Horizontal Gas-liquid Two-phase Flow Research Articles

Measurement method of gas holdup in horizontal gas-liquid two-phase flow based on fiber-optic probe array

Aiming at the problem of gas holdup measurement in horizontal shale gas wells with low flow rates, a fiber-optic probe array sensor for horizontal gas-liquid stratified flow is designed and developed. The Fluent fluid volume method is used to establish a simulation model of gas-liquid two-phase flow in the horizontal collecting pipe, and a study on the flow characteristics and flow patterns in the gas-liquid two-phase flow in the horizontal collecting pipe with low gas flow is carried out. Based on the acquisition of the fluid flow pattern is stratified flow characteristics, the design of the fiber-optic probe array structure with different numbers and positions of the probes, and the fiber-optic probe array sensor is modeled using the ZEMAX ray tracing software, simulation analysis of its response characteristics in different flow patterns and the array structure selection. Finally, based on the above research, the fiber-optic probe array sensor for gas holdup measurement is designed and developed, and the platform for gas-liquid two-phase flow is constructed and experimentally verified. The experimental results show that the developed fiber-optic probe array sensor has good applicability for gas holdup measurement under stratified flow, and the error of the measurement does not exceed 0.1.

Simultaneous measurement of velocity profile and liquid film thickness in horizontal gas–liquid slug flow by using ultrasonic Doppler method

Horizontal gas–liquid two-phase flows widely exist in chemical engineering, oil/gas production and other important industrial processes. Slug flow pattern is the main form of horizontal gas–liquid flows and characterized by intermittent motion of film region and slug region. This work aims to develop the ultrasonic Doppler method to realize the simultaneous measurement of the velocity profile and liquid film thickness of slug flow. A single-frequency single-channel transducer is adopted in the design of the field-programmable gate array based ultrasonic Doppler system. A multiple echo repetition technology is used to improve the temporal–spatial resolution for the velocity profile. An experiment of horizontal gas–liquid two-phase flow is implemented in an acrylic pipe with an inner diameter of 20 mm. Considering the aerated characteristics of the liquid slug, slug flow is divided into low-aerated slug flow, high-aerated slug flow and pseudo slug flow. The temporal–spatial velocity distributions of the three kinds of slug flows are reconstructed by using the ultrasonic velocity profile measurement. The evolution characteristics of the average velocity profile in slug flows are investigated. A novel method is proposed to derive the liquid film thickness based on the instantaneous velocity profile. The liquid film thickness can be effectively measured by detecting the position and the size of the bubbles nearly below the elongated gas bubble. Compared with the time of flight method, the film thickness measured by the Doppler system shows a higher accuracy as a bubble layer occurs in the film region. The effect of the gas distribution on the film thickness is uncovered in three kinds of slug flows.

Identification of Horizontal Gas-Liquid Two-Phase Flow Regime using Deep Learning

Two-phase flow is of great importance in various industrial processes. A characteristic feature of two-phase flow is that it can acquire various spatial distribution of phases to form different flow patterns/regimes. The knowledge of flow regime is very important for quantifying the pressure drop, the stability and safety of two-phase flow systems and it holds great significance in petrochemical and thermonuclear industries today. The objective of this study is to develop a methodology for identification of flow regime using dynamic pressure signals and deep learning techniques. Stratified, slug and annular flow regimes were simulated using a Level-Set (LS) method coupled with Volume of Fluid (VOF) method in a 6 m horizontal pipe with 0.050 m inner diameter. Dynamic pressure signals were collected at a strategic location. These signals were converted to scalograms and used as inputs in deep learning architectures like ResNet-50 and ShuffleNet. Both architectures were effective in classifying different flow regime and recorded testing accuracies of 85.7% and 82.9% respectively. According to our knowledge no similar research has been reported in literature, where various Convolutional Neural Networks are used along with dynamic pressure signals to identify flow regime in horizontal pipe. This research provides a benchmark for future research to use dynamic pressure for identification of two-phase flow regimes. This research provides a benchmark for future research to use dynamic pressure for identification of two-phase flow regimes. This study can be extended by collecting data over broader range of flow parameters and different geometries.

