Masato Eguchi

Rotordynamic Forces Acting on Three-Bladed Inducer Under Supersynchronous/Synchronous Rotating Cavitation

Asymmetric cavitation, in which cavity lengths are unequal on each blade, is known as a source of cavitation induced shaft vibration in turbomachinery. To investigate the relationship of the uneven cavity length and rotordynamic force in a cavitating inducer with three blades, we conducted two experiments. In one, the growth of cavity unevenness at the inception of synchronous rotating cavitation in cryogenic flow was observed, and in the other, the rotordynamic fluid forces in water were examined by using a rotordynamic test stand with active magnetic bearings. Rotordynamic performances were obtained within a wide range of cavitation numbers, and whirl/shaft speed ratios included supersynchronous/synchronous rotating cavitation. These experimental results indicate that the shaft vibration due to the rotating cavitation is one type of self-excited vibrations arising from the coupling of cavitation instability and rotordynamics.

Comparison of Rotordynamic Fluid Forces Between Closed Impeller and Open Impeller

In the design of rocket turbopump with high energy density, rotordynamics considerations are very important to stabilize the motion of the shaft. Rotordynamic instabilities generated by rotordynamic fluid forces are often reported. It is recognized that the forces affect the whirling motion of the rotor, and induce the self-excited vibration. To understand the effect of the rotordynamic fluid forces of the impellers on rotor vibration, a tangential fluid force in a forward whirling direction and a normal fluid force in a radial direction were measured by using the experimental apparatus with an active magnetic bearing. As the experimental result for a closed impeller and an open impeller, it was clarified their fluid forces are quite different in the characteristics of destabilizing/damping effects and restoring/inertia effects.© 2012 ASME

Rotordynamic Forces Acting on Three-Bladed Inducer Under Super-Synchronous/Synchronous Rotating Cavitation

Asymmetric cavitation, in which cavity lengths are unequal on each blade, is known as a source of cavitation induced shaft vibration in turbomachinery. To investigate the relationship of the uneven cavity length and rotordynamic force in a cavitating inducer with three blades, we conducted two experiments. In one, the growth of cavity unevenness at the inception of synchronous rotating cavitation in cryogenic flow was observed, and in the other, the rotordynamic fluid forces in water were examined by using a rotordynamic test stand with active magnetic bearings. Rotordynamic performances were obtained within a wide range of cavitation numbers and whirl/shaft speed ratios included super-synchronous/synchronous rotating cavitation. These experimental results indicate that the shaft vibration due to the rotating cavitation is one type of self-excited vibrations arising from the coupling of cavitation instability and rotordynamics.Copyright