臺灣博碩士論文加值系統

聲化學是經由超音波換能器將高功率超音波導入至溶液內，超音波在液體中造成正負壓不斷反覆變化，當聲壓振幅超過空蝕閥值時，使液體中之汽泡核受到壓力的擾動而膨脹及收縮而產生非穩態空蝕氣泡場，這種現象稱為非穩態空蝕。非穩態空蝕汽泡在崩裂時其內部瞬間產生極高溫及高壓的環境，隨即快速冷卻，因此提供了一個獨特的方法及環境，使化學反應能在極致的條件下進行。本研究利用COMSOL有限元素分析軟體，對壓電換能器、聲化學反應槽、水中聲場進行耦合分析，並結合基因演算法以水中平均聲壓為最大值為最佳化目標函數，針對單頻與雙頻聲化學反應槽進行最佳化設計。本研究分別對聲化學反應槽以定性實驗分析，發現本研究線性聲學模型模擬有一定之可靠性。且由定量實驗結果得知，本研究製作的聲化學反應槽其空蝕產量較文獻中已發表的實驗結果大5倍之多。

In a sonochemical reactor, high power ultrasound is introduced into liquid. Once the amplitude of the ultrasound beyond a threshold, nuclei in the liquid become unstable; volumes of the oscillating bubbles fast increase and collapse violently. This phenomenon is called unstable acoustic cavitation. Violent collapses of the cavitation bubbles result in high local pressures and temperatures accompany with extremely rapid cooling, providing a unique environment and means for driving chemical reactions under extreme conditions. In the present study the COMSOL multiphysics analysis software is employed to construct a complete model of the sonochemical bath by coupling the vibrations of piezoelectric ultrasonic transducers and vessel walls with the acoustic field of the liquid. A genetic algorithm is then employed to optimize the geometries of the bath such that a resonant acoustic field and a maximum average sound pressure can be built inside the bath. Two types of sonochemical baths are examined, namely the single-frequency bath and dual-frequency bath. Experimental results show that the distributions of cavitation bubbles qualitatively agree with the simulations. Cavitation yields generated by the single-frequency sonochemical bath is about 5 times greater than those reported in the literature.

摘要 I
SUMMARY II
誌謝 VI
目錄 VII
圖目錄 X
表目錄 XIV
符號說明 XV
第一章 導論 1
1-1 前言 1
1-2 文獻回顧 2
1-3 研究動機與本文架構 7
第二章 超音波空蝕與聲化學 9
2-1 壓電效應 9
2-2 超音波原理 10
2-3 空蝕與聲化學 13
2-4 空蝕產量 15
第三章 超音波換能器之最佳化設計與製作 17
3-1 超音波壓電換能器之構造 17
3-2 基因演算法 19
3-2-1 基因演算法簡介 19
3-2-2 基因演算法流程 19
3-2-3 基因演算法優劣 22
3-3 PZT 壓電片之有限元素分析 24
3-4 超音波壓電換能器之分析與最佳化 30
3-4-1 有限元素模型 30
3-4-2 藍杰文壓電換能器之分析與最佳化 31
3-5 超音波壓電換能器之製作及實驗量測 36
3-5-1 換能器之製作 36
3-5-2 換能器之阻抗與實驗量測 38
第四章 聲化學反應槽之分析與最佳化 43
4-1 聲化學反應槽之有限元素分析 43
4-2 聲固耦合分析 45
4-3 聲化學反應槽之最佳化設計 47
4-4 雙頻聲化學反應槽之疊代設計 52
第五章 聲化學實驗結果與討論 54
5-1 實驗架構 54
5-2 單頻聲化學反應槽之實驗結果與討論 57
5-2-1 空蝕場與聲場模態之定性比較 57
5-2-2 聲化學反應效率之量測結果與討論 62
5-3 雙頻聲化學反應槽之實驗結果與討論 68
第六章 結論與未來展望 70
6-1 結論 70
6-2 未來展望 71
附錄A 平均功率的計算 73
參考文獻 75

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