The Effects of Wear on the Rotordynamic Coefficients of a Hydrostatic Journal Bearing

1991 ◽  
Vol 113 (1) ◽  
pp. 210-213 ◽  
Author(s):  
J. K. Scharrer ◽  
R. F. Hecht ◽  
R. I. Hibbs
Keyword(s):  
Turbulent Flow ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Liquid Hydrogen ◽  
Radial Clearance ◽  
Hydrostatic Bearing ◽  
Rotordynamic Coefficients ◽  
Analytical Results

Reynolds equation is solved for the turbulent flow of liquid hydrogen through an orifice compensated hydrostatic bearing with a worn stator element. The clearance function for the worn bearing is defined by the depth and circumferential location of wear and the resulting intersection of the journal and housing radii. Analytical results are presented for stiffness, damping and leakage as a function of bearing wear. The results show that the performance of the bearing degrades steadily for wear amounts greater than 5 percent of the radial clearance and is relatively insensitive to the geometrical location of the wear.

Effect of wear on the performance of hole entry hybrid conical journal bearing employing constant flow valve compensation

2019 ◽  
Vol 233 (9) ◽  
pp. 1277-1292 ◽  
Author(s):  
Sanjay R Pawar ◽  
Vikas M Phalle
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Load Capacity ◽  
Radial Clearance ◽  
Constant Flow ◽  
Performance Parameters ◽  
Element Analysis ◽  
Spherical Coordinate ◽  
Flow Valve

Hybrid bearings gets worn gradually during the start and stop operation. This wearing leads to change in the geometry of bearing and affects the radical clearance as well as fluid film thickness. Therefore, these discontinuities in the radial clearance can influence the performance characteristics. With the purpose of preventing irreparable failure state of bearing assembly, it is essential to concentrate on the actual changes in the performance parameters of hole entry hybrid conical journal bearing due to wear. In this context, the main aim of this analysis is to predict the performance of hole entry hybrid conical journal bearing employing constant flow valve compensation. Modified Reynolds equation in spherical coordinate form is used to govern the flow of lubricant in the narrow region between journal and conical bearing. The solution to this Reynolds equation is obtained by finite element analysis with appropriate boundary conditions. This paper summarizes that for a given bearing with constant flow valve as compensating element, the wear causes variation in lubricant film thickness, which strongly affects load capacity, pressure generated, and dynamic performance parameters.

Influence of geometric imperfection of journal on the performance of porous hybrid journal bearing under turbulent condition

2020 ◽  
pp. 135065012097642
Author(s):  
Anil Singh ◽  
Satish C Sharma
Keyword(s):  
Turbulent Flow ◽  
Flow Condition ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Performance Parameters ◽  
Geometric Imperfection ◽  
Damping Coefficients ◽  
Turbulent Condition ◽  
Stiffness And Damping ◽  
Rotor Dynamic

The present work deals with numerical investigation into geometric imperfection (bellmouth, undulation and barrel shape) of the journal on performance of a porous hybrid journal bearing system (PHJBs) operating under turbulent flow condition. The Reynolds equation governing the flow of lubricant in the bearing clearance space is modified by using the turbulent lubrication theory proposed by Constantinescu’s. The bearing performance parameters are numerically computed using FEM. The effects of geometric irregularities, turbulent flow condition, and permeability parameters have been investigated on the performance of PHJBs. The theoretically obtained results indicates that the combined effect of turbulent flow condition and geometric imperfection offers enhanced values of [Formula: see text] and rotor dynamic coefficients (stiffness and damping coefficients).

scholarly journals Measurements Versus Predictions for the Static and Dynamic Characteristics of a Four-Pad, Rocker-Pivot, Tilting-Pad Journal Bearing

2013 ◽  
Author(s):  
David P. Tschoepe ◽  
Dara W. Childs
Keyword(s):  
Journal Bearing ◽  
Dynamic Stiffness ◽  
Radial Clearance ◽  
Static And Dynamic Characteristics ◽  
Rotordynamic Coefficients ◽  
Stiffness Coefficients ◽  
Bearing Clearance ◽  
Tilting Pad ◽  
Frequency Independent ◽  
Tilting Pad Journal Bearing

