| 摘要 |
PROBLEM TO BE SOLVED: To provide a porous preform manufacturing apparatus to suppress gas stream turbulence in a reaction chamber at the initial stage of deposition, and to prevent the porous preform from breaking, in a large-sized porous preform manufacturing apparatus by a VAD method.SOLUTION: In a porous glass preform manufacturing apparatus, glass raw material, combustible gas and combustion-assisting gas are supplied to a burner, the glass raw material is hydrolyzed in an oxygen and hydrogen flame to generate glass fine particles, and the generated glass fine particles are deposited on a starting member under rotating and being pulled up, to manufacture a porous glass preform. A reaction chamber comprises a deposition room in which glass fine particle deposition is implemented, and a cylinder section to house a deposited porous glass preform above the deposition room. A gas-stream-stabilizing member constituted by combining a cylinder of an outer diameter of Dand discs of an outer diameter of Dis positioned above the starting member located in the reaction chamber. Providing the inner diameter of the cylinder section as D, the outer diameter of the gas-stream-stabilizing member, D, satisfies the relationship of D/D≥0.8. |
