Gas-Liquid Two-Phase Research Articles

A New CCERT System With Shielding for Gas-Liquid Two-Phase Flow

This work presents a new capacitively coupled electrical resistance tomography (CCERT) system with shielding for gas-liquid two-phase flow. The new system is developed from the aspects of hardware, image reconstruction algorithm and experiments. The hardware includes a 12-electrode CCERT sensor with shielding, a measurement circuit and an image reconstruction computer. The sensor with shielding is designed and the measurement circuit is developed to obtain the resistance information (real part of the impedance). Based on truncated singular value decomposition (TSVD) and density peaks clustering (DPC), a new image reconstruction algorithm is proposed. TSVD is introduced to obtain the initial image. DPC is improved and used to obtain the final image. Image reconstruction experiments were carried out with the new 12-electrode CCERT system with shielding. Experimental results show that the new CCERT system has good imaging performance. The design of the hardware is successful, and the new proposed image reconstruction algorithm is effective. Compared with the conventional image reconstruction algorithms, the proposed algorithm has higher imaging quality. The maximum relative image errors of the new system are 0.2887 under bubble flow and 0.4177 under stratified flow. Research results also indicate that the shielding design contributes to better imaging stability in interference environment.

Gas-entry pressure impact on the evaluation of hydrogen migration at different scales of a deep geological disposal of radioactive waste

Although the importance of gas-entry pressure in simulating two-phase liquid–gas flow in porous media has been studied at the column and borehole scales, its impact on the simulation of transient hydraulic-gas at different scales of a deep geological repository of radioactive waste (DGR) in low permeability clay rock during the post-closure phase has not yet been studied. The purpose of this work is to show that neglecting this phenomenon can lead to underestimation of the maximum gas pressure and water–gas fluxes simulated within the host rock and backfilled drift network. This could impact the performance of the engineered barrier system of a DGR. Simulations performed for a high-level waste disposal cell and for a simplified repository composed of hundreds of disposal cells situated in a clay host rock, show that gas preferentially migrates through the DGR components with low capillary entry pressures, such as the excavation damaged zone (Refers to the zone where fractures develop due to failure of the rock mass around galleries after tunneling) (EDZ), the engineered barriers materials (backfill, bentonite-plug…) and interfaces between the EDZ and these materials. Such a result could have significant consequences on the performance of a repository, due to the accumulation of gas in the drift network and high increase of gas pressure, which could lead to the host rock hydraulic fracturing.

Experimental Study on Gas-Liquid Two-Phase Stratified Flow at High Pressure in a Horizontal Pipe

This study investigates wave-stratified flow in a horizontal pipe at high pressure, and flow characteristics are obtained, such as flow pattern map, liquid film thickness, and pressure drop. Compared with a flow pattern map of a gas-liquid two-phase flow carried out at atmosphere, stratified flow zone is depressed with increasing system pressure and the critical gas superficial velocity decreases for smooth-wave-stratified flow transition, while the critical liquid superficial velocity increases for stratified-intermittent transition. On one hand, the compressed air results in an increase in momentum transfer between gas and liquid phases, which accounts for the smaller gas superficial velocity that is encountered in both smooth-wave and stratified-annular flow transition at higher pressure. One the other hand, it slows down the liquid below the crest, and it makes the interface wave crest unstable and split for the vortex shedding behind the wave crest, which accounts for flow regime transition in gas-liquid two-phase flows in pipelines. As a result, stratified-intermittent flow transition is depressed and delayed. The pressure influence on the liquid film profile is analyzed, and relationships between film thickness and dimensionless numbers are studied, such as liquid Weber number and gas Weber number. Friction factors on different interfaces at high pressure are studied, and new empirical formulas are deduced.

