Analysis of helium/argon purge gas flows in industrial scale glass fiber drawing system

The high-speed glass fiber drawing in a silica-based optical fiber mass manufacturing system is numerically modeled and simulated on draw furnace model to systematically examine how the use of highly expensive helium in purge gas supply greatly improves the process stability and purging of contamination particles. The numerical results found the undesirable purge gas flow phenomena such as large buoyancy driven flow recirculations and periodic or quasi-chaotic flow patterns around the preform neck-down formation, when the purge gas is made of argon only. The effects of helium contents and flowrates in purge gas supply of argon/helium mixture are extensively investigated on neck-down formation and purge gas flow patterns. In contrast, it is shown that the helium usage effectively eliminates the flow recirculation and flow instability. The optimization of purge gas supply condition is also discussed in an effort to reduce helium consumption.