Measured and predicted static and dynamic characteristics are provided for a four-pad, rocker-pivot, tilting-pad journal bearing in the load-on-pad and load-between-pad orientations. The bearing has the following characteristics: 4 pads, .57 pad pivot offset, 0.6 L/D ratio, 60.33 mm (2.375in) pad axial length, 0.08255 mm (0.00325 in) radial clearance in the load-on-pad orientation, and 0.1189 mm (0.00468 in) radial clearance in the load-between-pad orientation. Tests were conducted on a floating test bearing design with unit loads ranging from 0 to 2903 kPa (421.1 psi) and speeds from 6.8 to 13.2 krpm. For all rotor speeds, hot-clearance measurements were taken to show the reduction in bearing clearance due to thermal expansion of the shaft and pads during testing. As the testing conditions get hotter, the rotor, pads, and bearing expand, decreasing radial bearing clearance. Hot-clearance measurements showed a 16–25% decrease in clearance compared to a clearance measurement at room temperature. To look at the radial thermal gradient in the loaded pad, embedded thermocouples were inserted inside the bearing pad near the bearing housing. Results showed a 5–25°C decrease in temperature from the rotor side of the pad to the temperatures near the bearing housing. This radial temperature gradient caused an uneven thermal deflection in the pad, changing the pads’ radii of curvature. For all test conditions, dynamic tests were performed over a range of excitation frequencies to obtain complex dynamic stiffness coefficients as a function of frequency. The direct real dynamic stiffness coefficients were then fitted with a quadratic function with respect to frequency. From the curve fit, the frequency dependence was captured by including a virtual-mass matrix [M] to produce a frequency independent [K][C][M] model. The direct dynamic stiffness coefficients for the load-on-pad orientation showed significant orthotropy, while the load-between-pad did not. The load-between-pad showed slight orthotropy as load increased. Experimental cross-coupled stiffness coefficients were measured in both load orientations, but were of the same sign and significantly less than direct stiffness coefficients. In both orientations the imaginary part of the measured dynamic stiffness increased linearly with increasing frequency, allowing for frequency-independent direct damping coefficients. Rotordynamic coefficients presented were compared to predictions from two Reynolds-based models. The models showed the importance of taking into account pivot contact flexibility and different pad geometries (due to the reduction in bearing clearance during testing) in predicting rotordynamic coefficients. If either of these two inputs were incorrect, then predictions for the bearings impedance coefficients were very inaccurate.

A General Solution of Reynolds’ Equation for a Full Finite Journal Bearing

1967 ◽  
Vol 89 (2) ◽  
pp. 203-210 ◽  
Author(s):  
R. R. Donaldson
Keyword(s):  
Fourier Series ◽  
Series Solution ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Load Capacity ◽  
Separation Of Variables ◽  
Hill Equation ◽  
Eigenvalues And Eigenvectors ◽  
General Series ◽  
Bearing Load

Reynolds’ equation for a full finite journal bearing lubricated by an incompressible fluid is solved by separation of variables to yield a general series solution. A resulting Hill equation is solved by Fourier series methods, and accurate eigenvalues and eigenvectors are calculated with a digital computer. The finite Sommerfeld problem is solved as an example, and precise values for the bearing load capacity are presented. Comparisons are made with the methods and numerical results of other authors.

Theoretical Condition for the Cxy=Cyx Relation in Fluid Film Journal Bearings

1989 ◽  
Vol 111 (3) ◽  
pp. 426-429 ◽  
Author(s):  
T. Kato ◽  
Y. Hori
Keyword(s):  
Reynolds Equation ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Fluid Film ◽  
Finite Width ◽  
Damping Coefficients ◽  
Dynamic Coefficients ◽  
Cross Terms ◽  
Linear Damping ◽  
Theoretical Condition

A computer program for calculating dynamic coefficients of journal bearings is necessary in designing fluid film journal bearings and an accuracy of the program is sometimes checked by the relation that the cross terms of linear damping coefficients of journal bearings are equal to each other, namely “Cxy = Cyx”. However, the condition for this relation has not been clear. This paper shows that the relation “Cxy = Cyx” holds in any type of finite width journal bearing when these are calculated under the following condition: (I) The governing Reynolds equation is linear in pressure or regarded as linear in numerical calculations; (II) Film thickness is given by h = c (1 + κcosθ); and (III) Boundary condition is homogeneous such as p=0 or dp/dn=0, where n denotes a normal to the boundary.

