Gas-liquid Multiphase Flow Research Articles

Numerical simulation on gas–liquid multiphase flow behavior under coupling effects of annular gas curtain and swirling flow at tundish upper nozzle

Numerical simulation on gas–liquid multiphase flow behavior under coupling effects of annular gas curtain and swirling flow at tundish upper nozzle

Performance evaluation on full-scale proton exchange membrane fuel cell: Mutual validation of one-dimensional, three-dimensional and experimental investigations

The coupling of multiple physical processes such as gas multi-component transport, gas–liquid multiphase flow, and electrochemical reactions within the proton exchange membrane fuel cell (PEMFC) makes its hydrothermal management exceptionally complicated. Therefore, the complex heat and mass transfer processes in the full-scale PEMFC are investigated in single cell with single channel serpentine flow field (FF). Firstly, the reliability of the proposed three-dimensional (3D) computational fluid dynamics (CFD) numerical model is verified by using the experimental test results of a single cell. Among them, the trend of simulation and experiment performance curves is consistent, and the minimum error of current density is 0.665%. Secondly, the ionomer model of cathode catalyst layer (CCL) is considered in CFD simulation, which is closer to the actual working condition of fuel cell (FC). The resistance of ionomer film and liquid water film mainly affects the diffusion rate of oxygen in CCL, resulting in a decrease in both current density values and power density values. Subsequently, the electrochemical reaction platform of one-dimensional (1D) FC is constructed, and the performance curves of multi-scale FCs are analyzed. The results demonstrate that the error of stack level is the largest, followed by single cell and single channel is the smallest. Finally, the 1D numerical model and the 3D PEMFC multiphase flow CFD model are utilized to investigate the cell voltage losses in the bionic spider flow field, the variable path flow field, and the serpentine flow field, respectively, under different operating conditions.

Numerical investigation of SO2 absorption into a droplet: deformation and internal flow facilitating mass transfer

The SO2 absorption into a droplet falling freely is investigated numerically based on a detailed three-dimensional mode in this work. Gas-liquid multiphase flow simulations coupled with interphase mass transfer are performed using the coupled Level-set and Volume of Fluid method (CLSVOF) to trace the gas-droplet interface. The results of simulation reveal that droplet would deform and deviate from the standard sphere during falling, with an approximately 5.6 % increase in surface area under the discussed working conditions. The evolution mechanism of the internal circulation in the droplet is clarified: the increase in the relative velocity of gas-droplet facilitates the formation and intensification of the internal circulation in the droplet. As the internal circulation develops into the stable stage, the convective mass transport would dominate the mass transfer process and promote the mass transfer. The distribution laws of the local mass transfer rate and coefficient over the droplet surface are found analogous to the typical case of heat transfer around a sphere. Finally, considering the effects of both droplet deformation and internal circulation on mass transfer concurrently, the variation of Sh as a function of Reynolds number is obtained, which appears the same trend but yields slightly higher values compared to the results of empirical correlations.

Machine learning-aided characterization of microbubbles for venturi bubble generator

The characterization of microbubbles for venturi tube is important for the associated industrial applications, but still challenging due to the coupling effects of numerous operating factors. Here, we report a machine learning (ML)-aided approach for predicting the characteristics of microbubbles generated by venturi tube. Full factorial design of experiments (DOE) was first carried out, followed by the image post-processing to obtain multi-dimensional dataset. After data cleaning, MLP (Multi-Layer Perception), random forest (RF) and Catboost models were trained to correlate the Sauter mean diameter (ds) to five operating features, namely, throat-to-outlet ratio β, divergent angle θ, gas-to-liquid ratio α, gas Reynolds number Reg and liquid Reynolds number Rel. All three ML models provide excellent predictability on ds, while the Catboost model displays the best extrapolation performance in three investigated scenarios. Internal importance analysis shows that the throat size and Reg play the greatest and least influence on ds, respectively. We also explored the mathematical fitting approach based on obtained experimental dataset. The results show that ML models deliver improved predictive performance over mathematical model, but the latter provides better mechanistic interpretability. This work demonstrates the great potential of ML in the gas–liquid multiphase flow.

