激光多普勒流动测量技术在颗粒流体两相流中的应用

分析介绍了激光多普勒流动测量技术的原理和用ＬＤＶ／ＰＤＰＡ同时测定颗粒流体两相速度和粒径大小的基本方法，并进一步讨论了ＬＤＶ／ＰＤＰＡ测量颗粒浓度和两相流动动态特性的问题。     

粒径分布对循环床内颗粒速度分布的影响

利用激光相位多普勒粒子分析仪（PDPA），在截面尺寸为100mm×15mm的二维循环流化床实验装置上测量比较了平均粒径基本相同的3种不同粒径分布的玻璃珠颗粒在相同操作气速下的颗粒时均速度、脉动速度与数量密度的截面分布特性；初步考察了粒径分布对气固并流上行两相湍流流动行为的影响问题。     

大悬浮轻颗粒固液两相流中的有序结构

应用三维颗粒图像跟踪技术,对竖直管内向上大悬浮轻颗粒固液两相流中分散相即颗粒相瞬时分布进行非接触测量,由此对顺流方向颗粒串组成的有序相分布结构进行观察研究。实验发现,当液体流动速度大于某一确定值时会有明显的颗粒串出现,此时颗粒由于受液体速度梯度诱导的强升力作用而紧贴管壁运动;随着液体流动速度的降低,颗粒串逐渐消失而颗粒沿管径向的分布会向着管中心方向发展;当液流速度进一步降低,颗粒开始在水平方向团聚。分析表明液体流动的剪切作用是颗粒串生成和稳定的机制。实验还显示,随着颗粒相平均份额的增加,流动中串间颗粒的相互作用加强,颗粒分布结构也随之受到影响。     

人体心血管系统中两相流动的数值模拟

本文用液体-颗粒两相流动的方程来描述心血管系统中的血液流动、对导出的二维两相流动基本方程用SIMPLE及IPSA算法进行了离散求解．算例的结果显示：两相系统的描述方法确实能对红组胞的一些运动特性给出恰当的解释，具有单相流动法不可比拟的优点。     

固相颗粒粒径对浆体流变特性影响的实验研究

为研究固相颗粒粒径大小对冰浆类固液两相流流变特性的影响,本文选用三种平均粒径分别为0.31、0.43和0.51 mm的聚乙烯颗粒(密度约为0.922 g/cm3)作为固相,改变混合浆体的流速及固相质量分数,测量浆体在水平圆管内流动的压降值,根据剪切应力与剪切速率的关系,确定了分段拟合流变方程的方法,分析了固相颗粒粒径大...     

超声谱法在颗粒两相流测量中的应用进展

颗粒两相流测量技术指对连续相中的颗粒粒度和浓度等参数进行测量,是两相流测量中非常重要的分支。它与化工、能源、动力、材料、食品等诸多行业都有着密切联系,随着近年来工业的高速发展,颗粒两相流测量技术获得越来越多关注。结合近几年超声谱法在颗粒测量中的研究现状,重点回顾超声谱法颗粒两相流测量技术的应用进展状况,并分析其发展前景。     

在线检测中不同形状煤粉颗粒的流动特性

基于图像识别技术在煤粉二值化图像中进行煤粉颗粒基本特征的提取；建立煤粉颗粒和在线检测装置的三维几何模型；设定气固两相的模拟参数及边界条件后，采用CFD-DEM耦合方法模拟煤粉的气固两相流动，进行气相速度场的分析以及颗粒相的流动分析，研究颗粒的扩散机理，获得颗粒相的速度场和体积分数的分布，归纳出颗粒的流动特性。结果表明：气相在主流通道内流动比较均匀，沿管径增大方向流速逐渐减小；在检测通道内有比较明显的旋涡生成，湍流卷吸效应影响了煤粉颗粒影像的清晰度；形状规则的球形颗粒更易偏离主流流动方向，形成颗粒沉积；形状不规则的颗粒受气力输运作用影响较大，大部分在煤粉气流主流通道内流动；在颗粒受湍流卷吸效应偏离主流流动通道后，粒径较小的颗粒更易运动至检测通道两侧检测元件附近从而影响检测效果。     

插入式静电传感器特性研究

插入式静电传感器在测量气-固两相流参数和保证其传送安全方面有较好的应用。通过建立电极数学模型,讨论了插入式静电传感器电极的插入深度、空间滤波特性和空间灵敏度特性,得到固体颗粒位置对电极上感应电荷的影响情况、感应电极灵敏度分布规律和插入深度L与电极测量信号幅值之间关系。对于连续流动的固相颗粒,当插入式电极插入深度L为管道直径的1/2时为最佳尺寸,此时电极具有低通滤波特性。在利用电极数学模型对电极空间滤波特性理论推导的过程中获得了固相颗粒速度与测量信号截止频率的表达式。实测结果证实了电极的空间滤波特性和空间灵敏度特性。     

