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The 7th International Symposium on Measurement Techniques for multiphase flows

作者： J.Ye L.J.Guo H.L.Zhou State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

A type of capacitance probe performance with two brass electrodes intertwined on the outer wall of insulation pipe like a double helix is investigated numerically in this paper,which can measure water fraction in air-oil-water two or three-phase flow in oil *** motivation of this paper is to optimize this kind of probe to improve its electric response and spatial resolution and so a 3-D numerical simulation using finite element method is employed to evaluate the effect of electrodes configuration of this capacitance probe on measuring water fraction in horizontal *** electrostatic field of the probe is preliminarily analyzed referred to stratified flow of air-water two-phase flow *** parameters are considered as main variables which have an important effect on the precision of the probe,such as central angle,position angle and length of the two *** the electrostatic field analysis,lumped capacitance between the two electrodes is obtained in every different electrode geometry model and the results of each model are compared to each other in order to select a better arrangement of the electrodes that has a better response to water *** by using circuit simulation method,the numerical calculated lumped capacitance is transferred to voltage output through the circuit used in the *** relationship between voltage and water fraction of calculated and experimental result are compared in order to test the reasonableness of the *** results show that at high water fraction,the difference between numerical and measured data agrees very well.

关键词： Numerical simulation water fraction capacitance probe multiphase flow

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Enhancement of Photoelectrochemical Performance by Doping Tantalum Ions in Hematite （a-Fe2O3） Nanorod Photoanodes

Enhancement of Photoelectrochemical Performance by Doping Ta...

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International Conference on Nanoscience & Technology,China 2013(ChinaNANO 2013)

作者： Yanming Fu Liang Zhao Shaohua Shen State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Ta-doped hematite (α-Fe 2 O 3 ) nanorod array electrodes were successfully prepared on FTO substrates using the conventional method by adding TaCl 5 in the aqueous solution directly. With the increasing of TaCl 5 dopant content, the photoelectrochemical (PEC) activity of the Ta-dopedα-Fe 2 O 3 nanorod films firstly increased and then decreased. Compared with the undoped α-Fe2O3 nanorod films, the optimal content of Ta-doped hematite sample showed about 3.5 times higher photoelectrochemical activity under the irradiation of solar light (AM 1.5, 100 mW·cm-2), as high as 0.53 mA·cm -2 at 0.5V vs. SCE(saturated calomel electrode) in 0.5 M Na 2 SO 4 . In order to analyze the mechanism of tantalum ions in changing the photoelectrode performance, all films were characterized by Raman spectra, UV-visible spectra, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrum(EDX) and X-ray photoelectron spectroscopy (XPS). The results reveal that at low Ta doping contents, small amount of Ta is dopedinto the nanorods of α-Fe 2 O 3 films and the photocurrent improvement is mainly attributed to the reduced electron-hole recombination in the α-Fe 2 O 3 nanorod *** at high Ta doping contents, superfluous Ta dopant forms a thick tantalum oxide layer and the layer completely covers the nanorods of α-Fe 2 O 3 films. This special surface structure reduces the number of photogenerated electrons (or holes) and weakens the charge transfer ability to raise the surface charge recombination of α-Fe 2 O 3 nanorods, leading to the decreased photoelectrochemical activity.

关键词： α-Fe 2 O 3 , nanorods, photoelectrochemical, doping

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Enhancing Photocurrent in Unannealed NiS x /CdS Photoelectrochemical System for Water Splitting and Hydrogen Production

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MRS Online Proceedings Library 2011年第1期1326卷 1-6页

作者： Ning Zhang Liejin Guo State Key Laboratory of Multiphase Flow in Power Engineering (MPFL) School of Energy and Power Engineering Xi’an Jiaotong University Shaanxi PR China

In this work, NiSx was deposited on FTO by chemical bath and worked as the inner layer in order to enhance the photocurrent of CdS film. It is found the unannealed CdS/NiSx had a higher photocurrent than unannealed CdS, but after annealing, the photocurrent of CdS/NiSx showed dramatical decrease. The mechanism was discussed in detail by UPS and current-potential curves.

关键词： Ni S thin film

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An improved moving particle semi-implicit method for simulating viscous free surface flows without compressible stress instability

An improved moving particle semi-implicit method for simulat...

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7th International Conference on Fluid Mechanics(ICFM7)

作者： Hao Xiang Bin Chen State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University

＜正＞Moving Particle Semi-implicit（MPS）method and Smoothed Particle Hydrodynamics（SPH）have been widely applied in modelling free surface ***,application of the meshfree methods was still limited due to the problem of compressible stress instability,which occurs in the presence of attractive forces when particles are approaching and the low accuracy of the numerical schemes for gradient operator.

