Numerical study on inlet operational conditions in the outside vapor deposition process

Operational conditions at inlets of outside vapor deposition (OVD) play an important role in production yields and quality of optical fiber preforms. This work aims to numerically investigate the inner states and SiO₂ deposition performance of OVD under different inlet operational conditions. This is based on a recently developed Eulerian-Eulerian multiphase OVD process model which is extended to consider the SiO₂ particle nucleation and growth. The effects of inlet operational conditions are investigated in terms of the flow rate of SiCl₄/O₂-H₂-O₂, the mass fraction ratio of SiCl₄/O₂ as well as different carrier gases (H₂, N₂ or O₂). The simulations show that there exists an optimal SiCl₄/O₂ flow rate to yield the maximum deposition efficiency. While the deposition efficiency decreases with increasing either O₂ or H₂ flow rate. The reduction of the mass fraction ratio of SiCl₄/O₂ leads to a dramatic decline in deposition efficiency, whereas the averaged particle diameter of SiO₂ on the target is insensitive to the variations of the SiCl₄/O₂ mass fraction ratio. In addition, using H₂ or N₂ as carrier gas instead of O₂ leads to a nonuniform SiO₂ distribution and a significant decline in SiO₂ particle sizes on the target. The results reveal that selecting inlet operational conditions is an effective tool to adjust deposition efficiency and control the quality of SiO₂ particles on the target.