Experimental Study on Gas–Liquid Two-Phase Flow Upstream and Downstream of U-Bends

In this study, the influence of U-bends on the flow and pressure propagation characteristics of a gas–liquid two-phase flow in upstream and downstream straight pipes was investigated experimentally. The superficial velocities of the gas and liquid are 0.18–25.11 m/s and 0.20–1.98 m/s, respectively, covering plug flow, slug flow, and annular flow. The experiments were conducted in U-tubes with inner diameters of 9 mm and 12 mm and with a curvature ratio of 8.33. The U-tube was C-shaped. The pressure fluctuations at the axial measurement points of the straight tubes were measured. Flow images of the distal straight tubes and U-bends were obtained. The disturbance from U-bends in the two-phase flow in the vicinity of the bend is very obvious. The perturbation from U-bends in the fluid in the adjacent straight tubes is highly related to the incoming flow pattern. The slug flow has the most significant influence, whereas the effects of the plug and annular flows are small. Fundamentally, it mainly depends on the weight relationship between the gravity, centrifugal force, and inertial force of the gas–liquid two-phase fluid. The pressure fluctuation propagates in the form of a wave with the same dominant frequency in the straight pipes of the U-tube. The pressure pulsation energy in the straight tubes strengthens with decreasing distance from the 180° return bend. In addition, the pressure fluctuation energy downstream of the U-bend is greater than that upstream of the return bend.

Two-Phase Stereo-PIV measurement techniques for Gas-Liquid Two-Phase flow — Methodology and validation

The bubbles and three-component (3C) velocity are of great significance in the investigation of gas–liquid two-phase flows. In this study, two kinds of two-phase stereo-PIV measurement techniques, based on optical phase discrimination and image phase discrimination, were proposed to realize the simultaneous measurement of 3C velocity and bubbles. The corresponding image processing and velocity reconstruction methods were developed. Three validation tests were conducted to verify the accuracy and feasibility of the proposed techniques. The measurement results of the pipe flow and the motor-driven swirl flow illustrate the sufficient accuracy of the techniques. Finally, the techniques were applied to the vertical bubbly pipe flow and the rising bubble in the bubble column. The results show that both OPD and IPD methods have successfully obtained the three-dimensional velocity and bubbles. Through comparison, the IPD method was greatly recommended for two-dimensional (2D) measurement due to its low equipment requirements, simple setups, and high spatial resolution.

Gas–Liquid Two-Phase Flow Measurement With Throat-Extended Venturi Meter Based on Differential Pressure Ratios and Fluctuations

Gas–Liquid Two-Phase Flow Measurement With Throat-Extended Venturi Meter Based on Differential Pressure Ratios and Fluctuations

Joint Recurrence Network-Based Dynamic Parameter Measurement of Gas–Liquid Two-Phase Flow

Joint Recurrence Network-Based Dynamic Parameter Measurement of Gas–Liquid Two-Phase Flow

Numerical Model of Two-Phase Gas–Liquid Streamer Discharge in Ester-Based Insulating Oil Under Impulse Voltage

Numerical Model of Two-Phase Gas–Liquid Streamer Discharge in Ester-Based Insulating Oil Under Impulse Voltage

Void Fraction Measurement of Gas-Liquid Two-Phase Flow Based on Capacitance Sensor

Void Fraction Measurement of Gas-Liquid Two-Phase Flow Based on Capacitance Sensor

Explanation of Deep Learning Model with SHAP for Measuring the Flow Rate of Gas-Liquid Two-Phase Flow

Explanation of Deep Learning Model with SHAP for Measuring the Flow Rate of Gas-Liquid Two-Phase Flow

MODELING OF TWO-PHASE GAS-LIQUID SLUG FLOWS IN MICROCHANNELS

Even though numerical simulation of two-phase flows in microchannels has been attempted by many investigators, most efforts seem to have failed in correctly capturing the flow physics, especially the slug-flow regime characteristics. The presence of a thin liquid film in the order of 10 μm around the bubble (sometimes called gas pocket or gas slug) may be a contributing factor to the above difficulty. Typically, liquid films have a significant effect on the flow field. Thus, there is a strong motivation to employ numerical simulation methods to avoid some of the experimental difficulties. In this paper, the characteristics of two-phase slug flows in microchannels are calculated with the help of the volume-of-fluid (VOF) method. Formation of the slugs for different superficial velocities, capillary numbers, and gas volume fractions are investigated. The minimum mesh resolution required to capture the liquid film surrounding the gas bubble is reported employing a dynamic mesh adaptation methodology with interface tracking. Results are shown to be in good agreement with experimental data and empirical correlations.

