Abstract

Propulsion systems powered by double-cylinder turbines (DCT) are widely used in large-scale ships. However, the nonlinear instability leads to hidden dangers associated with the safe operation, and there is a lack of theoretical and systematic research on this problem. Based on the gear transmission principle and non-Newtonian thermal elastohydrodynamic lubrication (EHL) theory, a torsional model of a two-stage herringbone system forced by unsymmetrical load is established.

The nonlinear and time-varying factors of meshing friction, meshing stiffness, and gear pair backlash are included in the model, and multiple meshing states, including single- and double-sided impact are studied. New nonlinear phenomena of the dynamic system are explored and the effects of the unsymmetrical load on the system stability are quantified.

The results indicate that the stability of the gear system is improved, and that the back-sided impact gradually disappears with the increases of load ratio between the two inputs and the input load value. Furthermore, it is found that the gear pairs on the low-load side experience more severe vibration than those on the high-load side. Finally, the stability of the gear pairs decreases along the power transmission path of the multi-stage gear system. The results of this research will be useful when making predictions of the stability of such systems and in the optimization of the load parameters.