Dynamic Stability Research on the Double-Cylinder Turbines Marine Propulsion System With Unsymmetrical Load

Abstract

The double-cylinder turbines' (DCT) propulsion system is widely applied to large-scale ships, while the instability mechanism of the system lacks theoretical and scientific research. Based on gear transmission principle and finite width journal bearings theory, the lateral-torsional-axial model of the system considering multiple nonlinear and time-varying factors is established. The effects of the unsymmetrical load parameters on the stability of the coupled system have been explored and quantified. Results indicate that the phenomenon of instability gradually occurs with the increase of excitation frequency, the decrease of load ratio between the two inputs or the decrease of input load value, and the vibration of the gear pair on the low load side is more severe. Furthermore, the vibration amplitude is related not only to the load parameters but also to the distance between the gear pair and the load input disk. Finally, the influence of the oil whip on the system stability is crucial, especially when the system is in an unstable state. This study puts forward the stability boundary of the DCT propulsion system and provides a theoretical reference for the optimization and adjustment of the load parameters.