Compressible Squeeze Films and Squeeze Bearings

1964 ◽  
Vol 86 (2) ◽  
pp. 355-364 ◽  
Author(s):  
E. O. J. Salbu
Keyword(s):  
Steady State ◽  
Finite Difference ◽  
Journal Bearings ◽  
Squeeze Film ◽  
Thrust Bearings ◽  
Finite Difference Solution ◽  
Squeeze Number ◽  
Gas Bearing ◽  
Compressibility Effects ◽  
Piezoelectric Devices

Experimental agreement with a finite-difference solution of the isothermal squeeze film equation was obtained for steady-state sinusoidal squeeze motion of parallel, coaxial disks. At low squeeze number, the film force is in phase with the velocity; at high squeeze number, with the displacement. Compressibility effects at high squeeze number introduce a superambient mean film pressure, so that it is possible to operate a gas bearing on squeeze effects alone. Thrust bearings, spherical bearings, and journal bearings have been successfully operated as squeeze bearings, using both electromagnetic and piezoelectric devices to generate the squeeze motion.

On the Physical Meanings of Λ/Q˜p0 and σ/Q˜p0 in Molecular Gas Film Lubrication Problems

1996 ◽  
Vol 118 (2) ◽  
pp. 364-369 ◽  
Author(s):  
S. Fukui ◽  
R. Matsuda ◽  
R. Kaneko
Keyword(s):  
Flow Rate ◽  
Squeeze Film ◽  
Molecular Gas ◽  
Thrust Bearings ◽  
Molecular Gas Film Lubrication ◽  
Lubrication Characteristics ◽  
Bearing Number ◽  
Squeeze Number ◽  
Film Lubrication ◽  
The Continuum

To estimate molecular gas film lubrication (MGL) characteristics, we propose a modified bearing number Λ′ and a modified squeeze number σ′, which are, respectively, the conventional bearing Λ and squeeze number σ divided by the relative Poiseuille flow rate Q˜p0. Using Λ′ and σ′, the linearized MGL problem can be reduced to the continuum gas film lubrication problem and the MGL characteristics can be exactly estimated, if the characteristic flow rate corresponding to the spacing, Q˜p0, is known. For nonlinear MGL problems, the lubrication characteristics can be verified to be roughly estimated by Λ′ and σ′ both in rectangular slider bearings and in circular squeeze-film thrust bearings.

Stability and Unbalance Response of Centrally Preloaded Rotors Mounted in Journal and Squeeze Film Bearings

1979 ◽  
Vol 101 (2) ◽  
pp. 120-128 ◽  
Author(s):  
E. J. Hahn
Keyword(s):  
Steady State ◽  
Vibration Isolation ◽  
Journal Bearings ◽  
Squeeze Film ◽  
State Behavior ◽  
Unbalance Response ◽  
Radial Stiffness ◽  
Rolling Element ◽  
Orbit Eccentricity ◽  
Vertical Bearing

The unbalance response and stability of centrally preloaded symmetric rigid rotors are investigated. Steady state solutions for unbalance transmissibilities, orbit eccentricity radii, and stability are presented for rotors running in hydrodynamic journal bearings and in rolling element bearings which are supported in squeeze film bearings. The Ocvirk and Warner approximations are used to evaluate the fluid film forces, rendering the data applicable to any length/diameter ratio. Both pressurized (2π film) and unpressurized (π film) oil supply are considered. Pressurization has a far reaching influence on the steady state behavior of both journal and squeeze film bearings. For unpressurized bearings, conditions of multistable operation and for stability are depicted, with journal bearings exhibiting ‘half frequency whirl’ possibilities as well. The error involved in predicting vertical bearing behavior by assuming an equivalent unidirectional load equal to the unbalance load is demonstrated. For pressurized bearings multistable operation is eliminated but both squeeze film and journal bearings are unstable for most length/diameter ratios in the absence of external radial stiffness. The stabilizing effect of superimposed external radial stiffness on pressurized bearings is clearly demonstrated. While pressurized journal bearings can run stably, they are less suited than pressurized squeeze film bearings for vibration isolation.

