Evaluation of the Thermal Effects in Tilting Pad Bearing

Daniel, Gregory B.; Cavalca, Kátia Lucchesi

doi:10.1155/2013/725268

Cited by 25 publications

(39 citation statements)

References 17 publications

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“…The mentioned program was used to determine the oil film pressure distribution over a pad of the upper journal bearing of Itaipu hydrogenerators, with a clearance of 280 m and with an average viscosity of 0.047 Pas, the same values existing in a pad where the oil film pressure was measured [10]. The estimation of the oil film temperature and viscosity considered the results obtained by Daniel and Cavalca [29]. This bearing has 16 pads with length = 0.35 m, width = 0.40 m, / = 0.40, and radius = 1.103 m. The tangential velocity of shaft surface is = 10.6 m/s, considering a 60 Hz hydrogenerator at nominal speed (92.3 r/min).…”

Section: Model Validationmentioning

confidence: 99%

Using Simplified Models to Assist Fault Detection and Diagnosis in Large Hydrogenerators

Brito

Machado

Neto

2017

International Journal of Rotating Machinery

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Based on experimental evidence collected in a set of twenty 700 MW hydrogenerators, this article shows that the operating conditions of large hydrogenerators journal bearings may have unpredictable and significant changes, without apparent reasons. These changes prevent the accurate determination of bearing dynamic coefficients and make the prediction of these machines dynamic behavior unfeasible, even using refined models. This makes it difficult to differentiate the normal changes in hydrogenerators dynamics from the changes created by a fault event. To overcome such difficulty, this article proposes a back-to-basics step, the using of simplified mathematical models to assist hydrogenerators vibration monitoring and exemplifies this proposal by modeling a 700 MW hydrogenerator. A first model estimates the influence of changes in bearing operating conditions in the bearing stiffnesses, considering only the hydrodynamic effects of an isoviscous oil film with linear thickness distribution. A second model simulates hydrogenerators dynamics using only 10 degrees of freedom, giving the monitored vibrations as outputs, under normal operating conditions or in the presence of a fault. This article shows that simplified models may give satisfactory results when bearing operating conditions are properly determined, results comparable to those obtained by more refined models or by measurements in the modeled hydrogenerator.

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Section: Model Validationmentioning

confidence: 99%

Using Simplified Models to Assist Fault Detection and Diagnosis in Large Hydrogenerators

Brito

Machado

Neto

2017

International Journal of Rotating Machinery

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“…This sudden increase in the natural frequencies implies a substantial and abrupt change in the bearings stiffness, what can be explained by sudden changes in the shaft eccentricity, like the one shown in Figure 7. [19,20]), modifying the dynamic behavior of the rotating machine. This section describes some phenomena observed in LHG journal bearings.…”

Section: Sudden Changes On Natural Frequenciesmentioning

confidence: 99%

Experimental Aspects in the Vibration-Based Condition Monitoring of Large Hydrogenerators

Brito

Machado

Neto

et al. 2017

International Journal of Rotating Machinery

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Based on experimental observations on a set of twenty 700 MW hydrogenerators, compiled from several technical reports issued over the last three decades and collected from the reprocessing of the vibration signals recorded during the last commissioning tests, this paper shows that the accurate determination of the journal bearings operating conditions may be a difficult task. It shows that the outsize bearing brackets of large hydrogenerators are subject to substantial dimensional changes caused by external agents, like the generator electromagnetic field and the bearing cooling water temperature. It also shows that the shaft eccentricity of a journal bearing of a healthy large hydrogenerator, operating in steady-state condition, may experience unpredictable, sudden, and significant changes without apparent reasons. Some of these phenomena are reproduced in ordinary commissioning tests or may be noticed even during normal operation, while others are rarely observed or are only detected through special tests. These phenomena modify journal bearings stiffness and damping, changing the hydrogenerator dynamics, creating discrepancies between theoretical predictions and experimental measurements, and making damage detection and diagnostics difficult. Therefore, these phenomena must be analyzed and considered in the application of vibration-based condition monitoring to these rotating machines.

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“…Thermo-hydrodynamic (THD) and more recently thermo-elasto-hydrodynamic (TEHD) analyses are usually used for the prediction of pad metal temperature. Daniel and Cavalca in [5] investigated the thermal effects of tilting-pad bearings by using THD analysis and a finite-volume method for the integration of the energy equation. Thorat et al in [6] compared pad temperature measurements with predictions using a TEHD model by investigating the effects of manufacturing tolerances on bearing assembled clearance and preload.…”

Section: Introductionmentioning

confidence: 99%

Cooled Pads for Tilting-Pad Journal Bearings

et al. 2019

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Tilting-pad journal bearings (TPJBs) are widely installed in rotating machines owing to their high stability, but some drawbacks can be noted, such as higher cost with respect to cylindrical journal bearings and thermal issues. High temperatures in the pads correspond to low oil-film thicknesses and large thermal deformations in the pads. Therefore, the restriction of the maximum temperature of the bearing is a key aspect for oil-film bearings. The temperature reduction is generally obtained by adopting higher oil inlet flowrates or suitable oil nozzles. In this paper, the idea of using cooled pads with internal channels in which an external cooling fluid is circulated will be applied to a TPJB for the first time. The three-dimensional TEHD model of the TPJB, equipped with a cooled pad, will be introduced, and the results of the numerical simulations will be discussed. Several analyses have been performed in order to investigate the influence of cooling conditions, such as the type, flowrate, inlet temperature and number of cooled pads. Two types of pad geometry with different cross-sections of the cooling circuit, namely, circular and six-square multi-channel sections, have been compared to the reference bearing with solid pads. Simple experimental tests were performed by means of a test rig equipped with a cooled pad bearing obtained with the additive manufacturing process, thus showing the effectiveness of the solution and the agreement with the predictions.

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Evaluation of the Thermal Effects in Tilting Pad Bearing

Cited by 25 publications

References 17 publications

Using Simplified Models to Assist Fault Detection and Diagnosis in Large Hydrogenerators

Using Simplified Models to Assist Fault Detection and Diagnosis in Large Hydrogenerators

Experimental Aspects in the Vibration-Based Condition Monitoring of Large Hydrogenerators

Cooled Pads for Tilting-Pad Journal Bearings

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