scholarly journals Investigation of Huge Wave in Gas-Liquid Two-Phase Churn Flow

2021 ◽  
Vol 2097 (1) ◽  
pp. 012015
Author(s):  
S Zhang ◽  
Q Q Shao ◽  
B Hu ◽  
K Wang
Keyword(s):  
High Speed ◽  
Power Plants ◽  
Chemical Engineering ◽  
Industrial Applications ◽  
Management Control ◽  
Two Phase ◽  
Liquid Distribution ◽  
Transition Mechanism ◽  
Chaotic Nature ◽  
Churn Flow

Abstract Churn flow frequently occurs in power plants, chemical engineering, petroleum, and other industrial applications. Due to its chaotic nature, churn flow has a significant influence on safety and management control. As one of the essential characteristics of churn flow, depth knowledge of the huge wave is crucial for a better understanding churn flow. However, relevant studies on these issues are still in shortage because it is difficult to capture its behaviours experimentally. In this study, we employed the high-speed camera to capture the evolution and properties of huge waves under churn flow conditions in a vertical pipe. The inner diameter of the pipe is 19 mm. Based on the observation, the flooding of the falling film in churn flow is demonstrated to be the slug/churn transition mechanism. Additionally, the liquid distribution in the cross-section of the tube is provided and discussed in detail. Compared with the existing experiment data, we carefully analyze the properties of huge waves, such as frequency and amplitude.

Experimental Characterization of a Modified Airlift Pump

2014 ◽  
Author(s):  
Afshin Goharzadeh ◽  
Keegan Fernandes
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
High Speed ◽  
Water Flow Rate ◽  
High Speed Photography ◽  
Two Phase ◽  
Inner Diameter ◽  
Airlift Pump ◽  
Flow Map ◽  
Churn Flow

This paper presents an experimental investigation on a modified airlift pump. Experiments were undertaken as a function of air-water flow rate for two submergence ratios (ε=0.58 and 0.74), and two different riser geometries (i) straight pipe with a constant inner diameter of 19 mm and (ii) enlarged pipe with a sudden expanded diameter of 19 to 32 mm. These transparent vertical pipes, of 1 m length, were submerged in a transparent rectangular tank (0.45×0.45×1.1 m3). The compressed air was injected into the vertical pipe to lift the water from the reservoir. The flow map regime is established for both configurations and compared with previous studies. The two phase air-water flow structure at the expansion region is experimentally characterized. Pipeline geometry is found to have a significant influence on the output water flow rate. Using high speed photography and electrical conductivity probes, new flow regimes, such as “slug to churn” and “annular to churn” flow, are observed and their influence on the output water flow rate and efficiency are discussed. These experimental results provide fundamental insights into the physics of modified airlift pump.

Development of a Phase-field Method for Phase Change Simulations Using a Conservative Allen-cahn Equation

2021 ◽  
Author(s):  
Akinori Tamura ◽  
Kenichi Katono
Keyword(s):  
Phase Change ◽  
Phase Field ◽  
Computational Efficiency ◽  
Power Plants ◽  
Field Method ◽  
Industrial Applications ◽  
Phase Field Method ◽  
Benchmark Problems ◽  
Two Phase ◽  
Cahn Equation

Abstract Two-phase flows including a phase change such as liquid-vapor flows play an important role in many industrial applications. A deeper understanding of the phase change phenomena is required to improve performance and safety of nuclear power plants. For this purpose, we developed a phase change simulation method based on the phase field method (PFM). Low computational efficiency of the conventional PFM based on the Cahn-Hilliard equation is an obstacle in practical simulations. To resolve this problem, we presented a new PFM based on the conservative Allen-Cahn equation including a phase change model. The wettability also needs to be considered in the phase change simulation. When we apply the conventional wetting boundary condition to the conservative Allen-Cahn equation, there is a problem that the mass of each phase is not conserved on the boundary. To resolve this issue, we developed the mass correction method which enables mass conservation in the wetting boundary. The proposed PFM was validated in benchmark problems. The results agreed well with the theoretical solution and other simulation results, and we confirmed that this PFM is applicable to the two-phase flow simulation including the phase change. We also investigated the computational efficiency of the PFM. In a comparison with the conventional PFM, we found that our proposed PFM was more than 100 times faster. Since computational efficiency is an important factor in practical simulations, the proposed PFM will be preferable in many industrial simulations.

