Acceleration Performance Improvement for Gas Turbine/Waterjet Propelled Vessels.

Abstract: The paper presents a criterion for the acceleration performance improvement of vessels whose propulsion system consists of a gas turbine/waterjet combination. The criterion is developed and tested by means of computer simulation, through a complex mathematical model applied here to a fast trimaran ferry. The model consists of several modules, describing the dynamic performance of the different elements of the propulsion system (i.e.: gas turbine, waterjet, hull resistance, telegraph, engine governor, etc.). So, linking together the modules, the dynamic simulation model of the ship propulsion system is obtained. The improvement of the acceleration performance for the considered fast ferry is obtained by means of a careful choice of the telegraph setting, able to maintain, in combination with the gas turbine governor, each of the propulsion system components within its correct operative range. According to this concept, in order to optimize the acceleration performance of the ship, different acceleration manoeuvres have been considered and analyzed, by applying to the telegraph a setting logic similar to that used for the slam acceleration of a turbojet propelled aircraft. The analysis of the results puts into evidence the considerable improvement of the ferry acceleration performance allowed by the here proposed telegraph setting logic, as compared with an analogue acceleration manoeuvre obtained using a less sophisticated telegraph setting.