垂直管中管径突变对空气-水两相流流型的影响(Ⅱ)突扩接头

In this companion paper, flow patterns in the upstream and downstream tubes of a sudden-expansion cross-section (SECS) in a vertical straight pipe were presented. The effect of SECS on flow patterns upstream and downstream was analyzed by comparing with flow patterns in uniform cross-section vertical tubes. It is found the effect is great. There exist great instabilities of two-phase flow in the neighboring areas of the SECS both downstream and upstream.     

水平长直管内油水两相流流动特性实验研究

The flow patterns and their transitions of oil-water two-phase flow in horizontal pipes were studied. The experiments were conducted in two kinds of horizontal tubes, made of plexiglas pipe and stainless steel pipe with 40 mm ID respectively. No. 46 mechanical oil and tap water were used as working fluids. The superflcial velocity ranges of oil and water were: 0.04-1.2m·s-1 and 0.04-2.2m·s-1, respectively. The flow patterns were identified by visualization and by transient fluctuation signals of differential pressure drop. The flow patterns were defined according to the relative distribution of oil and water phases in the pipes. Flow pattern maps were obtained for both pipelines. In addition, semi-theoretical transition criteria for the flow patterns were proposed, and the proposed transitional criteria are in reasonable agreement with available data in liquid-liquid systems.     

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%.     

利用符号时间序列分析法表征垂直上升管中油水两相流流型

The flow patterns of oil/water two-phase flow in vertical upward pipes were characterized by the analysis of symbolic time series based on the conductance fluctuating signals. The study showed that the symbolic sequence temporal irreversibility Tfb and chi-square χfb^2 statistics had little change with oil-in-water flow pattern variations for water cut (Kw) ranging from 61% to 91% but showed irregular sudden changes with transitional flow pattern variations for water cut 51%. When distinguishing the transitional flow pattern from oil-in-water flow pattern, the symbolic time series analysis method presented more unique characteristics and was a useful assistant diagnostic tool for the identification of oil/water two- phase flow patterns.     

A CRITERION FOR TRANSITION FROM BUBBLING TO TURBULENT FLUIDIZATION

Investigations of the transition from bubbling to turbulent fluidization were conducted in a gas-solid fluidized bed using on-line computer analysis of pressure fluctuation. In order to study the effects of density and size of the particles as well as bed geometry on the transition, a series of experiments were performed. A correlation was obtained for the flow pattern transition velocity, U_C. Besides, it has been found that the Geldart's classification of particles also predicts flow pattern transition.     

垂直上升管内有水平柱体时气液两相局部流型转变的研究

1 INTRODUCTION Gas-liquid two-phase cross flow and heat transfer exists in oil production and chemical facilities. With the rapid development of the technology of modern industry, the gas-liquid two-phase flow across a rod and heat transfer characteristics are studied more ex- tensively, and its thorough understanding is of great importance to the design and operation of processing equipment. Flow pattern and its transition are important in the study of multiphase flow. Because of the com…     

Solid concentration and velocity distributions in an annulus turbulent fluidized bed

Solid concentration and particle velocity distributions in the transition section of a?200 mm turbulent fluidized bed (TFB) and a?200 mm annulus turbulent fluidized bed (A-TFB) with a?50 mm central standpipe were mea-sured using a PV6D optical probe. It is concluded that in turbulent regime, the axial distribution of solid concen-tration in A-TFB was similar to that in TFB, but the former had a shorter transition section. The axial solid concentration distribution, probability density, and power spectral distributions revealed that the standpipe hin-dered the turbulence of gas–solid two-phase flow at a low superficial gas velocity. Consequently, the bottom flow of A-TFB approached the bubbling fluidization pattern. By contrast, the standpipe facilitated the turbulence at a high superficial gas velocity, thus making the bottom flow of A-TFB approach the fast fluidization pattern. Both the particle velocity and solid concentration distribution presented a unimodal distribution in A-TFB and TFB. However, the standpipe at a high gas velocity and in the transition or dilute phase section significantly affected the radial distribution of flow parameters, presenting a bimodal distribution with particle concentration higher near the internal and external wal s and in downward flow. Conversely, particle concentration in the middle an-nulus area was lower, and particles flowed upward. This result indicated that the standpipe destroyed the core-annular structure of TFB in the transition and dilute phase sections at a high gas velocity and also improved the particle distribution of TFB. In conclusion, the standpipe improved the fluidization quality and flow homogeneity at high gas velocity and in the transition or dilute phase section, but caused opposite phenomena at low gas ve-locity and in the dense-phase section.     

