异形竖板上降落液膜破裂特性

在实验研究的基础上,对表面蒸发条件下沿异形竖板的降落液膜破裂特性作了简化理论分析,得出了液膜暂时破裂临界状态与永久破裂临界状态的准数关系式,以预测液膜破裂条件.     

油滴作用下的气泡液膜破裂机理研究进展

从泡沫破裂的慢速消泡行为和快速消泡机理两大方面阐述了油滴作用下泡沫破裂的理论研究发展现状,主要包括油滴作用下泡沫破裂的阶段理论,油滴作用下泡沫液膜的破裂机理,介绍和评述了"架桥-拉伸","架桥-反润湿","铺展-流体卷吸"和"铺展-波形成"液膜破裂机理。结合泡沫在石油与天然气开采作业中诸如泡沫驱油、泡沫堵水和堵气、泡沫排液、泡沫压裂等作业过程的应用现状,指出油滴与泡沫相互作用领域今后的研究方向。     

液丝破裂过程的VOF模拟

Study on pinching liquid filament in literature was reviewed. The breakup of liquid filaments under surface tension is governed by incompressible, two-dimensional (2-D), Navier-Stokes Equations. Surface tension was expressed via a CSF (continuous surface force) model that ensures robustness and accuracy. A new surface reconstruction scheme, alternative phase integration (API) scheme was proposed to solve the kinematic equation,and was compared with other three referential schemes. A general-purpose computer program has been developed for simulating transient, 2-D, incompressible fluid flows with free surface of complex topology. The transient behavior of breaking Newtonian liquid filaments under surface tension was simulated successfully using the developed program.The initial wave growth predicted using API-VOF (volume of fluid) scheme was in good agreement with Rayleigh‘‘s linear theory and one-dimensional (l-D) long-wave theory. Both long wave theory and two-dimensional (2-D) API-VOF model on fine meshes show that as time goes on, these waves pinch off large droplets separated by smaller satellite ones that decrease in size with decreasing wavelength. Self-similar structure during the breakup was found using 1-D and 2-D models, and three breakups were predicted for a typical case. The criterion of filament breaking predicted by the 2-D model is that the wavelength is longer than the circumference of a filament. The predicted sizes of main and satellite droplets were compared with published experimental measurements.     

表面活性剂液膜体系流体力学稳定性的研究

针对液膜的破裂问题,首次提出双重膜破裂机理.根据概率和流体力学有关理论,并在液膜稳定性研究中引入界面粘度的影响,推导了破裂率的数学模型.对模型的适用性进行了检验,计算值和实验值能很好吻合.     

复合支撑液膜

本文研究了一种新型复合支撑液膜,复合膜由超薄层层,经涂复的方法附载到憎水的微孔支撑体膜复合而成。     

双层乳状液膜一次萃取的扰动与幂级数联合解——传质过程中乳状液膜破裂的作用

本文在传质过程的乳状液膜破裂作用研究中,对1982年W.S.Ho提出的反应前沿模型所忽略的乳状液膜破裂问题,进行了探讨.考虑这些因素后,用扰动与幂级数联合解法获得了分析解.并提出有效萃取时间、萃取项、破裂泄漏项等新概念.这一工作扩大了Ho模型的应用,以及能更准确地预见萃取情况.     

液膜萃取技术综述

对近年来液膜萃取技术的发展进行了综述。对乳状液膜、支撑液膜、包容液膜、大块液膜、静电式准液膜、内耦合萃反交替分离过程6大类当前研究、使用较多的液膜分离过程分别作了评述。     

撞击流气液反应器湿法脱硫的试验研究

以空气和SO2混合气体作为模拟烟气,以Ca(OH)2悬浮液作为吸收剂,在一个新型撞击流气液反应器中进行了湿法脱硫试验研究。反应器采用水平两流撞击流,喷嘴系获得专利的旋涡压力喷嘴。研究了液气流量比Vl/Vg、钙硫摩尔比rCa/rS、进口SO2浓度cS等主要参数对脱硫率的影响规律。在液气流量比Vl/Vg=0.84×10-3,撞击速度u=7m/s,进口SO2浓度cS=2 400 mg/m3条件下,脱硫效率达到了94%。     

