Gas-Liquid Two-Phase Research Articles

Effect of Diversion Cavity Geometry on the Performance of Gas-Liquid Two-Phase Mixed Transport Pump

For the purpose of improving the transport capability of the mixed transport pump, a new self-made three-stage deep-sea multiphase pump was taken as the research object. Based on the Euler-Euler heterogeneous flow model, liquid (water) and gas (air) are used as the mixed media to study the external characteristics and internal flow identities of the mixed pump under different gas volume fraction (GVF) conditions. According to the simulation results, a local optimal design scheme of the diversion cavity in the dynamic and static connection section is proposed. The numerical results before and after the optimization are compared and analyzed to explore the effect of the diversion cavity optimization on the performance, blade load and internal flow identities of the pump. The results show that the head and efficiency are obviously improved when the inner wall of the diversion cavity is reduced by 4 mm along the radial direction. After optimization, under the condition of 10% gas content, the head and efficiency is increased by 3.73% and 2.91% respectively. Meanwhile, the hydraulic losses of the diversion cavity and diffuser are reduced by 9.11% and 4.32% respectively. The gas distribution in the impeller is improved obviously and the phenomenon of a large amount of gas phase accumulation is eliminated in the channel. In addition, the abnormal pressure load on the blade surface is eliminated and the turbulent flow energy intensity is reduced. The average turbulent kinetic energy ( T K ) at i = 0.51 of the first stage impeller passage is reduced by 35%. Finally, the reliability of the numerical method is verified by the experimental results. To sum up, the performance and internal flow identities of the optimized mixed transport pump are improved, which verifies the availability and applicability of the optimization results. This provides a reference for the research and design of a multiphase mixed transport pump in the future.

Model of Liquid and Gas Flow Mixing in a Two-Phase Jet Device (the Concept of Superposition in Investigation of Two-Phase Fluids)

A model for two-phase flow is proposed using a two-phase liquid-gas jet device as an example. The proposed model analyzes a separate flow of fluids and superposition of flows with account of their mutual influence. A comparison with test results is presented.

Artificial Void Wave Propagation in a Gas-Liquid Two-Phase Horizontal Turbulent Channel Flow

Artificial Void Wave Propagation in a Gas-Liquid Two-Phase Horizontal Turbulent Channel Flow

Effect of Gas-Liquid Two-Phase Flow in a Venturi Tube on Atomization and Transportation of Coagulant

Compulsive sedimentation of soil particles using coagulant is one of the countermeasures for long-term turbid water in a dam reservoir. We used allophane as a coagulant, since it is considering that allophane obtained from nature has low environmental impact when it is added into the dam reservoir. The objective of the present study is to propose an atomization and transportation technique for allophane with a Venturi tube and to elucidate their mechanisms. We successfully visualized atomization behavior of allophane in detail and considered the atomization mechanisms. In addition, we confirmed that the turbidity of the water is improved by adding atomized allophane. In transportation experiment of allophane, it is found that allophane transportation is promoted in the condition of microbubble generation. Furthermore, visualization of allophane adhering to microbubble and following water flow is achieved, and it is suggested that allophane is transported by microbubble. Finally, we measured zeta potential of particles that is important factor in allophane transportation, and tried to elucidate the transportation mechanisms with evaluating the relationship with Sauter mean diameter of allophane.

Flow Pattern of Gas-Liquid Two-Phase Flow Driven by a Rotating Cylinder

Flow Pattern of Gas-Liquid Two-Phase Flow Driven by a Rotating Cylinder

Numerical simulation, validation, and analysis of two-phase slug flow in large horizontal pipes

Multiphase flow, especially two-phase gas-liquid flow, is of great importance for a variety of applications and industrial processes, for example in the nuclear, chemical, or oil and gas industries. In this contribution, we present simulation results for gas-liquid slug flow in large horizontal pipes. Six test cases with different oil, water, and gas flow rates are considered, which cover a wide range of different slug flows. The numerical predictions are validated by comparison with experimental data obtained from video observations. The relative error of the mean liquid level between experiment and simulation is less than 12.3% for all but one test cases. Furthermore, a frequency analysis is performed. The single-sided amplitude spectrum as well as the smoothed power spectral density are calculated. For both, experimental and simulation data, one observes an increase of the dominant frequencies if the ratio of liquid and gas superficial velocity is increased.

