A Study of the Transport Processes and of the Generation of Defect Centers in Optical Fiber Drawing

该项目针对光纤拉伸过程，通过减少过程中产生的缺陷和不规则性来提高光纤的质量，并通过提高冷却速度来提高拉伸速度。与光纤拉伸有关的热传递和物质流动过程对所获得的光纤质量和最佳拉伸速度起着非常重要的作用。将进行详细的数值和实验研究，以调查传输现象对纤维质量的影响，特别是对缺陷产生的影响，以及提高传热率以提高拉伸速度和减少冷却纤维所需的距离到所需的温度水平。材料的温度分布、颈部以下区域的表面轮廓、传热率和过程中的材料分布将采用数值方法确定，所考虑的轴对称问题采用有限体积方法，并采用实验结果来验证模型和数值方案。所获得的详细结果有望有助于更好地理解所涉及的基本传输过程，并为改进现有程序提供科学依据，对高速拉伸、低成本纤维制造、拉伸诱导缺陷产生、超低损耗纤维开发等工艺产生影响。非氧化玻璃拉拔过程中热致相分离结晶、残余应力的产生等。

The project is directed at the optical fiber drawing process in an effort to improve the quality of the fiber, by reducing the defects and irregularities generated in the process, and to increase the draw speed, by enhancing the cooling rate. The thermal transport and material flow processes associated with the drawing of optical fiber play a very important role in determining the quality of the fiber obtained and the optimum draw speed. A detailed numerical and experimental study will be performed to investigate the effect of the transport phenomena on the quality of the fiber, particularly on defect generation, and the enhancement of the heat transfer rate to increase draw speeds and reduce distances needed for cooling the fiber to a desired temperature level. The temperature distribution in the material, the surface profile in the neck down region, heat transfer rates and material distribution in the process are to be determined numerically, using the finite volume approach for the axisymmetric problem under consideration and employing the experimental results for the validation of the model and of the numerical scheme. The detailed results obtained are expected to contribute to a better understanding of the basic transport processes involved and to provide a scientific basis for improving existing procedures, impacting on processes such as high speed drawing, low cost of fiber fabrication, draw induced defect generation, ultra low loss fiber development, thermally induced phase separation and crystallization during drawing of non-oxide glasses, residual stress generation, etc.