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Research Papers: Hydrodynamic Lubrication

A Model for Oil Flow and Fluid Temperature Inlet Mixing in Hydrodynamic Journal Bearings

[+] 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.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received May 17, 2018; final manuscript received August 4, 2018; published online October 11, 2018. Assoc. Editor: Joichi Sugimura.

J. Tribol 141(2), 021701 (Oct 11, 2018) (14 pages) Paper No: TRIB-18-1190; doi: 10.1115/1.4041211 History: Received May 17, 2018; Revised August 04, 2018

The quality of predictions for the operating behavior of high-speed journal bearings strongly depends on realistic boundary conditions within the inlet region supplying a mixture of hot oil from the upstream pad and fresh lubricant from the inlet device to the downstream located pad. Therefore, an appropriate modeling of fundamental phenomena within the inlet region is essential for a reliable simulation of fluid and heat flow in the entire bearing. A theoretical model including hydraulic, mechanical, and energetic effects and the procedure of its numerical implementation in typical bearing codes for thermo-hydrodynamic lubrication is described and validated. Convective and conductive heat transfer as well as dissipation due to internal friction in the lubricant is considered for the space between pads or the pocket where the inlet is located. In contrast to most other models, the region between the physical inlet and the lubricant film is part of the solution domain and not only represented by boundary conditions. The model provides flow rate and temperature boundary conditions for extended Reynolds equation and a three-dimensional (3D) energy equation of film and inlet region, respectively. The impact of backflow from the inlet region to the outer supply channel possibly occurring in sealed pockets is taken into account. Moreover, the model considers the influence of turbulent flow in the inlet region.

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References

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Figures

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Fig. 3

Directed lubrication (left) and flooded lubrication (right)

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Fig. 2

Bleed notch in the pocket of a fixed-pad journal bearing

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Fig. 1

Perturbing elements in groove mixing according to Ref.[1]

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Fig. 5

Pressure drop at the axial interface between the pocket and land according to Ref. [26]

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Fig. 4

Flow rates in the pocket area [20]

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Fig. 6

Flow profile in inlet and leading edge pad region [6]

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Fig. 7

Geometry of pocket region with bleed notches

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Fig. 8

Geometrical matching coefficient for triangular cross section (laminar flow) [28]

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Fig. 9

Geometrical matching coefficient for triangular cross section (turbulent flow) [28]

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Fig. 10

Boundary layer in the inlet region at laminar and turbulent flow according to Ref. [8]

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Fig. 11

Four-lobe bearing with outer annular supply channel

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Fig. 12

Extended control stream channel model of Vohr [9] according to Ref. [8] for unpressurized inlet pockets

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Fig. 13

Modified control stream channel for pressurized inlet pockets

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Fig. 14

Transformation of the hot oil layer to the leading edge flow in the pocket

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Fig. 15

Modified control stream channel for backflow into the outer annular channel

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Fig. 16

Determination of flow field and pressure distribution for a certain journal position

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Fig. 17

Temperature and heat flow boundary conditions for fixed-pad bearings

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Fig. 18

Temperature and heat flow boundary conditions for conventionally lubricated tilting-pad bearings

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Fig. 19

Temperature and heat flow boundary conditions for tilting-pad bearings with LEG

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Fig. 20

Two-lobe fixed-pad bearing (TLB) according to Ref. [3]

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Fig. 21

Measured [3] and predicted bearing metal temperatures for medium rotor speeds (TLB, z = 250 mm, p¯= 2.0 MPa, Tsup = 45 °C)

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Fig. 22

Measured [3] and predicted bearing metal temperatures for high rotor speeds (TLB, z = 250 mm, p¯= 2.0 MPa, Tsup = 45 °C)

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Fig. 23

Measured [3] and predicted leading edge bearing metal temperatures and pocket temperatures according to Eq. (26) (TLB, z = 250 mm, p¯ 2.0 MPa, Tsup = 45 °C)

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Fig. 24

Predicted heat flow on reservoir in pocket (left) and share of pocket oil flow rate (right) (TLB, p¯= 2.0 MPa, Tsup = 45 °C)

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Fig. 27

Measured [3] and predicted frictional power loss (TLB, p¯ 0.0 MPa, Tsup = 45 °C)

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Fig. 28

Predicted flow regime distribution in the pad (left) and inlet (right) region (TLB, p¯= 0.0 MPa, Tsup = 45 °C)

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Fig. 25

Measured [3] and predicted film pressure (TLB, z = 250 mm, n = 3000 rpm, Tsup = 45 °C)

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Fig. 26

Measured [3] and predicted film thickness (TLB, z = 250 mm, n = 3000 rpm, Tsup = 45 °C)

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