scholarly journals Running Characteristics of Aerodynamic Bearing with Self-Lifting Capability at Low Rotational Speed

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Tadeusz Adam Stolarski
Keyword(s):  
Fourier Transform ◽  
Journal Bearing ◽  
Static Model ◽  
The Self ◽  
Experimental Results ◽  
Squeeze Film ◽  
Film Pressure ◽  
Squeeze Film Effect ◽  
Time Marching ◽  
The Stability

An aerodynamic journal bearing that is capable of self-generating squeeze-film pressure is presented and its dynamic characteristics investigated numerically and experimentally. A numerical method based on a time-marching static model was applied to assess the orbit trajectory path of the rotor upon a perturbation. Experimental results were obtained to validate the effect of the self-generated squeeze-film pressure on the stability of the rotor. Analyzing the Fast Fourier Transform (FFT) responses of the rotor orbits enabled identification of self-excited whirling instabilities. Both numerical and experimental results showed that increasing the squeeze-film effect of the bearing could raise the threshold speed of instability.

An Experimental Method for the Determination of Journal-Bearing Stability Parameters. Part 2: Experiment

1979 ◽  
Vol 21 (3) ◽  
pp. 187-196 ◽  
Author(s):  
J. E. L. Simmons
Keyword(s):  
Experimental Method ◽  
Journal Bearing ◽  
Experimental Results ◽  
Air Bearing ◽  
Stability Parameters ◽  
Basic Principles ◽  
Underlying Theory ◽  
Stability Data ◽  
The Stability

The design of a flexibly mounted journal-bearing apparatus is described, and it is shown how the experimental results may be used to generate stability charts for design. For reasons of simplicity in demonstrating the basic principles, this work has been carried out using a plain circular air bearing. The underlying theory, however, is common to all journal-bearing systems, and it is intended to extend the experimental method to liquid-lubricated bearings and non-circular profiles. In addition to the stability data which have been obtained, the apparatus has enabled a detailed study of the phenomenon of whirl cessation.

scholarly journals Acoustic Journal Bearing With Changeable Geometry and Built-in Flexibility

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
T. A. Stolarski ◽  
M. Miyatake
Keyword(s):  
Performance Assessment ◽  
Journal Bearing ◽  
Squeeze Film ◽  
Film Pressure ◽  
Motion Stability ◽  
Start Up ◽  
Fatigue Endurance ◽  
Better Than

The influence of embodiment flexibility on the performance of an acoustic journal bearing is presented. Two completely different embodiments of the bearing were investigated using three criteria of performance assessment that is torque at the start-up, amount of separation due to squeeze film pressure, and motion stability of the shaft running at speed. The embodiment with built-in flexibility proved to perform far better than the bearing for which overall flexibility was much less. However, considerations pertinent to the easy of machining and fatigue endurance mitigate the ranking of performance of the two embodiments investigated.

Stability Characteristics of a Journal Bearing Mounted in an Uncentralized Squeeze Film Damper

1991 ◽  
Vol 113 (3) ◽  
pp. 584-589
Author(s):  
Yuichi Sato ◽  
H. Fujino ◽  
H. Sakakida ◽  
S. Hisa
Keyword(s):  
Steam Turbine ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Squeeze Film ◽  
Squeeze Film Damper ◽  
The Stability ◽  
Bearing Analysis

This paper describes the stability of a journal bearing mounted in an uncentralized squeeze film damper. It is known that mounting a journal bearing in a centralized squeeze film damper improves the bearing stability. From a practical viewpoint, however, it is difficult to centralize journal bearings which support a heavy rotor, such as a steam turbine. Experimentally, we show that a journal bearing can be stabilized by mounting in an uncentralized squeeze film damper. The effect of clearance of a squeeze film damper is investigated. By using short bearing analysis, rotor trajectories are calculated. Calculated results also shows stability improvement.

Stability of a Squeeze-Film Journal Bearing

1967 ◽  
Vol 89 (3) ◽  
pp. 369-373 ◽  
Author(s):  
J. V. Beck ◽  
C. L. Strodtman
Keyword(s):  
Journal Bearing ◽  
Mathieu Equation ◽  
Squeeze Film ◽  
Infinite Length ◽  
Driving Frequency ◽  
Numerical Techniques ◽  
Variational Techniques ◽  
Regions Of Stability ◽  
The Stability ◽  
Stability Limits

