气液界面摩擦因子对分层流向段塞流过渡的影响

根据气液两相流段塞稳定性理论,结合分层流理想化模型,对直径2.54 cm水平管内空气-水两相流出现段塞流时的各相临界表观速度和临界液层高度进行了理论预测,并且分析了气液两相界面的摩擦因子对于预测流型转变的影响.由于在不同的气相流速范围内,段塞流由不同形式的界面波形成,当气相表观速度小于 4 m(s(1时,由大振幅波形成段塞流,而当气相表观速度大于 4 m(s(1,段塞流由小波长的滚动波合并而成,因而根据实测数据对界面摩擦因子的计算进行了补充修正,并且应用到对应的气相流速范围.基于所给出的计算方法解得发生分层流向段塞流转变的临界表观速度和临界液层高度,并和实验数据进行了比较. 结果表明所做的修正可以避免以往理论预测中出现的低估情况,求得的各临界特征参数值和实验结果吻合得较好.     

Y形气-液顶吹喷枪流型及两相流混合特性实验

贫化电炉气液顶吹喷枪是一种独特的垂直下降管,其一端Y形通入气液两相,一端直接通入熔池中进行喷吹作业。本文采用多相流水模型模拟仿真的实验手段进行了定量分析,结果表明：不同于传统的垂直下降管,这种顶吹喷枪的管内流型受气液相间压差的影响,产生了一种由环状流过渡为泡状流的流型,不同流型的分布区域与压差的大小有关并且稳定存在;在支管与主管的交叉区域,对于不同的气液比存在3种气液混合相分界面,并各自产生不同的流型;浸没式顶吹气泡群形态在不同的管内流型驱动下有较大差异,表现在深度及宽度两个方面,并证明了气液比为2～5间的生产效果是最佳的。     

油气水三相段塞流与滚动波流型的转变

Compared with gas-liquid two-phase flow,oil-gas-water three-phase flow is much more complex. There is immiscible oil-water,whose interaction and dispersion greatly affects the flow characteristics. The slug flow pattern of oil-gas-water three-phase and its flow pattern transition were studied in a 95 m long,51 mm i. d. horizontal pipe. The oil-gas-water three-phase slug flow pattern could be classified into five sub-flow patterns. The slug flow was W/O or O/W one during its transition to roll wave,which was three-layer flow pattern without mixed-phase on the interface. An even larger superficial gas velocity was needed for the transition boundary of slug flow and roll wave flow when the superficial liquid velocity is large. Besides,the region of roll wave flow pattern became smaller. The above-mentioned transition only happened when the water cut of liquid was between 30% and 70%. At the same superficial liquid velocity,there appeared a minimum superficial gas velocity corresponding to the transition of flow pattern when the water cut of liquid was between 40% and 50%.     

垂直管气液两相环状流界面扰动波频率特性

气液两相环状流的相界面存在扰动波,波动频率是描述环状流界面扰动波特性的关键参数,对环状流的传质传热研究有重要参考价值。利用近红外光的吸收特性,设计了液膜检测装置,采用垂直对射光路设计,并通过置入式导光管屏蔽一侧液膜和气芯夹带液滴,实现了对环状流局部液膜的非接触式检测。在此基础上对界面扰动波进行了频域分析,运用功率谱密度估计,对50 mm管径竖直上升管环状流界面扰动波波动频率进行了定量研究,得到0.1～0.8 MPa不同压强条件下,共70个流动条件的环状流界面扰动波频率值。利用实验结果对现有模型进行验证分析,在此基础上利用Strouhal数描述液相流动条件的影响,利用Froude数描述气相流动条件的影响,建立了预测环状流界面扰动波波动频率的St-Fr模型,经实验数据验证预测的平均绝对误差（MAE）为11.42%。     

Counter‐current gas‐liquid wavy film flow between the vertical plates analyzed using the Navier‐Stokes equations

