Lateral-torsional coupled vibration of a propulsion shaft with a diesel engine supported by a resilient mount

Lateral-torsional coupled vibration destabilizes a rotating system. The instability region of the rotating system is the speed range where the frequencies of the lateral and torsional modes intersect. In this study, the abnormally increased vibration of the typical diesel engine-reduction gear propulsion system for a naval vessel was examined in relation to the lateral-torsional coupled vibration under the assumption that it can be approximated by the Jeffcott rotor with three degrees of freedom. Through numerical and experimental investigation, a protection method was developed to avoid the unstable region of the diesel engine-reduction gear propulsion system.