Research Papers: Hydrodynamic Lubrication

Measurement and Prediction of the Journal Circumferential Temperature Distribution for the Rotordynamic Morton Effect

[+] Author and Article Information
Xiaomeng Tong

Department of Mechanical Engineering,
Texas A&M University,
College Station, TX 77840
e-mail: tongxiaomeng1989@tamu.edu

Alan Palazzolo

James J. Cain Professor
Fellow ASME
Department of Mechanical Engineering,
Texas A&M University,
College Station, TX 77840
e-mail: a-palazzolo@tamu.edu

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received May 6, 2017; final manuscript received September 27, 2017; published online October 23, 2017. Assoc. Editor: Mihai Arghir.

J. Tribol 140(3), 031702 (Oct 23, 2017) (13 pages) Paper No: TRIB-17-1176; doi: 10.1115/1.4038104 History: Received May 06, 2017; Revised September 27, 2017

The journal is the part of a shaft that is inside a fluid film bearing and is usually assumed to be circumferentially isothermal. Recent work has shown that under certain vibration conditions, a significant temperature difference (ΔT) can develop around the journal circumference. The ΔT may cause the shaft to bend leading to a synchronous vibration instability problem, termed the “Morton effect” (ME). A test rig was developed to verify the asymmetric journal temperature of the ME and its prediction using a five-pad tilting pad journal bearing (TPJB) operating with an eccentric shaft to replicate a circular vibration orbit. The bearing is tested at various conditions including: supply oil temperature at 28 °C and 41 °C, bearing operating eccentricities of zero and 32%Cb, and rotor speed up to 5500 rpm. The journal temperature distribution is recorded with 20 sensors located around the journal circumference, and the measurements provide a benchmark for predictions from a time transient model with the three-dimensional (3D) fluid and solid finite element method (FEM), and with a simplified ME prediction approach using only steady-state results. The test results follow the predictions exhibiting a sinusoidal-like temperature profile around the circumference with an angular lag of the hot spot location behind the high spot location (angular position on the rotor that arrives at the minimum film thickness condition each rotation) by a speed-dependent angle. Increasing the supply oil temperature reduced the journal ΔT, while increasing the bearing operating eccentricity increased the journal ΔT. The agreement between the test and predicted results is significantly better for the 3D FEM transient model than for the steady-state-based model in terms of journal ΔT and hot spot position. An improved version of the latter approach is proposed and yields significantly better correlation with the test measurements.

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Fig. 1

Photo and diagram showing the key components of the TPJB-ME test rig

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Fig. 2

(a) Shaft with eccentric journal and 20 internally routed RTDs and (b) TPJB test bearing

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Fig. 3

Key components of the TPJB-ME test rig hydraulic system

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Fig. 4

Cross-sectional view for both static eccentricities, e1=0 and e2=0.32Cb

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Fig. 5

Measured rotor temperature with lower (cool) supply oil temperature and two static eccentricities: (a) maximum rotor temperature and peak–peak temperature difference, (b) rotor temperature profiles at approximately 1 krpm, (c) 3.75 krpm, and (d) 5 krpm

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Fig. 6

(a) Linear interpolation to estimate hot spot location and (b) measured phase lag between the high spot and hot spot with cool supply oil and two eccentricities

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Fig. 7

Measured rotor temperature with hot supply oil and two eccentricities: (a) maximum journal temperature and peak–peak temperature difference, (b) phase lag between high spot and hot spot, (c) steady rotor temperature profile around 1 krpm, (d) 3.75 krpm, and (e) 5 krpm

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Fig. 8

(a) Ratio between hot and cool oil testing and (b) oil viscosity profile versus different temperature

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Fig. 9

Boundary conditions for the Reynolds and Energy equations solution [14]

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Fig. 10

Journal and rigid pad force diagram

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Fig. 11

Boundary conditions for the coupled journal/shaft/film/pad thermal model

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Fig. 12

Experimental and predicted journal temperature comparison for cool and hot oil cases: (a) maximum temperature, (b) peak–peak temperature difference, and (c) phase lag between high and hot spot

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Fig. 13

Parametric studies of bearing clearance and mixing coefficient by predicting (a) maximum journal temperature, (b) peak–peak temperature difference on journal circumference, and (c) phase lag between high and hot spot

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Fig. 14

Predictions of journal temperature difference by the high-fidelity and simplified analysis (a) cold oil supply, eccentricity e = 0, (b) cold oil supply, e = 0.32Cb, (c) hot oil supply, e = 0, and (d) hot oil supply, e = 0.32Cb

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Fig. 15

Journal center whirling along an orbit with velocity v

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Fig. 16

Predicted TPJB journal ΔT for the simplified and high fidelity methods with reduced clearance: (a) eccentricity = 0 and (b) eccentricity = 0.17Cb




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