悬浊液透光脉动颗粒在线检测技术及其应用(待续)——透光脉动颗粒检测理论

在国外现有研究的基础上 ,从理论上推导出了悬浊液透光率脉动值的解析式。对该解析式的进一步研究表明 ,悬浊液透光率脉动值VR 或R(R=VR/V)主要与悬浊颗粒大小有关 ,颗粒个数浓度N对VR 或R的影响较小 ,悬浊颗粒凝聚时透光率脉动值总是增大的。给出了单一粒径组成和具有一定粒径分布的悬浊液 ,根据其透光率脉动值计算颗粒平均粒径的解析式。     

旋转压力式喷嘴喷雾特性的实验研究

以纯水为雾化介质,研究了旋转压力式喷嘴喷雾特性.测得了喷嘴流量、喷雾角、雾滴直径与压力的变化关系,以及雾滴粒径和喷嘴径向喷雾通量的分布情况.实验结果表明：压力和喷嘴孔径同时影响喷嘴流量、喷雾角、雾滴直径;雾滴粒径主要集中在80～200μm之间.旋转压力式喷嘴的喷雾通量在雾锥中心处最大,随着压力增大,邻近雾锥中心的区域喷雾通量变大,在雾锥边缘处喷雾通量变小.实验结果为旋流压力式雾化器的工业化设计提供了重要的实验依据.     

悬浊液透光脉动颗粒在线检测技术及其应用（待续）—透光脉动颗粒检测理论

在国外现有研究的基础上，从理论上推导出了悬浊液透光率脉动值的解析式。对该解析式的进一步研究表明，悬浊液透光率脉动值VR或R（R＝VR／V）主要与悬浊颗粒大小有关，颗粒个数浓度N对VR或R的影响较小，悬浊颗粒凝聚时透光率脉动值总是增大的。给出了单一粒径组成和具有一定粒径分布的悬浊液，根据其透光率脉动值计算颗粒平均粒径的解析式。     

喷雾增湿过程的数学模型

根据计算流体动力学的原理,论述了喷雾增湿过程中增湿塔内的风场流动特性和雾滴的运动状态,同时对雾滴在运动过程中的受力情况进行了分析,建立了一个基本上能较清楚描述喷雾增湿塔的操作特性,反映喷雾增湿操作过程中粒子运动轨迹的数学模型,并采用时间增量法和拖动坐标系对数学模型进行了求解。     

基于三目视觉的圆柱尾迹层析PIV测量

多数机械设备如换热器、汽轮机、燃气轮机等内部流场均具有内部空间狭小、流场流动复杂的特点。目前对于该类流场测量多采用二维粒子图像测速（PIV）的方法,难以反映真实的流场速度分布;同时多数三维流场测量系统设备复杂且昂贵,难以应用到狭小的空间测量中。因此本文搭建了一套基于三台相机的三维流场测量系统,针对某矩形水流管道,应用层析PIV技术对圆柱尾迹的低速流场进行了测量,成功观察并重建了圆柱产生的三维卡门涡街流场。测量区域约为30mm×30mm×5mm,三维空间分辨率达到20voxels/mm,重投影误差小于0.5%。研究结果表明,采用本文搭建的三相机层析PIV系统测量得到的三维矢量场合理地反映了圆柱尾迹的流动结构;MLOS算法相较于传统MART算法能够有效降低重构所耗时间,并能够达到同样的重建精度。本文搭建的测量系统也可用于其他低速流体实验中,而三相机的布置为测量狭小空间的复杂流场提供了可能。     

大型喷雾粒径分布的图像法测量

雾化技术在能源、化工等领域应用广泛,研究雾化机理和优化雾化喷嘴性能的前提是对其雾化液滴尺寸及粒度分布进行准确有效的测量和表征。目前常用的雾化液滴粒度测量技术,如基于光散射或衍射原理的激光粒度仪和相位多普勒分析仪等,能够较准确地测量粒径分布比较窄、最大粒度在2000 μm以下的喷雾,但对含特大颗粒且粒径分布很宽的喷雾,往往难以得到可靠结果甚至不可能进行测量。本文提出了用图像法测量这类大流量喷雾,构建了图像法测量系统,编写了图像处理程序,经标定实验后,采用该系统对某喷嘴喷雾液滴粒径分布及规律进行了测量研究。研究结果表明图像法可用于大型喷雾液滴粒度及分布的测量。     

