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%.     

Surface wettability and flow properties of non-metallic pipes in laminar flow

In this paper, three liquids flowing in five pipes with the same inner diameter of 14 mm were studied to determine the relationship between the surface wettability and flow properties in laminar flow(Re b 2000). This was motivated by oilfield observations of increased pressure drops in non-metallic pipes compared to those in metal pipes,which was contrary to expectations. A new expression for the frictional coefficient that considers the Reynolds number and contact angle θ in laminar flow for non-metallic pipes was proposed based on the experimental results of single-phase flow using dimension and regression analyses. The solutions of the anomalous phenomenon were proposed from the perspectives of the pipe diameter, contact-angle difference, and the compatibility between flexible composite pipe and JLHW105 oil according to the new formula. The surprising finding was that the surface wettability could control the frictional resistance by the critical contact angle(39.9°) obtained at the same Reynolds number. If 0° b θ≤ 39.9°, the frictional coefficient increased as the contact angle increased. In contrast, if 39.9° b θ b 180°,the frictional coefficient decreased with increasing contact angle. The influences of the pipe diameter and contactangle difference on the pressure drop difference of JLHW105 oil showed an inversely proportional relation. A series of materials and liquids were tested. The selection of pipe material for transporting a given fluid can be based on the contact angle, surface tension, and critical limit of the contact angle obtained. The research results are expected to provide some guidelines for the selection of the appropriate pipe material for a given set of fluids.     

Mixture temperature prediction of waxy oil–water two-phase system flowing near wax appearance temperature

Temperature sensitivity of waxy crude oils makes it difficult to study their flow behaviour in the presence of water especially near their wax appearance temperature(WAT). In this study a method was proposed and implemented to mitigate such difficulties which was applied in predicting mixture temperatures(Tm) of a typical Malaysian waxy crude oil and water flow in a horizontal pipe. To this end, two analytical models were derived firstly from calorimetry equation which based on developed two correlations for defining crude oil heat capacity actualized from the existed specific heat capacities of crude oils. The models were then applied for a set of experiments to reach the defined three predetermined Tm(26 °C, 28 °C and 30 °C). The comparison between the predicted mixture temperatures(Tm,1and Tm,2) from the two models and the experimental results displayed acceptable absolute average errors(0.80%, 0.62%, 0.53% for model 1; 0.74%, 0.54%, 0.52% for model 2). Moreover,the average errors for both models are in the range of standard error limits(±0.75%) according to ASTM E230.Conclusively, the proposed model showed the ease of obtaining mixture temperatures close to WAT as predetermined with accuracy of ± 0.5 °C approximately for over 84% of the examined cases. The method is seen as a practical reference point to further study the flow behaviour of waxy crudes in oil–water two-phase flow system near sensitive temperatures.     

Oil–water pre-separation with a novel axial hydrocyclone

A novel hydrocyclone with guide vanes, named as axial hydrocyclone(AHC), is designed to tackle the problem of oil–water separation faced by most mature oilfields. Optimal design of the AHC is carried out by using numerical methods. The effects of guide vanes, cone angle, tapered angle and overflow pipe on the oil–water separation are discussed in this paper. The results show that a double swirling flow is generated in the tapered section where oil–water separation occurs. Both the cylindrical and the tapered section have important influences on AHC performance. On the basis of single factor results, response surface methodology is employed to optimize the AHC design. The experimental results indicate that the novel AHC has an excellent performance for the oil–water separation.     

规整填料内单相流的LDV实验研究

To date, many models have been developed to calculate the flow field in the structured packing by the computational fluid dynamics （CFD） technique, but little experimental work has been carried out to serve the vali-dation of flow simulation. In this work, the velocity profiles of single-phase flow in structured packing are measured at the Reynolds numbers of 20.0, 55.7 and 520.1, using the laser Doppler velocimetry （LDV）. The time-averaged and instantaneous velocities of three components are obtained simultaneously. The CFD simulation is also carried out to numerically predict the velocity distribution within the structured packing. Comparison shows that the flow pattern, velocity distribution and turbulent kinetic energy （for turbulent flow） on the horizontal plane predicted by CFD simulation are in good agreement with the LDV measured data. The values of the x-and z-velocity components are quantitatively well predicted over the plane in the center of the packing, but the predicted y-component is sig-nificantly smaller than the experimental data. It can be concluded that experimental measurement is important for further improvement of CFD model.     

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.     

双螺旋电容传感器水平油水两相流液相持率测量特性(英文)

This paper presents the characteristics of a double helix capacitance sensor for measurement of the liquid holdup in horizontal oil–water two-phase flow. The finite element method is used to calculate the sensitivity field of the sensor in a pipe with 20 mm inner diameter and the effect of sensor geometry on the distribution of sensitivity field is presented. Then, a horizontal oil–water two-phase flow experiment is carried out to measure the response of the double helix capacitance sensor, in which a novel method is proposed to calibrate the liquid holdup based on three pairs of paral el-wire capacitance probes. The performance of the sensor is analyzed in terms of the flow structures detected by mini-conductance array probes.     

