On the Lubrication of Short Porous Journal Bearings—Use of the Brinkman Model

1995 ◽  
Vol 117 (1) ◽  
pp. 196-199 ◽  
Author(s):  
Jaw-Ren Lin ◽  
Chi-Chuan Hwang
Keyword(s):  
Pressure Gradient ◽  
Journal Bearings ◽  
Shear Stresses ◽  
Brinkman Model ◽  
Eccentricity Ratio ◽  
Lubrication Performance ◽  
Viscous Shear ◽  
Permeability Parameter

Based on the Brinkman model (MB), this paper concerns the more realistic influence of viscous shear stresses on the lubrication performance of short porous journal bearings. Compared with those using the zero pressure gradient assumption (ZPGA), the effect of LPGA provides an improvement in the bearing performance, especially when the thick-walled bearing has higher permeability parameter or the journal operates at higher eccentricity ratio.

Direct and Inverse Solutions for Elastohydrodynamic Lubrication of Finite Porous Journal Bearings

2000 ◽  
Vol 123 (2) ◽  
pp. 276-282 ◽  
Author(s):  
Abdallah A. Elsharkawy ◽  
Lotfi H. Guedouar
Keyword(s):  
Parameter Estimation ◽  
Optimization Technique ◽  
Elastohydrodynamic Lubrication ◽  
Constant Load ◽  
Shear Stresses ◽  
Elastic Model ◽  
Eccentricity Ratio ◽  
Viscous Shear ◽  
Permeability Parameter ◽  
Inverse Solutions

In this paper a numerical solution for the elastohydrodynamic lubrication of a finite porous journal bearing is presented. The Brinkman–extended Darcy model was applied within the porous layer to incorporate the viscous shear stresses into the analysis. A simple elastic model is used to describe the elastic deformation of the liner. An inverse model is introduced to estimate the permeability parameter and/or the eccentricity ratio from experimentally obtained pressure data. As experimental measurements were not conducted, these data were simulated numerically. It consists of a direct solution for the pressure, for given parameters (permeability parameter and/or the eccentricity ratio), to which a normally distributed random error is added. The least-squares optimization technique is used to solve the proposed inverse problem. A unique solution was obtained for one-parameter estimation. The two-parameter estimation case, however, leads to multiple solutions lying on a constant load line.

Linear Stability Analysis of Short Porous Journal Bearings—Use of the Brinkman Model

1995 ◽  
Vol 117 (1) ◽  
pp. 199-202 ◽  
Author(s):  
Jaw-Ren Lin ◽  
Chi-Chuan Hwang
Keyword(s):  
Linear Stability ◽  
Flow Model ◽  
Slip Flow ◽  
Journal Bearings ◽  
Shear Stresses ◽  
Brinkman Model ◽  
Stability Threshold ◽  
Viscous Shear ◽  
Shear Effects ◽  
The Stability

On the basis of a Brinkman model (BM), this paper predicts that the effects of viscous shear stresses on the linear stability of short porous journal bearings are apparent and not negligible. Compared with those of the slip-flow model (SFM) and the Darcy model (DM), the viscous shear effects provide a significant increase in the stability threshold speeds of short porous journal bearings.

Thermohydrodynamic Lubrication Analysis of Misaligned Plain Journal Bearing With Rough Surface

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Jun Sun ◽  
Mei Deng ◽  
Yonghong Fu ◽  
Changlin Gui
Keyword(s):  
Surface Roughness ◽  
Thermal Effect ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Eccentricity Ratio ◽  
Oil Viscosity ◽  
Oil Film ◽  
Lubrication Performance ◽  
Journal Misalignment

Journal misalignment exists generally in journal bearings. When severe journal misalignment takes place, the minimum film thickness of journal bearings reduces greatly. In this condition, the surface roughness, the oil viscosity-pressure relationship (VPR), and the thermal effect have obvious effects on hydrodynamic lubrication performance of misaligned bearings. In this paper, the oil film pressure, oil film temperature, load-carrying capacity, end leakage flow rate, frictional coefficient, and misalignment moment of a journal bearing with different angles of journal misalignment and surface roughness, and considering oil VPR and thermal effect, were calculated based on the generalized Reynolds equation, energy equation, and solid heat conduction equation. The results show that the oil VPR and surface roughness have a significant effect on the lubrication of misaligned journal bearings under large eccentricity ratio. The thermal effect will affect obviously the lubrication of misaligned journal bearings when eccentricity ratio and angle of journal misalignment are all large. In the present design, the size of the journal bearing is compact more and more, and the eccentricity ratio and angle of journal misalignment are usually large in operating conditions. Therefore, it is necessary to take the effects of journal misalignment, surface roughness, oil VPR, and thermal effect into account in the design and analyses of journal bearings.

scholarly journals The effect of textured surfaces on the hydrodynamic pressure generation in journal bearings