Multi-size Numerical Simulation of Bubbles on Gas-liquid Two-Phase Flow in a Centrifugal Pump

Multi-size Numerical Simulation of Bubbles on Gas-liquid Two-Phase Flow in a Centrifugal Pump

IMPROVEMENT OF METHODS FOR CALCULATION OF GAS-LIQUID SLUG OF FLOW IN PIPELINES

To calculate pressure losses during transportation of gas-liquid fluids in flowlines, it is important to correctly estimate the effective density and viscosity of the mixture, which increases the accuracy of calculating the tangential stresses required to determine hydraulic pressure losses at the liquid-wall boundary. The determining parameter when calculating the effective values of the density and viscosity of the mixture is the coefficient liquid holdup in the cross section of the pipeline. The article analyzes the applicability of empirical methods for modeling two-phase gas-liquid currents when calculating liquid holdup in slug body of a intermittent (slug) flow in horizontal pipelines. A description is given of the mechanistic approach proposed by Zhang to calculate the liquid holdup in the slug body used in one of the most famous modern models of gas-liquid flow — TUFFP Unified model. The results of calculating the actual liquid holdup in the slug body using the TUFFP Unified model hydrodynamic model are presented, showing good consistency of the calculated data with experimental ones for vertically located pipelines, and unsatisfactory consistency for currents in horizontal pipes. The purpose of the article is to improve the methods of calculating the gas-liquid slug structure of the current using the TUFFP Unified model, by improving the accuracy of calculating the liquid holdup in the slug body at the horizontal location of the flowline. The proposal to use in the TUFFP Unified model a new approach to assessing the stable diameter of the gas bubble of the dispersed-bubble flow regime in the body of a liquid slug made it possible to increase the reliability of calculating the liquid holdup in the slug body with a horizontal location of the pipeline.

Experimental and CFD modeling of a progressive cavity pump (PCP) using overset unstructured mesh part 2: Two-phase flow.

In oil well operations, accurate modeling of two-phase liquid-gas flow in Progressive Cavity Pumps (PCPs) is vital. This study aimed to comprehensively analyze such flow in a metal-metal PCP using computational fluid dynamics (CFD) simulations validated by experimental data. The methodology applied to the High-Resolution Interface Capturing (HRIC) scheme is to compute the convective transport of phase fractions, yielding insights into the intricate dynamics of these flows. Validation was achieved using laboratory-acquired data and comparisons with extant publications. The findings confirmed the CFD simulations' alignment with field data for two-phase liquid-gas flows. Gas compression and effective viscosity gradient were crucial for accurate pump performance prediction. An investigation into the “gas seal” phenomenon using the Eulerian Multiphase Model elucidated the distinct separation of gas and liquid phases. The influence of the gas volume fraction on pump metrics like torque, power, and efficiency was explored, with CFD predictions exhibiting less than 8% error. The study underscores the pivotal role of CFD tools in predicting pump behavior under diverse conditions. It advances our understanding of two-phase flows in oil wells, especially regarding the gas's impact on pump components. This research offers the oil industry a refined modeling tool, enhancing the comprehension of oil well pump dynamics.

