Rotordynamic Evaluation of a Near-Tangential-lnjection Hybrid Bearing

1999 ◽  
Vol 121 (4) ◽  
pp. 886-891 ◽  
Author(s):  
Franck Laurant ◽  
Dara W. Childs
Keyword(s):  
Rolling Element Bearings ◽  
Test Results ◽  
Margin Of Stability ◽  
Stiffness Coefficients ◽  
Rolling Element ◽  
Radial Injection ◽  
Hybrid Bearing ◽  
San Andres ◽  
Frequency Ratios ◽  
Hydrodynamic Effects

Given the inherent DN and assembly limitations of rolling-element bearings, research is underway to develop hybrid bearings (combining hydrostatic and hydrodynamic effects) for their replacement. Hybrid bearings develop cross-coupled stiffness coefficients due to fluid rotation, leading to predictions of onset speeds of instability and potential limitations in their range of application. Injecting fluid into a bearing recess against rotation, versus the customary radial injection, can reduce the circumferential flow and the cross-coupled-stiffness coefficients, and increase the margin of stability. Test results are presented here for a hybrid bearing with against-rotation injection. The bearing has a 76.4 mm diameter with LID = 1, and CrIR = 0.001. Data are presented for 55°C water at three speeds out to 25000 rpm and three pressures out to 7.0 MPa. Compared to a radial-injection hybrid bearing, experiments show injection against rotation enhances stability, yielding reductions of cross-coupled stiffness coefficients and whirl frequency ratios. However, increased flow rate and a drop of effective stiffness with increasing speed adversely affect the bearing performance. The prediction code developed by San Andres (1995) includes angled-orifice injection. The code correctly predicts trends, but at low speed, measured cross-coupled stiffness coefficients are positive, versus a prediction of larger negative values.

Rotordynamic Evaluation of a Roughened-Land Hybrid Bearing

1999 ◽  
Vol 121 (1) ◽  
pp. 133-138 ◽  
Author(s):  
Patrice Fayolle ◽  
Dara W. Childs
Keyword(s):  
High Speed ◽  
Factor Model ◽  
Attractive Alternative ◽  
Good Prediction ◽  
Ball Bearings ◽  
Stiffness Coefficients ◽  
Leakage Flow Rate ◽  
Hybrid Bearing ◽  
San Andres ◽  
Rotor Dynamic

Hybrid bearings represent an attractive alternative to ball bearings for use in highspeed cryogenic turbopumps. However, the internally-developed cross-coupled forces can generate instabilities responsible for a speed limitation of the machine. To reduce these forces and raise the onset speed of instability, the use of deliberately-roughened stators, already successfully tested for liquid “damper” seals, is investigated. Rotor-dynamic results are presented for a five-pocket orifice-compensated hole-pattern-land hybrid bearing tested with water at high speed and high pressure. Experimental data show a good prediction of leakage flow rate and direct damping but a significant improvement in stability compared to a conventional smooth-land hybrid bearing, resulting in an elevation of the onset speed of instability. Comparisons between measurements and predictions from a code developed by San Andres (1994) shows good predictions for flowrate and direct damping but an over prediction for the direct and cross-coupled stiffness coefficients by about 30 and 50 percent, respectively. The use of the Moody friction-factor model is thought to be mainly responsible for the poorer predictions of stiffness coefficients.

scholarly journals Influence of raceway waviness on the level of vibration in rolling-element bearings

2017 ◽  
Vol 65 (4) ◽  
pp. 541-551 ◽  
Author(s):  
S. Adamczak ◽  
P. Zmarzły
Keyword(s):  
Ball Bearing ◽  
Correlation Coefficients ◽  
Rolling Element Bearings ◽  
Test Results ◽  
Frequency Bandwidth ◽  
Surface Waviness ◽  
Medium Frequency ◽  
Method Of Calculation ◽  
Rolling Element ◽  
Bearing Vibration

AbstractThis paper provides a quantitative analysis of how raceway waviness (RONt) in 6304-type bearings affects their vibration. The waviness of bearing races was measured at the actual points of contact between the balls and the races. The measurements were conducted in the range of 16–50 undulations per revolution (UPR). The bearing vibration was analyzed in three bandwidths of frequency: low (LB) (50 ÷ 300 Hz), medium MB (300 ÷ 1800 Hz) and high HB (1800 ÷ 10 000 Hz), as well as in the full RMS bandwidth. The paper also presents the procedure used to determine the actual points of contact between the ball and each race to specify the point of waviness measurement. The method of calculation of the contact angle for a ball bearing is also discussed. The Pearson linear correlation coefficients were determined to analyze the relationships between the waviness parameters and the level of vibration. The test results show that an increase in the surface waviness on the inner and outer raceways causes an increase in the vibration level. The influence is most visible for the medium frequency bandwidth.