Design and Analysis of Rotary Positive Displacement Mechanism for Oil-Less Compression

2010 ◽  
Author(s):  
Holger Roser
Keyword(s):  
High Speed ◽  
High Performance ◽  
Effective Means ◽  
Cost Effective ◽  
Industrial Applications ◽  
Two Phase ◽  
Major Drawback ◽  
Displacement Mechanism ◽  
Flow Losses ◽  
Positive Displacement

In this paper, a simple positive displacement mechanism is investigated, which comprises two counter-rotating meshing rotors within a casing. Although considered for various applications more than a century ago, the basic geometry of this mechanism has not been further explored or adapted to modern gas compressor technology. As a fully balanced rotational mechanism operating at uniform angular velocity, potential applications range from pumps to expanders, from slow large displacement to high-speed devices; nonetheless, this research focuses on high-performance oil-less gas compressors as an ideal application. During one complete cycle, the main rotor compresses and discharges the fluid, whilst the secondary rotor seals the compression chamber. Important features of this mechanism are the circular profiles of the rotors, the potential to accommodate large ports for reduced flow losses, and ease of cooling. The simple geometry facilitates a cost-effective means of achieving tight operating clearances between rotors and casing for enhanced sealing without the need for liquid lubricants such as oil. This study and preliminary tests indicate that pressure ratios suitable for standard industrial applications can be obtained over a broad speed range, whilst minimizing friction and flow losses, a major drawback of current technologies. Moreover, two-phase compression and injection of liquids prior to compression have been studied and identified as a means to further improve efficiency and cooling.

Status and Prospects of HTS Synchronous Machines

2006 ◽  
Vol 47 ◽  
pp. 228-237
Author(s):  
Heinz Werner Neumüller ◽  
G. Klaus ◽  
W. Nick
Keyword(s):  
High Speed ◽  
Power Plants ◽  
Large Scale ◽  
World Wide ◽  
Feasibility Studies ◽  
The United States ◽  
Industrial Applications ◽  
Economic Benefits ◽  
Synchronous Machines ◽  
High Efficient

Up to now most of the efforts for developing HTS technology have been directed to devices for grid applications. However, HTS synchronous machines as motors and generators become more and more interesting within the world-wide development programs. Replacing the copper winding of the rotor by an HTS one and introducing an iron-less aircore stator winding the very compact HTS machine has less than half the weight and volume, higher efficiency and an excellent operational behavior when compared to the conventional devices. These features make HTS rotating machines very attractive for e.g. ship drives and industrial applications for the processing industry and power generation in power plants and wind parks. World-wide, HTS machines have already demonstrated their advantages and technical feasibility. The prototypes are ranging from the 5 MW low-speed high-torque propulsion motor to the high-speed 3600 rpm 4 MVA HTS generator. Feasibility studies clearly show the financial benefits when introducing high-efficient HTS wire based rotors into a large scale power generator systems. At present, most of the industry driven activities take place in the United States, Germany, Japan and Korea and are mainly directed towards applications aboard ships. Further potential applications as well as the technical and economic benefits will be discussed.

Bubble Behaviour in Three Phase Capillary Microreactors

2003 ◽  
Vol 1 (1) ◽  
Author(s):  
Mark J Simmons ◽  
David C Y Wong ◽  
Paul J Travers ◽  
James S Rothwell
Keyword(s):  
High Speed ◽  
Flow Characteristics ◽  
Flow Regimes ◽  
Two Phase ◽  
Microchannel Reactors ◽  
Flow Maps ◽  
Three Phase ◽  
Monolith Reactors ◽  
Produce Flow ◽  
Churn Flow

Two-phase flow characteristics in vertical capillary downflow were investigated in order to obtain understanding of the behaviour of three-phase monolith reactors. Experiments were conducted using air and dyed water in round and square capillary tubes of 2 mm and 3 mm diameter. The flow regimes and transitions observed were recorded using high speed videography and this data was used to produce flow maps for each tube. The gas and liquid superficial velocities used ranged from 0.001 to 10 m/s and 0.0001 to 1 m/s respectively. The flow regimes and their transitions were found to be a strong function of tube geometry and surface tension effects, and some differences were observed between capillaries of round and square section. This has significant implications for the design of microchannel reactors. Annular, slug-annular, slug, bubbly and churn flow regimes were observed in the round tubes; channelling/irregular flow was observed in the square tubes in place of annular and slug-annular flow.

