The Influence of Oil Supply Pressure on the Behavior of a Rigid Symmetrical Balanced Rotor in Journal Bearings With Circumferential Feeding

1992 ◽  
Vol 114 (4) ◽  
pp. 812-817 ◽  
Author(s):  
G. Capone ◽  
M. Russo ◽  
R. Russo
Keyword(s):  
Experimental Investigation ◽  
Journal Bearings ◽  
Experimental Results ◽  
Specific Load ◽  
Static Characteristics ◽  
Supply Pressure ◽  
Film Instability ◽  
Low Load ◽  
Theoretical Predictions ◽  
Load Conditions

A theoretical-experimental investigation was carried out on the behavior of a rigid symmetrical balanced rotor in short, cylindrical, circumferentially fed journal bearings under low load conditions. The influence of supply pressure on bearing static characteristics and oil film instability threshold was evaluated for the above system. The experimental results are shown along with the theoretical predictions of the static characteristics and limit stability curves for different values of the ratio between supply pressure and specific load.

Analysis of the Hydraulic Jacking of Journal Bearings

1971 ◽  
Vol 13 (3) ◽  
pp. 123-129 ◽  
Author(s):  
J. H. Horlock
Keyword(s):  
Flow Rate ◽  
Journal Bearings ◽  
Experimental Results ◽  
Supply Pressure ◽  
Hydraulic Jacking

An analysis is given for the flow in the clearance space between a shaft and its bearing, when the shaft is touching the bearing at its lowest point. Solutions are given for short and long bearings. The predictions of the analysis are compared with published experimental results. While the supply pressure required to lift a shaft off its bearing may be predicted accurately, the estimated flow rate is far less than that measured in experiments.

Report Paper 2: Approximate Short Bearing Analysis and Experimental Results Obtained Using Plastic Bearing Liners

1969 ◽  
Vol 184 (12) ◽  
pp. 190-196 ◽  
Author(s):  
J. P. O'Donoghue ◽  
P. R. Koch ◽  
C. J. Hooke
Keyword(s):  
Approximate Solution ◽  
Film Thickness ◽  
Journal Bearings ◽  
Experimental Results ◽  
Approximate Theory ◽  
Hydrodynamic Problem ◽  
Dynamic Conditions ◽  
Oil Film ◽  
Theoretical Predictions ◽  
Bearing Analysis

This paper outlines a new approximate theory for liquid lubricated plain journal bearings with elastic liners. This is a modified form of Ocvirk's theory and includes the effect of circumferential flow. The results of a series of tests on short plastic bearings are presented to compare with the theoretical predictions of the new theory. The authors conclude that for short bearings the theory gives reasonably good predictions of performance, but the elasticity assumptions cause major errors for length/diameter ratios greater than 0·5 due to the decrease in oil film thickness that occurs near the ends of the bearing. The approximate solution adopted for the hydrodynamic problem may be of use for considering dynamic conditions taking the Reynolds conditions for cavitation.

A Comparison of Experimental Results and Theoretical Predictions for the Rotordynamic Coefficients of Short (L/D = 1/6) Labyrinth Seals

1991 ◽  
Author(s):  
Joseph M. Pelletti ◽  
Dara W. Childs
Keyword(s):  
Flow Model ◽  
Control Volume ◽  
Pressure Ratio ◽  
Experimental Results ◽  
Rotor Speed ◽  
Labyrinth Seals ◽  
Rotordynamic Coefficients ◽  
Supply Pressure ◽  
Test Conditions ◽  
Theoretical Predictions

Abstract Experimental results for the rotordynamic coefficients of short (L/D = 1/6) teeth-on-stator and teeth-on-rotor labyrinth seals are presented. The effects that pressure ratio (fluid density), rotor speed, fluid pre-swirl and seal clearance have on these coefficients are studied. Tests were run out to speeds of 16000 rpm with a supply pressure of 17.3 bar and seal clearances ranging from 0.229–0.419 mm. The experimental results are compared with theoretical predictions of a two control volume compressible flow model. The experimental results show that decreases in pressure ratio and increases in rotor speed are stabilizing while increases in fluid pre-swirl and seal clearance are destabilizing for both seal configurations. The theoretical model correctly predicts the effects of pressure ratio, rotor speed and fluid pre-swirl on the cross-coupled stiffness. It also predicts reasonable values for direct damping for all test conditions. However, the theory incorrectly predicts the effect of seal clearance on these coefficients. Consequently the theoretical predictions are much better for the large clearance seals.