基于LDV测速算法的多普勒频率测量不确定度分析和评定

为了明确激光多普勒测速仪(LDV)通过转盘装置校准的低速结果在高速的适用性，分析得到LDV测量流速的不确定度与测量体中的干涉条纹间距和多普勒频率的不确定度相关。由于干涉条纹间距与被测流速无关，则高、低流速测量结果不确定度间的可能差异由多普勒频率算法引入。用基于蒙特卡洛法(MCM)传播概率分布评定测量不确定度的方法分析在不同流速下多普勒频率算法引入的多普勒频率测量不确定度，发现在流速为0.1～340 m/s时，由多普勒频率算法引入的多普勒频率相对不确定度均小于0.03%,且该相对不确定度在不同流速下基本保持不变。流速不同产生的多普勒频率不确定度差异对LDV测速结果的影响小于0.013%,验证了测速算法精度的适用范围。得到了LDV低速校准结果可以应用于高速测量的结论，解决了高流速测量的溯源问题。     

流动颗粒显微图像测量技术研究

针对显微环境下流动颗粒测量的需要,构建了测量平台,研制了基于MEMS工艺的测量器件。在分析流动颗粒显微图像特征的基础上,提出了基于颗粒运动特性的图像测量流程,其中提出了基于基准桢差分的目标提取算法,解决了流动颗粒目标分割的问题,根据图像运动模糊的退化模型,研究了图像模糊恢复的问题。最后以润滑油中的磨损颗粒为例,验证了该文的分析方法对流动颗粒检测的有效性。     

Particle Characteristics and Analysis Using the Laser-Based Phase Doppler Particle Analyzer (PDPA) and Statistical Method

Particle characterization is an important component in product research and development, manufacturing, and quality control of particulate materials. In this article a laser-based phase Doppler particle analyzer (PDPA) was used to measure particle size and velocity. Two different particles, humid particles and fog particles, were tested using the PDPA. Several tests were conducted under different conditions and all data were analyzed using the statistical method and analysis of variance (ANOVA) to see which factor affects particle performance. The humid particle flow rate has a significant effect on both the particle mean diameter and the particle mean velocity with 90% confidence. The type of oil particle has a significant effect on the particle mean velocity with 90% confidence.     

Particle Characteristics and Analysis Using a Laser-Based Phase Doppler Particle Analyzer (PDPA) and Statistical Method

Particle characterization is an important component in product research and development, manufacturing, and quality control of particulate materials. In this study a laser-based phase Doppler particle analyzer (PDPA) was used to measure particle size and velocity. Two different particles including humid particles and fog particles were tested using the PDPA. Several tests were conducted under different conditions and all data were analyzed using the statistical method and analysis of variance (ANOVA) to see which factor affects particle performance. The humid particle flow rate has a significant effect on both the particle mean diameter and the particle mean velocity with 90% confidence. The type of oil particles has a significant effect on the particle mean velocity with 90% confidence.     

The Unique Phase Doppler Particle Analyzer Application and Analysis of Solid Particle Flow in the Fluidized Bed Combustor (FBC) Cold Model

The hydrodynamic effects of varying operating parameters in the fluidized bed combustor (FBC) have been of great interest to the FBC design and manufacturing process. Some experiments to investigate the gas/particle flows in the gaseous fluidized bed were performed with the laser-based phase Doppler particle analyzer (PDPA). In the experiments, the PDPA was used to measure the vertical component of fluidizing particle velocity at one specific position point. The robust experimental design method was used to evaluate the experimental conditions and to analyze the experimental results. An empirical model for the particle velocity vertical component V_y with particle size (S) and fluidizing airflow rate (R) as variables was developed for the FBC cold model. From the model, it was found that vertical component V_y has a strong linear relationship with the fluidizing airflow rate (R), while particle size (S) has less linear relationship to V_y. It can also be seen that V_y increased when fluidizing airflow rate increased and V_y decreased when particle size increased.     

The Unique Phase Doppler Particle Analyzer Application and Analysis of Solid Particle Flow in the Fluidized Bed Combustor (FBC) Cold Model

The hydrodynamic effects of varying operating parameters in the fluidized bed combustor (FBC) have been of great interest to the FBC design and manufacturing process. Some experiments to investigate the gas/particle flows in the gaseous fluidized bed were performed with the laser-based phase Doppler particle analyzer (PDPA). In the experiments, the PDPA was used to measure the vertical component of fluidizing particle velocity at one specific position point. The robust experimental design method was used to evaluate the experimental conditions and to analyze the experimental results. An empirical model for the particle velocity vertical component V_y with particle size (S) and fluidizing airflow rate (R) as variables was developed for the FBC cold model. From the model, it was found that vertical component V_y has a strong linear relationship with the fluidizing airflow rate (R), while particle size (S) has less linear relationship to V_y. It can also be seen that V_y increased when fluidizing airflow rate increased and V_y decreased when particle size increased.     