Gas-Liquid Two-Phase Flow Regime in a Horizontal Channel Under Transverse Vibration

This paper presents experiments carried out to study the influences of transverse vibration on horizontal gas-liquid two-phase flow. The experiments considered the transverse vibration over a wide range of vibration frequencies and vibration amplitudes. Five typical flow regimes were observed. The fluid flow conditions in steady state and transverse vibration were compared. The traditional flow regime transition lines did not match the gas-liquid flow in channel under transverse vibration. The results suggest that vibration frequency mainly affected the flow regime by promoting the aggregation of gas slug, while vibration amplitude mainly influenced the fluctuation height of the gas and liquid interface.

Characteristics of horizontal gas-liquid two-phase flow measurement in a medium-sized pipe using gamma densitometry

Two-phase flows are common occurrences in many industrial applications. The understanding of their characteristics in industrial piping systems is vital for the efficient design, optimization, and operation of industrial processes. Most of the previous experimental studies involving the use of gamma densitometers for holdup measurements in air-water mixtures are limited to smaller diameter pipes (generally regarded as those with < 50 mm in nominal diameter). Further, very few literature report experimental data obtained using gamma desitometers. This paper presents an application of a gamma densitometer in the measurement of two-phase flow characteristics in an intermediate diameter pipe (nominal diameter between 50 mm and 100 mm). Scaled air-water experiments were performed in a 17-m long, 0.0764-m internal diameter horizontal pipe. Liquid superficial velocity ranged between 0.1–0.4 m/s while gas superficial velocity ranged from 0.3 to 10.0 m/s. The measured parameters include liquid holdup, pressure gradient, flow pattern, and slug flow features. The flow patterns observed were stratified, stratified-wavy, plug, slug, and annular flows. Plug and slug flow patterns showed good agreement with established flow pattern maps. Furthermore, the slug translational velocity was observed to increase with increasing mixture velocity, as reported by previous authors, hence establishing the reliability of the instrumentation employed. The slug body length was also measured using the gamma densitometer and was found to be within the range 24–36D with a mean length of 30.6D.

Structure Detection of Horizontal Gas–Liquid Slug Flow Using Ultrasonic Transducer and Conductance Sensor

Slug flow is one of the most common flow patterns in horizontal gas-liquid two-phase flow. Structure detection of slug flow is of great significance for understanding the heat and mass transfer between phases and uncovering the mechanism of flow pattern transition. However, it is remarkably difficult to accurately measure the interface structures of slug flow with a single-sensing mode due to its multiscale characteristics. In this article, we design a combined ultrasonic and conductance sensing system that consists of a transmission ultrasonic transducer (TUT), a reflection ultrasonic transducer (RUT) and two parallel-wire conductance sensors (PWCSs). The response signals of the ultrasonic transducers and the conductance sensor for slug flows were collected in an experiment of horizontal gas-liquid flow. Based on the different measurement mechanisms of the ultrasonic transducers and the conductance sensor, the 2-D gas-liquid interfaces in slug flows were reconstructed. The experimental results demonstrate that, compared with the TUT and the PWCS, the RUT has obvious advantages in the detection of the local gas-liquid interface structure. In addition, based on the cross-correlation velocity measured by the PWCSs, the slug lengths in the gas-liquid flow were accessed. It was found that the slug lengths derived from the ultrasonic transducers and the conductance sensor indicate a good agreement and present complicated evolution characteristics due to the coalescence and crushing of the slugs.

Liquid flow measurement using phase isolation and an imaging method in horizontal gas–liquid two-phase flow

A new imaging method based on phase isolation for the liquid flow measurement of gas–liquid two-phase flow is proposed in this study. A swirler is arranged upstream to isolate two-phase fluids. As the two-phase mixture passes through it, a strong swirl flow is generated. The gas is concentrated into the center of the tube and forms a gas core while the liquid phase is pushed to the tube wall and forms a uniform liquid film, which is where the swirl core-annular flow occurs. After phase isolation, many microbubbles, which are small enough to neglect their body force, appear in the liquid film. These phase-isolation-induced microbubbles are used as tracers to represent the local velocity of the liquid flow. A CCD camera is employed to track the motion of the bubbles at the focal plane and determines the velocity at this position. Then this measured local velocity is converted to the mean velocity of the liquid film by a velocity coefficient based on the similitude principle of the velocity profile. After the flow area of the liquid film is derived from the void fraction measurement by another CCD camera, the flowrate of liquid film is determined. The velocity coefficients which express the relation between local velocity and mean velocity of liquid film are obtained by a calibration experiment. Two conventional industry CCD cameras and corresponding individual LED illuminations constitute the imaging system. The image-processing algorithm was developed using the MATLAB image toolbox. AAir and tap water are used and their superficial velocity are in the range of 3.41 m s−1 ∼ 45.15 m s−1 and 0.022 m s−1 ∼ 0.265 m s−1, respectively. The thickness of liquid film ranges from 72.75 μm to 423.11 μm and the diameter of microbubbles ranges from 11 μm to 35 μm.