2018 ◽  
Vol 204 ◽  
pp. 04006
Author(s):  
Muchammad ◽  
Mohammad Tauviqirrahman ◽  
Rizqy Amanullah Akbar ◽  
Fuad Hilmy ◽  
Jamari
Keyword(s):  
Journal Bearing ◽  
Fluid Dynamic ◽  
Surface Texturing ◽  
Hydrodynamic Pressure ◽  
Journal Bearings ◽  
Hydrodynamic Performance ◽  
Textured Surfaces ◽  
Eccentricity Ratio ◽  
Lubrication Performance ◽  
Effect Of Surface

Surface texturing of the lubricated bearing has proven to improve the hydrodynamic performance. The present paper analyzed the effect of surface texturing on the covergent journal bearing with computational fluid dynamic (CFD) approach. The eccentricity ratio, the ratio of textured depth and surface area are the main parameter research. It was shown that for the eccentricity ratio of 0.2, the surface texturing improves the hydrodynamic performance lubrication by increasing the load support. On the otherwise, for the eccentricity ratio of 0.8, the surface texturing does not improve the lubrication performance, even under certain condition, it decreases the lubrication performance of journal bearing.

Ciliary Flow of Casson Nanofluid with the Influence of MHD having Carbon Nanotubes

2020 ◽  
Vol 16 ◽  
Author(s):  
Adel Alblawi ◽  
Saba Keyani ◽  
S. Nadeem ◽  
Alibek Issakhov ◽  
Ibrahim M. Alarifi
Keyword(s):  
Carbon Nanotubes ◽  
Velocity Profile ◽  
Pressure Gradient ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Pressure Rise ◽  
Shear Stresses ◽  
Left Wall ◽  
Coupled Equations ◽  
The Right

Objective: In this paper, we consider a model that describes the ciliary beating in the form of metachronal waves along with the effects of Magnetohydrodynamic fluid over a curved channel with slip effects. This work aims at evaluating the effect of Magnetohydrodynamic (MHD) on the steady two dimensional (2-D) mixed convection flow induced in carbon nanotubes. The work is done for both the single wall nanotube and multiple wall nanotube. The right wall and the left wall possess a metachronal wave that is travelling along the outer boundary of the channel. Methods: The wavelength is considered as very large for cilia induced MHD flow. The governing linear coupled equations are simplified by considering the approximations of long wavelength and small Reynolds number. Exact solutions are obtained for temperature and velocity profile. The analytical expressions for the pressure gradient and wall shear stresses are obtained. Term for pressure rise is obtained by applying Numerical integration method. Results: Numerical results of velocity profile are mentioned in a table form, for various values of solid volume fraction, curvature, Hartmann number [M] and Casson fluid parameter [ζ]. Final section of this paper is devoted to discussing the graphical results of temperature, pressure gradient, pressure rise, shear stresses and stream functions. Conclusion: Velocity profile near the right wall of the channel decreases when we add nanoparticles into our base fluid, whereas an opposite behaviour is depicted near the left wall due to ciliated tips whereas the temperature is an increasing function of B and ߛ and decreasing function of ߶.

Endwall Boundary Layer Development in a Multistage Low-Speed Compressor With Tandem Stator Vanes

2021 ◽  
Author(s):  
Michael Hopfinger ◽  
Volker Gümmer
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Shear Stresses ◽  
Flow Area ◽  
Stage Design ◽  
Low Speed ◽  
Boundary Layer Development ◽  
Viscous Shear ◽  
Layer Development ◽  
Highly Loaded

Abstract The development of viscous endwall flow is of major importance when considering highly-loaded compressor stages. Essentially, all losses occurring in a subsonic compressor are caused by viscous shear stresses building up boundary layers on individual aerofoils and endwall surfaces. These boundary layers cause significant aerodynamic blockage and cause a reduction in effective flow area, depending on the specifics of the stage design. The presented work describes the numerical investigation of blockage development in a 3.5-stage low-speed compressor with tandem stator vanes. The research is aimed at understanding the mechanism of blockage generation and growth in tandem vane rows and across the entire compressor. Therefore, the blockage generation is investigated as a function of the operating point, the rotational speed and the inlet boundary layer thickness.

Analysis of Pneumatic Instability of Externally Pressurized Porous Gas Journal Bearings

1979 ◽  
Vol 101 (1) ◽  
pp. 48-53 ◽  
Author(s):  
N. S. Rao ◽  
B. C. Majumdar
Keyword(s):  
Theoretical Analysis ◽  
Mass Parameter ◽  
Journal Bearings ◽  
Order Perturbation ◽  
Rigid Rotor ◽  
Eccentricity Ratio ◽  
Dynamic Displacement ◽  
First Order ◽  
Supply Pressure ◽  
First Order Perturbation

A theoretical analysis is presented for the study of pneumatic instability for a rigid rotor supported in externally pressurized porous gas journal bearings. The analysis is based on a first-order perturbation with respect to the amplitude of dynamic displacement of rotor. The variation of threshold mass parameter with feeding parameter is shown. In addition, the effects of supply pressure, eccentricity ratio, L/D ratio, and porosity parameter are investigated and presented in the form of graphs.

