【作者】 王刚；

【导师】 刘少军；

【作者基本信息】 中南大学 ， 机械设计及理论， 2009， 博士

【摘要】 陆地上矿物资源的逐渐枯竭成为进行强有力海洋采矿研究的重要动机。在复杂海洋环境因素影响下将深海多金属结核连续、高效地采集并输送到海面采矿船上,同时要求开采系统具有高度可靠性和商业应用价值,是目前深海采矿面临的主要研究课题之一。管道提升式深海采矿系统是目前被国际广泛认可的典型深海多金属结核开采系统。自20世纪70年代,国际上各研究机构对这种采矿系统开展了大量的研究与海洋试验。中国深海多金属结核开采1000m海试系统亦采用集矿机与管道提升相结合的采矿方式,其扬矿系统是由扬矿硬管、扬矿泵、中间仓、柔性软管等多体组合的复杂长管线系统。在海洋采矿作业过程中,扬矿管线系统既受到包括海洋环境载荷在内的各种复杂外部载荷作用,又受到海面采矿船和海底集矿机作业运动的影响,因此无论是在布放回收还是在拖航作业过程中,其运动学和动力学特性都十分复杂。作者结合国家深海技术发展项目相关课题,采用有限元法对深海采矿扬矿管线系统作业过程进行数值模拟,研究管线空间构形和动态特性。主要研究内容如下:1.多体组合的深海采矿扬矿管线系统各部分主体结构之间力学耦合,根据中国深海采矿1000m海试系统总体方案和作业规划,针对扬矿系统各部分的结构特点、联接方式和作业条件,研究多体组合的扬矿管线系统在复杂外部载荷和作业联动作用下的力学建模。柔性复合软管作为扬矿管线系统的重要组成部分,其建模方法对整体扬矿系统作业联动分析的计算效率和精度影响很大。针对柔性复合软管抗拉刚度大,抗弯刚度小的宏观特性,提出了基于空间管梁有限元模型的单元耦合建模方法,建立了包括扬矿硬管、柔性软管、中间仓及扬矿泵等多体组合的扬矿管线系统有限元模型,为整体扬矿管线系统布放回收和拖航作业过程动力学分析提供了一种较精确的力学分析模型。2.扬矿管线有限元模型的外部载荷包括重力、浮力、海洋液动力、内外流体压力、内部流体运动产生的摩擦力、泵工作产生的轴向力和扭矩、软管的集中吊挂浮力等,在整体作业联动过程分析中,还包括采矿船和集矿机的运动载荷,以及布放回收作业中管线的运动载荷。扬矿管在海洋中受到波浪和海流联合作用的液动力载荷是扬矿管线主要的环境载荷,在海洋工程结构中属小直径管柱的流体动力问题。作者基于Morison公式研究了波浪与海流联合作用下扬矿管液动力载荷计算方法,同时给出了在大型低噪声循环水槽中进行的1000m海试系统中带附管扬矿管的流体动力系数试验方法和测定结果。3.在变形过程中伴随有大位移和有限旋转的空间管梁结构的几何非线性有限元分析方法有全拉格朗日法(TL),更新拉格朗日法(UL)和随体旋转法(CR)等。研究分析了拉格朗日法与随体旋转法各自的特点,给出了Rankin等推导的随体旋转法求解原理,并选用该方法求解扬矿管线的几何非线性问题。4.基于多体组合的扬矿管线有限元模型,采用静态分析方法对软管的空间构形进行研究,为扬矿管线系统布放回收和拖航作业过程动态分析提供基本参数。在软管空间构形的影响因素中,软管集中吊挂浮力配置方式对其水下空间构形的影响很大。在综合考虑软管空间构形、软管下端对集矿机作用力、软管下端偏转角度等多种因素基础上,研究了较优的软管集中吊挂浮力配置方案,包括浮力大小、配置比例、浮力体吊挂位置等。5.在布放回收作业过程中扬矿管线系统的结构形态和力学特性发生着快速变化,开展了扬矿管线布放回收过程数值模拟的探索性研究。针对布放过程中集矿机着底后管线系统的动态特性分析,建立了相应的有限元初始化模型,并对不同运动参数下布放作业中的管线形态和动态特性进行瞬态动力学分析。研究发现:较低的管线布放速度可以明显改善系统的动态特性;某些布放方式可能导致软管产生堆积缠绕现象,对此论文提出了相应的避免措施;管线回收作业的数值模拟过程基本上是布放作业过程模拟的逆过程,其动力学特性亦具有可比性。6.对多种运动参数下的扬矿管线作业联动特性和3种典型连续轨迹的拖航作业模式进行了动力学分析,实现了扬矿管线系统在稳态载荷、瞬态载荷和简谐载荷组合作用下时程变化的位移、作用力及应力的求解。研究表明:拖航速度越高,扬矿硬管偏转角度和中间仓的横向偏移越大,软管马鞍型形态畸变程度也相应增大;在低于0.5m/s速度下拖航,中间仓的拖曳轨迹与采矿船运动轨迹基本一致,系统的跟随性较好。7.由于海试系统的软管布放长度会根据实际水深适当调整,且中间仓距海底高度随海底地形变化,因此以中间仓为中心,建立了集矿机动态安全域。将软管布放长度和中间仓距海底高度在其变化值范围内离散化,并根据有限元分析结果,建立了集矿机动态安全域参数实时查询表,可供作业监控系统实时调用。8.为了验证扬矿管线建模方法的正确性,采用一个与1000m海试扬矿管线系统特征相似的拖曳水池实验模型,根据相同的管线建模方法建立了实验系统的有限元模型。选择有代表性的有流试验和无流试验两种实验测试结果与计算结果作比较,应力计算结果与实验测量结果相吻合。上述研究结果为深海多金属结核1000m海试开采系统的设计及其作业规化提供了基本参数和理论依据,同时研究方法为类似海洋工程长管线作业系统的研究提供了思路。更多还原

【Abstract】 The gradual exhausting of mineral resources in land store becomes an important motive which promotes more and more powerful research on ocean mining. It is main research topic of the deep ocean mining that efficiently collecting and transporting system of poly-metallic nodule from the sea floor to surface mining vessel is needed under complicated influence of the ocean environment, in the meantime which has high reliability and commercial applied value. The collector-pipe mining system as a typical commercial mining system for deep ocean poly-metallic nodule is extensively accepted by the nations currently. From the 70’s in 20 centuries, many technology research and ocean experiments on such mining system had been carried out by many international research organizations or some nations. Collector-pipe lift mining system is also adopted in Chinese 1000m sea trial project of mining system for deep ocean poly-metallic nodule, which is a long multibody pipeline system consists of lifting steel pipe, pump, buffer station, flexible hose, etc.During the ocean mining process, lifting pipeline system bears complex coupled external loads such as hydrodynamic loads of ocean environment, and is also affected by the motions of surface mining vessel and submarine collector. Therefore, the kinematic and dynamic responses of lifting pipeline system are very complex not