Abstract:

The whirling behaviour of an over\|hung rotor partially filled with fluid in the unstable region is investigated experimentally. Specific attention is paid to the developing process of the rotor instability, the whirling frequency and direction within the unstable region, the fluid free surface characteristics and the dynamical behaviour of the rotor system while the instability occurs. The effects of the fluid fill ratio on the whirling frequency and the unstable region are also studied. The results clarify many issues and show many new phenomena about the instability of the rotor partially filled with fluid for the first time. These new phenomena include the subsynchronous frequency occurring before the instability which does not result in the instability of the rotor system and disappears in the unstable speed region at large fluid fill ratios, different whirling frequencies existing in the unstable region between the slowing increasing and decreasing speed operation, the breaking\|down phenomenon of the fluid free surface and the chaotic motion.

Key words: rotordynamics, instability, rotating fluid, fluid\, solid interaction, rotor