海上LNG液舱晃荡及储运安全规律的研究
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摘要
液化天然气(LNG)作为一种清洁、高效、方便、安全的能源,以其高热值、环保、储运方便等优点成为现代人类社会选择的优质能源之一。特别是近些年来,随着全球LNG生产和贸易的日益活跃,液化天然气行业正成为全球增长最快的能源行业之一。一些能源大国也越来越重视LNG的引进,在这条贸易链中,LNG船作为海上运输的主要工具成为各国建造的热点。在LNG船的建造过程中,一些技术问题凸显出来,液货的晃荡就是其中一个亟待解决的问题。液货在液舱中剧烈的晃荡会引起围护结构的破坏;同时,由于LNG的易燃性和低温性,一旦发生泄漏,后果也是十分严重的。
本文基于CFD(计算流体力学)方法对目前比较常用的液舱型式——薄膜型液舱进行了相关的研究计算。通过VOF(流体体积函数)法建立晃荡数值模型,研究了LNG液舱对液货晃荡的敏感性。研究发现:液货对液舱的冲击程度主要受到外部激励方式、液货充装水平和激励周期条件的影响。在这些影响因素中,外部激励周期占主导地位,一旦激励周期接近液体的共振周期,液货对液舱的冲击作用是最大的,液体的波动高度也是最高的,对液货储存安全造成了巨大的威胁。因此,在实际设计和操作过程中,要尽量避免激励周期接近液体的共振周期。针对上述问题,分析了薄膜型液舱充装水平对晃荡的敏感性,得出充满度液面在小于10%或大于70%以内最佳,对晃荡的敏感性最小。同时就存在的三种主要液舱型式(薄膜型、球型和SPB型),通过液舱受力的变化情况来判断液舱内液货的晃荡程度。对比研究发现:SPB型液舱具有良好的防晃荡特性,薄膜型最差。
在LNG运输的过程中同时伴随着液体的蒸发,由于LNG船的液舱承压能力有限,一般为常压储存,因此对于围护结构的保温特性有严格的要求。考虑到液舱内压力升高问题,分别对保温结构、液舱容积、外界环境温度和充满度等方面进行了相关模拟,找出了影响压力变化的规律。本次研究可以为LNG船在设计和制造过程中提供较高的参考价值。
As a clean, efficient, convenient and safe energy, Liquefied natural gas (LNG) with the merits of high thermal value, environmental protection, convenient storage and transportation has been becoming the high-quality energy in modern human society. Especially in recent years, as the global LNG production and trade has become increasingly active, liquefied natural gas industry is becoming one of the fastest growing energy businesses in the global. A number of energy countries pay more and more attention to the introduction of LNG and focus on the construction of LNG ships for LNG transportation in LNG trade chain. However, some technical problems are discovered in the process of LNG ships’construction, and the sloshing of liquid cargo is one of the problems to be solved. Liquid cargo sloshing in the tank can cause severe damage of cargo containments; at the same time, because of LNG's flammability and low temperature, the consequences caused by the event of leakage are very serious.
Based on the computational fluid dynamics (CFD) method, the membrane tanks which types are now commonly used are studied in this paper. The sloshing sensitivity of liquid cargo has been studied through the volume of fluid method (VOF) to establish sloshing numerical model. It is found that the impact strength of liquid cargo is mainly influenced by external excitation patterns, liquid filling rate and excitation period and so on. In these factors, the external excitation period is dominant; and once the excitation period is close to the resonance excitation period of liquid cargo, the impact force is the largest, and the wave motion is the highest, which cause the great threat on the safe storage of liquid cargo. Therefore, it is needed to avoid the excitation period close to the liquid resonance excitation period in the actual designing and operating process. According to the problems above, the sloshing sensitivity of the filling rate in membrane tank was analyzed and it is found that the best filling rate is less than 10% or lager than 70% which range is the least sensitivity of sloshing. At the same time, the sloshing extent of liquid cargo in the three main tank types involved of membrane-type, sphere-type and SPB-type are determined by force analysis. It showed by comparison that SPB-type tank have a good anti-sloshing characteristic, while membrane-type is on the contrary.
Because of limited pressure-bearing capacity in LNG tank, which is commonly at atmospheric pressure in the process of LNG transportation accompanied by liquid evaporation, there are strict requirements for insulation properties of the containments. Considering the problem of pressure rise in tanks, the insulation of the structure, tank volume, the external environment temperature and filling rate were respectively simulated and the influence effect of the pressure variation were identified. In a word this study provides some references for design and manufacture of LNG ships.
