浅层电动机械钻具设计及其冰屑螺旋输送理论研究

发布时间：2018-08-12 10:54

【摘要】：冰盖冰川和高山冰川是富含古代气候信息和存储古气候重要信息的气候档案库。冰川变化是大气和海洋变化的敏感指标之一,对海平面上升、山区供水河流的水文、海洋的淡水平衡、自然灾害,甚至地球的形状和旋转等全球重要性进程具有重要影响。浅层冰心包含的信息可以实现重建气候变化循环,提高最古老冰心位置选择的准确性,研究冰盖内部的动力学特征与冰盖内应力、应变率的时空变化间的关系等等。本文对浅层冰心钻探方法以及目前广泛应用于浅层冰心钻探的电缆悬挂式电动机械钻具研究现状进行了详细的调研、分析。在此基础上,以提高冰屑输送效率为目标,通过回转螺旋输送理论和离散元数值模拟方法,确定了冰屑螺旋输送系统的最优设计参数。借鉴已有浅层电动机械钻具的设计理念,设计并研发了浅层电动机械螺旋钻具,通过室内和扩色色勒冰川野外试验,验证了冰屑螺旋输送系统及浅层电动机械螺旋钻具工作的可靠性,为进一步设计和优化浅层电动机械钻具结构参数,提高其冰屑输送效率和机械钻速,获取高质量冰心提供了重要借鉴。论文研究主要获得以下结论:1)通过回转螺旋输送理论对冰屑螺旋输送系统进行理论分析,确定了其输送效率的影响因素。设计了冰摩擦系数试验台,通过测量牵引冰样的拉力和冰样的重量,计算得出冰在不同温度下与不同材料间摩擦系数的数据库。针对不同材料组合,计算螺旋升角和回转速度与冰屑螺旋输送效率之间的关系。根据计算得出当外管内壁采用沟槽设计、内管和螺旋叶片选用聚四氟乙烯材料、转速为175 rpm、对应的螺旋升角为13.7°时,冰屑的输送效率最高,可达87%。利用多功能冰钻测试台对回转螺旋输送理论在冰屑螺旋输送系统中应用的可行性其进行验证。试验证明由常规回转螺旋输送理论计算所得的最优冰屑螺旋输送参数并不能有效输送冰屑。冰屑在螺旋叶片底部堵塞严重甚至压实成块,导致冰屑无法输送,最终钻进停止。常规回转螺旋理论并不能应用于冰屑螺旋输送系统的参数设计。2)利用散体颗粒物料分析方法-离散单元法对冰屑颗粒在螺旋输送系统中的输送情况进行了数值模拟。模拟结果表明,冰屑螺旋输送是一个非常复杂的过程,并对操作参数非常敏感。基于冰屑颗粒尺寸的假设,数值模拟可以得出:在低回转速度条件下,冰屑在近螺旋底端区域堆积。而当回转速度高于100 rpm时,冰屑的输送效率更高;颗粒的有序输送是提高输送效率和减少能量消耗的重要影响因素之一。在高回转速度下容易引起冰屑颗粒的无序运动,其原因可能是由于冰屑颗粒尺寸过小或重量太轻,螺旋叶片的搅拌作用大于输送作用引起的;电动机械钻具螺旋输送系统最优参数的选取,要综合考虑诸如冰层温度和所需驱动电机的可用性等多种因素。针对本文研究的限定条件,结合平均颗粒速度、平均纵向颗粒速度、质量流率、平均颗粒高度、单位质量颗粒的能耗平均值和比能六个不同输送特性的综合评价,有序和无序运动的临界值在100rpm左右对应的螺旋升角为35°-40°。3)设计和加工了测试版浅层电动机械钻具TestSEMA及其试验台,通过钻进天然冰样对测试版钻具和基于离散元法设计的最优冰屑输送系统进行测试和评价。实验结果表明在钻进过程中,冰屑在螺旋叶片上输送顺畅,没有任何卡堵现象,增大回转速度可明显加快冰屑上升的速度和高度。当Test SEMA稳定工作时机械钻速可达10.2 m/h,满足电动机械钻具的平均机械钻速要求,证明了冰屑螺旋输送系统的工作稳定性和可靠性。试验获得的冰孔光滑、冰心完整,但钻得的冰屑颗粒尺寸较小,表面能较高,在输送过程中容易发生团聚现象。TestSEMA钻具试验验证了离散元方法在冰屑螺旋输送系统中应用的可行性以及TestSEMA钻具和试验台(地表设备)设计的合理性,为设计和优化野外钻探用浅层电动机械螺旋钻具(SEMA)提供了重要参考。4)设计了包括SEMA钻具及其地表设备的浅层电动机械钻具。SEMA钻具在扩色色勒冰川上海拔为5600 m处共进行了55回次测试。钻进过程中,冰屑输送顺畅无阻,获得的冰心质量好,最大长度达1.1 m,钻具最大机械钻速可达18 m/h,平均机械钻速为10.8 m/h。SEMA钻具的野外测试验证了钻具设计的可行性和工作可靠性,进一步实地验证了离散元法设计冰屑螺旋输送系统的适用性。整个设备只需两人便可进行野外作业,便于运输、安装,拆卸和操作,可应用于高山冰川或冰盖冰川的取样任务。
[Abstract]:Ice sheet glaciers and alpine glaciers are climate archives rich in ancient climate information and important paleoclimate information. Glacier change is one of the sensitive indicators of atmospheric and oceanic changes. Glacier change is a process of global importance, such as sea level rise, hydrology of mountain water supply rivers, fresh water balance of oceans, natural disasters, and even the shape and rotation of the earth. The information contained in the shallow ice core can reconstruct the climate change cycle, improve the accuracy of choosing the location of the oldest ice core, study the relationship between the dynamic characteristics of the ice cap and the internal stress of the ice cap, the temporal and spatial variation of the strain rate and so on. Based on the investigation and analysis of the present situation of the cable suspended motor-driven drilling rig, the optimum design parameters of the screw conveying system for ice chips are determined by means of the rotary screw conveying theory and the discrete element numerical simulation method in order to improve the ice chips conveying efficiency. Designed and developed shallow electro-mechanical spiral drilling tools. The reliability of the screw conveying system and shallow electro-mechanical spiral drilling tools is verified by indoor and field tests on Xerox glacier. The structural parameters of shallow electro-mechanical drilling tools are further designed and optimized to improve the efficiency of ice scrap conveying and the rate of mechanical drilling. The main conclusions of this paper are as follows: 1) Through theoretical analysis of the screw conveying system, the factors affecting the conveying efficiency of the screw conveying system are determined. An ice friction coefficient test bench is designed, and the ice is calculated by measuring the pulling force of the ice sample and the weight of the ice sample. The relationship between screw angle and