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Research Papers: Hydrodynamic Lubrication

Steady Characteristics of High-Speed Micro-Gas Journal Bearings With Different Gaseous Lubricants and Extreme Temperature Difference

[+] Author and Article Information
Xueqing Zhang

Key Laboratory of Low-Grade Energy
Utilization Technologists and
Systems of Ministry of Education,
College of Power Engineering,
Chongqing University,
Chongqing 40030, China
e-mail: xueqingzhang@cqu.edu.cn

Qinghua Chen

Mem. ASME
Key Laboratory of Low-Grade Energy
Utilization Technologists and
Systems of Ministry of Education,
College of Power Engineering,
Chongqing University,
Chongqing 40030, China
e-mail: qhchen@cqu.edu.cn

Juanfang Liu

Key Laboratory of Low-Grade Energy
Utilization Technologists and
Systems of Ministry of Education,
College of Power Engineering,
Chongqing University,
Chongqing 40030, China
e-mail: juanfang@cqu.edu.cn

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received November 21, 2015; final manuscript received April 19, 2016; published online August 11, 2016. Assoc. Editor: Bugra Ertas.

J. Tribol 139(2), 021703 (Aug 11, 2016) (7 pages) Paper No: TRIB-15-1420; doi: 10.1115/1.4033565 History: Received November 21, 2015; Revised April 19, 2016

High-speed micro-gas journal bearing is one of the essential components of micro-gas turbines. As for the operating conditions of bearings, the high-speed, high-temperature, ultra-high temperature difference along the axial direction and the species of gaseous lubricants are extremely essential to be taken into account, and the effects of these factors are examined in this paper. The first-order modified Reynolds equation including the thermal creep, which results from the extremely large temperature gradient along the axial direction, is first derived and coupled with the simplified energy equation to investigate the steady hydrodynamic characteristics of the micro-gas bearings. Under the isothermal condition, it is found that CO2 can not only improve the stability of bearings but also generate a relatively higher load capacity by some comparisons. Thus, CO2 is chosen as the lubricant to further explore the influence of thermal creep. As the rotation speed and eccentricity ratio change, the thermal creep hardly has any effect on the gas film pressure. However, the shorter bearing length can augment the thermal creep. Compared with the cases without the thermal creep, the thermal creep could remarkably destroy the stability of gas bearing, but it might slightly enhance the load capacity.

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References

Figures

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Fig. 1

Variation in the dynamic viscosity with the gas film temperature for the different gaseous lubricants

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Fig. 2

Variation in the reference Knudsen number with the gas film temperature for the different gaseous lubricants

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Fig. 3

Schematic of the gas journal bearings (a) and three-dimensional coordinates of the gas film (b)

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Fig. 4

Variation of the load capacity with the rotation speed for the different gaseous lubricants

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Fig. 5

Variation of the attitude angle with the rotation speed for the different gaseous lubricants

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Fig. 6

Profiles of the gas film pressure at the different temperatures: (a)  y=0 and (b) θ=π

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Fig. 7

Comparison of the film pressure profiles at the different rotation speeds (a), eccentricity ratios (b), and bearing lengths (c)

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Fig. 8

Variations in the load capacity and the attitude angle with (a) the rotation speed, (b) the eccentricity ratio, and (c) the bearing length

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