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类型 应用研究 预答辩日期 2017-12-23
开始(开题)日期 2014-09-09 论文结束日期 2017-10-26
地点 东南大学榴园宾馆三江阁 论文选题来源 省(自治区、直辖市)项目    论文字数 7.7 (万字)
题目 海洋环境对浮式液化天然气平台关键设备的影响研究
主题词 浮式液化天然气平台,FLNG 储罐,管式换热器,液体晃荡,低温传热
摘要 浮式液化天然气平台(FLNG)将陆基天然气液化工厂转移至海上平台运行,形成一种全新的海洋天然气开采模式,可大幅缩减海洋边际气田的开发流程和前期投资,是未来海洋天然气资源开采的发展方向。但是陆基工厂采用的生产、储存设备在向海洋浮式平台转移时,由海洋环境引起的浮式平台晃动、倾斜会对设备运行的安全性和稳定性产生干扰,需要针对海洋环境进行设备的适应性分析和优化。本文基于计算流体力学对晃动环境下的FLNG储存关键设备 – 储罐,以及倾斜环境下的生产关键设备 – 换热器进行了数值模拟研究,通过分析储罐、换热器中工作流体受到海洋环境干扰时的运动、传热情况,研究了储罐底部结构、摆动-起伏耦合激励对液体晃荡特性和内腔压力分布的影响,以及蒸发气换热器对流量工况、倾斜环境的传热响应规律。取得如下创新性成果: (1)在液体晃荡行为的理论研究方面:提出参数峰值平均法对储罐内液体运动的剧烈程度进行量化评估,进而指导储罐晃荡固有频率的计算以及不同晃荡工况下的液体运动特性对比研究。参数峰值定义为液面高度、位移量、壁面压力等参数的时域局部极大值,对各波动周期内的参数峰值取算数平均数,可得到整个晃荡过程的唯一标量,即参数峰值平均数,该值代表了液体运动的剧烈程度,相同监测位置时,参数峰值平均数越大,表示当前工况下的液体运动越剧烈,激励频率越接近固有频率。由于其对参数的选择并无特殊要求,可兼容实验和仿真两种研究手段,实现液体运动剧烈程度的精确量化。 (2)在FLNG储存设备性能研究方面:建立FLNG储罐内流体晃荡数值模拟模型,引入摆动-起伏耦合激励模型,对不同频率成分的耦合激励作用结果进行了对比研究,针对不同储罐结构、液体填充率、激励参数作用下的液体晃荡行为进行了对比研究,从而获得不同工况下的储罐动态压力载荷。通过流体体积法和独立网格控制方法建立了薄膜式储罐内的液体晃荡模型,以正弦激励为对象,研究了储罐底部结构引起的固有频率漂移和晃荡特性改变规律。液体填充率较低时:随着斜坡尺寸的增大,晃荡固有频率逐渐减小,高压区域的影响范围以及峰值压力逐渐降低;填充率较高时:固有频率保持稳定,斜坡结构的优化作用小于填充率较低时的工况。此外,在研究摆动-起伏耦合激励时,对不同频率成分的耦合激励作用结果进行了对比研究。两种激励成分以频率比作为相互制约的参数,起伏频率较小时,液体运动由摆动激励主导,反之液体运动由起伏激励主导。起伏激励频率为摆动频率2倍时,液体运动达到晃荡特征的极限状态,此时起伏激励对晃荡运动的增益效果达到最大。 (3)在FLNG生产设备性能响应方面:在水平蒸发气换热器的流量工况响应研究基础上,增加倾斜环境的设置,研究了蒸发气换热器在不同倾斜环境下的传热性能响应规律。通过建立蒸发气换热器的数值模拟模型,分析换热器流场、温度场在不同运行工况下的性能参数,对水平环境下的流量工况响应规律进行了详细研究。蒸发气换热器各出口温度随壳程流量的改变呈单向响应变化,响应灵敏度在低流速时较大、高流速较小;高壳程质量流工况时,换热器具有更好的稳定性和更为合理的流场、温度场分布,而当壳程质量流低于一定阀值时,两个流域出现温度交叉现象,低温流体的出口温度高于高温流体,出现不必要的反向传热,流场结构与当前工况的匹配性较差。倾斜环境下的换热器响应研究发现:轴向倾向对换热器性能的影响大于径向倾斜,且壳程质量流较低时的换热器比高质量流时更易受到环境因素变化的影响。 (4)在实验验证及工程应用方面:通过相近工况下的FLNG储罐及换热器实验研究,对本文通过数值模拟方法获得的研究结论进行验证,并将其应用于橇装式小型船用蒸发气再液化工厂的工程研制中。针对海洋环境的设备性能仿真研究,可在设计阶段对设备进行适应性分析、载荷校核、工况预测,进而对陆基天然气液化设备和技术进行校验和改造,实现陆地工厂设备向海洋平台的转移,缩短海洋平台的研制周期。
英文题目 INFLUENCE STUDY OF MARITIME ENVIRONMENT ON THE KEY EQUIPMENT OF FLOATING LIQUEFIED NATURAL GAS
英文主题词 Floating Liquefied Natural Gas, FLNG storage tank, Tubular heat exchanger, Sloshing, Cryogenic thermodynamics
英文摘要 Floating Liquefied Natural Gas (FLNG) is a maritime platform settled near the gas field on the ocean. It’s equipped with natural gas pretreatment, liquefaction, storage and offloading system. With all these systems, FLNG is expected to replace onshore liquefaction factory and starts a brand new modal for the exploitation of maritime natural gas. This new modal can save the investment of subsea pipeline and the construction time of onshore factory. After the exploitation of one gas field, it can be shipped to another one without any further infrastructure. These advantages make FLNG become the future direction of exploiting maritime resources. But as a high-tech maritime platform, there are still some scientific and engineering problems to be solved, particularly the adaptability and the reliability of onshore equipment working in an ocean environment. In this work, computational fluid dynamics methods, such as Volume-of-Fluid, fluid control equations are used to simulate the fluid sloshing in a membrane FLNG storage tank and the thermodynamic flow in a tubular heat exchanger. The influence from tank shape, environmental disturbance has been studied to get a better understanding of pressure distribution inside the tank, liquid behavior under different excitations and thermal response of heat exchanger in different working conditions. Major outcomes are elucidated as follows. (1) Evaluation model of sloshing behavior in a partly filled tank. Averaged peak value is applied to evaluate the liquid sloshing in a FLNG tank. Based on this quantitative evaluation, natural frequency and sloshing characteristic can be analyzed under different excitation conditions. Peak value can be the local maximum value of fluid depth, fluid displacement or hydraulic pressure on the wall. By calculating the average peak value of one selected parameter, liquid behavior during the whole sloshing can be described. Bigger value means the liquid sloshing is more violent and the excitation frequency is much closer to the