Effects of Increased Tooth Clearance on the Performance of a Labyrinth Seal With Oil-Rich Bubbly Laminar Flow

2021 ◽  
Author(s):  
Min Zhang ◽  
Dara W. Childs
Keyword(s):  
Smooth Surface ◽  
Volume Fraction ◽  
Silicone Oil ◽  
Bubbly Flow ◽  
Labyrinth Seal ◽  
Test Fluid ◽  
Axial Thrust ◽  
Rotordynamic Coefficients ◽  
Piston Seal ◽  
The Impact

Abstract In recent years, multiphase pumps have become more and more popular because of the capability to simplify the process, reduce the footprint, and lower the cost. To compensate for the axial thrust force, an annular seal is normally used as a balance piston seal, and the labyrinth seal is one of the choices. A typical labyrinth seal consists of a surface with teeth and a smooth surface. The teeth are either on the rotor or the stator. To protect the machine, one side (either the teeth or the smooth surface) is made of a material that can be safely sacrificed during a rub. After the rub, the teeth clearance is increased. This paper studies the impact of the increased teeth clearance on the performance of the labyrinth seal under oil-rich bubbly flow conditions. The test fluid is a mixture of silicone oil (PSF 5cSt) and air with inlet Gas Volume Fraction GVF up to 9%. Tests are conducted with pressure drop PD = 34.5 bars, rotor speed ω = 5 krpm, and radial tooth clearance Cr = 0.102 mm and 0.178 mm. Test results show that, for all test conditions (before and after injecting air bubbles into the oil flow), increasing Cr from 0.102 mm to 0.178 mm increases the mass flow rate by about 40% but barely changes the test seal’s rotordynamic coefficients; i.e., the increased tooth clearance would not change the pump vibration performance.

A Study on the Leakage and Rotordynamic Performance of a Long Labyrinth Seal Under Mainly Air Conditions

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Min Zhang ◽  
Dara W. Childs
Keyword(s):  
Silicone Oil ◽  
Dynamic Stiffness ◽  
Excitation Frequency ◽  
Labyrinth Seal ◽  
System Stability ◽  
Test Fluid ◽  
Liquid Volume ◽  
Frequency Dependent ◽  
Frequency Independent ◽  
The Impact

Abstract This paper investigates the impact of liquid presence in air on the leakage and rotordynamic coefficients of a long (length-to-diameter ratio L/D = 0.747) teeth-on-stator labyrinth seal. The test fluid is a mixture of air and silicone oil (PSF-5cSt). Tests are carried out at inlet pressure Pi = 62.1 bars, three pressure ratios from 0.21 to 0.46, three speeds from 10 to 20 krpm, and six inlet liquid volume fractions (LVFs) from 0% to 15%. Complex dynamic-stiffness coefficients Hij are measured. The real parts of Hij are too frequency dependent to be fitted by frequency-independent stiffness and virtual-mass coefficients. Therefore, this paper presents frequency-dependent direct stiffness KΩ and cross-coupled stiffness kΩ. The imaginary parts of Hij produce frequency-independent direct damping C. Test results show that, under both pure- and mainly air conditions, the leakage mass flowrate m˙ of the test seal steadily increases as inlet LVF increases. KΩ is negative under all test conditions, and the magnitude of KΩ increases as inlet LVF increases, leading to a larger negative centering force on the associated compressor rotor. Under pure-air conditions, kΩ is a small negative value. Injecting oil into the air increases kΩ slightly and make the magnitude of kΩ closer to zero. Under mainly air conditions, increasing inlet LVF from 2% to 15% has little impact on kΩ. C normally increases as inlet LVF increases. The value of the effective damping Ceff = C − kΩ/Ω near 0.5ω is of significant interest to the system stability since an unstable centrifugal compressor may precess at approximately 0.5ω. Ω denotes the excitation frequency. The oil presence in the air has little impact on the value of Ceff near 0.5ω. Also, the liquid presence does not change the insensitiveness of m˙, KΩ, kΩ, C, and Ceff to change in ω; i.e., under both pure- and mainly air conditions, changes in ω has little impact on m˙, KΩ, kΩ, C, and Ceff.

