Abstract
It is well known that zero and one nodal diameter (k=0 and k=1) modes of blade system interact with shaft system. We discus experimentally and theoretically the k=1 modes of blade system. If we excited the shaft at the rotational speed of Ω=|ω_b-ω_s|, we examined that the exciting frequency ν=ω_s induced shaft-blade coupled resonance. In addition, we encountered the abnormal vibration below. In the case of the in-plane blade system, blades resonate at Ω=ω_b attributed to deformation caused by gravity. In the case of the out-of-plane blade system, blades are generated at Ω=ω_b/2 due to unbalance of the shaft and asymmetry of the bearing stiffness, and a nonlinear self-exited vibration occurred by galloping due to the cross-section shape of blade tip. Both occurred at the same time and the entrainment phenomena were identified. This paper also includes experimental data of 45deg. blade system.