水平管气液两相弹状流液弹频率的水动力学新模型

The prediction of slug frequency has important significance on gas-liquid two-phase flow. A hydrodynamic model was put forward to evaluate slug frequency for horizontal two-phase flow, based on the dependence of slug frequency on the frequency of unstable interfacial wave. Using air and water, experimental verification of the model was carried out in a large range of flow parameters. Six electrical probes were installed at different positions of a horizontal plexiglass pipe to detect slug frequency development. The pipe is 30 m long and its inner diameter is 24 ram. It is observed experimentally that the interracial wave frequency at the inlet is about i to 3 times the frequency of stable slug. The slug frequencies predicted by the model fit well with Tronconi (1990) model and the experimental data. The combination of the hydrodynamic model and the experimental data results in a conclusion that the frequency of equilibrium liquid slug is approximately half the minimum frequency of interfacial wave.     

Robust,fluorine-free and superhydrophobic composite melamine sponge modified with dual silanized SiO_2 microspheres for oil–water separation

Massive oily wastewater discharged from industrial production and human daily life have been an urgent environmental and ecological challenge. Superhydrophobic materials have attracted tremendous attention due to their unique properties and potential applications in the treatment of wastewater. In this study, a novel superhydrophobic/superoleophilic composite melamine sponge modified with dual silanized Si O_2 microspheres was fabricated simply by a two-step sol–gel method using vinyltriethoxysilane and hexadecyltrimethoxysilane as functional agent, which exhibited a water contact angle of 153.2° and a water sliding contact angle of 4.8°. Furthermore, the composite sponge showed the excellent oil adsorption performance and the compressive elasticity reaching up to 130 g·g~(-1) of dichloromethane and 33.1 k Pa of compressive stress. It was worth noting that the composite sponge presented the excellent separation efficiency(up to 99.5%) in the processes of continuous oil/water separation. The robust superhydrophobic composite melamine sponge provided the possibility with the practical application for oil–water separation.     

Highly efficient[C8mim][Cl] ionic liquid accompanied with magnetite nanoparticles and different salts for interfacial tension reduction

The 1-octyl-3-methylimidazolium chloride, [C_8 mim][Cl] ionic liquid(IL) was used as a novel surfactant in n-heptane/water system. The interfacial tensions(IFT) were measured and corresponding variations were investigated. An IFT reduction of 80.8% was appropriate under the IL CMC of about 0.1 mol·L~(-1) and stronger effects were achieved when magnetite nanoparticles and salts were present profoundly under alkaline p Hs.The equilibrium IFT data were accurately simulated with the Frumkin adsorption model. Hereafter, the saturated surface concentration, equilibrium constant and interaction parameter were obtained and their variations were demonstrated. Further, emulsion stability and contact angle of oil/water interface over quartz surface were studied. The oil/water emulsion stability was hardly changed with nanoparticles; however, the stability of oil/water + IL emulsions was significantly improved. It was also revealed that the presence of sodium and calcium chloride electrolytes fortifies the IL impact, whereas sodium sulfate weakens. From dynamic IFT data and fitting with kinetic models, it was found that the IL migration toward interface follows the mixed diffusion–kinetic control model. Consequently, the IL diffusion coefficient and the appropriate activation energy were determined.     

水平渐变管内油水两相流模拟研究

为优化油气集输管道局部管道结构,采用计算流体力学软件对水平渐变管内油水两相流进行数值模拟,对比不同含水率、不同入口流速条件下两相流流型,分析油水两相流在管道内的压力分布规律。结果表明,渐变管内油水两相流流型为水包油流型,管壁主要为油相润湿;渐缩管压力随流向位移持续下降,渐扩管先下降后上升再下降;整体压降速率与含水率成反比,与入口流速成正比。研究结果可以为优化稠油集输管网管道结构、降低管道流动能耗等油水混输问题提供参考。     

重力场中水平纤维悬垂液滴形状的模型研究

通过搭建可视化试验台观测了重力场中水平金属纤维表面的液滴形状，并测量了液滴形状参数，包括液滴直径、高度、接触角、接触线宽度和接触线高度。通过拟合参数关联式，求解了液滴固-液界面子模型和气-液界面子模型的描述方程，开发了一种椭球形的纤维液滴形状模型。液滴模型的轮廓预测结果和观测试验得到的液滴图像吻合度较好，可以在±10％的误差范围内描述98%的试验结果，平均偏差为4.6％。     

Equilibrium shape and contact angle of sessile drops of different volumes—Computation by SPH and its further improvement by DI

Equilibrium shapes of sessile liquid drops over horizontal substrates are modeled using smoothed particle hydrodynamics (SPH). The model can predict the variations of shape and contact angle of drops as a function of drop volume. In the model, a scheme of repositioning the particle at the triple line has been incorporated to attain the in situ contact angle. The simulations show a reasonable match with available analytical results. However, some mismatch of the drop shape near the three-phase contact line is observed. To improve the predictability, combined diffused interface smoothed particle hydrodynamics model (Das and Das, 2009b) is employed. The developed hybrid simulations improve the prediction. Estimated drop shapes and contact angle agree with experimental data reasonably well over a wide range of fluid properties and drop volume. The technique establishes the suitability of a particle-based hydrodynamic simulation for the modeling of complex interfaces and three-phase contact lines.     

