浸水式超音波聲化學反應器主要由三部份組成，即壓電換能器、變幅桿及反應室。超音波是由壓電換能器產生，經由變幅桿傳遞至反應室的液體中產生空蝕汽泡。一般市售的系統中，空蝕汽泡的發生位置均在變幅桿的端面附近，不僅造成超音波能量的散射與散逸，導致聲化學能量轉換效率不佳，同時使變幅桿的端面產生空蝕侵蝕，減短設備的使用壽命並造成樣本的汙染。為了解決此一問題，本研究以有限元素分析搭配基因演算法，對一40-kHz的浸水式的超音波聲化學反應器進行最佳化設計。分析結果顯示，藉由調整反應室的半徑、液體高度及變幅桿端面到底板的距離，可將系統操作於特定的共振模態。同時我們也以實驗觀察比對不同共振聲場模態下所產生的空蝕汽泡場。本研究最重要的結果是：經由適當的分析設計，可將最大聲壓振幅的位置由變幅桿端面附近移至反應室的內部，使反應器在極低的功率密度下便能產生大區域的空蝕汽泡場。

Immersed-type ultrasonic sonochemical reactors contain three main parts, namely piezoelectric transducer, horn, and reaction cell. Ultrasonic wave is generated by the piezoelectric transducer and transmits to the liquid in the cell through the horn. Cavitation bubbles are then generated by ultrasound. For a general commercialized immersed-type sonochemical system, cavitation bubbles occur very near the horn tip, causing dispersion and dissipation of the ultrasound, poor sonochemical efficiency, severe cavitation erosion of the horn, contamination of the reaction mixture, and degeneration of the system performance. To solve this problem, this study employs a finite element analysis incorporated with a genetic algorithm to optimize a 40-kHz ultrasonic sonochemical reactor. Results show that, by adjusting the radius of the reaction cell, the liquid height and the distance from the horn to the cell bottom, the system can be operated in a specific resonant mode. Several acoustic resonance modes observed in the simulation are realized experimentally and used for generating cavitation fields. The most important finding of this study is that, through proper analysis and design, the location of the maximum ultrasonic pressure can be moved from the vicinity of the horn tip to the interior of the cell and a large field of cavitation bubbles can be generated using a very small ultrasonic power density.

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