空气助力改善气化炉激冷室喷嘴特性的实验研究

设计了4种不同结构的用于气化炉激冷室内喷雾激冷的压力雾化喷嘴,采用马尔文激光粒度分析仪和数码单反照相机分别测量了不同压差、不同水流量等工况参数下的液滴粒径(SMD)D32分布和雾化角变化规律,并对4种喷嘴进行了优化选型。研究结果表明:雾滴粒径随压力的增加而减小,随水流量的减小而减小,空气助力可以明显改善液滴的雾化质量;雾化角随压差的增大先增大后趋于平缓;当压差增大到0.4 MPa时,雾滴粒径、雾化角等参数的变化渐趋平缓。通过比较气化炉激冷室中4种压力式雾化喷嘴的测量结果,1-2号内混式空气雾化喷嘴在4组喷嘴中具有最好的雾化效果,当气压为0.8 MPa,水流量为20 L/h时,SMD极小值为16,因此优选出喷嘴1-2作为气化炉激冷室冷模实验的定型喷嘴。     

空气雾化喷嘴的液滴雾化性能实验研究

采用LSA-Ⅲ型激光粒度仪对一种常用的小流量空气雾化喷嘴的液滴雾化性能进行实验研究。实验主要测定了不同气液比、气相压力和液相压力情况下沿喷雾轴向不同位置处的液滴粒径分布。测定结果表明气液比和气相压力对雾化液滴粒径影响均较大,其中气相压力影响最大,气液比其次,液相压力影响最小。在本实验测定条件下,经过喷嘴雾化后在轴向100、200、300、400和500 mm位置处液滴的表面积平均直径（SMD）和体积平均直径（D43）出现波动性变化。通过对实验测得液滴粒径分布数据的分析,可以得到Rosin-Rammler分布函数中的特征参数和n,为定量计算液滴粒径提供理论基础。     

立体传质塔板CTST喷射特性的研究

立体喷射型塔板的喷射状况对气液两相接触面积有重要影响。在直径570 mm的冷模实验塔内,采用高速摄像仪对CTST的喷射过程参数进行了实验研究,并且基于不稳定波动理论建立了液滴群平均粒径的计算模型。结果表明:喷射孔气速是影响喷射锥角的关键因素,随着喷射孔气速的增加喷射锥角逐渐增大,当喷射孔气速超过7.5 m?s-1时,喷射锥角趋于恒定,其数值稳定在55°左右。随着气速的增加喷射孔处液膜速度显著增大,而液体流量增加时液膜速度略有减小,越靠近喷射孔顶端液膜速度越大。喷射区域内液滴的分布密度接近于Rosin-Rammler分布,在喷射锥角为[20o,40o]区间内的液滴数量比较集中,随着气速和液体流量的增大,液滴分布密度逐渐趋于均匀。液滴群平均粒径随气速的增加而减小,随液量的增加略有增大。正常工作范围内,液滴群平均粒径为1.0~2.5 mm。     

螺旋喷嘴液滴分布特性的实验研究

以水为喷淋介质,研究了螺旋喷嘴的喷淋量与喷淋压力的关系,考察了雾化液滴的粒径分布特性。实验结果表明,随着喷淋压力的增大,喷淋量相应增大,并逐渐趋于平缓;螺旋喷嘴喷雾区喷淋量沿径向形成多个峰,随工作压力增大各峰沿径向外移,处在峰面上液滴的索特直径较峰面间的大;液滴平均粒径随压力升高而趋于均匀,且大喷嘴雾化形成的粒径比小喷嘴的略大。研究结果可为螺旋喷嘴的实际应用提供参考。     

