散射管气体鼓泡塔流场分布特性及优化

鼓泡塔因其较好的气-液传质性能具有高污染物脱除效率,被广泛应用于生物化工和烟气处理等领域。鼓泡塔散射管气体分布器的几何尺寸和结构是影响相间传质效率的关键因素,优化塔内流场对于提高鼓泡塔内气-液两相间的传质效率至关重要。采用Fluent软件对有内构件散射管横向进气口式的鼓泡塔进行模拟研究,基于双流体方法和群体平衡模型(PBM)模型对鼓泡塔三维建模,采用一阶迎风差分格式离散,使用Phase Coupled Simple算法进行压力速度耦合。研究了散射管所在圆环直径d分别为0. 375D、0. 5D、0. 625D、0. 75D时(D为鼓泡塔直径),散射管进气口的布置对整体和局部气含率、液速和气泡尺寸等的影响。研究结果表明,随着散射管分布环直径的增大,整体气含率先增大后减少,平均气泡直径先减小后增大;当散射管所在圆环直径d=0. 5D时,鼓泡塔整体气含率和液相循环速度最大,平均气泡直径最小,鼓泡塔流场综合性能最好。     

多级鼓泡塔内液体速度分布的实验研究

液体循环流动是多级鼓泡塔重要流体力学特征之一,文中在内径为282 mm,高2000 mm的鼓泡塔内,采用不同类型的筛板将普通鼓泡塔分割成双级气液鼓泡塔.采用Pavlov管测液速的方法考察了不同筛板、不同表观气速下该鼓泡塔中上下二侧的液体速度分布.根据实验结果得出了液体速度在塔中心处最大,且与表观气速有关,随着表观气速的...     

逆流鼓泡塔气含率分布的试验测量与CFD模拟

利用热膜测速仪测得了气液逆流鼓泡塔内不同表观气速、表观液速和径向位置下的气液信号,采用改进的阈值法进行分析,得到塔内气含率的径向分布。结果表明气含率在各个截面上都是从塔中心到塔壁逐渐减小;同时利用计算流体力学方法对气液逆流的鼓泡塔内的气液两相流动进行了模拟,计算了不同气速和不同液速下的气含率,计算结果与试验数据吻合较好。     

高气速下鼓泡塔中气含率分布的测定

在内径476 mm的鼓泡塔内用压差法测定全塔平均气含率与表观气速的关系,进一步利用响应特性良好的双电导探针,考察了不同气速下局部气含率的分布规律。实验结果表明,利用探针法计算得到的全塔平均气含率值与压差法测定值平均误差仅为4.5%,表明探针法测量局部气含率的可靠性良好。实验还表明在高气速下,除分布板影响区外,局部气含率均类似抛物线型分布;随着气速增加,气含率分布趋于陡峭。以实验为依据,拟合了不同气速下(0.05~1.0 m/s)鼓泡塔中局部气含率的关联式,认为塔内局部气含率与径向位置、表观气速和塔径等因素有关。     

气液鼓泡塔液体流动状态的声发射检测

提出一种基于声发射气液鼓泡塔液相流动状态检测方法,将多通道声发射传感器等距地置于鼓泡塔轴向壁面,提取不同表观气速下的各通道声发射信号,对其做经验模态分解(EMD),根据每个imf的Hurst指数值,提取和重构相应的imf,求其每个信号的平均能量。实验结果表明:鼓泡塔壁处液体轴向流速随着表观气速的增加而增大,当表观气速为14 m/min时,塔壁处液体轴向环流速度最大,当表观气速大于18 m/min时,液体轴向完全变为湍流,出现严重返混。声发射检测法能够有效检测出液体流动状态。     

鼓泡塔内气泡羽流周期性摆动的数值模拟

以二维和三维鼓泡塔内气液二相流动的动态特性为研究对象,寻找各自合适的湍流模型和边界条件设置。二维鼓泡塔的进口气速采用2种不同的方法:①实际进口速度法;②均值修正法。湍流模型选用标准k-ε湍流模型、RNG k-ε湍流模型。结果显示二维模拟使用RNG k-ε湍流模型、三维模拟使用标准k-ε湍流模型能够得到周期性的羽流摆动,且二维鼓泡塔的进口气速采用均值修正法能够得到较合理的摆动周期。     

鼓泡塔反应器的两级气泡模型参数研究

为了研究鼓泡塔反应器两级气泡模型在高黏度下的适用性,采用动态气体逸出法,在内径为286 mm,总高为7 200 mm的鼓泡塔中考察了液体黏度(1.2×10-3—210.4×10-3Pa·s)和操作条件对塔内总气含率,大、小气泡相含率和大、小气泡上升速度等两级气泡模型参数的影响。结果表明:床层总气含率随表观气速的增加而增大,大气泡相含率受液体黏度的影响较小,受表观气速的影响较大;小气泡相含率随黏度的增加而迅速下降,在高气速时受表观气速的影响较小。大、小气泡上升速度均随液体黏度的增加而降低,但随表观气速的升高有着不同的变化关系:前者明显升高,后者略有降低。大气泡直径随着黏度增大而稍有增大,小气泡直径随着黏度增大急剧减小。     