两喷嘴对置撞击流驻点偏移规律

运用烟线法和热线风速仪对两喷嘴撞击流流场进行了实验研究,考察了不同喷嘴间距、不同气速比下撞击面的稳定性和撞击面驻点的偏移规律。结果发现,当2D≤L≤4D（L为喷嘴间距,D为喷嘴直径）时,若两喷嘴气速相等,撞击面不稳定,在轴线上发生振荡;当两喷嘴气速有小的差异时,撞击面驻点将发生大幅度的偏移,此时流场变得相对比较稳定。当2D≤L≤8D时,撞击面驻点位置对气速比变化很敏感;当L<2D和L>8D时,撞击面驻点位置对两喷嘴气速比的变化逐渐变得不敏感。     

Experimental investigation of flow regimes of axisymmetric and planar opposed jets

Dynamic behaviors of axisymmetric and planar opposed jets have been experimentally studied at 786 < Re < 6288. The flow patterns were investigated by a smoke‐wire technique, and the smoke‐wire photos were recorded by a high‐speed camera. Different flow regimes of axisymmetric and planar opposed jets have been identified. Axisymmetric opposed jets exhibit axial quasi‐periodic oscillations, stagnation point offsets, and steady states, while planar opposed jets exhibit both horizontal instabilities and deflecting oscillations. Effects of the nozzle separation and the exit Reynolds number on the dynamic characteristics of axisymmetric and planar opposed jets have been investigated and discussed. Maps of parameter spaces describing the flow regimes of axisymmetric and planar opposed jets at various nozzle separations and exit Reynolds numbers have been presented. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

基于制备超细复合含能材料的对置受限式撞击流反应器微观混合性能

由于对置受限式撞击流反应器较高的传热及混合效率,能够制备出粒径小、均匀且分布范围窄的超细颗粒。本文采用碘化物-碘酸盐平行竞争反应体系研究入射速度、结构尺寸对对置受限式撞击流反应器微观混合效果的影响规律,并将混合腔尺寸同等比例放大一倍进行对比研究。结果表明,随着入射速度的增大,离集指数减小,微观混合效果提高。喷嘴间距与喷嘴直径比的增大使得离集指数增大,微观混合效果降低。离集指数随着混合腔高度、混合腔出口尺寸的增大呈现先增大后减小的趋势,且混合腔高度对混合效果的影响较混合腔出口尺寸显著。将对置受限式撞击流反应器混合腔尺寸扩大一倍,离集指数增加到原来的2.4倍,微观混合效果显著下降,但是在较大入射速度下,两种结构的混合效果差距减小。研究结果可为纳米复合含能材料的制备提供高效、安全的技术支持。     

Gas entrainment rate and flow pattern of vertical plunging liquid jets

For a vertical plunging liquid jet system using various liquids, the effects of the operating conditions including the nozzle length-to-diameter ratio on the gas entrainment rate Q_g were evaluated experimentally. The differences in Q_g were related to the changes in the jet shape before plunging and the velocity of the plunging liquid jet at the point where the gas sheath breaks up. Empirical relationships were also presented to predict the maximum depth Z of bubbles entrained by the diffusing jet. The changes of Z were further discussed in terms of the downward liquid velocity distribution in the submerged two-phase region, which depends mainly on the size of entrained bubbles.     

