不同尺寸异径管的冲蚀数值模拟研究

运用Fluent软件中的DPM模型对不同入口颗粒浓度下不同尺寸异径管的冲蚀磨损进行数值模拟研究。通过数值模拟得出异径管冲蚀情况与入口浓度和尺寸之间的关系。结果表明,不同尺寸异径管的严重冲蚀区域都位于变径区域壁面;在相同的入口速度下,异径管的冲蚀磨损随着入口浓度的增大而上升;异径管的冲蚀磨损随着变径角度的上升成先上升后下降的现象,且冲蚀严重区域形状随角度的上升从斑点状向环状转变,并存在最严重冲蚀角度。     

T型管道的冲蚀磨损数值模拟分析

三通管道作为石化行业中常见部件。针对天然气三通管道冲蚀破坏问题,采用标准k-epsilon模型,SMPLE算法,对T型三通管道内部流场进行了仿真分析。数值模拟结果表明:T型三通冲蚀部位最易发生在迎流壁面偏向出口处区域;流体速度和砂粒的质量流量对T型三通管道的冲蚀速率有促进作用;管道壁面的最大冲蚀速率在砂粒质量流量大于0.009kg/s之后,增长幅度变大;最大冲蚀速率随着砂粒的圆球度数值的增大而减小,当颗粒中的圆球度在0.1至0.4之间变化时,最大冲蚀速率值减小的幅度相对较大,之后最大冲蚀速率呈缓慢减小的趋势。     

三通管中气液冲蚀磨损的数值模拟研究

运用Fluent软件中的DPM模型对含少量液滴的气体在三通管中的冲蚀情况进行数值模拟,通过模拟实验分析三通管中冲蚀比较严重部位。结果证明在速度相同的情况下,流体对三通管的冲蚀磨损作用随着液滴含量的增加而增大;在液滴含量相同的情况下,流体对三通管的冲蚀磨损作用随着流体入口速度的增大而增大。     

提升管出口T型弯头压降特性的实验分析

在大型循环流化床装置上,以FCC催化剂颗粒为实验物料,针对提升管出口T型弯头用动态压力传感器测量了操作参数和结构尺寸变化对其压降的影响,系统地分析了T型弯头的压降特性。实验结果表明T型弯头的压降与颗粒浓度呈线性关系,与入口速度（提升表观气速）呈二次方关系;T型弯头出口管截面积的减小使得压降显著增大;T型弯头盲管高度的增加可使T型弯头的压降降低,但是当盲管高度增加到一定值时,压降减小不明显。盲管高度对压降的影响是由于盲管高度的增加改变了提升管上部压力的分布,使T型弯头入口压力减小,导致T型弯头的压降降低;同时盲管高度的增加也使提升管出口区域的负压约束区长度增加。盲管所形成的负压约束区构成了对提升管出口的约束作用,T型弯头的盲管高度越大负压约束区越长,约束作用越强。     

沈阳工业大学科研成果介绍电催化氧化有机废水处理设备

为研究集输管道弯管应力集中区域的冲蚀现象,以30°弯管为例,先运用应力分析软件探求弯管应力集中区域;再运用CFD软件对应力集中处的冲蚀现象进行仿真模拟,通过改变入口流速、颗粒的粒径及质量流率,分析冲蚀速率的变动规律。结果表明:弯管应力主要集中在拐角处,且应力集中处的冲蚀区域呈“O”型分布;随入口流速、颗粒粒径及颗粒质量流率的增加,冲蚀速率均呈递增趋势,但不同粒径范围,其增加的速度并不相同,且颗粒质量流率的影响程度要略大于入流流速;弯管拐角外壁面同时承载压力、应力及冲蚀作用,而拐角内侧壁面压力及冲蚀均较低,因此拐角外壁面的破坏概率远大于内壁面,加强拐角外壁面的防护尤为重要。     

