网格尺度、时间步长和颗粒堆积率对射流床CFD模拟的影响

采用欧拉-欧拉双流体模型,在CFX4.4软件上增加用户自定义子程序模拟了高2.0 m、宽0.3 m的二维射流床内空气和玻璃珠体系的流体动力学特性. 考察了网格尺度、最大颗粒堆积率和时间步长对射流的形成及发展过程、射流穿透深度及射流频率的影响,并与实验数据进行了对比. 结果表明,对于本研究的气固体系,当床层下部纵向网格数为100、时间步长0.0005 s时,不仅可以满足网格尺度和时间步长的无关性要求,而且模拟的射流穿透深度和射流频率与实验测量值的误差分别为5.7%和3.8%. 最大颗粒堆积率在本研究范围对模拟结果的影响可以忽略.     

流化床中射流机制和双射流相互作用

在文献的基础上, 通过实验和模拟的方法研究了射流机制和双射流的相互作用. 采用一个300 mm′51 mm的两维气固流化床,内置两个垂直射流, 使用多路毕托管系统测量射流穿透深度. 使用描述气固流态化的双流体模型进行模拟,用改进的IPSA求解模型方程,通过数值模拟, 讨论了射流产生的机理, 再现了双射流, 并发现双射流的相互作用可分为三类：孤立射流、过渡射流和互作用射流,提出了相应的射流间距判据. 发现影响双射流穿透深度最主要的因素是射流动量、两相间曳力、射流间距和床层表观气速, 建议使用Froude数、Reynolds数、床层表观气速、射流间距和喷口直径来关联不同区域的射流穿透深度. 得到了一个关联式并与文献中的关联式或实验数据做了比较.     

气固流化床内射流穿透深度的CFD模拟及其实验验证

在经典的Gidaspow无黏性双流体模型中考虑离散颗粒对流体和固体动量守恒方程的影响后,建立了一个具有模拟大规模流化床内气固两相流体动力学特性潜在优势的简化数学模型。在CFX4.4商业化软件平台上通过增加用户自定义子程序考察了二维气固流化床(高2.00 m、宽0.30 m)内射流气速、喷嘴尺寸、环隙气速和静床高度对射流穿透深度的影响,并以树脂颗粒(粒径670 μm、密度1474 kg·m^-3)为研究对象在厚度为0.025 m的矩形床内进行了对比实验。结果表明,选取空隙率为0.8的等高线作为射流边界比较合适;射流穿透深度随射流气速或射流喷口尺寸的增加而增大;射流周围环隙气速由0变到最小流化速度时,射流穿透深度随环隙气速增加而增大,在最小流化速度时达到最大值,然后随环隙气速增加单调减小,当环隙气速大于2.5倍最小流化速度时,射流穿透深度减小程度变缓;在相同射流气速下射流穿透深度随着静床高度的增加而减小,静床高度对射流穿透深度的影响随着射流气速增加呈现扩大的趋势。     

双组分射流床中射流穿透深度的研究

使用多相流模型计算了灰熔聚流态化粉煤气化器中双组分的射流穿透深度。较科学地讨论了模拟计算中射流边界的定义；提出在工业气化器的操作条件下，用基于颗粒个数的算术平均法求混合物的平均直径，从而将双组分问题简化为单组分的计算，求出的射流穿透深度与实验值或文献值比较吻合，并发现床层表观气速的影响较大。     

不同形状喷嘴的射流流动与卷吸特性

在不同雷诺数下,基于ANSYS Fluent 6.3软件对圆、椭圆、正方、十字、三角5种形状喷嘴的射流卷吸特性进行数值模拟,分析了轴向射流时均速度分布. 结果表明,三角形喷嘴的射流轴向最大时均速度最大,不同形状喷嘴的射流轴向最大时均速度均随轴向位置增大呈幂函数关系衰减;射流穿透深度与雷诺数和弗劳德准数存在多元线性关系;随轴向位置增大,射流横截面形状由初始段内喷嘴形状逐渐向圆形转化并最终扩展为圆形边界;射流轴线速度半值宽随轴向位置增加呈线性增大趋势,三角形喷嘴的卷吸率是十字形喷嘴的1.92~2.32倍.     

