【作者】 顾妍；

【导师】 巨永林；

【作者基本信息】 上海交通大学 ， 制冷及低温工程， 2012， 博士

【摘要】 海洋蕴藏着丰富的天然气资源，储量约占世界天然气总产量的三分之一。我国近海海域也发育了一系列沉积盆地，总面积达近百万平方公里，具有丰富的海洋石油伴生气（即天然气）资源。随着能源开发技术的进步，海洋石油伴生天然气资源的开采、利用成为可能。作为一种新型的开发技术，浮式液化天然气生产储卸平台（LNG-FPSO）集液化天然气生产、储存与卸载于一身，简化了海洋天然气资源的开发流程，因其投资低、建造周期短、便于迁移的优点而倍受青睐。LNG-FPSO平台的储存、输送系统受到LNG低温特性以及平台运动的限制，无法直接采用现有海上石油平台的储运系统。作为LNG-FPSO的关键系统之一，海上浮动平台低温液体动态储运的相关研究亟待开展。本文正是基于此背景，提出开展低温液体动态储运的数值模拟与实验研究工作，并取得了一定的进展。本文的具体研究内容如下：基于海上FPSO浮动平台的LNG概念输送装置的形式，并结合中国南海油田伴生气气源条件，建立一套FPSO平台LNG输送系统的仿真流程。通过流程模拟与理论分析相结合的方法，研究了管径、流量以及海洋环境特有的平台高度差等因素对FPSO平台LNG输送性能的影响。研究发现合理设计输送流量可达到泵功消耗、闪蒸气体量最经济的效果，并且推导了流量经济值的计算式提供设计者参考；提出海洋浮动平台LNG输送系统的泵功消耗设计须考虑平台垂荡、摇摆引起的平台高度变化；选择输送管管径时须综合考虑成本、平台与船间距、管道弯曲半径的需求，在满足以上条件的前提下建议选择管径较大、管数少的管路方案；LNG产品组分中重烃和氮气含量将引起甲烷蒸发量的增加，因此在预处理、液化阶段建议尽量提高天然气中甲烷的纯度。基于以上研究结论，提出该海上浮动平台LNG输送系统的具体参数设计值，包括输送流速、管径等。针对输送系统中最主要的流体输送管道受外部运动的影响展开了理论分析与数值模拟。首先结合惯性、非惯性坐标的动量方程分析摇摆运动的管道流动，研究发现引起流场参数波动的主要因素是摇摆运动的频率、角度以及流速；推导了不考虑粘性时竖直管道、水平管道的压力波动波幅以及平均值的理论关系式。其次建立了三维摇摆管道的数值模型，采用动网格模型对摇摆运动管道进行动态数值模拟。预测了平台的摇摆频率、角度、管内液体流速对管中流体压力波动的影响。数值模拟发现压力的波动周期为2/0，摇摆管道内液体压力波动幅度随着管道摇摆频率、角度和液体流速的增大而增大。并且通过与理想流体模拟结果的比较，分析了摇摆管道内流体摩擦损失的波动规律，发现摇摆管道的平均摩擦压力损失以及摩擦压力损失波动幅度都随着摇摆运动的频率、角度、流速增大而增大，摩擦压力损失波动周期为2/0，并拟合了摇摆管道内流体平均摩擦压力损失修正系数经验关系式。按照相似性原理，设计并建立了原型系统40:1的FPSO平台低温液体输送系统的实验装置。提出并设计了驱动实验平台摇摆运动的机械机构，可模拟多种频率及角度的摇摆运动。同时，设计了绝热良好、测量准确、数据重复性佳的低温测试段，用于测试容器、管路温度、压力参数动态信号。开展了详细的FPSO平台低温液体动态输送的实验研究。首先对实验系统进行漏热分析和测试，发现平台摇摆的运动对于高速流动的低温保温管中流体的温度基本没有影响；其次，研究平台摇摆的频率、角度以及输送速度对于低温液体传输压力波动特性的影响规律，实验发现液体压力周期性波动规律与模拟结论一致，压力波动的周期由平台激励频率决定，周期值为2π/ω₀，压力波动幅度随着平台摇摆运动频率、角度及液体流速的增加而增加。将实验数据与数值模拟结果进行了比较，发现两者具有较好的吻合度，数值模型能够较为可靠的预测实际情况。最后，本文还针对FPSO平台低温液体的动态储存过程进行了实验测量。采用静态蒸发率参数测试低温储罐在静止状态的绝热性能。在此基础上设计多种摇摆运动工况，测试摇摆运动低温储罐24小时的气体蒸发率。发现储罐摇摆运动引起低温液体储存蒸发率的增大，摇摆频率、角度越大，低温液体动态蒸发率越大。更多还原

