Experiments on the Stability and Response of a Flexible Rotor in Three Types of Journal Bearings

Abstract

Three sets of bearings were tested on a three-mass flexible rotor: axial-groove, pressure-dam and preloaded three-lobe, and the instability thresholds and unbalance responses were determined. The pressure-dam bearings were designed for maximum rigid rotor stability; the three-lobe bearings had preload factors of approximately 0.75. Rotor first and second critical speeds were observed at 2550 and 9800 rpm, respectively. The instability thresholds and unbalance responses at the first critical speed for the axial-groove and three-lobe bearings were found to be strongly dependent on the load orientation. Maximum stability limits of 6550, 7400 and 10 400 rpm were found for the axial-groove, pressure-dam, and three-lobe bearings, respectively. Thus, the preloaded three-lobe bearings were the only set that allowed this particular rotor to operate above the second critical speed. The experimental data were also compared to theoretical predictions. Differences in instability thresholds of up to 37 percent were rea...