臺灣博碩士論文加值系統

高速液體噴流之霧化廣泛運用於燃氣渦輪機、 柴油機、液態火箭推昇引擎及表面塗裝等技術。噴流霧化與液柱表面波不穩定成長有關，該表面波不穩定成長又與噴流初始速度、液體黏滯係數、表面張力、液/氣密度比、液/氣速度差及初始擾動等因素有關。本文以圓柱座標不可壓縮流之連續與動量方程式及小擾動波理論，推導高速液體圓柱噴流表面波之“時間性”不穩定波成長擴散方程式，求取近似解與全解。
有關數值分析部份，主要以不同流速、噴嘴出口管徑，進行不穩定波成長率之數值計算，並同時藉由不同液體性質包括黏度、表面張力、液/氣壓力差及速度差之變化，分析對不同波長的不穩定波成長率的影響，以了解霧化液滴顆粒大小及數量分佈的可能性。由計算結果顯示高速液體噴流霧化之表面波成長率，隨著噴流速度增加而增加，且具有最大成長率的波長相對變小，此與高速噴流霧化產生細小液滴的現象吻合，至於變化不同液體性質的計算結果，也與實驗觀察結果相符。

The high-speed jet atomization is a topic of practical applications, such as gas-turbine combustors, diesel engines, rocket thrust chambers, and spray coatings of protective materials on surface, etc. The liquid jet atomization is related with the unstable waves on the jet surface. The unstable growth rate of the surface wave is affected by initial jet velocity, liquid viscosity, liquid surface tension, liquid/gas density ratio, the difference between liquid and gas velocity, and the initial disturbance on the jet surface. In the present study, a cylindrical liquid jet issued from a nozzle at a constant velocity was considered in the cylindrical coordinate. The dispersion equations governing the temporal growth rates of the jet surface were derived from the continuity equation and the momentum equations with the small perturbation theory. The approximate and general solutions of the temporal dispersion equations were solved numerically.
In the present numerical analyses, the jet parameters, such as liquid velocity, nozzle diameter, liquid viscosity, surface tension, liquid/gas density ratio and the difference between liquid and gas velocity, were varied to study their influences on the unstable wave growth rate. The present models were applied to several low-speed and high-speed jets. The numerical results showed that the trend of variations of the drop sizes and size distributions is in good agreement with the observation of past experimental studies. The present model also predicted that the surface wave growth rate is increased with increasing the jet velocity, and the wavelength of the surface wave with a maximum growth rate becomes shorter. This indicates that the higher the jet velocity the finer droplets are produced in the high-speed atomization process.

摘要
英文摘要
目錄 I
圖目錄 III
表目錄 IV
符號說明 V
第一章 緒論 1
1-1 前言 1
1-2 研究動機 4
1-3 文獻回顧 6
1-4 研究目標 7
第二章 時間性不穩定波之理論分析 9
2-1 時間性擾動波之不穩定分析 9
2-2 時間性不穩定波模式之理論方法 13
2-3 時間性不穩定波模式之數值方法 19
2-3-1 完全擴散方程式之數值方法 20
2-3-2 近似擴散方程式之數值方法 22
第三章 時間性不穩定波之數值結果與討論 25
3-1 時間性不穩定波完全方程式與Levich近似方程式比較 26
3-2 改變流體性質對時間性不穩定波之影響 34
3-3 實際流體之應用 41
第四章結論與建議 46
4-1 結論 46
4-2 建議 48
參考文獻 49

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