only in the launch and retrieval operation process but also in towing mining process. Numerical simulation on space configuration and dynamic characteristic of lifting pipeline system in linkage operations for deep ocean mining was carried out by geometric nonlinear finite element method (FEM) in this thesis, as a part of national project of deep ocean technology research & development. The main contents are as follows:1. There are couple effects of mechanics on each part of the multibody lifting pipeline in deep ocean mining. According to total system design and operating plan of lifting pipe system for 1000m sea trial project, the modeling methods of multibody lifting pipeline system were studied in this thesis, based on the structure characteristic, connection modes, operation condition. Especially, the flexible hose is an important part of lifting pipeline; its modeling method influences the calculation efficiency and precision of integral pipeline analysis of deep ocean mining process greatly. A modeling method of element couple was put forward based on space beam model of finite element model to simulate the macrostructure characteristic of flexible hose, which tensile rigidity was large and bending stiffness was small relatively. The integral system model of multibody pipeline system was established, which consists of lifting steel pipe, flexible hose, buffer station, pump, etc. A kind of mechanics model of the integral lifting pipeline was achieved for the dynamic analysis of the launch, retrieval and towing process in deep ocean mining. 2. In FEM model of lifting pipeline, the following external loads are considered: gravity, buoyancy, hydrodynamic forces, internal and external fluid pressures, torsional moment and axial force induced by pump working, friction induced by interal flow, concentrated suspension buoyancy on the flexible hose, etc. For the dynamic analysis of working motion of lifting pipeline, the motion loads of collector and ship, and the pipeline’s motion loads during the launch and retrieval operation, are also considered. The pipeline’s hydrodynamic force induced by ocean wave and current is the main environment loads of lifting pipeline. It belongs to the hydrodynamic problem of pipe or cylinder with small diameter in ocean engineering. The calculation method of pipeline’s hydrodynamic force was described based on the Morison’s equation in this thesis. To evaluate the drag coefficients of lifting pipe with some adjunctive pipes used in 1000m sea trial, the hydrodynamic experiments had been done in the large low-noise circulation tank. The experimental methods and results of the drag coefficients were given.3. There are several important approaches of nonlinear finite element method to solve geometric nonlinear problem of spatial pipe & beam structures, which includes deformation process with large displacements and finite rotations, such as Total Largrangian (TL) formulation, Updated Largrangian (UL) formulation and Corotation (CR) formulation. Comparing the advantages of these approaches, the principle of Corotation formulation introduced by Rankin was described. The Corotation formulation was adopted to solve nonlinear problems of lifting pipeline.4. In order to obtain the basic parameters of lifting pipeline system for the dynamic analysis of launch and retrieval operation and towing mining, the configuration of lifting pipeline in space was analyzed by static analysis method based on multibody pipeline FEM model. Among many influencing factors of flexible hose