Samsung Heavy Industries Co., Ltd
12:15 - 12:45
Wednesday, 18 September 2019
T2.4 Sloshing in Membrane Tank for LNG Fuelled Ultra-large Containership
LNG fuel, which is environmentally friendly energy resource, has attracted a great deal of interest from ship owners as an alternative to meet IMO's enhanced environmental regulations. Recent researches say LNG fuel propulsion system can be applied to containerships with high efficiency and membrane type cargo containment systems are suitable because large capacity LNG fuel is required for ocean voyage of containerships. A research on the LNG fuel tank with KC-1 membrane technology of KC LNG Tech was performed for the ultra-large LNG fuelled containership of 23,000TEU designed by Samsung Heavy Industries (SHI). The required capacity of fuel tank was 18,300 cbm. The fuel tank was placed under the wheel house to avoid reducing the container loading space. As a result, the inner width of the fuel tank became as wide as 50 m. The wider the tank width, the higher the possibility of sloshing impact on the side wall is expected due to the wave breaking phenomenon under partial filling conditions. To lower the risk of sloshing for this wide LNG fuel tank, the lower chamfer height was increased. In addition, the side wall height and upper chamfer length were designed to be similar to each other so that the flow over the wall smoothly escapes without causing huge impact pressures. At first, the effect of the proposed design was examined by ABS SLOSH, a numerical sloshing analysis program of ABS. Then, a systematic sloshing evaluation was performed through model tests to investigate the sloshing impact loads under unlimited filling condition. The model test campaign was carried out using a 6-DOF motion platform of SSMB (Samsung Ship Model Basin) of SHI. A model tank with a scale ratio of 1/40 was used, and extreme wave conditions in the North Atlantic Ocean were considered as per IGF Code for unrestricted area service. A total of 176 pressure sensors were placed at the positions where high sloshing impact loads are expected to occur based on the previous experiences. In addition, CFD sloshing analysis was performed to analyze the impact pressure distribution on the area where sensors were not covered to check if hot spots were missed during the model test. In the sloshing experiment, both ballast and design load conditions were considered and it was found that the sloshing impact pressure could be high even under design load condition where roll motion is relatively small. Design sloshing load curve for hot spot area was analyzed and compared with the experimental results for the cargo tank of 174K LNGC, which is a reference vessel. Through the research, it was demonstrated that the present membrane LNG fuel tank design is suitable for the ultra-large LNG fuelled containership of 23,000TEU.