scholarly journals Detection of Gas-Solid Two-Phase Flow Based on CFD and Capacitance Method

2018 ◽  
Vol 8 (8) ◽  
pp. 1367 ◽  
Author(s):  
Wanting Zhou ◽  
Yue Jiang ◽  
Shi Liu ◽  
Qing Zhao ◽  
Teng Long ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Cfd Simulation ◽  
Fluid Model ◽  
Flow Direction ◽  
Solid Particles ◽  
Drilling Process ◽  
Sources Of Information ◽  
Discrete Phase Model ◽  
Horizontal Drilling ◽  
Annular Channels

Multiphase flow in annular channels is complex, particularly in the region where the flow direction abruptly changes between the inner pipe and the outer pipe, as the cases in horizontal drilling and pneumatic conveying. Simplified models and experience are still the main sources of information. First, to understand the process more deeply, Computational Fluid Dynamics (CFD) package Fluent is used to simulate the gas-solid flow in the horizontal and the inclined section of an annular pipe. Discrete Phase Model (DPM) is adopted to calculate the trajectories of solid particles of different sizes at different air velocities. Also, the Two-Fluid model is used to simulate the sand flow in the inclined section for the case of air flow stoppage, for which an experiment is also conducted to verify the CFD simulation. Simulation results reveal the behaviour of the solid particles showing the dispersed spatial distribution of small particles near the entrance. On the other hand, larger particles manifest a distinct sedimented flow pattern along the bottom of the pipe. The density distribution of the particles over a pipe cross section is demonstrated at a variety of air velocities. The results also show that the large airspeed tends to generate swirls near the outlet of the inner pipe. In addition, Electrical Capacitance Tomography (ECT) technology is used to reconstruct the spatial distribution of particles, and the cross-correlation algorithm to detect velocity. Both the distribution and the velocity measurement by electric sensors agree reasonably well with the CFD predictions. The details revealed by CFD simulation and the mutual-verification between CFD simulation and the ECT method of this study could be valuable for the industry in drilling process control and equipment development.

scholarly journals Decaying Swirl Flow and Particle Behavior through the Hole Cleaning Device for Horizontal Drilling of Fossil Fuel

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 336 ◽  
Author(s):  
Jingyu Qu ◽  
Tie Yan ◽  
Xiaofeng Sun ◽  
Zijian Li ◽  
Wei Li
Keyword(s):  
Fluid Model ◽  
Flow Direction ◽  
Tangential Velocity ◽  
Swirl Flow ◽  
Horizontal Drilling ◽  
Hole Cleaning ◽  
Particle Behavior ◽  
Swirl Intensity ◽  
Cleaning Device ◽  
Two Fluid Model

The hole cleaning device is a powerful application which can effectively slow down the deposition of cuttings during drilling. However, in this complicated swirl flow created by the device, the decay of the swirl flow and the particle behavior are not evident yet. In this paper, the decay of the swirl flow and the particle behavior in the swirl flow field are studied by the Eulerian–Eulerian two-fluid model (TFM) coupled with the kinetic theory of granular flows (KTGF), and sliding mesh (SM) technique for simulating the fluid flow. The results show that the swirl intensity decays exponentially along the flow direction under laminar flow conditions. The swirl flow has a longer acting distance at a higher rotational speed, which can effectively slow down the deposition of cutting particles. The initial swirl intensity of swirl flow induced by the blades increases significantly with the increase of blade height and the decrease of the blade angle. The tangential velocity of the cutting particles in the annulus is more significant near the central region, gradually decreases toward the wall in the radial direction, and rapidly decreases to 0 at the wall surface. The decay rate is negatively correlated with the initial swirl intensity. The results presented here may provide a useful reference for the design of the hole cleaning device.

