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Research Papers

Theoretical and Experimental Analyses of Directly Lubricated Tilting-Pad Journal Bearings With Leading Edge Groove

[+] Author and Article Information
Thomas Hagemann

Mem. ASME
Institute of Tribology and
Energy Conversion Machinery,
Clausthal University of Technology,
Leibnizstr. 32,
Clausthal-Zellerfeld 38678, Germany
e-mail: hagemann@itr.tu-clausthal.de

Hubert Schwarze

Mem. ASME
Institute of Tribology and
Energy Conversion Machinery,
Clausthal University of Technology,
Leibnizstr. 32,
Clausthal-Zellerfeld 38678, Germany
e-mail: schwarze@itr.tu-clausthal.de

1Corresponding author.

Manuscript received June 26, 2018; final manuscript received July 11, 2018; published online December 12, 2018. Editor: Jerzy T. Sawicki.

J. Eng. Gas Turbines Power 141(5), 051010 (Dec 12, 2018) (10 pages) Paper No: GTP-18-1354; doi: 10.1115/1.4041026 History: Received June 26, 2018; Revised July 11, 2018

Flooded lubrication of tilting-pad journal bearings provides safe and robust operation for many applications due to a completely filled gap at the leading edge of each pad. Direct lubrication by leading edge grooves (LEG) located on the pads represents an alternative to restrictive end seals to ensure these conditions at the entrance to the convergent lubricant film. A theoretical model is presented that describes the specific influences of LEG design on operating characteristics. First, in contrast to conventional tilting-pad journal bearing designs, the LEG is a self-contained lube oil pocket, which is generally connected to an outer annular oil supply channel. Consequently, each LEG can feature a specific speed and load-dependent effective pocket pressure, which influences the pad tilting angle. Second, the thermal inlet mixing model must consider the specific flow conditions depending on the main flow direction within the film as well as the one between outer annular channel and pocket. The novel LEG model is integrated into a comprehensive bearing code and validated with test from a high performance test rig for a four tilting-pad bearing in load between pivot orientations. Within the investigated operating range good agreement between theoretical and experimental data is achieved if all boundary conditions are accurately considered. Additionally, the impact of single simplifications within the model is studied and evaluated. Finally, the test data are compared to results from the same test bearing with modified lubricant oil supply conditions in order to identify specific properties of LEG design.

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References

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Figures

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Fig. 1

Inlet mixing energy balance

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Fig. 2

Punctuation is not used if the caption is a single sentence

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Fig. 4

Simplified model partition

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Fig. 5

Flow rates in the pocket area

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Fig. 6

Numerical grid and boundary conditions

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Fig. 7

Flow boundary conditions for positive main flow direction (y = 0)

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Fig. 8

General view on the test unit of the test rig

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Fig. 9

Drawing of the investigated tilting-pad journal bearing

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Fig. 10

Investigated tilting-pad journal bearing

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Fig. 11

Absolute fluid velocity within pocket 3 at n = 12,000 rpm

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Fig. 12

Heat transfer coefficients and boundary conditions

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Fig. 13

Measured film pressure (pq = 2.0 MPa, Q = 40 l/min, Tsup = 50 °C, z = 36 mm)

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Fig. 14

Predicted film pressure (pq = 2.0 MPa, Q = 40 l/min, Tsup = 50 °C, z = 36 mm)

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Fig. 15

Predicted film pressure on pad no. 3 (n = 12,000 rpm, pq = 2.0 MPa, Q = 40 l/min, Tsup = 50 °C, z = 36 mm)

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Fig. 16

Measured pad temperature (pq = 2.0 MPa, Q = 40 l/min, Tsup = 50 °C, z = 36 mm)

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Fig. 17

Predicted pad temperature (pq = 2.0 MPa, Q = 40 l/min, Tsup = 50 °C, z = 36 mm)

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Fig. 18

Measured and predicted maximum pad sensor temperature (pq = 2.0 MPa, Tsup = 50 °C)

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Fig. 19

Measured and predicted pad temperature (n = 12,000 rpm, pq = 2.0 MPa, Q = 40 l/min, Tsup = 50 °C, z = 36 mm)

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Fig. 20

Measured and predicted power loss (pq = 2.0 MPa, Tsup = 50 °C)

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Fig. 21

Measured and predicted pad temperature (n = 12,000 rpm, pq = 2.0 MPa, Q = 40 l/min, Tsup = 50 °C, z = 36 mm)

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Fig. 22

Measured and predicted maximum pad sensor temperature (pq = 2.0 MPa, Q = 40 l/min, Tsup = 50 °C)

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Fig. 23

Measured and predicted power loss (pq = 2.0 MPa, Q = 40 l/min, Tsup = 50 °C)

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Fig. 24

Measured pad temperature for spray-bar (S-bar) and LEG lubrication (n = 12,000 rpm, Q = 30 l/min, Tsup = 50 °C, z = 36 mm)

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Fig. 25

Measured power loss for spray-bar (S-bar) and direct LEG lubrication (n = 12,000 rpm, Q = 30 l/min, Tsup = 50 °C)

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Fig. 26

Predicted pad tilting-angles (pq = 2.0 MPa, Tsup = 50 °C)

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