VAD Cladding Burner Gas Flow Control for Melt Residue

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Solution Overview

Problem

The existing VAD method for producing optical fiber preforms results in melt residue when increasing the flow rate of combustible gas to adjust the refractive index distribution, leading to localized high-density glass fine particle regions during sintering and transparentization.

Innovation Solution

A method using a cladding deposition burner with five concentrically arranged cylindrical tubes and a ring-shaped group of small-diameter nozzles, where specific gases are flowed through different regions to achieve a linear velocity ratio of combustion supporting gas to combustible gas between 2.2 and 4.3, optimizing the deposition process to reduce melt residue.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the flow rate of combustible gas is increased to adjust the refractive index distribution shape of the core portion, then the refractive index distribution can be adjusted, but a region having a high density of glass fine particles is formed locally, causing melt residue during sintering and transparentizing

Engineering Contradiction:

Improverefractive index distribution shapeVSAvoidmelt residue

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The burner is divided into multiple functional regions with five concentric cylindrical tubes, each delivering different gases (combustible gas, combustion supporting gas, air, inert gas) to create distinct flame zones. This segmentation allows independent control of combustion parameters in different radial regions, preventing localized high-density glass particle formation while maintaining refractive index distribution control

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different gas flow rates and compositions are applied to different radial regions of the burner. The combustion supporting gas flow rate in the third region is specifically controlled to create a linear velocity ratio of 2.2-4.3 relative to combustible gas, optimizing local combustion conditions to prevent melt residue while achieving the desired refractive index distribution shape

Inventive Principle:

Principle #3Local quality

2Productivity

If a multi-nozzle burner with concentrically arranged small-diameter nozzles is used to increase deposition efficiency of the cladding deposition burner, then productivity is improved, but the complexity of the burner structure increases

Engineering Contradiction:

Improvedeposition efficiencyVSAvoidburner structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The burner employs five concentric cylindrical tubes nested within each other, with smaller-diameter nozzles arranged concentrically within larger tubes. This nested configuration allows multiple gas delivery functions to be integrated in a compact structure, increasing deposition efficiency while managing structural complexity through systematic nesting rather than random arrangement

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The cladding deposition burner is designed to perform multiple functions simultaneously: depositing cladding material, controlling refractive index distribution, and preventing melt residue formation. The multi-region gas delivery system enables these diverse functions to be achieved through a single integrated burner structure rather than requiring separate devices

Inventive Principle:

Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach effectively produces transparent glass rods with minimal melt residue defects and high silicon dioxide deposition efficiency, ensuring the quality of optical fiber preforms.

Implementation Method 1

a method for producing a glass fine particle deposit by a VAD method using a core deposition burner and a cladding deposition burner

Methodology Applied

Scientific EffectChemical Vapour Deposition: Chemical Vapour Deposition

Implementation Method 2

flowing, in the cladding deposition burner, a glass raw material gas and a combustion supporting gas in a first region from the inner side, air in a second region from the inner side, a combustible gas in the third region from the inner side

Methodology Applied

Scientific EffectCombustion: Combustion

Implementation Method 3

there is a problem that melt residue occurs when sintering and transparentizing a glass fine particle deposit

Methodology Applied

Scientific EffectSintering: Sintering

Data Source

PatentUS10829405B2Method for producing porous glass deposit for optical fiber

Publication Date: 2020.11.10 SHIN ETSU CHEMICAL CO LTD

AI summary

A method is provided for producing a glass fine particle deposit by a VAD method using a core deposition burner and a cladding deposition burner disposed adjacent to the core deposition burner. The cladding deposition burner including five cylindrical tubes having different outer diameters and concentrically superimposed on one another and a group of small-diameter nozzles arranged in a ring shape in a third region from the inner side. The method includes flowing, in the cladding deposition burner, a glass raw material gas and a combustion supporting gas in a first region from the inner side, air in a second region from the inner side, a combustible gas in the third region from the inner side, a combustion supporting gas in the group of small-diameter nozzles, an inert gas in a fourth region from the inner side, and a combustion supporting gas in a fifth region from the inner side, respectively.