Investigation of Rod Vibrations in Droplet Two-Phase Flows

2011 ◽  
Author(s):  
Yoshiteru Komuro ◽  
Zensaku Kawara ◽  
Tomoaki Kunugi
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Nuclear Power ◽  
Power Plants ◽  
Motion Tracking ◽  
High Speed Camera ◽  
Two Phase Flows ◽  
Two Phase ◽  
Wet Condition ◽  
Flow Induced Vibrations

Flow-induced vibrations are important problems in nuclear power plants from the view point of reactor safety. In the investigations of these vibrations especially those induced by two-phase flows, a numerical simulation plays a significant role, so it is necessary to obtain the experimental datasets that can validate the results of the numerical simulation. This paper deals with the experimental data of one-end-supported rod vibration, and focuses on the differences between the rod vibrations induced by single-phase air flows and those induced by droplet two-phase flows. In the experiments, the displacement of the non-supported end of the test rod was visualized by the high speed camera with high spatial and temporal resolutions, namely 9.5 μm and 500 μsec. Using an image analyzing software, the rod vibration displacements were measured by the motion tracking method. The curved surface of the rod was observed by another high speed camera and the relationship between the rod vibrations and the wet condition on the surface of the rod was investigated. In addition, the vibrations measured by the strain gages and those by the high speed camera were compared to discuss the differences in these two ways of the measurements.

Cavitation-Induced Interface Instability of Droplet Between Plates

2019 ◽  
Author(s):  
Hongchen Li ◽  
Jingzhu Wang ◽  
Yiwei Wang
Keyword(s):  
High Speed ◽  
Industrial Applications ◽  
High Speed Photography ◽  
Affecting Factors ◽  
Interface Instability ◽  
Jet Formation ◽  
Wave Impact ◽  
Two Phase ◽  
Droplet Shape ◽  
Bubble Pulsation

Abstract Interface instability of droplet and formation of the liquid jet caused by internal volume oscillation are directly related to liquid pumping and mixing of microfluidic devices. Complex morphology jet enables liquid shaping, which is advantageous for industrial applications and biomedical engineering. In this study, the interface instability of cylindrical droplet between plates is investigated. The problem is analyzed through numerical simulation and experimentation. In the experiment, a single-pulse laser is used to generate cavitation at the center of the cylindrical droplet between two polymethyl methacrylate plates, and the physical progress is captured by high-speed photography. A compressible two-phase solver in the open source code OpenFOAM is used to simulate the 3D progress of bubble pulsation and droplet jet in consideration of viscosity and surface tension. Numerical methods adopt large eddy simulation. Results show that the interface density gradient is not collinear with the pressure gradient due to the shock wave impact and the bubble pulsation, that is, the baroclinic effect is the main cause of the instability at the droplet interface. The mechanism of the radial jet formation in the first period of bubble pulsation is closely related to the interface instability. A pair of vortex rings is formed under the influence of instability, thereby causing a stacking phenomenon on the jet head and eventually being cut. Affecting factors of the instability of the droplet interface are discussed. A high instability intensity of the droplet interface can be caused by a large initial bubble energy and a small contact angle. The instability strength of the droplet interface and the mode of jet formation are very sensitive to the curvature of the initial droplet shape. Relevant results may provide a reference for further understanding of interface instability and related engineering applications.

