This study investigated thickness requirements for field fabricated (large) spherical liquefied natural gas (LNG) pressure vessels using the finite element method. In the FEM modeling, 3-dimenisonal analysis was used ...This study investigated thickness requirements for field fabricated (large) spherical liquefied natural gas (LNG) pressure vessels using the finite element method. In the FEM modeling, 3-dimenisonal analysis was used to determine thickness requirements at different sections of a 5-m radius spherical vessels based on the allowable stress of the material as given in ASME Section II Part D. Shallow triangular element based on shallow shell formation was employed using area coordinate system which had been proved better than the global coordinate system in an earlier work of the authors applied to shop built vessels. This element has five degrees of freedom at each corner node-five of which are the essential external degrees of freedom excluding nodal degree of freedom associated with in plane shell rotation. Set of equations resulting from Finite Element Analysis were solved with computer programme code written in FORTRAN 90 while the thickness requirements of each section of spherical pressure vessels subjected to different loading conditions were determined. The results showed membrane thickness decreasing from the base upwards for LNG vessels but constant thickness for compressed gas vessels. The obtained results were validated using values obtained from ASME Section VIII Part UG. The results showed no significant difference (P > 0.05) with values obtained through ASME Section VIII Part UG.展开更多
This work builds on an earlier work done which used global coordinates where a large number of elements were needed to form a convergence of results for shop built spherical pressure vessels. In this work area coordin...This work builds on an earlier work done which used global coordinates where a large number of elements were needed to form a convergence of results for shop built spherical pressure vessels. In this work area coordinates were used. Any action that leads to an inability on the part of a structure to function as intended is known as failure. This research, therefore, investigates stresses developed in a shop built carbon steel spherical storage vessels using finite element approach as the analytical tool. 3-D finite element modeling using 3-node shallow triangular element with five degrees of freedom at each node is employed. These five degrees of freedom are the essential nodal degrees of freedom without the sixth in-plane rotation. The resulting equations from finite element analysis are coded using FORTRAN 90 computer programme. Spherical storage vessels are subjected to various internal loading pressures while nodal displacements, strains and the corresponding maximum Von-mises stresses are determined. The calculated maximum Vonmises stresses are compared with the yield strength of the shell plate material. Using specified safety factor, safety internal pressures with the corresponding shell thicknesses for shop built spherical pressure vessels are determined. The finite element modeling carried out in this research can be used to predict in-service stresses, strains, and deformations of shop built spherical pressure vessels using Von-mises yield stress as the failure criteria. The results obtained were validated by analytical method and it showed there was no significant difference (P > 0.05) with values obtained through analytical method.展开更多
我国LNG动力渔船数量逐渐增多,前景广阔。LNG在由储罐进入动力装置利用之前会释放出大量冷能,为了有效的利用这部分冷能,提出了将LNG冷能用于渔船发电及冷库制冷相结合冷能利用系统,实现了系统及冷库内部冷能的梯级利用。利用HYSYS软件...我国LNG动力渔船数量逐渐增多,前景广阔。LNG在由储罐进入动力装置利用之前会释放出大量冷能,为了有效的利用这部分冷能,提出了将LNG冷能用于渔船发电及冷库制冷相结合冷能利用系统,实现了系统及冷库内部冷能的梯级利用。利用HYSYS软件对该冷库系统进行流程模拟及热力学计算分析。计算结果表明,该冷库系统的系统能效(COP)为1.86,效率为82.05%。其中LNG换热器的损失最大,为4.08 k W。实现了LNG动力渔船冷库冷能利用率及效率的大幅提高,节能效果显著,为LNG动力渔船冷能的高效利用提供了参考。展开更多
随着传统燃料价格的不断上涨,国际海事组织对船舶排放的新法规不断出台,人们对作为清洁燃料的LNG的需求正不断增加。以4000m3薄膜型(MARK III FLEX)LNG加注船为研究对象,从总布置设计、线型开发、液货舱设计及稳性等方面进行了总体设计...随着传统燃料价格的不断上涨,国际海事组织对船舶排放的新法规不断出台,人们对作为清洁燃料的LNG的需求正不断增加。以4000m3薄膜型(MARK III FLEX)LNG加注船为研究对象,从总布置设计、线型开发、液货舱设计及稳性等方面进行了总体设计研究,为进入该领域积累了经验。展开更多
文摘This study investigated thickness requirements for field fabricated (large) spherical liquefied natural gas (LNG) pressure vessels using the finite element method. In the FEM modeling, 3-dimenisonal analysis was used to determine thickness requirements at different sections of a 5-m radius spherical vessels based on the allowable stress of the material as given in ASME Section II Part D. Shallow triangular element based on shallow shell formation was employed using area coordinate system which had been proved better than the global coordinate system in an earlier work of the authors applied to shop built vessels. This element has five degrees of freedom at each corner node-five of which are the essential external degrees of freedom excluding nodal degree of freedom associated with in plane shell rotation. Set of equations resulting from Finite Element Analysis were solved with computer programme code written in FORTRAN 90 while the thickness requirements of each section of spherical pressure vessels subjected to different loading conditions were determined. The results showed membrane thickness decreasing from the base upwards for LNG vessels but constant thickness for compressed gas vessels. The obtained results were validated using values obtained from ASME Section VIII Part UG. The results showed no significant difference (P > 0.05) with values obtained through ASME Section VIII Part UG.
文摘This work builds on an earlier work done which used global coordinates where a large number of elements were needed to form a convergence of results for shop built spherical pressure vessels. In this work area coordinates were used. Any action that leads to an inability on the part of a structure to function as intended is known as failure. This research, therefore, investigates stresses developed in a shop built carbon steel spherical storage vessels using finite element approach as the analytical tool. 3-D finite element modeling using 3-node shallow triangular element with five degrees of freedom at each node is employed. These five degrees of freedom are the essential nodal degrees of freedom without the sixth in-plane rotation. The resulting equations from finite element analysis are coded using FORTRAN 90 computer programme. Spherical storage vessels are subjected to various internal loading pressures while nodal displacements, strains and the corresponding maximum Von-mises stresses are determined. The calculated maximum Vonmises stresses are compared with the yield strength of the shell plate material. Using specified safety factor, safety internal pressures with the corresponding shell thicknesses for shop built spherical pressure vessels are determined. The finite element modeling carried out in this research can be used to predict in-service stresses, strains, and deformations of shop built spherical pressure vessels using Von-mises yield stress as the failure criteria. The results obtained were validated by analytical method and it showed there was no significant difference (P > 0.05) with values obtained through analytical method.
文摘我国LNG动力渔船数量逐渐增多,前景广阔。LNG在由储罐进入动力装置利用之前会释放出大量冷能,为了有效的利用这部分冷能,提出了将LNG冷能用于渔船发电及冷库制冷相结合冷能利用系统,实现了系统及冷库内部冷能的梯级利用。利用HYSYS软件对该冷库系统进行流程模拟及热力学计算分析。计算结果表明,该冷库系统的系统能效(COP)为1.86,效率为82.05%。其中LNG换热器的损失最大,为4.08 k W。实现了LNG动力渔船冷库冷能利用率及效率的大幅提高,节能效果显著,为LNG动力渔船冷能的高效利用提供了参考。