Study on Optimization of Nozzle Angle for Oxygen-Rich Side-Blown Lead Melting Furnace

Taking an oxygen-rich side-blown lead melting furnace made by a company as the research object, the three-dimensional design software Solidworks was used to construct a model at an equal scale, and established a physical model which is in line with the actual system. Based on the determination of the physical properties of the slag phase and metal phase in the furnace, the VOF multiphase flow model and standard turbulence model in FLUENT were used to simulate the gas–liquid multiphase flow. By adjusting the different inclination angles of the spray gun, we analyzed the distribution changes of key indicators, such as the flow field, average turbulent kinetic energy and gas content in the furnace. At the same time, it was found that the turbulent kinetic energy in the middle of the furnace was large, which could strengthen the winding effect of the material and the best arrangement. The gas content of the upper part of the oxygen gun was high, and the gas content in the middle of the furnace was higher than that in the wall area on both sides and showed a gradual downward trend. If the inclination angle of the spray gun is too small, the agitation of the lower melting area is not strong enough, On the contrary, if the inclination angle is too large, the local flow rate of the sedimentation area increases and the gas content is low. The optimal tilt angle of the spray gun is between 10° and 15°.

A new gas–liquid mass transfer enhancement method for a multi-downcomer sieve tray: Bubble breakup by falling droplets

Gas–liquid multiphase flows are a significant phenomenon in many chemical processes. Smaller bubbles have higher mass transfer efficiency, so this work proposes a new gas–liquid mass transfer enhancement method for a multi-downcomer sieve tray: bubble breakup by falling droplets. The motion of the bubbles was studied with computational fluid dynamics and particle image velocimetry. The main depth of influence of droplets was determined to be around 15 mm. A droplet breaks a bubble better when the gas velocity is 0.34–0.42 m/s. The droplet enters the liquid layer and acts directly or indirectly on the bubble, increasing its residence time and surface area after large bubbles impacted by droplets are split into smaller ones. The flow field around the bubble changes, the pressure and velocity inside the bubble increase, and the surface renewal accelerates. CO2 absorption experiments show that droplet-broken bubbles enhance the gas–liquid mass transfer effect.

Evolution of Gas-Liquid Two-Phase Flow in an M-Shaped Jumper and the Resultant Flow-Induced Vibration Response

The vibration excited by gas-liquid multiphase flow endangers the structural instability and fatigue life of subsea jumpers due to the cyclic behavior. In this paper, the multiphase flow-induced vibration (MFIV) of an M-shaped jumper is numerically investigated using a two-way fluid-structure interaction (FSI) approach. The effect of gas-liquid ratios (β) ranging from 1:1 to 1:5 is examined with a fixed flow velocity of 3 m/s, and the influence of mixture velocity (vm) in the range 2–6 m/s is evaluated with a gas-liquid ratio of 1:1. The numerical results reveal the detailed flow evolution of the gas-liquid mixture along the jumper. With inflow of slugs, the pattern successively experiences the slug flow, wavy flow, imperfect annular flow, stratified flow, churn flow, wavy flow and imperfect annular flow in the pipe segments when β = 1:1 and vm = 3 m/s. This development of mixture flow is significantly altered by changing either the gas-liquid ratio or the mixture velocity. In comparison with the flow evolution in a stationary jumper, the pattern in each pipe segment is not been substantially changed due to the limited response amplitude of order of 10−3D (D is the outer diameter of the jumper). Due to the complex flow evolution, the pressure acting on the six bends of the jumper fluctuate in multiple frequencies. Nevertheless, the dominant fluctuation frequency is approximately equal to the inflow slug frequency. Moreover, the inflow slug frequency also dominates the in-plane response of the jumper. Both the in-plane and out-of-plane responses of the jumper exhibit spatial-temporal variation characteristics. The most vigorous oscillation occurs at the midspan of the jumper. As β is reduced, the out-of-plane response of the jumper midspan is suppressed while the in-plane response is enhanced. In contrast, both the in-plane and out-of-plane oscillations of the jumper midspan are amplified with the increase of vm.

