Experimental-Theoretical Comparison of Instability Onset Speeds for a Three Mass Rotor Supported by Step Journal Bearings

Abstract

Theoretically predicted instability onset speeds are compared to the experimental instability threshold speeds for a simple three mass flexible rotor supported by five geometrically different sets of step journal bearings and a set of two axial groove bearings. The near optimum step bearing designs increase the instability onset speed by around 109 percent in one case and 41 percent in another compared to two axial groove bearings. The off optimum designs increase the instability speed by 18, 30 and 35 percent. The theoretical stability analysis predicts the general trends in the experimental data.