尾缘锯齿对斜流叶轮气动噪声的影响

针对某型斜流叶轮的气动噪声问题,利用FLUENT软件对尾缘锯齿斜流叶轮的气动噪声进行数值模拟,获得尾缘锯齿斜流叶轮气动噪声的分布特性,并对比分析尾缘锯齿结构对气动噪声的影响规律。结果表明,尾缘锯齿结构可显著降低斜流叶轮整体噪声水平,并且形状越尖锐的锯齿降噪效果越明显,但同时存在叶轮气动性能的损失。研究结果可为斜流叶轮的降噪设计提供理论依据。     

多叶轮阶梯搅拌轴临界转速简便算法

针对多叶轮阶梯搅拌轴的临界转速计算问题,在综合传统算法的基础上,提出了一种实用简便的新算法.该算法首先将多叶轮阶梯搅拌轴简化为无叶轮的二阶搅拌轴,运用等效重量法计算出其临界转速.再将此搅拌轴还原,增加部分运用邓柯莱累加法及积分法进行计算得出该部分临界转速,最终可得出多叶轮阶梯搅拌轴的临界转速.运用ANSYS有限元软件验...     

粉粒体流动性的分析与测量

应用改进的RHEOLABMC1型流变仪对粉粒体内摩擦力及搅拌桨受力进行了测量 ,发现搅拌桨受力可分为两部分 ,即摩擦阻力和形体阻力。对于粘附性较弱的粉体和粒子 ,内摩擦力随转子运动速度的上升而下降 ,而形体阻力与运动速度的一次方近似成正比     

纳米α-FeOOH颗粒的形态和结构

以硫酸法钛白的副产物绿矾为原料，采用滴加法制备纳米铁黄（α－FeOOH）颗粒。研究了反应体系的pH值、反应温度、通氧速率、搅拌速率和添加剂等对铁黄颗粒形态结构的影响，采用XRD、TEM等分析手段对颗粒进行表征。结果表明，调节体系pH值能控制铁黄晶型结构和色相；改变通氧速率、搅拌速率、添加剂种类以及反应温度等可以调节纳米α－FeOOH的大小和分散性。     

高比转速斜流泵内部压力脉动特性的实验研究

为了研究不同工况下高比转速斜流泵内部压力脉动特性和规律,选取某高比转速斜流泵模型为研究对象,在斜流泵叶轮进口段至导叶出口段设置7个压力脉动监测点,采用微型压力脉动传感器采集不同工况下的压力脉动时域信号,并进行频域特性分析。实验结果表明,不同流量工况下,叶轮进口到导叶出口的压力脉动幅值依次降低,同时压力脉动所呈现出的周期性相似波动规律也依次减弱。叶轮进口压力脉动周期性相似波动规律较好,压力脉动幅值也最大,而叶轮出口受叶轮进口流动分离形成的低频大尺度漩涡及叶顶泄漏涡的影响,在小流量工况下的压力脉动周期性相似波动规律相对减弱。导叶进口只有在额定工况1.0Q_(opt)下压力脉动才有动静相干周期性相似波动规律,而导叶出口处的压力脉动幅值最小且在受到导叶数及其发生失速可能产生的低频大尺度漩涡和叶轮出口回流等漩涡的影响,在小流量工况下呈现较弱的周期性相似波动规律。此外,不同工况下叶轮进出口及导叶进口的压力脉动主频都是叶片通过频率,同时叶轮进出口还存在叶片通过频率的高阶谐波,但在导叶出口处的压力脉动主频随流量的变化而变化。     

叶片非均匀分布对斜流叶轮气动噪声的影响

针对某型斜流叶轮的气动噪声问题,基于FW-H方程利用FLUENT软件对叶片非均匀分布斜流叶轮的气动噪声进行数值模拟,获得叶片非均匀分布下斜流叶轮气动噪声的分布特性,并对比分析非均匀分布对气动噪声的影响规律。计算结果表明,叶片非均匀分布可以降低叶片基频及谐频上的声压幅值。研究结果可为斜流叶轮的优化设计提供理论依据。     