A Finite Element Method for the Calculation of Locus Paths in Dynamically Loaded Bearings

1973 ◽  
Vol 187 (1) ◽  
pp. 79-86 ◽  
Author(s):  
P. D. Shelly ◽  
C. Ettles
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Finite Elements ◽  
Finite Difference ◽  
Pressure Profile ◽  
Journal Bearings ◽  
Axial Pressure ◽  
Satisfactory Approximation ◽  
Finite Difference Solution ◽  
Predictor Corrector

A method using finite elements for the solution of journal bearings is outlined. The special properties of an exponentially shaped element are used together with a satisfactory approximation for the axial pressure profile. This approach is one hundred times faster than a conventional finite difference solution of equivalent accuracy. The method can be applied to the solution of locus paths for journal bearings under external dynamic load or under whirl conditions. The predictor-corrector method used to march out a locus path is briefly outlined and several typical loci are presented as examples.

A Rotordynamic, Thermal, and Thrust Load Performance Gas Bearing Test Rig and Test Results for Tilting Pad Journal Bearings and Spiral Groove Thrust Bearings

2016 ◽  
Author(s):  
Aaron M. Rimpel ◽  
Giuseppe Vannini ◽  
Jongsoo Kim
Keyword(s):  
Thrust Bearing ◽  
Journal Bearings ◽  
Temperature Gradients ◽  
Spiral Groove ◽  
Test Rig ◽  
Thrust Bearings ◽  
Tilting Pad ◽  
Gas Bearing ◽  
Thrust Load ◽  
Tilting Pad Journal Bearings

A high speed gas bearing test rig was developed to characterize rotordynamic, thermal, and thrust load performance of gas bearings being developed for an oil-free turboexpander. The radial bearings tested in this paper were tilting pad journal bearings with radial compliance features that allow the bearing bore to increase to accommodate shaft growth, and the thrust bearings were a spiral groove type with axial compliance features. The thrust bearing accounts for over 90% of the combined bearing power consumption, which has a cubic relationship with speed and increases with case pressure. Radial bearing circumferential pad temperature gradients increased approximately with speed to the fourth or fifth power, with slightly higher temperature rise for lower case pressure. Maximum steady state bearing pad temperatures increase with increasing speed for similar cooling mass flow rates; however, only the thrust bearing showed a significant increase in temperature with higher case pressure. The thrust bearings were stable at all speeds, but the load capacity was found to be lower than anticipated, apparently due to pad deformations caused by radial temperature gradients in the stator. More advanced modeling approaches have been proposed to better understand the thrust bearing thermal behavior and to improve the thrust bearing design. Finally, the radial bearings tested were demonstrated to be stable up to the design speed of 130 krpm, which represents the highest surface speed for tilting pad gas bearings tested in the literature.

A Novel Variable Impedance Hydrodynamic Oil-Film Bearing: Part 1: Theoretical Modelling

1996 ◽  
Vol 210 (1) ◽  
pp. 55-63 ◽  
Author(s):  
P J Ogrodnik ◽  
M J Goodwin ◽  
M P Roach ◽  
Y Fang
Keyword(s):  
Steady State ◽  
Finite Difference ◽  
Theoretical Modelling ◽  
Operating Characteristics ◽  
Operating Modes ◽  
Rotating Machine ◽  
Dynamic Operating ◽  
Finite Difference Solution ◽  
Bearing Design

A novel bearing design is presented. The bearing consists of a partial arc bearing into which two recesses are machined. Attached to the two recesses, via remote-controlled valves, are two accumulators. The ability to be able to open and close the valves gives the new bearing design four independent operating modes. Steady state operating characteristics for the bearing were predicted using a finite difference solution to Reynolds' equation. A new mathematical model is proposed for the recess boundary. The model is based on flow continuity and enables a finite difference node to be positioned on the recess boundary. It is demonstrated that the theoretical model proposed predicts steady state characteristics which agree favourably with previously published work and with experimental data. The model was further utilized, in a pressure perturbation algorithm, to obtain predictions of the bearing's dynamic operating characteristics. It is demonstrated that by switching the valves from open to closed, or vice versa, the bearing's characteristics can be altered in situ. It is also demonstrated that the inclusion of the recesses and accumulators has little effect on the steady state characteristics when compared to those of a conventional partial arc bearing. It is suggested that the bearing design proposed in this paper has major advantages to offer the rotating machine designer. Use of the bearing enables the operator to vary support characteristics without major re-machining. Furthermore, support characteristics may be varied in situ, without significant cost penalties and with little additional maintenance overheads.

