Stabilization of Journal Bearing Using Two-Layered Film Lubrication

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
T. V. V. L. N. Rao
Keyword(s):  
Frequency Ratio ◽  
Journal Bearing ◽  
Fluid Layer ◽  
Load Capacity ◽  
High Viscosity ◽  
Fluid Film ◽  
Low Viscosity ◽  
Linearized Stability ◽  
Viscosity Fluid ◽  
Layered Fluid

The purpose of this paper is to present the linearized stability analysis of two-layered fluid film in the journal bearing. In this work, a modified classical Reynolds equation is derived under dynamic conditions consisting of two layers of fluid film described by Newtonian viscosities. The magnitude of lubricant layer’s film thickness and viscosities are taken into consideration. The Reynolds boundary conditions are used in the analysis of classical one-dimensional journal bearing to predict the stiffness and damping coefficients, threshold speed and critical whirl frequency ratio. The coefficients of load capacity, threshold speed, and critical whirl frequency ratio (Cw, Cω, CΩ) for two-layered film with reference to homogeneous film are computed as a function of the two parameters: (i) higher to lower dynamic viscosity ratio of two-layered fluid film (β), and (ii) thickness ratio of fluid layer attached to journal and bearing (γ). Higher threshold speed is obtained for thick high viscosity fluid film attached to the bearing surface and a thin low viscosity fluid film attached to the journal surface.

Stability evaluation of three-layered journal bearing with slip/partial slip

2017 ◽  
Vol 69 (3) ◽  
pp. 334-341 ◽  
Author(s):  
T.V.V.L.N. Rao ◽  
A.M.A. Rani ◽  
M. Awang ◽  
F.M. Hashim
Keyword(s):  
Surface Layer ◽  
Frequency Ratio ◽  
Journal Bearing ◽  
Core Layer ◽  
High Viscosity ◽  
Partial Slip ◽  
Bearing Surface ◽  
Content Type ◽  
Linearized Stability ◽  
Slip Region

Purpose This paper aims to present stability of a three-layered journal bearing considering magnitude of the layers’ thicknesses and viscosities with slip/partial slip on the bearing surface. Design/methodology/approach Modified Reynolds equation based on one-dimensional analysis is derived for a three-layered journal bearing with slip/partial slip. Dynamic coefficients are derived based on infinitesimal perturbation method. Linearized stability analysis is presented taking into account slip/partial slip on bearing surface; thicknesses and viscosities of bearing surface layer; and core layer and journal surface layer. Findings Results of threshold speed and critical whirl frequency ratio coefficients (Cω, CΩ), stiffness (Kij for i = x,y) and damping (Bij for i = x, y) coefficients and threshold speed (ωs) and critical whirl frequency ratio (Ωs) are presented. The bearing surface is analyzed for slip (total surface with slip) and partial slip (partial surface with slip). The slip-on bearing surface reduces stability, while partial slip improves bearing stability. The threshold speed coefficient (Cω) decreases with slip on bearing surface. The threshold speed (ωs) and critical whirl frequency ratio (Ωs) are influenced by the variation of threshold speed coefficient (Cω) and critical whirl frequency ratio coefficient (CΩ), respectively. A three-layered journal bearing with partial slip and thick high viscosity bearing surface layer results in higher threshold speed coefficient and has a potential to improve stability of journal bearing. The analyses indicate that optimal angular extent of partial slip region (θs) enhances the stability of journal bearing. Originality/value The paper presents parametric study of stability coefficients (Cω and CΩ) and evaluation of threshold speed (ωs) and critical whirl frequency ratio (Ωs) of a three-layered journal bearing with slip/partial slip.

scholarly journals Improvement of Tilting-Pad Journal Bearing Operating Characteristics by Application of Eddy Grooves

Lubricants ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 18
Author(s):  
Eckhard Schüler ◽  
Olaf Berner
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Load Capacity ◽  
Fluid Film ◽  
Operating Characteristics ◽  
Fluid Film Bearings ◽  
Tilting Pad ◽  
Bearing Load ◽  
Bearing Loads ◽  
Tilting Pad Journal Bearing