Analysis of Cavitating High Speed Liquid Flow Through a Converging-Diverging Nozzle

2015 ◽  
Author(s):  
William E. Asher ◽  
Steven J. Eckels
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Power Plants ◽  
Control Volume ◽  
Homogeneous Model ◽  
Cavitating Flow ◽  
Shear Stresses ◽  
Variable Cross ◽  
Two Phase ◽  
Integral Forms

Cavitation is an important and common phenomena in fluid flow in which a fluid becomes two-phase through pressure variation. In devices such as valves, orifices, and metering devices, as well as loss of coolant situations in power plants, cavitation can be of interest due to erosion, energy efficiency, safety, and other concerns. It is possible for a cavitating flow to become sonic, accelerating and imposing additional energy losses that would not have occurred had the flow remained below the speed of sound. Models of this aspect of two-phase flow have not been fully explored and often have only been developed for the case of constant area. In the present paper, the homogeneous equilibrium model is developed by applying the integral forms of the conservation of mass, momentum, and energy equations to a control volume of variable cross-sectional area with adiabatic walls. The developed model is then applied to experimental data with R-134a as the fluid of interest for an instrumented converging-diverging nozzle for which mass flow, pressure, and temperature are measured. Applying the model to the experimental data yields interesting results in both the relationship between velocity and void fraction and in the predicted shear stresses down the length of the nozzle. The model predicts negative shear stresses near the nozzle’s throat an order of magnitude higher than those seen elsewhere in the nozzle. For this reason, the homogeneous model is likely not sufficient to accurately describe this variant of cavitating flow.

Flow Pattern Transition Criteria for Upward Two-Phase Flow in Annulus

2020 ◽  
Author(s):  
He Wen ◽  
Zhao Chenru ◽  
Bo Hanliang
Keyword(s):  
Flow Pattern ◽  
Flow Patterns ◽  
Flow Transition ◽  
Two Phase ◽  
Transition Mechanism ◽  
Flow Pattern Transition ◽  
Transition Criteria ◽  
Asymmetric Shape ◽  
Basic Characteristics ◽  
Churn Flow

Abstract Vertical upward two-phase flows in annulus are of great importance in many industrial fields due to the closely relationship between the flow patterns and the heat transfer characteristics. Common flow patterns in annulus are bubbly (B), slug (S), churn (C) and annular (A) flow, most of which are quite similar to those in tubes. However, due to the elliptic nose and asymmetric shape of the Taylor bubble in annulus, the slug to churn flow transition could be influenced by the channel geometry which was usually ignored in most of the previous researches. The flow pattern transition criteria for tubes are thus not applicable for annulus, especially for slug to churn flow transition, which should be separately studied. Therefore, in this paper, the basic characteristics of the flow pattern in annulus and their transition mechanism are analyzed. In addition, a set of semi-empirical transition criteria with higher accuracy are assessed and selected for annulus based on theoretical analysis and comparisons with experimental data.

Images Analysis of Horizontal Two-Phase Slug Flows

2011 ◽  
Author(s):  
R. E. M. Morales ◽  
M. J. da Silva ◽  
E. N. Santos ◽  
L. Dorini ◽  
C. E. F. do Amaral ◽  
...  
Keyword(s):  
High Speed ◽  
Oil And Gas Industry ◽  
Industrial Applications ◽  
Wire Mesh ◽  
Bubble Velocity ◽  
Internal Diameter ◽  
Two Phase ◽  
Experimental Conditions ◽  
Flow Measurements ◽  
Slug Flows

Multi-phase flow measurements are very common in industrial applications especially of the oil and gas industry. In order to study such pattern one can apply many different techniques such as capacitive probes, X-ray and gamma ray tomography, ultrasound transducers, wire-mesh sensors and high speed videometry. This article describes experimental study of water-air slug in horizontal pipes through non-intrusive image analysis technique. A flow test section comprising of a pipe of 26 mm internal diameter and 9 m long was employed to generate slug flows under controlled conditions. The behavior of the flow was studied using gas and liquid velocities between 0.3 m/s and 2 m/s with 6000 images (500×232 pixels) for each case. The algorithm comprises the automatic analysis of a sequence of frames in MatLab to measure flow characteristics such as Taylor bubble velocity and frequency applying morphological treatment. Finally, the parameters measured through the high speed videometry were compared with theoretical predictions showing that such method can be used to validate other types of sensors in experimental conditions.

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