大型喷雾粒径分布的图像法测量

雾化技术在能源、化工等领域应用广泛,研究雾化机理和优化雾化喷嘴性能的前提是对其雾化液滴尺寸及粒度分布进行准确有效的测量和表征。目前常用的雾化液滴粒度测量技术,如基于光散射或衍射原理的激光粒度仪和相位多普勒分析仪等,能够较准确地测量粒径分布比较窄、最大粒度在2000μm以下的喷雾,但对含特大颗粒且粒径分布很宽的喷雾,往往难以得到可靠结果甚至不可能进行测量。本文提出了用图像法测量这类大流量喷雾,构建了图像法测量系统,编写了图像处理程序,经标定实验后,采用该系统对某喷嘴喷雾液滴粒径分布及规律进行了测量研究。研究结果表明图像法可用于大型喷雾液滴粒度及分布的测量。     

考虑多组分颗粒运动各向异性的鼓泡流化床生物质气化数值模拟

考虑鼓泡流化床生物质气化过程多组分颗粒运动特点,建立多组分颗粒速度脉动二阶矩模型,结合化学反应动力学方法描述鼓泡流化床内生物质气化过程。模拟的气体组分结果与采用原始颗粒动理学模型的模拟结果进行了比较,并给出了两种粒径碳颗粒的浓度与温度瞬时分布。分析了两种碳颗粒的速度时均径向分布及速度脉动二阶矩时均径向分布,两种碳颗粒的速度分布一致,说明不同粒径碳颗粒混合充分。粒径较大的碳颗粒速度脉动二阶矩在轴向与径向上均较大,粒径的增加使得颗粒速度脉动增强。模拟统计了计算域内两种颗粒的速度脉动各向异性随颗粒浓度变化关系,各向异性随颗粒浓度的增加逐渐减弱,粒径较大的碳颗粒在计算域内的各向异性平均效果不如粒径较小的碳颗粒明显。     

计算机在圆柱形容器简体与接管相贯放样中的应用

针对制造过程中容器筒体和接管相贯曲线的精确、高效性和方便放样的问题,根据相贯线的几何原理,推导出空间两圆柱相贯线的平面展开图尺寸计算公式;根据应用的实用性,对程序的运行环境和开发环境进行了选择,完成了程序的设计和编制,实现了圆柱壳相贯结构相贯曲线放样的计算机化.多种相贯结构的验证结果表明,该程序操作简单,计算结果精确,...     

反相层析分离紫杉醇的柱动力学

通过考察物质在液固两相之间的基本传递现象 ,建立了常压非线性柱层析过程的速率模型 .对紫杉醇在C18-硅胶柱上分离纯化过程进行了数学分析 .模型计算值与实验值吻合良好 .研究物料浓度、进料速度、层析柱大小等因素对紫杉醇层析过程的影响说明 ,建立的柱动力学模型能指导紫杉醇层析过程简捷而有效地放大     

水在非相溶油中滴流雾化的界面追踪模拟

基于欧拉法和流体体积函数建立了描述相界面运动、变形、破碎等复杂变化的界面追踪模型(VOF-CSF),该模型采用了二相界面重构技术,并考虑了界面张力和接触角的影响,将水在非相溶油中滴流雾化形成液滴过程简化为二维轴对称数值模拟,模拟了层流环境中低喷射流率下液滴形成的全过程.模拟结果表明:在滴流雾化方式下,液滴形成过程由液滴...     

Simulation of the performance of electrical capacitance tomography for measurement of dense phase pneumatic conveying

A method for the estimation of image distortion which can occur in the reconstruction of electrical capacitance tomography (ECT) data for pneumatic conveying process is presented. Image distortion is associated the finite sampling rate of tomographic instrumentation which arises from changes in the distribution of phases occurring during a measurement cycle. The method uses an algorithm which provides the solution of the inverse and forward problems for an idealized 2-D sensor and to visualize the movement of powder slugs. The influence of the geometry of the sensor electrodes and the nature of slug perturbation on the fidelity of the reconstructed image is discussed. The practical implications of the simulation for the application of capacitance tomography for monitoring and control of dense phase conveying are discussed.     

