Hirotaka Kure

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.

Robust parameter design using a supersaturated design for a response surface model

Recently, the application of response surface methodology (RSM) to robust parameter design has attracted a great deal of attention. In some cases, experiments are very expensive and may require a great deal of time to perform. Central composite designs (CCDs) and Box and Behnken designs (BBDs), which are commonly used for RSM, may lead to an unacceptably large number of experimental runs. In this paper, a supersaturated design for RSM is constructed and its application to robust parameter design is proposed. A response surface model is fitted using data from the designed experiment and a stepwise variable selection. An illustrative example is presented to show that the proposed method considerably reduces the number of experimental runs, as compared with CCDs and BBDs. Numerical experiments are also conducted in which type I and II error rates are evaluated. The results imply that the proposed method may be effective for finding the effects (i.e. main effects, two-factor interactions, and pure quadratic effects) of active factors under the ‘effect sparsity’ assumption. Copyright

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