scholarly journals Experimental Assessment of Influence of the Ball Bearing Raceway Curvature Ratio on the Level of Vibration

2020 ◽  
Vol 22 (4) ◽  
pp. 103-111 ◽  
Author(s):  
Pawel Zmarzly
Keyword(s):  
Experimental Studies ◽  
Rolling Bearing ◽  
Rolling Element Bearings ◽  
Test Results ◽  
Curvature Ratio ◽  
Rolling Element ◽  
Innovative System ◽  
Bearing Raceway ◽  
Bearing Rings ◽  
Car Transportation

Raceway curvature ratio is a very important parameter, because its values influence the performance characteristics of rolling-element bearings, their durability and the level of generated vibrations. However, the level of generated vibrations is one of the most important operating parameters of the rolling-element bearings. Excessive vibrations generated by rolling-element bearings affect the operation of the whole mechanism. The article presents experimental studies aimed at evaluation of influence of the inner and outer raceway curvature ratios of 6304-type rolling-element bearings on generated vibrations values. The raceway curvature ratio was determined based on results of metrological measurements. For this purpose, the radii of the inner and outer raceways as well as the diameters of the balls were measured. Design and principle of operation of an innovative system for analysis of the raceway geometry of the rolling bearing rings was presented. The vibration analysis was carried out in three frequency ranges, i.e. low (50-300 Hz), medium (300-1,800 Hz) and high (1,800-10,000 Hz). Values of measured vibrations were expressed in Anderon units. The test results showed that increase in the raceway curvature ratio causes a moderate decrease in the value of the generated vibrations. The research results presented in this article will serve as a guidance to designers and manufacturers of the rolling-element bearings on how to modify the geometry of raceways and balls to obtain bearings that generate low vibration values. That is very important in car transportation.

Methods for Assessing the Bearing Surface Durability Performance of Lubricant Formulations

2005 ◽  
Author(s):  
Harvey P. Nixon
Keyword(s):  
Rolling Element Bearings ◽  
Test Results ◽  
Bearing Surface ◽  
Evaluation Tool ◽  
Rolling Element ◽  
Performance Effects ◽  
Surface Durability ◽  
Surface Performance ◽  
Durability Performance ◽  
Lubricant Performance

Lubricant formulations and lubricant additives have been demonstrated to have a major impact on the surface durability of rolling element bearings. However, there are very few standard tests used to assess the performance aspects of lubricants as it relates to bearing surface performance. Lubricant formulations have been slanted heavily toward protecting gear concentrated contacts from galling and wear. In addition, much of the performance differentiation of lubricants has been dependent on highly accelerated standardized laboratory tests related to gears. Methods have been developed for properly evaluating a lubricant’s performance characteristics as it relates to bearings. These methods are explained and the corresponding test results are reviewed to show their effectiveness as a lubricant performance evaluation tool. The implications of these findings provide direction and suggestions for ways to minimize or avoid potential detrimental performance effects of lubricant formulations on rolling element bearings.

Experimental Leakage and Rotordynamic Results for Helically Grooved Annular Gas Seals

1996 ◽  
Vol 118 (2) ◽  
pp. 389-393 ◽  
Author(s):  
D. W. Childs ◽  
A. J. Gansle
Keyword(s):  
Helix Angle ◽  
Progressive Increase ◽  
Test Results ◽  
Progressive Reduction ◽  
Stiffness Coefficients ◽  
Leakage Test ◽  
Gas Seals ◽  
Frequency Ratios ◽  
Rotordynamic Coefficient ◽  
Better Than

Rotordynamic-coefficient and leakage test results are presented for three grooved seals with helix angles of 0, 15, and 30 deg against rotation. The seals are 50.8 mm long and 152.4 mm in diameter. Tests were done for two supply pressures (up to 17 bars), three speeds (5000, 12,000, and 16,000 rpm), four pressure ratios, and three inlet fluid prerotation conditions. The results showed that increasing the helix angle yields a progressive reduction in the cross-coupled stiffness coefficient k and a progressive increase in leakage. The helically grooved seals consistently yield negative cross-coupled stiffness coefficients for nonprerotated inlet flow; hence, k in these seals would oppose forward whirl of a rotor. Helically grooved seals become less effective at reducing k with increasing preswirl; hence, for optimum effectiveness they should be used with a swirl brake. Comparison between helically grooved and honeycomb-stator seals showed that helically grooved stators had reduced (negative) whirl-frequency ratios for nonprerotated flows but were no better than honeycomb-stator seals for elevated fluid prerotation. The 15 and 30 deg helix grooves leaked about 1.6 and 2.2 times, respectively, as much as the honeycomb-stator seals.