本文基于CFD(计算流体力学)方法对目前比较常用的液舱型式——薄膜型液舱进行了相关的研究计算。通过VOF(流体体积函数)法建立晃荡数值模型,研究了LNG液舱对液货晃荡的敏感性。研究发现:液货对液舱的冲击程度主要受到外部激励方式、液货充装水平和激励周期条件的影响。在这些影响因素中,外部激励周期占主导地位,一旦激励周期接近液体的共振周期,液货对液舱的冲击作用是最大的,液体的波动高度也是最高的,对液货储存安全造成了巨大的威胁。因此,在实际设计和操作过程中,要尽量避免激励周期接近液体的共振周期。针对上述问题,分析了薄膜型液舱充装水平对晃荡的敏感性,得出充满度液面在小于10%或大于70%以内最佳,对晃荡的敏感性最小。同时就存在的三种主要液舱型式(薄膜型、球型和SPB型),通过液舱受力的变化情况来判断液舱内液货的晃荡程度。对比研究发现:SPB型液舱具有良好的防晃荡特性,薄膜型最差。
在LNG运输的过程中同时伴随着液体的蒸发,由于LNG船的液舱承压能力有限,一般为常压储存,因此对于围护结构的保温特性有严格的要求。考虑到液舱内压力升高问题,分别对保温结构、液舱容积、外界环境温度和充满度等方面进行了相关模拟,找出了影响压力变化的规律。本次研究可以为LNG船在设计和制造过程中提供较高的参考价值。
As a clean, efficient, convenient and safe energy, Liquefied natural gas (LNG) with the merits of high thermal value, environmental protection, convenient storage and transportation has been becoming the high-quality energy in modern human society. Especially in recent years, as the global LNG production and trade has become increasingly active, liquefied natural gas industry is becoming one of the fastest growing energy businesses in the global. A number of energy countries pay more and more attention to the introduction of LNG and focus on the construction of LNG ships for LNG transportation in LNG trade chain. However, some technical problems are discovered in the process of LNG ships’construction, and the sloshing of liquid cargo is one of the problems to be solved. Liquid cargo sloshing in the tank can cause severe damage of cargo containments; at the same time, because of LNG's flammability and low temperature, the consequences caused by the event of leakage are very serious.
Based on the computational fluid dynamics (CFD) method, the membrane tanks which types are now commonly used are studied in this paper. The sloshing sensitivity of liquid cargo has been studied through the volume of fluid method (VOF) to establish sloshing numerical model. It is found that the impact strength of liquid cargo is mainly influenced by external excitation patterns, liquid filling rate and excitation period and so on. In these factors, the external excitation period is dominant; and once the excitation period is close to the resonance excitation period of liquid cargo, the impact force is the largest, and the wave motion is the highest, which cause the great threat on the safe storage of liquid cargo. Therefore, it is needed to avoid the excitation period close to the liquid resonance excitation period in the actual designing and operating process. According to the problems above, the sloshing sensitivity of the filling rate in membrane tank was analyzed and it is found that the best filling rate is less than 10% or lager than 70% which range is the least sensitivity of sloshing. At the same time, the sloshing extent of liquid cargo in the three main tank types involved of membrane-type, sphere-type and SPB-type are determined by force analysis. It showed by comparison that SPB-type tank have a good anti-sloshing characteristic, while membrane-type is on the contrary.
Because of limited pressure-bearing capacity in LNG tank, which is commonly at atmospheric pressure in the process of LNG transportation accompanied by liquid evaporation, there are strict requirements for insulation properties of the containments. Considering the problem of pressure rise in tanks, the insulation of the structure, tank volume, the external environment temperature and filling rate were respectively simulated and the influence effect of the pressure variation were identified. In a word this study provides some references for design and manufacture of LNG ships.
