月壤钻进取心过程钻具热特性研究

我国探月三期工程采用回转冲击钻对月表月壤进行预计深度为2米的采样作业,采样过程中钻头由于钻削产生的切削热完全由钻具本身导热传递。由于月球的超高真空度以及苛刻的温度环境,导热效率相较于地面钻探低。同时,由于钻进工况的未知性,钻具可能会形成局部高温区域,这会使钻具的整体性能降低,尤其对钻具的取心性能影响最大。通过EDEM软件,建立不同形状及颗粒大小的月壤颗粒微元模型,组成月壤仿真模型,基于高温小颗粒群法,开展钻进过程月壤热特性仿真研究,研究温升颗粒的分布规律,并根据这一分布规律建立温升颗粒数量与温升之间的关系式。另外,在模拟月壤钻进实验中,在原有的取芯钻具上补充若干温度测量点,通过光纤光栅传感技术,开展钻具热特性实验研究,获得了钻头不同位置区域的温升规律,以及回转转速、进给速率对钻具温度的影响规律。温升颗粒数量模型以及常规热特性实验均能实现钻具温升情况的预测,为后续钻具在拟实月球环境及恶劣工况下的热安全性研究提供依据。

Study on thermal characteristics of drilling tools during lunar soil drilling coring process

Aiming to penetrate approximately two meters below the lunar surface, a rotary-percussive sampling drill is used for the lunar exploration project in China. The cutting heat generated by drilling is completely conducted by the drilling tool during the drilling process. Due to the ultra-high vacuum and harsh temperature environment of the Moon, the efficiency of the conduction is much lower than that of regular drilling operation on the Earth. As the drilling condition is unknown, the high temperature area in certain part of the drilling tool may be formed, which will reduce the overall performance of the drilling tool, particularly the coring performance of the drilling tool. Through the EDEM software, the lunar soil particle microelement model with different shapes and sizes were established to form the lunar soil simulation model. The thermal characteristics of the lunar soil in the drilling process were simulated based on the high temperature small particle cluster method in order to reveal the distribution rule of different temperature rise particle. Based on the distribution rule, a mathematical expression between the temperature rise particle number and temperature rise was built. In addition, in the simulated lunar drilling experiment, several temperature measurement points were supplemented on the original drilling tool by the fiber grating sensor technology. The thermal characteristic experiments of drilling tool were completed to obtain the temperature rise rule in different locations of drill bit and the influence of rotary speed or penetrating velocity on the temperature of drilling tool. Both the temperature rise particle number model and the traditional thermal characteristic experiment can predict the temperature rise of the drilling tool, which provides a basis for the thermal safety on the lunar simulation environment or extreme drilling condition.