natural frequency. As the value selection is not limited to simulation parameters, this method has a good compatibility in both numerical and experimental analysis. (2) Study on FLNG storage equipment: Based on Volume-of-Fluid method and independent grid building, numerical model of liquid sloshing in a FLNG membrane tank has been built. Sinusoidal excitation is applied to the tank to study the liquid behavior. With a lower filling rate, natural frequency of sloshing will decrease with the growing of bottom slopes. Bigger slope comes out with lower hydraulic pressure on the bottom. But with a higher filling rate, this affection from bottom slope is weaken and the peak pressure on the bottom is barely changed by enlarging the slopes. Coupled rotate-heave excitation is added to the VOF model of tank sloshing to study the liquid behavior in this complicated disturbance. Frequency ratio between heave and rotate excitations works like balance parameter. When the frequency ratio is small, liquid behavior is dominated by rotate excitation. In a bigger ratio, liquid flow pattern is more likely controlled by heave excitation. The balance value of frequency ratio is 2, where the rotate sloshing pattern increases to the largest amplitude. Impact pressure from liquid can be several times larger than the steady liquid. This balance pattern can be found in all filling rates. (3) Study on FLNG production equipment: Heat exchanger, as a key equipment in the production process, is used to transfer thermal energy between different working fluids. Thermal distribution and response of heat exchanger are studied under different situation. Reading from the simulation results, outlet temperature of heat exchanger is a one-way corresponding parameter to the mass flow rate of shell-side flow. Outlet temperature is more sensitive in lower mass flow rates and therefore more stable in high mass flow conditions. Temperature cross between tube and shell outlets will be found when the mass flow is smaller than a specific value, which means the heat exchanger doesn’t match with the working condition. After this, inclination condition is added to the heat exchanger to study the influence from inclination angle and location. It’s found that longitude inclination has a larger thermodynamic affection than the radial inclination. Heat exchanger working in lower mass flow rate is easier to be affected by spatial inclinations. (4) Experimental validation and application in industry: Analysis results from numerical simulation are validated by some similar experiments and then applied to the design of skid-mounted BOG reliquefaction system for the maritime platform. All these performance studies and loading calculations are used to optimize the land-factory equipment, so that they can adapt to the maritime environments by a shorter developing process.
学术讨论
主办单位时间地点报告人报告主题
东南大学机械工程学院 2013.11.07 机械楼201 严岩 吸油烟机仿真项目工作进展汇报
东南大学机械工程学院 2014.6.11 机械楼410 林元载 流固耦合作用下混合物气液二相流模型
东南大学机械工程学院 2015.7.3 机械楼201 严岩 FLNG自由液面运动过程模拟研究
UW-Madison 2015.9.8 Engineering Hall 严岩 Overview of Ph.D. project – FLNG
UW-Madison 2016.5.3 Engineering Hall 严岩 Free surface simulation of liquefied natural gas in a typical FLNG tank
东南大学机械工程学院 2016.10.8 机械楼201 严岩 联合培养学术交流
东南大学机械工程学院 2016.11.3 机械楼201 严岩 不同液体对FLNG储罐固有频率的影响
东南大学机械工程学院 2016.12.15 机械楼201 严岩 不同底部结构对FLNG储罐固有频率的影响
     
学术会议
会议名称时间地点本人报告本人报告题目
OMAE2017 2017.6.25-30 挪威-特隆赫姆 Numerical study of bottom shape effect on pressure performance in a sloshing FLNG membrane tank
CEC2017 2017.7.9-13 美国-威斯康辛麦迪逊 Numerical study of longitudinal inclination effect on a tubular BOG heat exchanger
     
代表作
论文名称
Numerical study of heat transfer characteristics in BOG heat exchanger
Numerical study on thermal performance of a BOG heat exchanger in the inclined condition
Motion behavior research of liquid micro-particles filtration at various locations in a rotational f
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
张广明 正高 教授 博导 南京工业大学
刘英 正高 教授 博导 南京林业大学
杨继全 正高 教授 硕导 南京师范大学
薛烽 正高 教授 博导 东南大学
赵剑锋 正高 教授 博导 东南大学
      
答辩秘书信息
姓名职称工作单位备注
项楠 其他 讲师 东南大学