引文
[1]陈科,李俊峰,王天舒.矩形储箱内液体非线性晃动动力学模型与分析[J].力学学报, 2005, 37(3): 339-345
[2]范喜哲,郑天心,何雪,等.大型立式储油罐地震反应分析[J].低温建筑技术, 2007(4): 74-75
[3]李俊峰,鲁异,宝音贺西,等.贮箱内液体小幅晃动的频率和阻尼计算[J].工程力学, 2005, 22(6): 87-90
[4]包光伟.平放柱形贮箱内液体晃动的等效力学模型[J].上海交通大学报, 2003, 37(12): 1961-1968
[5]李英波,冯正进.充液航天器液体晃动等效力学模型的建立[J].上海航天, 2003, (4): 1-5
[6]李松,高芳清,杨翊仁,等.液体晃动有限元模态分析及试验研究[J].核动力工程,2007,28(4): 54-57
[7] Harlow F., Welch J.E.. Numerical calculation of time-dependent viscous incompressible flow of fluid with a free surface [J]. Phys Fluids, 1965, V8(12): 2182-2189
[8] Welch J.E., Harlow F.H., Shannon J.P., et al. The MAC method. Technical Report LA-3425 [J], Los Alamos National Laboratory, 1965
[9] Amsden A., Harlow F.. The SMAC method: a numerical technique for calculating incompressible fluid flows [J]. Technical Report LA-4370, Los Alamos National Laboratory, 1970
[10] Hirt C.W., Nichols B.D.. Volume of fluid (VOF) method for dynamics of free boundary [J]. Journal of Computational Physics, 1981, V39(1): 201-225
[11]沈猛,王刚,唐文勇.基于改进VOF法的棱形液舱液体晃荡分析[J].中国造船, 2009, 50(1): 1-9
[12]杨魏,吴玉林,刘树红.圆柱箱体中液体晃动阻尼的数值研究[J].工程热物理学报, 2009, 30(2): 220-222
[13] Osher S., Sethian J.A.. Fronts propagating with curvature dependent speed: algorithms based on Hamilton-Jacobi formulations [J]. Journal of Computational Physics, 1988, V79(1): 12-49
[14]朱仁庆,方志勇,张照钢,等. Level-Set法预报液舱内剧烈晃荡引起的冲击压强[J].船舶力学, 2008, 12(3): 344-351
[15]赵兰浩,李同春,牛志伟,等.刚性容器内流体非线性大幅晃动的数值模拟[J].河海大学学报, 2006, 34(4): 401-405
[16]王建军,陆明万,张雄,等.自由液面流体大晃动有限元方法[J].水动力学研究与进展, 2001, 16(3): 390-395
[17]耿利寅,李青.容器内液体晃动的变分有限元方法[J].低温与特气, 2002, 20(6): 22-25
[18]陈建平,周儒荣,韦忠瑄.用结构有限元程序进行液体晃动动力分析[J].中国机械工程, 2003, 14(19): 1631-1633
[19] Mitra S., Sinhamahapatra K.P.. 2D simulation of fluid-structure interaction using finite element method [J]. Finite Elements in Analysis and Design, 2008, V45: 52-59
[20]王小贞,臧跃龙.边界元法分析粘性液体小幅晃动[J].力学季刊, 2001, 22(4): 455-459
[21] Lucy L.B.. A numerical approach to the testing of fusion process [J]. J.Astron, 1977, V82: 1013-1024
[22] Monaghan J.J.. Simulating free surface flows with SPH [J]. Journal of Computational Physics, 1994, V110(2): 399-406
[23] Delorme L., Iglesias A.S., Perez S.A.. Sloshing Loads Simulation in LNG Tankers with SPH [C]. International Conference on Computational Methods in Marine Engineering , 2005
[24] DNV-RP-C205 Environmental Conditions and Environmental Loads [S]. 2007
[25] Guru S.. Analysis and Optimization of Thermal Stratification and Self-Pressurization Effects in Liquid Hydrogen Storage Systems [J]. Journal of Energy Resources Technology, 1993, V115(3): 221-227
[26] Kourneta P., Ziomas I., Contini S., et al. Development of a model for simulating the variability of the physical properties of substance Stored in various storage tanks, in the presence of an external heat source [J]. Journal of Hazadous Materials, 1994, V39(1): 1-18
[27] John I. H.. Prediction of Self-Pressurization Cryogenic Propellant Tank [J]. J. Propulsion, 1990, V6: 14-15
[28]潘俊兴.低温液体容器静态憋压时的升压速度[J].低温工程, 1997, (5): 32-33
[29]尼瓦.费林,等著,赵运生,崔春娥,等译.液体低温系统[J].北京,低温工程编辑部, 1993: 25-47