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Movement of Oil-Water-Solid Three-Phase Contact Line under Velocity Gradients

Movement of Oil-Water-Solid Three-Phase Contact Line under V...

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2016年大连国际微流控和芯片实验室大会

作者： Wenxiu ZHENG Chengzhen SUN Bofeng BAI State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

The movement of three-phase contact line which formed in the oil-water-solid three-phase area is of great importance in a number of applications,such as oil recovery,groundwater remediation,decontamination and *** process of oil droplets/film migration and detachment,which are controlled by the moving contact line,has shown its great significance in oil *** are various factors which can drive the contact line to move,such as pressure and electrical driving forces,etc,which will generate a velocity gradient for the flow near the *** this paper,we dedicate to investigate the moving rule of contact line under a velocity gradient from molecular dynamics(MD) ***,MD simulations are implemented by the FORCITE module in the Material Studio software to obtain the microscopic view of the moving contact *** size of the system is about 14 nm×3 nm×50 nm,including 2880 oil molecules and 33080 water *** interatomic interactions are described by COMPASS force field,for which van der Waals interaction is described by 9-6 Lennard-Jones potential and electronic interaction is described by Coulombic potential *** water and oil molecules are arranged on a silica substrate and the velocity gradient is generated by moving the upper *** water molecules we used SPC/E *** cutoff radius is 1.25 nm to the short-range intermolecular *** long-range Coulombic interactions are handled with the Ewald *** on the MD simulations,the configuration of water and oil molecules shows us the morphology of the contact line and variations of the contact angle at different velocity *** results exhibit that the contact line will move only when the velocity gradient is larger than a certain *** force inside the contact line region such as friction force and shear stress are calculated to make a deep understanding of the moving contact *** property of water/oil molecules and velocity profile

关键词： Movement of Oil-Water-Solid Three-Phase Contact Line under Velocity Gradients Velocity

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The effects of Na+ and Cl- ions on the oil-water interface:a molecular dynamics study

The effects of Na+ and Cl- ions on the oil-water interface:a...

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2016年大连国际微流控和芯片实验室大会

作者： Boyao Wen Chengzhen Sun Bofeng Bai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Ions at the oil-water interface is a ubiquitous phenomenon which plays a important role in many industrial processes,such as extraction separation,nanoparticle assembly,enhanced oil recovery,*** the petroleum industry,due to the long-term interaction with solids and crude oil,the water including formation water,injection water and aqueous solution dissolves lots of ions,such as Na,K,Ca,Mg Cl,SO,*** migration of charged ions in the bulk phase or interface between oil and water has a significant influence on the molecular packing of active species at the interface,zeta potential of oil droplets and microstructure and strength of interfacial film by changing the interfacial tension,interface viscosity and electrical repulsion of charged ganglia,thus affecting the stability of crude oil emulsions and the oil displacement in porous ***,more detailed knowledge of how ions affect the properties of oil-water interface is ***,we perform a molecular dynamics（MD） study on the effects of ions on the oil-water interface using the LAMMPS package in the NVT *** temperature of the system is kept at 300 K via Nose-Hoover *** simulation box,whose volume equals to4×4×11.4 nm,is divided into two layers of oil and water *** boundary conditions are applied in x-,y-and *** is adopted as the oil phase according to "equivalent alkane carbon number"（EACN） value of crude *** are arranged uniformly in the water *** and Clions are involved,because they are basic components of brine and quite common in the *** atomic interactions between decane molecules are described by the OPLS-AA potential while the TIP3 P model of water is adopted to consider both dispersive and electrostatic *** cut-off distance of all potentials is 10 *** results demonstrate that the structures and dynamics of the oil-water interface is significantly affected by Na and *** kosmotropes,Na ions remain strongly h

关键词： The effects of Na and Cl ions on the oil-water interface:a molecular dynamics study

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Coupled double-distribution-function lattice Boltzmann method for the compressible Navier-Stokes equations

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Physical Review E 2007年第5期76卷 056705-056705页

作者： Q. Li Y. L. He Y. Wang W. Q. Tao State Key Laboratory of Multiphase Flow School of Energy and Power Engineering Xi’an Jiaotong University Xi’an Shaanxi 710049 China

A coupled double-distribution-function lattice Boltzmann method is developed for the compressible Navier-Stokes equations. Different from existing thermal lattice Boltzmann methods, this method can recover the compressible Navier-Stokes equations with a flexible specific-heat ratio and Prandtl number. In the method, a density distribution function based on a multispeed lattice is used to recover the compressible continuity and momentum equations, while the compressible energy equation is recovered by an energy distribution function. The energy distribution function is then coupled to the density distribution function via the thermal equation of state. In order to obtain an adjustable specific-heat ratio, a constant related to the specific-heat ratio is introduced into the equilibrium energy distribution function. Two different coupled double-distribution-function lattice Boltzmann models are also proposed in the paper. Numerical simulations are performed for the Riemann problem, the double-Mach-reflection problem, and the Couette flow with a range of specific-heat ratios and Prandtl numbers. The numerical results are found to be in excellent agreement with analytical and/or other solutions.