Role of all jet drops in mass transfer from bursting bubbles

When a bubble bursts at the surface of a liquid, it creates a jet that may break up and produce jet droplets. This phenomenon has motivated numerous studies due to its multiple applications, from bubbles in a glass of champagne to ocean/atmosphere interactions. We simulate the bursting of a single bubble by direct numerical simulations of the axisymmetric two-phase liquid-gas Navier-Stokes equations. We describe the number, size and velocity of all the ejected droplets, for a wide range of control parameters, defined as non-dimensional numbers, the Laplace number which compares capillary and viscous forces and the Bond number which compares gravity and capillarity. The total vertical momentum of the ejected droplets is shown to follow a simple scaling relationship with a primary dependency on the Laplace number. Through a simple evaporation model, coupled with the dynamics obtained numerically, it is shown that all the jet droplets (up to fourteen) produced by the bursting event must be taken into account as they all contribute to the total amount of evaporated water. A simple scaling relationship is obtained for the total amount of evaporated water as a function of the bubble size and fluid properties. This relationship is a first important step toward building a physics-based model of the ocean-atmosphere water vapour fluxes controlled by bubbles bursting at the surface.

Uncertainty Propagation through a Point Model for Steady-State Two-Phase Pipe Flow

Uncertainty propagation is used to quantify the uncertainty in model predictions in the presence of uncertain input variables. In this study, we analyze a steady-state point-model for two-phase gas-liquid flow. We present prediction intervals for holdup and pressure drop that are obtained from knowledge of the measurement error in the variables provided to the model. The analysis also uncovers which variables the predictions are most sensitive to. Sensitivity indices and prediction intervals are calculated by two different methods, Monte Carlo and polynomial chaos. The methods give similar prediction intervals, and they agree that the predictions are most sensitive to the pipe diameter and the liquid viscosity. However, the Monte Carlo simulations require fewer model evaluations and less computational time. The model predictions are also compared to experiments while accounting for uncertainty, and the holdup predictions are accurate, but there is bias in the pressure drop estimates.

Simulation of Gas-Liquid Two-Phase Flow in Metallurgical Process

Simulation of Gas-Liquid Two-Phase Flow in Metallurgical Process

Ultrafast X-Ray Computed Tomography Imaging for Hydrodynamic Investigations of Gas–Liquid Two-Phase Flow in Centrifugal Pumps

AbstractGas entrainment into centrifugal pumps decreases pump performance and may raise safety issues, e.g., through insufficient cooling. Although there is some phenomenological knowledge in the form of correlations between operating parameters and pump performance, a further understanding via direct observation of the gas–liquid mixture was so far not possible. In this paper, we demonstrate the capability of ultrafast X-ray computed tomography (UFXCT) to disclose gas–liquid two-phase flow dynamics in the impeller region of a centrifugal pump mockup. Experiments were performed for gas injection at impeller speeds between 1300 rpm and 1600 rpm. We analyzed the X-ray image sequences with respect to characteristics of the gas distribution and compared them with time-averaged image data of a real pump obtained earlier with gamma-ray computed tomography (CT).