A Study for Rotordynamic and Leakage Characteristics of a Long-Honeycomb Seal With Two-Phase, Mainly Air Mixtures

2019 ◽  
Author(s):  
Min Zhang ◽  
Dara W. Childs
Keyword(s):  
Volume Fraction ◽  
Silicone Oil ◽  
Pressure Ratio ◽  
Excitation Frequency ◽  
System Stability ◽  
Test Fluid ◽  
Liquid Volume ◽  
Liquid Volume Fraction ◽  
Honeycomb Seal ◽  
The Impact

Abstract This paper investigates the impact of the oil (silicone oil PSF-5cSt) presence in the air on the leakage and rotordynamic characteristics of a long-honeycomb seal with length-to-diameter ratio L/D = 0.748 and diameter D = 114.656 mm. Tests are carried out with inlet pressure Pi = 70.7 bars, pressure ratio PR = 0.35 and 0.25, inlet liquid volume fraction LVF = 0%, 3.5%, and 7%, and shaft speed ω = 10, 15, and 20 krpm. During the tests, the seal is centered. Test results show that leakage mass flow rate ṁ increases (as expected) as inlet LVF increases. Increasing inlet LVF makes direct stiffness K increase more rapidly with increasing excitation frequency Ω. Increasing inlet LVF has a negligible effect on K at low Ω values, but increases K at high Ω values. The value of effective damping Ceff at about 0.5ω is an indicator to the system stability since an unstable centrifugal compressor rotor can precess at about 0.5ω. Increasing inlet LVF increases the value of Ceff at about 0.5ω, reducing the possibility of sub-synchronous vibrations SSVs at about 0.5ω. San Andrés’s model is used to produce predictions. The model assumes that the test fluid in the seal clearance is an isothermal-homogenous mixture. The model adequately predicts ṁ, K, and the value of Ceff at about 0.5ω.

A Study for Rotordynamic and Leakage Characteristics of a Long-Honeycomb Seal With Two-Phase, Mainly Air Mixtures

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Min Zhang ◽  
Dara W. Childs
Keyword(s):  
Volume Fraction ◽  
Silicone Oil ◽  
Pressure Ratio ◽  
Excitation Frequency ◽  
System Stability ◽  
Test Fluid ◽  
Liquid Volume ◽  
Liquid Volume Fraction ◽  
Honeycomb Seal ◽  
The Impact

Abstract This paper investigates the impact of the oil (silicone oil PSF-5cSt) presence in the air on the leakage and rotordynamic characteristics of a long-honeycomb seal with length-to-diameter ratio L/D = 0.748 and diameter D = 114.656 mm. Tests are carried out with inlet pressure Pi = 70.7 bars, pressure ratio (PR) = 0.35 and 0.25, inlet liquid volume fraction (LVF) = 0%, 3.5%, and 7%, and shaft speed ω = 10, 15, and 20 krpm. During the tests, the seal is centered. Test results show that leakage mass flow rate m˙ increases (as expected) as inlet LVF increases. Increasing inlet LVF makes direct stiffness K increase more rapidly with increasing excitation frequency Ω. Increasing inlet LVF has a negligible effect on K at low Ω values, but increases K at high Ω values. The value of effective damping Ceff at about 0.5ω is an indicator to the system stability since an unstable centrifugal compressor rotor can precess at about 0.5ω. Increasing inlet LVF increases the value of Ceff at about 0.5ω, reducing the possibility of subsynchronous vibrations (SSVs) at about 0.5ω. San Andrés's model is used to produce predictions. The model assumes that the test fluid in the seal clearance is an isothermal-homogenous mixture. The model adequately predicts m˙, K, and the value of Ceff at about 0.5ω.

Effects of Clearance on the Performance of a Labyrinth Seal Under Wet-Gas Conditions

2020 ◽  
Author(s):  
Min Zhang ◽  
Dara W. Childs ◽  
Dung L. Tran ◽  
Hari Shrestha
Keyword(s):  
Dynamic Stiffness ◽  
Labyrinth Seal ◽  
Test Fluid ◽  
Radial Clearance ◽  
Liquid Volume ◽  
Rotordynamic Coefficients ◽  
Whirling Motion ◽  
Wet Gas ◽  
Different Diameters ◽  
The Impact

