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

Pettinato, Brian; Choudhury, Pranabesh De

doi:10.1080/10402009908982253

Cited by 25 publications

(7 citation statements)

References 3 publications

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“…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%

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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: Experimental Research and Frequency Dependencymentioning

confidence: 97%

Section: Experimental Research and Frequency Dependencymentioning

confidence: 98%

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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“…(11). And the moment at the fixed end can be calculated as: For higher load larger than q cr , the shim will perform as simply supported beam with a constant moment M cr at the left end.…”

Section: Compliant Shim Mechanical Modelmentioning

confidence: 99%

“…Jayaram gave an approximate solution technique considering the elastic effects on the performance [10]. Petiinato compared the bearing with key seat and spherical seat and showed that the power loss is more speed dependent rather than load dependent [11]. Wygant experimentally studied tilting the pad journal bearing with ball-socket and rockerback style pivots, and found that the friction between pivot and socket will increase the attitude angle, meanwhile increase the cross coupled stiffness [12,13].…”

Section: Introductionmentioning

confidence: 98%

Numerical study on tilting pad journal gas bearing with variable stiffness springs

et al. 2015

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Tilting pad journal gas bearing (TPJGB) with variable stiffness springs has been studied numerically. Elastic shims and displacement restriction component are introduced to realize the function of the variable stiffness springs. With different loads, the compliant component can be modeled as a cantilever beam or a combination of simply supported beam with moment at fixed end. This numerical solution couples the hydrodynamic fluid lubrication Reynolds equation with the deflections of the shims iteratively. The bearing performance with variable stiffness compliant shims has been studied with different bearing numbers. With variable stiffness compliant components, the bearing can provide mild stiffness under light load and higher stiffness under heavier load; the rotor and pad can move coherently. Therefore, the new structure possesses a wider operation range, namely high adaptability.

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“…The pad machined clearances were kept the same in the modified design, however, the preload was reduced for improved stability. This was achieved by increasing the assembled clearance by grinding the spherical seats pivots (Pettinato and De Choudhury, 1999). The tilting pad journal bearing were analyzed using frequencydependent methods (Smalley et al, 1975).…”

Section: Instability Due To Oil Sealsmentioning

confidence: 99%

Rotordynamic Stability Case Studies

Choudhury¹

2004

The International Journal of Rotating Machinery

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In this article case studies are presented involving ro-tordynamic instability of modern high-speed turbomachin-ery relating the field data to analytical methods. The studies include oil seal related field problems, instability caused by aerodynamic cross-coupling in high-pressure, high-speed compressors, and hydrodynamic bearing instability resulting in subsynchronous vibration of a high-speed turbo-charger. It has been shown that the analytical tools not only help in problem diagnostics, but also aid in problem resolution. Examples are presented showing how analytical methods , when appropriately applied, can solve rotordynamic instability and result in stable rotor system.

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

Cited by 25 publications

References 3 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

Numerical study on tilting pad journal gas bearing with variable stiffness springs

Rotordynamic Stability Case Studies

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