CFD Study on must of Grapes Separation in a Hydrocyclone

2013 ◽  
Vol 837 ◽  
pp. 645-650
Author(s):  
Petru Cârlescu ◽  
Ioan Tenu ◽  
Marius Baetu ◽  
Radu Rosca
Keyword(s):  
Cfd Simulation ◽  
Reynolds Stress Model ◽  
Continuous Phase ◽  
Solid Particles ◽  
Advanced Degree ◽  
Separation And Purification ◽  
Discrete Phase Model ◽  
Flow Rates ◽  
Discrete Phase ◽  
Simulation And Experiment

Abstract. Hydrocyclones are increasingly used in the food industry for various separation and purification. In this paper, an optimization was made to design a hydrocyclone model using CFD (Computational Fluid Dynamics). CFD simulation is performed with FLUENT software by coupling the Reynolds Stress Model (RSM) for must of grapes flow with Discrete Phase Model (DPM) for solid particles trajectory. Coupling of discrete phase (particles) and continuous phase (must of grapes) in the mathematical model is set so that the continuous phase to influence discrete phase. Tracking particles traiectory in this hydrocyclone allows advanced degree is separation so obtained to the maximum particle size approaching the size of a yeast cell 10 μm, without separating them. Hydrocyclone dimensional designed simulation was performed and analyzed on an experimental pilot plant for three different must flow rates supply. Introduced particle flow rates simulation and experiment does not exceed 10% of the must flow rates. The degree of separation obtained is in agreement with experimental data.

Effect of Particle Size on Magnitude and Location of Maximum Erosion in S-Bend

2014 ◽  
Author(s):  
Quamrul H. Mazumder
Keyword(s):  
Particle Size ◽  
Oil And Gas ◽  
Cfd Simulation ◽  
Flow Direction ◽  
Fluid Dynamic ◽  
Erosive Wear ◽  
Impact Angle ◽  
Solid Particles ◽  
Particle Sizes ◽  
Fluid Properties

Solid particle erosion is a micromechanical process that is influenced by flow geometry, material of the impacting surface, impact angle, particle size and shape, particle velocity, flow condition and fluid properties. Among the various factors, particle size and velocity have been considered to be the most important parameters that cause erosion. Particle size and velocity are influenced by surrounding flow velocities and carrying fluid properties. Higher erosion rates have been observed in gas-solid flow in geometries where the flow direction changes rapidly, such as elbows, tees, valves, etc., due to local turbulence and unsteady flow behaviors. S-bend geometry is widely used in different fluid handling applications such as automotive, oil and gas, arteries and blood vessels. This paper presents the results of a Computational Fluid Dynamic (CFD) simulation of diluted gas-solid and liquid-solid flows through an S-Bend and the dynamic behavior of entrained solid particles in the flow. CFD analyses were performed at five different particle sizes ranging between 50 and 300 microns. Maximum erosive wear was observed at smaller particle sizes and compared to the larger sizes. The location of maximum erosion was at different locations in the first bend as compared to the second bend.

Evaluation of Magnitude and Location of Solid Particle Erosive Wear in an Elbow Geometry Using CFD Analysis

2009 ◽  
Author(s):  
Quamrul H. Mazumder
Keyword(s):  
Particle Size ◽  
Cfd Simulation ◽  
Flow Direction ◽  
Erosive Wear ◽  
Impact Angle ◽  
Solid Particles ◽  
Metal Loss ◽  
Solid Flow ◽  
Fluid Properties ◽  
Flow Velocities

A number of factors that influence the magnitude of erosion include geometry, material of the impacting surface, impact angle, particle size and shape, particle velocity, flow condition and fluid properties. Among the various factors, particle size and velocity has been considered to be most important parameter that causes erosion. Particle size and velocity are influenced by surrounding flow velocities and carrying fluid properties. Higher erosion rates has been observed in gas solid flow in geometry where the flow direction changes rapidly such as elbow, tee, valves, etc due to local turbulence and unsteady flow behaviors. This paper presents the results of a Computational fluid dynamics (CFD) simulation of dilute gas-solid flow through a 90 degree elbow due to dynamics behavior of entrained solid particles in the flow. The effect of particle size and the corresponding location of erosion were investigated for 50, 100, 150, 200, 250 and 300 μm sand particles for three different flow velocities (15, 30 and 45 m/sec). The magnitude and location of erosion presented in the paper can be used to determine the areas susceptible to maximum erosive wear in the geometry along with corresponding rate of metal loss in these areas.