The article is devoted to a theoretical analysis of counter‐current gas‐liquid wavy film flow between vertical plates. We consider two‐dimensional nonlinear waves on the interface over a wide variation of parameters. The main interest is to analyse the wave structure at the parameter values corresponding to the onset of flooding observed in experiments. We use the Navier‐Stokes equations in their full statement to describe the liquid phase hydrodynamics. For the gas phase equations, we use two models: (1) the Navier‐Stokes system and (2) the simplified Benjamin‐Miles approach where the liquid phase is a small disturbance for the laminar or turbulent gas flow. With the superficial gas velocity increasing and starting from some value of the velocity, the waves demonstrate a rapid decreasing of both the minimal film thickness and the phase wave velocity. We obtain a region of the gas velocity where we have two solutions at one set of the problem parameters and where the flooding takes place. Both the phase wave velocity and the minimal film thickness are positive numbers at such values of the velocity. We calculate the flooding point dependences on the liquid Reynolds number for two different liquids. The wave regime corresponding to the flooding point demonstrates negative u‐velocities in the neighbourhood of the interface near the film thickness maximum. At smaller values of the superficial gas velocity, the negative u‐velocities take place in the neighbourhood of the film thickness minimum. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Detection and analysis of transition from annular to intermittent flow in vertical tubes

In vertical co-current gas-liquid flow, the transition from annular to intermittent flow occurs when gas core becomes interrupted by liquid bridges due to the instability of the interfacial capillary waves. An analytical model is formulated to explain the liquid bridging in terms of the growth of finite amplitude interfacial capillary waves. Experimental results show that the longest wave length, which is associated with the transition, is about eight times the wave length of waves moving with the velocity of the liquid film.     

湿气管道积液临界气速预测的新模型

气田开发经常采用湿气集输方案。针对湿气输送管道出现的积液问题，基于分层流最小界面剪切应力准则，利用气液平界面分层流液膜区的速度分布规律，建立了求解积液临界气速的新机理模型。由分层流液膜区的流场描述和气相动量方程得到气液界面剪切应力的表达式；利用界面剪切应力函数曲线特性，可以通过界面剪切应力关于持液率求导获得临界气速。以不同文献中收集的临界气速实验数据，对新模型和其他具有代表性的湿气管道积液模型进行验证对比，表明新模型的预测精度要优于其他模型。     

Interfacial Friction Factor Prediction in Vertical Annular Flow Based on the Interface Roughness

Correlations for the interface roughness are proposed for conditions without or with disturbance waves for vertical annular flow. The decisive role of interface roughness in the interfacial friction factor is specified through a comparison of ten correlations for the interfacial friction factor with an experimental database. The effect of the disturbance wave on the interface roughness is analyzed to figure out the influence parameters, which are the superficial gas and liquid Reynolds numbers for conditions without disturbance waves and gas core and liquid film Reynolds numbers for conditions with disturbance waves. The proposed correlations improve the prediction precision of the interfacial friction factor, especially in smooth and transitional regimes.     

PREDICTION OF FLOW REGIME TRANSITIONS IN VERTICAL UPWARD THREE PHASE GAS-LIQUID-SOLID FLOW

The effect of solids concentration on the bubble to bubble-slug, bubble-slug to slug, and slug to churn flow transitions in gas-liquid-solid vertical flow has been studied using air, water, and glass beads in a 5 cm ID plexiglass column. Several simple models to predict the transitions were developed utilizing criteria proposed for gas-liquid vertical flow. These criteria are shown to apply equally well in the absence or presence of the solid phase

With solids present in the flow, the bubble to bubble-slug and bubble-slug to slug flow transitions both occurred at lower superficial gas velocities because of increased bubble coalescence. However, the slug to churn flow transition was unaffected by solids in the range of flow conditions studied.     

