Experimental Investigation into the Instability of an Over-Hung Rigid Centrifuge Rotor Partially Filled With Fluid

The objective of this paper is to experimentally investigate the instability of an over-hung rigid centrifuge rotor partially filled with fluid. Specific emphasis has been placed on the developing process of rotor instability, the dynamical behavior of the rotor system while the instability occurs, and the frequency and direction of rotor whirl within the unstable region of rotational speeds. The effects of fluid-fill ratio on the rotor whirl frequency, the extent of the unstable region of rotational speeds, and the rotor imbalance are also studied. The detailed results clarify some issues and show some new phenomena on the instability of a rotor partially filled with fluid. The phenomena include: sub-synchronous frequency that does not result in instability of the rotor system and disappears in the unstable region at the larger fluid-fill ratios; different whirl frequencies entering the unstable region for slowly increasing and decreasing rotational speed operations; variable whirl frequency within the unstable region; hysteresis at the upper bound of the unstable region; and a break-down of the fluid free-surface.