Machine Learning for Two-Phase Gas-Liquid Flow Regime Evaluation Based on Raw 3D ECT Measurement Data

Machine Learning for Two-Phase Gas-Liquid Flow Regime Evaluation Based on Raw 3D ECT Measurement Data

Study on the Influence of the Microgravity on the Flow and Heat Transfer Characteristics of Gas–Liquid Two-Phase Flow in Evaporator

Study on the Influence of the Microgravity on the Flow and Heat Transfer Characteristics of Gas–Liquid Two-Phase Flow in Evaporator

Analysis of two-phase gas-liquid flow in an Electric Submersible Pump using A CFD approach

This study comprehensively analyzes a mixed-flow Electric Submersible Pump's (ESP) performance under challenging conditions of low flow rates and high gas fractions. The research leverages a computational model built on the Eulerian-Eulerian methodology, adeptly solving the 3D incompressible Navier-Stokes equations for each phase. To ensure an encompassing depiction of the flow dynamics within the ESP, the model considers critical parameters such as the bubble diameter and interphase forces, including drag, lift, and virtual mass force.Key findings reveal that the ESP's performance deteriorates markedly under the studied conditions. One of the primary influencers is the phenomenon of gas locking, where gas accumulation within the impeller hampers the consistent flow of liquid, thereby degrading the pump's efficiency. In addition, the model delineated the occurrence of the surging phenomenon across diverse gas volume fractions and rotational speeds, which further exacerbates the reduction in the ESP's performance. Intriguingly, the bubble diameter was identified as a decisive factor, especially at minuscule flow rates. Large bubble diameters instigate the formation of gas pockets on the suction side of the vane, culminating in a segregated flow pattern and further declining pump efficiency.On the other hand, the drag force is the primary interaction force between phases of gas-liquid flow. Other interfacial forces, such as lift and virtual mass force, change the pump's performance but do not affect the gas flow and distribution patterns for a one-stage configuration. Results show that the Schiller-Neuman drag coefficient offers a better fit than the Bozano-Dente coefficient.Conclusively, the study underscores the indispensable role of nuanced computational models in elucidating the intricate flow dynamics within ESPs, especially under conditions fraught with operational challenges. The insights gleaned enrich our understanding of ESP performance dynamics and provide a roadmap for designing more resilient and efficient pumping systems in the future.

Scaling two-phase gas-liquid flow in horizontal pipes

Two-phase flow in pipelines is analyzed by experimental facilities and also numerical analysis. The experimental facilities are designed by scale-down field pipelines. Therefore, the accuracy of experimental data is strongly dependent on the scaling method. In this research, an approach for downscaling field pipelines into experimental facilities is proposed. The fluid flows in different scales for various flow patterns including Stratified, Stratified Wavy, Slug, Plug and Bubbly are numerically simulated and validated against full-scale experimental data. The results of the scaled-down model simulation are in excellent agreement with the full-scale facilities, affirming the robustness of the downscaling method. This research enhances the understanding of scaled-down experiments for various flow conditions.

A New Flow Pattern Identification Method for Gas–Liquid Two-Phase Flow in Small Channel Based on an Improved Optical Flow Algorithm

A New Flow Pattern Identification Method for Gas–Liquid Two-Phase Flow in Small Channel Based on an Improved Optical Flow Algorithm

Assessment of the Void Fraction Correlations for Gas–Liquid Two-Phase Flows in Pipeline-Risers

In the past decades, studies on a void fraction of gas–liquid two-phase flow have mainly focused on straight pipes, while voidage in pipeline-riser flows have been largely neglected. In this work, the void fraction of gas–liquid two-phase flow in pipeline-riser was investigated. The test loop consists of a 12 m horizontal pipe, followed by a 2 m downward inclined pipe, and ended at a riser. Both vertical riser and catenary riser were used in the experiment. Slip in severe slugging and annular flow was more pronounced than in bubbly flow. The transition from the mixed to the separated flow occurs at gas–liquid volumetric flow rate ratio equals to 0.8. However, the separated flow forms when the gas–liquid volumetric flow rate ratio is greater than 0.9 for catenary riser. A total of 28 correlations for predicting the void fractions were evaluated with the experimental data. The Mishima and Hibiki correlation was found to be the most accurate among the studied correlations, predicting 68.5% and 69.3% of the measured data within ±30% for vertical and catenary riser, respectively. A new correlation considering the effect of the elbow is still needed for more accurate prediction of void fraction in pipeline-riser.