Theoretical and Experimental Comparisons for Rotordynamic Coefficients of a High-Speed, High-Pressure, Orifice-Compensated Hybrid Bearing

1995 ◽  
Vol 117 (2) ◽  
pp. 285-290 ◽  
Author(s):  
Nancy M. Franchek ◽  
Dara W. Childs ◽  
Luis San Andres
Keyword(s):  
High Pressure ◽  
High Speed ◽  
Discharge Coefficient ◽  
Test Fluid ◽  
Test Results ◽  
Rotordynamic Coefficients ◽  
Hybrid Bearing ◽  
San Andres ◽  
Experimental Comparisons ◽  
Good Agreement

Comparisons are presented between measurements and predictions for a 76.2 mm diameter, high-speed (24,600 rpm), high-pressure (7.0 MPa), hybrid bearings using warm (54°C) water as a test fluid. “Hybrid” refers to combined hydrostatic and hydrodynamic action. Test results are presented for an orifice-fed, square-recess configuration with five recesses. Data are provided for rotordynamic coefficients including direct and cross-coupled stiffness, direct damping, direct added-mass coefficients, and the whirl-frequency ratio. Experimental results are compared to predictions from an analysis by San Andres (1990a), which accounts for both temporal and convective acceleration terms in the fluid film. San Andres’ development uses an orifice discharge coefficient to model the pressure drop from supply pressure to recess pressure. With experimentally determined discharge-coefficient values as input, good agreement is obtained between theory and experiment. However, predictions are sensitive to changes in the orifice discharge coefficients.

Fault Diagnosis of Bearing Based on Selective Ensemble of Multiple Fuzzy ARTMAP Neural Networks

2013 ◽  
Vol 423-426 ◽  
pp. 2480-2485 ◽  
Author(s):  
Zeng Bing Xu ◽  
Hong Wu ◽  
Tie Lin Shi
Keyword(s):  
Neural Networks ◽  
Fault Diagnosis ◽  
Classification Performance ◽  
Fuzzy Artmap ◽  
Rolling Element Bearings ◽  
Test Results ◽  
Correlation Measure ◽  
Rolling Element ◽  
Selective Ensemble

A novel selective ensemble of multiple fuzzy ARTMAP (FAM) classifiers based on the correlation measure method and Bayesian belief method is proposed to apply to the fault diagnosis of rolling element bearings in this paper. The test results show that the selective ensemble of four optimal FAM classifiers can identify the different fault categories accurately and has a better classification performance compared to the single FAM and ensemble of all FAM classifiers.

Experimental Leakage and Rotordynamic Results for Helically Grooved Annular Gas Seals

1995 ◽  
Author(s):  
Dara W. Childs ◽  
Anthony J. Gansle
Keyword(s):  
Helix Angle ◽  
Progressive Increase ◽  
Test Results ◽  
Progressive Reduction ◽  
Stiffness Coefficients ◽  
Leakage Test ◽  
Gas Seals ◽  
Frequency Ratios ◽  
Rotordynamic Coefficient ◽  
Better Than

Rotordynamic-coefficient and leakage test results are presented for three grooved seals with helix angles of 0°, 15°, and 30° against rotation. The seals are 50.8 mm long and 152.4 mm in diameter. Tests were done for two supply pressures (up to 17 bars), three speeds (5000, 12000, and 16000 rpm), four pressure ratios, and three inlet fluid prerotation conditions. The results showed that increasing the helix angle yields a progressive reduction in the cross-coupled stiffness coefficient k and a progressive increase in leakage. The helically-grooved seals consistently yield negative cross-coupled stiffness coefficients for nonprerotated inlet flow; hence, k in these seals would oppose forward whirl of a rotor. Helically grooved seals become less effective at reducing k with increasing preswirl; hence, for optimum effectiveness they should be used with a swirl brake. Comparison between helically-grooved and honeycomb-stator seals showed that helically-grooved stators had reduced (negative) whirl-frequency ratios for nonprerotated flows but were no better than honeycomb-stator seals for elevated fluid prerotation. The 15° and 30° helix grooves leaked about 1.6 and 2.2 times, respectively, as much as the honeycomb-stator seals.

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