臺灣博碩士論文加值系統

本文的目的在於研究關於 MCVD 製程下的流體流動、熱傳及粒子堆積
等問題。所 模擬的 MCVD 製程係一混合對流效應下所造成複雜的三維
水平圓管流場，其中句括了 可變的流體物理性質、浮力、管子旋轉、
粒子輻射及化學反應等效應。在三維穩態層 流的狀況下、統御方程式
包括了連續方程式、動量方程式、物類方程式以及能量方程 式。本文
以四氯化矽的一階氧化反應來模擬 MCVD 製程中二氧化矽粒子的生成過程
。 藉由計算所得到的流場、溫度場及粒子濃度分佈，可以計算出粒子
的生成效率及堆積 效率，進而了解 MCVD 製程在不同狀況下的效率。
由 SiCl4 氧化過程所釋放出的反應熱，使得反應區內流體溫度急劇的被
提升。 當增加入口的 SiCl4 莫耳分率時，此溫度提升現象越往上游
方向移動，且對不完全 氧化反應而言其粒子生成率也隨著提高。也由
於反應熱對反應區內流體溫度的提升， 減弱了粒子輻射熱傳對提高粒
子生成效率的效應，但在冷卻區段，粒子的溫度受到熱 輻射效應進一
步的冷卻，結果降低粒子堆積效率。

A theoretical study of the MCVD (Modified Chemical Vapor
Deposition) process for the manufacture of optical
fiber preforms is presented. The related flow, heat
and mass transfer, particle formation and deposition are
obtained in cluding the effects of variable properties,
tube rotation, buoyancy, thermal radiation, and chemical
reaction. The governing equations, which include the
continuity, momentum, energy, and species equations, for the
steady-state, three-dimensional, laminar flow are solved
numerically. An one-step oxidation process of SiCl4 is applied
to simulate the chemical reactionand particle (SiO2) formation
in the MCVD process. The efficiencies of particle
formation and deposition are determined from the
resulting velocity, temperature, and species fields. The
energy release from the chemical reaction results in a spike in
gas temperature. This spike only exists in a complete
reaction processand results in a higher particle formation
efficiency and a shorter entrance length. By the effect
of thermal radiation the fluid is cooled down in deposition
zone, such that a more uniform temperature distribution
is obtained. So, effect of aerosol radiation decreases the
deposition efficiency.

COVER
CONTENTS
ABSTRACT
LIST OF TABLES
LIST OF FIGURES
NOMENCLATURE
1 INTRODUCTION
1.1 Motivation
1.2 Optical Fibers and Their Manufacture
1.2.1 Preform Construction
1.2.2 Outside Deposition Processes
1.2.3 Inside Deposition Processes--MCVD Process
1.2.4 Fiber Drawing
1.3 Scoope
2 LITERATURE REVIEWS
2.1 Buoyant flow in straight pipes
2.2 Thermopjoresis
2.3 Articles about the MCVD Process
3 EFFECT OF AEROSOL THERMAL RADIATION ON THE MCVD PROCESS
3.1 Pysical Model and Governing Process
3.2 Theremophysical Properties
3.3 Radiative Properties of aerosol
3.4 Radiation Models
3.5 Numerical Methods
3.5.1 Discretization
3.5.2 Staggered Grid
3.5.3 Differencing Scheme
3.5.4 Pressure Solver
3.5.5 Umderrelaxation
3.5.6 Linear Equation Solver
3.5.7 Convergence Criterion
3.5.8 Numerical Boundary Conditions at the Centerline
3.5.9 Overall Solution Sequence
3.5.10 Numerical Calculation of the Radiative Heat Source Term
3.6 Testing of the Computational Procedure
3.6.1 Thermally Developing Flow in a Straight Pipe without Buoyancy
3.6.2 Thermally Developing Flow in a Straight Pipe With Buoyancy
3.6.3 Three-Dimensional MCVD Process Modelled by Lin et al.(1991)
3.7 Results and Discusison
3.7.1 Effects of the Radiative Heat Transfer
3.7.2 Effects of the Aerosol Concentration
3.7.3 Effects of Tube Rotational Speed
3.7.4 Effects of Inlet axial Mean Velocity
3.7.5 The Reaction Surface Located at T=T rin
4 EFFECT OF SiCl4 OXIDATION OON THE MCVD PROCESS
4.1 Physical Model and Governing Process
4.1.1 Equation of Continuity
4.1.2 Equation of Momentum
4.1.3 Equation of Energy
4.1.4 Thermophorectic Coefficient K
4.1.5 Thermophysical Properties
4.1.6 Radiative Properties of Aerosol
4.1.7 Radiation Model
4.2 Numerical Methods
4.3 Testing Problem
4.4 Results and Discussion
4.4.1 Effect of Xsc,i
4.4.2 Effect of Inlet Flow Rate
4.4.3 Effect of Tube Roatation
4.7.4 Effect of Buoyancy
5 CONCLUSTIONS
5.1 Processes with Uniform Particale Formation Surfaces
5.2 Processes with Oxidation of SiCl4
5.3 Suggestions for Future Work
APPENDIX
REFERENCES
TABLES
FIRURES
OTHERS