转炉一次除尘新OG系统高效喷淋塔喷嘴雾化特性的模拟

利用离散相模型对转炉一次除尘新OG系统高效喷淋塔内喷嘴的雾化特性进行模拟,分析了喷射角度、喷射压力、喷射流量及喷嘴水平间距等因素对雾化场索太尔平均直径(SMD)和蒸发效率的影响. 结果表明,在一定范围内随喷射角度增加,液滴在雾化场中的覆盖面增大,液滴驻留时间变长,蒸发效率增加,雾化场SMD减小,喷射角度大于60o时,SMD值减小缓慢. 随喷射压力增大,液滴蒸发效率增加,雾化场SMD减小,压力大于1.0 MPa时对SMD的影响较小. 随喷射流量增加,液滴蒸发效率减小,雾化场SMD增加,流量小于0.15 kg/s时,SMD增加幅度偏小. 两喷嘴水平间距越大,液滴分布面积越大,但对雾化场SMD影响较小. 在一定条件下,喷嘴间距约为800 mm时,截面速度分布较均匀.     

多喷嘴脱硫废水烟道蒸发特性模拟分析

火力发电厂湿法脱硫产生的脱硫废水处理难度大,脱硫废水烟道蒸发技术能够有效降低脱硫废水排放量,甚至实现脱硫废水零排放,进而降低电厂运行成本。为研究多喷嘴脱硫废水雾化液滴在锅炉尾部烟道中的蒸发规律,建立了脱硫废水雾化液滴在烟气内的传热传质模型。以某330 MW锅炉尾部烟道为研究对象,利用Ansys Fluent模拟研究了不同喷嘴数量时,烟气和雾化液滴性质对废水运动蒸发过程的影响。结果表明,当脱硫废水流量一定时,随喷嘴数量增多,单个喷嘴废水流量逐渐减少,使废水液滴在烟道内的分布更均匀,喷嘴上方的低温区域面积沿流动方向逐渐增大,平均温度和最低温度升高。在不同烟气和液滴性质条件下,随喷嘴数量增多,液滴的蒸发速度均增大,蒸发时间和运动距离缩短,但降幅逐渐变小,且液滴蒸发距离与蒸发时间正相关。此外,液滴运动速度几乎不受喷嘴数量变化的影响,液滴运动速度主要受烟气速度的影响。不同喷嘴数量时,随烟气温度升高、烟气含水量降低、液滴粒径减少、液滴初始速度初始温度增加,废水液滴的蒸发时间降低,蒸发距离缩短;烟气流速的增加降低了蒸发时间,单喷嘴时,蒸发距离先减小后增大,当烟气流速为10 m/s时,蒸发距离最短为9...     

喷嘴进料对提升管进料段内颗粒浓度分布的影响

在提升管冷模实验装置上考察了喷嘴进料对颗粒浓度径向分布的影响规律. 结果表明,提升管进料段内存在3种形式的颗粒浓度径向分布,在距喷嘴较近的轴向区域,颗粒浓度沿径向呈明显的W形分布,喷嘴进料对颗粒流动的影响很强;在距喷嘴较远的轴向位置,颗粒浓度沿径向呈环-核分布,喷嘴进料对颗粒流动的影响很弱;在二者之间,颗粒浓度沿径向呈弱W分布,喷嘴进料对颗粒流动具有一定影响. 随着喷嘴气速的增加或预提升气速的减小,颗粒浓度逐渐由W形分布转变为环-核分布,喷嘴进料对颗粒流动的影响逐渐减弱. 采用喷嘴射流动量与预提升来流动量比Mj/Mr考察了操作参数及装置结构尺寸对提升管进料段内颗粒浓度径向分布的综合影响. 在实验范围内,动量比对进料段内颗粒浓度径向分布及颗粒流动行为具有明显的影响规律,随着动量比的增加,颗粒浓度逐渐由W形分布转变为环－核分布,操作参数及装置结构尺寸对颗粒流动的影响逐渐减小. 在动量比小于4.21时,操作参数及装置结构尺寸对颗粒流动的影响在H=0.675~1.075 m间的轴向位置基本结束;在动量比增大为4.21时,操作参数及装置结构尺寸对颗粒流动的影响在H=0.375~0.675 m间的轴向位置便已基本结束.     

