海上浮式油水置换储油舱内分层液体晃荡及传热耦合机理研究

Oil exploitation in deepwater is an inevitable trend in the development of the world petroleum industry. As a result, new floating drilling production storage and offloading units such as FDPSO and SDPSO have been invented. In the marine environment, stratified liquid sloshing and heat transfer simultaneously appear in the oil-water displacement storage tank located in the lower part of the FDPSO and SDPSO platforms, which have adverse effects on the stability, safety and economic efficiency of the platforms. In addition, significant mutual coupling effects exist between the liquid sloshing and heat transfer, however, mechanisms of the coupling have not been fully studied yet. Based on the previous studies, this project aims to establish a theoretical model that accurately describes the nonlinear sloshing and unsteady heat transfer in the floating oil-water displacement storage tank, and propose a three-dimensional numerical model that effectively simulate the breaking and instability of the liquid-liquid interface as well as the turbulent natural convection. An experimental system of the stratified liquid sloshing and heat transfer will be developed to conduct laboratory experiments to verify the accuracy and stability of the numerical model. By combining the numerical simulation method with the physical model tests, a systematic investigation on liquid sloshing and heat transfer in the offshore floating oil-water displacement storage tank is carried out to reveal the mechanisms of different types of interfacial waves and the interfacial instability, the local characteristics of the heat transfer at the liquid-liquid interface, and the coupling mechanisms of the stratified liquid sloshing and heat transfer. The present study has important scientific significance and practical application value. A better understanding of the characteristics of the stratified liquid sloshing and heat transfer in the floating oil-water displacement storage tank will be obtained, which provides a scientific basis and reference to actual engineering design and economic operation of floating or subsea oil-water displacement storage tank.

走向深水是世界石油工业发展的必然趋势，FDPSO和SDPSO等新型浮式钻井生产储卸油装置应运而生。在海洋环境中，位于FDPSO和SDPSO平台下部的油水置换储油舱内会同时发生油水分层液体晃荡和传热现象，对平台的稳定性、安全性和经济性产生不利影响。同时，晃荡与传热两种现象之间存在显著的相互耦合作用，但目前国内外还未对其耦合机理展开研究。本项目拟在前期研究基础上，建立可准确描述浮式油水置换储油舱非线性晃荡与非稳态传热的理论模型，开发能有效模拟液液界面剧烈破碎与湍流自然对流的三维数值模型，设计并搭建液体晃荡传热试验装置。在此基础上，采用数值模拟与模型试验相结合的方法，系统开展海上浮式油水置换储油舱晃荡与传热研究，获得液液界面内波的运动特性，掌握液液界面和舱壁附近热量传递的局部特性，揭示晃荡与传热的耦合机理。研究工作可以为国内外浮式和海底油水置换储油舱的实际工程设计以及安全经济运行提供科学依据。

海上浮式油水置换储油舱内分层液体晃荡及传热耦合机理研究是应海洋工程界对深海油田开发技术的迫切需求而提出的课题。本项目首先基于流体力学理论和传热学理论建立海上浮式油水置换储油舱物理模型，进而建立海上浮式油水置换储油舱非线性晃荡与非稳态传热数学模型，并在此基础上，开发分层液体晃荡与传热三维数值模型。针对我国南海深水边际油气田开发需要和南海原油特性，设计了浮式油水置换储油舱分层液体晃荡与传热试验装置与在线监测系统。试验装置主要由浮式油水置换储油舱模型、水池、中控系统、原油储罐、原油加热器、注油泵、卸油泵、流量计、制氮机和晃荡装置组成。在线监测系统主要包括置换水中含油在线测量系统、温度测量系统、油水界面位置在线监测系统和水下摄像系统。最后采用数值模拟与模型试验相结合的方法系统研究海上浮式油水置换储油舱内分层液体晃荡与传热特性。对于晃荡问题，详细讨论了外部激励频率和激励幅值对油水界面运动幅度的影响，分析了主导油水界面运动的关键因素，重点研究了外部激励频率接近或者等于系统固有频率时油水界面的晃荡情况，此外，提出了浮式油水置换储油舱内部减晃优化方案，研究了不同宽度的垂向隔板对油水界面晃荡幅度、油水界面形状和油水速度幅值的影响。对于传热问题，分析了不同时刻下油水界面的形状以及舱壁和界面附近的速度场、温度场，获得油水界面和舱壁处热量传递的局部特性，揭示自然对流流场的产生、发展、衰退及消失机理，掌握自然对流流动和油水界面运动对储油舱传热特性的影响规律。此外，还进行了部分研究计划中未提及的内容，增加了浮式油水置换储油舱分层液体传质特性研究，得到了储油舱运动、原油物性和环境温度对置换水中含油的影响规律。上述研究可形成系统的分层液体晃荡传热传质研究方法，掌握储油舱内油水界面的运动规律，揭示储油舱内热油与舱内外海水的传热传质机理，为海上浮式油水置换储油舱设计提供理论及数值等基础性技术参考。