ON THE TRANSLATORY WHIRL MOTION OF A VERTICAL ROTOR IN PLAIN CYLINDRICAL GAS-DYNAMIC JOURNAL BEARINGS
GENERAL ELECTRIC CO SCHENECTADY N Y
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The determination of the bearing fluid film forces in a rotor system under dynamical conditions is discussed. In the case of a vertical rotor operating in a gaseous medium in plain cylindrical journal bearings, the steady whirl approximation is appropriate. In the steady whirl approximation, a set of rotating coordinates is employed, and the time dependence of the Reynolds equation is eliminated. At the same time, the compressibility number, Lambda, is replaced by the quantity 1-2 alphaomega multiplied by lambda. This approximation applies when both whirl acceleration and the radial velocity of the shaft are small. The attitude angle of the fluid film force is strongly dependent on the whirl motion. Experimental data of synchronous whirl agrees with the theoretical calculations based on the steady whirl analysis. A perfectly balanced vertical rotor in a plain gas dynamic journal bearing is always unstable with respect to the half frequency whirl.