Dynamic Film Pressure Measurements in Journal Bearings for Use in Rotor Balancing

1976 ◽  
Vol 98 (1) ◽  
pp. 92-100 ◽  
Author(s):  
E. Christensen ◽  
J. Tonnesen ◽  
J. W. Lund
Keyword(s):  
Experimental Investigation ◽  
Measurement Accuracy ◽  
Journal Bearing ◽  
Linear Analysis ◽  
Journal Bearings ◽  
Experimental Measurements ◽  
Pressure Measurements ◽  
Pressure Transducers ◽  
Theoretical Predictions ◽  
Rotor Balancing

The paper presents the results of an experimental investigation where membrane transducers in the journal bearing wall are used to measure the dynamic oil-film pressures caused by rotor unbalance whirl. The results are applied successfully to balancing the rotor, and the experimental measurements of amplitude and pressure response are found to agree well with theoretical predictions, based on a linear analysis. The measurement accuracy of the pressure transducers compare favorably with the accuracy obtained with shaft displacement probes.

scholarly journals Rotor Instability Induced by Radial Clearance in Ball Bearing Supports

1993 ◽  
Author(s):  
Yao-Qun Lin
Keyword(s):  
Experimental Investigation ◽  
Internal Friction ◽  
Natural Frequency ◽  
Computer Simulations ◽  
Ball Bearing ◽  
Rotor Dynamics ◽  
Experimental Results ◽  
Radial Clearance ◽  
Speed Range ◽  
Theoretical Predictions

In rotor dynamics, the rotor nonsynchronous natural frequency vibration, or rotor instability, has been mainly ascribed to two mechanisms, i.e., internal friction effects and fluid actions. It is shown, however, in this paper that the radial clearance in ball bearing supports can also induce rotor instability through an internal-impacts mechanism. The behavior of the rotor with radial clearance in its ball bearing supports is simulated numerically. The computer simulations show that there is a speed range in which the rotor will vibrate at both the synchronous frequency and the natural frequency. Below or above this speed range, the rotor has only the synchronous response and its harmonics. An experimental investigation was conducted to verify this analysis. The experimental results agree well with the theoretical predictions.

A Theoretical and Experimental Investigation of a Gas Operated Bearing Damper for Turbomachinery: Part II — Experimental Results and Comparison With Theory

1993 ◽  
Author(s):  
Padmanabhan Sundararajan ◽  
John M. Vance
Keyword(s):  
Experimental Investigation ◽  
High Temperature ◽  
Theoretical Model ◽  
Natural Frequency ◽  
Experimental Results ◽  
Experimental Measurements ◽  
Vibration Damper ◽  
Theoretical Predictions ◽  
Present Design ◽  
Gas Damper

Abstract This is the second of two papers describing results of a research project directed at developing a gas operated vibration damper for high temperature turbomachinery applications. This part presents the experimental measurements made on three variations of the gas damper hardware and compares them with the theoretical predictions presented in Part I. It is found that the isentropic theoretical model predicts the damper characteristics quite well. A maximum damping of 13.2 Ib-s/in was measured for a single actuator at a natural frequency of 100 hz using the present design and the results suggest that significantly higher damping levels are possible with design modifications.

Experimental Rotor Unbalance Response Using Hydrostatic Gas Lubrication

1973 ◽  
Vol 95 (4) ◽  
pp. 469-476 ◽  
Author(s):  
R. D. Dayton ◽  
M. R. Chasman
Keyword(s):  
Theoretical Model ◽  
Reasonable Agreement ◽  
Journal Bearings ◽  
Rotor Speed ◽  
Supply Pressure ◽  
Unbalance Response ◽  
Gas Lubrication ◽  
Theoretical Predictions ◽  
Theoretical Results

This paper investigates the adequacy of the theoretical model in predicting the unbalance response of a rotor supported in hydrostatic gas-lubricated journal bearings. The magnitude of experimental whirl amplitudes induced by applying various unbalances to a rotor supported in hydrostatic journal bearings were measured and compared to the theoretical predictions. Variables investigated were rotor unbalance, rotor speed, and bearing supply pressure. Reasonable agreement between the experimental and theoretical results was obtained.