Foam stability: The key to inhibiting slug generation in gas–liquid flow

Surfactant-based foam drainage technology is a favored method of liquid accumulation removal, and it has been demonstrated as an efficient way to improve gas production efficiency. However, foam properties are extremely complex and the same surfactant can produce foam systems with widely varying properties under different environmental conditions. This has a huge impact on the multiphase flow containing foam and thus on the efficiency of fluid removal. To further explore the influences of changing foam properties on the flow characteristics and the liquid-carrying capacity of foam, this study experimentally investigated the gas–liquid multiphase flow containing different foams in a hilly terrain pipeline with different properties in pipelines by adding SDS surfactant and MgCl2. The results show that the foam stability can significantly affect the gas–liquid multiphase flow characteristics. Adding MgCl2 enhances the stability of SDS foam. This narrows the range of intermittent flow conditions and leads to a significant fall in the critical gas velocity corresponding to the transition from intermittent to separated flow. Meanwhile, under the same gas and liquid velocities conditions, the foam with higher stability has a more pronounced suppression effect on the velocity of liquid in the upward inclined section, both the slug velocity and the liquid reflux velocity. The reduction in the holding rate also indicates that a more-stable foam improves the liquid-carrying capacity of gas and the discharge efficiency. In addition, as the gas velocity increases, the enhanced stability promotes the transition of the flow pattern from stratified to annular flow, resulting in a remarkable increase in the pressure drop gradient. This suggests that a more stable foam system is suitable for environments with lower gas velocities.

PEMYH için COMSOL'da Üç Boyutlu Çoklu Akış Modeliyle Altın Oran Yöntemi ile Oksijen ve Hidrojen Giriş Hızlarının Optimizasyonu

A three dimensional (3D), gas-liquid multi-phase flow and transport model in COMSOL Multiphysics has been developed to simulate flow and transport phenomena in a proton exchange membrane fuel cell (PEMFC) with several operational parameters. The effects of changes in oxygen and hydrogen input velocities on concentration change at electrodes, current density in polymeric membrane and cell performance have been investigated in PEMFC. The simulations, made in COMSOL for numerical method, were presented with an emphasis on the physical and fundamental insight afforded by distributions of velocity vector, local current density, overpotential, oxygen and water concentrations. Using Golden Section Method, optimization of the change in the speed vector was made based on the numerical models for velocity values. Results showed that computational and numerical methods are in great harmony. The polarization curve, which is used as a measure of efficiency in cell performance, were supportive with results. The data show that the power density obtained for the optimum model is higher, with such a model performance of 92.87%. Compared to the currently used PEMFC, while hydrogen saving achieved between 4.2% and 7.1%, electrical efficiency increase were between 1% and 2.4%.

Comparison of empirical models using experimental results of electrical submersible pump under two-phase flow: numerical and empirical model validation

Electrical submersible pumps (ESPs) dealing with gas-liquid multiphase flow face great challenges in the oil and gas industries. The main problem is caused by the accumulation of air bubbles inside the ESP, which degrade the pump performance ranging from minor to major degradation (surging and gas-locking). Several empirical models have been developed to predict head and surging mechanisms. However, the feasibility and versatility of these models are still questionable. Therefore, this study focuses on experimental analysis and their comparison with the existing empirical models (developed to predict Head and surging characteristics under two-phase flow conditions) to examine their validity and versatility in predicting the multiphase performance of pumps. The comparison showed that some models agree well with the given test analysis. However, some models either underestimate or overestimate the predicted values because most of these models were established for high inlet pressure, no water but oil and CO2, several impeller and diffusers, different rotational speed, and different pump geometries. Moreover, this study also compares test results with CFD simulations (using Euler-Euler two-fluid model) and shows that the experimental results are consistent and reliable. Furthermore, this study provides a detailed and close insight into the different aspects of empirical models to check whether they can be applied for wider applications or are limited to the type they were developed.

