| 摘要 |
The present invention provides a burner for manufacturing a porous glass preform, which is provided with a combustible gas injection port involving a plurality of small-diameter supporting gas injection ports such that the injection ports of the same row have the equal focal distance, the small-diameter supporting gas injection ports being arranged on the outside of a glass source gas injection port in the center so as to be in a row or in a plurality of rows and concentric with the glass source gas injection port, wherein the small-diameter supporting gas injection ports are bent toward the burner center axis at predetermined positions from the tip ends of the small-diameter supporting gas injection ports so that the focal points of the small-diameter supporting gas injection ports of the same row agree with each other, and the bend angle of the small-diameter supporting gas injection port row closest to the glass source gas injection port in the center of the small-diameter supporting gas injection port rows arranged in the plurality of rows is at most 5 degrees with respect to the burner center axis.
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