A propulsion shafting system in a naval vessel consists of twin propeller shafts mainly according to the requirement of high power, high speed and various operating modes.
Destroyer is intended for multi-purpose naval vessel. Destroyer’s propulsion system consists generally of two controllable pitch propellers(twin screws) powered by a combined gas turbine and gas turbine(COGAG) propulsion system.
Two gas turbines are connected at the reduction gear assembly by a independent driving shaft. Each gas turbine set, gear drive and shaft line are mechanically not restrained each other.
Therefore, the system includes the branched shafting and such a branched shafting system has very intricate vibrating characteristics.
In this study, to evaluate vibrational characteristics of the propulsion shafting system some analytical methods are studied and vibrational equations are derived. And then, torsional natural frequencies and mode shapes of the system are analyzed.
The analysis, including natural frequencies and mode shapes, for 12 cases of the system is conducted using ANSYS code with an equivalent mass-elastic model.