Resonance and Instability of Blade-Shaft Coupled Bending Vibrations with In-plane Blade Vibration

Abstract As a major component of a power plant, a turbine generator must have sufficient reliability. Longer blades have lower natural frequency, thereby requiring that the design of the shaft and blade takes into account the coupling of the blade vibration mode, nodal diameter k =0 and k =1 with vibration of the shaft. The present work analyzes the coupling of the translation motion of the shaft with in-plane vibration of the blades with k =1 modes. At a rotational speed Ω 1 =|ω s −ω b |, the resonance of the blades has a relatively large amplitude. A violent coupled resonance was observed at a rotational speed Ω 2 =ω s +ω b . Resonance in blade vibration at Ω 1 =|ω s −ω b | was experimentally confirmed. Keywords : Blade-Shaft coupled vibration, Bending vibration, Resonance, Instability, In-plane vibration, Turbine generator 1. Introduction As a major component of the power plant, a turbine generator must have sufficient reliability. The rotary shaft system is usually designed to give a low Q-factor and avoid resonance based on the rotor-dynamic analysis of the bending and torsional vibration of the shaft-bearing system, in which the blades are assumed to be a rigid disk. Meanwhile, the blade is designed to avoid resonance under the rated operation conditions based on analysis of a single blade under ideal conditions where the shaft is assumed to be fixed [1],[2]. The long blades used in turbine generators for nuclear power plants have low natural frequencies, thereby necessitating a design that takes into consideration blade-shaft coupled vibration. General conditions for coupling of blade and shaft vibrations are shown in Table 1. Blade