电容层析成像在煤粉料仓下料中的应用

煤粉料仓下料是气流床粉煤气化工艺中粉体供料单元的重要组成部分,其安全稳定运行具有重大的经济意义。提出将电容层析成像（ECT）技术用于煤粉料仓下料,从而实现研究手段的可视化。在煤粉料仓下料系统上,通过线性反投影算法及图片累加技术,获得料仓出口管道截面的相对颗粒浓度分布图像和下料过程的二维流型图;对比分析了称重信号和ECT信号的时间序列曲线,并通过RSD统计方法定量描述煤粉下料的波动程度。结果表明,ECT研究与煤粉下料分区理论吻合良好,借助ECT可充分认识煤粉下料流型和气固作用特征。     

基于遗传算法的快速X射线计算机层析成像多相流测试技术(Ⅰ)测试原理和数值仿真

针对局部浓度场具有二值分布特征的特定多相流体系,提出引入多相流物理特征的快速X射线计算机层析成像（XCT）技术,基于围绕被测物有限角度的X射线投影数据,建立了改进的遗传算法（GA）求解不完整投影数据集的二值图像重构算法。通过有限角度的同时投影,实现对两相流浓度场的瞬间图像冻结和快速图像采集,既拥有XCT的高空间分辨率特征,同时满足高时间分辨率的动态测量要求,并由于投影角度数要求的大幅度缩减而降低了XCT的硬件成本。以气液两相流的多泡体系为研究对象,通过详细的数值仿真实验获得了较理想的图像重构效果,验证了GA-XCT的理论可行性。在3～24个有限角度投影数据的情况下,GA-XCT表现出明显优于传统CT图像重构算法（即滤波反投影算法）的二值图像重构能力。同时,GA-XCT具有很好的抗噪声能力,而且不依赖于气泡形状。     

电容层析成像技术在线测量气固流化床空隙率的研究

基于电容层析成像技术，提出了一种在线测量气固流化床空隙率的新方法。建立了相应的12电极电容层析成像气固流化床空隙率测量系统，可同时实现气固 流化床空隙率分布的在线显示和整体空隙率测量。选择加权反投影算法进行图像重建以保证空隙率分布显示的实时性和有效性。采用Tikhonov正则化原理和ART算法相结合的组合型新图像重建算法来实现整体空隙率的测量。Tikhonov正则化原理用于克服图像重建过程中的不适定问题，ART算法用于提高最终重建图像的质量。研究表明以上提出的空隙率测量新方法是有效的。空隙率分布在线测量的速度可达25幅／秒以上，整体空隙率测量的最大误差可小于5％。     

Numerical simulation of unsteady mass transfer by the level set method

Unsteady mass transfer to/from a single drop in the continuous phase is formulated and numerically simulated in a moving reference coordinate system by solving the motion and mass transfer equations of an accelerating drop coupled with a level set equation for capturing the interface. Numerical simulation demonstrates the evolution of mass transfer rate and average drop concentration. Numerical simulation of the flow field and the concentration field simultaneously in each time step is compared with experimental data on single drop motion and mass transfer in two typical solvent extraction systems. The numerical predictions are found in good accord with the experimental measurements. The present numerical procedure in which the flow field is solved in a coupled way with the concentration field gives more accurate prediction than the previous decoupling algorithm by the authors.     