A posteriori error estimates for a compositional two-phase flow with nonlinear complementarity constraints

In this work, we develop an a-posteriori-steered algorithm for a compositional two-phase flow with exchange of components between the phases in porous media. As a model problem, we choose the two-phase liquid-gas flow with appearance and disappearance of the gas phase formulated as a system of nonlinear evolutive partial differential equations with nonlinear complementarity constraints. The discretization of our model is based on the backward Euler scheme in time and the finite volume scheme in space. The resulting nonlinear system is solved via an inexact semismooth Newton method. The key ingredient for the a posteriori analysis are the discretization, linearization, and algebraic flux reconstructions allowing to devise estimators for each error component. These enable to formulate criteria for stopping the iterative algebraic solver and the iterative linearization solver whenever the corresponding error components do not affect significantly the overall error. Numerical experiments are performed using the Newton-min algorithm as well as the Newton-Fischer-Burmeister algorithm in combination with the GMRES iterative linear solver to show the efficiency of the proposed adaptive method.

The Effect of a Conical Inner Electrode on the Mass-transfer Behavior in a Cylindrical Electrochemical Reactor under Single-Phase and Two-Phase (Gas-Liquid) Swirling Flow

The influence of a continuous change in the cross-section area on mass-transfer performance is analyzed in an electrochemical reactor under swirling flow. Thus, a conical frustum is used as an inner electrode in a cylindrical arrangement. A convergent flow is obtained by placing the conical frustum with its smaller base at the bottom of the reactor, or conversely, it produces a divergent flow. Experimental local mass-transfer coefficients along the electrode length are reported using the reduction of ferricyanide as a test reaction. The mass-transfer distribution as well as the global mass-transfer coefficient are both discussed in three geometric arrangements, i.e. constant interelectrode gap, convergent and divergent cases under single-phase and two-phase (gas-liquid) flow. The highest global mass-transfer coefficients are obtained for the convergent arrangement in the middle range of volumetric flow rates, giving out values 7.6% higher than those for the constant interelectrode gap case. Divergent geometry presents, as its main asset, the most uniform mass-transfer distribution in comparison with the other two configurations. The presence of the gas phase also has little influence on the mass-transfer performance of the reactor. Computational fluid dynamics calculations are in good agreement with experimental measurements.

Influence of Direct and Co-Flow Pre-Injection of a Gas Phase on Gas–Liquid Two-Phase Flow through a Vertical Minichannel

The influence of pre-injection of a gas phase on gas–liquid two-phase flow through a vertical minichannel is experimentally investigated. Circular minichannel of 2 mm inner diameter is considered for the investigations. Air is used as a gas phase and water is used as a liquid phase. The superficial gas and liquid velocities are kept as 0.0531–0.2653 and 0.1062–0.2653 m/s, respectively. Inlet premixing of gas–liquid two-phase flow is achieved with an injector equipped with a nozzle to inject a gas phase. Three nozzles are developed with inner diameters of 0.7, 2, 2.5 mm. Direct injection and co-flow pre-injections of gas phase are obtained with various positions of a nozzle (0, 25 and 50 mm) in an injector. Flow patterns such as bubbly flow, Taylor bubble flow and slug-annular flow are observed and captured using an EXILIM high-speed camera. The influence of nozzle size and its positions in an injector on the hydrodynamics of Taylor bubble flow as well as two-phase pressure drop are analysed in detail. Inlet premixing and two-phase flow hydrodynamics have significant influence of gas-phase pre-injection in a vertical minichannel.

Effect of the Inclination Angle on Slippage Loss in Gas-Liquid Two-Phase Flow

The lifting efficiency and stability of gas lift well are affected by the socalled slippage-loss effect in gas-liquid two-phase flow. The existing studies on this subject have generally been based on vertical and horizontal wells. Only a few of them have considered inclined pipes. In the present work a new focused study is presented along these lines. More specifically, we use the non-slip pressure drop model with Flanigan’s fluctuation correction coefficient formula (together with the parameters of slippage density, slippage pressure drop and slippage ratio) to analyze the influence of the inclination angle on slippage loss for different conditions (different gas-liquid superficial velocity and pipe diameters). Moreover, the “standard regression coefficient method” is used for multi-factor sensitivity analysis. The experimental results indicate that slippage loss is affected by multiple factors, and the influence of the inclination angle on slippage loss is less significant than other factors. The change of the slippage pressure drop with the superficial velocity of gas-liquid is similar to that of the total pressure drop. The inclination angles of 45° and 60° have the greatest influence on slippage loss. The correlation between slippage density and slippage ratio is not obvious. Using the so-called slippage ratio seems to be a more accurate option to evaluate the degree of slippage loss.