Experimental Investigation of Static Characteristics on Eddy Current Sensor for External Cylindrical Grinding Measurement System

2011 ◽  
Vol 460-461 ◽  
pp. 3-8 ◽  
Author(s):  
Yi Cao ◽  
Hong Ge Sun ◽  
Yi Zang ◽  
Xiu Juan Li
Keyword(s):  
Experimental Investigation ◽  
Eddy Current ◽  
Measurement System ◽  
Experimental Results ◽  
Current Sensor ◽  
Static Characteristics ◽  
Cylindrical Grinding ◽  
Eddy Current Sensor ◽  
External Cylindrical Grinding

In order to investigate the static characteristics of eddy current sensor (ECS) influenced by cylindrical diameter, material and displacement of the target workpiece, some experiments were carried out. Firstly, the theoretical principles of ECS were recalled for explaining the related parameters. The experiment setup was then introduced and some features including linearity, resolution and sensitivity were tested by the experimental instrument and calibrated. Finally, the experimental results were obtained and the influence elements were discussed in the paper.

On the Influence of the Supply Pressure on the Dynamic Stability of Hybrid Gas Journal Wave Bearings

2005 ◽  
Author(s):  
Florin Dimofte ◽  
Sorin Cioc ◽  
Robert F. Handschuh ◽  
David P. Fleming
Keyword(s):  
Hydrodynamic Instability ◽  
General Rule ◽  
Journal Bearings ◽  
Clearance Ratio ◽  
Stability Threshold ◽  
Supply Pressure ◽  
Bearing Clearance ◽  
Whirling Motion ◽  
Film Instability ◽  
The Stability

Gas journal bearings are very sensitive to the hydrodynamic instability known as subsynchronous whirl motion, especially when they are unloaded. The wave bearing concept can improve the bearing stability, meaning that the wave bearing can run stably up to higher speeds than the plain bearing. In addition, when whirling motion occurs due to the fluid film instability, the orbit of this motion can be contained within the bearing clearance. Another step ahead for improving bearing stability is to pressurize the bearing. Tests were conducted to verify the threshold of subsynchronous whirl motion of bearings with a 35 mm diameter and 30 mm length. Pressurized air is admitted to the bearings through inherent compensated holes located in two planes along the bearing length. Various numbers of holes and diameters were used. The tests were conducted at speeds up to 30,000 rpm and the supply pressure was varied from zero to 0.14 MPa. The pressure was measured within a 2% precision. Two values for the wave amplitude to bearing clearance ratio were used. Pressurizing the bearing with 0.14 MPa can make the bearing run stably up to a speed of 20,000 rpm, unlike an unpressurized bearing that can experience subsynchronous motion at speeds less than 1,000 rpm. It was found that the supply pressure has a strong stabilizing effect. As a general rule, a 10% change of the value of the supply pressure can modify the stability threshold speed with more than 1000 rpm.

Journal Bearing Lubrication and Design

1948 ◽  
Vol 158 (1) ◽  
pp. 250-254
Author(s):  
A. S. T. Thomson
Keyword(s):  
Experimental Investigation ◽  
Applied Load ◽  
Journal Bearing ◽  
Point Contact ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Experimental Results ◽  
Radial Clearance ◽  
Series Of Experiments ◽  
Loaded Side

The paper summarizes the results of an experimental investigation on the effects of variation in bearing width and radial clearance on the operating conditions of centrally loaded clearance journal bearings, the bearing arc being kept constant at 120 deg. The investigation, which was carried out prior to 1940, is complementary to an earlier paper by the author in which the effects of variations in bearing width and arc of embrace were investigated. The experimental results are compared with theoretical values modified by the relevant leakage coefficients. The measure of agreement obtained indicates that theoretical values so modified may be used with confidence in design. A short series of experiments is described; in these, high-point contact at starting and stopping is eliminated by supplying oil to a groove in the loaded side of the bearing at a pressure sufficiently great to overcome the applied load. The effect of a groove on the loaded side of the brass under various conditions of lubrication is investigated.

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