半高导叶对离心泵径向力影响数值模拟研究

半高导叶广泛应用于压缩机与涡轮机械中,能有效改善其气动性能,而在离心泵中应用较少,对其性能的影响机理不明确。采用SST k-ω湍流模型对半高导叶离心泵内部流场进行非稳态数值分析,重点研究半高导叶对离心泵压力脉动及径向力性能的影响规律。结果表明:当H/b=0.4～0.6时,离心泵的水力性能最优、高效区较宽;随着流量增加;当H/b=1.0时,离心泵叶轮出口各流道压力对称性在逐渐变好,作用于叶轮上径向力在逐渐降低;当H/b=0～0.8时,离心泵中叶轮出口各流道压力对称性在逐渐变差,径向力在逐渐增加;在各流量工况下,当H/b=0～0.8时离心泵径向力瞬时平均值高于H/b=1.0,但其径向力波峰与波谷差值较小,且作用于叶轮上径向力矢量分布更均匀,叶轮出口液流角波动较稳定。分析结果为离心泵半高导叶设计提供理论依据与参考。     

斜叶桨在气液固三相搅拌反应釜中的混合性能研究

在机械搅拌槽中，针对不同悬浮液浓度及不同通气水平的三相体系，使用斜叶浆（６ＰＴＤ），研究颗粒完全离底悬浮的临界搅拌转速、气体和固体的分散状态、搅拌功率的变化规律及气体在液相中的质量传递系数等混合性能。     

旋转切向流对一体式膜过滤器中膜过滤性能影响的研究

以改善一体式膜过滤器中膜过滤性能为目的,将搅拌引入膜过滤系统,设计新型的旋转切向流强化膜过滤.考察搅拌器的类型以及操作参数(搅拌速度、叶轮直径、膜管与搅拌轴之间的距离)对膜通量的影响,并比较旋转切向流膜过滤与错流膜过滤的能耗,为一体式膜过滤器的应用提供基础数据.     

分子泵叶轮装配过盈量设计与应力分析

动叶轮作为分子泵的关键部件,与芯轴过盈装配,要求在高速状态下仍保持一定的过盈量.本文计算了动叶轮在高速转动时的径向变形、过盈装配时的初始应力状态和转动时应力状态,根据径向变形量的差异和应力优化了装配过盈量,既保证了动叶轮转子强度又使过盈联接可靠.     

Degradation and calcification of a PEO/PBT copolymer series

In this study the influence of polyethylene oxide content (70, 60, 55, 40 and 30%) on degradation and calcification of dense polyethylene oxide (PEO)/polybutyleneterephthalate (PBT) copolymer cylinders was evaluated at subcutaneous sites in goats. Histologically, the 30/70 and 40/60 PEO/PBT implants revealed no signs of calcification and of degradation, although slight surface alterations were evident after 1 year. In contrast, peripheral fragmentation and intermediate calcification were observed for 55/45 and 60/40 PEO/PBT specimens. After subsidence of the inflammatory reaction to the surgical intervention, the tissue reaction to these four PEO/PBT proportions was characterized by a fibrous capsule, although macrophages were frequently seen bordering 55/45 and 60/40 fragments. More extensive degradation and calcification were encountered for 70/30 PEO/PBT samples. Peripheral crack formation occurred from 4 weeks on and at 12 weeks, surface fragmentation was observed for this material. Fragments were usually surrounded by macrophages and, in addition, phagocytes with a foamy appearance were found. Fragmentation and phagocytotic activity increased during the course of the experiment. Using confocal Raman microspectroscopy, it was demonstrated that phagocytes contained 70/30 PEO/PBT fragments in their cytoplasm, as intracellular fragments were chemically composed of PEO and PBT. Systemic effects of the fragmentation were not observed in axial lymph nodes. It can be concluded from the data obtained in this model that a PEO/PBT copolymer series was well toierated. This study showed that PEO content in PEO/PBT copolymers is directly related to degradation and calcification of these materials and that the extent of these parameters may vary under different experimental conditions. The application of confocal Raman microspectroscopy enables analysis of the chemical composition of intracellular fragments and may therefore be a valuable instrument in the prediction of long-term implant performances.     