Abstract The labyrinth seal is one of the most popular non-contact annular seals used in centrifugal compressors to improve machine efficiency by reducing the secondary flow leakage. Reducing the radial clearance Cr can effectively decrease the seal’s leakage and therefore increase the machine efficiency. However, reducing Cr can also introduce undesired effects on the machine’s vibration behaviors. This paper experimentally studies the impact of reducing Cr on the leakage and rotordynamic coefficients of a 16-tooth see-through labyrinth seal under wet-gas conditions. The test seal’s inner diameter is 89.256 mm. Two rotors with different diameters are used to obtain two radial clearances (0.102 mm and 0.178 mm). Tests are carried out at a supply pressure of 62 bars, three speeds from 10krpm to 20 krpm, three pressure ratios from 0.21 to 0.46, and six inlet liquid volume fractions (LVFs) from zero to 15%. The test fluid is a mixture comprised of air and silicon oil. Test results show that, for all pure-air and mainly-air conditions, decreasing Cr decreases (as expected) the test seal’s leakage mass flow rate. For all test cases, direct dynamic stiffness KΩ is negative, producing a negative centering force on the associated rotor. For inlet LVF ≤ 8%, the effects of decreasing Cr on KΩ are negligible. When inlet LVF = 12% and 15%, decreasing Cr increases KΩ (decreases the magnitude). In other words, when inlet LVF = 12% and 15%, decreasing Cr reduces the test seal’s negative centering force on the rotor, and would increase the critical speeds of the rotor. The value of the effective damping Ceff near 0.5ω represents the seal’s capability to suppress the rotor’s potential whirling motion at about 0.5ω. For all pure-air and mainly-air conditions, decreasing Cr generally increases the Ceff value near 0.5ω; i.e., decreasing Cr improves the test seal’s stabilizing capability against the rotor’s potential whirling motion at about 0.5ω.

Effects of Clearance on the Performance of a Labyrinth Seal Under Wet-Gas Conditions

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Min Zhang ◽  
Dara W. Childs ◽  
Dung L. Tran ◽  
Hari Shresth
Keyword(s):  
Dynamic Stiffness ◽  
Labyrinth Seal ◽  
Test Fluid ◽  
Radial Clearance ◽  
Liquid Volume ◽  
Rotordynamic Coefficients ◽  
Whirling Motion ◽  
Wet Gas ◽  
Different Diameters ◽  
The Impact

Abstract The labyrinth seal is one of the most popular noncontact annular seals used in centrifugal compressors to improve machine efficiency by reducing the secondary flow leakage. Reducing the radial clearance Cr can effectively decrease the seal's leakage and therefore increase the machine efficiency. However, reducing Cr can also introduce undesired effects on the machine's vibration behaviors. This paper experimentally studies the impact of reducing Cr on the leakage and rotordynamic coefficients of a 16-tooth see-through labyrinth seal under wet-gas conditions. The test seal's inner diameter is 89.256 mm. Two rotors with different diameters are used to obtain two radial clearances (0.102 mm and 0.178 mm). Tests are carried out at a supply pressure of 62 bars, three speeds from 10 krpm to 20 krpm, three pressure ratios from 0.21 to 0.46, and six inlet liquid volume fractions (LVFs) from zero to 15%. The test fluid is a mixture comprised of air and silicon oil. Test results show that, for all pure-air and mainly air conditions, decreasing Cr decreases (as expected) the test seal's leakage mass flowrate. For all test cases, direct dynamic stiffness KΩ is negative, producing a negative centering force on the associated rotor. For inlet LVF ≤ 8%, the effects of decreasing Cr on KΩ are negligible. When inlet LVF = 12% and 15%, decreasing Cr increases KΩ (decreases the magnitude). In other words, when inlet LVF = 12% and 15%, decreasing Cr reduces the test seal's negative centering force on the rotor, and would increase the critical speeds of the rotor. The value of the effective damping Ceff near 0.5ω represents the seal's capability to suppress the rotor's potential whirling motion at about 0.5ω. For all pure-air and mainly air conditions, decreasing Cr generally increases the Ceff value near 0.5ω; i.e., decreasing Cr improves the test seal's stabilizing capability against the rotor's potential whirling motion at about 0.5ω.

Experimental Study on the Performance of a See-Through Labyrinth Seal With Two-Phase, Mainly-Liquid Mixtures

2020 ◽  
Author(s):  
Min Zhang ◽  
Dara W. Childs
Keyword(s):  
Experimental Study ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Labyrinth Seal ◽  
Test Fluid ◽  
Inlet Temperature ◽  
Pure Liquid ◽  
Pump Rotor ◽  
Piston Seal