In high speed, high load fluid-film bearings, the laminar-turbulent flow transition can lead to a considerable reduction of the maximum bearing temperatures, due to a homogenization of the fluid-film temperature in radial direction. Since this phenomenon only occurs significantly in large bearings or at very high sliding speeds, means to achieve the effect at lower speeds have been investigated in the past. This paper shows an experimental investigation of this effect and how it can be used for smaller bearings by optimized eddy grooves, machined into the bearing surface. The investigations were carried out on a Miba journal bearing test rig with Ø120 mm shaft diameter at speeds between 50 m/s–110 m/s and at specific bearing loads up to 4.0 MPa. To investigate the potential of this technology, additional temperature probes were installed at the crucial position directly in the sliding surface of an up-to-date tilting pad journal bearing. The results show that the achieved surface temperature reduction with the optimized eddy grooves is significant and represents a considerable enhancement of bearing load capacity. This increase in performance opens new options for the design of bearings and related turbomachinery applications.

scholarly journals Nonlinear dynamic analysis of low viscosity fluid-lubricated tilting-pad journal bearing for different design parameters

Friction ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 930-944 ◽  
Author(s):  
Yingze Jin ◽  
Fei Chen ◽  
Jimin Xu ◽  
Xiaoyang Yuan
Keyword(s):  
Dynamic Analysis ◽  
Nonlinear Dynamic ◽  
Load Capacity ◽  
Nonlinear Dynamic Analysis ◽  
Design Parameters ◽  
Clearance Ratio ◽  
Low Viscosity ◽  
Nonlinear Design ◽  
Tilting Pad ◽  
Viscosity Fluid

Abstract To reveal nonlinear dynamic rules of low viscosity fluid-lubricated tilting-pad journal bearings (TPJBs), the effects of design parameters on journal center orbits and dynamic minimum film thicknesses of water-lubricated TPJBs with and without static loads are investigated. The hydrodynamic bearing force used in the nonlinear dynamic analysis is an approximate analytical solution including the turbulence effect. The results reveal the methods for vibration suppression and load capacity improvement and give an optimal pivot offset and clearance ratio that can maximize the minimum film thickness. The results also show that four-pad TPJBs with loads between pads are preferred due to good dynamic performance and load capacity. This study would provide some guidance for nonlinear design of low viscosity fluid-lubricated TPJBs under dynamic loads.

Proppant Placement Using Alternate-Slug Fracturing

SPE Journal ◽  
2014 ◽  
Vol 19 (05) ◽  
pp. 974-985 ◽  
Author(s):  
Sahil Malhotra ◽  
Eric R. Lehman ◽  
Mukul M. Sharma
Keyword(s):  
High Viscosity ◽  
Mixing Zone ◽  
Proppant Transport ◽  
Fracture Length ◽  
The Past ◽  
Low Viscosity ◽  
Viscous Fingers ◽  
Wide Range ◽  
Design Calculations ◽  
Viscosity Fluid

Summary New fracturing techniques, such as hybrid fracturing (Sharma et al. 2004), reverse-hybrid fracturing (Liu et al. 2007), and channel (HiWAY) fracturing (Gillard et al. 2010), have been deployed over the past few years to effectively place proppant in fractures. The goal of these methods is to increase the conductivity in the proppant pack, providing highly conductive paths for hydrocarbons to flow from the reservoir to the wellbore. This paper presents an experimental study on proppant placement by use of a new method of fracturing, referred to as alternate-slug fracturing. The method involves an alternate injection of low-viscosity and high-viscosity fluids, with proppant carried by the low-viscosity fluid. Alternate-slug fracturing ensures a deeper placement of proppant through two primary mechanisms: (i) proppant transport in viscous fingers, formed by the low-viscosity fluid, and (ii) an increase in drag force in the polymer slug, leading to better entrainment and displacement of any proppant banks that may have formed. Both these effects lead to longer propped-fracture length and better vertical placement of proppant in the fracture. In addition, the method offers lower polymer costs, lower pumping horsepower, smaller fracture widths, better control of fluid leakoff, less risk of tip screenouts, and less gel damage compared with conventional gel fracture treatments. Experiments are conducted in simulated fractures (slot cells) with fluids of different viscosity, with proppant being carried by the low-viscosity fluid. It is shown that viscous fingers of low-viscosity fluid and viscous sweeps by the high-viscosity fluid lead to a deeper placement of proppant. Experiments are also conducted to demonstrate slickwater fracturing, hybrid fracturing, and reverse-hybrid fracturing. Comparison shows that alternate-slug fracturing leads to the deepest and most-uniform placement of proppant inside the fracture. Experiments are also conducted to study the mixing of fluids over a wide range of viscosity ratios. Data are presented to show that the finger velocities and mixing-zone velocities increase with viscosity ratio up to viscosity ratios of approximately 350. However, at higher viscosity ratios, the velocities plateau, signifying no further effect of viscosity contrast on the growth of fingers and mixing zone. The data are an integral part of design calculations for alternate-slug-fracturing treatments.