rotation speed and screw conveying efficiency of ice chips is calculated for different material combinations. According to the calculation, when the inner wall of the outer tube is designed with grooves, the inner tube and the screw blade are made of PTFE, and the rotational speed is 175 rpm, the corresponding screw lift is obtained. When the angle is 13.7 degrees, the conveying efficiency of ice chips is the highest, up to 87%. The feasibility of applying the rotary screw conveying theory to the screw conveying system of ice chips is verified by using the multi-functional ice drill test rig. The experiment proves that the optimal screw conveying parameters calculated by the conventional rotary screw conveying theory can not convey ice chips effectively. The conventional rotary screw theory can not be applied to the parameter design of the screw conveying system. 2) The transport of ice particles in the screw conveying system was numerically analyzed by using the discrete element method (DEM) and the method of granular material analysis. The simulation results show that the screw conveying of ice debris is a very complicated process and sensitive to the operation parameters. Based on the assumption of the size of ice debris particles, the numerical simulation can be concluded as follows: under the condition of low rotational velocity, the ice debris accumulates near the bottom of the screw. Orderly transport of particles is one of the important factors to improve the transport efficiency and reduce energy consumption.It is easy to cause disorderly movement of ice particles at high rotational speed.The reason may be that the size or weight of ice particles is too small or too light,and the agitation effect of screw blades is greater than that of conveying. The selection of the optimal parameters of the system should take into account such factors as the ice temperature and the availability of the required driving motor and so on. Comprehensive evaluation shows that the critical value of ordered and disordered motion is about 100 RPM corresponding to the spiral angle of 35 [-40]. TestSEMA and its test bench are designed and manufactured for the shallow electromechanical drilling tool of test plate. The test rig and the optimal ice transport system based on discrete element method are tested and evaluated by drilling natural ice samples. The results show that during the drilling process, the chips are conveyed smoothly on the spiral blade without any blocking phenomenon, and the increase of rotation speed can obviously accelerate the rising speed and height of the chips. The test results show that the ice holes are smooth and the ice cores are intact, but the ice grains drilled are small and the surface energy is high, which makes it easy to agglomerate in the conveying process. The rationality of the design provides an important reference for the design and optimization of the shallow electromechanical auger drill (SEMA) for field drilling. 4. The shallow electromechanical drill, including the SEMA drill and its surface equipment, was designed. The SEMA drill was tested 55 times at the altitude of 5600 m in the Pan-Seller Glacier. The maximum length of the ice core is 1.1 m, the maximum penetration rate of the drill tool is 18 m/h and the average penetration rate is 10.8 m/h. The field test of the SEMA drill tool verifies the feasibility and reliability of the design of the drill tool, and further verifies the applicability of the discrete element method in the design of the screw conveying system. It is easy to transport, install, disassemble and operate. It can be used in the sampling of alpine glaciers or ice sheet glaciers.
【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P634.4

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