一种新的电容层析成像电极组合激励测量模式

电容层析成像图像重建为非线性不适定反问题,其敏感场分布不均匀,可获得的测量数据有限,中心处物体的成像效果不佳。增加电极数目,可获得更多的电容测量数据,减小其不定性,同时改善敏感场分布。但同时导致电容测量值变小,测量精度下降。在保证电容测量精度的前提下,提出了24电极组合式电容层析成像传感器结构,研究了两种激励测量方案,并与传统12电极电容层析成像传感器进行了对比分析,包括电容测量值的大小及其动态测量范围、灵敏场分布的均匀性以及不同流型下的重建图像。仿真结果表明,与12电极电容层析成像传感器相比,采用24电极组合式电容层析成像传感器,其电容测量值大,可较好地保证测量精度,其灵敏度分布更加均匀,对中心处物体的成像质量明显提高。     

用于竖直油井测井的侵入式电阻层析成像图像重建(英文)

An invasive electrical resistance tomographic sensor was proposed for production logging in vertical oil well.The sensor consists of 24 electrodes that are fixed to the logging tool,which can move in the pipeline to acquire data on the conductivity distribution of oil/water mixture flow at different depths.A sensitivity-based algorithm was introduced to reconstruct the cross-sectional images.Analysis on the sensitivity of the sensor to the distribution of oil/water mixture flow was carried out to optimize the position of the imaging cross-section.The imaging results obtained using various boundary conditions at the pipe wall and the logging tool were compared.Eight typical models with various conductivity distributions were created and the measurement data were obtained by solving the forward problem of the sensor system.Image reconstruction was then implemented by using the simulation data for each model.Comparisons between the models and the reconstructed images show that the number and spatial distribution of the oil bubbles can be clearly identified.     

Integration of ECT measurements with hydrodynamic modelling of conventional gas-solid bubbling bed

The electrical capacitance tomography (ECT) provides fast images of the cross-sectional concentration distribution of solid-gas flow in a confined volume. This information can be integrated with numerical simulation to estimate some of the most important hydrodynamic quantities in solid-gas flow, such as the particles velocity, interstitial gas velocity and particle-particle contact forces.In this study, using the two-fluid approach, momentum and energy balance equations, along with the appropriate boundary conditions, have been solved by integrating the numerical procedure with the experimental data of the fluidised bed pressure drop and pixel distribution of particle concentration available from the ECT measurements. Preliminary results of time-dependent hydrodynamic features of the bed are presented. These results were analysed and assessed using the available experimental literature data on conventional bubbling fluidised bed. In general, it is demonstrated that the integration of ECT measurements with numerical modelling offers a unique and promising technique for comprehensive non-intrusive information on gas-solid flow systems.     

Effects of surface-active agents on mass transfer of a solute into single buoyancy driven drops in solvent extraction systems

Numerical simulation was made of transient mass transfer to a surfactant contaminated buoyancy-driven drop controlled by appreciable resistance in both liquid phases. For this purpose, the momentum equations were formulated and solved in a boundary-fitted orthogonal coordinate system. On the basis of resolved hydrodynamics of the contaminated drop, the transient mass transfer was formulated and solved in the same coordinate system. In order to check the applicability of the numerical scheme, single drop extraction experiments were conducted in a totally closed droplet file column with the terminal effect efficiently eliminated. The MIBK-acetic acid-water system was used with small quantities of SDS (sodium dodecyl sulphate), Triton X-100, or Tween 80 introduced into the continuous phase. For these experimental cases, the flow field and the drag coefficient of a contaminated drop were simulated first. The numerical prediction of the drag coefficient is found in good agreement with the corresponding experimental data. It illustrates that the behavior of a drop approaches that of a rigid sphere and that about 100 times higher bulk concentration of SDS than that of Triton X-100 is required for the same extent contamination of a MIBK drop of the same size. Then the information of the flow field of a contaminated MIBK drop was used in simulating the transient mass transfer of solute into the drop. The resulted extraction fraction and overall mass transfer coefficient are in reasonable coincidence with the experimental data. Both numerical results and experimental data show that overall mass transfer coefficient of a heavily contaminated drop is only about one third of that in the pure system. This can be explained well by the distribution of the local Sherwood number, which drops down abruptly along the rear stagnant surface. Also the interfacial resistance of adsorbed surfactant was incorporated in the mass transfer model and then estimated by the least square fitting the simulation with data. The numerical results also show that Tween 80 presents obvious interfacial resistance on the acetic acid diffusing across the interface, whereas SDS and Triton X-100 show no interfacial resistance. It is suggested that the numerical simulation can be resorted in some solvent extraction systems containing surfactants to conduct numerical experiments and parametric study.