运用Rosin-Rammler函数研究喷淋塔内液滴粒径分布规律

以水和空气为实验介质,通过拍照法获得喷淋塔内液滴粒径分布,运用Rosin-Rammler(R-R)分布函数对累积粒径分布进行拟合,分析了操作条件对均匀度指数及特征尺寸的影响,并专门就均匀度指数对粒径分布和比表面积的影响进行了计算分析。结果表明,喷淋塔内液滴粒径累积分布与R-R分布函数规律十分吻合;液滴群均匀度指数随喷淋量增大而减小,随空塔气速的增大而提高;增大空塔气速或提高喷淋量均可使液滴特征尺寸减小;通过量纲1化拟合得到R-R分布函数的均匀度指数m及特征尺寸?d的经验计算式,其计算结果与实际值十分吻合;随着均匀度指数的增加,塔内比表面积增大,实现大尺度液滴的破碎可显著提高传质面积。     

基于图像法的环雾状流液滴参数测量与分析

环雾状流广泛存在于石油化工领域,其内部流场测量具有重要意义。本文结合光学图像法和高速摄影技术对撞针式喷嘴的雾化特性进行了测量分析,以此为基础对基于雾化混合的环雾状流中夹带液滴特性开展了实验研究。利用高速摄影技术对喷雾进行可视化,采用单帧单曝光法对液滴尺寸和速度信息进行提取。研究发现,液滴速度随轴向距离增大呈衰减趋势,且相同轴向距离（约在径向位置10mm处）条件下,速度达到峰值;液滴索泰尔平均直径（SMD）随喷嘴孔径d₀的增大而增大,并与液相质量流量m_l和喷嘴上下游压差?p均呈负相关;另外,在环雾状流环境中,相同气压条件下液滴SMD随气相体积流量Q_g增大而减小,而相同气相体积流量条件下SMD随气压p_g增大而增大。基于实验测量结果,以气相韦伯数We_g和液相雷诺数Re_l为主影响参数,引入相间滑移和压力系数建立了基于量纲分析的环雾状流液滴SMD预测模型,平均绝对百分比误差MAPE为11.4672%。     

喷嘴雾化参数轨迹图像法测量实验研究

针对喷嘴雾化多参数同步测量问题,提出了基于图像处理的喷嘴雾化角、雾化细度、液滴运动速度及分布参数测量方法,利用背光阴影成像技术搭建了喷嘴雾化参数测量系统,建立了基于轨迹图像法原理的喷嘴雾化参数图像处理流程与算法,利用标准颗粒测量验证了该方法对颗粒粒径测量的精度,并开展了不同孔径与压力下扇形喷嘴雾化参数同步测量实验研究。结果表明：当雾化压力不变,扇形喷嘴孔径从0.66 mm变为1.10 mm时,雾化细度与液滴平均运动速度分别增加26.82%、10.42%,而雾化角随扇形喷嘴孔径增大而减小16.66%;当扇形喷嘴孔径不变,雾化压力从0.1 MPa增加到0.4 MPa时,雾化角与液滴平均运动速度分别增加47.71%、95.10%,而雾化细度随雾化压力增加而减小44.23%。这为雾化液滴特性研究与喷嘴性能评估提供了有效手段。     

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.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.     

Highly moisture-proof polysilsesquioxane coating prepared via facile sol-gel process

A highly moisture-proof polysilsesquioxane coating was obtained from a new bis-silylated precursor, which was synthesized from 3-aminopropyltriethoxysilane (APTES) and m-xylylene diisocyanate (m-XDI) in tetrahydrofuran (THF) and verified by ¹H MAS NMR. For direct comparison purposes, an SiO₂ coating was also prepared by the Stöber method using tetraethoxysilane (TEOS) as the reactant. Interestingly, the coating obtained from the polysilsesquioxane sol exhibited a much higher moisture resistance capability than its counterpart, which was attributed to its more compact feature between nanoparticles as characterized by N₂ absorption experiment and transmission electron microscopy (TEM). Furthermore, its high transparency of about 92% showed potential for application in the protection of optical crystals.