A comparative study of the cumulant lattice Boltzmann method in a single-phase free-surface model of violent flows

Many coastal and ocean engineering flows, such as tsunamis inundating urban areas, tend to be violent. The characteristics of these damaging flow fields are three-dimensional, highly non-linear and non-hydrostatic. A fully three-dimensional free-surface fluid model is required to simulate such a flow field. Fluid simulations in the field of coastal engineering are often large-scale since large areas are the subject of the simulations. The numerical model must be not only accurate but also efficient. In recent years, the lattice Boltzmann method (LBM) has attracted much attention as a novel simulation method and has been successfully applied to various engineering fields. The LBM calculates complex phenomena in a simple framework. The density field determines the pressure field with the equation of state. This means that the LBM does not have to solve the pressure Poisson equation. However, the existing gas–liquid multi-phase flow models that employ the LBM have a critical problem. Pressure calculations with large density ratios easily become unstable, and the application of these models to violent flow fields is limited. The single-phase free-surface fluid model provides good approximations for flow problems in which the gas dynamics can be neglected. Moreover, the cumulant LBM has attracted attention because it has excellent numerical stability even for high Reynolds number flows. The single-phase free-surface flow model using the cumulant LBM is a suitable approach for simulating violent flow fields in coastal engineering. In this study, we propose a single-phase free-surface flow model based on the cumulant LBM using the volume-of-fluid (VOF) model to capture the interface. We demonstrate that the cumulant LBM is stable under violent flows and reproduces the density field well compared with the traditional single relaxation time model. We find that a larger bulk viscosity can reduce the numerical oscillation of the impact pressure acting on a structure, although a bulk viscosity that is too large reduces the accuracy and stability. The results of the proposed model are in good agreement with previous experimental results.

Sub-grid Scale Modelling and a-Posteriori Tests with a Morphology Adaptive Multifield Two-Fluid Model Considering Rising Gas Bubbles

The predictive simulation of gas–liquid multiphase flows at industrial scales reveals the challenging task to consider turbulence and interfacial structures, which span a large range of length scales. For simulation of relevant applications, a hybrid model can be utilised, which combines the Euler–Euler model for the description of small interfacial structures with a volume-of-fluid model as a scale-resolving multiphase approach. Such a hybrid model needs to be able to simulate interfaces, which are hardly resolved on a coarse numerical grid. The goal of this work is to improve the prediction of interfacial gas–liquid flows on a numerical grid with comparably large grid spacing. From the low-pass filtering of the two-fluid model five unclosed sub-grid scale terms arise. The convective and the surface tension part of the aforementioned contributions are individually modelled with multiple closure formulations. Those models are a-posteriori assessed in cases of two- and three-dimensional gas bubbles rising in stagnant liquid. It is shown, that the chosen closure modelling approach is suitable to improve the predictive power of the numerical model utilised in this work. Hence, simulation results on comparably coarse grids are changed towards results obtained with higher spatial resolution.

A Review on Gas-Liquid Mass Transfer Coefficients in Packed-Bed Columns

This review provides a thorough analysis of the most famous mass transfer models for random and structured packed-bed columns used in absorption/stripping and distillation processes, providing a detailed description of the equations to calculate the mass transfer parameters, i.e., gas-side coefficient per unit surface ky [kmol·m−2·s−1], liquid-side coefficient per unit surface kx [kmol·m−2·s−1], interfacial packing area ae [m2·m−3], which constitute the ingredients to assess the mass transfer rate of packed-bed columns. The models have been reported in the original form provided by the authors together with the geometric and model fitting parameters published in several papers to allow their adaptation to packings different from those covered in the original papers. Although the work is focused on a collection of carefully described and ready-to-use equations, we have tried to underline the criticalities behind these models, which mostly rely on the assessment of fluid-dynamics parameters such as liquid film thickness, liquid hold-up and interfacial area, or the real liquid paths or any mal-distributions flow. To this end, the paper reviewed novel experimental and simulation approaches aimed to better describe the gas-liquid multiphase flow dynamics in packed-bed column, e.g., by using optical technologies (tomography) or CFD simulations. While the results of these studies may not be easily extended to full-scale columns, the improved estimation of the main fluid-dynamic parameters will provide a more accurate modelling correlation of liquid-gas mass transfer phenomena in packed columns.

