| Mechanics and Fluids |
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| Effects of rarefaction on the characteristics of micro gas journal bearings |
| Hai-jun ZHANG, Chang-sheng ZHU, Ming TANG |
| College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China; College of Mechanical-Electrical Engineering, Jiaxing University, Jiaxing 314001, China |
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Abstract Given the definition of the reference Knudsen number for micro gas journal bearings, the range in the number is related to the viscosity of air at different temperatures. A modified Reynolds equation for micro gas journal bearings based on Burgdorfer’s first-order slip boundary condition is proposed that takes into account the gas rarefaction effect. The finite difference method (FDM) is adopted to solve the modified Reynolds equation to obtain the pressure profiles, load capacities and attitude angles for micro gas journal bearings at different reference Knudsen numbers, bearing numbers and journal eccentricity ratios. Numerical analysis shows that pressure profiles and non-dimensional load capacities decrease markedly as gas rarefaction increases. Attitude angles change conversely, and when the eccentricity ratio is less than 0.6, the attitude angles rise slightly and the influence of the reference Knudsen number is not marked. In addition, the effect of gas rarefaction on the non-dimensional load capacity and attitude angle decreases with smaller bearing numbers.
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Received: 10 March 2009
Published: 30 November 2009
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