Test Results of Key and Spherical Pivot Five-Shoe Tilt Pad Journal Bearings—Part II: Dynamic Measurements

Pettinato, Brian; Choudhury, Pranabesh De

doi:10.1080/10402009908982269

Cited by 16 publications

(12 citation statements)

References 5 publications

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“…Branagan and Barrett [37] account for reductions in bearing clearance by calculating the thermal expansion of the pad using the difference between the pad at room temperature and at operating conditions (using the mean of pad temperatures at the surface and back of the pad), the pad's thermal expansion coefficient, and the thickness of the pad at the pivot. For the bearing investigated, employing this method results in a clearance reduction coefficient of (30) which accounts for only one-half the change in clearance noted in the current work.…”

Section: Resultsmentioning

confidence: 88%

“…Other notable experimental papers include those by Pettinato and De Choudhury [29,30] in 1999, who presented comparisons between theory and experiment for five-pad cylindrical-seat and spherical-seat sliding-pivot bearings having similar pivot stiffnesses. Theoretical predictions were generated using an isoviscous Reynolds equation model and Lund's pad assembly method with rigid pads and pivots.…”

Section: Experimental Research and Frequency Dependencymentioning

confidence: 97%

“…Note that statements by researchers in 1995 [11], in 1999 [29,30], and in 2006 [28,31,32,34] regarding good agreement between measurements and predictions do not specify whether cold-bearing or hot-bearing (operating) clearances were used to predict bearing coefficients. Since hot-bearing clearances were not stated, it is likely that cold-bearing clearances were used for predictions.…”

Section: Experimental Research and Frequency Dependencymentioning

confidence: 98%

See 2 more Smart Citations

Tilting Pad Journal Bearings—A Discussion on Stability Calculation, Frequency Dependence, and Pad and Pivot

Wilkes

Childs

2012

Journal of Engineering for Gas Turbines and Power

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For several years, researchers have presented predictions showing that using a full tilting-pad journal bearing (TPJB) model (retaining all of the pad degrees of freedom) is necessary to accurately perform stability calculations for a shaft operating on TPJBs. This paper will discuss this issue, discuss the importance of pad and pivot flexibility in predicting impedance coefficients for the tilting-pad journal bearing, present measured changes in bearing clearance with operating temperature, and summarize the differences between measured and predicted frequency dependence of dynamic impedance coefficients. The current work presents recent test data for a 100 mm (4 in.) five-pad TPJB tested in load on pad (LOP) configuration. Measured results include bearing clearance as a function of operating temperature, pad clearance and radial displacement of the loaded pad (the pad having the static load vector directed through its pivot), and frequency-dependent stiffness and damping. Measured hot-bearing clearances are approximately 30% smaller than measured cold-bearing clearances and are inversely proportional to pad surface temperature; predicting bearing impedances with a rigid pad and pivot model using these reduced clearances results in overpredicted stiffness and damping coefficients that are several times larger than previous comparisons. The effect of employing a full bearing model versus a reduced bearing model (where only journal degrees of freedom are retained) in a stability calculation for a realistic rotor-bearing system is assessed. For the bearing tested, the bearing coefficients reduced at the frequency of the unstable eigenvalue (subsynchronously reduced) predicted a destabilizing cross-coupled stiffness coefficient at the onset of instability within 1% of the full model, while synchronously reduced coefficients for the lightly loaded bearing required 25% more destabilizing cross-coupled stiffness than the full model to cause system instability. The same stability calculation was performed using measured stiffness and damping coefficients at synchronous and subsynchronous frequencies. These predictions showed that both the synchronously measured stiffness and damping and predictions using the full bearing model were more conservative than the model using subsynchronously measured stiffness and damping, an outcome that is completely opposite from conclusions reached by comparing different prediction models. This contrasting outcome results from a predicted increase in damping with increasing excitation frequency at all speeds and loads; however, this increase in damping with increasing excitation fi-equency was only measured at the most heavily loaded conditions.

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Section: Resultsmentioning

confidence: 88%

Section: Experimental Research and Frequency Dependencymentioning

confidence: 97%

Section: Experimental Research and Frequency Dependencymentioning

confidence: 98%

See 1 more Smart Citation

Tilting Pad Journal Bearings—A Discussion on Stability Calculation, Frequency Dependence, and Pad and Pivot

Wilkes

Childs

2012

Journal of Engineering for Gas Turbines and Power

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“…Pettinato and Choudhury [116] identified bearing coefficients for tilting-pad bearings with unbalance excitation. Incremental loading was used to identify bearing stiffness.…”

Section: Known/additional Unbalance Excitation and Vibration Monitoringmentioning

confidence: 99%

A Review on Application of Dynamic Parameters of Journal Bearing for Vibration and Condition Monitoring

Babu

Raj²,

Lakshmanan

2015

J. mech.

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The journal bearings are used to support high-speed rotors in turbo machinery which often operate above the rotor first bending critical speed. This bearing provide both lateral support and dynamic coefficients: Stiffness, damping, and mass terms, related to machine vibrations. The various methods of identifying journal bearing dynamic characteristics, from measured data, obtained from different measurement systems, are reviewed. The various approaches to the bearing identification problem are discussed. The various data processing methods in the time and frequency domains are presented. Also, vibration and condition monitoring techniques are presented. In this review, the relative strengths and weaknesses of bearing are presented and developments and trends in improving bearing measurements are documented. Future trends of journal bearing are discussed.

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“…(frequency) Mass, damping, stiffness and uncertainty Li et al (1999) GDS Impact Displ. (frequency) Damping and stiffness Pettinato and Choudhury (1999) HDJ in the geometry and consequently in the analysis and experimental rig fabrication along with their general representation in mathematical modeling among the all other classes of the bearings. Lund (1980Lund ( , 1987 reviewed the concept of dynamic coefficients for fluid-film journal bearings.…”

Section: Referencesmentioning

confidence: 99%

Identification of Dynamic Bearing Parameters: A Review

Tiwari¹,

Lees²,

Friswell³

2004

shock vib digest

132

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In this paper, we present a review of the experimental identification of dynamic parameters of bearings in a rotating machine. Major emphasis is given to vibration-based identification methods and the review encompasses descriptions of experimental measurement techniques, mathematical modeling, parameter extraction algorithms and uncertainty in the estimates applied to a variety of bearings. The parameter extraction algorithms include the descriptions of governing equations of the rotor-bearing system and identification methods in both time and frequency domains. The identification techniques have been classified based on methods used to excite the system. The review includes a variety of bearings and similar components, which play an active link between the rotating and stationary parts of a machine. Based on the state of the art in bearing identification, conclusions are made and future directions are suggested.

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Test Results of Key and Spherical Pivot Five-Shoe Tilt Pad Journal Bearings—Part II: Dynamic Measurements

Cited by 16 publications

References 5 publications

Tilting Pad Journal Bearings—A Discussion on Stability Calculation, Frequency Dependence, and Pad and Pivot

Tilting Pad Journal Bearings—A Discussion on Stability Calculation, Frequency Dependence, and Pad and Pivot

A Review on Application of Dynamic Parameters of Journal Bearing for Vibration and Condition Monitoring

Identification of Dynamic Bearing Parameters: A Review

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