单个运动气泡近界面浓度场的研究

对单个气泡传质的近界面浓度场影响因素进行了实验和理论研究．实时激光全息干涉法测量结果表明,运动气泡近界面浓度是一个定态值,受流速、泡径、温度等因素影响显著;假设该传质过程达到局部平衡,进行热力学分析,得到的结论与实验结果一致．在实验测量结果的基础上,对单个O_2气泡在乙醇中吸收时的传质近界面浓度场进行了数值模拟,取得了良好的结果．     

运动气泡近界面湍流场的激光测量及其湍流结构特性

运用二维激光多普勒测速仪,测定了运动气泡近界面的动力学特性,其中包括时均特性及湍流场结构.实验表明,尾涡区的时均流速呈非均匀分布,湍流场由双结构组成,即由完全随机的湍流涡及规律性的相干涡构成,这种双结构现象在尾涡的中心及边缘部又有所变化,其相关函数、谱密度函数及统计尺度亦随不同的部位而变化.泡前区受尾涡区周期性Karman涡脱落的影响,呈现相同频率的周期波动.这种特性存在于切向及法向速度中.     

PDMS—环己烷体系中起泡脱挥气泡场全息记录与再现

ＰＤＭＳ－环己烷体系中起泡脱挥气泡场全息记录与再现鲁阳谢建军潘勤敏潘祖仁（浙江大学力学系,杭州３１００２７）（浙江大学高分子科学与工程研究所）关键词起泡脱挥气泡场象平面全息１前言化学工程中多相流粒子场（气泡、液滴、固体粒子）特性研究多采用普通摄影或...     

环已烷／PDMS体系起泡脱挥中气泡场的激光全息研究

在介绍环已烷／ＰＫＭＳ体系中起泡脱挥气泡场的激光全息图记录与再现的基础上,对其全息图通过计算机进行了ＶＰＰＳＡ颗粒开头分析和数据处理。讨论了液体高度、操作真空度和环已烷初始浓度对数均气泡直径的影响。实验结果表明,数均气泡直径随液体高度增加而增加,随操作真空度和环已烷初始浓度的增加而稍增大,液体高度是其主要影响因素。同时,对测量误差的影响因素也进行了讨论。     

气泡传质过程近界面非稳态特性及热力学研究

利用实时显微激光全息干涉测试技术 ,对运动气泡传质过程近界面的非稳态特性及浓度分布进行了实验测定 ,讨论了近界面湍动性质、稳态性质、非平衡性质及其关系 ,考察了流速、泡径、温度等因素对气泡传质过程的影响     

运动气泡近界面浓度场的激光测量及其传质特性的研究

<正>1引言迄今为止,有关两相流气泡的传质研究已有大量报道[1-4]。这些研究均是一种黑箱式的研究方法,着眼于宏观现象的观测、分析及回归,无法从机理上展示各种宏观传递现象的差异及其内在本质,固而其研究结果均带有很大的经验性和局限性。 随着化学工程基础理论研究的深入发展,需要进一步了解运动气泡逼近界面处浓度场的变化与分布。特别是由于运动气泡的特殊性,气泡在上升过程中要发生变形[5],形成泡前区及尾涡区,在这两个区域内,界面阳近动力学特性及浓度场特性有很大差异,这就需要在更深的层次上研究这种微观差异。     

基于浓度/速度场测量的吸收过程液相传质系数

针对矩形流道内气、液流体的并流吸收传质过程,分别应用实时激光全息干涉术和激光多普勒速度仪对不同气、液流速下液相内近界面浓度分布与速度分布进行了实验观测.结果表明,边界层内浓度分布呈指数下降,流速越大梯度越陡,且速度边界层厚度要大于浓度边界层厚度.建立了通过物料衡算求算液相传质系数的方法.得到了不同条件下平均液相传质系数,并与Whiteman’s双膜理论的计算结果进行了比较.     

激光全息技术测定聚合物系脱挥中气泡场的若干问题

探讨了在聚合物系脱挥过程中获得高质量的三维气泡全息图的几种途径和折射率的变化率，分析了实验装置与光路设计、全息图的衍射效率和分辨率对提高全息图质量的影响，推导了最佳衍射效率的计算公式。     

浆料系统内上升气泡周围微细颗粒浓度分布和附着效率的理论研究

Quantitative prediction of distribution function and adhesion efficiency of particles around a rising bubble in slurry systems is presented in this work. By solving the convection-diffusion equation (Fokker-Planck equation), the influence of Brownian diffusivity of fine particles on concentration distribution and adhesion efficiency is demonstrated with the hydrodynamic force and van der Waals attractive potential between particles and bubble considered. It is found that two kinds of mechanism dominate the adhesion process of particles on bubble according to different Peclet number or size of particles and bubble, as well as other properties of the slurry systems. In addition, the viscosity ratio of bubble to the suspending fluid was found to have obvious influence on particle adhesion.     

超声波溶液浓度在线检测中气泡影响的消除方法

通过测量超声波速度可以估算溶液的浓度。在化工生产液中时常会出现大量的气泡,为了避免气泡对测量的影响,借助微机技术同时测量声速及声衰减,以此判断测量是否受到了气泡的影响且只保留正确的数据用于计算溶液浓度。这样,制成的仪器工作性能十分稳定,可以用于在线分析。     

PIV用于板坯连铸结晶器流场的实验研究

将粒子图像测速技术应用于板坯连铸结晶器内流场研究.结合1550mm×160 mm板坯结晶器内腔尺寸,采用1:0.5水模型进行实验,研究了拉速、浸入深度、水口倾角等参数对结晶器流场的影响.结果表明,结晶器液面波动、流股对结晶器窄面的冲击及同流区涡心位置与以上3种参数直接相关.随着拉速增加,结晶器内的流速随之增大,液面波动明显,上下部回流区延伸范围增加,涡心位置下移:采用较大的水口浸入深度和水口倾角,射流在结晶器窄面的冲击位置下移,可以有效稳定液面,避免卷渣.     