An experimental investigation on the interfacial waves in air-water two-phase flow within horizontal pipelines

By using two-parallel conductance probes,the instantaneous film thickness of gas-liquidtwo-phase flow within a horizontal plexiglass pipe of 50mm inner diameter was experimentallymeasured.The pipe was 6680mm long.Several wave patterns were distinguished through statisticalanalysis of signals of film thicknesses.Wave pattern maps were obtained and compared with resultsof former studies.The characteristics of the interfacial waves,such as time-averaged film thickness,wave height,wave propagation speed,wavelength and wave frequency,were systematically investigated.The effect of the exit structure of the test section on interfacial waves was experimentally examined.     

Investigating the flow characteristics of air-lift pumps operating in gas-liquid two-phase flow

Experiments were conducted to investigate the flow characteristics in the riser pipe and the suction pipe of airlift pump at a series of air flow rates and submergence ratios by using a high speed camcorder and a Laser Doppler Velocimetry system(LDV). A modified model was developed to predict the performance of airlift pump operating in gas-liquid two-phase flow. The results show that an unstable flow structure composed by a water falling film,a bubbly mixture, a water ascending film appearing alternately in riser pipe dominates the performance of airlift pump at large air flow rates. The bubbly mixture with a strongest capacity for pumping water first increases to its maximum and then slightly decreases. In suction pipe, the average velocity shows a flat profile and increases with increasing submergence ratio. Moreover, the predicted results of modified model are in good agreement with the experimental data in a margin of ± 12%.     

基于声发射技术的垂直管气液两相流动检测方法

声发射（AE）作为一种无损检测手段,用于气液两相流的测量具有非侵入式、测量不破坏被测管道及流场分布,信号强、灵敏度高等优点。利用声发射技术在河北大学垂直管气液两相流管道上进行了大量实验,运用现代信息数据处理方法对气液两相流垂直管道流型特征参数进行了提取。分析结果表明利用声发射手段提取出的流型特征参数可以反映出典型流型下的动力学特征。垂直管道中,泡状流、弹状流、环状流以及过渡状态下的乳沫状流在时域和频域信号中有着明显区别,小波能量和小波包分解后的信息熵的值也存在较大的差异性,从另一角度验证了在不同流型下两相流体在管道内部不同的运动状态,利用模式识别的思想,对垂直管4种典型流型进行了流型识别,取得了较好的效果,研究结果表明声发射技术可以作为一种技术手段用于气液两相流流动的检测。     

水平管内油水两相流流型转换特性

以高黏度的油和水为工质,在内径为25.7 mm,长52 m的水平不锈钢油水两相流实验环道内对油水两相流流型及其转换特性进行了实验研究.根据实验结果定义了不同流动条件下出现的流型,绘制了流型图.对影响油水两相管流流型转换的各种因素进行了综合分析,利用量纲分析的方法得出了流型转换的准则关系式,并提出了一个较为准确的有关油水两相管流中反相临界含水率的计算相关式.     

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。     

The Effect of Sudden Change in Pipe Diameter on Flow Patterns of Air-Water Two-Phase Flow in Vertical Pipe (Ⅱ) Sudden-Expansion Cross-Section

In this companion paper, flow patterns in the upstream and downstream tubes of a sudden-expansion cross-section (SECS) in a vertical straight pipe were presented. The effect of SECS on flow patterns upstream and downstream was analyzed by comparing with flow patterns in uniform cross-section vertical tubes. It is found the effect is great. There exist great instabilities of two-phase flow in the neighboring areas of the SECS both downstream and upstream.     