Gas-liquid two-phase flow in a horizontal channel under nonlinear oscillation: Flow regime, frictional pressure drop and void fraction

This paper presents experiments carried out to study the effects of nonlinear oscillation on horizontal gas-liquid two-phase flow. The experiments considered the nonlinear oscillation over a wide range of vibration parameters. Flow regime, transition boundary, frictional pressure drop and void fraction were measured using a high-speed camera, pressure sensor and electrical impedance. Six typical flow regimes were observed. The frictional pressure drop and void fraction in steady state and nonlinear oscillation were compared. It found that the traditional predictive correlations for frictional pressure drop were accurate and matched the measured frictional pressure drop closely. On the other hand, the prediction performance of selected void fraction correlations based on three typical models was below par for the experimental conditions chosen in this paper. We further showed that predicted correlations based on flow regime could estimate measured void fraction reasonably well.

Experimental Study of Horizontal Gas-liquid Two-phase Flow in Two Medium-diameter Pipes and Prediction of Pressure Drop through BP Neural Networks

Horizontal gas-liquid two-phase flow is of crucial importance in oil-gas storage and transportation. In view of previous researches with the lack of horizontal gas-liquid two-phase flow in medium-diameter pipes (60-75 ㎜), experiments were conducted in DN 60 and DN75 at medium-high liquid velocity (50-250 m3/d) and high gas-liquid ratio (20-500 m3/m3). Comparison between flow patterns maps in DN60 and DN75 and the Taitel-Dukler model showed that only flow patterns map in DN60 agreed well. On the basis of experimental data analysis, variation laws of liquid holdup and pressure drop were determined. Besides, this paper developed a method to predict liquid holdup and pressure drop through BP neural networks. Results proved the capability of BP neural networks. The further validation can be made in practical applications.

Gas–Liquid Two-Phase Flow Velocity Measurement With Continuous Wave Ultrasonic Doppler and Conductance Sensor

Flow velocity is an important process parameter that quantifies the volume or mass flow rate as well as monitors the process safety. To nonintrusively measure the flow velocity of horizontal gas–liquid two-phase flow, an ultrasonic Doppler sensor and a conductance sensor with dedicated measurement models are presented. The air superficial flow velocity can be directly obtained and the water superficial flow velocity can be calculated through a two-fluid model for bubble flow and plug flow. For slug flow, a correlation between the phase velocity in slug body and overall superficial flow velocity was built based on a slug closure model. In order to eliminate the influence of the changing velocity profile in the fluid, the sample volume was designed to cover the whole pipe cross section by installing a two-chip piezoelectric transducer with 1-MHz center frequency at the bottom of the pipe. The conductance sensor provided water holdup estimate to compensate the velocity measurement model. Experiments were carried out in a 50-mm inner diameter pipe to verify the proposed sensor and model. Three flow patterns (bubble flow, plug flow, and slug flow) were generated by adjusting the inlet flow rate of the air and the water. The results show that the mean relative error can achieve within 5%.

Characterizing the correlations between local phase fractions of gas-liquid two-phase flow with wire-mesh sensor.

Understanding of flow patterns and their transitions is significant to uncover the flow mechanics of two-phase flow. The local phase distribution and its fluctuations contain rich information regarding the flow structures. A wire-mesh sensor (WMS) was used to study the local phase fluctuations of horizontal gas-liquid two-phase flow, which was verified through comparing the reconstructed three-dimensional flow structure with photographs taken during the experiments. Each crossing point of the WMS is treated as a node, so the measurement on each node is the phase fraction in this local area. An undirected and unweighted flow pattern network was established based on connections that are formed by cross-correlating the time series of each node under different flow patterns. The structure of the flow pattern network reveals the relationship of the phase fluctuations at each node during flow pattern transition, which is then quantified by introducing the topological index of the complex network. The proposed analysis method using the WMS not only provides three-dimensional visualizations of the gas-liquid two-phase flow, but is also a thorough analysis for the structure of flow patterns and the characteristics of flow pattern transition. This article is part of the themed issue 'Supersensing through industrial process tomography'.