scholarly journals Finite Difference Solution of Unsteady Flow Past an Oscillating Semi-Infinite Vertical Plate with Variable Surface Temperature and Uniform Mass Flux

2014 ◽  
Vol 19 (4) ◽  
pp. 709-724 ◽  
Author(s):  
R. Muthucumaraswamy ◽  
B. Saravanan
Keyword(s):  
Steady State ◽  
Finite Difference ◽  
Unsteady Flow ◽  
Thermal Radiation ◽  
Mass Flux ◽  
Vertical Plate ◽  
Grashof Number ◽  
Flow Past ◽  
Finite Difference Solution ◽  
Difference Solution

Abstract A finite difference solution of an unsteady flow past an oscillating semi-infinite vertical place with variable temperature and uniform mass flux is presented here. The fluid considered here is a gray, absorbing-emitting radiation but a non-scattering medium. The dimensionless governing equations are solved by an efficient, more accurate, and unconditionally stable and fast converging implicit scheme. The steady state velocity, temperature and concentration profiles are shown graphically. The effect of velocity and temperature for different physical parameters such as the thermal radiation, Schmidt number, thermal Grashof number and mass Grashof number is studied. It is observed that the velocity decreases in the presence of thermal radiation. It is also observed that the time taken to reach a steady-state is more in the case of vertical plate than horizontal plate.

A Rotordynamic, Thermal, and Thrust Load Performance Gas Bearing Test Rig and Test Results for Tilting Pad Journal Bearings and Spiral Groove Thrust Bearings

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Aaron M. Rimpel ◽  
Giuseppe Vannini ◽  
Jongsoo Kim
Keyword(s):  
Journal Bearings ◽  
Spiral Groove ◽  
Test Rig ◽  
Radial Temperature ◽  
Gas Bearings ◽  
Thrust Bearings ◽  
Tilting Pad ◽  
Gas Bearing ◽  
Thrust Load ◽  
Tilting Pad Journal Bearings

A high-speed gas bearing test rig was developed to characterize rotordynamic, thermal, and thrust load performance of gas bearings being developed for an oil-free turboexpander. The radial bearings (RBs) tested in this paper were tilting pad journal bearings with radial compliance features that allow the bearing bore to increase to accommodate shaft growth, and the thrust bearings (TBs) were a spiral groove type with axial compliance features. The TB accounts for over 90% of the combined bearing power consumption, which has a cubic relationship with speed and increases with case pressure. RB circumferential pad temperatures increased approximately with speed to the fourth or fifth power, with slightly higher temperature rise for lower case pressure. Maximum steady-state bearing pad temperatures increase with increasing speed for similar cooling mass flow rates; however, only the TB showed a significant increase in temperature with higher case pressure. The TBs were stable at all speeds, but the load capacity was found to be lower than anticipated, apparently due to pad deformations caused by radial temperature gradients in the stator. More advanced modeling approaches have been proposed to better understand the TB thermal behavior and to improve the TB design. Finally, the RBs tested were demonstrated to be stable up to the design speed of 130 krpm, which represents the highest surface speed for tilting pad gas bearings tested in the literature.

Load Support of Spherical Squeeze-Film Gas Bearings

1969 ◽  
Vol 91 (1) ◽  
pp. 132-137 ◽  
Author(s):  
J. V. Beck ◽  
C. L. Strodtman
Keyword(s):  
Steady State ◽  
Finite Difference ◽  
Small Parameter ◽  
Ambient Pressure ◽  
Polar Axis ◽  
Squeeze Film ◽  
Ph Distribution ◽  
Gas Bearings

The steady-state ph distribution and the load support capability for a squeeze-film bearing in the form of a sphere, or portions of a sphere, are given for two cases, (a) when the sphere pulsates radially and (b) when the sphere motion is along the polar axis. Both small parameter and finite-difference results are given for loads in the radial and polar directions. It is shown that considerably more load support in both the radial and the polar directions is developed when the sphere pulsates radially. It is further shown that the load support can be improved by removing a portion of the sphere near the pole, thus venting the bearing to the ambient pressure.

Sign in / Sign up

Export Citation Format

Share Document