MultiUQ: A software package for uncertainty quantification of multiphase flows

multiUQ is a novel tool that simulates gas-liquid multiphase flows and quantifies uncertainty in results due to variability about fluid properties and initial/boundary conditions. The benefit over a typical deterministic solver is that inexact information, such as variability in fluid properties or flow rates, can be included to determine the affect on simulation solutions. It is common to deploy non-intrusive methods which utilize many solutions from a deterministic solver to generate a distribution of possible results. Contrarily, multiUQ uses an intrusive uncertainty quantification method wherein variables of interest are functions of space, time, and additional uncertainty dimensions. The intrusive solver is run once, giving a distribution of solutions as an output, as well as desired statistics. We use polynomial chaos to create the stochastic variables, which represent a distribution of values at each grid point. The stochastic variables are substituted into the incompressible Navier-Stokes equations, which govern the stochastic fluid dynamics. A stochastic level set is used to capture the distribution of interfaces that are present in an uncertain multiphase flow. multiUQ is written in Fortran and uses a message passing interface (MPI) for parallel operation. Given the many applications of multiphase flows, including open flows, hydraulics, fuel injection systems, and atomizing jets, there is a massive potential benefit to calculating uncertainty information about these flows in a cost-effective manner. Program summaryProgram Title: multiUQCPC Library link to program files:https://doi.org/10.17632/yp5pkd5x89.1Developer's repository link:https://bitbucket.org/markowkes/multiuqLicensing provisions: GPLv3Programming language: Fortran 95/2003Supplementary material: Wiki available at repository link.Nature of problem: Performing uncertainty quantification on simulations of gas-liquid multiphase flows to understand the impact of input uncertainty on simulation results.Solution method: This software utilizes an intrusive approach to uncertainty quantification of multiphase flows. Deterministic variables are expanded to include an added uncertainty domain by way of polynomial chaos. Stochastic Navier-Stokes govern the flow field in an incompressible one-fluid approach. Multiphase flows are created by coupling a stochastic level set and surface tension.

Research Progress and Prospects of Multi-Stage Centrifugal Pump Capability for Handling Gas–Liquid Multiphase Flow: Comparison and Empirical Model Validation

The working capability of multi-stage pumps, such as electrical submersible pumps (ESPs) handling multiphase flow, has always been a big challenge for petroleum industries. The major problem is associated with the agglomeration of gas bubbles inside ESP-impellers, causing pump performance degradation ranging from mild to severe deterioration (surging/gas pockets). Previous literature showed that the two-phase performance of ESPs is greatly affected by gas involvement, rotational speed, bubble size, and fluid viscosity. Thus, it is necessary to understand which parameter is actually accountable for performance degradation and different flow patterns in ESP, and how it can be controlled. The present study is mainly focused on (1) the main parameters that impede two-phase performance of different ESPs; (2) comparison of existing empirical models (established for two-phase performance prediction and surging initiation) with our single-stage centrifugal pump results to determine their validity and working-range; (3) gas-handling techniques applied to enhance the multiphase performance of ESPs. Firstly, it aims at understanding the internal flow mechanism in different ESP designs, followed by test studies based on empirical models, visualization techniques, bubble-size measurements, and viscosity analysis. The CFD-based (computational fluid dynamics) numerical analysis concerning multiphase flow is described as well. Furthermore, gas-handling design methods are discussed that are helpful in developing the petroleum industry by enhancing the multiphase performance of ESPs.

Atomization Mechanism of Internally Mixing Twin-Fluid Y-Jet Atomizer

AbstractThe atomization mechanism of the gas-liquid multiphase flow through an internally mixing twin-fluid Y-jet atomizer has been studied by examining both the internal and external flow patterns...

Numerical simulation of the propagation of pressure waves in water during the collapse of a spherical air cavity

Numerical simulation of the collapse of a spherical gas cavity in a liquid under the influence of a pressure drop is performed. The unsteady motion of a viscous compressible fluid is described by the equations of continuity, momentum, and energy, supplemented by Menter’s SST model. The VoF approach was used to track the interface of the gas–liquid multiphase flow. The problem was solved using OpenFOAM software. Comparison of the obtained results with the known data of other authors was carried out. In experiments, the initial radius of the spherical cavity varied from 0.01 to 0.09 m, and the gas pressure varied from 0.05 to 0.5 MPa at a constant liquid pressure of 7 MPa. The dependences of the radius of the gas cavity, the velocity of the interface, and turbulent kinetic energy on time were obtained, and the shape of the cavity during the implosion process was calculated. The influence of the gas pressure and the radius of the spherical cavity at the initial time on the maximum pressure at the control point was analyzed.