Analysis of Flow-Induced Vibration Due to Stratified Wavy Two-Phase Flow

Fluctuating force induced by horizontal gas–liquid two-phase flow on 90 deg pipe bend at atmospheric pressure condition is considered. Analysis was conducted to develop a model which is capable of predicting the peak force fluctuation frequency and magnitudes, particularly at the stratified wavy two-phase flow regime. The proposed model was developed from the local instantaneous two-fluid model, and adopting guided acoustic theory and dynamic properties of one-dimensional (1D) waves to consider the collisional force due to the interaction between dynamic waves and structure. Comparing the developed model with experimental database, it was found that the main contribution of the force fluctuation due to stratified wavy flow is from the momentum and pressure fluctuations, and collisional effects. The collisional effect is due to the fluid–solid interaction of dynamic wave, which is named as the wave collision force. Newly developed model is capable of predicting the force fluctuations and dominant frequency range with satisfactory accuracy for the flow induced vibration (FIV) caused by stratified wavy two-phase flow in 52.5 mm inner diameter (ID) pipe bend.

Characterization of horizontal air–water two-phase flow in a round pipe part I: Flow visualization

As a part of characterizing the bubble interaction mechanisms and flow regime transition processes in horizontal gas–liquid two-phase flow, a flow visualization study is performed in an air–water test facility constructed from 3.81cm inner diameter clear acrylic round pipes. The test section is approximately 250 diameters in length to allow for development of the flow. Flow visualizations are performed using a high-speed video camera at 80 and 245 diameters downstream of the inlet to observe the development of the flow structures. A total of 27 flow conditions including bubbly, plug, slug, stratified, wavy, and annular flows are characterized in the present study.In highly turbulent bubbly flow conditions it is found that the distribution becomes more uniform with increasing development length through a turbulence penetration process that counters the effect of buoyancy. It is also found that plug bubbles form below a layer of small bubbles rather than at the upper pipe wall where the bubbles are most packed. In fact, it is consistently found that turbulence-based bubble interactions do not occur in the most densely packed regions as the eddies there are not large enough to effect the bubbles. Rather, bubble packing-induced coalescence occurs in these regions and contributes to the formation of plug bubbles. The newly formed plug bubbles move faster than, and ultimately pass, the smaller bubbles above due to the effect of the wall. These small bubbles are subsequently overtaken by the following plug bubble and coalesce with the nose region through a process denoted as drag-induced coalescence.

CHARACTERIZATION OF HORIZONTAL GAS–LIQUID TWO-PHASE FLOW USING MARKOV MODEL-BASED COMPLEX NETWORK

Horizontal gas–liquid two-phase flow widely exists in many physical systems and chemical engineering processes. Compared with vertical upward gas–liquid two-phase flow, investigations on dynamic behavior underlying horizontal gas–liquid flows are quite limited. Complex network provides a powerful framework for time series analysis of complex dynamical systems. We use a network generation method based on Markov transition probability to infer directed weighted complex networks from signals measured from horizontal gas–liquid two-phase flow experiment and find that the networks corresponding to different flow patterns exhibit different network structure. To investigate the dynamic characteristics of horizontal gas–liquid flows, we construct a number of complex networks under different flow conditions, and explore the network indices for each constructed network. In addition, we investigate the sample entropy of different flow patterns. Our results suggest that the network statistic can well represent the complexity in the transition among different flow patterns and further allows characterizing the interface fluctuation behavior in horizontal gas–liquid two-phase flow.

302 水平管内振動気泡流に見られる気泡挙動の特性(OS9 オーガナイズドセッション《熱・流体・エネルギー変換工学の進展》)

Abstract Earthquake is one of the most serious phenomena for safety of a nuclear reactor, especially in Japan. The behavior of nuclear reactor may be affected by the fluctuation of gas-liquid two-phase flow caused by the earthquake but not studied enough. In the project, bubbly or plug flow with flow rate fluctuation in a fixed horizontal pipe is studied experimentally. In this paper, the result on the bubbly flow under the flow rate fluctuation is shown. The flow was bubbly flow and/or plug flow in a horizontal circular pipe. The working fluids were water and nitrogen gas. The water was driven by a pump and the flow rate fluctuation was given by a reciprocating piston attached to the main flow loop. he behavior of horizontal gas-liquid two-phase flow under the flow rate fluctuation was measured by image processing and particle image velocimetry (PIV).