关键词： NUMERICAL-SIMULATION STRONG SHOCKS flowS MODEL SCHEMES CONNECTION

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Study on Steam-Water Solar Cavity Receiver

Study on Steam-Water Solar Cavity Receiver

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2014第四届国际新能源产业大会——主题：助力一个美丽、洁净、可持续发展的家园

作者： Jinjia Wei State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

Solar energy is clean without pollution,rich and free,so solar thermal power has the huge potential for future energy *** type concentrating technology can be used for large-scale solar power *** the power tower system,the heat receiver is the key equipment for sunlightheat *** thermal performance of the receiver will affect the efficiency of the entire power *** is no rich experience on the design of receiver,which is mainly based on the coal-fired *** to the non-uniform and instantaneous characteristics of sunlight,the receiver should differ greatly from the conventional coal-fired *** it is necessary to study the receiver according to the sunlight *** experiment platform for testing the thermal performance of a water/steam cavity receiver was firstly designed and *** start-up curves under different operating pressures were obtained and the receiver has low thermal efficiency of only about 55-70%.The low thermal efficiency is attributed to the low mass flow rate.A combined method was proposed to evaluate the thermal performance of the cavity receiver for start up and *** numerical results are in good agreement with the *** results suggested that an appropriate mass flow rate of 200 kg/h should be chosen for the design and operation of the experiment *** thermal performance of a solar cavity receiver under windy conditions was numerically *** heat flux and temperature distributions on boiling tubes in the cavity were *** convective and radiative heat losses were analyzed in *** the wind flow angle or velocity can obviously affect the air velocity inside the cavity,which reaches the maximum value for side on wind,resulting in a large convective heat *** on the experimental and numerical studies,a water/steam cavity receiver was designed and *** receiver is now being used in 1MW power tower plant in China with a

关键词： Study on Steam-Water Solar Cavity Receiver

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A Model for Wave Properties in Churn flow

A Model for Wave Properties in Churn Flow

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The Fifth China-Korea Workshop on Nuclear Reactor Thermal Hydraulics

作者： Ke Wang Bofeng Bai Jiahuan Cui State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University

A model for wave properties, such as wave velocity and amplitude in churn flow has been developed in this paper. The results demonstrate that the wave behavior differs from that in annular flow. In addition, the critical amplitude A c decreases with the increase in gas flow rate. Moreover, the maximum amplitude A max decreases with the increasing of gas mass flux but increase with the increasing of liquid mass flux. The average absolute deviations (AAD) for A c and A max are 16.29% and 7.10%, respectively.

关键词： A Model for Wave Properties in Churn flow Model

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Capacitance probe for water holdup measurement in crude oil-water flows

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Measurement: Sensors 2020年 10-12卷

作者： Zheng, Xuebo Yang, Bo Bai, Bofeng State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Water holdup in crude oil-water flows is a crucial parameter to identify flow patterns or monitor the flow process in oil production. It has been increasingly important to accurately predict water holdup. Due to the simple structure and robust performance, capacitance probes have been widely used in experimental research and industrial application. In this paper, we proposed a water holdup measurement device based on a capacitance probe for crude oil-water flows. The measurement principle lies in the fact that the output capacitance is proportional to the part of the probe immersed in water. It was found that when inserted into crude oil, the surface of the probes will absorb hydrocarbons and form an oil film covering the probes. The formed oil film will reduce the sensitivity of the output capacitance to the water layer height. The thicker the film the lower the sensitivity. We examined the parameters that affect the thickness of the formed oil film and found that the thickness is mainly dependent on temperature and water holdup. The higher the temperature the thinner the formed oil film. The reason is that an increase of temperature leads to a decrease of viscosity. In addition, as the temperature approached about 50 °C, the thickness is nearly unchanged. As for the water holdup, at low temperatures the effect is considerable. At relatively high temperatures, the effect is minor and can be neglected. The experimental results showed that the capacitance probes have the highest sensitivity at about 50 °C. We designed and manufactured a prototype of the measurement device. The probes were inserted with heating wires to heat the crude oil near the probes and the current was controlled by an integrated circuit to maintain the temperature at about 50 °C. The field test showed that the natural gas entrained in the production fluids caused the device to under-predict the water holdup. After gas-liquid separation, the prediction errors were within ±6%. © 2020 The Author

关键词： Crude oil

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