Mechanical properties and reactions of PBT/PTW blends

The new rubbery poly(ethylene-butylacrylate-glycidyl methacrylate) (PTW) containing epoxy groups was used as a toughener for poly(butylene terephthalate) (PBT). The morphology and mechanical property of the PBT/PTW blend was studied. The reactions between PBT and PTW resulted in improvement of toughness, and were affected by the content of PTW. The reaction during the blending process was followed using an internal mixer. The simulated interfacial reaction between PBT and PTW was studied using the ARES rheometer. The complex viscosity curve could be divided into three stages to characterize the interfacial reactions between PBT and PTW at different temperatures. The temperature strongly affected the rates of the interfacial reaction and diffusion. The reaction of the mixture of PBT and PTW in the internal mixer was much faster than that at the simulated interfacial region. Finally, the differences between the simulated interfacial reaction and the reaction during the real processing were discussed.     

聚对苯二甲酸丁二酯的固相缩聚研究

本文在不同的固相缩聚反应温度和时间的条件下研究了ＰＢＴ固相缩聚反应动力学，测定了反应条件下的表观活化能，认为扩散和化学反应是ＰＢＴ分子量增长的两个主要控制因素。在低温下反应主要由化学控制，而在高温下反应主要由扩散控制，此时的增长曲线偏离二级反应方程。同时，本文对所获得的固相缩聚的ＰＢＴ样品的分子量分布、熔融行为、结晶度和晶粒尺寸进行了研究，得到了一些有规律的结论。     

Photodegradation of aniline by goethite doped with boron under ultraviolet and visible light irradiation

In the present study, goethite and goethite doped with boron (B-goethite) were employed to detect the presence or absence of semiconductor photocatalytic reaction mechanism in the reaction systems. B-goethite was prepared by sol-gel method in presence of boron acid in order to improve its photocatalystic efficiency under the ultraviolet and visible light irradiation. The optical properties of goethite and B-goethite were characterized by ultraviolet and visible absorption spectra and the result indicated that B-goethite has slight red shift in the band gap transition beside their stronger light absorption compared with pristine goethite. Degradation of aniline was investigated in presence of goethite and B-goethite in aqueous solution. It was found that the B-goethite photocatalyst exhibited enhanced ultraviolet and visible light photocatalytic activity in degradation of aniline compared with the pristine goethite. The photocatalytic degradation mechanism of B-goethite was discussed.     

Hydrogen peroxide decomposition in model subsurface systems.

Rates of hydrogen peroxide decomposition, hydroxyl radical production, and oxygen evolution were investigated in silica sand-goethite slurries using unstabilized and stabilized hydrogen peroxide formulations. The goethite-catalyzed decomposition of unstabilized hydrogen peroxide formulations resulted in more rapid hydrogen peroxide loss and oxygen evolution relative to systems containing a highly stabilized hydrogen peroxide formulation. Systems at neutral pH and those containing higher goethite concentrations were characterized by higher rates of hydrogen peroxide decomposition and by more oxygen evolution. The stabilized hydrogen peroxide formulation showed greater hydroxyl radical production relative to the unstabilized formulations. Furthermore, hydroxyl radical production rates were greater at neutral pH than at the acidic pH regimes. The results suggest that when stabilized hydrogen peroxide is injected into the subsurface during in situ bioremediation, naturally occurring minerals such as goethite may initiate Fenton-like reactions. While these reactions may prove to be toxic to microorganisms, they have the potential to chemically oxidize contaminants in soils and groundwater.     

Nitrate reduction over nanoscale zero-valent iron prepared by hydrogen reduction of goethite