湿天然气在上倾管道的气液两相流动特性研究

利用VOF (Volume of Fluid)模型模拟了湿天然气在上倾管道的气液两相流动特性。讨论了管道内气体入口流速对气液两相流动特性的影响。结果表明,当管道内气体入口流速较低时,由于气液界面的切应力小于液相在上倾段的重力分力,因此气体无法将液体携带至管道上倾段。随着气速的增加,气液界面的切应力逐渐增大,气液界面开始出现波纹,气体逐渐将液体携带并完全平铺于管道上倾段。     

倾斜圆管内气液两相分层流界面的稳定性分析

<正>l 弓l言 气液两相流分层流界面波特性及界面稳定性分析对理论和应用具有重要意义.50年代,Banjamin”’、Miles”’和 Hanratty’‘’“开始了此方面的研究.以往研究中,均采用 Jeffreys”’的方法,即利用液相动量方程的积分形式,气相的影响只作为液相动量方程的边界条件.另外也有研究者从N-S方程出发,通过对实际问题的适当简化以研究界面稳定性”‘. 本文利用双流体模型研究了倾斜圆管内气液两相分层流的界面稳定性,系统研究了管道几何条件及流动状况对稳定性的影响.2 数学模型 对如图1所示的倾斜管内分层流,假定两相间不存在热量传递和相变过程,其一维双流体流动模型为”-“ ～r 入八人）乃t十别八U。人）/肚一0（I） ltw 8（pkA。U。）/9 t + 3（pkA。厂。ZtZ）/sx 、_/.\—一,。J。士。/;+八。A。slip J>>一二卜 卜。二.t 一洪人八）/gx+AdA/a工（2） 一人二二>二v抑Q厂二厂了 式（1）、式（2）中k—l或g,当k—g时,取 pry——“一”号,k—l时贩“十”号.素流速度分布均 匀,厂。一 l“’‘;层流根据液膜内速度分布可知, 图 1 分层流示意图——”———一’—””—””——～ 八一4/3““二 气液两相静压项用文献〔幻的方 F。Ic0d屯＊r＊donof盯r＊1m叨n0w”‘’-’“‘一‘””—’““——一‘一     

基于气泡群相间作用力模型的加压鼓泡塔流体力学模拟

目前,多数文献报道了冷态加压湍动鼓泡塔内流动特征,并且通过实验数据回归相关经验关联式。然而,此类关联式适用范围有限,难以直接外推到工业鼓泡塔反应器条件。因此,在FLUENT平台上建立了基于气泡群相间作用力的、动态二维加压鼓泡塔计算流体力学模型。通过数值模拟考察了操作压力为0.5~2.0 MPa,表观气速为0.20~0.31 m·s^-1,内径0.3 m鼓泡塔内流场特性参数分布,并且与冷态实验数据进行比较。结果表明,采用修正后的气泡群曳力模型、径向力平衡模型以及壁面润滑力模型描述气泡群相间作用力,能够较为准确地反映平均气含率和气含率径向分布随操作压力和表观气速变化的规律。     

预测水平管气-液环状流周向液膜厚度分布的理论模型

针对水平环状流液膜厚度沿周向分布的不对称性 ,用 5组双平行电导探针测量了水平管内气液环状流沿周向的瞬态液膜厚度 ,得到了平均液膜厚度沿周向的分布规律 .分析了液膜向上输送的机理 .为更为准确地预测液膜厚度 ,综合考虑了扰动波抽吸作用机理、气体二次流机理及液滴沉降和携带机理 ;通过量级比较和应力平衡的方法 ,提出了一个预测液膜厚度沿周向分布的理论模型 .数值模拟结果表明预测值与实验测量结果符合较好     

垂直管内气液两相弹状流含气率研究

In order to investigate the influence of the entrance effect on the spatial distribution of phases, the experiments on gas-liquid two-phase slug flow in a vertical pipe of 0.03m ID were carried out by using optical probes and an EKTAPRO 1000 high speed motion analyzer. It demonstrates that the radial profile of slug flow void fraction is parabolic. Influenced by the falling liquid film, the radial profile curve of liquid slug void fraction in the wake region is also parabolic. Since fully turbulent velocity distribution is built up in the developed region,the void fraction profile in this region is the saddle type. At given superficial liquid velocity, the liquid slug void fraction increases with gas velocity. The radial profiles of liquid slug void fraction at different axial locations are all saddle curves, but void fraction is obviously high around the centerline in the entrance region. The nearer the measuring station is from the entrance, the farther the peak location is away from the wall.     

