Architecture-Dependent LNG Tank Pressure Management in Dual-Fuel Ships

Alternative liquefied natural gas (LNG) fuel gas supply system (FGSS) architectures allocate fuel delivery, tank-pressure management, and boil-off gas (BOG) management to different components, creating operating-mode-dependent functional relationships. This study develops a dynamic model of three representative low-pressure architectures based on pressure build-up, pumping, and pumping with compression, and compares them under LNG-only and dual-fuel operating profiles. The LNG tank submodel was validated against published experimental data, with a mean relative pressure deviation below 2.5%. The comparison considers pressure margin, BOG management, energy demand, configuration-specific implementation requirements, and sensitivity to key parameters. Under the dual-fuel profile, pressure margins were 0.50, 0.73, and 3.10 bar for FGSS 1–3, respectively. FGSS 3 required no excess BOG discharge in the base case but had approximately 10.5 times the specific mechanical-energy demand of FGSS 2. Fuel demand most strongly affected voyage endurance, whereas insulation performance strongly influenced tank pressure and BOG management. At the highest insulation thermal conductivity investigated, FGSS 3 reached the maximum allowable working pressure during conventional-fuel operation when compressor-assisted BOG removal was intentionally not used under the adopted strategy. The results show that performance depends on functional allocation, installed capabilities, operating strategy, evolving tank state, and available BOG management pathways, thereby supporting conceptual architecture screening.