[30]汪顺华.液化天然气气车燃料储存与供气特性研究[D].上海:上海交通大学, 2002
[31]周明顺,李博洋,王瑞宣. LNG船MOSS型液货舱蒸气绝热应用分析[J].造船技术, 2009, (2):1-2,16
[32]李博洋,李迪阳.液化天然气船隔热舱室温度场的仿真计算[J].中国航海, 2008, 31(4): 352-355,382
[33]李娟,汪荣顺,于耀华.低温绝热气瓶压力对日蒸发率的影响规律研究[J].低温与特气, 2005, 23(6): 8-15
[34]孙法峰. FPSO-LNG储罐储存特性及安全技术[D].青岛:中国石油大学(华东), 2010
[35]温正,石良辰,任毅如.流体计算应用教程[M].北京:清华大学出版社, 2009: 59-60
[36]刘应中,缪国平.船舶在波浪上的运动理论[M].上海:上海交通大学出版社出版, 1987
[37] Hakan Akyildiz, Erdem Unal. Experimental investigation of pressure distribution on a rectangular tank due to the liquid sloshing [J]. Ocean Engineering, 2005, V32: 1503-1516
[38] Delorme L., Colagrossi A.. A set of canonical problems in sloshing, Part 1: Pressure field in forced roll-comparison between experimental results and SPH [J]. Ocean Engineering, 2009, V36: 168-178
[39] Olsen H.. Unpublished Sloshing Experiments at the Technical University of Delft. Delft, The Netherlands, 1970
[40] Landrini M., Colagorossi A. and Faltisen O.M.. Sloshing in 2-D Flows by the SPH Method [C]. Proceeding of the 8th International Conference on Numerical Ship Hydrodynamics, Busan, Korea, 2003
[41] GD 10-2007,薄膜型液化天然气运输船检验指南(试行)[S].北京:人民交通出版社, 2007
[42]李海波,温宝贵.用短峰波理论预报南海浮式生产储油装置运动响应.中国海上油气, 2007, 19(5): 346-349
[43] Thomas Lamb, Regu Ramoo. The Application of a New Tank Comtainment System to ULTRA-Large LNG Carriers [C]. Offshore Technology Conference, 2009
[44] Wu G.X., Ma Q.W., Taylor R.E.. Numerical simulation of sloshing waves in a 3D tankbased on a finite element method [J]. Applied Ocean Research, 1998, V20: 337–355
[45] IGC CODE,国际散装运输液化气体船舶构造和设备规则[S]. MSC.61(48), 2002
[46]乔国发.影响LNG储存容器蒸发率因素的研究[D].东营:中国石油大学(华东), 2007
[2]范喜哲,郑天心,何雪,等.大型立式储油罐地震反应分析[J].低温建筑技术, 2007(4): 74-75
[3]李俊峰,鲁异,宝音贺西,等.贮箱内液体小幅晃动的频率和阻尼计算[J].工程力学, 2005, 22(6): 87-90
[4]包光伟.平放柱形贮箱内液体晃动的等效力学模型[J].上海交通大学报, 2003, 37(12): 1961-1968
[5]李英波,冯正进.充液航天器液体晃动等效力学模型的建立[J].上海航天, 2003, (4): 1-5
[6]李松,高芳清,杨翊仁,等.液体晃动有限元模态分析及试验研究[J].核动力工程,2007,28(4): 54-57
[7] Harlow F., Welch J.E.. Numerical calculation of time-dependent viscous incompressible flow of fluid with a free surface [J]. Phys Fluids, 1965, V8(12): 2182-2189
[8] Welch J.E., Harlow F.H., Shannon J.P., et al. The MAC method. Technical Report LA-3425 [J], Los Alamos National Laboratory, 1965
[9] Amsden A., Harlow F.. The SMAC method: a numerical technique for calculating incompressible fluid flows [J]. Technical Report LA-4370, Los Alamos National Laboratory, 1970
[10] Hirt C.W., Nichols B.D.. Volume of fluid (VOF) method for dynamics of free boundary [J]. Journal of Computational Physics, 1981, V39(1): 201-225
[11]沈猛,王刚,唐文勇.基于改进VOF法的棱形液舱液体晃荡分析[J].中国造船, 2009, 50(1): 1-9
[12]杨魏,吴玉林,刘树红.圆柱箱体中液体晃动阻尼的数值研究[J].工程热物理学报, 2009, 30(2): 220-222
[13] Osher S., Sethian J.A.. Fronts propagating with curvature dependent speed: algorithms based on Hamilton-Jacobi formulations [J]. Journal of Computational Physics, 1988, V79(1): 12-49
[14]朱仁庆,方志勇,张照钢,等. Level-Set法预报液舱内剧烈晃荡引起的冲击压强[J].船舶力学, 2008, 12(3): 344-351
[15]赵兰浩,李同春,牛志伟,等.刚性容器内流体非线性大幅晃动的数值模拟[J].河海大学学报, 2006, 34(4): 401-405
