Approximate Analysis of Turbulent Hybrid Bearings. Static and Dynamic Performance for Centered Operation

1990 ◽  
Vol 112 (4) ◽  
pp. 692-698 ◽  
Author(s):  
Luis San Andre´s
Keyword(s):  
Analytical Study ◽  
Dynamic Performance ◽  
Journal Bearings ◽  
Dynamic Force ◽  
Force Response ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Numerical Predictions ◽  
Hybrid Bearing ◽  
Close Form

An analytical study for the flow and dynamic force response in turbulent hybrid journal bearings is presented. Fluid inertia effects at the recess edges and film lands are included. For small amplitude motions about the centered position, the equations for the flow on the film lands and recesses are solved in close form by invoking the thin-land assumption. Predictions from the present simplified analytical theory agree well with full numerical predictions. The effect of recess pressure on the dynamic force response of a L02 hybrid bearing is discussed in detail.

Dynamic Characterization of an Integral Squeeze Film Bearing Support Damper for a Supercritical CO2 Expander

2017 ◽  
Author(s):  
Bugra Ertas ◽  
Adolfo Delgado ◽  
Jeffrey Moore
Keyword(s):  
High Speed ◽  
Dynamic Performance ◽  
Mechanical Impedance ◽  
Squeeze Film ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Damping Behavior ◽  
Impedance Testing ◽  
Stiffness And Damping ◽  
Onset Of Cavitation

The present work advances experimental results and analytical predictions on the dynamic performance of an integral squeeze film damper (ISFD) for application in a high-speed super-critical CO2 (sCO2) expander. The test campaign focused on conducting controlled orbital motion mechanical impedance testing aimed at extracting stiffness and damping coefficients for varying end seal clearances, excitation frequencies, and vibration amplitudes. In addition to the measurement of stiffness and damping; the testing revealed the onset of cavitation for the ISFD. Results show damping behavior that is constant with vibratory velocity for each end seal clearance case until the onset of cavitation/air ingestion, while the direct stiffness measurement was shown to be linear. Measurable added inertia coefficients were also identified. The predictive model uses an isothermal finite element method to solve for dynamic pressures for an incompressible fluid using a modified Reynolds equation accounting for fluid inertia effects. The predictions revealed good correlation for experimentally measured direct damping, but resulted in grossly overpredicted inertia coefficients when compared to experiments.

Thermohydrodynamic Analysis of Process-Liquid Hydrostatic Journal Bearings in Turbulent Regime, Part I: The Model and Perturbation Analysis

1995 ◽  
Vol 62 (3) ◽  
pp. 674-678 ◽  
Author(s):  
Zhou Yang ◽  
L. San Andres ◽  
D. W. Childs
Keyword(s):  
Energy Equation ◽  
Dynamic Performance ◽  
Journal Bearings ◽  
Fluid Film ◽  
Turbulent Regime ◽  
Fluid Inertia ◽  
Flow Process ◽  
Fluid Film Bearings ◽  
Friction Factors ◽  
Flow Turbulence

A bulk-flow thermohydrodynamic (THD) analysis is developed for prediction of the static and dynamic performance characteristics of turbulent-flow, process-liquid, hydrostatic journal bearings (HJBs). Pointwise evaluation of temperature and hence liquid properties is achieved through the solution of the energy equation in the fluid film with insulated boundaries, and justified for fluid film bearings with external pressurization. Fluid inertia within the film lands and at recess edges is preserved in the analysis. Flow turbulence is accounted through turbulence shear parameters based on friction factors derived from Moody’s formulae. The effects of fluid compressibility and temperature variation in the bearing recesses are included. Numerical solution and results are presented in the second part of this work and compared with some limited experimental data for a liquid hydrogen (LH2) bearing.

Stability of Multirecess Hybrid-Operating Oil Journal Bearings

1985 ◽  
Vol 107 (1) ◽  
pp. 116-121 ◽  
Author(s):  
Y. S. Chen ◽  
H. Y. Wu ◽  
P. L. Xie
Keyword(s):  
Finite Difference Method ◽  
Dynamic Performance ◽  
Journal Bearings ◽  
Design Parameters ◽  
Stability Threshold ◽  
Damping Coefficients ◽  
Hybrid Bearing ◽  
The Stability ◽  
Stiffness And Damping ◽  
Bearing System

An analysis and a numerical solution using finite difference method to predict the dynamic performance of multirecess hybrid-operating oil journal bearings are presented. The linearized stiffness and damping coefficients of a typical capillary-compensated bearing with four recesses are computed for various design parameters. The corresponding stiffness and the stability threshold of the bearing are then obtained, and the opposite influences of the hydrodynamic action on them are demonstrated. The effect of rotor flexibility on the onset of self-excited whirl is discussed, and a method is given to determine the stability threshold of a rotor-hybrid bearing system.