【Abstract】 It has been estimated that about one third of the total gas production inworld are contained in the deep oceans, in the forms of marginal gas fieldand oil-associated gas field. They are called stranded gas resources fortechnical and economical reasons. LNG-FPSO and similar units have beenproposed, and supposed to be the solution to the stranded gas resources. TheLNG-FPSO is a floating platform supporting gas-to-liquids process facilitiesand also storing and offloading LNG production in offshore areas. Due tothe remarkable advantages of lower capital, movability and reusability, thenovel unit LNG-FPSO is predicted to be the highlight in the field of offshoreenergy.There are several key technologies unsolved before to build a realLNG-FPSO. The transportation and storage systems of cryogenic liquidbetween floating platforms are limited by the cryogenic features and theplatform movement. The traditional systems on offshore oil platform can notbe directly used on LNG-FPSO. Therefore it is necessary to carry out theresearch on the processes of the transportation and storage of offshorecryogenic liquid. The thesis is based on this background and to carry out thedetailed numerical simulation and the experimental study.Based on the conceptual designs of the transporation process in literatures,and the associated gas conditions of Wenchang oil field in South China Sea,the LNG transportation process between the LNG-FPSO and LNG carrier isdesigned and simulated. Combining with theoretical analyses, the criticalparameters and their influences on the performance of the transportationsystem are investigated, including the flow rate, the pipeline diameter,etc. From the view of the pump power and BOG generation, it is found that there was an economic mass flow rate for practical design. The heightdifference of the pipeline must be considered for the increase of requiredpump head and harms from pressure changes. After meeting therequirements of the cost, ship distance and the bending radius of pipeline,the large diameter tube of small number is suggested when designing thepipeline program. By these findings, the values of key parameters of theLNG transportation system are proposed for associated gas in South ChinaSea, such as the flow velocity, the diameter, etc.Since the pipeline plays the most important role in the transportationsystem, the theoretical analysis and numerical simulations have beenconducted. Combining the inertial coordinate and the non-inertial coordinate,the momentum equation of the rolling pipeline is simplified and analyzedwithout considering the viscosity. The analyses help to discover theinfluencing factors on the flow parameters. The relationships of the pressureloss, the amplitude of the pressure fluctuation and the average pressure aretheoretically derived. In order to predict the influences of the factors on thefliud pressure, a pipeline physical model is established in CFD software.Using user-defined functions (UDF) and dynamic mesh model, the fluidflowing in the rolling pipeline is simulated, at the rolling frequencies of3-15rpm and the rolling angles of6-15°, respectively. It is found from thesimulation results that the pressure fluctuates in the period of2/0. Theamplitude of pressure fluctuation increases with the increase of the rollingfrequency, the rolling angle and the flow velocity. Compared with thesimulation results of ideal fluid, the friction loss of fluid in the rolling pipecan be gained. The friction loss fluctuates in the period of2/0as well.The fluctuation amplitude and the mean value of the friction loss grow withthe increase of the rolling frequency, angle and the flow velocity. Moreover,the modified coefficient of the mean frition loss in the rolling pipe is fitted.According to the similarity principle, a40:1experimental setup isdesigned and constructed, which could roll in different angles andfrequencies, to simulate the freedom of the platform movement in the ocean. The dynamic measurements of the temperature and pressure in thecryogenic tanks and pipeline are well designed, with adiabatic environment,accurate testing method, and good repeatability.In the experiments the cryogenic liquid will be transported between therolling platforms. First, through the heat leak calculation of the system andthe test data, it shows that the rolling motion has little effect on thetemperature of the high-velocity flow in the insulating pipe. Then theinfluences of the flow velocity and the rolling motion including the rollingfrequency and angle on the pressure characteristics of cryogenic liquid areinvestigated. It is found that the rolling motion of the platform causes theperiodically fluctuation of the pressure. The period of the pressurefluctuation is determined by the platform rolling frequency. The amplitudeof the pressure fluctuations increases with the increase of the rollingfrequency, angle and the flow velocity. In the cases in this paper, theamplitude of the pressure fluctuation is in the range of2~6kPa. Comparedwith the simulation results, it can be found that the pressure fluctuationcharacteristics in the experiments and that in the simulations are veryconsistent. The comparison illustrates that the numerical model is reasonableand reliable.The dynamic storage of cryogenic liquids is experimentally studied. Avariety of rolling motion conditions is designed when the cryogenic liquid isstored in the tank. The gas evaporation rate of the cryogenic tanks in24hours is tested. It is found that the evaporation rate increases caused by thetank rolling motion.更多还原