Static and stability analysis of partial slip texture multi-lobe journal bearings

2019 ◽  
Vol 234 (4) ◽  
pp. 567-587
Author(s):  
TVVLN Rao ◽  
Ahmad M A Rani ◽  
Norani M Mohamed ◽  
Hamdan H Ya ◽  
Mokhtar Awang ◽  
...  
Keyword(s):  
Stability Analysis ◽  
Journal Bearing ◽  
Load Capacity ◽  
Journal Bearings ◽  
Partial Slip ◽  
Pressure Gradients ◽  
Capacity Coefficient ◽  
Texture Region ◽  
Linearized Stability ◽  
Infinitesimal Perturbation

This paper presents one-dimensional analysis of modified dynamic Reynolds equation derived for partial slip texture multi-lobe journal bearings. The novelty included in this study is the configuration of partial slip texture region on the bottom bearing lobe surface of a multi-lobe journal bearing under a constant vertical load. The nondimensional pressure and shear stress for steady-state and nondimensional pressure gradients for dynamic coefficients for each lobe with partial slip texture configuration are derived based on narrow groove theory. Linearized stability analysis is evaluated using infinitesimal perturbation method. Results of static and stability characteristics of partial slip texture multi-lobe (two-axial groove, elliptical, three-lobe and offset) journal bearings are presented. Partial slip texture configuration significantly enhances load capacity, coefficient of friction, and stability of two-lobe journal bearing.

Temporal and Convective Inertia Effects in Plain Journal Bearings With Eccentricity, Velocity and Acceleration

2011 ◽  
Author(s):  
Saeid Dousti ◽  
Jianming Cao ◽  
Amir Younan ◽  
Paul Allaire ◽  
Tim Dimond
Keyword(s):  
Reynolds Number ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Fluid Film ◽  
Navier Stokes ◽  
Inertia Effect ◽  
Inertia Effects ◽  
Low Viscosity ◽  
Fluid Film Bearings

Fluid film bearings are commonly analyzed with the conventional Reynolds equation, without any temporal inertia effects, developed for oil or other high viscosity lubricants. In applications with rapidly time varying external loads, e.g. ships on wavy oceans, temporal inertia effect should be taken into account. As rotating speeds increase in industrial machines and the reduced Reynolds number increases above the turbulent threshold, a form of linearized turbulence model is often used to increase the effective viscosity to take the turbulence into account. Other than the turbulence effect, with high reduced Reynolds number, convective inertia effect gains importance. Water or other low viscosity fluid film bearings used in subsea machines and compressors are potential applications with a highly reduced Reynolds number.” This paper extends the theory originally developed by Tichy [1] for impulsive loads to high reduced Reynolds number lubrication in different bearing configurations. Both fluid shear and pressure gradient terms are included in the velocity profiles across the lubricant film. The incompressible continuity equation and Navier Stokes equations, including the temporal inertia term, are simplified using an averaged velocity approach to obtain an extended form of Reynolds equation which applies to both laminar and turbulent flow. All terms in the Navier Stokes equation, including both the convective and temporal inertia terms are included in the analysis. The inclusion of the temporal inertia term creates a fluid acceleration term in the extended Reynolds equation. A primary advantage of this formulation is that fluid film bearings lubricated with low viscosity lubricants which are subject to high force slew rates can be analyzed with this extended Reynolds equation. A short bearing form of the extended Reynolds equation is developed with appropriate boundary conditions. A full kinematic analysis of the short journal bearing is developed including time derivatives up to and including shaft accelerations. Linearized stiffness, damping and mass coefficients are developed for a plain short journal bearing. A time transient solution is developed for the pressure and bearing loads in plain journal bearings supporting a symmetric rigid rotor when the rotor is subjected to rapidly applied large forces. The change in the rotor displacements when subjected to unbalance forces is explored. Several comparisons between conventional Reynolds equation solutions and the extended Reynolds number form with temporal inertia effects will be presented and discussed.