Abstract With the increasing demand of the oil & gas industry, many pump companies are developing multiphase pumps, which can handle liquid-gas flow directly without separating the liquid from a mixed flow. The see-through labyrinth seal is one of the popular types of non-contact annular seals that act as a balancing piston seal to reduce the axial thrust of a high-performance centrifugal pump. The see-through labyrinth seal also generates reaction forces that can significantly impact the rotordynamic performance of the pump. Multiphase pumps are expected to operate from pure-liquid to pure-gas conditions. Zhang et al. (2019) conducted a comprehensive experimental study on the performance (leakage and rotordynamic coefficients) of a see-through labyrinth seal under mainly-gas conditions. This paper continues Zhang et al.’s (2019) research and studies the performance of the see-through TOS (tooth-on-stator) labyrinth seal under mainly-liquid conditions. The test seal’s inner diameter, length, and radial clearance are 89.256 mm, 66.68 mm, and 0.178 mm, respectively. The test fluid is a mixture of air and silicone oil (PSF-5cSt), and the inlet GVF (gas volume fraction) varies from zero to 12%. Tests are conducted at an exit pressure of 6.9 bars, an inlet temperature of 39.1 °C, three pressure drops PDs (27.6 bars, 34.5 bars, and 48.3 bars), and three rotating speeds ω (5 krpm, 10 krpm, and 15 krpm). The seal is always concentric with the rotor, and there is no intentional fluid pre-rotation at the seal inlet. The air presence in the oil flow significantly impacts the leakage as well as the dynamic forces of the test seal. The first air increment (increasing inlet GVF from 0% to 3%) slightly increases the leakage mass flow rate, while further air increments steadily decrease the leakage mass flow rate. For all test conditions, the leakage mass flow rate does not change as ω increases from 5 krpm to 10 krpm but decreases as ω is further increased to 15 krpm. The reduction in the leakage mass flow rate indicates that there is an increase in the friction factor, and there could be a highly possible flow regime change as ω increases from 10 krpm to 15 krpm. For ω ≤ 10 krpm, effective stiffness Keff increases as inlet GVF increases. Keff represents the test seal’s total centering force on the pump rotor. The increase of Keff increases the seal’s centering force and would increase the pump rotor’s critical speeds. Ceff indicates the test seal’s total damping force on the pump rotor. For ω ≤ 10 krpm, Ceff first decreases as inlet GVF increases from zero to 3%, and then remains unchanged as inlet GVF is further increased to 12%. For ω = 15 krpm, Keff first increases as inlet GVF increases from zero to 3% and then decreases as inlet GVF is further increased. As inlet GVF increases, Ceff steadily decreases for ω = 15 krpm.

Experimental Study on the Performance of a See-Through Labyrinth Seal With Two-Phase, Mainly-Liquid Mixtures

2021 ◽  
Vol 143 (1) ◽  
Author(s):  
Min Zhang ◽  
Dara W. Childs
Keyword(s):  
Experimental Study ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Gas Turbines ◽  
Labyrinth Seal ◽  
Test Fluid ◽  
Inlet Temperature ◽  
Pump Rotor ◽  
Piston Seal