PIV在化工搅拌釜内流动测量中的应用

着重探讨了新一代全场光学测速技术——粒子图像速度场仪(PIV)在搅拌混合实验中的应用,指出PIV及其衍生的测速技术在搅拌混合实验研究中具有广泛应用前景。PIV流场测量结果兼具很高的空间分辨率和时间解析度,可以得到搅拌釜中混合流体的瞬时2D或3D速度场以及浓度场等信息,进行非定常湍流特性研究,有助于建立搅拌釜内多相流动模型,揭示搅拌混合作用机理,优化搅拌桨型设计,促进搅拌混合技术的进一步发展。     

Flow around individual Taylor bubbles rising in stagnant CMC solutions: PIV measurements

The flow around single Taylor bubbles rising in non-Newtonian solutions of Carboxymethylcellulose (CMC) polymer was studied using simultaneously particle image velocimetry (PIV) and shadowgraphy. This technique made it possible to determine the correct position of the bubble interface. Solutions of polymer with weight percentage varying from 0.1 to 1.0 wt% were used to cover a wide range of flow regimes. The rheological fluid properties and pipe dimension yielded Reynolds numbers between 4 and 714 and Deborah numbers for the higher concentration solutions between 0.001 and 0.236. The shape of the bubbles rising in the different solutions was compared. The flow around the nose of the bubbles was found to be similar in all the studied conditions. Velocity profiles in the liquid film around the bubble were measured and different wake structures were found. With increasing solution viscosity, the wake flow pattern varied from turbulent to laminar, and a negative wake was observed for the higher polymer concentration solutions.     

圆柱绕流的数值模拟与PIV测试研究

利用计算流体力学软件Fluent对均匀来流绕固定圆柱的流动情况进行了数值模拟,考察和研究了气流绕过圆柱时的边界层的形成以及旋涡的形成及脱落过程,利用粒子图像测试(PIV)技术对绕流情况进行了实验研究.通过数值模拟结果与PIV实验结果的定性和定量分析比较,证明Fluent软件的模拟结果具有相当的准确性,能够准确的预测流体的流动特性.     

非牛顿流体中的两并行运动气泡周围流场及气泡间相互作用的PIV研究

The flow fields surrounding two parallel moving bubbles rising from two identical orifices submerged in non-Newtonian fluid of carboxymethylcellulose (CMC) solution of three different mass concentration were measured experimentally by the use of particle image velocimetry (PIV). The influences of gas flowrate, solution mass concentration, orifice interval and the angle between two bubble centers line and vertical direction on the flow field surrounding bubbles were discussed respectively by analyzing the velocity vector, velocity contours as well as individual velocity components. The results show that the liquid velocity both in front of two bubbles and behind increases with gas flowrate duo to shear-thinning effect of previous bubbles, whereas decreases with the increase of CMC concentration due to the increase of drag force acting on bubbles. The effect of the orifice interval on the flow field around two moving bubbles becomes gradually obvious as the interval becomes closer. Moreover, two adjacent side-by-side bubbles repulse each other during rising, leading to the practical interval between them increased somewhat above the orifice interval. When the distance between bubbles is less than the orifice interval l0 mm, the interaction between two neighboring bubbles changed from mutual repellence to attraction with the decrease of the angle of the line of linking two bubble centers to the vertical direction.     

Velocity Field Structure and Flocculation Efficiency in Taylor-Couette Flow

Velocity field data were acquired for Taylor-Couette flow in the annulus gap between a rotating inner cylinder and a fixed concentric outer cylinder by using particle image velocimetry. The flocculation efficiencies were also obtained in the same Taylor-Couette flow under the conditions corresponding to the velocity field measurement. The flocculation efficiencies reached the maximum values due to the closed vortices, their contraction and expansion with time in wavy vortex flow. But out of the wavy vortex flow range, the comparatively low flocculation efficiencies were obtained due to the no-closed vortices which connected with each other.     

PIV测量用模型泵的水力设计及性能分析

为了研究离心泵内部流动情况,参考IS80-50-315型离心泵,设计了一台PIV测量用有机玻璃模型泵,并对该泵的可拍摄性和水力性能进行了分析。介绍了模型泵、片光和CCD相机的布置及其流场拍摄方法。结果表明,该泵适用于PIV拍摄,且水力性能满足实验要求。     

Study of bubble induced flow structure using PIV

An experimental investigation of the flow structure induced by a chain of gas bubbles was carried out in a rectangular bubble column using particle image velocimetry (PIV). It is observed that the bubble rising trajectory changes from one dimension to three dimension as liquid viscosity reduces. The variation of bubble rising trajectory associates with the alternation of bubble motions—with or without oscillatory and rotational motion depending the bubble rising trajectory is 3-D or 1-D. The different behaviors of gas bubbles introduce various instantaneous and averaged liquid flow structures. In general, complex fluid velocity fields present in liquid system of low viscosity where free vortex, cross flow, and irregular circular flow can be observed. The liquid pseudo-turbulence measured in terms of turbulence intensity and Reynolds stress is more intense in liquid of low viscosity. The turbulence is also enhanced by the frequency of bubble formation.     

挡板式泡沫发生器内部流场分析

泡沫发生器是产生泡沫流体的设备,其发泡的基本原理是将空气引入发泡剂溶液中。应用数值模拟与PIV实验相结合,研究不同挡板角度对泡沫发生器内部气液两相流流动影响规律。该研究为疏松砂岩油藏冲砂洗井作业提供指导,为后续泡沫发生器结构设计提供理论依据。