不同分布器对鼓泡塔气液两相流影响的CFD模拟

对不同分布器的鼓泡塔反应器内的气液两相流体动力学行为进行了三维瞬态数值模拟.模型采用欧拉-欧拉双流体模型以及RNG κ-ε湍流模型,研究了不同分布器设计对鼓泡塔反应器气液两相流的影响.模拟得到了鼓泡塔内整体气含率、液相速度矢量分布、时均气含率以及时均轴向液速的径向分布等结果,并对部分模拟结果与文献实验结果进行了比较,其结果吻合得较好,证实了随着分布器开孔越均匀则有利于加强流形的非对称性,从而加剧了气液两相径向混合,但对整体气含率的影响不大.     

鼓泡塔中气泡尺寸分布和局部气含率研究

在内径为0.38 m的鼓泡塔中采用双电导探针法对不同通气速率下的气泡尺寸分布和局部气含率进行了实验研究,分析了气泡尺寸的概率密度分布。结果表明:气泡尺寸随轴向高度的增加而增大,随径向距离增加而减小;鼓泡塔中气液流动可分为过渡流域和充分发展流域,在过渡流域气含率随轴向高度增加而增大,在充分发展流域气含率趋于均值,径向局部气含率分布呈抛物线型下降。高气速下气泡尺寸概率密度分布比低气速下宽,且随轴向高度的增加分布变宽。     

偏心进气式鼓泡反应器内气液流动的大涡模拟

采用气液两相流动的欧拉-欧拉大涡模拟,研究了偏心进气式鼓泡塔内气液两相湍流流动。模拟结果表明：气泡流的运动与气含率的分布与试验结果吻合良好,得到了气液两相湍流瞬态结构形成和演变过程;增大气速使涡结构剧烈变化,液体粘度增高限制了旋涡尺度的发展,反应器高径比减小使涡数量减少。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料，介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比，介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序，对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

Inorganic/organic nanocomposite coatings: The next step in coating performance

Inorganic/organic hybrid materials have considerable promise and are beginning to become a major area of research for many coating usages, including abrasion and corrosion resistance. Our primary approach is to prepare the inorganic phase in situ within the film formation process of the organic phase. The inorganic phase is introduced via sol-gel chemistry into a thermosetting organic phase. By this method, the size, periodicity, spatial positioning, and density of the inorganic phase can be controlled. An important aspect of the inorganic/organic hybrid materials is the coupling agent. The initial task of the coupling agent is to provide uniform mixing of the oligomeric organic phase with the sol-gel precursors, which are otherwise immiscible. UV-curable inorganic/organic hybrid systems have the advantages of a rapid cure and the ability to be used on heat sensitive substrates such as molded plastics. Also, it is possible to have better control of the growth of the inorganic phase using UV curing. It is our ultimate goal to completely separate the curing of inorganic and organic phases to gain complete control over the morphology, and hence optimization of “all” the coating properties. Thus far, it has been found that concomitant UV curing of the inorganic and organic phases using titanium sol-gel precursors afforded nanocomposite coatings which completely block the substrate from UV light while maintaining a transparent to visible light. Also, it has been found that the morphology of the inorganic phase is highly dependent on the concentration and reactivity of the coupling agent. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004, in Chicago, IL.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Some Large Wood-Boring Beetles in Southeastern USA

Ethanol and α-pinene were tested as attractants for large wood-boring pine beetles in Alabama, Florida, Georgia, North Carolina, and South Carolina in 2002–2004. Multiple-funnel traps baited with (−)-α-pinene (released at about 2 g/d at 25–28°C) were attractive to the following Cerambycidae: Acanthocinus nodosus, A. obsoletus, Arhopalus rusticus nubilus, Asemum striatum, Monochamus titillator, Prionus pocularis, Xylotrechus integer, and X. sagittatus sagittatus. Buprestis lineata (Buprestidae), Alaus myops (Elateridae), and Hylobius pales and Pachylobius picivorus (Curculionidae) were also attracted to traps baited with (−)-α-pinene. In many locations, ethanol synergized attraction of the cerambycids Acanthocinus nodosus, A. obsoletus, Arhopalus r. nubilus, Monochamus titillator, and Xylotrechus s. sagittatus (but not Asemum striatum, Prionus pocularis, or Xylotrechus integer) to traps baited with (−)-α-pinene. Similarly, attraction of Alaus myops, Hylobius pales, and Pachylobius picivorus (but not Buprestis lineata) to traps baited with (−)-α-pinene was synergized by ethanol. These results provide support for the use of traps baited with ethanol and (−)-α-pinene to detect and monitor common large wood-boring beetles from the southeastern region of the USA at ports-of-entry in other countries, as well as forested areas in the USA.