Abstract With the increasing demand of the oil and gas industry, many pump companies are developing multiphase pumps, which can handle liquid–gas flow directly without separating the liquid from a mixed flow. The see-through labyrinth seal is one of the popular types of noncontact annular seals that act as a balancing piston seal to reduce the axial thrust of a high-performance centrifugal pump. The see-through labyrinth seal also generates reaction forces that can significantly impact the rotordynamic performance of the pump. Multiphase pumps are expected to operate from pure-liquid to pure-gas conditions. Zhang and Childs (2019) (Zhang, M., and Childs, D., 2019, “A Study on the Leakage and Rotordynamic Performance of a Long Labyrinth Seal Under Mainly-Air Conditions,” ASME J. Eng. Gas Turbines Power, 141(12), p. 121024) conducted a comprehensive experimental study on the performance (leakage and rotordynamic coefficients) of a see-through labyrinth seal under mainly gas conditions. This paper continues Zhang and Childs (2019) (Zhang, M., and Childs, D., 2019, “A Study on the Leakage and Rotordynamic Performance of a Long Labyrinth Seal Under Mainly-Air Conditions,” ASME J. Eng. Gas Turbines Power, 141(12), p. 121024) research and studies the performance of the see-through tooth-on-stator labyrinth seal under mainly liquid conditions. The test seal's inner diameter, length, and radial clearance are 89.256 mm, 66.68 mm, and 0.178 mm, respectively. The test fluid is a mixture of air and paper silicone oil (PSF-5cSt), and the inlet gas volume fraction (GVF) varies from zero to 12%. Tests are conducted at an exit pressure of 6.9 bars, an inlet temperature of 39.1 °C, three pressure drops (PDs) (27.6 bars, 34.5 bars, and 48.3 bars), and three rotating speeds ω (5 krpm, 10 krpm, and 15 krpm). The seal is always concentric with the rotor, and there is no intentional fluid prerotation at the seal inlet. The air presence in the oil flow significantly impacts the leakage as well as the dynamic forces of the test seal. The first air increment (increasing inlet GVF from 0% to 3%) slightly increases the leakage mass flow rate, while further air increments steadily decrease the leakage mass flow rate. For all test conditions, the leakage mass flow rate does not change as ω increases from 5 krpm to 10 krpm but decreases as ω is further increased to 15 krpm. The reduction in the leakage mass flow rate indicates that there is an increase in the friction factor, and there could be a highly possible flow regime change as ω increases from 10 krpm to 15 krpm. For ω ≤ 10 krpm, effective stiffness Keff increases as inlet GVF increases. Keff represents the test seal's total centering force on the pump rotor. The increase of Keff increases the seal's centering force and would increase the pump rotor's critical speeds. Ceff indicates the test seal's total damping force on the pump rotor. For ω ≤ 10 krpm, Ceff first decreases as inlet GVF increases from zero to 3%, and then remains unchanged as inlet GVF is further increased to 12%. For ω = 15 krpm, Keff first increases as inlet GVF increases from zero to 3% and then decreases as inlet GVF is further increased. As inlet GVF increases, Ceff steadily decreases for ω = 15 krpm.

scholarly journals Experimental Study of the Static and Dynamic Characteristics of a Long (L/D = 0.75) Labyrinth Annular Seal Operating Under Two-Phase (Liquid/Gas) Conditions

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Hari Shrestha ◽  
Dara W. Childs ◽  
Dung L. Tran ◽  
Min Zhang
Keyword(s):  
Volume Fraction ◽  
Silicone Oil ◽  
Dynamic Stiffness ◽  
Labyrinth Seal ◽  
Radial Clearance ◽  
Labyrinth Seals ◽  
Two Phase ◽  
Annular Seal ◽  
The Stability ◽  
Gas Volume

AbstractA two-phase annular-seal stand at the Turbomachinery Laboratory of Texas A&M University is utilized to experimentally investigate a labyrinth seal operating under two-phase flow conditions (a mixture of silicone oil and air). A long labyrinth seal (length-to-diameter ratio L/D = 0.75, diameter D = 114.729 mm, and radial clearance Cr = 0.213 mm) is tested at a supply pressure of 62 bars-g with inlet gas volume fraction GVFi ranging from 90 to 100%. Tests were conducted at three pressure ratios PR (0.3, 0.4, 0.5), three rotating speeds (5, 10, 15 krpm), six GVFi (90%, 92%, 94%, 96%, 98%, and 100%), and three inlet-preswirl inserts, namely, zero, medium, and high. Specifically, the ratio between the fluid's circumferential velocity and the shaft surface's velocity are in ranges of 0.0–0.2, 0.5–1.6, and 0.5–2.7 for the zero, medium, and high preswirls respectively. The direct dynamic stiffness KΩ is negative. As GVFi decreases (more liquid), KΩ becomes more negative for the zero preswirl. The effect of changing GVFi on KΩ for the medium and high preswirls is not as clear as for the zero preswirl. For the zero preswirl, as GVFi decreases, the cross-coupled dynamic stiffness kΩ and direct damping C damping increase. However, the effective damping Ceff values converge to almost the same positive value for higher frequencies. Hence, there is no significant effect of change in GVFi for the zero preswirl. For the high preswirl, as GVFi decreases, kΩ decreases and C increases. As GVFi decreases, Ceff becomes less negative and eventually becomes positive for frequencies higher than Ωc. This result indicates that at certain frequencies, the presence of liquid can make the labyrinth seals with high preswirl more stable. For the seal tested, a compressor running at 15 krpm and PR (ratio of seal exit pressure and seal inlet pressure) = 0.5 with the first critical speed of 7500 rpm (125 Hz) would experience an increase in stability with presence of liquid in the flow stream for the medium and high preswirls. However, for the range of GVFi considered here, if swirl brakes are used in a compressor application to reduce the preswirl, there would be no impact of liquid presence on the stability of the compressor. Concerning static measurements, leakage rate m˙ increases with decreases in GVFi but remains unchanged with increasing preswirl.

