舶用ガスタービンコンバインドサイクルのシステム検討

抄録

  Combined cycle is often called as the hybrid power generation system composed of a gas turbine and a steam turbine where the steam turbine is powered by exhaust gas heat from the gas turbine. Emission control requirement of the exhaust gas and the fuel oil price forecast have induced to choose the liquefied natural gas (LNG) as alternative to fuel oil, which offers more options of marine power source including the combined cycle.

This paper reviews technologies related to the marine LNG-fueled combined cycle, primarily: working fluid, exhaust gas heat exchanger, and compact steam prime mover. The case study of the marine combined cycle is also proposed, in which the working fluid is set to water, exhaust gas heat exchanger is set to hi-finned tube heat exchanger and compact steam prime mover is set to hi-speed radial turbine. Supposing the gas turbine with rated power of 22,370kW, operating at 100% of power with 40% efficiency, and steam turbine with 80% efficiency; steam condition at the exit of the heat exchanger is 0.3MPa and 573K to gain larger expansion ratio in the steam turbine and more total output of the combined cycle. The case study predicted 3,381kW output by two-stages of the radial steam turbine and 44.06% total efficiency of this combined cycle.