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Research Papers: Gas Turbines: Structures and Dynamics

Improving Tilting Pad Journal Bearing Predictions—Part I: Model Development and Impact of Rotor Excited Versus Bearing Excited Impedance Coefficients

[+] Author and Article Information
Jason C. Wilkes

Research Engineer
Southwest Research Institute,
San Antonio, TX 78238
e-mail: jason.wilkes@swri.org

Dara W. Childs

Leland T. Jordan Prof. of
Mechanical Engineering,
Turbomachinery Laboratory,
Texas A&M University,
College Station, TX 77802
e-mail: dchilds@tamu.edu

Contributed by International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 2, 2012; final manuscript received July 5, 2012; published online December 4, 2012. Editor: Dilip R. Ballal.

J. Eng. Gas Turbines Power 135(1), 012502 (Dec 04, 2012) (14 pages) Paper No: GTP-12-1249; doi: 10.1115/1.4007367 History: Received July 02, 2012; Revised July 05, 2012

The floating-bearing-test-rig concept was initially developed by Glienicke in 1966 and has since been used to test many tilting-pad journal bearings (TPJBs). The impedances measured during these tests have been compared to rotor/journal-perturbed impedance predictions. Since the inertial acceleration of a pad is different for bearing-perturbed and rotor-perturbed motions, the bearing's reaction force components for bearing-perturbed and journal-perturbed motions will also differ. An understanding of how bearing-perturbed and rotor-perturbed impedances differ is needed to assess the validity of past, present, and future comparisons between TPJB test data and predictions. A new TPJB perturbation model is developed including the effects of angular, radial, and transverse pad motion and changes in pad clearance due to pad bending compliance. Though all of these pad variables have previously been included in different analyses, there are no publications containing perturbations of all four variables. In addition, previous researchers have only perturbed the rotor, while both the bearing and rotor motions are perturbed in the present analysis. The applicability of comparing rotor-perturbed bearing impedance predictions to impedances measured on a bearing-perturbed test rig is assessed by comparing rotor-perturbed and bearing-perturbed impedance predictions for an example bearing.

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References

Figures

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Fig. 1

Schematic of the journal, bearing, and kth pad in the reference state

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Fig. 2

Rigid body degrees of freedom for a tilting pad

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Fig. 3

Pivot reaction forces

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Fig. 4

Pressure distribution on a tilting pad

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Fig. 5

Change in pad curvature resulting from applied end moments

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Fig. 6

Illustration of a pad with a pivot insert

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Fig. 7

Schematic of the journal, bearing, and kth pad in a general position

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Fig. 8

Schematic of the dynamic forces acting on the kth pad in a TPJB

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Fig. 10

(a) Real and (b) imaginary impedances for bearing A with 10× heavier pads predicted relative to perturbations of the journal (jj) and bearing (bb) at 10,000 rpm and 1200 kPa unit load

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Fig. 9

(a) Real and (b) imaginary impedances for bearing A predicted relative to perturbations of the journal (jj) and bearing (bb) at 10,000 rpm and 1200 kPa unit load

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Fig. 11

(a) Real and (b) imaginary bearing impedances predicted relative to perturbations of the journal (jj) and journal-bearing (jb) at 4400 rpm and 1200 kPa (454 psi) unit load

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Fig. 12

(a) Real and (b) imaginary impedances for bearing B predicted relative to perturbations of the journal (jj) and bearing (bb) at 3000 rpm and 1200 kPa unit load

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Fig. 13

(a) Real and (b) imaginary impedances for bearing B predicted relative to perturbations of the journal (jj) and bearing (bb) at 3000 rpm and 300 kPa unit load

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