The Impact of Pad Flexibility on the Rotordynamic Coefficients of Tilting-Pad Journal Bearings

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Jennifer E. Gaines ◽  
Dara W. Childs
Keyword(s):  
Dynamic Stiffness ◽  
Dynamic Performance ◽  
Element Model ◽  
Bending Stiffness ◽  
Test Fluid ◽  
Unit Load ◽  
Rotordynamic Coefficients ◽  
Damping Coefficients ◽  
Tilting Pad ◽  
The Impact

Static and dynamic load tests were performed on a three-pad, rocker-pivot, tilting-pad journal bearing (TPJB) with three interchangeable pad configurations, each with measurably different pad flexibilities. Measured dynamic-stiffness data for the bearing were readily fitted by a frequency-independent, constant-coefficient [K][C][M] model. The test-bearing had a 101.74 mm diameter with L/D = 0.6. Tests were conducted over the speed range of 6–12 krpm, with unit loads varying from 0.172 to 1.724 MPa. An ISO VG 46 lubricant was used as the test fluid. Pad flexibility was characterized as the change in the pad's bending stiffness or the change in pad thickness. A finite-element model (FEM) was created to predict the structural bending stiffness of each pad configuration, showing a significant pad flexibility increase as pad thickness decreased. To examine the effect of pad flexibility on the rotordynamic coefficients, the measured results were compared across pad configurations and showed that the pad flexibility increase reduced the direct damping coefficients by 12–20%. As pad flexibility increased, the direct-stiffness coefficients could increase or decrease, depending on the unit load. They varied from an increase of 12% at low unit loads to a decrease of 3% at high unit loads. Results show that the pad's structural bending stiffness or flexibility is important when predicting the bearing’s dynamic performance. Damping is consistently overpredicted when neglecting pad flexibility. A nondimensional pad flexibility parameter αflex was developed. It related the average deflection across the pad surface to the pad's arc length and was to relate the pad flexibility of multiple bearings of different sizes. A bearing code was used to predict the percent change in direct damping coefficients for rigid-pad/flexible-pivot and flexible-pad/flexible-pivot models for a surface speed of 54 m/s and a unit load of 783 kPa for the three-pad configuration tested here plus five additional tested bearings from the literature. For the minimum pad thickness configuration tested here, the code predicted a 20% drop in predicted Cxx (off-load axis direct damping) when comparing a model that included pad flexibility with a model that neglected pad flexibility. In terms of αflex, the two thinnest pad configurations tested here are quite flexible compared to both TPJB's pads used in industry and previously tested TPJB pads.

scholarly journals CFD Modeling of Gas-Liquid Bubbly Flow in Horizontal Pipes: Influence of Bubble Coalescence and Breakup

2012 ◽  
Vol 2012 ◽  
pp. 1-20 ◽  
Author(s):  
K. Ekambara ◽  
R. Sean Sanders ◽  
K. Nandakumar ◽  
J. H. Masliyah
Keyword(s):  
Volume Fraction ◽  
Liquid Velocity ◽  
Bubbly Flow ◽  
Bubble Diameter ◽  
Three Dimensional ◽  
Gas Bubbles ◽  
Bubbly Flows ◽  
Cfd Modeling ◽  
Horizontal Pipe ◽  
The Impact

Modelling of gas-liquid bubbly flows is achieved by coupling a population balance equation with the three-dimensional, two-fluid, hydrodynamic model. For gas-liquid bubbly flows, an average bubble number density transport equation has been incorporated in the CFD code CFX 5.7 to describe the temporal and spatial evolution of the gas bubbles population. The coalescence and breakage effects of the gas bubbles are modeled. The coalescence by the random collision driven by turbulence and wake entrainment is considered, while for bubble breakage, the impact of turbulent eddies is considered. Local spatial variations of the gas volume fraction, interfacial area concentration, Sauter mean bubble diameter, and liquid velocity are compared against experimental data in a horizontal pipe, covering a range of gas (0.25 to 1.34 m/s) and liquid (3.74 to 5.1 m/s) superficial velocities and average volume fractions (4% to 21%). The predicted local variations are in good agreement with the experimental measurements reported in the literature. Furthermore, the development of the flow pattern was examined at three different axial locations ofL/D= 25, 148, and 253. The first location is close to the entrance region where the flow is still developing, while the second and the third represent nearly fully developed bubbly flow patterns.

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