Sensor‐based flow pattern detection—gas–liquid–liquid upflow through a vertical pipe

Flow distribution during gas–liquid–liquid upflow through a vertical pipe is investigated. The optical probe technique has been adopted for an objective identification of flow patterns. The probability density function (PDF) analysis of the probe signals has been used to identify the range of existence of the different patterns. Dispersed and slug flow have been identified from the nature of the PDF, which is bimodal for slug flow and unimodal for dispersed flow. The water continuous, oil continuous, and emulsion type flow distributions are distinguished on the basis of the PDF moments. The method is particularly useful at high flow rates where visualization techniques fail. Based on this, a flow pattern detection algorithm has been presented. Two different representations of flow pattern maps have been suggested for gas–liquid–liquid three phase flow. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3362–3375, 2014     

Flow regime identification of two-phase liquid-liquid upflow through vertical pipe

The present work has attempted to identify the flow patterns during liquid-liquid two phase flow through a vertical pipe. Dyed kerosene and water have been selected as the test fluids. The measurements have been made for phase velocities varying from 0.05 to 1.5 m/s for both the liquids. The conductivity probe technique has been adopted and three different probe designs have been used to identify the patterns under different flow conditions. A parallel wire type probe traversing the entire cross-section along a diametral plane has indicated the existence of bubbly flow at low phase flow rates and dispersed bubbly flow at high velocities of water. Apart from the visual appearance of the signals, different statistical analysis namely the probability density function and wavelet analysis have been performed for a better appraisal of the flow situation. The information in the PDFs have been quantified by means of the statistical moments. The existence of the core-annular flow at high kerosene and low water velocities has been confirmed from measurements using a different probe design. The intermediate region between the bubbly and annular flow patterns is characterized by a random distribution of the two liquids with continually changing interface between them. This has been named as the churn turbulent flow pattern. The information thus obtained has been represented in the form of a flow pattern map.     

上倾管高黏油气两相流型及压降特性

利用室内实验装置,对上倾管内高黏油气两相流的流型和压降特性进行了实验研究。实验中观测到7种流型,得到了不同工况下的压力波动信号及压降值。实验结果表明,由于液相黏度的影响,上倾管内大部分流型的过渡边界向流型图的左侧偏移,且黏度越大偏移程度越大。将流型数据与Barnea流型判断模型进行对比,发现在高黏度时两者误差较大。根据压降数据得出,由于高黏度时液滴的附着作用增强,在气液表观速度均较小时,会出现黏度增加而压降却减小的现象。验证了OLGA模型和Zhang模型对于压降的计算精度,发现高黏度时模型的计算误差远大于低黏度情况。通过高黏度闭合关系式对Zhang模型进行修正,结果表明可以显著地提高其计算精度。     

偏心楔形喂料斗卸料过程中颗粒流动特性

采用三维离散单元法,研究了偏心楔形喂料斗中不同粒径颗粒卸料过程的流场分布,建立了适用于偏心楔形喂料斗的整体流系数模型,分析了料斗卸料流型以及卸料流型与卸料质量流率的相关性,并通过实验验证了离散元模型的可靠性。结果表明：偏心楔形喂料斗内颗粒流场分布以靠近喂料管口区域为高速区,并呈辐射状朝远离垂直壁面端的料斗上部低速区过渡,高速区颗粒流场的整体一致性好,低速区颗粒流场呈局部涡流状;颗粒粒径增大,颗粒整体流动性变差,高速区域范围减小,低速区域范围增大,过渡区域变模糊;当颗粒粒径不大于10 mm时,整体流系数与颗粒粒径呈线性负相关,卸料质量流率与整体流系数呈线性正相关。