| Popis: |
Ice sheets in the Arctic contain well-ordered accumulations of ancient ice that fell as snow years to millions of years ago. Ice-core data have become central to our understanding of climate change in the past, and to assessments of possible future climate change. Hot-water ice-coring drills are often used to recover ice-core samples from a desirable depth in conjunction with a full-scaled hot-water drilling systems. However, the recovered cores had the varying quality. In hot-water ice-coring drilling, many small nozzles are used to spray water out and melt out a cylindrical ice. Parameters of the nozzle, which mainly includes angle, diameter and quantity, are the most critical part of the drilling system. To improve the ice-core quality in hot-water ice-coring drilling, the influence mechanism of annular hot-water jets formed by nozzle with different parameters on ice-core quality was studied. Heat transfer law of annular jet on the ice-core was studied using the numerical simulation. Totally nine kinds of nozzle with different parameters were designed by using the orthogonal design method and the corresponding calculation domain model of ice was established. The ANSYS FLUENT software was used to analyze the heat flow field, variation trend of heat transfer to the ice-core with different nozzle parameters was researched. The result indicated that the heat transfer of hot water to ice core increased with the larger nozzle diameter while decreasing with the increase of nozzle quantity and nozzle angle. The result can help to give a reference for the design of hot-water ice-coring drill head used in the polar regions. |
