【作者】 刘杰；

【导师】 许栋； 及春宁； 夏建新； 张明进；

【作者基本信息】 天津大学 ， 土木水利， 2023， 硕士

【摘要】 深海采矿是近年来海洋工程研究的热点。海底拥有丰富的矿产资源,尤其是多金属结核,多金属结核含有锰、铁、镍、钴、铜等几十种元素,且海底储量大,拥有巨大的商业开发价值。海底采矿主要采集方式包括水力式、机械式和水力机械混合式采集等,其中水力式采集具有机械部件固定、可靠性好、结构简单等优点,是目前最具发展前景的采集方式之一。水力采集器通过集矿头喷嘴生成高速淹没射流,冲击海床表面并剥离多金属结核颗粒,进一步通过水流抽吸收集颗粒。水力采集过程中,海床表面的多金属结核颗粒能否在水流作用下,从土体中剥离起动并随水流进入采集器,是工艺设计的关键。集矿头周围的三维水流结构是分析颗粒运动特性的力学基础。此外,集矿头的结构及尺寸设计是影响采集效率的关键因素。本文首先利用CFD(计算流体力学)方法对水力射流采矿集矿头周围流场结构特性进行了探究,然后利用CFD-DEM(计算流体力学-离散元)耦合方法研究了集矿头不同结构参数对水力采矿的影响,在水力采矿机制以及集矿头结构参数优化上得出了有价值的结论。主要结论如下:水力式采矿集矿头周围流场大致分为五个区域:淹没射流区、冲击区、壁面射流区、汇合区和上升区,壁面射流区流体对海床的水流剪切力是结核颗粒剥离起动的重要动力来源。对于底面壁面剪切力,由滞点向内侧快速增大,在两个滞点的中间位置达到最大值。最大床面剪切力随喷嘴射流速度呈线性增长趋势。对于采集能效,随着射流功率的增加,结核采集能效逐渐减小;随着结核颗粒粒径的增加,采集能效整体呈幂级减小。集矿头结构参数对水力采矿影响:随着离地高度的增加,结核采集率下降,采集效率降低,对采集器下方海底环境扰动强度减小;随着射流速度的增加,结核采集效率总体呈先增加后减少的趋势,对采集器下方环境扰动强度先增加后减少;随着射流角度的增加,结核采集效率增加,对采集器下方海底环境扰动强度增加。总体来讲,本文采用的采集器优化结果为:离地高度为5cm左右、射流速度为10 m/s左右、射流角度取70°～80°时,水力采矿采集效果较好,采集率可以达到100%,且在0.25s内可以将全部结核采集完毕。更多还原

【Abstract】 Deep sea mining is a hot topic in recent years.The seabed is rich in mineral resources,especially polymetallic nodules,which contain dozens of elements such as manganese,iron,nickel,cobalt and copper,and the seabed reserves are large,with huge commercial development value.The main collection methods of seabed mining include hydraulic,mechanical and hydraulic-mechanical combined collection,among which hydraulic collection has the advantages of fixed mechanical parts,good reliability,simple structure and so on,and is one of the most promising collection methods at present.The hydraulic collector generates a high-speed submerged jet through the nozzle of the ore collecting head,impinges on the seabed surface and strips the polymetallic nodules,and further absorbs the particles through the water flow.In the process of hydraulic collection,whether the polymetallic nodules on the seabed surface can be peeled off from the soil,start up and enter the collector with the water flow is key to the process design.The three-dimensional flow structure around the collecting head is the mechanical basis for analyzing the movement characteristics of particles.In addition,the structure and size design of ore collecting head are key factors affecting the collection efficiency.In this paper,CFD(computational fluid dynamics)method is used to explore the flow field structure characteristics around the mining head of hydraulic jet mining,and then the coupling method of CFD-DEM(computational fluid dynamics-discrete element)is used to study the influence of different structural parameters of the mining head on the hydraulic mining mechanism and the optimization of structural parameters of the mining head,valuable conclusions are drawn.The main conclusions are as follows:The flow field around the hydraulic mining collecting head can be roughly divided into five areas:submerged jet area,impact area,wall jet area,confluence area and rising area.The shear force of the fluid in the wall jet area on the seabed is an important power source for the stripping start of nodules.For the bottom wall shear force,it increases rapidly from the hysteresis point to the inside and reaches its maximum value in the middle of the two hysteresis points.The maximum bed shear force increases linearly with the jet velocity.As for the collection energy efficiency,with the increase of jet power,the collection energy efficiency of nodules decreases gradually.With the increase of tuberculosis particle size,the collection energy efficiency decreases in a power level.The influence of collecting head structural parameters on hydraulic mining:with the increase of the altitude above the ground,the collection rate of nodules decreases,the collection efficiency decreases,and the disturbance intensity of the seabed environment below the collector decreases.With the increase of jet velocity,the collection efficiency of nodules increases first and then decreases,and the environmental disturbance intensity under the collector increases first and then decreases.With the increase of jet Angle,the collection efficiency of nodules increases,and the disturbance intensity to the seabed environment below the collector increases.In general,the optimization results of the collector adopted in this paper are as follows:when the height above the ground is about 5cm,the jet velocity is about 10 m/s,and the jet Angle is 70°～80°,the hydraulic mining collection effect is better,the collection rate can reach 100%,and all nodles can be collected within 0.25s.更多还原