configuration, the concentrated suspension buoyancy on hose affects its configuration greatly. Based on combinational analysis of configuration in space, action force on collector and deflection angle of flexible hose bottom, optimized arrangement of concentrated suspension buoyancy on hose was presented, including buoyancy value, arrangement proportion and suspension position of buoyancy balls.5. During the launch and retrieval operation, the configuration, shape and mechanical characteristic of lifting pipeline system transform quickly and greatly. The exploratory research of numerical simulation for launch and retrieval towing process was carried out in this thesis. According to the dynamic analysis of pipeline for launch operation process affter collector landing the sea floor, the initial FEM model for transient dynamic analysis was established. The pipeline shape and dynamic characteristic during launch and retrieval process under various motions parameters were analyzed by transient dynamic method. The research indicates: lower velocity of pipeline’s launch improves the dynamic characteristic of flexible hose; the flexible hose is easily piled and enwind at some launch operation mode, and the advice to avoid such situation was offered; the numerical simulation of pipeline’s retrieval is the inverse process of launch operation approximately, kinematics and dynamics characteristic of retrieval is comparable with that of launch.6. Based on the FEM model of integral lifting pipeline, transient dynamic characteristic of various linkage motions and 3 typical towing mining modes under continuous tracks was analyzed. Considering the combination effects of steady loads, transient loads and simple periodic motion, the dynamic response of pipeline in time domain was calculated, such as displacement, action force, stress, etc. The results of dynamic analysis indicate: the deflection angle of steel pipe and lateral deflecting of buffer increase with augmentation of towing velocity, as well as the deformation of hose’s saddle shape; when towing velocity is less than 0.5m/s, the towing track of buffer is coincided with the setting route of ship on the whole and the following ability of pipeline system is also kept well.7. The launch length of flexible hose will be determined according to the water depth in sea trial, and the distance between buffer and sea floor varies with terrain changing. Therefore, safety domain for collector’s motions was designed, in which the buffer was the center of coordinate system. The launch length of flexible hose and the distance between buffer and sea floor are discretized in range. Based on the analysis by FEM, the real-time inquiry table of safety domain for collector’s motions was established for real-time monitor system in ocean mining.8. An experimental model in towing water tank with the similar characters of pipeline system in 1000m sea trial was designed to verify the FEM modeling method. And the FEM model of experiment system was established by modeling methods introduced by this thesis. Measuring records of typical hydrodynamic experiment and anhydrous experiment were obtained. The simulation results of pipe stress were coincided with the experimental results by comparison.Conclusions of research in this thesis provided basic characteristic parameters and theory reference for the design of mining system and operation planning of 1000m sea trial. And its methods can also provide references for mechanics research of long pipeline system in ocean engineering.更多还原