平面撞击流振荡特性

对两对置平面喷嘴形成的撞击流的振荡特性进行了实验研究。采用高速摄像仪、烟线流场显示和热线测量的方法,研究了不同喷嘴间距、不同喷嘴出口气速下平面喷嘴撞击流的振荡行为。研究结果表明,平面撞击流的振荡特性主要有流向拟周期振荡和偏斜振荡两种,当L<5H时主要为流向拟周期振荡模式,当L>5H时主要为偏斜振荡模式。     

Compound liquid jets at low Reynolds numbers

Asymptotic methods based on the slenderness ratio are used to obtain the leading-order equations which govern the fluid dynamics of axisymmetric, isothermal, Newtonian, compound liquid jets such as those employed in the manufacture of textile fibres, composite fibres and optical fibres, at low Reynolds numbers. It is shown that the leading-order equations are one-dimensional, and analytical solutions are obtained for steady flows at zero Reynolds numbers, zero gravitational pull, and inertialess jets. A linear stability analysis of the viscous flow regime indicates that the stability of compound jets is governed by the same eigenvalue equation as that for the spinning of round fibres and annular jets. Numerical studies of the time-dependent equations subject to axial velocity perturbations at either the nozzle exit or the take-up point, or both, indicate that the compound jet dynamics evolves from periodic to chaotic motions as the extension or draw ratio is increased. The power spectrum of the inner (round) jet's radius at the take-up point broadens and the phase diagrams exhibit holes at large draw ratios. The number of holes increases as the draw ratio is increased, thus indicating chaotic behaviour. It is also shown that the nonlinear dynamics of bicomponent, compound jets is analogous to that of single-component, annular jets.     

不同工作因数下方波冲击射流的换热特性

应用数值模拟方法研究了不同工作因数下方波冲击射流的换热及流动特性,并分析了冲击靶面换热特性的变化规律。研究了冲击靶面换热特性随Reynolds数、脉冲频率、喷嘴距冲击靶面距离与喷嘴直径之比等参数的变化规律,重点分析了不同工作因数对冲击射流滞止区域换热与流动特性的影响,并将数值计算结果与连续冲击射流、脉动冲击射流实验结果进行对比验证。计算结果表明:当工作因数为0.5与0.7时,冲击靶面滞止区域Nusselt数非常接近;当工作因数为0.5时,壁面射流区域Nusselt数比工作因数为0.7时提高了10%;工作因数为0.9时,冲击靶面Nusselt数比连续冲击射流提高3%;工作因数为0.7时,相对于工作因数为0.5、0.9及连续冲击射流时,冲击靶面滞止区域存在强烈的涡结构变化。     

Experimental study of oscillation behaviors in confined impinging jets reactor under excitation

Dynamic behaviors in a three‐dimensional confined impinging jets reactor (CIJR) under excitation were experimentally studied by a flow visualization technique at 75 ≤ Re ≤ 150. The effects of inlet Reynolds numbers (Re), excitation frequencies and excitation amplitudes on the oscillation behaviors in CIJR have been investigated by a particle image velocimetry (PIV) and a high‐speed camera. Results indicate that the excitation in the inflow of the opposed jets can induce periodic oscillation of the impingement plane along the axis, whose oscillation frequency is equal to the excitation frequency. At Re ≤ 100, the induced axial oscillation can further cause a deflective oscillation with a frequency nearly equal to the excitation, and the scale of the vortex in the impingement plane is well regulated by the excitation frequency. At Re = 150, the excitation of amplitude less than 20% has insignificant effect on the deflective oscillation existing in CIJR. A semiempirical formula has been proposed to predict the oscillation amplitude of the impingement plane in CIJR under excitation. © 2014 American Institute of Chemical Engineers AIChE J, 61: 333–341, 2015     

平面气固撞击流周期振荡的模拟分析

由于喷嘴截面的高宽比远小于1,平面狭缝喷嘴撞击流可看作二维撞击流。采用欧拉双流体模型对二维气固撞击流进行数值模拟。模拟结果表明,当固相负载率m≤8.2,颗粒粒径为60 μm≤d_p≤175 μm时,大间距的平面气固撞击流也出现了周期振荡。通过分析射流轴线上不同位置的压力和速度的瞬时值和平均值,认为周期振荡是由于撞击面上压力释放和持续射流的共同作用导致。讨论了不同条件对振荡周期的影响:振荡周期随喷嘴间距或颗粒粒径的增加而增加;而随射流Reynolds数的增加或者固相负载率的增加而减小。