Design of Multi-Recess Hydrostatic Journal Bearings for Minimum Total Power Loss

1974 ◽  
Vol 96 (1) ◽  
pp. 226-232 ◽  
Author(s):  
C. Cusano ◽  
T. F. Conry
Keyword(s):  
Rotational Speed ◽  
Power Loss ◽  
Load Capacity ◽  
Maximum Load ◽  
Journal Bearings ◽  
Design Criterion ◽  
Total Power ◽  
Eccentricity Ratio ◽  
Constant Ratio ◽  
Design Charts

The design problem is formulated for multi-recess hydrostatic journal bearings with a design criterion of minimum total power loss. The design is subject to the constraints of constant ratio of the recess area to the total bearing area and maximum load capacity for a given recess geometry. The L/D ratio, eccentricity ratio, ratio of recess area to total bearing area, and shaft rotational speed are considered as parameters. The analysis is based on the bearing model of Raimondi and Boyd [1]. This model is generally valid for low-to-moderate speeds and a ratio of recess area-to-total bearing area of approximately 0.5 or greater. Design charts are presented for bearings having a ratio of recess area-to-total bearing area of 0.6 and employing capillary and orifice restrictors, these being the most common types of compensating elements. A design example is given to illustrate the use of the design charts.

scholarly journals Mathematical Models and Evaluation Software for Stress-Strain State of the Earth’s Lithosphere

2019 ◽  
pp. 51-66
Author(s):  
Alexander O. Faddeev ◽  
Svetlana A. Pavlova ◽  
Tatiana M. Nevdakh
Keyword(s):  
Mathematical Model ◽  
Strain State ◽  
Uniform Grid ◽  
Shear Stresses ◽  
Stress Strain ◽  
Gravitation Field ◽  
Vertical Movements ◽  
Stress Strain State ◽  
The Earth ◽  
Viscous Shear

Introduction. For the purposes of this article, geodeformation processes mean processes associated with deformations arising from the movement of species and blocks of the lithosphere at various depths, including surfaces. The objective is to reconstruct geodynamic stress fields, which cause modern shifts and deformations in the Lithosphere. A mathematical model and software for estimating the stress-strain state of the Earth Lithosphere are considered. Materials and Methods.For mathematical modeling of stresses, isostatically reduced data on abnormal gravitation field were used. The methods of continuum mechanics and methods of the theory of differential equations were used to design a model for estimating the stressstrain state of the Earth Lithosphere. For processing input, intermediate and outcoming data, the Fourier transform method of spectral analysis for constructing grid functions and spectral-temporal method were used. To model for the stress-strain state of the Lithosphere globally, stress calculation was corrected on the basis of sputnik-derived velocity data at the surface of the earth crust. The data on the rates of horizontal and vertical movements at the surface of the Earth crust were processed to obtain a distribution of velocities in the uniform grid embracing longitudes and latitudes. The processing procedure was carried out on the basis of the Kraiging method. The software was developed in Borland Delphi 7.0 programming environment. Results. Based on the data on the abnormal gravitation field in isostatic reduction and information on the distribution of velocities of horizontal motions on the surface of the Earth crust, a mathematical model of the stress-strain state of the Lithosphere was constructed. With the help of the obtained mathematical model and software complex, the stress-strain state of the Lithosphere was calculated at various depth using elastic and elastic-viscous models, and maps of equipotential distribution of shear elastic-viscous deformations in the lithosphere at the depth of 10 km were constructed. Discussion and Conclusion. The presented mathematical model and software allow restoring fields of both elastic and elastic-viscous deformations that is fundamental for quantification of elastic-viscous shear stresses deep in the Earth Lithosphere.

Theoretical Prediction of the Lift-Off Speed in Aerodynamic Compliant Foil Journal Bearings

2010 ◽  
Author(s):  
Shemiao Qi ◽  
Y. S. Ho ◽  
Haipeng Geng ◽  
Lie Yu
Keyword(s):  
Theoretical Prediction ◽  
Generalized Solution ◽  
Journal Bearings ◽  
Numerical Results ◽  
Computational Method ◽  
Radial Clearance ◽  
Eccentricity Ratio ◽  
Foil Bearings ◽  
Lift Off ◽  
Air Film

In aerodynamic bearings, since the supporting air film is generated by rotor motion, there is no support at the start of motion. As in all such bearings, there is dry rubbing until the rotor achieves sufficient speed to lift-off. Thus, the lower the lift-off speed, the less will be the rubbing and so the greater will be the life of the bearing. This paper focuses on the theoretical prediction of lift-off speed in aerodynamic compliant foil journal bearings based on a generalized solution of elasto-aerodynamically coupled lubrication for compliant foil bearings. A computational method is presented which is used to predict the lift-off speed in aerodynamic foil journal bearings with eccentricity ratio greater than or equal to 1.0. Special emphasis is placed on investigating the effects of the load imposed on the bearing, the nominal radial clearance and the bearing radius on the lift-off speed. The numerical results obtained indicate that lift-off speed decreases with the decrease of load and nominal radial clearance, but with an increase in bearing radius. The eccentricity ratios are all greater than 1.0 at the lift-off speed for the aerodynamic compliant foil journal bearings used in this study.

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