粘弾性ゴムで支持された流体潤滑軸受における剛体軸ホイップの不安定性

抄録

In turbo machinery, bearing support structure with flexible O-rings can reduce the critical speed, and significantly suppress self-excited vibrations, such as whirl and whip. However, the flexibility could cause rigid rotor whip, if it has low damping. In this study, experimental data of rigid rotor whip are presented, which was obtained in an operation of water-lubricated turbo compressor. Numerical calculations were performed for two-dimensional motion equations for both the shaft and bearing, to clarify the influences of dynamic properties of bearing support. As a result, the rigid rotor whip appeared spontaneously, which agreed with the experimental data. The equations of motion were linearized and eigenvalue analysis was performed. The frequency region of rigid rotor whip was the same with Hopf bifurcation region at which the real part of an eigenvalue was positive. The influences of the frequency-dependent viscoelasticity of O-rings on the bifurcation frequencies were discussed.