An approximate method for the calculation of dynamic stiffness and damping coefficients of externally pressurized porous gas journal bearings

Wear ◽  
1980 ◽  
Vol 61 (2) ◽  
pp. 375-379 ◽  
Author(s):  
N.S. Rao ◽  
B.C. Majumdar
Keyword(s):  
Approximate Method ◽  
Dynamic Stiffness ◽  
Journal Bearings ◽  
Damping Coefficients ◽  
Stiffness And Damping

scholarly journals Alternation of the dynamic coefficients of short journal bearings due to wear

2015 ◽  
Vol 6 (5) ◽  
pp. 649-664
Author(s):  
Michael G. Papanikolaou ◽  
Michael G. Farmakopoulos ◽  
Chris A. Papadopoulos
Keyword(s):  
Dynamic Stiffness ◽  
Journal Bearings ◽  
Fe Analysis ◽  
Operating Conditions ◽  
Wear Depth ◽  
Content Type ◽  
Damping Coefficients ◽  
Dynamic Coefficients ◽  
Low Viscosity ◽  
Stiffness And Damping

Purpose – Wear in journal bearings occurs when the operating conditions (high load, high temperature, low angular velocity or low viscosity), downgrade the ability of the bearing to carry load. The wear depth increases because the rotor comes in contact with the bearing surface. Wear in journal bearings affects their characteristics because of its influence on the thickness of the fluid film. This influence can be detected in the dynamic behavior of the rotor and especially in the dynamic stiffness and damping coefficients. The paper aims to discuss these issues. Design/methodology/approach – In this paper, the effect of wear on the rotor dynamic stiffness and damping coefficients (K and C) of a short journal bearing is investigated. K and C in this work are estimated by using two methods a semi-analytical method and finite element (FE) analysis implemented in the ANSYS software. Findings – The main goal of this research is to make the identification of wear in journal bearings feasible by observing the alternation of their dynamic coefficients. Both of the methods implemented are proven to be useful, while FE analysis can provide more accurate results. Originality/value – This paper is original and has not been published elsewhere.

Dynamic Stiffness and Damping Coefficients of Aerostatic, Porous, Journal Bearings

1978 ◽  
Vol 20 (5) ◽  
pp. 291-296 ◽  
Author(s):  
N. S. Rao ◽  
B. C. Majumdar
Keyword(s):  
Continuity Equation ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Dynamic Pressure ◽  
Dynamic Stiffness ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Damping Coefficients ◽  
Design Charts ◽  
Stiffness And Damping

A periodic (displacement) disturbance is imposed on an aerostatic, porous, journal bearing of finite length under steady-state conditions. The dynamic pressure distribution is obtained by a pressure perturbation analysis of Reynolds equation and a modified flow continuity equation in a porous medium. Dynamic stiffness and damping coefficients for different operating conditions are calculated numerically, using a digital computer, and presented in the form of design charts.

Dynamic Stiffness and Damping of Externally Pressurized Gas Lubricated Journal Bearings

1977 ◽  
Vol 99 (1) ◽  
pp. 101-105 ◽  
Author(s):  
David P. Fleming ◽  
William J. Thayer ◽  
Robert E. Cunningham
Keyword(s):  
Dynamic Stiffness ◽  
Journal Bearings ◽  
Vertical Shaft ◽  
Small Eccentricity ◽  
Damping Coefficients ◽  
Supply Pressure ◽  
High Speeds ◽  
Angle Data ◽  
Stiffness And Damping ◽  
Gas Supply

A rigid vertical shaft was operated with known amounts of unbalance at speeds up to 30,000 rpm and gas supply pressure ratios to 4.8. From measured amplitude and phase angle data, dynamic stiffness and damping coefficients of the bearings were determined. The measured stiffness was proportional to the supply pressure, while damping was little affected by supply pressure. Damping dropped rapidly as the fractional frequency whirl threshold was approached. A small eccentricity analysis overpredicted the stiffness by 4 to 55 percent. Predicted damping was close to measured at low speeds but higher at high speeds.