Theoretical Investigation of Fluid Inertia Effects and Stability of Self-Acting Gas Journal Bearings

1999 ◽  
Vol 121 (4) ◽  
pp. 836-843 ◽  
Author(s):  
G. Belforte ◽  
T. Raparelli ◽  
V. Viktorov
Keyword(s):  
Reynolds Equation ◽  
Equation Of Motion ◽  
Journal Bearings ◽  
Fluid Inertia ◽  
Stability Parameters ◽  
Inertia Effects ◽  
Stability Diagrams ◽  
Intensive Use ◽  
Stability Limits ◽  
Theoretical Results

The journal equation of motion and the complete Reynolds equation of compressible fluid film are numerically solved and a computer program is developed. The formulas are for externally pressurized bearings, but results are shown only for self-acting bearings. For certain cases, the validity of the theoretical results is verified by comparison with the experimental data available from the literature. Through intensive use of the program, journal center trajectories are obtained and effects of fluid inertia are investigated. New stability parameters are presented and stability diagrams are established for bearings with L/D = 0.25, 0.5, 1, 1.5, and 2. The rotor unbalance effects on bearing stability limits are illustrated for several cases.

Turbulent Hybrid Bearings With Fluid Inertia Effects

1990 ◽  
Vol 112 (4) ◽  
pp. 699-707 ◽  
Author(s):  
Luis San Andre´s
Keyword(s):  
High Speed ◽  
Load Capacity ◽  
Pressure Rise ◽  
Reynolds Numbers ◽  
Dynamic Force ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Friction Factors ◽  
Region Flow ◽  
The Stability

High speed hybrid bearings for cryogenic applications demand large levels of external pressurization to provide substantial load capacity. These conditions give rise to large film Reynolds numbers, and thus, cause the fluid flow within the bearing film to be turbulent and dominated by fluid inertia effects both at the recess edges and at the thin film lands. The analysis includes the effect of recess fluid compressibility and a model for the pressure rise within the recess region. Flow turbulence is simulated by friction factors dependent on the local Reynolds numbers and surface conditions. A perturbation method is used to calculate the zeroth and first flow fields and determine the bearing steady-state and dynamic force response. Comparison of results with existing experimental data shows the accuracy of the present full inertial-turbulent analysis. A roughened bearing surface is shown to improve considerably the stability characteristics of hybrid bearings operating at high speeds.

Analysis of Hydrostatic Journal Bearings With End Seals

1992 ◽  
Vol 114 (4) ◽  
pp. 802-811 ◽  
Author(s):  
L. A. San Andres
Keyword(s):  
Journal Bearings ◽  
Squeeze Film ◽  
Dynamic Force ◽  
Jet Engines ◽  
Fluid Inertia ◽  
Active Device ◽  
Typical Application ◽  
Liquid Compressibility ◽  
Squeeze Film Dampers ◽  
Direct Stiffness

An approximate analysis for the pressure field and dynamic force coefficients in turbulent flow, centered hydrostatic journal bearings (HJBs) with fluid inertia and liquid compressibility effects is presented. Results from the analysis show that HJBs with end seals have increased damping, better dynamic stability characteristics, as well as lower flow rates, than conventional HJBs. However, hydrostatic (direct) stiffness may be lost if excessively tight end seals are used. End seals are shown to compensate for the effect of liquid compressibility within the recess volume, and prescribe a net reduction in the whirl frequency ratio for hybrid operation. Hydrostatic squeeze film dampers (HSFD) with end seals are shown to be a viable alternative in applications where a tight control of the bearing leakage is important such as in jet-engines. Furthermore, HSFDs with end seals could be used as an active device to control the available damping in a typical application.

Evaluation of Various Approximate Solutions for Fluid Inertia Effects on the Dynamic Performance of a Stepped Thrust Bearing

1985 ◽  
Vol 107 (1) ◽  
pp. 39-45 ◽  
Author(s):  
Y. Haruyama ◽  
T. Kazamaki ◽  
A. Mori ◽  
H. Mori
Keyword(s):  
Film Thickness ◽  
Thrust Bearing ◽  
Stokes Equations ◽  
Dynamic Performance ◽  
Approximate Solutions ◽  
Time Dependent ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Dependent Term ◽  
Wide Range

Based on the Navier-Stokes equations in which the pressure is assumed to be constant across the film thickness, various approximate solutions and the exact one for the dynamic performance of an infinitely wide, stepped thrust bearing in a laminar flow regime are presented under the assumption of a small harmonic vibration. From comparison of the approximate solutions with the exact one, it is concluded that some kind of averaging approach in which the time dependent term is treated exactly while the convective inertia terms are averaged out across the film thickness gives close approximations in a wide range of designing conditions, and that the other kind of averaging approach in which all the inertia terms including the time dependent term are averaged out across the film thickness gives fairly good approximations.

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