Rotordynamic data are presented for a rocker-pivot tilting pad bearing in load-on-pad (LOP) configuration for (345–3101 kPa) unit loads and speeds from 4000 rpm to 13,000 rpm. The bearing was directly lubricated through a leading edge groove with five pads, 0.282 preload, 60% offset, 57.87 deg pad arc angle, 101.587 mm (3.9995 in.) rotor diameter, 0.1575 mm (0.0062 in.) diametral clearance, and 60.325 mm (2.375 in.) pad length. Measured results were reported for this bearing by Carter and Childs (2008, “Measurements Versus Predictions for the Rotordynamic Characteristics of a 5-Pad, Rocker-Pivot, Tilting-Pad Bearing in Load Between Pad Configuration,” ASME Paper No. GT2008-50069) in the load-between-pad (LBP) configuration. Results for the LOP are compared with predictions from a bulk-flow Navier–Stokes model (as utilized by San Andres (1991, “Effect of Eccentricity on the Force Response of a Hybrid Bearing,” STLE Tribol. Trans., 34, pp. 537–544)) and to the prior LBP results. Frequency effects on the dynamic-stiffness coefficients were investigated by applying dynamic-force excitation over a range of excitation frequencies. Generally, the direct real parts of the dynamic-stiffness coefficients could be modeled as quadratic functions of the excitation frequency, and accounted for by adding a mass matrix to the conventional model to produce a frequency-independent model. Measured added-mass terms in the loaded direction approached 60 kg. The static load direction in the tests was . The direct stiffness coefficients and depend strongly on the applied unit load, more so than speed. They generally increased linearly with load, shifting to a quadratic dependence at higher unit loads. At lower unit loads, and increase monotonically with running speed. The experimental results were compared with predictions from a bulk-flow computational fluid dynamics analysis. Stiffness orthotropy was apparent in test results, significantly more than predicted, and it became more pronounced at the heavier unit loads. Measured values were consistently higher than predicted, and measured values were lower. Comparing the LOP results to prior measured LBP results for the same bearing, at higher loads, is significantly larger for the LOP configuration than LBP. Measured values for are about the same for LOP and LBP. At low unit loads, stiffness orthotropy defined as is the same for LOP and LBP, progressively increasing with increasing unit loads. At the highest unit load, for LOP and 1.7 for LBP. Measured direct damping coefficients and were insensitive to changes in either load or speed, in contrast to predictions of marked sensitivity for changes in the load. Only at the highest test speed of 13,000 rpm were the direct damping coefficients adequately predicted. No frequency dependency was observed for the direct damping coefficients.
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August 2011
Research Papers
Rotordynamic Characteristics of a Five Pad, Rocker-Pivot, Tilting Pad Bearing in a Load-on-Pad Configuration; Comparisons to Predictions and Load-Between-Pad Results
Dara W. Childs,
Dara W. Childs
The Leland T. Jordan Professor of Mechanical Engineering
Turbomachinery Laboratory,
e-mail: dchilds@tamu.edu
Texas A&M University
, College Station, TX 77843-3123
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Clint R. Carter
Clint R. Carter
Graduate Research Assistant
Turbomachinery Laboratory,
e-mail: crcarter@dow.com
Texas A&M University
, College Station, TX 77843-3123
Search for other works by this author on:
Dara W. Childs
The Leland T. Jordan Professor of Mechanical Engineering
Turbomachinery Laboratory,
Texas A&M University
, College Station, TX 77843-3123e-mail: dchilds@tamu.edu
Clint R. Carter
Graduate Research Assistant
Turbomachinery Laboratory,
Texas A&M University
, College Station, TX 77843-3123e-mail: crcarter@dow.com
J. Eng. Gas Turbines Power. Aug 2011, 133(8): 082503 (11 pages)
Published Online: April 6, 2011
Article history
Received:
August 5, 2009
Revised:
August 21, 2009
Online:
April 6, 2011
Published:
April 6, 2011
Citation
Childs, D. W., and Carter, C. R. (April 6, 2011). "Rotordynamic Characteristics of a Five Pad, Rocker-Pivot, Tilting Pad Bearing in a Load-on-Pad Configuration; Comparisons to Predictions and Load-Between-Pad Results." ASME. J. Eng. Gas Turbines Power. August 2011; 133(8): 082503. https://doi.org/10.1115/1.4000893
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