Research on the Marine Shafting Torsional Vibration with Gears Transmission

Abstract The torsional vibration of marine propulsion shafting has been studied for more than a century. With abundant research achievements and experiences, a systematic approach of vibration calculation has been put forward for ship industrial applications. However, literature review indicates that when processing the gear transmission in the shaft line, the meshing motion has been treated as rigid mass in the equivalent equation of energy conservation, which leads to a certain error between the theoretical and experimental results of torsional vibration. Hence, to improve the calculation accuracy, a new method which considers the gear meshing stiffness is proposed in this paper. By taking the propulsion shafting of 3700DWT IMO TYPE II CHEMICAL TANKER as the research object, the forward computing formula of the shaft torsional vibration was first obtained using gear system dynamics theory. Then, the gear mesh stiffness was derived from the length variation of gear contact line. Finally, the free torsional vibration frequency was calculated considering the influence of the gear meshing force. The real marine test was implemented to verify the proposed method. The calculation results show that the new approach can track the actual torsional vibration more precisely than that without taking the gear meshing impact into account.