Thermal optimization of induction-heated pulling-down furnace for quartz glass rod fabrication

Quartz glass rods are widely used in modern industries due to their remarkable properties. In this paper, a systematic study is conducted to analyze the induction-heated pulling-down furnace for quartz glass rod fabrication using simulation methods. The softening zone of quartz glass rod plays a significant role in its quality, which needs proper controlling. Numerical simulations are performed to explore the influences of furnace design, including coil pitch, coil position, length and thickness of the afterheater, and thickness of the bottom insulation, on the softening zone range. In quantitative analysis, the softening zone is described using the length parameters l1 and l2 and the relative length lr. Single-factor analysis reveals that under current study conditions, increasing coil pitch or afterheater thickness is beneficial to the softening zone, while the other three factors exert non-monotonic effects. To identify optimal conditions for quartz glass rod fabrication, an orthogonal test design is employed with a comprehensive consideration of the five aforementioned factors. Based on the results, the influence of afterheater thickness on the softening zone is the most significant, and coil position is the least. An optimal furnace design is proposed that could provide useful insight into the fabrication of high-quality quartz glass rods.