An investigation is made of the regions of stability for a compressible fluid, squeeze-film journal bearing of infinite length. Motion along one axis considered and the resulting dynamic equation is solved two ways: by variational techniques and by numerical techniques. The solution from the variational analysis can be approximated by a Mathieu equation thus showing that instability can occur at one-half the driving frequency. The numerical analysis shows the stability limits in terms of the load, drive amplitude, and dimensionless “mass.” The stability analysis is significant as there appears to be a rather large number of combinations of the parameters for which the squeeze-film journal is not stable. The stability characteristics of a squeeze-film bearing should, therefore, be examined carefully before application.

scholarly journals A Dynamical Study of a Rotor Supported by a Radial Journal Bearing Incorporating a Spherical Squeeze Film Damper

2021 ◽  
Vol 31 (5) ◽  
pp. 10-16
Keyword(s):  
Journal Bearing ◽  
Equations Of Motion ◽  
Spherical Shape ◽  
Squeeze Film ◽  
Dynamical Study ◽  
Squeeze Film Damper ◽  
Mechanical Waves ◽  
Squeeze Film Dampers ◽  
The Stability ◽  
Nonlinear Equations Of Motion

The reduction of noises, vibration, and mechanical waves transmitting through water from the shells of submarines is essential to their safe operation and travelling. Vibrations from the rotors of the engines are widely deemed as one of the main sources to which engineers have tried to attenuate with various designs. Squeeze-film dampers can be easily integrated into rotor-bearing structures in order to lower the level of vibrations caused by rotors out of balance. For this advantage, squeeze-film dampers are widely used in air-turbine engines. This paper presents preliminary results of a numerical simulation of a shaft running on a journal bearing integrated with a squeeze-film damper and evaluates the capacity in reducing vibrations concerning the stability of static equilibrium of the shaft journal center. The proposed damper is designed in spherical shape with self-aligning capacity. The results were obtained using finite difference method and numerical integration of the full nonlinear equations of motion.

Mass Conserving Cavitation Effects in Squeeze-Film Journal Bearings Subjected to Fully Reversing Loads

2010 ◽  
Author(s):  
S. Boedo
Keyword(s):  
Large Range ◽  
Journal Bearings ◽  
Experimental Results ◽  
Fluid Film ◽  
Squeeze Film ◽  
Threshold Pressure ◽  
Film Pressure ◽  
Time Histories ◽  
Cavitation Threshold ◽  
Good Agreement

This paper presents a study of cavitation effects associated with the performance of fluid-film journal bearings subjected to fully-reversing sinusoidal loading. Employing an established mass-conserving cavitation algorithm, it is observed that periodic time histories of journal eccentricity and maximum film pressure are strongly influenced by the process of cavitation formation and collapse. Good agreement of predicted and experimental results is obtained over a large range of loads for cavitation threshold pressure values typically associated with vapor cavitation.

Oscillation Loop for a Vibratory Gyroscope and Its Experiment Study

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Liu Heng ◽  
Su Wei ◽  
Zhang Fu-tang
Keyword(s):  
Signal To Noise Ratio ◽  
Gain Control ◽  
The Self ◽  
Experimental Results ◽  
Velocity Amplitude ◽  
Vibratory Gyroscope ◽  
Gyroscope System ◽  
Control Scheme ◽  
Oscillation Loop ◽  
The Stability

This paper investigates the design of a self-oscillation loop for the gyroscope system. The dynamic equations describing this system are analyzed using the method of averaging, and a criterion for selecting the circuit parameters is established based on the analysis. The validity of the criterion and the effectiveness of the control scheme are verified by the experimental results obtained from the control parameters that satisfy or violate the stability criterion. The performance of the self-oscillation loop with a z-axis gyroscope is also evaluated in light of the experimental results. The self-oscillation loop based on the auto gain control scheme effectively tracks the resonance frequency of a z-axis gyroscope. This frequency corresponds to a standard Allan variance of 0.04 Hz in 8 min at natural frequency. The output signal-to-noise ratio (SNR) is about 90 dB, and the vibratory velocity amplitude shows a deviation of 0.5% in 8 min.

Lateral Tire Forces on Wet Roads

1977 ◽  
Vol 5 (2) ◽  
pp. 75-82 ◽  
Author(s):  
A. Schallamach
Keyword(s):  
Normal Load ◽  
The Self ◽  
Experimental Results ◽  
Slip Angle ◽  
Tire Model ◽  
Side Force ◽  
Tire Forces

Abstract Expressions are derived for side force and self-aligning torque of a simple tire model on wet roads with velocity-dependent friction. The results agree qualitatively with experimental results at moderate speeds. In particular, the theory correctly predicts that the self-aligning torque can become negative under easily realizable circumstances. The slip angle at which the torque reverses sign should increase with the normal load.

Sign in / Sign up

Export Citation Format

Share Document