Nitrate reduction with nanoscale zero-valent iron (NZVI) was reported as a potential technology to remove nitrate from nitrate-contaminated water. In this paper, nitrate reduction with NZVI prepared by hydrogen reduction of natural goethite (NZVI-N, -N represents natural goethite) and hydrothermal goethite (NZVI-H, -H represents hydrothermal goethite) was conducted. Besides, the effects of reaction time, nitrate concentration, iron-to-nitrate ratio on nitrate removal rate over NZVI-H and NZVI-N were investigated. To prove their excellent nitrate reduction capacities, NZVI-N and NZVI-H were compared with ordinary zero-valent iron (OZVI-N) through the static experiments. Based on all above investigations, the mechanism of nitrate reduction with NZVI-N was proposed. The result showed that reaction time, nitrate concentration, iron-to-nitrate ratio played an important role in nitrate reduction by NZVI-N and NZVI-H. Compared with OZVI, NZVI-N and NZVI-H showed little relationship with pH. And NZVI-N for nitrate composition offers a higher stability than NZVI-H because of the existence of Al-substitution. Furthermore, NZVI-N, prepared by hydrogen reduction of goethite, has higher activity for nitrate reduction and the products contain hydrogen, nitrogen, NH₄⁺, a little nitrite, but no NOx, meanwhile NZVI-N was oxidized to Fe²⁺. It is a relatively easy and cost-effective method for nitrate removal, so NZVI-N reducing nitrate has a great potential application in nitrate removal of groundwater.     

聚乙二醇改性PET／PBT共混体系研究

本文以廉价易得的聚乙二醇(PEG)作结晶促进剂,利用WAXD、DSC研究了PET/PBT共混体系的结晶行为,并以共混体系结晶熔融峰面积计算PET和PBT各自的结晶度。结果发现,加入PEG可以使共混体系冷结晶峰温明显下降,PEG用量越大,冷结晶峰温越低,结晶速度加快;随着PEG分子量增大,当小于2000或等于2000时,冷结晶峰温随之降低,但当分子量≥6000时,冷结晶峰温随之略有升高;加入PEG,对共混体系中PET和PBT各自结晶的作用不同,二者的结晶度随PEG分子量或用量变化不同。     

Catalytic degradation of explosives with goethite and hydrogen peroxide

Goethite (alpha-FeOOH), one of soil contents, can be dissolved in acidic water to produce ferrous ions initiating Fenton reaction with hydrogen peroxide to degrade explosive. In this study, a series of catalytic degradation of nitro aromatic explosives, namely picric acid (PA) and ammonium picrate (AP) have been investigated using the FeOOH/H2O2 process. The controlling factors, such as adsorption of goethite dosage, hydrogen peroxide concentration and UV-light exposure on the oxidation of nitro aromatic explosives were investigated. The results showed that target compounds were adsorbed on the surface of goethite while the oxidation was proceeding. Furthermore, inhibition effect of nitro aromatic intermediates on the reaction was also discussed. A half-life kinetic model has been proposed to predict the half-lives of explosive oxidation in the goethite/H2O2 system.     

PBT/PC共混体系相容性与力学性能的研究

利用聚对苯二甲酸丁二醇酯(PBT)与聚碳酸酯(PC)之间的酯交换反应,自制了PBT与PC的共聚产物作为PBT/PC共混体系的相容剂,讨论了相容剂对该共混体系综合性能的影响.结果表明,相容剂的加入改善了PBT与PC两相间的相容性,共混体系的强度和韧性得到协调.PBT/PC共混体系中组分PC不仅影响了组分PBT的结晶行为,其分子链还影响PBT分子链的有序排列,阻碍PBT的结晶,降低了PBT的成型收缩率.另一方面,PBT的存在也使得PC的耐溶剂性提高,且PBT的含量越高,体系耐溶剂性越强,同时使PC的流动性得以改善.     

Large-scale synthesis of hierarchical alpha-FeOOH flowers by ultrasonic-assisted hydrothermal route

In this paper, we report a facile, an environmental friendly ultrasonic-assisted hydrothermal route for preparation of goethite flower structures using Fe nanopowders at low temperature (85°C). The flower structure consisted of tens of hundreds of nanowires and such structures can further self-assemble with the flake with micro size area. Structural, morphological, and elemental analysis revealed that the products consisted of flower-like structures with high structural uniformity, good crystal quality, and high yields. Influencing factors such as the reaction temperature, pH value, and the deposition time were systematically investigated. A possible formation mechanism was proposed on the basis of the experimental results. Magnetic measurements showed that the as-obtained goethite flowers exhibited weakly ferromagnetic characteristics at room temperature, which were quite different from those of the corresponding bulk materials.