相态逆转及其密度波的不稳定性

在长度／直径比为1250的水平管内研究了液液相态逆转现象及其对油水两相流和油气水多相流水动力特性的影响．以双流体模型为基础,考虑悬浮相所受的雷诺应力,提出了描述气液两相流和液液两相流中密度波不稳定性的通用模型．模型计算结果表明,“水包油”流型与“油包水”流型之间的相态逆转在悬浮相体积分数为0.3左右发生,与经验性结论相吻合,揭示了相态逆转的机理．     

三相卧螺离心机设计分析及结构参数对分离效果的影响

首先提出了用于油水砂分离的三相螺旋沉降式离心机两种结构模型。通过CFD数值计算发现,带有轴向管法兰的三相卧螺离心机结构模型存在一定的缺陷,即管法兰上有堵砂的情况出现且分离效率较低。通过改进设计,可调溢流挡板的三相卧螺离心机结构模型是可取的。该模型有较高的油相回收率,且固相也相对较干燥,适用于油水固三相分离。该模型还具有水与油砂分离、油水与砂分离或油与水砂分离等几种不同的排液方式。对此三相卧螺离心机加工制造,搭建实验平台,通过实验研究发现,此种结构的三相卧螺离心机对油相的分离效率较高,挡板圆弧中心到转鼓中心轴的距离对分离效率有着不同的影响。     

Hydrodynamics of disturbed flow and erosion–corrosion. Part II — Two-phase flow study

Erosion–Corrosion in turbulent, two-phase liquid/particle flow with recirculation, after a sudden pipe expansion is studied by the application of a numerical flow model along with two different erosion models. The flow model, which is based on a two-phase flow version of a standard two-equation model of turbulence and a stochastic simulation of particle-fluid turbulence interactions, is capable of successfully predicting local values of time averaged fluid velocities and turbulent fluctuations, as well as predicting particle dispersion and particle-wall interaction. The erosion models used are that of Finnie (1960) and a modified version suggested by Bergevin (1984). The agreement of the predicted and measured hydrodynamic parameters, for flow through a sudden expansion, was satisfactory. Predictions of erosion rates using Bergevin's modified model were in good agreement with the stainless steel erosion measurements for a 2% water/sand slurry flow. The erosion–corrosion model was successful in predicting the overall pattern and rates of metal loss for carbon steel.     

垂直上升管内气体扰动油水两相乳化液流动特性

气体 -油水乳化液的管内流动是原油开采、油气输运以及许多化工领域中经常遇到的工程现象 ,正确认识油水乳化液在气体扰动下的动力特性对圆管内油、气、水多相流的理论建模具有重要的工程应用和学术价值 .本文通过垂直上升管内油气水三相弹状流的实验研究 ,提出了垂直上升弹状流中油水乳化液黏度计算模型 .基于此模型 ,油水乳化液在气体掺入下的流动特性可表现为气体扰动变稠的非牛顿流体特性和气体扰动变稀的非牛顿流体特性 .     

FLOW CHARACTERISTICS OF GAS-OIL-WATER EMULSION IN PIPES

气体 -油水乳化液的管内流动是原油开采、油气输运以及许多化工领域中经常遇到的工程现象 ,正确认识油水乳化液在气体扰动下的动力特性对圆管内油、气、水多相流的理论建模具有重要的工程应用和学术价值 .本文通过垂直上升管内油气水三相弹状流的实验研究 ,提出了垂直上升弹状流中油水乳化液黏度计算模型 .基于此模型 ,油水乳化液在气体掺入下的流动特性可表现为气体扰动变稠的非牛顿流体特性和气体扰动变稀的非牛顿流体特性 .     

Discussion on the pressure drop calculation for oil‐water separated flow using a one dimensional two‐fluid model

The purpose of this work is to seek the key factors influencing the pressure drop calculation for oil‐water separated flow using a one dimensional two‐fluid model. Closure relations published for the two‐fluid model such as interface configuration, wall, and interfacial shear stress correlations are summarized. Interface configurations are established by numerically solving the Young‐Laplace equation, correlated with the Bond number, contact angle, and water holdup. Results show that the interface transforms from concave to convex with the enlargement of the contact angle and becomes flat as the Bond number increases. For the pressure drop calculation, a limited difference of predicted accuracy between the curve and flat interface is found. Discussions of both the wall and interfacial friction factor correlation on the pressure drop calculation are performed. In contrast to the effect of the interfacial friction factor, the correlation of the wall friction factor is found to have more contributions. We validate the prediction accuracy of different wall frictions factors using eight groups of published experiment results, and one correlation is recommended and being further extended.