Characteristics of propulsion shafting system in ships with engine acceleration problems in the barred speed range

Abstract As part of recent efforts to reduce emissions and get significant fuel savings with ships, ultra-long stroke engines, (hereafter G-type engines), are now commonly used in eco-ships. The best feature of G-type engines is their ability to generate greater power at lower speeds than previous designs to get higher propulsion efficiency. In some recent cases, however, operators of eco-ships have experienced problems related to being unable to pass quickly enough through their critical speed within the overall range of operating speeds. In this study, the characteristics of the torsional vibration in a propulsion shafting system equipped with a fuel saving ultra-long stroke engine were reviewed. This review included the technology developed for improvement of the acceleration capacity in low load ranges in eco-ships. Then a proper examination was conducted of methods for alternative design of propulsion shafting systems to cope with the engine acceleration problem in the barred speed range.