间隔靶对射流侵彻能力影响极限的实验研究

利用实验方法对间隔靶影响射流侵彻能力的极限值进行了确定。通过实验，获得间隔靶间隔值与射流侵彻深度的关系曲线，得出间隔靶对射流侵彻能力的降低极限为5．5％左右，即当间隔靶间隔值为最不利于射流侵彻的间隔值时，每个间隙使射流的侵彻能力下降5．5％左右。通过对实验现象的观察，发现射流在间隔靶之间的飞溅是降低射流侵彻能力的一个主要因素。     

射流位置对碳化反应器混合效果影响的数值模拟分析

为探究射流器结构参数对碳化反应器混合效果的影响，基于CFD（计算流体力学）数值模拟的方法，采用ANSYS模拟软件对比研究了制备碱式碳酸镁的新型射流碳化反应器不同射流位置对混合效果的影响规律。对室温下通入速度为2 m/s的二氧化碳气体及氢氧化镁浆料的射流反应器进行了二维瞬态模拟，并对不同射流位置下的二氧化碳和氢氧化镁浆料速度、浓度分布及反应器腔内流场分布情况进行了对比研究。模拟结果表明，射流在混合腔的速度最大，气液剧烈混合，物料由扩散腔射出后，在反应器内以低于20 m/s的速度均匀混合，在射流位置为1/2H至1/5H范围内，随着射流位置降低，速度亏损最小为1.2%，射流效果更稳定，浆料和气体混合更充分。此外，射流位置对于腔内浆料的浓度有明显影响，当射流位置为1/2H时，浆料和气体浓度比接近1∶1，物料混合效果较好。该模拟优化结果能够为碱式碳酸镁射流碳化反应器的优化设计提供理论依据。     

固定床熔渣气化炉内冷态气固两相流动特性

为了研究固定床熔渣气化炉喷嘴射流速度和安装角度对炉内流场的影响,搭建了固定床熔渣气化炉冷态试验平台,并结合Fluent软件进行了建模。结果发现:(1)随着气体流量和射流速度的不断增加,气体在物料内部的穿透距离不断加长;(2)随着喷嘴下倾角度的增加,射流深度、回流区径向深度及回流区高度呈不断减小趋势;当喷嘴下倾5°~10°布置时为最优工况,料层内部喷嘴方向射流穿透深度适中,炉内流场分布较好;(3)随着喷嘴切圆角度的不断增大,喷嘴对冲碰撞作用越小,气流逐渐偏离径向区域,喷嘴轴截面气体分布量逐渐变少,料层内部射流穿透深度先增大后减小。综合考虑各因素,喷嘴下倾5°并切圆旋转10°布置时,料层内部水平方向射流穿透深度最大,炉内流场分布较好。     

二维射流床空隙率分布

使用ＰＣ－４光导纤维测浓仪测定了二维射流床中的空隙率分布，并考查了静床高、射流管径对空隙率分布的影响，发现在射流喷口上方２．５ｃｍ￣７．５ｃｍ处有一最大空隙率分布区。利用空率分布可定义并求出射流深度，其值与Ｙａｎｇ的关联式计算值吻合。     

射流倾角对喷射器性能影响的数值模拟

对喷射泵内部流动进行了数值模拟,计算了喷射泵在不同射流倾角下的性能参数,分析了喷射泵喷嘴偏离泵体轴线的倾角对其性能和流场的影响。结果表明：随着射流倾角度数的增加,喷射泵喷射系数和气体卷吸量逐渐下降。在喷嘴速度较低时,射流倾角对喷射泵的卷吸量影响较小;随着喷嘴速度的增大,当射流倾角增大时,喷射泵造成的卷吸量下降加剧。     

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.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

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.     

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.     

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。