[16]王建军,陆明万,张雄,等.自由液面流体大晃动有限元方法[J].水动力学研究与进展, 2001, 16(3): 390-395
[17]耿利寅,李青.容器内液体晃动的变分有限元方法[J].低温与特气, 2002, 20(6): 22-25
[18]陈建平,周儒荣,韦忠瑄.用结构有限元程序进行液体晃动动力分析[J].中国机械工程, 2003, 14(19): 1631-1633
[19] Mitra S., Sinhamahapatra K.P.. 2D simulation of fluid-structure interaction using finite element method [J]. Finite Elements in Analysis and Design, 2008, V45: 52-59
[20]王小贞,臧跃龙.边界元法分析粘性液体小幅晃动[J].力学季刊, 2001, 22(4): 455-459
[21] Lucy L.B.. A numerical approach to the testing of fusion process [J]. J.Astron, 1977, V82: 1013-1024
[22] Monaghan J.J.. Simulating free surface flows with SPH [J]. Journal of Computational Physics, 1994, V110(2): 399-406
[23] Delorme L., Iglesias A.S., Perez S.A.. Sloshing Loads Simulation in LNG Tankers with SPH [C]. International Conference on Computational Methods in Marine Engineering , 2005
[24] DNV-RP-C205 Environmental Conditions and Environmental Loads [S]. 2007
[25] Guru S.. Analysis and Optimization of Thermal Stratification and Self-Pressurization Effects in Liquid Hydrogen Storage Systems [J]. Journal of Energy Resources Technology, 1993, V115(3): 221-227
[26] Kourneta P., Ziomas I., Contini S., et al. Development of a model for simulating the variability of the physical properties of substance Stored in various storage tanks, in the presence of an external heat source [J]. Journal of Hazadous Materials, 1994, V39(1): 1-18
[27] John I. H.. Prediction of Self-Pressurization Cryogenic Propellant Tank [J]. J. Propulsion, 1990, V6: 14-15
[28]潘俊兴.低温液体容器静态憋压时的升压速度[J].低温工程, 1997, (5): 32-33
[29]尼瓦.费林,等著,赵运生,崔春娥,等译.液体低温系统[J].北京,低温工程编辑部, 1993: 25-47
[30]汪顺华.液化天然气气车燃料储存与供气特性研究[D].上海:上海交通大学, 2002
[31]周明顺,李博洋,王瑞宣. LNG船MOSS型液货舱蒸气绝热应用分析[J].造船技术, 2009, (2):1-2,16
[32]李博洋,李迪阳.液化天然气船隔热舱室温度场的仿真计算[J].中国航海, 2008, 31(4): 352-355,382
[33]李娟,汪荣顺,于耀华.低温绝热气瓶压力对日蒸发率的影响规律研究[J].低温与特气, 2005, 23(6): 8-15
[34]孙法峰. FPSO-LNG储罐储存特性及安全技术[D].青岛:中国石油大学(华东), 2010
[35]温正,石良辰,任毅如.流体计算应用教程[M].北京:清华大学出版社, 2009: 59-60
[36]刘应中,缪国平.船舶在波浪上的运动理论[M].上海:上海交通大学出版社出版, 1987
[37] Hakan Akyildiz, Erdem Unal. Experimental investigation of pressure distribution on a rectangular tank due to the liquid sloshing [J]. Ocean Engineering, 2005, V32: 1503-1516
[38] Delorme L., Colagrossi A.. A set of canonical problems in sloshing, Part 1: Pressure field in forced roll-comparison between experimental results and SPH [J]. Ocean Engineering, 2009, V36: 168-178
[39] Olsen H.. Unpublished Sloshing Experiments at the Technical University of Delft. Delft, The Netherlands, 1970
[40] Landrini M., Colagorossi A. and Faltisen O.M.. Sloshing in 2-D Flows by the SPH Method [C]. Proceeding of the 8th International Conference on Numerical Ship Hydrodynamics, Busan, Korea, 2003
[41] GD 10-2007,薄膜型液化天然气运输船检验指南(试行)[S].北京:人民交通出版社, 2007
[42]李海波,温宝贵.用短峰波理论预报南海浮式生产储油装置运动响应.中国海上油气, 2007, 19(5): 346-349
[43] Thomas Lamb, Regu Ramoo. The Application of a New Tank Comtainment System to ULTRA-Large LNG Carriers [C]. Offshore Technology Conference, 2009
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