As is well known, zero and one nodal diameter ( and ) modes of a blade system interact with the shaft system. The former couples with torsional and/or axial shaft vibrations, and the latter with bending shaft vibrations. This paper addresses the latter. With respect to modes, we discuss, from experimental and theoretical viewpoints, in-plane blades and out-of-plane blades attached radially to a rotating shaft. We found that when we excited the shaft at the rotational speed of (where is the blade natural frequency, the shaft natural frequency, and is the rotational speed), the exciting frequency induced shaft-blade coupling resonance. In addition, in the case of the in-plane blade system, we encountered an 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 due to the unbalanced shaft and the anisotropy of bearing stiffness. The other is a flow-induced, self-excited vibration caused by galloping due to the cross-sectional shape of the blade tip because this instability disappeared in the rotation test inside a vacuum chamber. The two types of abnormal vibrations occurred at the same time, and both led to the entrainment phenomenon, as identified by our own frequency analysis technique.
Vibration Diagnosis Featuring Blade-Shaft Coupling Effect of Turbine Rotor Models
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Anegawa, N., Fujiwara, H., and Matsushita, O. (October 26, 2010). "Vibration Diagnosis Featuring Blade-Shaft Coupling Effect of Turbine Rotor Models." ASME. J. Eng. Gas Turbines Power. February 2011; 133(2): 022501. https://doi.org/10.1115/1.4001980
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