条件下,随着活性炭载银量和投炭量的增加, DOC和UV254去除率呈现增加的趋势;单位质量的载银活性炭对UV254和DOC的去除率随投炭量的增加而下降,投炭量80 mg/L、载银量0.50%符合出水水质要求;载银粉末活性炭可以更有效地去除紫外区类腐殖质物质;吸附时间20 min时达到吸附平衡,活性炭在酸性条件下更有利于对有机物的吸附.载银活性炭对膜污染的控制较好,超滤膜经反洗后膜通量恢复较好,膜污染指数增长缓慢.     

基于压力衰减的超滤膜急性与慢性物理破损评价

为验证超滤膜物理破损压力衰减监测的有效性,对破损后膜出水水质的变化和膜内压力的衰减情况进行系统考察.借助医用探针在超滤膜上制造破损点(单个扎孔破损率A=5.46×10-6),发现随着破损率由0增加到5A,超滤膜出水的UV254和DOC仅分别增加24%和26%;出水浊度由0.100 NTU增加到0.290 NTU,但绝对值依然很低,难以反映超滤膜破损的程度.超滤膜急性物理破损时,膜内压力则呈现出急剧下降的趋势,即便破损率仅为1A时,55 k Pa的压力仅66 s就降至零点.因此,以压力衰减监测作为超滤膜物理破损的一种快速、高效、灵敏的评价方法是行之有效的.接触实验表明,粉末炭与超滤膜的短期接触(45 d)不会造成超滤膜的慢性物理破损,不会影响出水水质.     

PAC对水库型水源水中嗅味物质2-MIB的吸附特性

为解决水库型水源水中季节性藻致嗅味物质的应急处理问题,研究了不同水质条件下粉末活性炭(PAC)对水中嗅味物质二甲基异崁醇(2-MIB)的吸附动力学模型和吸附热力学模型,考察了2类水库型水源水中有机物对吸附作用的影响.结果表明:在试验浓度范围内,纯水、原水A和原水B中PAC对2-MIB的吸附过程符合准二级反应动力学模型,吸附等温线符合修正的Freundlich方程,且吸附速率和吸附容量依次降低;原水A、B中PAC对2-MIB的吸附能力显著降低,但原水B中2-MIB在活性炭表面的吸附势能比原水A中的强,这可能主要是由原水中分子质量500 u的小分子有机物引起的微孔吸附竞争及其极性造成的.     

挡墙后爆炸冲击波绕流现象研究

重要建筑通常采用防爆挡墙以防范恐怖主义袭击和意外爆炸。在爆炸冲击下,绕流作用使挡墙墙后的冲击波流场产生变化,导致墙后一定距离处的超压大幅提高,建筑承受比预期更大的荷载。本文用LS-DYNA对近地爆炸下刚性墙后的绕流现象进行了数值模拟,研究了超压时程规律及影响因素。研究发现,距离墙后1.5～2.5倍墙高区域内绕流超压较大,在2倍墙高处出现马赫反应,比无墙时更为危险。研究成果可为重要建筑物防爆挡墙的布置及挡墙后建筑抗爆分析提供参考。     

爆炸法消除焊接残余应力对焊接接头力学性能的影响

采用70mm厚16MnJ对接试板,研究了焊后和爆炸消除应力后两种状态焊接接头冷弯、拉伸、硬度、冲击和疲劳等力学性能的变化。结果表明:爆炸法消除焊接应力不会降低焊接接头的上述力学性能。     

Calculation of temperature field near stagnation point in explosive welding

0IntroductionResearch of temperature field near stagnation pointquantificationally is of great importance to control the qual-ity of explosive welding. If the temperature at the weldinginterface is too high the material will melt in excess andthe metal plates can not be welded well and if the tempera-ture is too lowthe plates can not be well-knit. At the sametime to calculate the heat behavior in the flow field of ex-plosive welding quantificationally is the basis to analyze themetallurgic eff…     

爆炸焊接TA2/316L复合板界面的微观分析

采用扫描电镜、能谱仪和显微硬度计，对爆炸焊接316L／TA2复合板结合界面的显微组织，成分和显微硬度进行了研究。结果表明，界面呈波状；316L与TA2结合界面之间有一层约为5μm的熔化层：波尾处存在漩涡状熔化块，熔化块内有微裂纹和气孔；界面附近的基体组织产生了剧烈的塑性变形；钛一侧存在绝热剪切带；界面附近的原子存在扩散现象；界面区的显微硬度有显著的提高。