模拟分析小颗粒对T型管的冲蚀

T型管道在天然气输送中较为常见的管件,气体在管道内流动时流向会发生改变导致气体直接冲击管壁,此时气体内夹带的微小颗粒也会冲击管壁,形成冲蚀降低管道输送的安全性。为了充分了解颗粒对管壁冲蚀影响,以两端为入口,一端为出口的T型管为研究对象,利用FLUENT模拟不同流速下产生的冲蚀情况。在T型管的一个入口端注入小颗粒并且保持入口条件不变,另外一个入口端不加颗粒而改变气体的速度来观察产生冲蚀的情况。结果显示改变无颗粒进气端的速度会对冲蚀的位置产生影响,同时冲蚀的程度也会产生一些变化。对比分析在不同气体流速下管道内压力云图、速度云图和流线图,来揭示颗粒的运动规律进而说明气体流速对于颗粒对于管壁冲蚀的影响。为实际生产中确定管道危险位置提供依据。     

竖直窄通道充分发展段液固流动特性的数值模拟

采用欧拉-欧拉双流体模型,基于水-玻璃珠体系,对长×宽×高尺寸为240 mm×12 mm×1800 mm的竖直窄通道充分发展段内液固两相流动特性进行了数值模拟。结果表明,沿窄通道竖直方向0.7 m以上液固两相流动进入充分发展阶段,在充分发展阶段的窄通道截面上,狭长方向与狭窄方向各位置颗粒速度及浓度均呈中心区域高、贴近边壁区域低的分布趋势;随着入口液速提高,截面各位置颗粒速度均提高,而颗粒浓度在流道中心区域降低,在贴近壁面区域升高;随着初始固相体积分数增加,截面各位置颗粒浓度均提高,而颗粒速度在流道中心区域略有降低,在贴近壁面区域略有升高;在窄通道截面狭长方向两端靠近三边壁影响的区域存在颗粒增浓效应,在截面狭窄方向颗粒速度和浓度分布梯度较大的区域无量纲占比随着入口液速的提高而提高,随着初始固相体积分数的提高而减小。     

竖直窄通道充分发展段液固流动特性的数值模拟

采用欧拉-欧拉双流体模型,基于水-玻璃珠体系,对长×宽×高尺寸为240 mm×12 mm×1800 mm的竖直窄通道充分发展段内液固两相流动特性进行了数值模拟。结果表明,沿窄通道竖直方向0.7 m以上液固两相流动进入充分发展阶段,在充分发展阶段的窄通道截面上,狭长方向与狭窄方向各位置颗粒速度及浓度均呈中心区域高、贴近边壁区域低的分布趋势;随着入口液速提高,截面各位置颗粒速度均提高,而颗粒浓度在流道中心区域降低,在贴近壁面区域升高;随着初始固相体积分数增加,截面各位置颗粒浓度均提高,而颗粒速度在流道中心区域略有降低,在贴近壁面区域略有升高;在窄通道截面狭长方向两端靠近三边壁影响的区域存在颗粒增浓效应,在截面狭窄方向颗粒速度和浓度分布梯度较大的区域无量纲占比随着入口液速的提高而提高,随着初始固相体积分数的提高而减小。     

基于仿生结构的方管冲蚀数值模拟分析

非常规油田开采需要大量的管道对油气进行输送,在天然气的输送过程中,固相杂质会随着高速流动对管道的内壁造成冲蚀磨损,影响管道的使用寿命.为了进一步探究管道减磨、抗磨的方法,本文设计了一种仿生型弯头,采用CFD数值方法对普通管道和仿生管进行了冲蚀的数值模拟,结果表明仿生弯头在工况(颗粒粒径100um、速度10m/s、质量流...     

基于Ansys Fluent及正交试验的90°弯管冲蚀影响因素分析

管道系统在物料运输过程中,受固体颗粒的冲蚀,常导致管道弯头失效。应用Ansys Fluent软件进行90°弯管冲蚀模拟,得出入口流速、颗粒质量流量、颗粒粒径、管道直径、弯径比均会影响90°弯管冲蚀率。采用正交试验方法分析得到冲蚀影响因素主次顺序为:入口流速颗粒质量流量弯径比管道直径颗粒粒径;通过方差分析得出,入口流速、颗粒质量流量对弯管冲蚀率的影响高度显著,入口流速、颗粒质量流量、颗粒粒径间交互作用不显著。     

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。