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Abstract: Considering the boundary conditions due to the slip effect, the modified Reynolds equation is applied to investigate the dynamical lubrication characteristics of the gas bearing of micro-rotor system in micro-electro-mechanical systems (MEMS), the real pressure distribution in the interior of the bearing, the load carrying capacity and the attitude angle are obtained by using numerical calculation method. The characteristics of micro-lubricated gas journal bearings compared with those obtained from macro infinite short bearing indicate that the slip effect has great impact on the dynamical lubrication characteristics of gas bearing. The macro infinite short bearing model and the bearing model without slip effect will overestimate the load carrying capacity of the gas bearing, particularly in the range of high eccentricity e (e >0.6), i.e., the discrepancy will be larger. When the micro-rotor system runs at high-speed or super high-speed, the pressure and load carrying capacity of the gas bearing can be improved.
Key words: Micro-electro-mechanical systems (MEMS) Gas bearing Slip effect
CLC No:
TH117.2 TH133
国家杰出青年基金 (10325209)、国家自然科学基金(10602033,
50575132)和中国博士后基金(20060400165)资助项目. Received 20070513
,
received
in
revised
form
20080103
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| References
[1] BART S F,
MEHREGANY M, TAVROW L S, et al. Electric micromotor dynamics[J]. IEEE
Transactions on Electron Devices, 1992, 39(3): 566-575.
[2] EPSTEIN A H. Millimeter-scale, MEMS gas turbine engines[C]//Proc. of
ASME Turbo Expo 2003 Power for Land, Sea and Air, June 16-19, 2003,
Atlanta, Georgia, USA, 2003: 1-28.
[3] LIU Ying, WEN Shizhu. Study on performances of micro-friction and
its control in MEMS[J]. Chinese Journal of Mechanical Engineering,
2002, 38(3): 1-5.
[4] ZHANG Wenming, MENG Guang. Progress of wear properties on
micro-electro-mechanical systems[J]. Tribology, 2005, 25(5): 489-494.
[5] ZHANG Wenming, MENG Guang. Numerical simulation of sliding wear
between the rotor bushing and ground plane in micromotors[J]. Sensors
and Actuators A: Physical, 2006, 126: 15-24.
[6] ZHANG Wenming, MENG Guang. Study on wear characteristics of super
high-speed micro-rotor systems [J]. Tribology, 2006, 26(2): 155-158.
[7] ZHANG Wenming. Study on the dynamic characteristics of micro-rotor
system [D]. Shanghai: Shanghai Jiaotong University, 2006.
[8] FUKUI S, KANEKO R. Estimation of gas film lubrication effects
beneath sliding bushings of micromotors using a molecular gas film
lubrication equation[J]. Wear, 1993, 168: 175-179.
[9] KIM D, LEE S, BRYANT M D, et al. Hydrodynamic performance of gas
micromotors[J]. Journal of Tribology, 2004, 126: 711-718.
[10] WONG C W, ZHANG X, JACOBSON S A, et al. A self-acting thrust
bearing for high speed micro-rotors[C]//The Fifteenth IEEE International
conference on Micro Eleltro Mechanical Systems, January 20-24, 2002, Las
Vegas, NV, USA, 2002: 276-279.
[11] SAVOULIDES N, BREUER K S, JACOBSON S, et al. Low-order models for
very short hybrid gas bearings[J]. Journal of Tribology, 2001,
123: 368-375.
[12] WU L, BOGY D B. New first and second order slip models for the
compressible Reynolds equation[J]. Journal of Tribology, 2003,
125: 558-561.
[13] SUN Y, CHAN W K, LIU N. A slip model with molecular dynamics[J]. J.
Micromech. Microeng., 2002, 12: 316-322.
[14] GAD-EL-HAK M. The fluid mechanics of microdevices- the Freeman
scholar lecture[J]. Journal of Fluids Engineering, 1999, 121: 5-33.
[15] LEE Y B, KWAK H D, KIM C H, et al. Numerical prediction of slip
flow effect on gas-lubricated journal bearings for MEMS/MST-based
micro-rotating machinery[J]. Tribology International, 2005, 38: 89-96.
[16] BURGDORFER A. The influence of the molecular mean free path on the
performance of hydrodynamic gas lubricated bearing[J]. ASME Journal of
Basic Engineering, 1959, 81(1): 94-100.
[17] HSIA Y T, DOMOTO G A. An experimental investigation of molecular
rarefaction effects in gas lubricated bearings at ultra-low clearances[J].
Journal of Tribology, 1983, 81: 94-100.
[18] MITSUYA Y. Modified Reynolds equation for ultra-thin film gas
lubrication using 1.5-order slip-flow model and considering surface
accommodation coefficient[J]. Journal of Tribology, 1993, 115: 289-294.
[19] FUKUI S, KANEKO R. Analysis of ultral-thin gas film lubrication
based on linearized Boltzmann equation: first report-derivation of a
generalized lubrication including thermal creep flow[J]. Journal of
Tribology, 1988, 110: 253-262.
[20] HARMROCK B J. Fundamentals of fluid film lubrication [M].
McGraw-Hill Series in Mechanical Engineering, New York: McGraw-Hill,
1994.
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