A gas kick early detection method outside riser based on Doppler ultrasonic wave during deepwater drilling

The feasibility of gas kick early detection outside the riser was analyzed based on gas-liquid multiphase flow theory. Then an experimental platform for gas kick early detection based on Doppler ultrasonic wave was established and the propagation experiments in two-phase flow of gas-water (sucrose solutions) were conducted. The time and frequency domains of the Doppler ultrasonic wave signals during the experiments were analyzed. The results show that: (1) No matter the pump was on or off, the detected average Doppler ultrasonic signal voltage increased first and then decreased with the increase of the gas void fraction, and had a quadratic function relation with gas void fraction, so the average voltage change of the monitored signals can be used to deduce the approximate gas void fraction. The Doppler ultrasonic wave signal voltage was significantly reduced in magnitude and variation in the solution with higher viscosity, and the viscosity has stronger impact on the magnitude of signal than density. (2) When the pump was stopped, the Doppler shift increased with the increase of gas void fraction, and the two showed a nearly linear relation, so the detected amount of Doppler shift can reflect the variation of gas void fraction quantitatively. When the pump was on, the sound energy produced by frequency converter had a more significant impact on amplitude spectrum than gas void fraction, so it is impossible to determine whether gas kick occurs by frequency domain signal analysis. (3) This method is a non-contact measurement, with no contact with the drilling fluid and no disruption to the drilling operation. It can quantitatively characterize the gas void fraction according to the change of Doppler ultrasonic signal, enabling earlier detection of gas kick.

Systematic Frequency and Statistical Analysis Approach to Identify Different Gas–Liquid Flow Patterns Using Two Electrodes Capacitance Sensor: Experimental Evaluations

This work proposes a method to distinguish between various flow patterns in a multiphase gas–liquid system. The complete discrimination between different flow patterns can be achieved by mapping the corresponding frequency and statistical parameters. These parameters are usually obtained from further analysis conducted on the signal data of the utilized sensor. The proposed technique is based on establishing interrelationships between these parameters, namely the mean (m), the standard deviation ( σ ¯ ), power spectral density (PSD), the width of the characteristic frequency peaks (Δƒ), the skewness ( γ 1 ) and the kurtosis ( γ 2 ). Therefore, a relatively simple electrical capacitance sensor with two electrodes was designed and implemented on a two-phase flow apparatus with a circular pipe. The experimental operating conditions comprised of different combinations of air–water superficial velocities at three inclinations (i.e., horizontal, upward 15° and upward 30°). This research discusses in specific the analysis underlying flow patterns identification method and the rationale for selecting the proposed approach. The results showed that some parameters found to be more valuable than others such as m, σ ¯ and Δƒ. Besides, combining two sets of these statistical graphs which are (a) σ ¯ vs. Δƒ with Δƒ vs. m (or Δƒ vs. total power), (b) Δƒ vs. total power with γ 1 vs. σ ¯ (or γ 2 vs. σ ¯ ), and (c) σ ¯ vs. m with Δƒ vs. m (or Δƒ vs. total power), allowed all flow patterns field to be identified clearly at all inclinations. It is therefore concluded that for any gas–liquid multiphase flow system, the reported approach can be used reliably to discriminate between different generated flow patterns.

Simulation of thermal spray process of a three phase flow calculation with substrate temperature of 300K

We propose a particle method (MPS method) which can analyse the large deformation, splitting and coalescence of liquid as a new calculation method and a gas-liquid coupling method of finite volume method which can stably solve the compressible flow. By doing this, we aim to solve the interface resolution problem in the interface capture method and to establish a complicated gas-liquid multiphase flow analysis method that can deal with large deformation case. At the temperature of 300K, the validity of the flow field is consistent with the reference. The processes from the acceleration and deformation of a droplet to the solidification of the droplet on a substrate are successfully being observed. The shape of the splat is influence by substrate temperature.