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Research Papers: Gas Turbines: Structures and Dynamics

Modeling and Analysis of Micro Hybrid Gas Spiral-Grooved Thrust Bearing for Microengine

[+] Author and Article Information
Xiao-Qing Zhang

e-mail: xiaogear@bit.edu.cn

Xiao-Li Wang

e-mail: xiaoli_wang@bit.edu.cn

Ren Liu

e-mail: 29318868@qq.com

Yu-Yan Zhang

e-mail: hangyuyan@bit.edu.cn

School of Mechanical Engineering,
Beijing Institute of Technology,
Beijing 100081, China

Contributed by the Structures and Dynamics Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received June 25, 2013; final manuscript received July 31, 2013; published online September 23, 2013. Editor: David Wisler.

J. Eng. Gas Turbines Power 135(12), 122508 (Sep 23, 2013) (8 pages) Paper No: GTP-13-1180; doi: 10.1115/1.4025239 History: Received June 25, 2013; Revised July 31, 2013

The micro hybrid spiral-grooved thrust bearing is a promising candidate to support the rotating elements in power MEMS devices such as micro gas turbine engines. However, the realization of hybrid thrust bearings has encountered a number of technical challenges due to the very high rotating speed and DN number (the product of the inner diameter and the rotational speed of the bearing, mm · rpm) to achieve high power density, the super thin gas film between rotors and thrust pad, and the relative large fabrication uncertainties according to the imperfection of the fabrication technology. In this paper, the configuration of a micro hybrid spiral-grooved thrust bearing for power MEMS is designed, and the steady and dynamic characteristics of this kind of bearing are then analyzed comprehensively, with the consideration of both the rarefaction effects and the influence of potential microfabrication defects. The nonlinear equations of molecular gas-film lubrication describing the gas rarefaction effects in a micro hybrid bearing are discretized by the finite volume method and solved by the Newton–Raphson techniques. The small perturbation technique is employed to study the dynamic behavior of a micro hybrid bearing. The results show that the micro hybrid thrust bearing exhibits better steady-state and dynamic performance than the existing micro hydrodynamic and hydrostatic bearings and that the hybrid bearings are likelier to be stable than their hydrodynamic counterparts, especially when the frequency number is high. The load capacity of the micro hybrid bearing increases slightly with the number of orifices and gradually with the diameter ratio of the orifice. The microfabrication defects of clogged orifices could lessen the load capacity and the dynamic coefficients of the hybrid thrust bearing. The model developed in this paper can serve as a useful tool to provide insight into micro hybrid gas thrust bearing-rotor systems.

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Figures

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Fig. 1

Schematic of the microengine with hybrid thrust bearing

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Fig. 2

Schematic drawing of the hybrid thrust bearing pad

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Fig. 3

Comparison of numerical load capacity with experimental results

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Fig. 4

Dynamic coefficients versus frequency number at Λ = 100: (a) stiffness and (b) damping

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Fig. 5

Comparison of numerical load capacity among three types of thrust bearing

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Fig. 6

Schematic drawing of different configurations and the corresponding pressure distribution

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Fig. 7

Comparison of nondimensional load capacity among different cases

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Fig. 8

Nondimensional load capacity versus orifice number at different supply pressure

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Fig. 9

Nondimensional load capacity versus diameter ratio at different supply pressure

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Fig. 10

Nondimensional load capacity for bearings with clogged orifices at σ = 10, Ps = 4.0

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Fig. 11

Dynamic coefficients for bearings with clogged orifices at Λ = 100, σ = 100, Ps = 4.0: (a) stiffness coefficients; (b) damping coefficients

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