Numerical Approaches for Modeling Gas–Solid Fluidized Bed Reactors: Comparison of Models and Application to Different Technical Problems

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Peter Ostermeier ◽  
Annelies Vandersickel ◽  
Stephan Gleis ◽  
Hartmut Spliethoff
Keyword(s):  
Calcium Carbonate ◽  
Size Distribution ◽  
Fluidized Bed ◽  
Fluid Model ◽  
Industrial Applications ◽  
Small Scale ◽  
Fluidized Bed Reactors ◽  
Discrete Phase Model ◽  
Technical Problems ◽  
Numerical Approaches

Gas–solid fluidized bed reactors play an important role in many industrial applications. Nevertheless, there is a lack of knowledge of the processes occurring inside the bed, which impedes proper design and upscaling. In this work, numerical approaches in the Eulerian and the Lagrangian framework are compared and applied in order to investigate internal fluidized bed phenomena. The considered system uses steam/air/nitrogen as fluidization gas, entering the three-dimensional geometry through a Tuyere nozzle distributor, and calcium oxide/corundum/calcium carbonate as solid bed material. In the two-fluid model (TFM) and the multifluid model (MFM), both gas and powder are modeled as Eulerian phases. The size distribution of the particles is approximated by one or more granular phases with corresponding mean diameters and a sphericity factor accounting for their nonspherical shape. The solid–solid and fluid–solid interactions are considered by incorporating the kinetic theory of granular flow (KTGF) and a drag model, which is modified by the aforementioned sphericity factor. The dense discrete phase model (DDPM) can be interpreted as a hybrid model, where the interactions are also modeled using the KTGF; however, the particles are clustered to parcels and tracked in a Lagrangian way, resulting in a more accurate and computational affordable resolution of the size distribution. In the computational fluid dynamics–discrete element method (CFD–DEM) approach, particle collisions are calculated using the DEM. Thereby, more detailed interparticulate phenomena (e.g., cohesion) can be assessed. The three approaches (TFM, DDPM, CFD–DEM) are evaluated in terms of grid- and time-independency as well as computational demand. The TFM and CFD–DEM models show qualitative accordance and are therefore applied for further investigations. The MFM (as a variation of the TFM) is applied in order to simulate hydrodynamics and heat transfer to immersed objects in a small-scale experimental test rig because the MFM can handle the required small computational cells. Corundum is used as a nearly monodisperse powder, being more suitable for Eulerian models, and air is used as fluidization gas. Simulation results are compared to experimental data in order to validate the approach. The CFD–DEM model is applied in order to predict mixing behavior and cohesion effects of a polydisperse calcium carbonate powder in a larger scale energy storage reactor.

Spatial Distribution of Local Permeabilities in Fibrous Networks

1992 ◽  
Vol 62 (3) ◽  
pp. 151-161 ◽  
Author(s):  
Susan M. Montgomery ◽  
Bernard Miller ◽  
Ludwig Rebenfeld
Keyword(s):  
Spatial Distribution ◽  
Spatial Heterogeneity ◽  
Heterogeneous Networks ◽  
Flow Direction ◽  
Time Dependent ◽  
Dependent Development ◽  
Fabric Structure ◽  
Elliptical Flow ◽  
Fluid Boundary ◽  
Liquid Flows

The shape of a developing radial fluid boundary in the plane of a fabric is a reflection of the structure of the fabric. Homogeneous fabrics, with permeabilities independent of position, yield circular or elliptical flow fronts, depending on the existence of a universally preferred flow direction. Heterogeneous networks yield flow fronts that deviate from this elliptical shape due to spatial variations in permeability. The time-dependent development of the fluid front that occurs when liquid flows radially in the plane of a fabric may be analyzed using Darcy's law to calculate local fabric permeabilities. The resulting spatial distribution of permeabilities is representative of the spatial heterogeneity of the fabric structure. Sample permeability distributions of geotextile fabrics are discussed.

scholarly journals Experimental and Numerical Analysis on Two-Phase Induced Low-Speed Pre-Ignition

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 5063
Author(s):  
Norbert Zöbinger ◽  
Thorsten Schweizer ◽  
Thomas Lauer ◽  
Heiko Kubach ◽  
Thomas Koch
Keyword(s):  
Gas Phase ◽  
Cfd Simulation ◽  
Particle Temperature ◽  
Solid Particles ◽  
Two Phase ◽  
Engine Operation ◽  
Oil Droplet ◽  
Low Speed ◽  
Detailed Reaction Mechanism ◽  
Oil Fuel

