Experimental Investigation of Gas Bearings with Ultra-Thin Films.
COLUMBIA UNIV NEW YORK LUBRICATION RESEARCH LAB
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The experimental investigation described here involves the highly accurate measurement of bearing clearances on the order of 10 microinches in self-acting pivoted narrow-slider gas bearings. The experimental measurements are based on light interferometry using a variable-wavelength pulsed dye laser and a CW HeNe laser as monochromatic sources. The light interference in the gas bearing is obtained by flying the slider on a very precise optically flat quartz disk through which the light beam is transmitted. The combined effect of high Knudsen numbers and surface irregularities on the flying height of narrow gas bearings is observed by varying the load on the bearing and the ambient molecular mean free path. The experimentally measured bearing clearances are compared quantitatively with rather accurate theoretical predictions obtained by numerical solution of Reynolds differential equation for compressible fluids with slip boundary conditions. The result of this study indicates that, as clearances in narrow gas bearings get progressively smaller, while the Knudsen number increases to values beyond 0.1, the theoretical model fails to predict the bearing behavior. It is also argued that this failure is because of the weakness of the continuum model. Author
- Machinery and Tools