Liquid film circumferential asymmetry prediction in horizontal annular two-phase flow

This study considers the prediction of the degree of asymmetry in the circumferential distribution of the liquid film in the tube cross section of horizontal annular gas–liquid two-phase flow, endemic of the lower region of this flow regime near the stratified-wavy flow transition boundary. Focusing on disturbance waves as the predominant mechanism for transporting the liquid in the annular film from the bottom to the top of the tube to counterbalance the draining effect of gravity, a new prediction method for the degree of asymmetry in the annular liquid film is proposed that outperforms existing correlations. Flow pattern maps for horizontal gas–liquid two-phase flow of frequent use in the design of evaporators and condensers can thus be explicitly updated to account for both symmetric and asymmetric annular flows. The underlying experimental database contains 184 measured liquid film circumferential profiles, corresponding to 1276 local liquid film thickness measurements collected from 15 different literature studies for tube diameters from 8.15mm to 95.3mm.

Study on Interphase Force Quantitative Detection Device of Horizontal Pipe Gas-Liquid Two-Phase Flow

The paper focuses on the interphase force of the gas-liquid two-phase flow in the horizontal pipe design and designs a new interpahse force quantitative detection devices. On the basis of analyzing the physical models and the mathematical models, the devices got the more accurate differential pressure and the two-phase flow phase holdup, avoiding many factors by using the capacitance sensor which is made up of the complete closure outer electrode and flow media as the inner electrode. Finally, the devices achieved the quantitative detection of the interphase force through the differential pressure and the phase holdup. The experiments proved that the devices can better reflect the interphase force changes of the gas-liquid two-phase flow in the horizontal tube and reached the design goal very well.

Gamma-ray attenuation technique for measuring void fraction in horizontal gas-liquid two-phase flow

The measurement of void fraction is of importance to the oil industry and chemical industry. In this article, the principle and mathematical method of determining the void fraction of horizontal gas-liquid flow by using a single-energy γ-ray system is described. The γ-ray source is the radioactive isotope of 24IAm with γ-ray energy of 59.5 keV. The time-averaged value of the void fraction in a 50.0-mm i.d. transparent horizontal pipeline is measured under various combinations of the liquid flow and gas flow. It is found that increasing the gas flow rate at a fixed liquid flow rate would increase the void fraction. Test data are compared with the predictions of the correlations and a good agreement is found. The result shows that the designed γ-ray system can be used for measuring the void fraction in a horizontal gas-liquid two-phase flow with high accuracy.

Effects of Pressure on Velocity of Liquid Lumps in Horizontal Gas-Liquid Two-Phase Flow.

phase flow under a wide range of pressures from near atmospheric pressure to a highly elevated pressure of about 20 MPa. The liquid lumps of interest are liquid slugs, huge waves, disturbance waves and ephemeral large waves. Velocities were determined using time-series signals of cross-sectional mean liquid holdup which were electrically detected at two axially separated locations of the test tube. It is demonstrated how the mean values of liquid lump velocity and its standard deviation depend on the gas and liquid flow rates and pressure. It is obtained that the liquid lump velocity and its standard deviation are obviously affected by the pressure and are related to flow patterns. The comparison of liquid lump velocities between vertical upward flow and horizontal flow is also discussed.

Behavior of a Horizontal Gas-Liquid Two-Phase Flow under Microgravity. Flow Pattern and Film Construction in Annular Flow Region.

In order to predict various phenomena related to flow and heat transfer in space, it is necessary to carry out experiments under microgravity. In this paper, we describe the behavior of a horizontal two-phase flow under microgravity utilizing a drop tower 6.1m in height, which realizes microgravity conditions of less than 0.02G(G=g/g0) for about one second when the capsule is falling down. The experiment was carried out in a horizontal transparent acrylic resin tube of 10mm I. D. and 250mm length, using Freon-22 and water as the working fluid, in a superficial gas velocity range of 0.021m/s to 5.05m/s (ReG=58∼1.4×104) and a superficial water velocity of 0.022m/s to 0.456m/s (ReL=246∼5.1×103). The flow patterns obtained under microgravity were compared with other data under actual microgravity utilizing a drop tower. Furthermore, the base liquid film thickness, the height of waves and the period of waves in the region of annular flow, were obtained from a measured shape of waves. Then, the relationship between these values, gas Reynolds number and liquid film Reynolds number was obtained. Also, the void fraction under microgravity could be expressed using the distribution parameter and the Martinelli parameter.