Article Published In Vol.5 (Nov-Dec-2017)

Performance Analysis of Different Propulsion Systems for LNG Carriers

Author : Walid M Bahgat and Ahmed Salem

This paper analyses the performance of different propulsion systems which are used in LNG vessels. Additionally, it discusses the effect of replacing steam turbine with other prime movers at the same power. Furthermore, the paper includes the comparison between steam turbine, slow-speed diesel engine, gas turbine, combined diesel and steam cycle and combined gas and steam cycle with respect to its performance that comprise the thermal efficiency, SFC specific fuel consumption and the boil-off gas SFC for each one. In a nut shell, it could be noticed that the steam turbine and gas turbine propulsion systems are almost equal in thermal efficiency and a quiet difference in SFC. After words, there is a slight increase in thermal efficiency and specific fuel consumption by applying the combined cycle gas and steam. Moreover, by using diesel engine propulsion system the thermal efficiency went up to 52.26 % and the SFC reached its lowest value, the thermal efficiency value of the combined cycle diesel and steam climbed to 58.36 % with considerable decrease in SFC. Finally, by knowing the fuel consumption for each propulsion system, the most efficient propulsion system can be identified.

Keywords: Propulsion systems; steam turbine, slow-speed diesel engine, gas turbine, thermal efficiency