垂直同心环形管内上升气液团状流向环状流的转换

对垂直同心环形管内上升气液团状流向环状流的转换进行了研究 .根据团状流及环状流的流动特性 ,并考虑同心环形管的结构特征 ,建立了垂直同心环形管上升气液团状流向环状流转换的新的理论模型 .通过本文的实验数据及其他研究者的实验数据对该模型的预测性能进行了检验 ,并与其他研究者的模型进行了比较 .结果表明本文的转换模型预测性能较好     

INTERFACIAL INTERACTIONS AND SECONDARY FLOWS IN STRATIFIED TWO-PHASE FLOW

In this paper are analysed the interactions between a surface wave field and the kinematic structures above and below the waves, in gas-liquid stratified flow in a rectangular cross sectional channel. The analysis is based on experimental data both on the local structure of the flows and on the deformation of the gas-liquid surface. The basic phenomena that have been observed are: on the one hand, the waves that propagates over the liquid surface can exhibit a crosswise distribution of amplitude; on the other hand, secondary flows can be generated both in the gas and in the liquid. A theoretical attempt is developed to explain the distribution to wave amplitude: in fact, the waves propagate over a non uniform liquid current. On the one hand, the wave field interact with the liquid current to generate secondary flows below the waves. On the other hand, the wave amplitude distribution interacts with the gas flow; the wave distribution can be considered as a non uniform interfacial roughness which generates Prandtl second type secondary flows above the waves. These physical mechanisms which are based on the analysis of experimental results are also validated with numerical simulations.     

垂直同心环空管内上升弹状流向团状流的转换

对垂直同心环形管内上升气液弹状流向团状流的转换进行了一定的研究。根据弹状流及团状流的流动特性 ,并考虑同心环形管的结构特征 ,建立了垂直同心环形管上升气液团状流向环状流转换的新的理论模型。通过文中的实验数据及其他研究者的实验数据对该模型的预测性能进行了检验 ,并与其他研究者的模型进行了比较 ,最后还对环形管结构参数对转换的影响进行了一定的分析。     

洗涤冷却室气液两相流的模拟及结构优化

洗涤冷却室是激冷式煤气化炉的重要组成部分,对气化室内生成的高温合成气进行降温及洗涤。目前的洗涤冷却室在工业上依然存在诸多问题,如液位及压力波动较大、装置运行不稳定、洗涤效率不够高等,需要对其结构进行优化改进。采用三维欧拉-欧拉模型对三种不同结构的洗涤冷却室进行了CFD模拟。三种洗涤冷却室的结构分别为无内构件、含有支管内构件及新型耦合支管与导流筒内构件。与文献实验数据的对比表明,模型能较准确地预测洗涤冷却室内的气含率分布。支管的加入分流了部分气量,使部分气体能够从鼓泡区域中心上升,促进了气体的径向扩散,有助于维持装置的稳定运行;而导流筒内构件的加入增大了支管气体分流的比例,提升了洗涤冷却室液面下的全局气含率,增强了气液回流,从而进一步强化洗涤效果。     

IMPROVED HYDRODYNAMIC MODEL OF TWO-PHASE SLUG FLOW IN VERTICAL TUBES

Merits of the Fernandes model(Fernandes et al.1983)for two-phase slug flow in verticaltubes are reviewed in this paper.While predicting many macroscopic parameters of slug flow in verti-cal tubes,it fails to present correctly the trend that the average voidage in liquid slugs increases asthe rising velocity of Taylor bubbles is increased.It is also desirable to extend its application toelectrolyte systems, and to churn flow conditions.Based on the diagnostic analysis,the model equa-tion for gas entrainment by falling liquid film is reformulated and the influence of surface tension isalso accounted for.Development of the falling liquid film is recognized in the revised model in or-der to suit the case of short Taylor bubbles as well.The modified model predicts the variation of av-erage voidage in liquid slugs in good agreement with available experimental data.