Multi-Scale and Multi-Physics Simulations for Gas-Liquid Two-Phase Flows

Multi-Scale and Multi-Physics Simulations for Gas-Liquid Two-Phase Flows

Visualization of Gas-Liquid Two-Phase Flow in a Packed Bed of Spheres

Visualization of Gas-Liquid Two-Phase Flow in a Packed Bed of Spheres

Effect of Bubble flow on Heat Transfer Characteristics in Gas-Liquid Two-Phase Flow in a Horizontal Tube Bundle

Effect of Bubble flow on Heat Transfer Characteristics in Gas-Liquid Two-Phase Flow in a Horizontal Tube Bundle

Measurements of Turbulence in a Gas-Liquid Two-Phase Flow by Using an Electro-Magnetic Probe and PIV Methods

Measurements of Turbulence in a Gas-Liquid Two-Phase Flow by Using an Electro-Magnetic Probe and PIV Methods

Algorithms for determination of the vector velocity field in a two-phase gas-liquid flow

Energy efficiency is a key issue of sustainable development. During the design of industrial devices, it strives to achieve the highest possible energy efficiency. In the industrial systems, two-phase flow is a difficult task, especially the prediction, and maintenance of the two-phase flow regime. That is why this research proposes the evaluation and choice of an algorithm that will give a hint of the device design for which the hydrodynamic conditions of the two-phase mixture flow may be evalu-ated. The tests were carried out in a rectangular vertical narrow channel, as this type of device is in common use. The work aimed to show which algorithm is better for such evaluation. Parameters such as pressure drop, heat, mass, and momentum transfer are influenced by the phase velocity field. Still, various models are used for the determination of the velocity field. Therefore, there is a problem of choosing a model that will give the results closest to the real conditions. Flow visualization gives the non-invasive determination of the actual velocity field. An analysis of the velocity field was performed, which showed that for different two-phase flow regimes there are differences for given algorithms. The following algorithms were used to determine the velocity vector field: adaptive correlation method and adaptive particle image velocity method were used which are the parts of the general digital particle image velocimetry. The determination of the velocity fields in the quantitative and qualitative assessment of a given two-phase flow re-gime was obtained. The result of the research is the evaluation of algorithms for characterization two-phase gas-liquid flow.

Application of videogrammetry in the mechanics of multi-phase systems

This paper is a description of the evolution of long-term research work on two-phase flows using parallel studies of dynamic image analysis and stochastic processes analysis. The state of current knowledge on the research of gas-solid and gas-liquid systems as well as a review of research relating to these issues are also presented. The work grants the principles of videogrammetric surveys based on stochastic analysis for a series of photographs taken with video techniques. The method applies the analysis of changes in selected features and parameters in the time domain. Especially in application to multiphase gas-liquid and solid-gas mixture flows, which are characterized by strong variabilities. Parameters such as flow patterns of the mixture were determined as time-space distributions of phase concentration, displacement velocities of separated two-phase structures, volume partitions of phases, and velocity field distributions are evaluated. The changes of certain parameters characterizing the flow in the time domain often hide more useful information. The subject of this study covers the basics of videogrammetry with a description of two-phase mixture motion for co-current flow in channels, mapping of the phase velocity field, also across the tube bundle in shell-and-tube apparatus, phase motion at the flow of a two-phase gas-liquid mixture in mini-channels, transport of liquids in air-lift pump and fluidization of solid particles.