LNG液舱晃荡冲击比尺效应的实验研究

发布时间：2018-05-17 20:53

本文选题：二维八边形液舱 + 比尺效应　；参考：《大连理工大学》2015年硕士论文

【摘要】：随着人类将油气资源开采的目光由陆地转向海洋,浮式液化天然气平台(FLNG)成了世界各国竞争的一个新型装备制高点。但其运营过程中储液舱内部存在严重的流体晃荡冲击问题,所以,一直都是海洋工程领域的研究热点。目前,室内模型实验是研究储液舱晃荡的重要手段。其相对于理论方法和数值方法而言,可以得到更加有效的结果来指导工程实际。但通过人们开展大量的晃荡模型实验研究发现,在实验过程中将不同比尺模型液舱得到的结果还原到原型时,会与原型实测结果之间存在不同程度的偏差,即比尺效应。鉴于此,本文通过调研国内外研究进展,系统总结了晃荡比尺效应的实验研究方法；针对海洋油气储运装备中经常采用的GTT薄膜型储舱,构建三个不同比尺的二维八边形液舱,并在室内开展了三个液舱之间的晃荡冲击比尺效应实验研究。研究给出了详细的分析流程,并建立了完善的室内半物理仿真实验平台。在实验开始前,通过几何相似和弗劳德相似对运动激励、模型液舱、传感器布置位置和实验时间等主要影响因素均进行相似缩比。实验所得晃荡荷载结果还原同样依据弗劳德相似实现,特别是在长时间激励作用下,实验引入了数理统计方法来处理晃荡冲击压力峰值,并从三个比尺液舱同一位置的压力峰值超越概率分布研究了模型实验与原型实验之间的比尺效应。此次研究以20%低载液率和80%高载液率作为两个典型的载液工况,开展了三个比尺液舱在自由液面共振频率下,分别受到单次横荡冲击激励、长时间横荡和横摇规则激励作用下的晃荡冲击比尺实验。本文通过对比分析三个比尺液舱在同一位置晃荡冲击压力峰值的超越概率分布并结合相应的流场形态,研究了晃荡模型实验与原型实验之间的比尺效应。研究结果表明：在模型与原型液舱内同一位置都出现气体截留现象时,将模型实验在该位置得到的晃荡荷载根据弗劳德相似还原到原型后,与原型实验对应位置的结果偏差较大；当以上两种液舱内同一位置都受到气液混合流体冲击时,模型实验还原结果与原型实验实测结果之间的偏差会有所减小；只有当二者都受到不可压缩纯液体冲击时,由模型实验还原后的晃荡冲击压力结果才能相对真实地反映原型实验实测结果；考虑到原型液舱晃荡过程中许多特殊的物理现象在小比尺模型液舱内无法重现,因此,应尽可能开展大比尺模型实验来研究和评估原型液舱内的晃荡冲击机理。
[Abstract]:With the development of oil and gas resources from land to sea, floating liquefied natural gas platform (FLNGG) has become a new type of equipment in the world. However, there is a serious fluid sloshing impact problem in the tank, so it is always a hot topic in the field of ocean engineering. At present, indoor model experiment is an important means to study sloshing of tank. Compared with the theoretical method and numerical method, more effective results can be obtained to guide the engineering practice. However, through a large number of experiments on sloshing model, it is found that when the results obtained from different scale models are reduced to the prototype, there is a different degree of deviation between the experimental results and the measured results, that is, the scale effect. In view of this, through the research progress at home and abroad, this paper systematically summarizes the experimental research methods of sloshing scale effect, constructs three 2-D octagonal liquid tanks with different scales, aiming at the GTT thin film tank, which is often used in offshore oil and gas storage and transportation equipment. An experimental study of sloshing impact scale effect between three tanks was carried out indoors. The detailed analysis flow is given, and a perfect indoor semi-physical simulation experiment platform is established. Before the experiment, the geometric similarity and Froude similarity are used to simulate the main factors such as motion excitation, model tank, sensor position and experimental time. The reduction of the experimental results of sloshing load is also based on the Froude similarity, especially under the long-time excitation, the mathematical statistical method is introduced to deal with the peak value of the sloshing shock pressure. The scale effect between the model experiment and the prototype experiment is studied from the probability distribution of the pressure peak surpassing at the same position in the three scale tanks. In this study, 20% low load liquid rate and 80% high load liquid rate were used as two typical liquid loading conditions, and three scale tanks were subjected to a single wave shock at the resonance frequency of free liquid level, respectively. The scale experiment of sloshing impact under the action of long time rolling and rolling regular excitation. In this paper, the scale effect between the sloshing model experiment and the prototype experiment is studied by comparing and analyzing the probability distribution of the peak value of sloshing impact pressure of three scale tanks at the same position and combining with the corresponding flow pattern. The results show that when the gas interception occurs in the same position of the model and the prototype tank, the sloshing load obtained from the model experiment at this position is reduced to the prototype according to the Froude similarity. The deviation between the results of the model experiment and the prototype experiment will be reduced when the same position of the above two tanks is impacted by the gas-liquid mixed fluid and the results of the reduction of the model experiment and the measured results of the prototype experiment will be reduced. Only when both of them are impacted by incompressible pure liquid can the results of sloshing shock pressure after reduction from the model experiment reflect the measured results of the prototype experiment relatively. Considering that many special physical phenomena in the prototype tank sloshing can not be reproduced in the small scale model tank, large scale model experiments should be carried out as far as possible to study and evaluate the sloshing impact mechanism in the prototype tank.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE97

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