Abstract: This paper presents a new dynamic model of the shaft system of a hydropower generator coupled with external random excitation from its foundation. We establish nonlinear dynamic differential equations for the shaft system, considering the nonlinear effects of rotor unbalance and runner sealing force; numerically simulate the influences of nondeterministic and random foundation excitations on the shaft’s transverse vibrations, using axis orbit diagrams, Poincaré maps and bifurcation diagrams, etc. The results show that the shaft system’s operational stability will be affected by variations in the frequency, intensity and spectrum width of the excitation, leading to its complicated nonlinear vibration behaviors such as period-doubling and chaotic motions. This study helps a deeper understanding of the influence and mechanism of the nonlinear dynamics of hydropower generator shaft systems.

Key words: hydraulic machinery, hydropower generator shaft system, foundation excitation, nonlinear vibration, random excitation