Nanostructuring of poly(diphenylamine) inside the galleries of montmorillonite organo clay through self-assembly approach

Hollow spheres of poly(diphenylamine) (PDPA) was prepared by confining PDPA in the galleries of montmorillonite organo clay modified with organoammonium cations (MMT). At first instant, diphenylamine (DPA) was loaded into the galleries of MMT and subjected to subsequent oxidative polymerization to form PDPA. beta-naphthalene sulfonic acid (NSA) was used as medium to influence self-assembly of DPA inside the galleries of MMT. Polymerization of self assembled structure resulted hollow spheres of PDPA inside galleries of MMT. X-ray diffraction analysis (XRD), field emission transmission electron microscopy (FETEM), Fourier transform infra-red spectroscopy (FT-IR) and thermogravimetric analysis (TGA) were used to characterize the composites. Transmission emission microscopy of the composite shows the hollow spherical morphology of PDPA. FT-IR, UV-Visible spectroscopy, conductivity measurement and X-ray photoelectron spectroscopy were used to characterize the PDPA extracted from MMT galleries. PDPA extracted from MMT galleries was found to have difference in electronic property than PDPA formed by the conventional method, due to the confinement effect.     

Investigation on the atomization characteristics of a solid-cone spray for dust reduction at low and medium pressures

Water spray is the most widely used means of wet dust reduction, and its atomization parameters are directly related to the effect of dust reduction. In order to obtain the atomization properties of solid-cone spray for dust reduction, the paper used droplet velocity and particle size to characterize its atomization characteristics. The Phase Doppler Particle Analyzer (PDPA) was used to precisely measure droplet sizes and velocities of a solid-cone spray at distances of 15?cm, 25?cm and 45?cm horizontally from the nozzle outlet, using low and medium spray pressures. The results show that the droplet size was fluctuant before spray pressure increasing to 2.0?MPa and then decreased gradually with the increasing of spray pressure. The droplet velocity increased with the raising spray pressure and the velocity at 45?cm is the minimum. The droplet size measurements taken 45?cm from the nozzle exhibited more complex slope changes in particle size curve that were not existed at the closer distances spray of 15?cm or 25?cm, which implies that the near-field spray is more stable than far-field spray. This study is of important significance for further understanding the characteristics of solid-cone spray and guiding its application in dust reduction.     

Template-free mechanochemical route to prepare crystalline and electroactive polydiphenylamine nanostructures

A facile and sustainable mechanochemical route for the synthesis of undoped polydiphenylamine (PDPA) and inorganic acid doped nanostructures are reported. Field emission scanning electron microscopic (FESEM) images highlighted the formation of distinctly different nanostructures for each of the inorganic acid doped PDPA. Elemental analysis carried out for the polymers revealed the presence of more repeating units in their backbone. The X-ray diffraction (XRD) results of the as-prepared PDPA nanostructures indicated the high degree of crystallinity ever reported for PDPA. Spectroscopic profile of the polymers showed that the prepared PDPA is in a doped conducting form. Electrochemical studies performed for the polymeric particles ascertained the redox behaviour and the good electrochemical activity of obtained PDPA samples. The probable mechanistic aspect behind the formation of PDPA nanostructures through this simple and efficient route is discussed.     

Polydiphenylamine/carbon nanotube composites for applications in rechargeable lithium batteries

Polydiphenylamine/single walled carbon nanotube (PDPA/SWNT) composites were synthesized electrochemically aiming at their application as active electrode materials for rechargeable lithium batteries. The electrochemical polymerization of diphenylamine (DPA) on a SWNT film immersed in a 1 M HCl solution was studied by cyclic voltammetry. Comparing cyclic voltammograms recorded on a blank Pt electrode with those obtained for a SWNT film deposited on Pt electrode one observes in the latter case a decrease of the DPA reduction potential. To elucidate electrochemical polymerization mechanism, photoluminescence studies on DPA/SWNT and PDPA/SWNT systems were carried out. Additional information concerning the functionalization process of SWNT with PDPA was obtained by Raman and IR spectroscopy. Using the PDPA/SWNT composite as active material for the positive electrode of a rechargeable lithium cell (LiPF₆ electrolyte), the charge-discharge tests show a specific discharge capacity of ca. 245 mA h g⁻¹, much higher than the 35 mA h g⁻¹ for pure PDPA.     

Fabrication of Functional Nanofibrous Ammonia Sensor

A nanofibrous sensor for ammonia gas is fabricated by electrospinning the composite of poly(diphenylamine) (PDPA) with poly(methyl methacrylate) (PMMA) onto the patterned interdigit electrode. The composite electrospun membrane shows interconnected fibrous morphology. Functional groups in PDPA and the high active surface area of the fibrous membrane make the device detect a lower concentration of ammonia with a good reproducibility. The sensing capability of the device is studied by monitoring the changes in resistance of the membrane with different concentrations of ammonia. The changes in resistance of the membrane shows linearity with the concentration of ammonia in the limit of 10 and 300 ppm. UV-visible spectroscopy reveals the mechanism of sensing ammonia by the membrane.