中小型LNG船货罐鞍座及附近船体材料分布研究

Materials Distribution of Cargo Tank Saddle and Nearby Hull Structure of Small and Medium LNG Carrier

C型独立液货罐是中小型LNG船的主要液舱形式,属于半冷半压式容器。由于贮存LNG的液货罐处于低温状态,且因与船体相连的鞍座支撑,在鞍座及附近船体上就会形成温度梯度,故有必要对鞍座及附近船体结构进行温度场分析,以确定其材料分布。提出了对该C型独立液货罐鞍座及其附近船体结构热分析的方法,认为鞍座及其附近船体处在低温液货、海水与空气3种流体介质中,通过船体与3种流体的对流换热及其与层压木之间的热传导达到热平衡。借助ANSYS有限元软件,给出有限元热分析模型的简化和对流载荷的施加方法,以确定鞍座及其附近船体结构的温度场分布,结合材料的最低许用设计温度确定鞍座及附近船体结构材料的合理分布,以防止材料发生低温脆性破坏,并给出具体实例。

The C-shape independent liquid cargo tank,the main liquid tank form of the small and medium LNG carrier,is a semi-chilled and semi-compressed container.Because of the low temperature around the liquid tank,which loads LNG and is supported by the saddle connected with hull structure,temperature gradient will be formed on the saddle and nearby hull structure.So it is necessary to analyze the temperature field about the saddle and nearby hull structure so as to determine the material distribution.The thermal analysis method for the saddle of the C-shape independent liquid cargo tank and nearby hull structure is proposed.It is considered that the bearing of the cargo tank and the nearby hull structure is surrounded by the three mediums,low-temperature liquid cargo,seawater and air,and achieves heat balance by convective heat transfer between hull and the three mediums and the heat conduction between hull and laminated wood.With the FEM software ANSYS,a simplified model for thermal analysis and the approach to applying convection load is given to determine the temperature field layout of the saddle and nearby hull structure.Meanwhile,combining with the allowable design temperature of the materials,the suitable materials distribution is given,which can prevent the material from the low-temperature break.An instance is given which is a meaningful attempt to solving the problem of the material distribution for the bearing and nearby hull structure surrounded by the low temperature.