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Title: | 超音波傅立葉放大器設計與液滴霧化之研究 Numerical Analysis and Experimental Results by Silicon-Based Fourier Ultrasonic Nozzles to Product of Monodisperse Droplets |
Authors: | Chih-Hsiao Cheng 鄭志孝 |
Advisor: | 周元昉 |
Keyword: | 傅利葉放大器,法拉第波, Monodisperse Droplets,ultrasonic atomization, |
Publication Year : | 2012 |
Degree: | 博士 |
Abstract: | 均勻細小的液滴有許多的用途,例如可當作製造奈米級顆粒的先驅物、可製做形成極為細緻表面的塗料;可加大液滴表面,增加蒸發速度甚至燃料速率;可使懸浮藥物直接進入肺部,並由肺泡吸收進入血液等。
本文首先推導在非慣性座標Navier-Stokes方程式,進而導出盛水容器受到垂直振動作用下之法拉第波方程式並計算發生法拉第波所需之激振振幅,及相對應之起始波數。再次分別探討不同流體參數對臨界振幅和相對應波數之關係與上層氣流作用下,如何改變法拉第波的波數。 其次製作傅利葉放大器,先介紹機械放大器(Horn)種類和基本原理,並說明選用傅利葉放大器的原由,其次設計實驗所需傅利葉放大器並利用有限元素法(FEM)模擬並闡述微機電製程(MEMS)並實際製作矽基傅利葉放大器。 最後描述實驗結果,利用阻抗分析儀去驗證矽基傅利葉放大器共振頻率,使用雷射都卜勒振動分析儀(Polytec Laser Doppler Vibrometer)、粒徑分析儀(Malvern Spraytec RT5000)分別去量測其振動的幅度以及霧化後的粒徑分佈。 Monodisperse de-ionized water droplets 4.5 μm~10.1μm in diameter have been produced in ultrasonic atomization using micro electro-mechanical system (MEMS)-based three-Fourier horn 1MHz~300kHz silicon Fourier nozzles. The nozzles measure 1.80 x 0.21 x 0.11 cm3 and can accommodate flow rate of 2 to 300μl/min. As liquid enters the 200 μm x 200 μm central channel of the nozzle, a curved thin liquid film is maintained at the nozzle tip that vibrates longitudinally at the nozzle resonance frequency, resulting in formation of standing capillary waves on the free surface of the liquid film. As the tip vibration amplitude exceeds a threshold (critical or onset amplitude), the standing capillary waves become unstable (temporal instability) and a spray of monodisperse droplets (mist) is produced. In this thesis, thetheoretical predictions of ultrasonic atomization for production of monodisperse water droplets based on the linear theory of capillary wave atomization mechanism and their comparisons to the experimental results obtained using the MHz 3-Fourier horn nozzles are reported. Results of 3-D simulation on mode shape analysis and the resulting resonance frequency using the finite element method (FEM) are also presented which are in good agreement with the experimental data. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/16454 |
Fulltext Rights: | 未授權 |
Appears in Collections: | 機械工程學系 |
Files in This Item:
File | Size | Format | |
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ntu-101-1.pdf Restricted Access | 4.16 MB | Adobe PDF |
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