The Effect of Lubricant Inertia in Journal-Bearing Lubrication

1957 ◽  
Vol 24 (4) ◽  
pp. 494-496
Author(s):  
J. F. Osterle ◽  
Y. T. Chou ◽  
E. A. Saibel
Keyword(s):  
Reynolds Number ◽  
Steady State ◽  
Reynolds Equation ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Hydrodynamic Theory ◽  
Simple Relationship ◽  
Inertia Effect ◽  
Laminar Regime ◽  
Steady State Operation

Abstract The Reynolds equation of hydrodynamic theory, modified to take lubricant inertia into approximate account, is applied to the steady-state operation of journal bearings to determine the effect of lubricant inertia on the pressure developed in the lubricant. A simple relationship results, relating this “inertial” pressure to the Reynolds number of the flow. It is found that the inertia effect can be significant in the laminar regime.

Numerical and Experimental Investigations on Preload Effects in Air Foil Journal Bearings

2017 ◽  
Author(s):  
Marcel Mahner ◽  
Pu Li ◽  
Andreas Lehn ◽  
Bernhard Schweizer
Keyword(s):  
Reynolds Equation ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Compressible Fluids ◽  
Experimental Investigations ◽  
Hysteresis Curves ◽  
Numerical Predictions ◽  
Bearing Stiffness ◽  
Gasdynamic Model ◽  
Good Agreement

A detailed elasto-gasdynamic model of a preloaded three-pad air foil journal bearing is presented. Bump and top foil deflections are herein calculated with a nonlinear beamshell theory according to Reissner. The 2D pressure distribution in each bearing pad is described by the Reynolds equation for compressible fluids. With this model, the influence of the assembly preload on the static bearing hysteresis as well as on the aerodynamic bearing performance is investigated. For the purpose of model validation, the predicted hysteresis curves are compared with measured curves. The numerically predicted and the measured hysteresis curves show a good agreement. The numerical predictions exhibit that the assembly preload increases the bearing stiffness (in particular for moderate shaft displacements) and the bearing damping.

A Theoretical Analysis of Floating Bush Journal Bearing With Axial Oil Film Rupture Being Considered

2002 ◽  
Vol 124 (3) ◽  
pp. 494-505 ◽  
Author(s):  
Kiyoshi Hatakenaka ◽  
Masato Tanaka ◽  
Kenji Suzuki
Keyword(s):  
Steady State ◽  
Reynolds Equation ◽  
Speed Ratio ◽  
Shaft Speed ◽  
Film Rupture ◽  
State Behavior ◽  
Oil Film ◽  
Rotordynamic Coefficients ◽  
The Stability ◽  
Very High

A new modified Reynolds equation is derived with centrifugal force acting on the hydrodynamic oil film being considered. This equation, together with a cavitation model, is used to obtain the steady-state equilibrium and calculate the rotordynamic coefficients of lightly loaded floating bush journal bearings operating at very high shaft speeds. The bush-to-shaft speed ratio and the linear cross-coupling spring coefficients of the inner oil film is found to decrease with the increase in shaft speed as the axial oil film rupture develops in the inner oil film. The present model can give reasonable explanation to the steady-state behavior and the stability behavior of the bearing observed in actual machines.

Influence of geometric parameters and operating conditions on the thermohydrodynamic behaviour of plain journal bearings

2000 ◽  
Vol 214 (5) ◽  
pp. 445-457 ◽  
Author(s):  
I Pierre ◽  
M Fillon
Keyword(s):  
High Speed ◽  
Journal Bearing ◽  
Three Dimensional ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Thermal Dissipation ◽  
Radial Clearance ◽  
Geometric Factors ◽  
Essential Components ◽  
Mass Flowrate

Hydrodynamic journal bearings are essential components of high-speed machinery. In severe operating conditions, the thermal dissipation is not a negligible phenomenon. Therefore, a three-dimensional thermohydrodynamic (THD) analysis has been developed that includes lubricant rupture and re-formation phenomena by conserving the mass flowrate. Then, the predictions obtained with the proposed numerical model are validated by comparison with the measurements reported in the literature. The effects of various geometric factors (length, diameter and radial clearance) and operating conditions (rotational speed, applied load and lubricant) on the journal bearing behaviour are analysed and discussed in order to inform bearing designers. Thus, it can be predicted that the bearing performance obtained highly depends on operating conditions and geometric configuration.

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