Vibration analysis on Power Take Off generators in hybrid ship propulsion system

Abstract

The hybrid propulsion in vessels comprises mechanical and electrical propulsion in the kinematic drivetrain. Hence, propulsion efficiency is optimised and responding to a variable power demand quickly and flexibly both in mechanical power delivered by diesel engines and/or electric power through variable speed electric motors. This combination leads to an extensive operating flexibility, making it possible to precisely provide the power and torque in all of the vessel’s operating modes with different operating modes. At present, there are few works in literature about the research on the vibration of the hybrid propulsion system in new ship propulsion plant. Based on experimental measurements, the paper aims to present a framework of vibration measurement, data processing, analyses and evaluation for the vibration of Power Take Off (PTO) generators in one operating mode of such hybrid propulsion system during vessels’ sea trials. A case study for a vessel is described in detail to verify the procedure. The frequency analyses are made in the range of 2 to 100 Hz and compared to relevant DNV - GL (Det Norske Veritas - Germanischer Lloyd) criteria and also ISO 10816-3 for assessing the acceptability of the vibration levels during the sea trials. The results from this study also provide a reliable procedure for testing and evaluating the vibration of shaft generators founded in any hybrid propulsion shafting.