タービンモデルロータの翼軸連成効果に着目した振動診断(機械力学,計測,自動制御)

概要

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It is well known that zero and one nodal diameter (k=0 and k=1) modes of blade system interact with shaft system. The former is coupling with torsional and/or axial shaft vibrations and the latter with bending shaft vibrations. This paper deals with the latter. With respect to k=1 modes, we discuss experimentally and theoretically in-plane blades and out-of-plane blades attached radially to rotating shaft. If we excited the shaft at the rotational speed of Ω=|ω_b-ω_s| (where ω_b=blade natural frequency, ω_s=shaft natural frequency and Ω=rotational speed), we examined that the exciting frequency v=ω_s induced shaft-blade coupling resonance. In addition, in the case of the in-plane blade system we encountered the additional resonance attributed to deformation caused by gravity. In the case of the out-of-plane blade system, we experienced two types of abnormal vibrations. One is the additional resonance generated at Ω=ω_b/2 due to unbalance of the shaft and anisotropy of the bearing stiffness. The other is a flow-induced self-exited vibration caused by galloping due to the cross-section shape of blade tip, because this instability disappeared at rotation test inside a vacuum chamber. Both occurred at the same time and both leads to the entrainment phenomenon, which was identified by our own frequency analysis technique.
2010-04-25