Performance of Adaptive Lubricants in a Hybrid Journal Bearing Operating Under Fully Saturated Conditions

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Ssu-Ying Chien ◽  
M. S. Cramer ◽  
Gen Fu ◽  
Alexandrina Untaroiu
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Fluid Dynamic ◽  
Load Capacity ◽  
Three Dimensional ◽  
Co2 Concentration ◽  
Dissolved Carbon ◽  
Synthetic Oil ◽  
Low Viscosity ◽  
Carbon Dioxide Co2

Adaptive lubricants involve binary mixture of synthetic oil and dissolved carbon dioxide (CO2). Unlike conventional lubricant oils, the lubricant viscosity not only varies with the temperature within the bearing but also can be directly adjusted through the CO2 concentration in the system. In this study, we consider the synthetic oil to be fully saturated by CO2 to investigate the maximum impacts of adaptive lubricants on the performance of a hybrid journal bearing. The adaptive lubricant analyzed for this study was the polyalkylene glycol (PAG) oil with low concentration of CO2 (<30%). A three-dimensional (3D) computational fluid dynamic (CFD) model of the bearing was developed and validated against the experimental data. The mixture composition and the resultant mixture viscosity were calculated as a function of pressure and temperature using empirical equations. The simulation results revealed that the viscosity distribution within the PAG/CO2-lubricated bearing is determined primarily by the pressure at the low operating speed. When the speed becomes higher, it is the temperature effect that dominates the viscosity distribution within the bearing. Moreover, the PAG/CO2-lubricated bearing can reduce up to 12.8% power loss than the PAG-lubricated bearing due to the low viscosity of PAG/CO2 mixture. More importantly, we have found that the PAG/CO2 can enhance the load capacity up to 19.6% when the bearing is operating at high-speed conditions.

LOAD CAPACITY COEFFICIENT EVALUATION OF THREE-LAYERED JOURNAL BEARING WITH SLIP

2016 ◽  
Vol 78 (6-10) ◽  
Author(s):  
T. V. V. L. N. Rao ◽  
A. M. A. Rani ◽  
M. Awang ◽  
F. M. Hashim
Keyword(s):  
Reynolds Equation ◽  
Journal Bearing ◽  
Load Capacity ◽  
High Viscosity ◽  
Bearing Surface ◽  
Surface Layers ◽  
Navier Slip ◽  
Slip Boundary ◽  
Capacity Coefficient ◽  
Navier Slip Boundary Conditions

Analysis of three-layered journal bearing with slip on bearing surface is presented. A modified classical Reynolds equation is derived for slip on bearing surface taking into consideration of bearing surface, core and journal surface layers. The modified Reynolds equation is derived taking into consideration of lubricant layer’s film thickness, viscosities and slip on the bearing surface. Navier slip boundary conditions are used to analyze slip. Results of load capacity coefficient are presented for three-layered and two-layered journal bearing with slip. The load capacity coefficient decreases with bearing surface with slip. For a three-layered journal bearing with slip, high viscosity bearing surface layer results in higher load capacity coefficient.

scholarly journals Evaluating the effect of drill string rotation and change in drilling fluid viscosity on hole cleaning

2021 ◽  
Author(s):  
Samuel Bright Olawale ◽  
Promise O. Longe ◽  
Samuel Felix Ofesi
Keyword(s):  
Drilling Fluid ◽  
High Viscosity ◽  
Drill String ◽  
Rheological Parameters ◽  
Fluid Viscosity ◽  
Hole Cleaning ◽  
Low Viscosity ◽  
Cutting Bed ◽  
Viscosity Fluid ◽  
Deviated Wells

AbstractThe most primitive hole challenge is cleaning the hole, which is more severe in deviated wells. This problem was tackled in this research via experimental analysis and graphical evaluations. To hit this aim, rheological parameters were experimentally obtained, and Noah’s model was used to determine cutting bed erosion time at varying heights. A graphical evaluation was done using a case study of deviated wells X and Y from a Niger Delta field. The result shows that low-viscosity fluid, KCL polymer fluid and high-viscosity fluid take 124, 283 and 342 min, respectively, to erode equal height as graphical evaluation shows that hole cleaning will grow complex on deviation. Thus, the deduction from this work in reducing non-productive time (NPT) related to hole cleaning in drilling operation is first, prior to making a trip, pumping low-viscosity fluid at a high flow rate. Secondly, during drilling, increasing drill string rotation in deviated wells can effectively stir the cuttings into the annulus above the low session of the hole.

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