Calculation and Measurement of the Stiffness and Damping Coefficients for a Low Impedance Hydrodynamic Bearing

1997 ◽  
Vol 119 (1) ◽  
pp. 57-63 ◽  
Author(s):  
M. J. Goodwin ◽  
P. J. Ogrodnik ◽  
M. P. Roach ◽  
Y. Fang
Keyword(s):  
Experimental Data ◽  
Dynamic Stiffness ◽  
Perturbation Technique ◽  
The Novel ◽  
Oil Film ◽  
Hydrodynamic Bearing ◽  
Damping Coefficients ◽  
Stiffness And Damping ◽  
Film Stiffness ◽  
Novel Design

This paper describes a combined theoretical and experimental investigation of the eight oil film stiffness and damping coefficients for a novel low impedance hydrodynamic bearing. The novel design incorporates a recess in the bearing surface which is connected to a standard commercial gas bag accumulator; this arrangement reduces the oil film dynamic stiffness and leads to improved machine response and stability. A finite difference method was used to solve Reynolds equation and yield the pressure distribution in the bearing oil film. Integration of the pressure profile then enabled the fluid film forces to be evaluated. A perturbation technique was used to determine the dynamic pressure components, and hence to determine the eight oil film stiffness and damping coefficients. Experimental data was obtained from a laboratory test rig in which a test bearing, floating on a rotating shaft, was excited by a multi-frequency force signal. Measurements of the resulting relative movement between bearing and journal enabled the oil film coefficients to be measured. The results of the work show good agreement between theoretical and experimental data, and indicate that the oil film impedance of the novel design is considerably lower than that of a conventional bearing.

The Surface Roughness Effect on the Dynamic Stiffness and Damping Characteristics of the Hydrostatic Thrust Spherical Bearings: Part 5 of 5 — Clearance Type of Bearings

2007 ◽  
Author(s):  
Ahmad W. Yacout
Keyword(s):  
Surface Roughness ◽  
Capillary Tube ◽  
Dynamic Stiffness ◽  
Dynamic Performance ◽  
Major Effect ◽  
Design Parameters ◽  
Compressibility Effect ◽  
Damping Coefficients ◽  
Stiffness And Damping ◽  
Fluid Compressibility

This study has theoretically analyzed the surface roughness, centripetal inertia and recess volume fluid compressibility effects on the dynamic behavior of a restrictor compensated hydrostatic thrust spherical clearance type of bearing. The stochastic Reynolds equation, with centripetal inertia effect, and the recess flow continuity equation with recess volume fluid compressibility effect have been derived to take into account the presence of roughness on the bearing surfaces. On the basis of a small perturbations method, the dynamic stiffness and damping coefficients have been evaluated. In addition to the usual bearing design parameters the results for the dynamic stiffness and damping coefficients have been calculated for various frequencies of vibrations or squeeze parameter (frequency parameter) and recess volume fluid compressibility parameter. The study shows that both of the surface roughness and the centripetal inertia have slight effects on the stiffness coefficient and remarkable effects on the damping coefficient while the recess volume fluid compressibility parameter has the major effect on the bearing dynamic characteristics. The cross dynamic stiffness showed the bearing self-aligning property and the ability to oppose whirl movements. The orifice restrictor showed better dynamic performance than that of the capillary tube.

Porous Wall Gas Lubricated Journal Bearings: Theoretical Investigation

1979 ◽  
Vol 101 (4) ◽  
pp. 458-465 ◽  
Author(s):  
E. P. Gargiulo
Keyword(s):  
Experimental Investigation ◽  
Dynamic Stiffness ◽  
Porous Wall ◽  
Companion Paper ◽  
Journal Bearings ◽  
Damping Properties ◽  
Governing Equations ◽  
Performance Curves ◽  
Unsteady Characteristics ◽  
Stiffness And Damping

A model has been developed to compute the dynamic stiffness and damping properties of externally pressurized, porous-wall, gas journal bearings which includes the effects of journal rotation and eccentricity. This paper presents the derivation of the governing equations and the perturbation analysis used to find the unsteady characteristics. Typical nondimensional performance curves are found and the influences of seven governing parameters are discussed. A companion paper describes an experimental investigation of porous journal bearings.

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