The root cause of the initial low-speed pre-ignition (LSPI) is not yet clarified. The literature data suggest that a two-phase phenomenon is most likely triggering the unpredictable premature ignitions in highly boosted spark-ignition engines. However, there are different hypotheses regarding the actual initiator, whether it is a detached liquid oil-fuel droplet or a solid-like particle from deposits. Therefore, the present work investigates the possibility of oil droplet-induced pre-ignitions using a modern downsized engine with minimally invasive endoscopic optical accessibility incorporating in-cylinder lubrication oil detection via light-induced fluorescence. This setup enables the differentiation between liquid and solid particles. Furthermore, the potential of hot solid particles to initiate an ignition under engine-relevant conditions is analyzed numerically. To do so, the particle is generalized as a hot surface transferring heat to the reactive ambient gas phase. The gas-phase reactivity is represented as a TRF/air mixture based on RON/MON specifications of the investigated fuel. The chemical processes are predicted using a semi-detailed reaction mechanism, including 137 species and 633 reactions in a 2D CFD simulation framework. In the optical experiments, no evidence of a liquid oil droplet-induced pre-ignition could be found. Nevertheless, all observed pre-ignitions had a history of flying light-emitting objects. There are strong hints towards solid-like deposit LSPI initiation. The application of the numerical methodology to mean in-cylinder conditions of an LSPI prone engine operation point reveals that particles below 1000 K are not able to initiate a pre-ignition. A sensitivity analysis of the thermodynamic boundary conditions showed that the particle temperature is the most decisive parameter on the calculated ignition delay time.

scholarly journals CFD simulation of gas-liquid floating particles mixing in an agitated vessel

2017 ◽  
Vol 23 (3) ◽  
pp. 377-389 ◽  
Author(s):  
Liangchao Li ◽  
Bin Xu
Keyword(s):  
Velocity Field ◽  
Cfd Simulation ◽  
Solid Phase ◽  
Fluid Model ◽  
Surface Region ◽  
Operating Conditions ◽  
Gas Dispersion ◽  
Agitated Vessel ◽  
Superficial Gas Velocity ◽  
Floating Particles

Gas dispersion and floating particles suspension in an agitated vessel were studied numerically by using computational fluid dynamics (CFD). The Eulerian multi-fluid model along with standard k-? turbulence model was used in the simulation. A multiple reference frame (MRF) approach was used to solve the impeller rotation. The velocity field, gas and floating particles holdup distributions in the vessel were first obtained, and then, the effects of operating conditions on gas dispersion and solid suspension were investigated. The simulation results show that velocity field of solid phase and gas phase are quite different in the agitated vessel. Floating particles are easy to accumulate in the center of the surface region and the increasing of superficial gas velocity is in favor of floating particles off-surface suspension. With increasing solids loading, the gas dispersion becomes worse, while relative solid holdup distribution changes little. The limitations of the present modeling are discussed and further research in the future is proposed.

scholarly journals The alteration of the operating parameteres of the aerocyclone depending on the geometry of the vortex finder

2021 ◽  
Vol 11 (5) ◽  
pp. 180-187
Author(s):  
Blanka Orosz ◽  
Máté Petrik ◽  
L. Gábor Szepesi
Keyword(s):  
Production Process ◽  
Significant Role ◽  
Cfd Simulation ◽  
Solid Particles ◽  
Engineering Practice ◽  
Operating Parameters ◽  
Hazardous Material ◽  
Vortex Finder

The engineering practice in general requires the ability to recognize the possible hazards associated with the coordinated production process. Solid particles found in the air can potentially be one of these, therefore it is fundamental to deal with the risk posed by certain types of dusts. An industrial cyclone is an equipment which is designed to separate the hazardous material from the harmless matter within the air. First and foremost the efficiency of a cyclone is determined substantially by the operating parameters. Certain geometries of the device however, such as the vortex finder can also have a significant role. The experiment conducted revolves around a CFD simulation to determine the efficiency of the apparatus based on different geometries in general and also regarding the vortex finder. The results indicate that the length of the vortex detector has a more significant effect, than the overall geometry.

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